Class I–unrestricted noncytotoxic anti–HTLV-I activity of CD81 T cells

Although it is widely believed that viral clearance is mediated principally by the destruction of infected cells by cytotoxic T cells, noncytolytic antiviral activity of CD81 T cells may play a role in preventing the progression to disease in infections with immunodeficiency viruses and hepatitis B virus. We demonstrate here that (1) replication of human T-lymphotropic virus type I (HTLV-I) is more readily detected from CD81 T-cell– depleted (CD82) peripheral blood mononuclear cells (PBMCs) of healthy HTLV-I carriers than from unfractionated PBMCs, (2) cocultures of CD82 PBMCs with autologous or allogeneic CD81 T cells suppressed HTLV-I replication, and (3) CD81 T-cell antiHTLV-I activity is not abrogated in trans-well cultures in which CD81 cells are separated from CD82 PBMCs by a permeable membrane filter. These results suggest that class I-unrestricted noncytolytic anti–HTLV-I activity is mediated, at least in part by a soluble factor(s), and may play a role in the pathogenesis of HTLV-I infection. (Blood. 2000;96: 1994-1995)