Epitope-vaccine induces high levels of ELDKWA-epitope-specific neutralizing antibody

Abstract

Based on the fact that mAb 2F5 recognizing ELDKWA-epitope on the C-domain of HIV-1 gp41 has significant neutralization potency against 90% of the investigated viruses of African, Asian, American and European strains, we attempted to characterise immunogenicity of the ELDKWA-epitope on an epitope-vaccine, and to produce ELDKWA-epitope-specific monoclonal antibodies (mAb) induced by the epitope-vaccine. The C-domain peptide (P2) and the ELDKWA-tetramer peptide [C-(ELDKWAG)₄] were conjugated with BSA or P24-EC (GPKEPFRDYVDRFYK, a peptide of HIV-1 gag-protein P24, proved to be a good carrier peptide to induce an immune response to the hapten on the conjugates[¹⁸])by different methods. After the vaccination course, two P2-BSA peptide-vaccines both induced a strong antibody response against the P2-peptide by about 1:12800–25600 dilution, and a weak antibody response against the ELDKWA-epitope (1:1600–3200). The P2-P24EC and P2 (conjugated with itself) peptide-vaccines could also induce a weak antibody response against the ELDKWA-epitope (1:1600–3200), while an rgpl60 subunit vaccine induced a very weak antibody response (1:400). Interestingly, the ELDKWA-tetramer epitope-vaccine [C-(ELDKWAGVBSA] could induce a strong antibody response against the ELDKWA-epitope (1:12800–25600), i.e. It increased the level of ELDKWA-antibody eight-fold, clearly better than the P2 peptide-vaccine, and much better than the rgp160 subunit vaccine, which indicates that the immunogenicities of the ELDKWA-epitope on the ELDKWA-tetramer peptide, the C-domain peptide and rgp160 are very different. These results suggest that the ELDKWA-epitope-vaccine may be a new strategy for inducing high levels of epitope-specific neutralizing antibodies against HIV- 1. Using hybridoma-technique, a mouse monoclonal antibody recognizing the ELDKWA-epitope on ELDKWA-peptide and C-domain peptide was produced by immunization with the C-(ELDKWAG)₄-BSA epitope-vaccine, which indicates a new way to produce an epitope-specific mAb, namely immunization with epitope-vaccine instead of a natural or recombinant protein immunogen.

Key Words:

• immunogenicity
• epitope vaccine
• ELDKWA-epitope
• monoclonal antibody