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

Abstract

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 chronically infected HIV-1-positive chimpanzees for evidence of progressive infection. In addition to 1 animal that developed AIDS, 3 chimpanzees exhibit evidence of progressive HIV infection. All progressors have low CD4+ T cell counts (<200 cells/μL), severe CD4:CD8 inversion, and marked reduction in interleukin-2 receptor expression by CD4+ T cells. In comparison with HIV-positive nonprogressor chimpanzees, progressors have higher plasma and 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 β2-microglobulin, all markers of HIV progression in humans. These observations show that progressive HIV-1 infection can occur in chimpanzees and suggest that the pathogenesis of progressive infection in this species resembles that in humans.