PEPTIDE MIMICS OF A CONFORMATIONALLY CONSTRAINED PROTECTIVE EPITOPES OF RESPIRATORY SYNCYTIAL VIRUS FUSION PROTEIN

Aims: To identify peptides that mimic (mimotopes) conformational and p rotective epitopes of RSV fusion protein and to assess their efficacy as immunogens and potential vaccines. Material and methods: An 8-mer s olid-phase (TG resin) library was screened with a neutralising and pro tective RSV fusion protein specific monoclonal antibodies (Mab-19). Af ter selection of positive beads, reactive sequences were identified by microsequencing and 8-mer peptides were synthesised. Improvement of b inding was analysed by amino acid replacement using the SPOTs method. Results: Mabs were not able to bind to the free and soluble peptides, nor did these peptides induce anti-RSV specific antibodies. However, s everal peptides re-synthesised on a TG resin (to produce de-protected 8-mer peptides linked to the resin) or as SPOTs reacted specifically. Therefore it was critical to be able to reproduce this conformation in order to use these mimotopes as immunogens and potential vaccines. Us ing C-terminal constrained versions of the mimotopes, strong binding o f one of the Mabs to the peptides was demonstrated by surface-plasmon resonance. Immunisation of Balb/c mice with these peptide-mimics produ ced anti-sera that: (1) reacted specifically with RSV; (2) inhibited t he binding of the Mab to the virus; (3) neutralised RSV in vitro with high titres (range: 80-640); and (4) reduce significantly the viral lo ad in the lungs of mice challenged with RSV (P < 0.01). Conclusions: T his report demonstrates for the first time that: (1) a protective epit ope of the conserved RSV fusion protein can be mimicked by synthetic p eptides; and (2) immunisations with these mimotopes induced specific a nti-RSV neutralising antibodies and reduced viral load in vivo. These results represent a novel concept for the development of a vaccine aga inst RSV. Published by Elsevier Science B.V.