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2014
|
vol. 61
|
issue 3
561-572
EN
Recombinant subunit vaccines based on hemagglutinin proteins produced in bacteria (bacterial HAs) are promising candidates for enhancing the supply of vaccines against influenza, especially for a pandemic. Over 20 years after the failure to obtain the antigen with native HA characteristics in the early 1980’s, there are increasing data on successful production of HA proteins in bacteria. The vast majority of bacterial HAs have been based on the HA1 subunit of HA expressed separately or as a component of conjugate vaccines, but those based on the ectodomain and the HA2 subunit have also been reported. The most of HAs have been efficiently expressed as insoluble aggregates called inclusion bodies. Refolded and purified proteins were extensively studied for structure, the ability to bind to sialic acid-containing receptors, antigenicity, immunogenicity and efficacy. The results from these studies contradict the view that glycosylation determines the correct structure of the hemagglutinin, as they proved that bacterial HAs can be valuable vaccine antigens when appropriate folding and purification methods are applied to rationally designed proteins. The best evidence for success in bacterial production of protective HA is that vaccines based on proprietary Toll-like Receptor (VaxInnate) and bacteriophage Qβ-VLPs (Cytos Biotechnology) technologies have been advanced to clinical studies.
EN
Gram-positive and nonpathogenic lactic acid bacteria (LAB) are considered to be promising candidates for the development of new, safe systems of heterologous protein expression. Recombinant LAB has been shown to induce specific local and systemic immune response against selected pathogens, and could be a good alternative to classical attenuated carriers. The main goal of our study was to express the avian influenza haemagglutinin (H5) and chicken interleukin 2 (chIL-2) in Lactococcus lactis. Results of this study were anticipated to lead to construction of lactococcal strain(s) with potential vaccine properties against the avian influenza A (H5N1) virus. Expression of the cloned H5 gene, its His-tagged variant and chIL-2 gene, under the control of the ptcB gene promoter was attested by RT-PCR on transcriptional level and Western or dot blot analysis on translational level, demonstrating that system can be an attractive solution for production of heterologous proteins. The results of the preliminary animal trial conducted in mice are a promising step toward development of a vaccine against avian bird flu using Lactococcus lactis cells as antigen carriers.
EN
Hemagglutinin (HA), as a major surface antigen of influenza virus, is widely used as a target for production of neutralizing antibodies. Monoclonal antibody, mAb6-9-1, directed against HA of highly pathogenic avian influenza virus A/swan/Poland/305-135V08/2006(H5N1) was purified from mouse hybridoma cells culture and characterized. The antigenic specificity of mAb6-9-1 was verified by testing its cross-reactivity with several variants of HA. The mimotopes recognized by mAb6-9-1 were selected from two types of phage display peptide libraries. The comparative structural model of the HA variant used for antibody generation was developed to further facilitate epitope mapping. Based on the sequences of the affinity- selected polypeptides and the structural model of HA the epitope was located to the region near the receptor binding site (RBS). Such localization of the epitope recognized by mAb6-9-1 is in concordance with its moderate hemagglutination inhibiting activity and its antigenic specificity. Additionally, total RNA isolated from the hybridoma cell line secreting mAb6-9-1 was used for obtaining two variants of cDNA encoding recombinant single-chain variable fragment (scFv) antibody. To ensure high production level and solubility in bacterial expression system, the scFv fragments were produced as chimeric proteins in fusion with thioredoxin or displayed on a phage surface after cloning into the phagemid vector. Specificity and affinity of the recombinant soluble and phage-bound scFv were assayed by suitable variants of ELISA test. The observed differences in specificity were discussed.
EN
The A/swan/Poland/305-135V08/2006 (H5N1-subtype) hemagglutinin (HA) gene was cloned and expressed in yeast Pichia pastoris (P. pastoris). The HA cDNA lacking the C-terminal transmembrane anchor-coding sequence was fused to an α-factor leader peptide and placed under control of the methanol-inducible P. pastoris alcohol oxidase 1 (AOX1) promoter. Two P. pastoris strains: SMD 1168 and KM 71 were used for protein expression. Recombinant HA protein was secreted into the culture medium reaching an approximately 15 mg/L (KM 71 strain). Fusion protein with a His6 tag was purified to homogeneity in one step affinity chromatography. SDS-PAGE and MS/MS analysis indicated that the protein is cleaved into HA1 and HA2 domains linked by a disulfide bond. Analysis of the N-linked glycans revealed that the overexpressed HA is fully glycosylated at the same sites as the native HA in the vaccine strain. Immunological activity of the hemagglutinin protein was tested in mice, where rHA elicited a high immune response.
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