EARLY PHENOTYPIC AND FUNCTIONAL ALTERATIONS IN LYMPHOCYTES FROM SIMIAN IMMUNODEFICIENCY VIRUS-INFECTED MACAQUES

Phenotypic and functional changes in lymphocytes from rhesus monkeys ( Macaca mulatta) were investigated during the first 6 months after infe ction with SIVmac 32H. Animals preimmunized with keyhole limpet hemocy anin (KLH) were sacrificed 1, 3, 6, 12, and 24 weeks post infection. S ubset composition and function of lymphocytes from blood, spleen, lymp h node and thymus were analysed. In addition to a rapid decline in CD4 /CD8 ratios, a massive reduction in CD29+CD4+ cells was seen in the pe riphery. Although depletion of this subset was observed throughout the course of this experiment, the loss of proliferative T cell responses was most pronounced very early after infection and partially recovere d after Month 3. Polyclonal cytotoxic responses were only slightly aff ected. In the thymus, a gradual, but moderate loss of CD4+CD8+ immatur e thymocytes, and a relative increase in both CD4+ and CD8+ mature sub sets was observed. Infectious virus was readily recovered from homogen ates of lymph node and spleen, but not of thymus tissue. Interestingly , however, virus was detected in thymocytes from all infected animals by cocultivation with a simian immunodeficiency virus (SIV) susceptibl e cell line.