T-CELL APOPTOSIS IN HUMAN-IMMUNODEFICIENCY-VIRUS TYPE 2-INFECTED AND SIMIAN IMMUNODEFICIENCY VIRUS-INFECTED MACAQUES

Recent evidence suggests that T cell apoptosis could be involved in th e pathogenesis of HIV infection, In addition, lymphocyte apoptosis has been described in SIV-infected macaques that developed simian AIDS, T o investigate further the role of apoptosis in AIDS pathogenesis, we s tudied lymphocytes of HIV-2-infected cynomolgus macaques that did not develop simian AIDS, We compared apoptosis of lymphocytes from animals infected with non-pathogenic HIV-2 to that in macaques infected with pathogenic SIV, Unfractionated peripheral blood mononuclear cells of S IV- and HIV-2-infected macaques showed evidence of apoptosis by electr on microscopy, Row cytometry (terminal dUTP nick end labelling) and vi sualization of DNA fragmentation, Between 30-50% apoptotic cells could be detected in SIV-infected animals, compared to approximately 30% in HIV-2-infected and 5-12% in uninfected monkeys, However, separation o f PBMC into T cell subpopulations revealed striking differences in apo ptosis between SIV- and HIV-2-infected macaques. In SIV-infected monke ys both CD4 and CD8 cells underwent apoptosis to a large extent, In co ntrast, in the HIV-2-infected macaques apoptosis was restricted to the CD8 cell compartment. The lack of apoptosis in CD4 cells of healthy H IV-2-infected macaques implies an important role for CD4 cell apoptosi s in AIDS pathogenesis.