Viremia control following antiretroviral treatment and therapeutic immunization during primary SIV251 infection of macaques

Prolonged antiretroviral therapy (ART) is not likely to eradicate human imm unodeficiency virus type I (HIV-I) infection. Here we explore the effect of therapeutic immunization in the context of ART during primary infection us ing the simian immunodeficiency virus (SIV251) macaque model. Vaccination o f rhesus macaques with the highly attenuated poxvirus-based NYVAC-SIV vacci ne expressing structural genes elicited vigorous virus-specific CD4(+) and CD8(+) T cell responses in macaques that responded effectively to ART. Foll owing discontinuation of a six-month ART regimen, viral rebound occurred in most animals, but was transient in six of eight vaccinated animals. Viral rebound was also transient in four of seven mock-vaccinated control animals . These data establish the importance of antiretroviral treatment during pr imary infection and demonstrate that virus-specific immune responses in the infected host can be expanded by therapeutic immunization.