Identification of a synthetic peptide as part of a major neutralization epitope of respiratory syncytial virus.

A 7000 Mr cleavage fragment of the F1 subunit that carries the major neutralization epitope has been identified by chemical and enzymatic cleavage of the fusion protein of respiratory syncytial (RS) virus (Long strain) with an efficient RS virus-neutralizing monoclonal antibody. Based on the published mRNA-deduced sequence of the A2 strain, coupled to the hydropathicity profile and prediction of protein conformation, the neutralization epitope has tentatively been localized on the first third of the F1 protein N-terminal, probably in the region of amino acids 215Ser to 236Glu. Analysis of three peptides covering different portions of the 212Cys to 236Glu region of the F1 fusion protein identified a peptide (Cys X 216Asn to 236Glu) that reacted strongly with the neutralizing monoclonal antibody and that was efficient in blocking neutralization and in plaque-reducing assays, confirming that the neutralization epitope was localized in that region. Further analysis with two other synthetic peptides (212Cys to 222Glu and Cys X 221Ile to 236Glu) indicated that the dodecapeptide Ile-Glu-Phe-Gln-Lys-Asn-Asn-Arg-Leu-Leu-Glu mimicked either the whole or a major part of the neutralization epitope. This opens a promising avenue for the simple design of a synthetic peptide vaccine to control RS virus infection.