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Mayra M F Barbosa,1,2 Alex I Kanno,1 Giovana C Barazzone,1 Dunia Rodriguez,1 Violeta Pancakova,1,3 Monalisa Trentini,1 Eliana L Faquim-Mauro,4 Amanda P Freitas,4 Mariana I Khouri,5 Jessica Lobo-Silva,5 Viviane M Goncalves,1 Rocilda P F Schenkman,1 Martha M Tanizaki,1 Diana Boraschi,6– 8 Richard Malley,9 Leonardo P Farias,5 Luciana C C Leite1 1Laboratório de Desenvolvimento de Vacinas, Instituto Butantan, São Paulo, Brazil; 2Programa de Pós-Graduação Interunidades em Biotecnologia, Universidade de São Paulo, São Paulo, Brazil; 3Université Claude Bernard Lyon 1 (UCBL1), Villeurbanne, 69100, France; 4Laboratório de Imunopatologia, Instituto Butantan, São Paulo, Brazil; 5Laboratório de Biomarcadores e Inflamação, Instituto Gonçalo Moniz, Fundação Oswaldo Cruz, Salvador, Brazil; 6Istituto di Biochimica e Biologia Cellulare, Consiglio Nazionale delle Ricerche, Napoli, Italy; 7Stazione Zoologica Anton Dohrn, Napoli, Italy; 8Shenzhen Institute of Advanced Technologies (SIAT), Chinese Academy of Sciences (CAS), Shenzhen, China Division of Infectious Diseases, Boston Children’s Hospital, Boston, MA, USA; 9Division of Infectious Diseases, Boston Children’s Hospital, Boston, MA, USACorrespondence: Luciana C C LeiteLaboratório de Desenvolvimento de Vacinas, Instituto Butantan, Av. Vital Brasil, São Paulo, 1500, SP, BrazilTel +55-11-2627-9816Email luciana.leite@butantan.gov.brPurpose: The use of adjuvants can significantly strengthen a vaccine’s efficacy. We sought to explore the immunization efficacy of bacterial outer membrane vesicles (OMVs) displaying the Schistosoma mansoni antigen, SmTSP-2, through a biotin-rhizavidin coupling approach. The rationale is to exploit the nanoparticulate structure and the adjuvant properties of OMVs to induce a robust antigen-specific immune response, in light of developing new vaccines against S. mansoni.Materials and Methods: OMVs were obtained from Neisseria lactamica and conjugated with biotin. The recombinant SmTSP-2 in fusion with the biotin-binding protein rhizavidin (rRzvSmTSP-2) was produced in E. coli and coupled to biotinylated OMVs to generate an OMV complex displaying SmTSP-2 on the membrane surface (OMV:rSmTSP-2). Transmission electron microscopy (TEM) and dynamic light scattering analysis were used to determine particle charge and size. The immunogenicity of the vaccine complex was evaluated in C57BL/6 mice.Results: The rRzvSmTSP-2 protein was successfully coupled to biotinylated OMVs and purified by size-exclusion chromatography. The OMV:rSmTSP-2 nanoparticles showed an average size of 200 nm, with zeta potential around – 28 mV. Mouse Bone Marrow Dendritic Cells were activated by the nanoparticles as determined by increased expression of the co-stimulatory molecules CD40 and CD86, and the proinflammatory cytokines (TNF-α, IL-6 and IL-12) or IL-10. Splenocytes of mice immunized with OMV:rSmTSP-2 nanoparticles reacted to an in vitro challenge with SmTSP-2 with an increased production of IL-6, IL-10 and IL-17 and displayed a higher number of CD4+ and CD8+ T lymphocytes expressing IFN-γ, IL-4 and IL-2, compared to mice immunized with the antigen alone. Immunization of mice with OMV:rSmTSP-2 induced a 100-fold increase in specific anti-SmTSP-2 IgG antibody titers, as compared to the group receiving the recombinant rSmTSP-2 protein alone or even co-administered with unconjugated OMV.Conclusion: Our results demonstrate that the SmTSP-2 antigen coupled with OMVs is highly immunogenic in mice, supporting the potential effectiveness of this platform for improved antigen delivery in novel vaccine strategies.Keywords: Schistosoma mansoni, vaccine, TSP-2 antigen, outer membrane vesicles, OMV, biotin-avidin coupling, nanoparticle

Schistosomiasis causes significant morbidity and mortality. Vaccine efforts to date indicate the need to increase the immunogenicity of Schistosoma antigens. The multiple antigen-presenting system, whereby proteins are genetically fused to rhizavidin and affinity linked to biotinylated templates, enables the generation of robust immune responses. The objective of this work was to express and purify the S. mansoni antigens, SmTSP-2 and SmCD59.2, in fusion with rhizavidin. The fusion with rhizavidin greatly decreased the expression level of rSmTSP-2, but not rSmCD59.2, and both were expressed in the insoluble fraction, requiring optimization of culture conditions. Evaluation of different E. coli strains and media showed that BL21-DE3 cultured in Terrific Broth provided the highest expression levels of both proteins. Investigation of a range of time and temperature of induction showed that E. coli strains expressing rRzv:SmTSP-2 and rRzv:SmCD59.2 showed the highest protein production at 23 °C for 15 h. Recombinant proteins were purified by a single step of affinity chromatography allowing isolation of these proteins in high concentration and purity. The optimization process increased final soluble protein yield of rRzv:SmTSP-2 by fourfold and rRzv:SmCD59.2 by tenfold, providing ~ 20 mg/L of each protein. Optimized fusion protein production will allow antigen use in biotin–rhizavidin affinity platforms. Supplementary Information The online version contains supplementary material available at 10.1007/s12033-021-00355-2.

Diagnosing Zika virus (ZIKV) infections has been challenging due to the cross-reactivity of induced antibodies with other flavivirus. The concomitant occurrence of ZIKV and Dengue virus (DENV) in endemic regions requires diagnostic tools with the ability to distinguish these two viral infections. Recent studies demonstrated that immunoassays using the C-terminal fragment of ZIKV NS1 antigen (ΔNS1) can be used to discriminate ZIKV from DENV infections. In order to be used in serological tests, the expression/solubility of ΔNS1 and growth of recombinant E. coli strain were optimized by Response Surface Methodology. Temperature, time and IPTG concentration were evaluated. According to the model, the best condition determined in small scale cultures was 21 °C for 20 h with 0.7 mM of IPTG, which predicted 7.5 g/L of biomass and 962 mg/L of ΔNS1. These conditions were validated and used in a 6-L batch in the bioreactor, which produced 6.4 g/L of biomass and 500 mg/L of ΔNS1 in 12 h of induction. The serological ELISA test performed with purified ΔNS1 showed low cross-reactivity with antibodies from DENV-infected human subjects. Denaturation of ΔNS1 decreased the detection of anti-ZIKV antibodies, thus indicating the contribution of conformational epitopes and confirming the importance of properly folded ΔNS1 for the specificity of the serological analyses. Obtaining high yields of soluble ΔNS1 supports the viability of an effective serologic diagnostic test capable of differentiating ZIKV from other flavivirus infections.

The granulocyte colony-stimulating factor (G-CSF) is a hematopoietic cytokine that has important clinical applications for treating neutropenia. Nartograstim is a recombinant variant of human G-CSF. Nartograstim has been produced in Escherichia coli as inclusion bodies (IB) and presents higher stability and biological activity than the wild type of human G-CSF because of its mutations. We developed a production process of nartograstim in a 10-L bioreactor using auto-induction or chemically defined medium. After cell lysis, centrifugation, IB washing, and IB solubilization, the following three refolding methods were evaluated: diafiltration, dialysis, and direct dilution in two refolding buffers. Western blot and SDS-PAGE confirmed the identity of 18.8-kDa bands as nartograstim in both cultures. The auto-induction medium produced 1.17 g/L and chemically defined medium produced 0.95 g/L. The dilution method yielded the highest percentage of refolding (99%). After refolding, many contaminant proteins precipitated during pH adjustment to 5.2, increasing purity from 50 to 78%. After applying the supernatant to cation exchange chromatography (CEC), nartograstim recovery was low and the purity was 87%. However, when the refolding solution was applied to anion exchange chromatography followed by CEC, 91%-98% purity and 2.2% recovery were obtained. The purification process described in this work can be used to obtain nartograstim with high purity, structural integrity, and the expected biological activity. KEY POINTS: • Few papers report the final recovery of the purification process from inclusion bodies. • The process developed led to high purity and reasonable recovery compared to literature. • Nartograstim biological activity was demonstrated in mice using a neutropenia model.

The available pneumococcal conjugate vaccines provide protection against only those serotypes that are included in the vaccine, which leads to a selective pressure and serotype replacement in the population. An alternative low-cost, safe and serotype-independent vaccine was developed based on a nonencapsulated pneumococcus strain. This study evaluates process intensification to improve biomass production and shows for the first time the use of perfusion-batch with cell recycling for bacterial vaccine production. Batch, fed-batch, and perfusion-batch were performed at 10 L scale using a complex animal component-free culture medium. Cells were harvested at the highest optical density, concentrated and washed using microfiltration or centrifugation to compare cell separation methods. Higher biomass was achieved using perfusion-batch, which removes lactate while retaining cells. The biomass produced in perfusion-batch would represent at least a fourfold greater number of doses per cultivation than in the previously described batch process. Each strategy yielded similar vaccines in terms of quality as evaluated by western blot and animal immunization assays, indicating that so far, perfusion-batch is the best strategy for the intensification of pneumococcal whole-cell vaccine production, as it can be integrated to the cell separation process keeping the same vaccine quality.

This article aims to review the present status of anti-flavivirus subunit vaccines, both those at the experimental stage and those already available for clinical use. Aspects regarding development of vaccines to Yellow Fever virus, (YFV), Dengue virus (DENV), West Nile virus (WNV), Zika virus (ZIKV), and Japanese encephalitis virus (JEV) are highlighted, with particular emphasis on purified recombinant proteins generated in bacterial cells. Currently licensed anti-flavivirus vaccines are based on inactivated, attenuated, or virus-vector vaccines. However, technological advances in the generation of recombinant antigens with preserved structural and immunological determinants reveal new possibilities for the development of recombinant protein-based vaccine formulations for clinical testing. Furthermore, novel proposals for multi-epitope vaccines and the discovery of new adjuvants and delivery systems that enhance and/or modulate immune responses can pave the way for the development of successful subunit vaccines. Nonetheless, advances in this field require high investments that will probably not raise interest from private pharmaceutical companies and, therefore, will require support by international philanthropic organizations and governments of the countries more severely stricken by these viruses.

The pneumococcal whole cell vaccine (PWCV) has been investigated as an alternative to polysaccharide-based vaccines currently in use. It is a non-encapsulated killed vaccine preparation that induces non-capsular antibodies protecting mice against invasive pneumococcal disease (IPD) and reducing nasopharyngeal (NP) carriage via IL-17A activation of mouse phagocytes. Here, we show that PWCV induces antibody and IL-17A production to protect mice against challenge in a fatal aspiration-sepsis model after only one dose. We observed protection even with a boiled preparation, attesting to the stability and robustness of the vaccine. PWCV antibodies were shown to bind to different encapsulated strains, but complement deposition on the pneumococcal surface was observed only on serotype 3 strains; using flow cytometer methodology, variations in PWCV quality, as in the boiled vaccine, were detected. Moreover, anti-PWCV induces phagocytosis of different pneumococcal serotypes by murine peritoneal cells in the presence of complement or IL-17A. These findings suggest that complement and IL-17A may participate in the process of phagocytosis induced by PWCV antibodies. IL-17A can stimulate phagocytic cells to kill pneumococcus and this is enhanced in the presence of PWCV antibodies bound to the bacterial cell surface. Our results provide further support for the PWCV as a broad-range vaccine against all existing serotypes, potentially providing protection for humans against NP colonization and IPD. Additionally, we suggest complement deposition assay as a tool to detect subtle differences between PWCV lots.

Introduction: Lower respiratory tract infections are the fourth cause of death worldwide and pneumococcus is the leading cause of pneumonia. Nonetheless, existing pneumococcal vaccines are less effective against pneumonia than invasive diseases and serotype replacement is a major concern. Protein antigens could induce serotype-independent protection, and mucosal immunization could offer local and systemic immune responses and induce protection against pneumococcal colonization and lung infection. Areas covered: Immunity induced in the experimental human pneumococcal carriage model, approaches to address the physiological barriers to mucosal immunization and improve delivery of the vaccine antigens, different strategies already tested for pneumococcal mucosal vaccination, including live recombinant bacteria, nanoparticles, bacterium-like particles, and nanogels as well as, nasal, pulmonary, sublingual and oral routes of vaccination. Expert opinion: The most promising delivery systems are based on nanoparticles, bacterial-like particles or nanogels, which possess greater immunogenicity than the antigen alone and are considered safer than approaches based on living cells or toxoids. These particles can protect the antigen from degradation, eliminating the refrigeration need during storage and allowing the manufacture of dry powder formulations. They can also increase antigen uptake, control release of antigen and trigger innate immune responses.

RESUMO A baixa cobertura em termos de sorotipos das vacinas atuais contra S. pneumoniae tem levado a busca por novos antigenos que oferecam protecao independente de sorotipos. Assim, este trabalho propoe a producao de um hibrido das proteinas PspA e pneumolisina geneticamente detoxificada, que mostrou-se imunogenico e protetor em camundongos. Para isso a molecula foi obtida em E. coli com cauda de histidina. Os cultivos foram realizados em reator de 5L e a purificacao seguiu as seguintes etapas: ruptura celular em homogeneizador continuo de alta pressao, precipitacao com detergente cationico CTAB, clarificacao, cromatografia de troca anionica e cromatografia de interacao hidrofobica, alcancando 85% de pureza e recuperacao de 4%. A baixa recuperacao ocorreu porque o hibrido mostrou-se instavel.Duas bandas principais foram observadas na eletroforese, que correspondiam a cada uma das proteinas do hibrido, tal como revelado por Western Blot. Novas construcoes de hibridos estao sendo elaboradas com espacadores rigido e flexivel a fim de aumentar sua estabilidade.

Ion exchange chromatography is extensively used in the purification of biological compounds. Reliable mathematical models describing this chromatographic technique are available and can be used to improve the performance of this separation step. However, the use of synthetic mixtures for model development hampers the application of this approach with real cell extracts processed in downstream operations. This work presents an original approach for handling non-synthetic genuine mixtures of proteins, which was applied in the purification of an untagged recombinant pneumococcal surface protein A (PspA4Pro). First, evaluation was made of the efficiency of steric mass action (SMA) and modified Langmuir isotherms, which were separately used together with the equilibrium dispersive model (EDM). The data used for parameter estimation and model validation were obtained from anion exchange chromatography runs (employing Q-Sepharose FF), applied to real cell extracts produced by different cultivation strategies. Simulations showed that the models were able to describe the complex mixtures of unknown proteins. Next, the EDM and SMA approaches were used to separately describe the profile of PspA4Pro and the pool of protein impurities eluted together. The simulations showed that PspA4Pro tended to elute at the beginning of the peak, enabling the establishment of an alternative elution schedule that provided a 34% increase in the purity achieved using the anion exchange chromatography.

Attainment of a stable and highly active β-xylosidase is of major importance for the efficient and cost-competitive hydrolysis of hemicellulose xylan, as well as for its industrial conversion into biofuels and biochemicals. Here, a recombinant β-xylosidase of the glycoside hydrolase family (GH43) from Bacillus subtilis was produced in Escherichia coli culture, purified, and subsequently immobilized on agarose and chitosan. Glutaraldehyde and glyoxyl groups were evaluated as activating agents to select the most efficient derivative. Multi-point immobilization on agarose led to an extraordinary thermal stability (half-lives 3604 and 164-fold higher than the free enzyme, at 50° and 35 °C, respectively). Even for chitosan activated with glutaraldehyde, a low-cost support, thermal stability of the immobilized enzyme was 326 and 12-fold higher than the free enzyme at 50° and 35°C, respectively. Immobilized enzymes showed no release of any subunit for the agarose-glyoxyl derivative, and only a few ones for the support activated with glutaraldehyde. Most remarkably, the enzyme kinetic behavior after immobilization increased up to 4-fold in relation to the free one. β-xylosidase, a tetrameric enzyme with four identical subunits, exists in equilibrium between the monomeric and oligomeric forms in solution. Depending on the pH of immobilization, the enzyme oligomerization can be favored, thus explaining the hyperactivation phenomenon. Both glyoxyl-agarose and chitosan-glutaraldehyde derivatives were used to catalyze corncob xylan hydrolysis, reaching 72 % conversion, representing a xylose productivity of around 20 g L−1 h−1. After ten 4h-cycles (pH 6.0, 35 °C), the xylan-to-xylose conversion remained approximately unchanged. Therefore, the immobilized β-xylosidases prepared in this work can be of great interest as biocatalysts in a biorefinery context.

Standard cultivation protocols for high cell-density cultures of recombinant E. coli rely on air enrichment with oxygen to prevent oxygen limitation. This way of increasing oxygen supply impacts on process economics due to the high cost of pure oxygen. Reactor pressurization is an alternative approach to improve oxygen mass transfer. In the present study, the performance of pressurized airlift bioreactor in growing r E. coli cells was evaluated. Experiments were performed in a pressurized internal-loop airlift bioreactor (ALB) and in a non-pressurized stirred tank reactor (STR), both with 5 L working volume, equipped with a system for automatic control and monitoring of pressure, temperature, pH, and dissolved oxygen. Pressurization showed to be crucial to improve ALB performance in biomass formation (29 g DCW L −1 ) and protein production (201 mg protein g DCW −1 ), resulting in protein productivity (240 mg protein −1 h −1 ) and energy efficiency (11 g protein kWh −1 ) similar to the achieved in STR (200 mg protein L −1 h −1 and 13 g protein kWh −1 , respectively). Due to the high cost of pure oxygen, air enrichment revealed to be economically unfeasible for ALB. By pressurizing the bioreactor up to 0.41 MPa, without pure oxygen supply, an 8.7-fold increase in economic efficiency is estimated, what shows the potential of this innovative strategy for aerobic cultures.

The impact of cultivation strategy on the cost of recombinant protein production is crucial for defining cost-effective bioreactor operation conditions. This paper presents a methodology to estimate and compare cost impacts related to utilities as well as medium composition, using simple design equations and accessible data. Data from batch bioreactor cultures were used as case study involving the production of pneumococcal surface protein A, a soluble recombinant protein, employing E. coli BL21(DE3). Cultivation strategies and corresponding process costs covered a wide range of operational conditions, including different media, inducers, and temperatures. The core expenses were related to the medium and cooling. When the price of peptone was above the threshold value of US$ 30/kg, defined medium became the best choice. IPTG and temperatures around 32 °C led to shorter cultures and lower PspA4Pro production costs. The procedure offers a simple, accessible theoretical tool to identify cost-effective production strategies using bioreactors.

Expression vectors for industrial production should be stable and allow tight control of protein synthesis. This is necessary to ensure plasmid transmission to daughter cells in order to achieve a stable population capable of synthesizing high amounts of the target protein. A high-copy-number plasmid, pAE, was previously used for laboratory-scale production of recombinant human granulocyte colony-stimulating factor (rhG-CSF) and the Schistosoma mansoni fatty acid binding protein (rSm14), but it was unstable for large-scale production. Therefore, here we evaluated a new expression vector derived from pAE, pAR-KanI, which combines two plasmid replication strategies: a high-copy plasmid pUC origin of replication as pAE, and a par locus sequence derived from pSC101, which is typical of low copy plasmids, for rhG-CSF and rSm14 production in Escherichia coli. Clones bearing these constructs were cultivated in two complex media (2YT and auto-induction) and both yielded higher-than-95% resistant colonies, before and after induction, either with or without antibiotics. In 2YT medium, we obtained 244 μg/mL of rSm14, 181 μg/mL and 392 μg/mL for rhG-CSF, with and without glucose, respectively. In auto-induction medium without antibiotics, 147 μg/mL of rSm14 and 162 μg/mL of rhG-CSF were obtained. The new vector presented high stability for the production of both recombinant proteins in complex media in Escherichia coli, even in the absence of antibiotics, making the pAR-KanI a promising vector for industrial production of recombinant proteins.

Burden of pneumonia caused by Streptococcus pneumoniae remains high despite the availability of conjugate vaccines. Mucosal immunization targeting the lungs is an attractive alternative for the induction of local immune responses to improve protection against pneumonia. Our group had previously described the development of poly(glycerol adipate-co-ω-pentadecalactone) (PGA-co-PDL) polymeric nanoparticles (NPs) adsorbed with Pneumococcal surface protein A from clade 4 (PspA4Pro) within L-leucine microcarriers (nanocomposite microparticles-NCMPs) for mucosal delivery targeting the lungs (NP/NCMP PspA4Pro). NP/NCMP PspA4Pro was now used for immunization of mice. Inoculation of this formulation induced anti-PspA4Pro IgG antibodies in serum and lungs. Analysis of binding of serum IgG to intact bacteria showed efficient binding to bacteria expressing PspA from clades 3, 4 and 5 (family 2), but no binding to bacteria expressing PspA from clades 1 and 2 (family 1) was observed. Both mucosal immunization with NP/NCMP PspA4Pro and subcutaneous injection of the protein elicited partial protection against intranasal lethal pneumococcal challenge with a serotype 3 strain expressing PspA from clade 5 (PspA5). Although similar survival levels were observed for mucosal immunization with NP/NCMP PspA4Pro and subcutaneous immunization with purified protein, NP/NCMP PspA4Pro induced earlier control of the infection. Conversely, neither immunization with NP/NCMP PspA4Pro nor subcutaneous immunization with purified protein reduced bacterial burden in the lungs after challenge with a serotype 19F strain expressing PspA from clade 1 (PspA1). Mucosal immunization with NP/NCMP PspA4Pro targeting the lungs is thus able to induce local and systemic antibodies, conferring protection only against a strain expressing PspA from the homologous family 2.

Current pneumococcal vaccines are composed of bacterial polysaccharides as antigens, plain or conjugated to carrier proteins. While efficacious against vaccine serotypes, epidemiologic data show an increasing incidence of infections caused by nonvaccine serotypes ofStreptococcus pneumoniae. The use of pneumococcal surface protein A (PspA) as a carrier protein in a conjugate vaccine could help prevent serotype replacement by increasing vaccine coverage and reducing selective pressure ofS. pneumoniaeserotypes. PspA is present in all pneumococcal strains, is highly immunogenic, and is known to induce protective antibodies. Based on its sequence, PspA has been classified into three families and six clades. A PspA fragment derived from family 2, clade 4 (PspA4Pro), was shown to generate antibodies with a broad range of cross-reactivity, across clades and families. Here, PspA4Pro was modified and conjugated to capsular polysaccharide serotype 14 (PS14). We investigated the impact of conjugation on the immune response induced to PspA4Pro and PS14. Mice immunized with the PS14-mPspA4Pro conjugate produced higher titers of anti-PS14 antibodies than the animals that received coadministered antigens. The conjugate induced antibodies with opsonophagocytic activity against PS14-carrying strains, as well as against a panel of strains bearing PspAs from five clades (encompassing families 1 and 2) bearing a non-PS14 serotype. Furthermore, mice immunized with PS14-mPspA4Pro were protected against nasal colonization with a nonrelatedS. pneumoniaestrain bearing PspA from clade 1, serotype 6B. These results demonstrate that the cross-reactivity mediated by PspA4Pro is retained following conjugation, supporting the use of PspA4 as a carrier protein in order to enhance pneumococcal vaccine coverage and encourage its further investigation as a candidate in future vaccine designs.

The capsular polysaccharide (PS) is the most important pneumococcal virulence factor and is currently used as antigen in all pneumococcal vaccines. Despite its physiological and epidemiological importance, meager studies have been devoted to improve PS production and understand its relationship with pneumococcal central metabolism. In this study, kinetics of growth and production of PS by Streptococcus pneumoniae serotype 14 (PS14) in batch and continuous cultivation were investigated. Strong cell lysis was observed in batch cultivation, while accumulation of organic acids and autolysis was avoided in continuous cultivation. In the continuous cultivation was possible to achieve higher concentration of biomass and PS14. Calculation of kinetic parameters demonstrated that PS14 is a cell-associated product. The coefficients for growth-associated stoichiometric true yield and maintenance were determined as 0.25 gglucose gbiomass−1 and 1.24 gglucose (gbiomass h)−1, respectively. The maximum productivity of PS14 released in the supernatant (PS14R) and cell-bound PS14 (PS14C) were obtained at a dilution rate of 0.8 h−1, respectively, 85 and 122 mg (gbiomass h)−1. Compared to batch fermentation, both PS14R and PS14C productivities were increased by about 300% in the continuous process. These findings demonstrate that continuous cultivation is a promising strategy for PS production to be used in pneumococcal vaccines.

High cell density cultivations of recombinant E. coli have been increasingly used for the production of heterologous proteins. However, it is a challenge to maintain these cultivations within the desired condi- tions, given that some variables such as dissolved oxygen concentration (DOC) and feed flow rate are difficult to control. This paper describes the software SUPERSYS_HCDC, a tool developed to supervise fed-batch cultures of rE. coli with biomass concentrations up to 150 gDCW/L and cell productivities up to 9 gDCW.L -1 .h -1 . The tool includes automatic control of the DOC by integrated action of the stirrer speed as well as of the air and oxygen flow rates; automatic start-up of the feed flow of fresh medium (system based on a neural network committee); and automatic slowdown of feeding when oxygen consumption exceeds the maximum capacity of the oxygen supply.

Streptococcus pneumoniae (pneumococcus) is a bacterium responsible for a wide spectrum of illnesses. The surface of the bacterium consists of three distinctive membranes: plasmatic, cellular and the polysaccharide (PS) capsule. PS capsules may mediate several biological processes, particularly invasive infections of human beings. Prevention against pneumococcal related illnesses can be provided by vaccines. There is a sound investment worldwide in the investigation of a proteic antigen as a possible alternative to pneumococcal vaccines based exclusively on PS. A few proteins which are part of the membrane of the pneumococcus seem to have antigen potential to be part of a vaccine, particularly the PspA. A vital aspect in the production of the intended conjugate pneumococcal vaccine is the efficient production (in industrial scale) of both, the chosen PS serotypes as well as the PspA protein. Growing recombinant Escherichia coli (rE. coli) in high-cell density cultures (HCDC) under a fed-batch regime requires a refined continuous control over various process variables where the on-line prediction of the feeding phase is of particular relevance and one of the focuses of this paper. The viability of an on-line monitoring software system, based on constructive neural networks (CoNN), for automatically detecting the time to start the fed-phase of a HCDC of rE. coli that contains a plasmid used for PspA expression is investigated. The paper describes the data and methodology used for training five different types of CoNNs, four of them suitable for classification tasks and one suitable for regression tasks, aiming at comparatively investigate both approaches. Results of software simulations implementing five CoNN algorithms as well as conventional neural networks (FFNN), decision trees (DT) and support vector machines (SVM) are also presented and discussed. A modified CasCor algorithm, implementing a data softening process, has shown to be an efficient candidate to be part of an on-line HCDC monitoring system for detecting the feeding phase of the HCDC process.

Sugarcane bagasse is a residue with great potential as a feedstock for second-generation ethanol production. One of the approaches studied for making use of this material is the utilization of enzymes to hydrolyze the cell wall carbohydrates and generate fermentable sugars. These enzymes can be produced by cultivation of filamentous fungi or bacteria; however, the high production cost still represents a bottleneck to second-generation ethanol production. Expression of recombinant hydrolases through a co-culture strategy could be an interesting alternative for producing a recombinant cocktail at high levels of productivity that is tailor-made for each material to be hydrolyzed. In this study we evaluate the production of hydrolases by co-culturing two recombinant Escherichia coli , each expressing a specific hydrolase, β-1,3-1,4-glucanase or β-1,4-xylanase, both isolated from Bacillus subtilis . The cultures were conducted in bioreactors in batch and fed-batch mode in order to reach high cell densities. Co-culture in batch cultivation reached a dry cell weight of 10.4 g/L and volumetric activities of 31.96 U/mL and 11.89 U/mL for xylanase and endoglucanase, respectively. Fed-batch cultivation reached a dry cell weight of 60 g/L and the volumetric activities of xylanase and endoglucanase were respectively up to 5 and 1.3 times higher than those in batch mode. A competition assay indicates that no clone predominates over the other during cultivation. These results suggest that co-culture is a potential technique for producing recombinant hydrolase cocktails at lower cost than those associated with the production of a single culture.

Streptococcus pneumoniae is the main cause of pneumonia, meningitis, and other conditions that kill thousands of children every year worldwide. The replacement of pneumococcal serotypes among the vaccinated population has evidenced the need for new vaccines with broader coverage and driven the research for protein-based vaccines. Pneumococcal surface protein A (PspA) protects S. pneumoniae from the bactericidal effect of human apolactoferrin and prevents complement deposition. Several studies indicate that PspA is a very promising target for novel vaccine formulations. Here we describe a production and purification process for an untagged recombinant fragment of PspA from clade 4 (PspA4Pro), which has been shown to be cross-reactive with several PspA variants. PspA4Pro was obtained using lactose as inducer in Phytone auto-induction batch or glycerol limited fed-batch in 5-L bioreactor. The purification process includes two novel steps: (i) clarification using a cationic detergent to precipitate contaminant proteins, nucleic acids, and other negatively charged molecules as the lipopolysaccharide, which is the major endotoxin; and (ii) cryoprecipitation that eliminates aggregates and contaminants, which precipitate at −20 °C and pH 4.0, leaving PspA4Pro in the supernatant. The final process consisted of cell rupture in a continuous high-pressure homogenizer, clarification, anion exchange chromatography, cryoprecipitation, and cation exchange chromatography. This process avoided costly tag removal steps and recovered 35.3 ± 2.5% of PspA4Pro with 97.8 ± 0.36% purity and reduced endotoxin concentration by >99.9%. Circular dichroism and lactoferrin binding assay showed that PspA4Pro secondary structure and biological activity were preserved after purification and remained stable in a wide range of temperatures and pH values.

Streptococcus pneumoniae is a major cause of mortality in underdeveloped countries, where more than one million people die from pneumococcal disease every year. Vaccines are the most efficient method for preventing the infection and are based on the capsular polysaccharide (PS) protection. The serotype 14 is the most frequent in pediatric infections worldwide. This study aimed to establish a quantification protocol for PS present in culture broth samples of S. pneumoniae serotype 14 (PS14) and use this protocol for selection of the best PS14 producer strain. Phenol-sulfuric, HPSEC, competitive ELISA, and sandwich ELISA methods were tested for PS14 quantification. Sandwich ELISA was the method with the best reproducibility and sensitivity and the least susceptible to interferences. The quantification limit and detection limit of this method were 0.99 and 0.57 ng/mL, respectively. Statistical analysis was performed to calculate the coefficient of variation (CV) intraassay (1-3% intraplate and 2-6% interplate) and interassay (11-15%) and the reproducibility in different days (CV

The performance of an in-situ capacitance sensor for on-line monitoring of biomass concentration was evaluated for some of the most important microorganisms in the biotechnology industry: Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris and Bacillus megaterium. A total of 33 batch and fed-batch cultures were carried out in a bench-scale bioreactor and biomass formation trends were followed by dielectric measurements during the growth phase as well as the induction phase, for 5 recombinant E. coli strains. Permittivity measurements and viable cellular concentrations presented a linear correlation for all the studied conditions. In addition, the permittivity signal was further used for inference of the cellular growth rate. The estimated specific growth rates mirrored the main trends of the metabolic states of the different cells and they can be further used for setting-up control strategies in fed-batch cultures.

Pneumococcal surface protein A (PspA) is essential for Streptococcus pneumoniae virulence and its use either as a novel pneumococcal vaccine or as carrier in a conjugate vaccine would improve the protection and the coverage of the vaccine. Within this context, the development of scalable production and purification processes of His-tagged recombinant fragment of PspA from clade 3 (rfPspA3) in Escherichia coli BL21(DE3) was proposed. Fed-batch production was performed using chemically defined medium with glucose or glycerol as carbon source. Although the use of glycerol led to lower acetate production, the concentration of cells were similar at the end of both fed-batches, reaching high cell density of E. coli (62 g dry cell weight/L), and the rfPspA3 production was higher with glucose (3.48 g/L) than with glycerol (2.97 g/L). A study of downstream process was also carried out, including cell disruption and clarification steps. Normally, the first chromatography step for purification of His-tagged proteins is metal affinity. However, the purification design using anion exchange followed by metal affinity gave better results for rfPspA3 than the opposite sequence. Performing this new design of chromatography steps, rfPspA3 was obtained with 95.5% and 75.9% purity, respectively, from glucose and glycerol culture. Finally, after cation exchange chromatography, rfPspA3 purity reached 96.5% and 90.6%, respectively, from glucose and glycerol culture, and the protein was shown to have the expected alpha-helix secondary structure.

One of the most important events in fed-batch fermentations is the definition of the moment to start the feeding. This paper presents a methodology for a rational selection of the architecture of an artificial intelligence (AI) system, based on a neural network committee (NNC), which identifies the end of the batch phase. The AI system was successfully used during high cell density cultivations of recombinant Escherichia coli. The AI algorithm was validated for different systems, expressing three antigens to be used in human and animal vaccines: fragments of surface proteins of Streptococcus pneumoniae (PspA), clades 1 and 3, and of Erysipelothrix rhusiopathiae (SpaA). Standard feed-forward neural networks (NNs), with a single hidden layer, were the basis for the NNC. The NN architecture with best performance had the following inputs: stirrer speed, inlet air, and oxygen flow rates, carbon dioxide evolution rate, and CO2 molar fraction in the exhaust gas.

New conjugated vaccines against Streptococcus pneumoniae are being developed using pneumococcal surface proteins as carriers. The pneumococcal surface protein A (PspA) was selected as carrier because it is indispensable for virulence of S. pneumoniae. The PspA can be classified into 3 families according to the homology of protein sequences, within each family there is immunological cross-reactivity and PspA from family 1 or 2 are present in 99% of strains associated with pneumococcal invasive disease. Hence, the purpose of this work was to develop an industrial production and purification process of His-tagged recombinant fragment of PspA in E. coli BL21 (DE3), rfPspA245 from family 1. Fed-batch cultivations in 5-L bioreactors with defined medium were carried out using glycerol as carbon source. It was obtained circa 60 g/L of dry cell weight and 3.0 g/L of rfPspA. Cells were disrupted with 96.7% of efficiency by high pressure continuous homogenizer. The clarification step was done by centrifugation. The results of chromatographic steps were analyzed by densitometry of SDS-PAGE protein bands. Using the chromatographic sequence anion exchange (Q-Sepharose) followed by metal affinity (IMAC-Sepharose), the rfPspA245 was obtained with 67% and 97% of purity respectively for each step and final recovery of 23%. In conclusion, the purification process was developed and rfPspA245 was obtained with high purity, but the recovery should still be improved. © 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of Prof. Ray Spier

Mucosal immunization with a killed whole-cell pneumococcal vaccine, given with enterotoxin-related adjuvants, has been shown to confer multi-serotype protection against colonization of the nasopharynx and middle ear in mice. However, because novel mucosal immunization strategies may be difficult to implement, here we evaluated subcutaneous injection. Strain RM200 was engineered to be capsule-negative, autolysin-negative, and to express a non-toxic mutant pneumolysoid. Liter-scale and 60-l Good Manufacturing Practice (GMP) cultures were grown in bovine-free soy-based medium, killed with chloroform or beta-propiolactone, and injected into C57Bl/6 mice without or with aluminum adjuvant. The adjuvant Al(OH)(3) strongly increased responses, particularly if pre-treated with phosphate. Protection was found in several tested model infections: nasal colonization with a serotype 6B strain and fatal aspiration-sepsis with strains of serotype 3 and 5. Protection against colonization was mechanistically dependent on the presence of CD4+ T cells at the time of challenge; in contrast, in the type 3 aspiration-sepsis model, CD4+ T cells were not required for protection at the time of challenge, suggesting that antibody alone was sufficient to protect against death in this model. Rabbits receiving sequential intramuscular injections in a pilot toxicity study displayed local reactogenicity at injection sites but no clinical signs. The rabbit antiserum thus produced was active in an in vitro phagocytic killing assay and passively protected mice in the type 3 aspiration-sepsis model. Approval is being sought for human trials of this vaccine.

The high cost of the available pneumococcal conjugated vaccines has been an obstacle in implementing vaccination programs for children in developing countries. As an alternative, Malley et al. proposed a vaccine consisting of inactivated whole-cells of unencapsulated S. pneumoniae, which provides serotype-independent protection and involves lower production costs. Although the pneumococcus has been extensively studied, little research has focused on its large-scale culture, thus implying a lack of knowledge of process parameters, which in turn are essential for its successful industrial production. The strain Rx1Al- eryR was originally cultured in Todd-Hewitt medium (THY), which is normally used for pneumococcus isolation, but is unsuitable for human vaccine preparations. The purposes of this study were to compare the strains Rx1Al- eryR and kanR, develop a new medium, and generate new data parameters for scaling-up the process. In static flasks, cell densities were higher for eryR than kanR. In contrast, the optical density (OD) of the former decreased immediately after reaching the stationary phase, and the OD of the latter remained stable. The strain Rx1Al- kanR was cultivated in bioreactors with medium based on either acid-hydrolyzed casein (AHC) or enzymatically hydrolyzed soybean meal (EHS). Biomass production in EHS was 2.5 times higher than in AHC, and about ten times higher than in THY. The process developed for growing the strain Rx1Al- kanR in pH-controlled bioreactors was shown to be satisfactory to this fastidious bacterium. The new culture conditions using this animal-free medium may allow the production of the pneumococcal whole-cell vaccine.

The currently available anti-pneumococcal vaccines are based on capsular polysaccharide (PS), plain or conjugated to a carrier protein. Conjugated vaccines are expensive products, especially in the case of pneumococcus, in which reasonable coverage requires from 7 to 13 serotypes. To obtain increased coverage with fewer components, we evaluated the immunogenicity of the pneumococcal surface protein A (PspA), conjugated to capsular polysaccharide serotype 23F, aiming at induction of an immune response against both components. Mice immunized with PS23F-rPspA1 conjugate produced antibodies against both PS and rPspA1, comparable or slightly higher than that obtained by free PS. The immunized animals challenged with a lethal dose of a virulent strain bearing a homologous PspA, showed that the PS23F-rPspA1 conjugate induced higher survival than rPspA1 alone or in combination with PS. This increased protection was shown to correlate with the enhanced capacity of the antibodies to bind to the pneumococcal surface and to induce complement deposition. Our results indicate that the use of PS-PspA conjugates may be a way to increase coverage against pneumococci with fewer components.

Streptococcus pneumoniae is a human pathogen largely transmitted by aerosols. Vaccines are the main strategy against this pathogen, and the capsular polysaccharide (PS) is its major antigen. S. pneumoniae serotype 1 is associated with large outbreaks and epidemics of invasive diseases. The aims of this work were to screen serotype 1 strains to identify the best PS1 producer, evaluate three peptones for PS1 production, investigate the effects of culture medium components using a design of experiments (DoE), a statistic tool for optimization, and propose a new medium/cultivation strategy. After flask cultivation of nine strains, two that produced high PS1 and biomass values were chosen for further evaluation in the bioreactor, and ST595/01 was chosen as the best PS1 producer strain. Among the peptones tested (Casamino acids, Soytone, and Phytone), the highest PS1 production (298 mg/L) was reached with Phytone. Next, DoE (2(4-1)) was performed to evaluate the effects of yeast extract (YE), Phytone, L-asparagine (Asn), and L-glutamine (Gln), yielding the following results: Phytone presented positive effects (p

Pneumococcal infections impose a large burden of disease on the human population, mainly in developing countries, and the current pneumococcal vaccines offer serotype-specific protection, but do not cover all pathogenic strains, leaving populations vulnerable to disease caused by non-vaccine serotypes. The pneumococcal whole cell vaccine is a low-cost strategy based on non-capsular antigens common to all strains, inducing serotype-independent immunity. Therefore, we developed the process for the cGMP production of this cellular vaccine. Initially, three engineering runs and two cGMP runs were performed in 60-L bioreactors, demonstrating the consistency of the production process, as evaluated by the growth curves, glucose consumption and metabolite formation (lactate and acetate). Cell recovery by tangential filtration was 92 ± 13 %. We optimized the conditions for beta-propiolactone (BPL) inactivation of the bacterial suspensions, establishing a maximum cell density of OD600 between 27 and 30, with a BPL concentration of 1:4000 (v/v) at 150 rpm and 4 °C for 30 h. BPL was hydrolyzed by heating for 2h at 37 °C. The criteria and methods for quality control were defined using the engineering runs and the cGMP Lots passed all specifications. cGMP vaccine Lots displayed high potency, inducing between 80 and 90% survival in immunized mice when challenged with virulent pneumococci. Sera from mice immunized with the cGMP Lots recognized several pneumococcal proteins in the extract of encapsulated strains by Western blot. The cGMP whole cell antigen bulk and whole cell vaccine product lots were shown to be stable for up to 12 and 18 months, respectively, based upon survival assays following i.p. challenge. Our results show the consistency and stability of the cGMP whole cell pneumococcal vaccine lots and demonstrate the feasibility of production in a developing country setting.

Despite the substantial beneficial effects of incorporating the 7-valent pneumococcal conjugate vaccine (PCV7) into immunization programs, serotype replacement has been observed after its widespread use. As there are many serotypes currently documented, the use of a conjugate vaccine relying on protective pneumococcal proteins as active carriers is a promising alternative to expand PCV coverage. In this study, capsular polysaccharide serotype 6B (PS6B) and recombinant pneumococcal surface protein A (rPspA), a well-known protective antigen from Streptococcus pneumoniae , were covalently attached by two conjugation methods. The conjugation methodology developed by our laboratory, employing 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) as an activating agent through carboxamide formation, was compared with reductive amination, a classical methodology. DMT-MM-mediated conjugation was shown to be more efficient in coupling PS6B to rPspA clade 1 (rPspA1): 55.0% of PS6B was in the conjugate fraction, whereas 24% was observed in the conjugate fraction with reductive amination. The influence of the conjugation process on the rPspA1 structure was assessed by circular dichroism. According to our results, both conjugation processes reduced the alpha-helical content of rPspA; reduction was more pronounced when the reaction between the polysaccharide capsule and rPspA1 was promoted between the carboxyl groups than the amine groups (46% and 13%, respectively). Regarding the immune response, both conjugates induced functional anti-rPspA1 and anti-PS6B antibodies. These results suggest that the secondary structure of PspA1, as well as its reactive groups (amine or carboxyl) involved in the linkage to PS6B, may not play an important role in eliciting a protective immune response to the antigens.

This work proposes an innovative methodology to control high density fed-batch cultures of E. coli, based on measurements of the concentration of dissolved oxygen and on estimations of the cellular specific growth rate (µ), of the yield of biomass/limiting substrate (Y (xs)) and of the maintenance coefficient (m). The underlying idea is to allow cells to grow according to their metabolic capacity, without the constraints inherent to pre-set growth rates. Cellular concentration was assessed on-line through a capacitance probe. Three configurations of the control system were compared: (1) pre-set value for the three control parameters; (2) continuously updating µ; (3) updating µ, Y (xs) and m. Implementation of an efficient noise filter for the signal of the capacitance probe was essential for a good performance of the control system. The third control strategy, within the framework of an adaptive model-based control, led to the best results, with biomass productivity reaching 9.2 g(DCW)/L/h.

Polysaccharide-protein conjugates are so far the current antigens used for pneumococcal vaccines for children under 2 years of age. In this study, pneumococcal surface protein A (PspA) was used as a carrier protein for pneumococcal capsular polysaccharide serotype 14 as an alternative to broaden the vaccine coverage. PspA was modified by reductive amination with formaldehyde in order to improve the specificity of the reaction between protein and polysaccharide, inhibiting polymerization and the gel formation reaction. In the synthesis process, the currently used activator, 1-[3-(dimethylamine)propyl]-3-ethylcarbodiimide hydrochloride (EDAC) was substituted for 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). BALB/c mice were immunized with either the PS14-mPspA conjugate or the co-administered components in a three dose regimen and sera from the immunized animals were assayed for immunity induced against both antigens: PS14 and mPspA. Modification of more than 70% of lysine residues from PspA (mPspA) did not interfere in the immune response as evaluated by the anti-PspA titer and C3 complement deposition assay. Sera of mice immunized with conjugated PS14-mPspA showed similar IgG titers, avidity and isotype profile as compared to controls immunized with PspA or mPspA alone. The complement deposition was higher in the sera of mice immunized with the conjugate vaccine and the opsonophagocytic activity was similar for both sera. Conjugation improved the immune response against PS14. The anti PS14 IgG titer was higher in sera of mice immunized with the conjugate than with co-administered antigens and presented an increased avidity index, induction of a predominant IgG1 isotype and increased complement deposition on a bacteria with a surface serotype 14. These results strongly support the use of PspA as carrier in a conjugate vaccine where both components act as antigens.

Streptococcus pneumoniaeis a bacterial pathogen that causes many life-threatening diseases and an effective vaccine against this pa-thogen is still subject of research. These bacteria grow with low carbon dioxide production, which hinders the application of exhaust gas composition for on-line process monitoring. This work investigates the proposal of a committee of neural networks for identifying Streptococcus pneumoniaegrowth phases, to be used for on-line state inference. The committee results as well as the accuracy for predicting the culture phases are compared to the results of a unique neural network, for different input variables. The best configuration for the software was: a committee of three NN trained with two input attributes (optical density and mass of alkali solution), 200 epochs of training and log sigmoid as the activation function in the hidden layer as well as in the output layer.

Aim: An approach to increase Streptococcus pneumoniae capsular polysaccharide (CPS) in the culture medium during fed-batch cultivation in bioreactor. Methods and Results: Streptococcus pneumoniae serotype 23F was cultivated in a 5-l bioreactor with nitrogen-sparging and followed by addition of air in the stationary phase. The amount of CPS released in the supernatant progressively increased under air sparging. The profile of cellular viability and optical density was similar in both cultures. Immunoelectron microscopy showed that the amount of tightly cell-bound CPS was higher in bacteria cultivated under nitrogen than under air. Conclusions: The stress caused by the addition of air at the stationary phase promoted a large increase of free CPS into the medium, as a consequence of the morphologic change in the capsule. Significance and Impact of the Study: The use of air in the stationary phase of the culture would greatly simplify the subsequent downstream process, allowing CPS purification from the supernatant. The direct consequence of this process improvement is the reduction of vaccine production costs.

Streptococcus pneumoniae is a pathogenic encapsulated bacterium, which causes pneumonia, bacteraemia and meningitis. Capsular polysaccharide conjugated to a carrier protein has been widely used as a vaccine antigen. Serotype 23F is one of the prevalent worldwide pneumococci. A simple and efficient method for capsular polysaccharide serotype 23F purification that can easily be scaled-up was developed. This method consisted of using culture broth obtained by tangential microfiltration through a 0.22 microm membrane, broth microfiltrate concentration by tangential ultrafiltration in a 30 kDa spiral membrane, fractional ethanol precipitation (28-60%), nuclease and proteinase treatment, and concentration/diafiltration in a 30 kDa cassette membrane. The final polysaccharide recovery was 89%. The final protein and nucleotide contamination was 1.5% (w/w) and 0.3% (w/w) respectively. The final pure polysaccharide meets the requirements of the World Health Organization and residual proteinase was not found in the final product.