Experimental infection of cynomolgus monkeys (Macaca fascicularis) with simian immunodeficiency virus (SIVsm).

Five healthy cynomolgus monkeys were inoculated intravenously with simian immunodeficiency virus (SIVsm) propagated in human lymphocytes. All five animals became infected. Virus was recovered from blood mononuclear cells and viral antigen was detected in serum 12 days postinoculation (PI) in all inoculated animals. Virus was also isolated in all five animals tested 74 to 226 days PI. Antibodies to different structural proteins of SIV and HIV-2 were demonstrated by ELISA, Western blot, and radioimmunoprecipitation assay from day 31 PI concomitantly with a reduction of viral proteins in the serum. Reappearance of antigen accompanied by a fall in antibody to gag products (p26) was observed in two monkeys 69 days PI. All SIV-infected monkeys showed a pronounced decrease in CD4+ lymphocytes demonstrable already 12 days PI. They also developed persistent lymphadenopathy. Thus, infection of cynomolgus monkeys with SIVsm mimics events in human immunodeficiency virus infection in humans but the course of evolution of pathogenic events in the monkey is markedly compressed. This experimental model will be useful for evaluation of HIV vaccines and antiviral testing.