Progressive infection in a subset of HIV-1-positive chimpanzees

Chimpanzees are susceptible to infection with human immunodeficiency virus (HIV)-1; however, infected animals usually maintain normal numbers of CD4() T lymphocytes and do not develop immunodeficiency. We have examined 10 ch ronically infected HIV-1-positive chimpanzees for evidence of progressive i nfection. In addition to 1 animal that developed AIDS, 3 chimpanzees exhibi t evidence of progressive HIV infection. All progressors have low CD4(+) T cell counts (<200 cells/mu L), severe CD4:CD8 inversion, and marked reducti on in interleukin-2 receptor expression by CD4(+) T cells. In comparison wi th HIV-positive nonprogressor chimpanzees, progressors have higher plasma a nd lymphoid virus loads, greater CD38 expression in CD8(+)/HLA-DR+ T cells, and greater serum concentrations of soluble tumor necrosis factor type II receptors and beta 2-microglobulin, all markers of HIV progression in human s. These observations show that progressive HIV-1 infection can occur in ch impanzees and suggest that the pathogenesis of progressive infection in thi s species resembles that in humans.