Simian immunodeficiency virus infection of CD8(+) lymphocytes in vivo

To determine the lymphoid target cells of simian immunodeficiency virus (SIV) in vivo, peripheral blood lymphocytes (PBL) and lymph node lymphocytes (LNL) were positively selected (> 97% purity) for surface expression of CD4, CD8, or CD20 and then analyzed for SIV provirus using semiquantitative DNA amplification. We found provirus in CD4(+) and CD8(+) lymphocytes but none in CD20(+) lymphocytes. During acute SIV infection (less than or equal to 214 days postinoculation), the percentage 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 isolation by cocultivation was positive for both CD4(+) and CD8(+) purified populations. No difference in proviral burden was observed between PBL and LNL subsets during acute SIV infection. Up to 19.4% of positively selected CD8(+) cells also expressed CD4, and thus the provirus may reside within a dual-positive population. This dual-positive population may represent activated lymphocytes that are particularly susceptible to infection and may provide an opportunity for virus entry into the CD8(+) CD4(-) lymphocytes in vivo.