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Difficulty in obtaining large quantities of Mycobacterium tuberculosis (MTB) proteins remains a major obstacle in the development of subunit vaccines and diagnostic reagents for tuberculosis. A major reason is because Escherichia coli has not proven to be an optimal host for the expression of MTB genes. In this article, we used the yeast Pichia pastoris to express high levels of CFP32, a culture filtrate protein restricted to the MTB complex and a potential target antigen for serodiagnosis of tuberculosis in patients. Using shaker flasks, we generated a P. pastoris clone expressing CFP32 as a secreted protein fused to the myc- (His)6 tag, at a yield of 0.5 g of purified protein per liter of culture. Recombinant CFP32 (rCFP32) produced in P. pastoris has a molecular weight of 35 kDa, which is slightly higher than that of the native protein. We identified putative acylation and glycosylation sites in the CFP32 amino acid sequence that suggested posttranslational modifications may contribute to the size difference. The NH2-terminal peptide sequencing of rCFP32 showed that the signal peptide alpha factor is correctly excised. In addition, rCFP32 reacted with the sera of patients with tuberculosis. These data are the first to show that P. pastoris is a suitable host for high-yield production of good quality mycobacterium antigens, and especially culture filtrate proteins that have vaccine and diagnostic potential.

We herein report the production in the methylotrophic yeast Pichia pastoris of a recombinant scFv form of monoclonal antibody 107 [MAb 107]. This antibody is directed to the leukocyte adhesion molecule CR3 (CD11b/CD18) and is specific of the CD11bA domain. MAb 107 is a ligand mimic of CR3 that blocks the adhesion of leukocyte and their transendothelial migration (diapedesis), a feature that confers this MAb a potential anti inflammatory activity. Expression of scFv 107 as a myc-(His) 6 secreted fusion protein was achieved in the yeast P. pastoris using plasmid pICZαB. A spontaneous specific cleavage of the myc-His tag was consistently observed regardless of the culture conditions and the addition of different concentrations of casaminoacids in the medium. Loss of the myc-His tag did not affect the binding activity of scFv 107. This loss is due either to a specific proteolysis or to a mechanical cleavage. Optimization of the production of scFv 107 in shake flasks was carried out using an L16 array Taguchi design. A level of purified scFv-myc-His fusion protein estimated at 40 mg/L was reached at pH 6 and a temperature of 27 °C. The production of large amounts of recombinant scFv form of MAb 107 is essential for further molecular studies of the interactions between CR3 and its ligands, mainly those mediated by the CD11b A domain. It will also facilitate the investigation of its anti inflammatory activity in vivo.

We herein report the fabrication and characterisation of a novel impedimetric immunosensor based on an electrolyte–insulator–semiconductor (EIS) structure. It is a silicon nitride/aminosilane/glutaraldehyde/antibody biosensor specifically designed for the detection of antigens. This immunosensor was fabricated following the Self-Assembled Monolayers (SAMs) method, followed by glutaraldehyde cross linker and anti-rabbit IgG immobilization. The high coverage area of the silane monolayer on silicon nitride surface was estimated with impedance spectroscopy technique and the molecular structure with Fourier-transform infrared (FTIR) technique. The binding between antibody and antigen (Rabbit IgG) was monitored by measuring the resistance variation of the grafted layer. The developed immunosensor has a limit detection of 50 ng/ml of antigen.

Taguchi’s methods were used for the design of an experimental strategy aimed at optimizing cell density and monoclonal antibody (mAb) production from a spinner flask hybridoma culture. 23G11 is an antibody to the human leukocyte adhesion molecule, CR3 or β 2 integrin (CD11b/CD18). It recognizes specifically the A-domain of the α subunit CD11b. Anti β 2 integrin monoclonal antibodies hold a great potential for preventing inflammation mediated tissue injuries. An L8 orthogonal experimental design was used to investigate four different culture components: stirring speed, nature of serum, concentration of serum and nature of media (RPMI 1640 or RPMI 1640 supplemented with glucose and glutamine). The experiments were conducted using two levels for each factor studied and a direct ELISA test was used to estimate the level of antibody production. Statistical analysis of the collected data pointed to the stirring speed and serum concentration, and the interaction between these parameters, as the components that affected cell growth. Antibody production was affected by these factors and by the nature of medium but also by the following two interactions: stirring speed/nature of serum and stirring speed/concentration of serum. This study emphasizes the value of using Taguchi’s methods as a basis for optimization of mAb production from a hybridoma culture, in cost effective and significantly less labor intensive ways.

Escherichia coli is the most extensively used host for the production of recombinant proteins. However, most of the eukaryotic proteins are typically obtained as insoluble, misfolded inclusion bodies that need solubilization and refolding. To achieve high-level expression of soluble recombinant human interferon alpha (rhIFNalpha) in E. coli, we have first constructed a recombinant expression plasmid (pGEX-hIFNalpha2b), in which we merged the hIFNalpha2b cDNA with the glutathione S-transferase (GST) coding sequence downstream of the tac-inducible promoter. Using this plasmid, we have achieved 70% expression of soluble rhIFNalpha2b as a GST fusion protein using E. coli BL21 strain, under optimized environmental factors such as culture growth temperature and inducer (IPTG) concentration. However, release of the IFN moiety from the fusion protein by thrombin digestion was not optimal. Therefore, we have engineered the expression cassette to optimize the amino acid sequence at the GST-IFN junction and to introduce E. coli preferred codon within the thrombin cleavage site. We have used the engineered plasmid (pGEX-Delta-hIFNalpha2b) and the modified E. coli trxB(-)/gor(-) (Origami) strain to overcome the problem of removing the GST moiety while expressing soluble rhIFNalpha2b. Our results show the production of soluble and functional rhIFNalpha2b at a yield of 100 mg/l, without optimization of any step of the process. The specific biological activity of the purified soluble rhIFNalpha2b was equal to 2.0 x 10(8) IU/mg when compared with the WHO IFNalpha standard. Our data are the first to show that high yield production of soluble and functional rhIFNalpha2b tagged with GST can be achieved in E. coli.

Site-directed mutagenesis (SDM) is a powerful tool for exploring protein structure and function, and several procedures adjusted to specific purposes are still being developed. Herein we describe a straightforward and efficient method with versatile applications for introducing site-specific alterations in any deoxyribonucleic acid (DNA) sequence cloned in a plasmidic expression vector. In this polymerase chain reaction (PCR)-based SDM method, forward and reverse primers are used to amplify the plasmid containing the sequence of interest. The primers are designed so that the desired modifications are introduced at the 5' end of one of the primers, whereas the other primer starts with the nucleotide at position (-1) of the one to be modified. The PCR is carried out using Pfu DNA polymerase. The blunt-ended PCR-generated DNA fragment is self-ligated and used to transform Escherichia coli. Mutant clones are screened by colony hybridization using the mutagenic primer as probe and the presence of the mutation is confirmed by direct DNA sequencing. This procedure was used efficiently to introduce substitutions, deletions, and insertions in the DNA sequences coding for a recombinant form (scFv) of antibody 107 specific of the human CR3 molecule, the rat alpha integrin CD11b A-domain and the human CD8beta cloned in pPICZalphaB, pGEX-2T, and CDM8 expression vectors, respectively.

In this work we employ PEGylated polyethyleneimine (pPEI) o act both as an affinity ligand, to increase the selectivity of the ystem, and as a pDNA condensation agent. In this way we were ble to obtain plasmid polyplexes with a 100% yield without NA or protein contamination, after two ATPS extractions from lkaline lysates. In the first one a PEG 600—ammonium sulhate system, already described, was used and in the second one t was employed a PEG 3350—Dextran 110 system containing PEI. The isolation of polyplexes was carried out by ultrafiltraion. Although a substantial removal of Dextran and PEG was chieved the yield in polyplexes was very low (5–10%). This as due to binding of the polyplexes to the polyethersulphone embrane used. Further studies are being carried to optimize he ultrafiltration step. These results open the possibility of simultaneously purifyng and condensing the plasmid with the delivery vehicle for herapeutic applications and achieving the integration of two mportant steps on pharmaceutical plasmids production.