Spectrum of disease in macaque monkeys chronically infected with SIV/SMM.

Twelve rhesus and one pig-tailed macaque have been monitored for 28-41 months following experimental infection with 10(4) TCID of SIV/SMM. Twelve of the 13 animals became virus positive and seroconverted within 3 to 6 weeks of exposure; the remaining animal seroconverted at 6 months, but has remained virus negative. Six of the 13 animals (46%) died between 14 and 28 months post-infection, following prolonged clinical disease characterized by chronic diarrhea and weight loss, peripheral lymphadenopathy and hemogram abnormalities. Histologic findings ranged from prominent follicular hyperplasia to severe lymphoid depletion, with lymphoid tissues often showing an infiltrate of syncytial giant cells. One animal had intestinal cryptosporidiosis and two had brain lesions comparable to those seen in AIDS encephalopathy in humans. Three of the remaining seven animals have an ARC-like disease and are showing gradual deterioration of their clinical condition. These animals, as well as animals that died, had progressive decreases in CD4+ cells and CD4+/CD8+ cell ratios. These observations further document the marked clinical, pathologic and immunologic similarities between human AIDS and the SIV-infected macaque model.