430 results on '"Kontoravdi, Cleo"'
Search Results
152. In Situ Monitoring of Intracellular Glucose and Glutamine in CHO Cell Culture
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Behjousiar, Alireza, primary, Kontoravdi, Cleo, additional, and Polizzi, Karen M., additional
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- 2012
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153. The Role of ER Stress-Induced Apoptosis in Neurodegeneration
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C. Stefani, Ioanna, primary, Wright, Daniel, additional, M. Polizzi, Karen, additional, and Kontoravdi, Cleo, additional
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- 2012
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154. Dynamic Optimization of Bioprocesses
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Koumpouras, George, primary and Kontoravdi, Cleo, additional
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- 2012
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155. Application of Global Sensitivity Analysis to Determine Goals for Design of Experiments: An Example Study on Antibody-Producing Cell Cultures
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Kontoravdi, Cleo, primary, Asprey, Steven P., additional, Pistikopoulos, Efstratios N., additional, and Mantalaris, Athanasios, additional
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- 2008
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156. Amino acid and glucose metabolism in fed-batch CHO cell culture affects antibody production and glycosylation.
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Fan, Yuzhou, Jimenez Del Val, Ioscani, Müller, Christian, Wagtberg Sen, Jette, Rasmussen, Søren Kofoed, Kontoravdi, Cleo, Weilguny, Dietmar, and Andersen, Mikael Rørdam
- Abstract
ABSTRACT Fed-batch Chinese hamster ovary (CHO) cell culture is the most commonly used process for IgG production in the biopharmaceutical industry. Amino acid and glucose consumption, cell growth, metabolism, antibody titer, and N-glycosylation patterns are always the major concerns during upstream process optimization, especially media optimization. Gaining knowledge on their interrelations could provide insight for obtaining higher immunoglobulin G (IgG) titer and better controlling glycosylation-related product quality. In this work, different fed-batch processes with two chemically defined proprietary media and feeds were studied using two IgG-producing cell lines. Our results indicate that the balance of glucose and amino acid concentration in the culture is important for cell growth, IgG titer and N-glycosylation. Accordingly, the ideal fate of glucose and amino acids in the culture could be mainly towards energy and recombinant product, respectively. Accumulation of by-products such as NH4
+ and lactate as a consequence of unbalanced nutrient supply to cell activities inhibits cell growth. The levels of Leu and Arg in the culture, which relate to cell growth and IgG productivity, need to be well controlled. Amino acids with the highest consumption rates correlate with the most abundant amino acids present in the produced IgG, and thus require sufficient availability during culture. Case-by-case analysis is necessary for understanding the effect of media and process optimization on glycosylation. We found that in certain cases the presence of Man5 glycan can be linked to limitation of UDP-GlcNAc biosynthesis as a result of insufficient extracellular Gln. However, under different culture conditions, high Man5 levels can also result from low α-1,3-mannosyl-glycoprotein 2-β- N-acetylglucosaminyltransferase (GnTI) and UDP-GlcNAc transporter activities, which may be attributed to high level of [ABSTRACT FROM AUTHOR]- Published
- 2015
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157. Systematic Methodology for the Development of Mathematical Models for Biological Processes.
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Kontoravdi, Cleo
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- 2013
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158. Analysis of the profile of unfolded protein response (UPR) markers in model-systems of Alzheimer's disease
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Stefani, Ioanna, Kontoravdi, Cleo, and Polizzi, Karen
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- 2013
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159. Quality by Design for enabling RNA platform production processes.
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Daniel, Simon, Kis, Zoltán, Kontoravdi, Cleo, and Shah, Nilay
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SARS-CoV-2 , *COVID-19 , *MANUFACTURING processes , *RNA , *PROCESS capability - Abstract
RNA-based products have emerged as one of the most promising and strategic technologies for global vaccination, infectious disease control, and future therapy development. The assessment of critical quality attributes (CQAs), product–process interactions, relevant process analytical technologies, and process modeling capabilities can feed into a robust Quality by Design (QbD) framework for future development, design, and control of manufacturing processes. QbD implementation will help the RNA technology reach its full potential and will be central to the development, pre-qualification, and regulatory approval of rapid response, disease-agnostic RNA platform production processes. Pfizer-BioNTech's (BNT162b2) and Moderna's (mRNA-1713) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are the first RNA-based biologics to be approved for human use and mass produced. RNA technology holds great promise beyond infectious disease prophylaxis, from cancer and gene therapy to treatments against cardiovascular and autoimmune diseases. Current production processes have been developed and scaled up at an unprecedented speed, mostly under a Quality by Testing paradigm. Recent research has highlighted a strong link between product and process development. The application of advanced analytical and modeling technologies could rapidly reshape and digitize manufacturing processes. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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160. A quantitative and mechanistic model for monoclonal antibody glycosylation as a function of nutrient availability during cell culture.
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del Val, Ioscani Jiménez, Constantinou, Antony, Dell, Anne, Haslam, Stuart, Polizzi, Karen M., and Kontoravdi, Cleo
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BIOLOGICAL mathematical modeling ,MONOCLONAL antibodies ,GLYCOSYLATION ,CELL culture ,NUCLEOTIDES - Abstract
The article presents a study which discusses development of quantitative and mechanistic model for monoclonal antibody glycosylation as a function of nutrient availability during cell culture. Topics discussed include role of monoclonal antibodies (mAbs) in drug manufacture, need of quality by design (QbD) principles in process development, and mathematical model consisting of modular elements such as cell culture dynamics and nucleotide sugar (NS) metabolism.
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- 2013
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161. Quantification of intracellular nucleotide sugars and formulation of a mathematical model for prediction of their metabolism.
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del Val, Ioscani Jiménez, Nagy, Judit M., and Kontoravdi, Cleo
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NUCLEOTIDES ,MATHEMATICAL models - Abstract
An abstract of the article "Quantification of intracellular nucleotide sugars and formulation of a mathematical model for prediction of their metabolism," by Judit M. Nagy and colleagues is presented.
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- 2011
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162. Resources, Production Scales and Time Required for Producing RNA Vaccines for the Global Pandemic Demand.
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Kis, Zoltán, Kontoravdi, Cleo, Shattock, Robin, and Shah, Nilay
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RNA ,MESSENGER RNA ,VACCINES ,PANDEMICS ,COVID-19 ,IMMUNIZATION of children - Abstract
To overcome pandemics, such as COVID-19, vaccines are urgently needed at very high volumes. Here we assess the techno-economic feasibility of producing RNA vaccines for the demand associated with a global vaccination campaign. Production process performance is assessed for three messenger RNA (mRNA) and one self-amplifying RNA (saRNA) vaccines, all currently under clinical development, as well as for a hypothetical next-generation saRNA vaccine. The impact of key process design and operation uncertainties on the performance of the production process was assessed. The RNA vaccine drug substance (DS) production rates, volumes and costs are mostly impacted by the RNA amount per vaccine dose and to a lesser extent by the scale and titre in the production process. The resources, production scale and speed required to meet global demand vary substantially in function of the RNA amount per dose. For lower dose saRNA vaccines, global demand can be met using a production process at a scale of below 10 L bioreactor working volume. Consequently, these small-scale processes require a low amount of resources to set up and operate. RNA DS production can be faster than fill-to-finish into multidose vials; hence the latter may constitute a bottleneck. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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163. Multi-omic characterization of antibody-producing CHO cell lines elucidates metabolic reprogramming and nutrient uptake bottlenecks.
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Gopalakrishnan, Saratram, Johnson, William, Valderrama-Gomez, Miguel A., Icten, Elcin, Tat, Jasmine, Lay, Fides, Diep, Jonathan, Gomez, Natalia, Stevens, Jennitte, Schlegel, Fabrice, Rolandi, Pablo, Kontoravdi, Cleo, and Lewis, Nathan E.
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AMINO acid metabolism , *METABOLIC reprogramming , *CELL lines , *BIOCHEMICAL engineering , *MANUFACTURING cells , *CHO cell - Abstract
Characterizing the phenotypic diversity and metabolic capabilities of industrially relevant manufacturing cell lines is critical to bioprocess optimization and cell line development. Metabolic capabilities of production hosts limit nutrient and resource channeling into desired cellular processes and can have a profound impact on productivity. These limitations cannot be directly inferred from measured data such as spent media concentrations or transcriptomics. Here, we present an integrated multi-omic analysis pipeline combining exo-metabolomics, transcriptomics, and genome-scale metabolic network analysis and apply it to three antibody-producing Chinese Hamster Ovary cell lines to identify reprogramming features associated with high-producing clones and metabolic bottlenecks limiting product formation in an industrial bioprocess. Analysis of individual datatypes revealed a decreased nitrogenous byproduct secretion in high-producing clones and the topological changes in peripheral metabolic pathway expression associated with phase shifts. An integrated omics analysis in the context of the genome-scale metabolic model elucidated the differences in central metabolism and identified amino acid utilization bottlenecks limiting cell growth and antibody production that were not evident from exo-metabolomics or transcriptomics alone. Thus, we demonstrate the utility of a multi-omics characterization in providing an in-depth understanding of cellular metabolism, which is critical to efforts in cell engineering and bioprocess optimization. • Multi-omics analysis permits synergistic evaluation of culture performance. • Overall phenotypic changes were traced back to phase-specific metabolic reprogramming. • Reprogramming nitrogen usage and metabolism was associated with increased productivity. • Amino acid usage and channeling towards desired products limited productivity. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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164. Driving towards digital biomanufacturing by CHO genome-scale models.
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Park, Seo-Young, Choi, Dong-Hyuk, Song, Jinsung, Lakshmanan, Meiyappan, Richelle, Anne, Yoon, Seongkyu, Kontoravdi, Cleo, Lewis, Nathan E., and Lee, Dong-Yup
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CHO cell , *DIGITAL twins , *CELL metabolism , *METABOLIC models , *CELLULAR control mechanisms - Abstract
The reliability and methodology of genome-scale metabolic models (GEMs) of Chinese hamster ovary (CHO) cells have advanced. CHO-GEMs have aided in cell line and process development, thus impacting on biomanufacturing efficiency. An integrative model structure can incorporate multiple layers and capture condition-specific cell regulation. Integration of CHO-GEMs with artificial intelligence (AI) and advanced algorithms will enable autonomous bioreactor management for digital biomanufacturing. Genome-scale metabolic models (GEMs) of Chinese hamster ovary (CHO) cells are valuable for gaining mechanistic understanding of mammalian cell metabolism and cultures. We provide a comprehensive overview of past and present developments of CHO-GEMs and in silico methods within the flux balance analysis (FBA) framework, focusing on their practical utility in rational cell line development and bioprocess improvements. There are many opportunities for further augmenting the model coverage and establishing integrative models that account for different cellular processes and data for future applications. With supportive collaborative efforts by the research community, we envisage that CHO-GEMs will be crucial for the increasingly digitized and dynamically controlled bioprocessing pipelines, especially because they can be successfully deployed in conjunction with artificial intelligence (AI) and systems engineering algorithms. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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165. Harnessing the potential of artificial neural networks for predicting protein glycosylation
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Kotidis, Pavlos and Kontoravdi, Cleo
- Abstract
Kinetic models offer incomparable insight on cellular mechanisms controlling protein glycosylation. However, their ability to reproduce site-specific glycoform distributions depends on accurate estimation of a large number of protein-specific kinetic parameters and prior knowledge of enzyme and transport protein levels in the Golgi membrane. Herein we propose an artificial neural network (ANN) for protein glycosylation and apply this to four recombinant glycoproteins produced in Chinese hamster ovary (CHO) cells, two monoclonal antibodies and two fusion proteins. We demonstrate that the ANN model accurately predicts site-specific glycoform distributions of up to eighteen glycan species with an average absolute error of 1.1%, correctly reproducing the effect of metabolic perturbations as part of a hybrid, kinetic/ANN, glycosylation model (HyGlycoM), as well as the impact of manganese supplementation and glycosyltransferase knock out experiments as a stand-alone machine learning algorithm. These results showcase the potential of machine learning and hybrid approaches for rapidly developing performance-driven models of protein glycosylation.
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- 2020
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166. Computer-aided design space identification for screening of protein A affinity chromatography resins.
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Sachio, Steven, Likozar, Blaž, Kontoravdi, Cleo, and Papathanasiou, Maria M.
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AFFINITY chromatography , *COMPUTER-aided design , *PROTEOMICS , *PHARMACEUTICAL biotechnology industry , *MACHINE learning - Abstract
• Model-based frameworks for accelerated process development. • Computer-aided resin screening. • Machine learning enhanced dataset generation. • Consideration of process flexibility in resin evaluation. The rapidly growing market of monoclonal antibodies (mAbs) within the biopharmaceutical industry has incentivised numerous works on the design of more efficient production processes. Protein A affinity chromatography is regarded as one of the best processes for the capture of mAbs. Although the screening of Protein A resins has been previously examined, process flexibility has not been considered to date. Examining performance alongside flexibility is crucial for the design of processes that can handle disturbances arising from the feed stream. In this work, we present a model-based approach for the identification of design spaces, enhanced by machine learning. We demonstrate its capabilities on the design of a Protein A chromatography unit, screening five industrially relevant resins. The computational results favourably compare to experimental data and a resin performance comparison is presented. An improvement on the computational time by a factor of 300,000 is achieved using the machine learning aided methodology. This allowed for the identification of 5,120 different design spaces in only 19 h. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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167. COSMIC-dFBA: A novel multi-scale hybrid framework for bioprocess modeling.
- Author
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Gopalakrishnan, Saratram, Johnson, William, Valderrama-Gomez, Miguel A., Icten, Elcin, Tat, Jasmine, Ingram, Michael, Fung Shek, Coral, Chan, Pik K., Schlegel, Fabrice, Rolandi, Pablo, Kontoravdi, Cleo, and Lewis, Nathan E.
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ANTIBODY titer , *MULTISCALE modeling , *METABOLIC models , *PREDICTION models , *CELL metabolism , *GROWTH , *MACHINE learning - Abstract
Metabolism governs cell performance in biomanufacturing, as it fuels growth and productivity. However, even in well-controlled culture systems, metabolism is dynamic, with shifting objectives and resources, thus limiting the predictive capability of mechanistic models for process design and optimization. Here, we present Cellular Objectives and State Modulation In bioreaCtors (COSMIC)-dFBA, a hybrid multi-scale modeling paradigm that accurately predicts cell density, antibody titer, and bioreactor metabolite concentration profiles. Using machine-learning, COSMIC-dFBA decomposes the instantaneous metabolite uptake and secretion rates in a bioreactor into weighted contributions from each cell state (growth or antibody-producing state) and integrates these with a genome-scale metabolic model. A major strength of COSMIC-dFBA is that it can be parameterized with only metabolite concentrations from spent media, although constraining the metabolic model with other omics data can further improve its capabilities. Using COSMIC-dFBA, we can predict the final cell density and antibody titer to within 10% of the measured data, and compared to a standard dFBA model, we found the framework showed a 90% and 72% improvement in cell density and antibody titer prediction, respectively. Thus, we demonstrate our hybrid modeling framework effectively captures cellular metabolism and expands the applicability of dFBA to model the dynamic conditions in a bioreactor. • Hybrid framework improves bioprocess model predictive capabilities. • ML-modulated stoichiometric model predicts accurate instantaneous fluxes. • Prediction accuracy of cell state shifts and resource distribution affects concentration profiles. [ABSTRACT FROM AUTHOR]
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- 2024
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168. CHO cell cultures in shake flasks and bioreactors present different host cell protein profiles in the supernatant.
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Goey, Cher H., Bell, David, and Kontoravdi, Cleo
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CHO cell , *CELL culture , *BIOREACTORS , *LOW temperatures , *STATISTICAL correlation - Abstract
Highlights • Comparison of flask and bioreactor cultures at 37 °C and 32 °C. • All four conditions produced similar HCP concentration and mAb/HCP ratio. • Bioreactor cultures had significantly higher number of HCP species than flasks. • HCP variety correlated with apoptotic cell density in bioreactors but not flasks. Abstract Several studies on the impact of cell culture parameters on the profile of host cell protein (HCP) impurities have been carried out in shake flasks. Herein, we explore how transferable the findings and conclusions of such investigations are to lab-scale bioreactors. Experiments were performed in both systems in fed-batch mode under physiological temperature and with a shift to mild hypothermia and the impact on key upstream performance indicators was quantified. Under both temperatures, bioreactors produced a richer HCP pool despite the overall concentration being similar at both scales and temperatures. The number of different HCPs detected in bioreactor supernatants was four times higher than that in flasks under physiological temperature and more than eight times higher under mild hypothermia. The origin of HCPs was also altered from mostly naturally secreted proteins in flasks to mainly intracellular proteins in bioreactors at the lower temperature. Although the number of species correlated with apoptotic cell density in bioreactors, this was not the case in flasks. Even though the level of HCP impurities and mAb/HCP concentration ratio were similar under all four conditions with an average of approximately 330 μg HCP/mL culture and 0.3 mg HCP/mg IgG4, respectively, the fact that culture method significantly affects the number of species present in the supernatant can have implications for downstream processing steps. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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169. Mathematical modelling for bioprocess understanding and optimisation
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Alhuthali, Sakhr and Kontoravdi, Cleo
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615.3 - Abstract
Recombinant proteins have been extensively studied for their wide therapeutic and research applications. The main therapeutic product category is that of monoclonal antibodies (mAbs), which have been widely approved to treat a variety of chronic and life-threatening diseases. Increasing mAb titre has been achieved mainly by cell culture medium improvement and genetic engineering to increase cell density and productivity. However, this improvement has caused many technical issues in both upstream (USP) and downstream (DSP) processes. The higher accumulation of the main cell-derived impurities, host cell proteins (HCPs), in the supernatant has proved to negatively affect product integrity and immunogenicity in addition to increasing the subsequent cost of capture and polishing steps. It has severely affected the performance of antibody drug candidates in at least two cases in which clinical trials have been put on hold as a result of HCP-related problems. Certain HCPs are naturally secreted, while others are inevitably released because of cell death and lysis. Exploring the relationship between critical process parameters (CPPs) and critical quality attributes (CQAs) in the context of HCP dynamics at a minimum cost is a highly important factor from an industrial point of view. Mathematical modelling of bioprocess dynamics is a valuable tool to improve industrial production at fast rate and low cost. A single stage volume-based population balance model (PBM) has been built to capture Chinese hamster ovary (CHO) cell behaviour in fed-batch bioreactors. The model includes two operating modes; the first at physiological temperature and the second, which represents a common industrial practice, with a shift to mild hypothermic conditions (32 °C) in mid-exponential growth phase. The model considers the dynamic profile of substrates and metabolites, product titre and HCPs. Culture osmolality is also considered as a determining factor for cell growth rate and cell volume increase. The model was then used to optimise titre by controlling CPPs such as feed volume and frequency, the time point of temperature downshift as well as the harvesting time. The optimisation is subject to constraints such as maintaining culture viability above 80% and no feeding in the first 48 hours interval in all model optimisation runs. Four specific optimisation scenarios have been explored based on optimising titre and the titre/HCP ratio. This has been done on both operating modes; physiological temperature and initial physiological temperature with the possibility of temperature downshift after the second culture day. Total nutrients volume can be efficiently minimised by changing feeding volume and time point to satisfy the cellular metabolic need. This approach yields higher purity and more economical operating conditions. In general, higher product titres, up to 30%, and prolonged culture viability can be attained at the expense of higher feeding pulses. However, when a constraint on HCP concentration is also applied model-based optimisation results in shorter culture duration and, in turn, overall lower antibody titre. This thesis shows the usefulness of mathematical modelling for exploring trade-offs in bioprocess performance. Integrating this model with a downstream purification model to evaluate the cost of removing these fractions of impurities, can help determine what concentration of HCPs can be economically tolerated in the cell culture supernatant and aid whole bioprocess design.
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- 2020
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170. An integrated modelling/experimental framework for protein-producing cell cultures
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Kontoravdi, Cleo
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- 660.2844
- Published
- 2007
171. Modelling of amorphous cellulose depolymerisation by cellulases, parametric studies and optimisation.
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Niu, Hongxing, Shah, Nilay, and Kontoravdi, Cleo
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CELLULOSE , *DEPOLYMERIZATION , *MATHEMATICAL optimization , *SENSITIVITY analysis , *HYDROLYSIS - Abstract
Improved understanding of heterogeneous cellulose hydrolysis by cellulases is the basis for optimising enzymatic catalysis-based cellulosic biorefineries. A detailed mechanistic model is developed to describe the dynamic adsorption/desorption and synergistic chain-end scissions of cellulases (endoglucanase, exoglucanase, and β-glucosidase) upon amorphous cellulose. The model can predict evolutions of the chain lengths of insoluble cellulose polymers and production of soluble sugars during hydrolysis. Simultaneously, a modelling framework for uncertainty analysis is built based on a quasi-Monte-Carlo method and global sensitivity analysis, which can systematically identify key parameters, help refine the model and improve its identifiability. The model, initially comprising 27 parameters, is found to be over-parameterized with structural and practical identification problems under usual operating conditions (low enzyme loadings). The parameter estimation problem is therefore mathematically ill posed. The framework allows us, on the one hand, to identify a subset of 13 crucial parameters, of which more accurate confidence intervals are estimated using a given experimental dataset, and, on the other hand, to overcome the identification problems. The model’s predictive capability is checked against an independent set of experimental data. Finally, the optimal composition of cellulases cocktail is obtained by model-based optimisation both for enzymatic hydrolysis and for the process of simultaneous saccharification and fermentation. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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172. A multiscale modelling framework for the processes involved in consolidated bioprocessing
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Mc Caul, Kristian, Shah, Nilay, Kontoravdi, Cleo, and Xu, Yun
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660 - Abstract
Cellulosic biomass is one of the most abundant materials on earth, making it an attractive prospect for bioprocessing to produce fuels and chemicals as an alternative to fossil fuels. Traditional processes that convert cellulose to products do so via an inefficient multistep process, involving sequential reactors that first hydrolyse the cellulose through the addition of exogenous enzymes and then pass the hydrolysate to the next reactor for the liberated sugars to be fermented. Consolidated bioprocessing (CBP) combines this two-step process into one, offering improvements in costing, by removing the need for extra reactors, and efficiency, by having organisms utilise sugars as they are produced reducing end product inhibition of the cellulases. This thesis is aims to model the CBP process by developing separate hydrolysis and fermentation models and then integrating them together. Then by using the model the optimal conditions for ethanol production will be found and the limiting steps of the process identified. A model depicting the breakdown of cellulose by cellulases and a dynamic metabolic flux analysis (DMFA) model describing the fermentation of glucose and cellobiose by the thermophilic organism G. thermoglucosidasius was developed. These models were fitted to experimental data of the cells growing on cellobiose and literature data of cellulose hydrolysis. The effects of the timing of the anaerobic switch, adding either glucose or cellobiose to the system and enzyme composition were analysed. It was found that by adding 5 mmol/L of cellobiose at the start of the reaction, the ethanol production increased by 35% (mol/mol). The timing of the switch from aerobic to anaerobic conditions was found to be an important factor. The later the switch occurred, the less ethanol was produced. The longer the cells lived in aerobic conditions the more of the glucose and cellobiose was used for cell growth, leaving less for ethanol production once the switch was made. The ratio of endo/exoglucanses to β-glucosidase affected the rate at which cellulose was broken down. This effect then passed on to the cell growth curves and ethanol production. A ratio of 0.95 exo/endoglucanases to 0.05 β-glucosidases was found to produce the most ethanol. A combination of 1-hour anaerobic switch time, 0.95/0.05 enzyme split and 5 mmol/L initial cellobiose were found to be optimal, producing 115 mmol/L of ethanol. Global sensitivity analysis (GSA) was carried out on each of the models, with the key parameters affecting the outputs identified. There was a lack of detailed CBP for these cells growing on cellulose to assess the accuracy and validate the model. Therefore, there are areas of the model that require further investigation, in particular how the model predicts cell growth. Despite this the model does show that the ability to test changes to the process through simulations can be very powerful. Modelling the CBP process opens areas for more research in the future, such as online optimisation and control. Accurate control of co-cultures of microorganisms will be key in the future to produce exact levels of enzyme production and cell growth that maximise the production of products.
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- 2018
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173. Cascading effects in bioprocessing : the impact of cell culture environment on CHO cell behaviour and host cell protein species
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Goey, Cher Hui and Kontoravdi, Cleo
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615.1 - Abstract
One of the reasons for the rejection of new drugs during clinical trials is the presence of host cell proteins (HCPs) in the drug formulation. HCPs are immunogenic impurities that can compromise patient safety. Moreover, proteolytic and binding HCPs compromise the integrity, and, hence, the stability and efficacy of a recombinant protein. Therefore, HCPs should be removed from the bioprocess train as soon as possible. Current downstream purification platforms are challenged by HCP-mAb co-elution. A Quality by Design strategy to overcome this problem is to reduce the number of HCPs in the downstream feedstock by tracing their source back to upstream culture and eliminating it. Previous studies have shown that upstream cell culture parameters, e.g. harvest time and culture temperature, significantly affect HCP profiles. However, little is known about how host cells coordinate and regulate their molecular machinery under different cell culture environment that results in different HCP profiles. This study presents experimental results linking cell culture temperature and key process indicators of CHO cell cultures and post-Protein A purification (mAb titre, HCP level and HCP species) by considering the cellular behaviour in terms of cell growth, cell cycle distribution and cell health). This study involved the application of single-use fed-batch bioreactors to culture IgG4 producing GS-CHO cell line, cell health and cell cycle analysis with NucleoCounter, Protein A purification and proteomic analysis with HCP ELISA kits and LC-MS/MS. Cells were more robust under mild hypothermia: over 90% of cells were maintained in a healthy state until the decline phase, and the onset of apoptosis was less evident compared to the results for physiological temperature. IgG4 titre and HCP level at harvest were comparable between the two cases. However, mild hypothermia reduced the HCP variety in HCCF by 36%, including 44% and 27% lower proteases and chaperones, respectively. The differences in HCP variety at harvest resulted in a significantly different HCP profile post-Protein A purification between the two cases. Half of the critically immunogenic HCPs species as determined by the CHOPPI tool were different between the two cases. This study shows that cell culture conditions significantly affect the HCP profile at harvest and that of purified samples.
- Published
- 2017
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174. Towards the cell-free expression of glycoproteins
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Exley, Kealan Peter, Polizzi, Karen, and Kontoravdi, Cleo
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570 - Abstract
N-linked glycosylation, is the covalent linkage of an oligosaccharide to an amido-group of an asparagine in a consensus sequence motif. The biosynthesis and transfer of a carbohydrate chain onto a nascent protein occurs within the ER and these initial steps are highly conserved throughout eukaryotes. Further processing of the carbohydrate chain occurs in the Golgi apparatus, where differences in processing between species and cell-types arise, resulting in different saccharide composition of the end-product. These differences are important in nature as N-linked glycosylation can influence a protein's function and interaction. However, this trait can be problematic when manufacturing a biopharmaceutical, due to the potential pharmacokinetic influence of the glycan structure. Consequently, it is important to ensure a suitable N-linked glycan is produced. The removal of the N-linked glycosylation processing from the constraints of a cell will allow for greater control of the end saccharide composition of the glycan chain. A cell-free protein expression system will reduce heterogeneity allowing for the production of a homogenesis glycan chain. With this in mind, a project was conceived to create a cell free protein synthesis system for the expression of glycoproteins. The project commenced with implementation of a glycoengineering approach on P. pastoris to generate pentamannosyl oligosaccharide. This oligosaccharide is seen as substrate for the synthesis of a complex-type glycoprofile. To process the pentamannosyl oligosaccharide the expression of a glycosidase and two glycotransferases was attempted. The feasibility of producing a cell-free protein synthesis (CFPS) system from yeast cell lysate was also tested. This project resulted in a knockout P. pastoris strain which prevented the hypermannosylation glycoprofile. This strain can viably be used to generate the pentamannosyl oligosaccharide. A recombinant human GlcNAcT-I was produced which demonstrated the in vitro modification of an oligosaccharide chain. Finally, the project developed an active CFPS with a S. cerevisiae cell lysate but not with P. pastoris, suggesting that not all cell lysates can be utilised to generate an active CFPS. Together, these results highlight the difficulties in utilising a non-conventional yeast for genetic and metabolic engineering. This research has suggested targets for future work which could yet see the generation the first cell free glycoprotein synthesis with a complex-type glycoprofile.
- Published
- 2017
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175. Comparative assessment of simulation-based and surrogate-based approaches to flowsheet optimization using dimensionality reduction.
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Triantafyllou, Niki, Lyons, Ben, Bernardi, Andrea, Chachuat, Benoit, Kontoravdi, Cleo, and Papathanasiou, Maria M.
- Subjects
- *
SURROGATE-based optimization , *CHEMICAL processes , *SENSITIVITY analysis , *GLOBAL optimization , *OPERATING costs - Abstract
• Bayesian optimization for sequential-modular flowsheet optimization. • Global sensitivity analysis as a dimensionality reduction technique. • Simulation-based and surrogate-based Bayesian optimization. • Two industrially relevant case studies for plasmid DNA and dimethyl ether production. This work proposes a framework for simulation-based and surrogate-based reduced space Bayesian optimization of process flowsheets. The framework uses global sensitivity analysis for dimensionality reduction via the identification of critical process variables that contribute significantly to the variability of the objective function (e.g. productivity and operating costs). Both simulation- and surrogate-based algorithms are applied to a biopharmaceutical and a chemical process simulator for the production of plasmid DNA and dimethyl ether (DME), respectively. Their capabilities are assessed in terms of the trade-off between computational effectiveness and solution accuracy. Results indicate that simulation-based Bayesian optimization achieves better objective function values, while surrogate-based Bayesian optimization is more computationally effective. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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176. Understanding the impact of bioprocess conditions on monoclonal antibody glycosylation in mammalian cell cultures through experimental and computational analyses
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Sou, Si Nga, Kontoravdi, Cleo, and Polizzi, Karen M.
- Subjects
660 - Abstract
With positive outcomes from medical treatments, monoclonal antibodies (mAbs) are to date the best-selling biologics in the pharmaceutical market. The fact that a lot of blockbuster drugs are facing the period of patent cliffs and patents of many of them are due to expire in the next 5 years, places an urgency for better, cheaper and more efficient bioproduction processes, as well as the development of novel drugs and biosimilars. To address to this issue, application of the Quality by Design paradigm that was introduced by the Food and Drug Administration (FDA) is of paramount importance. Medical values and safety of monoclonal antibodies have been reported to rely on the carbohydrate structures that are attached to the mAb N-linked glycosylation site on each constant region. Fc-N-linked glycosylation is considered as a critical quality attribute (CQA) of these therapeutic proteins under the scope of Quality by Design. It was also reported that different bioprocess conditions during recombinant mAb production directly impact glycan compositions and their distribution on the molecules, although the mechanism behind this change is not fully understood. This lack of understanding limits process design and optimisation. To address this issue we examined the effect of mild hypothermia (32oC) and the different recombinant expression systems on mAb N-linked glycosylation, using experiments, flux balance analysis (FBA) and mechanistic modelling to identify resulting differences in cell metabolism. A defined mathematical model that mechanistically and quantitatively describes CHO cell behaviour and metabolism, mAb synthesis and its N-linked glycosylation profiles before and after the induction of mild hypothermia in SGE and TGE expression systems was also constructed, which we believe is the first quantitative model that relates mild hypothermia and TGE system to the four elements mentioned above. Not only does the model aid understanding of the way bioprocess conditions affect product quality, it also provides a platform for bioprocess design, control and optimisation in industry and helps the implementation of the Quality by Design principles. Results obtained from our computational studies suggested glycosyltransferases to be the key players for changes observed among different bioprocess conditions, based on results obtained from this thesis we then manipulated the expression of galactosyltransferase in particular, through a proof-of-concept experiment using miRNAs.
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- 2016
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177. Unravelling the progression of unfolded protein Rresponse in a model system of familial Alzheimer's disease
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Stefani Chrysoula, Ioanna, Kontoravdi, Cleo, and Polizzi, Karen
- Subjects
616.8 - Abstract
Alzheimer's disease (AD) is the most common form of dementia disorders and, yet, there is no preventative or curative treatment. It is associated with the progressive loss of memory and cognition and clinically divided into sporadic and familial forms. Familial Alzheimer's disease (FAD) has predominantly a genetic predisposition with inherited mutations in the amyloid-β precursor protein (APP) and presinilin genes, which promote APP processing through the amyloidogenic pathway. This results in the release of the Aβ peptide, a major neurotoxic agent in AD progression. Accumulation of unfolded and misfolded disease-specific proteins (including Aβ and tau proteins) in neuronal cells perturbs endoplasmic reticulum (ER) homeostasis, leading to the onset of a cellular stress cascade called unfolded protein response (UPR), markers of which are upregulated in AD brain specimens. This suggests a possible role for ER stress in activation and the pathogenesis of AD. The research aimed to investigate the dynamic response of the UPR in an experimental model system of the disease combined with a computational model. For this purpose human neuroblastoma cell lines overexpressing the wild-type (APPWT) and two mutant forms of APP (APPMUT) associated with FAD were generated. Gene expression analysis of UPR markers revealed that overexpression of APP induces preconditioning of ER stress in all cell lines but with a stronger response in FAD-associated mutants. The progression sequence of UPR in APPWT and APPMUT was investigated in a time-course manner following the application of chemical stress. The results revealed that APPMUT exhibited the highest global response to chemically induced stress with a similar pattern. A computational model of the mammalian UPR was then generated and used to understand the dynamics of UPR. The model was able to reproduce our experimental data, which included pre-existing genetic factors (mutations in APP-associated with FAD) and a mimic of environmental triggers (induction of stress) consequently triggering the stress response. It suggested a different protein load and magnitude of transcriptional activation upon stress among the three cell lines. This was followed by in silico case studies exploring the effect of drugs targeting different branches of the UPR. This study proposes a novel multidisciplinary platform that could be further used for the development of therapeutics for AD. As the familial and sporadic form of the disease have similar neuropathological characteristics, drugs efficacious for FAD will also be beneficial for the most common form of AD.
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- 2015
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178. A platform for the optimisation of metabolic pathways for glycosylation to achieve a narrow and targeted glycoform distribution
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Jedrzejewski, Philip, Kontoravdi, Cleo, and Polizzi, Karen M.
- Subjects
572 - Abstract
Glycoproteins make up the bulk of biologically-derived medicines, and are taking up an ever increasing share of the prescription pharmaceuticals market. As opposed to small molecule drugs, glycoproteins are large complex molecules with heterogeneity arising from a multitude of glycan moieties. Glycans are complex post-translation modifications, which result from a number of enzymatic reactions in the ER and Golgi collectively known as glycosylation and play an important role in pharmacokinetics such as drug safety, efficacy and half-life. It is known that the availability of the nucleotide sugar donors (NSDs), which are the co-substrates to the enzymatic glycosylation reactions of the Golgi, can be affected by a number of process conditions such as nutrient availability, as well as the addition of precursor molecules to the culture medium. Consequently, feeding strategies of nucleotide and nucleotide sugar precursors have been explored to exert control over the glycoform. In this work, a mathematical model platform is presented to quantify the impact of nutrient availability and feeding strategies on the glycosylation process with the aim to enable the design of feeding strategies to optimise the product glycoform. A modelling platform was developed and trained to link the extracellular environment, through the availability of intracellular metabolites in the cytoplasm and the Golgi apparatus, to the glycosylation of the conserved glycan site of the IgG heavy chain. The model platform comprises four parts, which are interlinked through dynamic fluxes and metabolite concentrations: A modified cell growth model based on Monod kinetics capturing cell culture dynamics and the impact of various hexose and nucleotide precursor additions to the cell culture media; A semi-structured purine and pyrimidine synthesis network describing the intracellular concentrations of nucleotide triphosphates, which are the co-substrates of NSD synthesis; A structured and mechanistic representation of the NSD synthesis pathway; The del Val et al. model describing the N-linked glycosylation process of the conserved glycan structure of the IgG antibody heavy chain. An initial proof-of-concept model framework was able to reproduce hybridoma batch cell growth dynamics, extracellular nutrient availability, dynamic intracellular NSD and nucleotide concentrations, product titer and the antibody product glycoform. Refinement of the original model framework and further training was achieved through a two-step CHO cell-based experimental process. In a first set of experiments the cells’ dynamic response to mannose and guanosine feeding was observed. The data allowed a model extension to fed-batch operation as well as inclusion of additional control and inhibitory mechanisms in the in silico representation of the nucleotide and NSD de novo synthesis networks. A second set of experiments probed the dynamic impact of galactose and uridine feeding strategies on antibody product galactosylation. The effects were dynamic perturbations with respect to cell culture dynamics, nucleotide and NSD synthesis as well as the antibody product glycoform. This formed as a basis for further model refinement and to provided a calibrated operating space with respect to galactose and uridine additions to cell culture media. The calibrated model platform was able to produce an optimal dynamic feeding strategy in silico with a predicted increase in galactosylation of 46.9% through pulse feeding of galactose and uridine on even days of culture. This framework is a first step towards a platform for the in silico optimisation of bioprocess conditions with respect to product quality and safety in line with the Quality by Design (QbD) paradigm.
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- 2015
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179. Hitting the sweet spot with capillary electrophoresis: advances in N-glycomics and glycoproteomics.
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Makrydaki, Elli, Kotidis, Pavlos, Polizzi, Karen M, and Kontoravdi, Cleo
- Subjects
- *
CAPILLARY electrophoresis , *GLYCANS , *BIOPHARMACEUTICS , *GLYCOMICS - Abstract
CE–MS glycoproteomics and glycomics. In intact methods, the glycans are identified while attached to the entire protein backbone, exposing the glycosylation profile and providing information on the macro-heterogeneity and site occupancy. In middle-up and bottom-up analysis, the protein is digested into sububits or smaller peptide fragments, revealing specific glycoforms and elucidating micro-heterogeneity in a site-specific approach. In released glycans techniques, the glycans are completely released from the protein molecule through chemical or enzymatic means. Unlike the middle-up and bottom-up techniques, released glycans do not offer site-specific information, but can achieve excellent levels of sensitivity in glycan microheterogeneity identification. [Display omitted] N -glycosylation is of paramount importance for understanding the mechanisms of various human diseases and ensuring the safety and efficacy of biotherapeutics. Traditional glycan analysis techniques include LC-based separations and MALDI-TOF-MS identification. However, the current state-of-the-art methods lack throughput and structural information, include laborious sample preparation procedures and require large sample volumes. Capillary electrophoresis (CE) has long been used for the screening and reliable quantitation of glycans, but its applications have been limited. Because of its speed, sensitivity and complementarity with standard glycan analysis techniques, CE is currently emerging as one of the most versatile and adaptable methods for glycan analysis in both academia and industry. Herein, we review the latest advancements in CE-based applications to glycomics and glycoproteomics within both the biopharmaceutical and clinical sectors. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
180. Amino acid metabolism in Chinese hamster ovary cell culture
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Kyriakopoulos, Sarantos and Kontoravdi, Cleo
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660 - Abstract
The present thesis focuses on amino acids (a.a.) and their metabolism by Chinese hamster ovary cells, the workhorse of the multibillion dollar biopharmaceutical industry. The aim of the research was to explore a.a. transport and metabolism and define optimal operating conditions during fed-batch culture, which is the most common process mode used industrially. A fast and reliable way to calculate a.a. concentration ranges in media and feeds is of vital importance, as a.a. are the monomers of proteins, which account for 70% of dry cell weight. The desired recombinant product of bioprocesses is typically also a protein. The transport of a.a. into the cells was studied at the mRNA level of a.a. transporters for the first time in a bioprocessing context. The presented results demonstrate that a.a. transport is not the limiting step for recombinant protein formation. Also, the study allowed for a staged feeding strategy to be designed, where a.a. were not fed altogether. Following linear projection of an integral of viable cell concentration target and using the specific a.a. consumption rates during batch culture, six feeds were formulated containing a.a. and glucose. Three designs were based on the results of the a.a. transport study; however, they underperformed in comparison to the other feeds. In the latter, all nutrients were fed at the same time, resulting in cell culture performance comparable to that obtained with a commercial feed that was tested in parallel. This renders the presented method the first to define a traceable quantitative way to calculate amount of nutrients in the feeds. Flux balance analysis, a powerful technique that allows for investigation of intracellular dynamics, was used to analyse the metabolic data. An enhanced intracellular network was created by coupling two pre-existing in the literature that also for the first time included the glycosylation of the host proteins in the biomass equation. Finally, a novel methodology was developed and coded in R to calculate specific rates of consumption/production of various metabolites in cell culture. The methodology couples mass balances for fed-batch culture operation with constructed vectors of the sampling and feeding schemes. This can be further developed to a bioprocess relevant software platform for analysing cell culture data.
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- 2014
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181. Modelling as a tool for increasing the specific productivity of single-chain antibody fragments from Pichia pastoris
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Royle, Kate, Leak, David, Kontoravdi, Cleo, and Bundy, Jake
- Subjects
570 - Abstract
Pichia pastoris is a commonly used recombinant protein expression host, predominantly due to ease of genetic manipulation and its capacity for high cell densities in cheap culture media. While considerable yields can be achieved in this way, the specific productivity is relatively low. Consequently, the full impact of this host on industrial biotechnology has not yet been realised. This research aimed to develop a strategy to optimise production of single chain antibody fragments (scFvs), an industrially relevant protein, using an integrated modelling and experimental approach. Initially, a dynamic model was constructed from literature sources to reproduce the scFv production pathway in P. pastoris. It incorporated aspects of transcription, translation, folding and misfolding in the endoplasmic reticulum (ER). Moreover, the unfolded protein response (UPR) and ER-associated degradation (ERAD) were added as these two stress pathways are crucial to productivity. Simulations qualitatively reproduced phenomena including secretion saturation and the negative influence of high gene copy numbers on yield. The model was used to target evaluation of the experimental system: P. pastoris strains expressing the scFvs BC1 and MFE23. RT Q-PCR and LC-MS/MS results revealed some surprising correlations between certain factors, such as the concentration of Kar2 and PDI, and yield. Moreover, it showed that there was more than one route to high productivity. Finally, it suggested that there may be an internal regulation of Kar2 that would be crucial to strategies aiming to increase yield through overexpression of that chaperone. Together, the results revealed a more complex picture of productivity than previously understood. In order to develop a strategy for optimal scFv production in P. pastoris, a greater understanding of the underlying biology and biochemistry is required. This research has suggested targets for future work which should generate insight into the network of factors responsible.
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- 2014
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182. In situ FRET biosensors for the in vivo measurement of important metabolites during cell culture
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Behjousiar, Alireza, Kontoravdi, Cleo, and Polizzi, Karen
- Subjects
660 - Abstract
It has long been a goal of the bioprocessing field to be able to produce proteins in a cost-effective and efficient manner. The current method of choosing high-producing mammalian cells is labour-intensive and time-consuming, representing an opportunity to employ new analytical methodologies in an effort to expedite progress. It would be advantageous to measure the intracellular concentration of key metabolites as the cells are growing. This would allow the user to have more information regarding the wellbeing and growth potential of cells. In this thesis the construction, optimisation and use of FRET biosensors for the in vivo measurement of glucose and glutamine in Chinese Hamster Ovary cells will be discussed. Experiments have been conducted in batch and fed-batch cultures as well as small-scale investigations using the BioLector™. The work presented here suggests the use of genetically encoded FRET biosensors allows for quantification of intracellular metabolite concentrations via FRET ratios during cell growth. These FRET biosensors also show that it may be possible to predict intracellular metabolite concentrations based solely on the FRET ratio of these cells. It has also been suggested that in a smaller volume micro fermentation system (BioLector™) these biosensor transfected cell lines can be used to detect changes in intracellular metabolite levels. These biosensor cell lines were then used for cell line selection, results indicate that the FRET ratio may also be used as a tool to discard various cell lines based on time of progression. Using data in the final study, it may be concluded that the early progressed cell lines may not necessarily be the highest protein producers and with, respect to scFv production, no product specific differences exist. The results indicate the usefulness of these FRET biosensors as tools in aiding the process of information gathering at an early stage during cell line selection.
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- 2014
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183. Assessment of the interactions between bioprocess conditions and protein glycosylation in antibody-producing mammalian cell cultures
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Jimenez Del Val, Ioscani, Kontoravdi, Cleo, and Nagy, Judit
- Subjects
660 - Abstract
The pharmaceutical industry is going through a rather turbulent period. Many blockbuster drugs have fallen off patent over the past two years and many more are expected to do so in the near future. In response, pharmaceutical companies have continued searching for products that will replace those that have lost patent protection. However, drug development and approval is extremely time-consuming and costly. So that this critical issue is addressed, industry experts and regulatory agencies have jointly proposed the implementation of Quality by Design (QbD) principles in the development and manufacture of all new drugs. Adoption of QbD is expected to reduce drug development cost and approval time. It is also expected to encourage innovation by developing drugs, and the processes used to manufacture them, around the mechanisms that relate process inputs with end product quality. Within this context, monoclonal antibodies (mAbs) are currently the highest-selling products of the biopharmaceutical industry and are projected to account for nearly half of the world’s top-selling drugs by 2018. All currently commercialized mAbs contain N-linked glycans (complex carbohydrates) bound to their protein backbone. These carbohydrates, in turn, have been widely reported to impact the safety and efficacy of mAbs. Furthermore, it has widely been reported that bioprocess conditions heavily impact the composition and distribution of these glycans. For these reasons, mAb glycosylation is considered a critical quality attribute (CQA) of these therapeutic proteins under the QbD scope. Based on QbD principles, the objective of this thesis was to generate a mathematical model that mechanistically relates the effect of nutrient availability throughout cell culture with the glycan profile of a mAb. The model was constructed from three individual ones. The first model describes the N-linked glycosylation process which occurs in the Golgi apparatus. The second model is unstructured and describes cell culture dynamics. The third and final model describes the biosynthetic pathway for nucleotide sugars. All three models were developed independently, but were adapted with features so that they could be interconnected. The glycosylation model approximates the Golgi apparatus to a single plug flow reactor where resident proteins (glycosylation enzymes and transport proteins) are recycled from distal portions of the Golgi space to proximal ones. Optimisation-based methods were developed to estimate unknown parameters of the model. The cell culture dynamics model was developed to represent cell growth, nutrient consumption and mAb synthesis. It was originally based on Monod kinetics, but was adapted to include experimentally-encountered complexity. The model for nucleotide metabolism was heuristically reduced from 35 constituting reactions to 7. Additional mechanistic features were adapted or included to ensure model fidelity. Experimentally, batch cultures were performed with hybridoma (CRL-1606 from ATCC). Data for viable cell density, glucose, glutamine, lactate, ammonia and mAb titre were collected. Intracellular samples were produced by perchloric acid extraction. These samples were then analysed for nucleotide sugar content using a high performance anion exchange chromatographic method which was optimized to quantify eight nucleotide sugars and four nucleotides in 30min. mAb bound glycans were analysed by MALDI mass spectrometry. The experimental data was used to estimate the unknown parameters of the models. The models – along with their associated parameters – were then combined to produce a coupled model that mechanistically relates nutrient availability with mAb glycosylation-associated quality. With further validation, such a model could be used for bioprocess design, control and optimization.
- Published
- 2013
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184. Genome-based metabolic modelling of CHO cells
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Chen, Ning and Kontoravdi, Cleo
- Subjects
660 - Abstract
Model-based analysis of cellular metabolism can facilitate our understanding of intracellular kinetics and aid the improvement of cell growth and biological product manufacturing. In this thesis, a model-based kinetic study of cytosolic glucose metabolism is presented. Based on the Kyoto Encyclopedia of Genes and Genomes and the Braunschweig Enzyme Database, a metabolic map of cytosolic glucose metabolism including 30 metabolites and 36 reactions, which consists of glycolysis, glucogenesis, pentose-phosphate pathway and adjacent metabolic reactions, has been constructed. Kinetic modelling was performed according to this metabolic map and reported enzyme kinetic studies, considering regulation and/or inhibition by products, substrates or other metabolites. Parameters were estimated based on previous parameter information and metabolic flux analysis studies, as well as results from our own experiments. Simulation results for cell population kinetics, metabolite concentrations and reaction rates have shown good agreement with experimental data. Furthermore, in silico case studies including global sensitivity analysis, feeding lactate as a co-substrate and the regulation effect by fructose 2,6-bisphosphate were performed in order to find strategies to increase metabolic efficiency in Chinese hamster ovary cells in an attempt to provide a guide for process optimisation. In conclusion, our model provides a deep look into cytosolic glucose metabolism and the simulation results have suggested a suitable direction to increase the metabolic efficiency.
- Published
- 2013
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185. Constrained global sensitivity analysis for bioprocess design space identification.
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Kotidis, Pavlos, Demis, Panagiotis, Goey, Cher H., Correa, Elisa, McIntosh, Calum, Trepekli, Stefania, Shah, Nilay, Klymenko, Oleksiy V., and Kontoravdi, Cleo
- Subjects
- *
BIOCHEMICAL engineering , *GLOBAL analysis (Mathematics) , *SENSITIVITY analysis , *CHO cell , *CELL culture , *PROTEIN structure - Abstract
Image, graphical abstract • Constrained global sensitivity analysis proposed for design space identification. • cGSA explores range of process inputs in silico subject to output constraints. • Applied to model of antibody-producing Chinese hamster ovary (CHO) cell culture system. • Findings verified experimentally for antibody titre and glycosylation as outputs. The manufacture of protein-based therapeutics presents unique challenges due to limited control over the biotic phase. This typically gives rise to a wide range of protein structures of varying safety and in vivo efficacy. Herein we propose a computational methodology, enabled by the application of constrained Global Sensitivity Analysis, for efficiently exploring the operating range of process inputs in silico and identifying a design space that meets output constraints. The methodology was applied to an antibody-producing Chinese hamster ovary (CHO) cell culture system: we explored >8000 feeding strategies to identify a subset of manufacturing conditions that meet constraints on antibody titre and glycan distribution as an attribute of product quality. Our computational findings were then verified experimentally, confirming the applicability of this approach to a challenging production system. We envisage that this methodology can significantly expedite bioprocess development and increase operational flexibility. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
186. Synergising stoichiometric modelling with artificial neural networks to predict antibody glycosylation patterns in Chinese hamster ovary cells.
- Author
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Antonakoudis, Athanasios, Strain, Benjamin, Barbosa, Rodrigo, Jimenez del Val, Ioscani, and Kontoravdi, Cleo
- Subjects
- *
CHO cell , *ARTIFICIAL neural networks , *MONOCLONAL antibodies , *GLYCOSYLATION , *RECOMBINANT proteins , *ARTIFICIAL cells , *BIOTECHNOLOGICAL process control - Abstract
• Stoichiometric model accurately describes CHO cell metabolism. • Artificial neural network used to model secreted antibody glycosylation. • Hybrid framework links extracellular culture conditions to recombinant protein quality. • Framework can be updated in-process with commonly monitored process variables. • Sets basis for bioprocess control. In-process quality control of biotherapeutics, such as monoclonal antibodies, requires computationally efficient process models that use readily measured process variables to compute product quality. Existing kinetic cell culture models can effectively describe the underlying mechanisms but require considerable development and parameterisation effort. Stoichiometric models, on the other hand, provide a generic, parameter-free means for describing metabolic behaviour but do not extend to product quality prediction. We have overcome this limitation by integrating a stoichiometric model of Chinese hamster ovary (CHO) cell metabolism with an artificial neural network that uses the fluxes of nucleotide sugar donor synthesis to compute the profile of Fc N-glycosylation, a critical quality attribute of antibody therapeutics. We demonstrate that this hybrid framework accurately computes glycan distribution profiles using a set of easy-to-obtain experimental data, thus providing a platform for process control applications. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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- View/download PDF
187. DigiGlyc: A hybrid tool for reactive scheduling in cell culture systems.
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Kotidis, Pavlos, Pappas, Iosif, Avraamidou, Styliana, Pistikopoulos, Efstratios N., Kontoravdi, Cleo, and Papathanasiou, Maria M.
- Subjects
- *
CELL culture , *MONOCLONAL antibodies , *CHO cell , *ANTIBODY formation , *HYBRID systems , *SCHEDULING - Abstract
• Development of a hybrid model for CHO cell culture using in silico training datasets • Model development focuses on antibody product synthesis and glycosylation • Glycosylation is one of main quality indicators for therapeutic antibodies • Hybrid model used as basis for the design of dynamic optimisation studies • Hybrid model used for reactive scheduling studies that assure product quality Chinese hamster ovary (CHO) cell culture systems are the most widely used platform for the industrial production of monoclonal antibodies (mAbs). The optimisation of manufacturing conditions for these high-value products is largely conducted off-line with little or no monitoring of mAb quality in-process. Here, we propose DigiGlyc, a hybrid model of these systems that predicts the critical quality attribute of mAb galactosylation. Having shown that DigiGlyc describes a wide range of experimental data well, we demonstrate that it can be used for the design of reactive optimisation studies. This hybrid formulation offers considerable gains in computational speed compared to mechanistic models with no loss in fidelity and can therefore underpin future online control and optimisation studies. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
188. Cascading effects in bioprocessing: the impact of cell culture environment on CHO cell behaviour and host cell protein species
- Author
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Goey, Cher Hui and Kontoravdi, Cleo
- Abstract
One of the reasons for the rejection of new drugs during clinical trials is the presence of host cell proteins (HCPs) in the drug formulation. HCPs are immunogenic impurities that can compromise patient safety. Moreover, proteolytic and binding HCPs compromise the integrity, and, hence, the stability and efficacy of a recombinant protein. Therefore, HCPs should be removed from the bioprocess train as soon as possible. Current downstream purification platforms are challenged by HCP-mAb co-elution. A Quality by Design strategy to overcome this problem is to reduce the number of HCPs in the downstream feedstock by tracing their source back to upstream culture and eliminating it. Previous studies have shown that upstream cell culture parameters, e.g. harvest time and culture temperature, significantly affect HCP profiles. However, little is known about how host cells coordinate and regulate their molecular machinery under different cell culture environment that results in different HCP profiles. This study presents experimental results linking cell culture temperature and key process indicators of CHO cell cultures and post-Protein A purification (mAb titre, HCP level and HCP species) by considering the cellular behaviour in terms of cell growth, cell cycle distribution and cell health). This study involved the application of single-use fed-batch bioreactors to culture IgG4 producing GS-CHO cell line, cell health and cell cycle analysis with NucleoCounter, Protein A purification and proteomic analysis with HCP ELISA kits and LC-MS/MS. Cells were more robust under mild hypothermia: over 90% of cells were maintained in a healthy state until the decline phase, and the onset of apoptosis was less evident compared to the results for physiological temperature. IgG4 titre and HCP level at harvest were comparable between the two cases. However, mild hypothermia reduced the HCP variety in HCCF by 36%, including 44% and 27% lower proteases and chaperones, respectively. The differences in HCP variety at harvest resulted in a significantly different HCP profile post-Protein A purification between the two cases. Half of the critically immunogenic HCPs species as determined by the CHOPPI tool were different between the two cases. This study shows that cell culture conditions significantly affect the HCP profile at harvest and that of purified samples. Open Access
- Published
- 2016
189. Modelling the osmotic behaviour of human mesenchymal stem cells.
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Casula, Elisa, Traversari, Gabriele, Fadda, Sarah, Klymenko, Oleksiy V., Kontoravdi, Cleo, and Cincotti, Alberto
- Subjects
- *
HUMAN stem cells , *MESENCHYMAL stem cells , *CORD blood , *CELLULAR mechanics , *OSMOTIC pressure , *CELL size , *CRYOPRESERVATION of organs, tissues, etc. , *ION channels - Abstract
• Non-perfect osmometer behavior of hMSCs from UCB described by a novel model. • A coupling of cell osmosis with mechanics and SAR is considered. • Mechanosensitive ion channels open when cell membrane stretches. • Comparison with data provided: fitting and validation through prediction. In this work, a novel mathematical model for the description of the osmotic behavior during the cryopreservation of human Mesenchymal Stem Cells (hMSCs) from Umbilical Cord Blood (UCB) is proposed. In cryopreservation, the two-parameter formalism of perfect osmometer behavior is typically adopted and preferred due to its simplicity: cell volume osmotic excursions are described as due only to the passive trans-membrane transport of water and permeant solutes such as cryoprotectant agents (CPAs); intracellular solutes, responsible of the isotonic osmolality, are assumed to be impermeant. The application of the two-parameter model fails to capture the osmotic response of hMSCs whenever a swelling phase is involved, as demonstrated by the authors. To overcome this limitation, the imperfect osmometer behavior of hMSCs is successfully modelled herein by improving the two-parameter formalism through the coupling of osmosis with cell mechanics and cell membrane Surface Area Regulation (SAR): now the transmembrane permeation of solutes (ions/salt) during the swelling phase through the temporary opening of mechanosensitive channels is allowed. This way cells can reach an equilibrium volume different from the initial isotonic one, when isotonic conditions are re-established after contact with impermeant or permeant solutes, such as sucrose or dimethyl-sulfoxide (DMSO), respectively. The sequential best-fit procedure adopted to adjust model parameters is reported herein along with model validation through full predictions. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
190. Understanding the impact of bioprocess conditions on monoclonal antibody glycosylation in mammalian cell cultures through experimental and computational analyses
- Author
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Sou, Si Nga, Kontoravdi, Cleo, Polizzi, Karen M, and Biotechnology and Biological Sciences Research Council (Great Britain)
- Abstract
With positive outcomes from medical treatments, monoclonal antibodies (mAbs) are to date the best-selling biologics in the pharmaceutical market. The fact that a lot of blockbuster drugs are facing the period of patent cliffs and patents of many of them are due to expire in the next 5 years, places an urgency for better, cheaper and more efficient bioproduction processes, as well as the development of novel drugs and biosimilars. To address to this issue, application of the Quality by Design paradigm that was introduced by the Food and Drug Administration (FDA) is of paramount importance. Medical values and safety of monoclonal antibodies have been reported to rely on the carbohydrate structures that are attached to the mAb N-linked glycosylation site on each constant region. Fc-N-linked glycosylation is considered as a critical quality attribute (CQA) of these therapeutic proteins under the scope of Quality by Design. It was also reported that different bioprocess conditions during recombinant mAb production directly impact glycan compositions and their distribution on the molecules, although the mechanism behind this change is not fully understood. This lack of understanding limits process design and optimisation. To address this issue we examined the effect of mild hypothermia (32oC) and the different recombinant expression systems on mAb N-linked glycosylation, using experiments, flux balance analysis (FBA) and mechanistic modelling to identify resulting differences in cell metabolism. A defined mathematical model that mechanistically and quantitatively describes CHO cell behaviour and metabolism, mAb synthesis and its N-linked glycosylation profiles before and after the induction of mild hypothermia in SGE and TGE expression systems was also constructed, which we believe is the first quantitative model that relates mild hypothermia and TGE system to the four elements mentioned above. Not only does the model aid understanding of the way bioprocess conditions affect product quality, it also provides a platform for bioprocess design, control and optimisation in industry and helps the implementation of the Quality by Design principles. Results obtained from our computational studies suggested glycosyltransferases to be the key players for changes observed among different bioprocess conditions, based on results obtained from this thesis we then manipulated the expression of galactosyltransferase in particular, through a proof-of-concept experiment using miRNAs. Open Access
- Published
- 2015
- Full Text
- View/download PDF
191. Unravelling the progression of unfolded protein Rresponse in a model system of familial Alzheimer’s disease
- Author
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Stefani Chrysoula, Ioanna, Kontoravdi, Cleo, Polizzi, Karen, and Engineering and Physical Sciences Research Council
- Abstract
Alzheimer’s disease (AD) is the most common form of dementia disorders and, yet, there is no preventative or curative treatment. It is associated with the progressive loss of memory and cognition and clinically divided into sporadic and familial forms. Familial Alzheimer’s disease (FAD) has predominantly a genetic predisposition with inherited mutations in the amyloid-β precursor protein (APP) and presinilin genes, which promote APP processing through the amyloidogenic pathway. This results in the release of the Aβ peptide, a major neurotoxic agent in AD progression. Accumulation of unfolded and misfolded disease-specific proteins (including Aβ and tau proteins) in neuronal cells perturbs endoplasmic reticulum (ER) homeostasis, leading to the onset of a cellular stress cascade called unfolded protein response (UPR), markers of which are upregulated in AD brain specimens. This suggests a possible role for ER stress in activation and the pathogenesis of AD. The research aimed to investigate the dynamic response of the UPR in an experimental model system of the disease combined with a computational model. For this purpose human neuroblastoma cell lines overexpressing the wild-type (APPWT) and two mutant forms of APP (APPMUT) associated with FAD were generated. Gene expression analysis of UPR markers revealed that overexpression of APP induces preconditioning of ER stress in all cell lines but with a stronger response in FAD-associated mutants. The progression sequence of UPR in APPWT and APPMUT was investigated in a time-course manner following the application of chemical stress. The results revealed that APPMUT exhibited the highest global response to chemically induced stress with a similar pattern. A computational model of the mammalian UPR was then generated and used to understand the dynamics of UPR. The model was able to reproduce our experimental data, which included pre-existing genetic factors (mutations in APP-associated with FAD) and a mimic of environmental triggers (induction of stress) consequently triggering the stress response. It suggested a different protein load and magnitude of transcriptional activation upon stress among the three cell lines. This was followed by in silico case studies exploring the effect of drugs targeting different branches of the UPR. This study proposes a novel multidisciplinary platform that could be further used for the development of therapeutics for AD. As the familial and sporadic form of the disease have similar neuropathological characteristics, drugs efficacious for FAD will also be beneficial for the most common form of AD. Open Access
- Published
- 2014
- Full Text
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192. Modelling as a tool for increasing the specific productivity of single-chain antibody fragments from Pichia pastoris
- Author
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Royle, Kate, Leak, David, Kontoravdi, Cleo, Bundy, Jake, and Biotechnology and Biological Sciences Research Council (Great Britain)
- Abstract
Pichia pastoris is a commonly used recombinant protein expression host, predominantly due to ease of genetic manipulation and its capacity for high cell densities in cheap culture media. While considerable yields can be achieved in this way, the specific productivity is relatively low. Consequently, the full impact of this host on industrial biotechnology has not yet been realised. This research aimed to develop a strategy to optimise production of single chain antibody fragments (scFvs), an industrially relevant protein, using an integrated modelling and experimental approach. Initially, a dynamic model was constructed from literature sources to reproduce the scFv production pathway in P. pastoris. It incorporated aspects of transcription, translation, folding and misfolding in the endoplasmic reticulum (ER). Moreover, the unfolded protein response (UPR) and ER-associated degradation (ERAD) were added as these two stress pathways are crucial to productivity. Simulations qualitatively reproduced phenomena including secretion saturation and the negative influence of high gene copy numbers on yield. The model was used to target evaluation of the experimental system: P. pastoris strains expressing the scFvs BC1 and MFE23. RT Q-PCR and LC-MS/MS results revealed some surprising correlations between certain factors, such as the concentration of Kar2 and PDI, and yield. Moreover, it showed that there was more than one route to high productivity. Finally, it suggested that there may be an internal regulation of Kar2 that would be crucial to strategies aiming to increase yield through overexpression of that chaperone. Together, the results revealed a more complex picture of productivity than previously understood. In order to develop a strategy for optimal scFv production in P. pastoris, a greater understanding of the underlying biology and biochemistry is required. This research has suggested targets for future work which should generate insight into the network of factors responsible. Open Access
- Published
- 2013
193. Assessment of the interactions between bioprocess conditions and protein glycosylation in antibody- producing mammalian cell cultures
- Author
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Jimenez Del Val, Ioscani, Kontoravdi, Cleo, Nagy, Judit, Mexican National Council for Science and Technology, Mario Molina Fund, Secretaría de Educación Pública (Mexico), and Biotechnology and Biological Sciences Research Council (Great Britain)
- Abstract
The pharmaceutical industry is going through a rather turbulent period. Many blockbuster drugs have fallen off patent over the past two years and many more are expected to do so in the near future. In response, pharmaceutical companies have continued searching for products that will replace those that have lost patent protection. However, drug development and approval is extremely time-consuming and costly. So that this critical issue is addressed, industry experts and regulatory agencies have jointly proposed the implementation of Quality by Design (QbD) principles in the development and manufacture of all new drugs. Adoption of QbD is expected to reduce drug development cost and approval time. It is also expected to encourage innovation by developing drugs, and the processes used to manufacture them, around the mechanisms that relate process inputs with end product quality. Within this context, monoclonal antibodies (mAbs) are currently the highest-selling products of the biopharmaceutical industry and are projected to account for nearly half of the world’s top-selling drugs by 2018. All currently commercialized mAbs contain N-linked glycans (complex carbohydrates) bound to their protein backbone. These carbohydrates, in turn, have been widely reported to impact the safety and efficacy of mAbs. Furthermore, it has widely been reported that bioprocess conditions heavily impact the composition and distribution of these glycans. For these reasons, mAb glycosylation is considered a critical quality attribute (CQA) of these therapeutic proteins under the QbD scope. Based on QbD principles, the objective of this thesis was to generate a mathematical model that mechanistically relates the effect of nutrient availability throughout cell culture with the glycan profile of a mAb. The model was constructed from three individual ones. The first model describes the N-linked glycosylation process which occurs in the Golgi apparatus. The second model is unstructured and describes cell culture dynamics. The third and final model describes the biosynthetic pathway for nucleotide sugars. All three models were developed independently, but were adapted with features so that they could be interconnected. The glycosylation model approximates the Golgi apparatus to a single plug flow reactor where resident proteins (glycosylation enzymes and transport proteins) are recycled from distal portions of the Golgi space to proximal ones. Optimisation-based methods were developed to estimate unknown parameters of the model. The cell culture dynamics model was developed to represent cell growth, nutrient consumption and mAb synthesis. It was originally based on Monod kinetics, but was adapted to include experimentally-encountered complexity. The model for nucleotide metabolism was heuristically reduced from 35 constituting reactions to 7. Additional mechanistic features were adapted or included to ensure model fidelity. Experimentally, batch cultures were performed with hybridoma (CRL-1606 from ATCC). Data for viable cell density, glucose, glutamine, lactate, ammonia and mAb titre were collected. Intracellular samples were produced by perchloric acid extraction. These samples were then analysed for nucleotide sugar content using a high performance anion exchange chromatographic method which was optimized to quantify eight nucleotide sugars and four nucleotides in 30min. mAb bound glycans were analysed by MALDI mass spectrometry. The experimental data was used to estimate the unknown parameters of the models. The models – along with their associated parameters – were then combined to produce a coupled model that mechanistically relates nutrient availability with mAb glycosylation-associated quality. With further validation, such a model could be used for bioprocess design, control and optimization.
- Published
- 2012
- Full Text
- View/download PDF
194. Degradation bottlenecks and resource competition in transiently and stably engineered mammalian cells.
- Author
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Gabrielli J, Di Blasi R, Kontoravdi C, and Ceroni F
- Subjects
- Humans, HEK293 Cells, Animals, Protein Stability, Cell Engineering methods, Proteolysis
- Abstract
Degradation tags, otherwise known as degrons, are portable sequences that can be used to alter protein stability. Here, we report that degron-tagged proteins compete for cellular degradation resources in engineered mammalian cells leading to coupling of the degradation rates of otherwise independently expressed proteins when constitutively targeted human degrons are adopted. We show the effect of this competition to be dependent on the context of the degrons. By considering different proteins, degron position and cellular hosts, we highlight how the impact of the degron on both degradation strength and resource coupling changes, with identification of orthogonal combinations. By adopting inducible bacterial and plant degrons we also highlight how controlled uncoupling of synthetic construct degradation from the native machinery can be achieved. We then build a genomically integrated capacity monitor tagged with different degrons and confirm resource competition between genomic and transiently expressed DNA constructs. This work expands the characterisation of resource competition in engineered mammalian cells to protein degradation also including integrated systems, providing a framework for the optimisation of heterologous expression systems to advance applications in fundamental and applied biological research., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)
- Published
- 2025
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- View/download PDF
195. GlyCompute: towards the automated analysis of protein N-linked glycosylation kinetics via an open-source computational framework.
- Author
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Flevaris K, Kotidis P, and Kontoravdi C
- Abstract
Understanding the complex biosynthetic pathways of glycosylation is crucial for the expanding field of glycosciences. Computer-aided glycosylation analysis has greatly benefited in recent years from the development of tools found in web-based portals and open-source libraries. However, the in silico analysis of cellular glycosylation kinetics is underrepresented in current glycoscience-related tools and databases. This could be partly attributed to the limited accessibility of kinetic models developed using proprietary software and the difficulty in reliably parameterising such models. This work aims to address these challenges by proposing GlyCompute, an open-source framework demonstrating a novel, streamlined approach for the assembly, simulation, and parameterisation of kinetic models of protein N-linked glycosylation. Specifically, given one or more sets of experimentally observed N-glycan structures and their relative abundances, minimum representations of a glycosylation reaction network are generated. The topology of the resulting networks is then used to automatically assemble the material balances and kinetic mechanisms underpinning the mathematical model. To match the experimentally observed relative abundances, a sequential parameter estimation strategy using Bayesian inference is proposed, with stages determined automatically based on the underlying network topology. The proposed framework was tested on a case study involving the simultaneous fitting of the kinetic model to two protein N-linked glycoprofiles produced by the same CHO cell culture, showing good agreement with experimental observations. We envision that GlyCompute could help glycoscientists gain quantitative insights into the effect of enzyme kinetics and their perturbations on experimentally observed glycoprofiles in biomanufacturing and clinical settings., (© 2024. The Author(s).)
- Published
- 2024
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196. Fluorescence diffuse optical monitoring of bioreactors: a hybrid deep learning and model-based approach for tomography.
- Author
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Cao J, Gorecki J, Dale R, Redwood-Sawyerr C, Kontoravdi C, Polizzi K, Rowlands CJ, and Dehghani H
- Abstract
Biosynthesis in bioreactors plays a vital role in many applications, but tools for accurate in situ monitoring of the cells are still lacking. By engineering the cells such that their conditions are reported through fluorescence, it is possible to fill in the gap using fluorescence diffuse optical tomography (fDOT). However, the spatial accuracy of the reconstruction can still be limited, due to e.g. undersampling and inaccurate estimation of the optical properties. Utilizing controlled phantom studies, we use a two-step hybrid approach, where a preliminary fDOT result is first obtained using the classic model-based optimization, and then enhanced using a neural network. We show in this paper using both simulated and phantom experiments that the proposed method can lead to a 8-fold improvement (Intersection over Union) of fluorescence inclusion reconstruction in noisy conditions, at the same speed of conventional neural network-based methods. This is an important step towards our ultimate goal of fDOT monitoring of bioreactors., Competing Interests: The authors declare no conflicts of interest., (© 2024 The Author(s).)
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- 2024
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197. Immobilized enzyme cascade for targeted glycosylation.
- Author
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Makrydaki E, Donini R, Krueger A, Royle K, Moya Ramirez I, Kuntz DA, Rose DR, Haslam SM, Polizzi KM, and Kontoravdi C
- Subjects
- Glycosylation, Humans, Polysaccharides metabolism, Polysaccharides chemistry, Protein Processing, Post-Translational, Enzymes, Immobilized chemistry, Enzymes, Immobilized metabolism, Galactosyltransferases metabolism, Galactosyltransferases chemistry
- Abstract
Glycosylation is a critical post-translational protein modification that affects folding, half-life and functionality. Glycosylation is a non-templated and heterogeneous process because of the promiscuity of the enzymes involved. We describe a platform for sequential glycosylation reactions for tailored sugar structures (SUGAR-TARGET) that allows bespoke, controlled N-linked glycosylation in vitro enabled by immobilized enzymes produced with a one-step immobilization/purification method. We reconstruct a reaction cascade mimicking a glycosylation pathway where promiscuity naturally exists to humanize a range of proteins derived from different cellular systems, yielding near-homogeneous glycoforms. Immobilized β-1,4-galactosyltransferase is used to enhance the galactosylation profile of three IgGs, yielding 80.2-96.3% terminal galactosylation. Enzyme recycling is demonstrated for a reaction time greater than 80 h. The platform is easy to implement, modular and reusable and can therefore produce homogeneous glycan structures derived from various hosts for functional and clinical evaluation., (© 2024. The Author(s).)
- Published
- 2024
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198. Machine learning framework to extract the biomarker potential of plasma IgG N-glycans towards disease risk stratification.
- Author
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Flevaris K, Davies J, Nakai S, Vučković F, Lauc G, Dunlop MG, and Kontoravdi C
- Abstract
Effective management of chronic diseases and cancer can greatly benefit from disease-specific biomarkers that enable informative screening and timely diagnosis. IgG N-glycans found in human plasma have the potential to be minimally invasive disease-specific biomarkers for all stages of disease development due to their plasticity in response to various genetic and environmental stimuli. Data analysis and machine learning (ML) approaches can assist in harnessing the potential of IgG glycomics towards biomarker discovery and the development of reliable predictive tools for disease screening. This study proposes an ML-based N-glycomic analysis framework that can be employed to build, optimise, and evaluate multiple ML pipelines to stratify patients based on disease risk in an interpretable manner. To design and test this framework, a published colorectal cancer (CRC) dataset from the Study of Colorectal Cancer in Scotland (SOCCS) cohort (1999-2006) was used. In particular, among the different pipelines tested, an XGBoost-based ML pipeline, which was tuned using multi-objective optimisation, calibrated using an inductive Venn-Abers predictor (IVAP), and evaluated via a nested cross-validation (NCV) scheme, achieved a mean area under the Receiver Operating Characteristic Curve (AUC-ROC) of 0.771 when classifying between age-, and sex-matched healthy controls and CRC patients. This performance suggests the potential of using the relative abundance of IgG N-glycans to define populations at elevated CRC risk who merit investigation or surveillance. Finally, the IgG N-glycans that highly impact CRC classification decisions were identified using a global model-agnostic interpretability technique, namely Accumulated Local Effects (ALE). We envision that open-source computational frameworks, such as the one presented herein, will be useful in supporting the translation of glycan-based biomarkers into clinical applications., Competing Interests: Gordan Lauc is the founder and CEO of Genos Ltd. Frano Vučković is employee of Genos Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 The Authors.)
- Published
- 2024
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- View/download PDF
199. Quality by Design Framework Applied to GMMA Purification.
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Giannelli C, Necchi F, Palmieri E, Oldrini D, Ricchetti B, Papathanasiou MM, Kis Z, Kontoravdi C, Campa C, and Micoli F
- Subjects
- Vaccines, Vaccine Development
- Abstract
In recent years, Generalized Modules for Membrane Antigens (GMMA) have received increased attention as an innovative vaccine platform against bacterial pathogens, particularly attractive for low- and middle-income countries because of manufacturing simplicity. The assessment of critical quality attributes (CQAs), product-process interactions, identification of appropriate in process analytical methods, and process modeling is part of a robust quality by design (QbD) framework to support further development and control of manufacturing processes. QbD implementation in the context of the GMMA platform will ensure robust manufacturing of batches with desired characteristics, facilitating technical transfer to local manufacturers, regulatory approval, and commercialization of vaccines based on this technology. Here, we summarize the methodology suggested, applied to a first step of GMMA manufacturing process., (© 2024. The Author(s).)
- Published
- 2024
- Full Text
- View/download PDF
200. Strategic Planning of a Joint SARS-CoV-2 and Influenza Vaccination Campaign in the UK.
- Author
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Ibrahim D, Kis Z, Papathanasiou MM, Kontoravdi C, Chachuat B, and Shah N
- Abstract
The simultaneous administration of SARS-CoV-2 and influenza vaccines is being carried out for the first time in the UK and around the globe in order to mitigate the health, economic, and societal impacts of these respiratory tract diseases. However, a systematic approach for planning the vaccine distribution and administration aspects of the vaccination campaigns would be beneficial. This work develops a novel multi-product mixed-integer linear programming (MILP) vaccine supply chain model that can be used to plan and optimise the simultaneous distribution and administration of SARS-CoV-2 and influenza vaccines. The outcomes from this study reveal that the total budget required to successfully accomplish the SARS-CoV-2 and influenza vaccination campaigns is equivalent to USD 7.29 billion, of which the procurement costs of SARS-CoV-2 and influenza vaccines correspond to USD 2.1 billion and USD 0.83 billion, respectively. The logistics cost is equivalent to USD 3.45 billion, and the costs of vaccinating individuals, quality control checks, and vaccine shipper and dry ice correspond to USD 1.66, 0.066, and 0.014, respectively. The analysis of the results shows that the choice of rolling out the SARS-CoV-2 vaccine during the vaccination campaign can have a significant impact not only on the total vaccination cost but also on vaccine wastage rate.
- Published
- 2024
- Full Text
- View/download PDF
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