Naturally occurring V1-env region variants mediate simian immunodeficiencyvirus SIVmac escape from high-titer neutralizing antibodies induced by a protective subunit vaccine

Macaques which developed high-titer neutralizing antibodies (htNAb) after i mmunization with a virion-derived oligomeric envelope glycoprotein subunit vaccine were protected against a homologous simian immunodeficiency virus S IVmac challenge. Here we demonstrate that the htNAb could be overcome by Vl -env region variants isolated ex vivo from an SIVmac-infected macaque. The results further suggest that the development of VI-env region neutralizatio n escape mutants is also necessary for survival of the virus in infected ma caques. The immunological capacity of a single variable region to induce ne utralizing antibodies in vaccinated and infected macaques initiate new idea s for a successful vaccine strategy.