PROTECTION OF MN-RGP120-IMMUNIZED CHIMPANZEES FROM HETEROLOGOUS INFECTION WITH A PRIMARY ISOLATE OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1

Three chimpanzees immunized with recombinant gp120 from human immunode ficiency virus type 1 (HIV-1) strain MN and 1 control animal were chal lenged intravenously with a primary isolate of HIV-1(SF2). Viral infec tion was detected in the control animal by viral culture, polymerase c hain reaction, and multiple serologic assays beginning 2 weeks after i nfection, Markers of HIV-1 infection were not detected in any of the g p120-vaccinated animals during 12 months of follow-up, Antisera from t he gp120-immunized chimpanzees were unable to neutralize the challenge virus cultured in peripheral blood mononuclear cells (PBMC), These st udies demonstrate that immunization with recombinant gp120 derived fro m a T cell-adapted isolate prevented infection by a heterologous prima ry isolate of HIV-1. The results suggest that in vitro virus neutraliz ation assays utilizing primary isolates cultured in PBMC may be imperf ect indicators of protection in vivo.