Distribution and quantification of human immunodeficiency virus type 1, strain JC499, proviral DNA in tissues from an infected chimpanzee.

Data are accumulating to show that the natural history of human immunodeficiency virus type 1 (HIV-1) in chimpanzees closely reproduces that in humans and is influenced by biologic properties of the infecting HIV-1 strain. To determine the distribution and relative amounts of HIV-1, proviral DNA in multiple tissues from a chimpanzee euthanized because of an abdominal tumor and kidney failure was quantified by nested PCR limiting-dilution assays. At death, 21 months after infection with HIV-1(JC499), this animal had a CD4(+) T-cell count of 268 and 1.7 x 10(5) copies of virion RNA/ml of plasma. The highest proviral burdens were in peripheral lymph nodes and blood, followed by lung, colon, and spleen; values ranged from 130 to 3350 proviral copies/microg DNA (equivalent to DNA in 150,000 cells). The lowest levels of virus were in the spinal cord, brain, and cecum (0.3 to 2.5 copies/microg DNA), with all other tissues harboring intermediate levels (6.8 to 114 copies/microg DNA). Viral burdens in all tissues were comparable to or greater than those reported for HIV-1-infected humans in all stages of disease. Immunohistochemistry for HIV-1 p24 Gag antigen revealed (i) trapping of HIV-1 on follicular dendritic cells in lymph node germinal centers and (ii) virus in the brain, where it was localized primarily to capillary endothelial cells in the cerebral cortex. Analysis of the genetic diversity of the Env V3 loop in tissues indicated that there was no apparent compartmentalization of HIV-1 variants. Of interest, in 83 of 94 (88.3%) clones sequenced, the unique GYGR motif at the tip of the V3 loop of HIV-1(JC499) had reverted to the more common GPGR. The results support the conclusion that HIV-1 has the potential to maintain high viral burdens in chimpanzees and to disseminate to most organs, including the central nervous system. The use of the chimpanzee model with HIV-1(JC499) (or related strains) in vaccine efficacy studies should prove valuable, especially when assessing protection against disease. Furthermore, comparison of both replicative properties of HIV-1(JC499) with SIVcpz strains and immune responses of chimpanzees infected with these viruses might provide new information about HIV pathogenesis.