Acute infection of Macaca nemestrina by human immunodeficiency virus type 1.

The pigtail macaque (Macaca nemestrina) has a marked sensitivity to infection by simian immunodeficiency virus and human immunodeficiency virus type 2 (HIV-2). On this basis, we previously studied this species' susceptibility to HIV-1 and demonstrated infection in six macaques inoculated with either cell-associated HIV-1 or cell-free virus alone. This report expands upon our initial in vitro and in vivo findings. Five laboratory-adapted and one primary clinical strain of HIV-1 replicated in vitro in human and M. nemestrina peripheral blood mononuclear cells (PBMCs). Replication was enhanced when CD4+ purified PBMCs were infected and inhibited when PBMC cultures were treated with zidovudine. All six macaques demonstrated HIV-1 infection of PBMCs from 2 to 8 weeks after inoculation but nearly all PBMC cultures were negative from weeks 10 to 40. Polymerase chain reaction showed HIV-1 gag DNA in the PBMCs of all infected macaques, including times when the macaques were culture negative. All macaques developed and maintained antibodies to gag and envelope HIV-1 proteins from week 4 after inoculation through the period of observation. Five macaques showed neutralizing antibody. These findings suggest that M. nemestrina can be infected by cell-free and cell-associated HIV-1. This model of acute HIV-1 infection may help in evaluating the pathogenesis of HIV-1 replication and candidate vaccines and therapies.