SIMIAN IMMUNODEFICIENCY VIRUS-INFECTION OF CD8(-VIVO() LYMPHOCYTES IN)

To determine the lymphoid target cells of simian immunodeficiency viru s (SIV) in vivo, peripheral blood lymphocytes (PBL) and lymph node lym phocytes (LNL) were positively selected (> 97% purity) for surface exp ression of CD4, CD8, or CD20 and then analyzed for SIV provirus using semiquantitative DNA amplification. We found provirus in CD4(+) and CD 8(+) lymphocytes but none in CD20(+) lymphocytes. During acute SIV inf ection (less than or equal to 214 days postinoculation), the percentag e of PBL and LNL CD4(+) cells containing proviral DNA ranged from 0.2 to 20% and from 0.2 to 2%, respectively. Proviral burden in the CD8(+) population of either PBL or LNL ranged from 0.01 to 0.2%. Virus isola tion by cocultivation was positive for both CD4(+) and CD8(+) purified populations. No difference in proviral burden was observed between PB L and LNL subsets during acute SIV infection. Up to 19.4% of positivel y selected CD8(+) cells also expressed CD4, and thus the provirus may reside within a dual-positive population. This dual-positive populatio n may represent activated lymphocytes that are particularly susceptibl e to infection and may provide an opportunity for virus entry into the CD8(+) CD4(-) lymphocytes in vivo.