Immunologic alterations in monkeys with simian acquired immunodeficiency syndrome (SAIDS)

Levels of lymphocyte responsiveness to T- and B-cell-specific mitogens and expressions of Ia, T4, T8, and T11 surface markers were monitored during the course of Simian acquired immunodeficiency syndrome (SAIDS) in four Rhesus macaques that either died or became ill and survived. The monkey that died showed progressively suppressed responses to concanavalin A (Con A), phytohemagglutinin (PHA), pokeweed mitogen (PWM), and Staphylococcus aureus Cowan I strain (SAC) through the time of death (5 1/2 weeks). For the three animals that survived, the responses of peripheral blood mononuclear cell (PBMC) to the same mitogens were decreased significantly during the period 4-6 weeks after inoculation. Levels of Ia-bearing cells in the PBMC population were markedly reduced in the moribund monkey but were not significantly decreased in the three survivors. There was no significant change in the percentage of T11-bearing cells in any of the study animals. The ratio of T4- and T8-positive cells did not vary significantly during the 18 weeks of observation in any of the animals. The infected animals showed other evidence of immunosuppression including neutropenia, lymphopenia, and depletion of lymphocytes in lymph nodes. The animal that had progressive disease and death also had Kaposi-like lesions and staphylococcal septicemia. These results indicated that in vitro evidence of immunosuppression due to SAIDS appears within a few weeks after infection and this may progress in animals that die.