The induction of neutralizing antibodies by synthetic peptides of the envelope protein of type D simian retrovirus-1 (SRV-1)

It has been recently demonstrated that two serotypes of type D simian retroviruses, namely SRV-1 and SRV-2, exhibit extensive immunological cross-reactivity but do not exhibit cross-reactivity at the level of neutralizing antibodies. We have also shown recently that an area which includes residues 147-162 of the envelope protein of SRV-1 constitutes an epitope to which neutralizing antibodies against SRV-1 but not against SRV-2 are directed. However, in spite of the capacity of various immunogenic preparations to induce antibodies which react with SRV-1 these antibodies were incapable of neutralizing in vitro viral infectivity. Work reported herein demonstrates that various immunogens consisting of a larger peptide, namely 142-167 of the envelope protein of SRV-1, induce antibodies capable of binding with the envelope protein of SRV-1 and with the whole virus. Moreover, these antibodies exhibit the capacity to neutralize in vitro the infectivity of SRV-1 but not of SRV-2.