Vaccine Protection against a Heterologous, Non-Syncytium-Inducing, Primary Human Immunodeficiency Virus

Vaccine-induced protection of chimpanzees against laboratory-adapted and syncytium-inducing, multiply passaged primary human immunodeficiency virus type 1 (HIV-1) isolates, but not against non-syncytium-inducing, minimally passaged ones, has been demonstrated. Following challenge with such an isolate, HIV-1(5016), we obtained complete protection in one of three chimpanzees previously protected against low- and high-dose HIV-1(SF2) exposures after immunization with an adenovirus-HIV-1(MN) gp160 priming–HIV-1(SF2) gp120 boosting regimen. At challenge, the protected chimpanzee exhibited broad humoral immunity, including neutralizing antibody activity. These results demonstrate the potential of this combination vaccine strategy and suggest that vaccine protection against an HIV isolate relevant to infection of people is feasible.