OBJECTIVETo investigate the biological and clinical features of Chinese rhesus monkeys after intravenous (IV) and intrarectal (IR) challenge with SIVmac239 in rhesus monkeys of Chinese origin, and compare the differences between the routes of infection.

METHODSRhesus monkeys of Chinese origin were inoculated with SIVmac239 either by IV (n = 19) or IR (n = 6) routes. Simian immunodeficiency virus (SIV)-specific antibody titer, CD4 + T cell counting, plasma SIV load, lymph node pathology, and clinical manifestations were compared between these two groups 232 or 168 days after challenging.

RESULTSAll SIVmac239-inoculated animals became seropositive for SIV-specific antibodies. SIV-specific IgM was detected in IV groups as from day 10 but was not detected in IR for all the time points. Although SIV-specific IgG was detected as from day 30 in both groups, the IgG titers were ten-fold higher in IV group than in IR group after day 168. CD4 + T-cell counting decreased progressively in IV group but remained stable in IR group over time. Plasma SIV RNA loads peaked in all animals between day 10 and day 14 (10(7) copies/ml), then declined to "setpoint" (10(3) - 10(6) copies/ml) about 2 months later. Most inoculated animals manifested lymphadenopathy. Two animals in IV group and one in IR group died of simian AIDS between day 150 and day 210, as evidenced by the autopsies showing the depletion of lymph tissues, Pneumocystis carinii pneumonia and other opportunity infections. Conclusion IV or IR inoculation of SIVmac239 in Chinese rhesus monkeys will result in chronic SIV infection with a similar clinical feature of natural HIV infection, which provides an excellent experimental animal model for AIDS.