Production of anti-peptide antisera

Functional and in silico Characterization of Neutralizing Interactions Between Antibodies and the Foot-and-Mouth Disease Virus Immunodominant Antigenic Site

Molecular knowledge of virus–antibody interactions is essential for the development of better vaccines and for a timely assessment of the spread and severity of epidemics. For foot-and-mouth disease virus (FMDV) research, in particular, computational methods for antigen–antibody (Ag–Ab) interaction, and cross-antigenicity characterization and prediction are critical to design engineered vaccines with robust, long-lasting, and wider response against different strains. We integrated existing structural modeling and prediction algorithms to study the surface properties of FMDV Ags and Abs and their interaction. First, we explored four modeling and two Ag–Ab docking methods and implemented a computational pipeline based on a reference Ag–Ab structure for FMDV of serotype C, to be used as a source protocol for the study of unknown interaction pairs of Ag–Ab. Next, we obtained the variable region sequence of two monoclonal IgM and IgG antibodies that recognize and neutralize antigenic site A (AgSA) epitopes from South America serotype A FMDV and developed two peptide ELISAs for their fine epitope mapping. Then, we applied the previous Ag–Ab molecular structure modeling and docking protocol further scored by functional peptide ELISA data. This work highlights a possible different behavior in the immune response of IgG and IgM Ab isotypes. The present method yielded reliable Ab models with differential paratopes and Ag interaction topologies in concordance with their isotype classes. Moreover, it demonstrates the applicability of computational prediction techniques to the interaction phenomena between the FMDV immunodominant AgSA and Abs, and points out their potential utility as a metric for virus-related, massive Ab repertoire analysis or as a starting point for recombinant vaccine design.

Dissecting antibodies with regards to linear and conformational epitopes

An important issue for the performance and specificity of an antibody is the nature of the binding to its protein target, including if the recognition involves linear or conformational epitopes. Here, we dissect polyclonal sera by creating epitope-specific antibody fractions using a combination of epitope mapping and an affinity capture approach involving both synthesized peptides and recombinant protein fragments. This allowed us to study the relative amounts of antibodies to linear and conformational epitopes in the polyclonal sera as well as the ability of each antibody-fraction to detect its target protein in Western blot assays. The majority of the analyzed polyclonal sera were found to have most of the target-specific antibodies directed towards linear epitopes and these were in many cases giving Western blot bands of correct molecular weight. In contrast, many of the antibodies towards conformational epitopes did not bind their target proteins in the Western blot assays. The results from this work have given us insights regarding the nature of the antibody response generated by immunization with recombinant protein fragments and has demonstrated the advantage of using antibodies recognizing linear epitopes for immunoassay involving wholly or partially denatured protein targets.

Construction of HCV-polytope vaccine candidates harbouring immune-enhancer sequences and primary evaluation of their immunogenicity in BALB/c mice

An efficient vaccine against hepatitis-C virus (HCV) infection requires vigorous and focused CD8(+) T-cell responses against viral antigens. Due to immunosuppressive effect of HCV antigens, polytope vaccines comprising the minimal CD8(+)CTL epitopes are of peculiar concern. Herein, to provide information for construction of efficient HCV polytope vaccine candidates, one H-2D(d) (E2(405-414):E(2)) and two HLA-A*0201 (E1(363-372):E(1) and Core(35-44):C)-restricted CD8(+) T-cell epitopes of HCV were selected. By employing number of in silico analyses, the E(2)E(1)C linear format was predicted as optimum epitope consecution and after amplification by SOEing-PCR, the corresponding DNA sequence was cloned in pcDNA3.1+ vector. To further evaluate the role of immune-enhancer elements, a universal T-helper epitope (PADRE), endoplasmic reticulum signal sequence (ERss) and hepatitis-B surface-antigen (HBsAg) gene were fused separately or in combination to the E(2)E(1)C minigene. In vitro analyses of polytopes by different DNA/protein-based assays demonstrated proper transcription/expression of constructs in transfected cells. Measurement of the HBsAg-mediated particle secretion by ELISA indicated lack of secretion in the related polytopes. Results of delayed-type hypersensitivity (DTH) as a preliminary in vivo analysis, and confirmatory ELISPOT assays showed the proper processing and presentation of H-2D(d)-restricted-E(2) epitope and approved the enhancing effect of PADRE and ERss sequences but not HBsAg for the immune responses against E(2) in immunized BALB/c mice. Our results pointed to the value of in silico predictions and application of immune-enhancer elements as well as DTH analysis for design and primary in vivo evaluation of HCV polytopes, prior to costly transgenic studies on immunogenicity of HLA-A*0201 epitopes.