Inability of Plasmacytoid Dendritic Cells To Directly Lyse HIV-Infected

The function of plasmacytoid dendritic cells (PDC) in chronic human immunodeficiency virus type 1 (HIV-1) infection remains controversial with regard to its potential for sustained alpha interferon (IFN-) production and induction of PDC-dependent tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-mediated cytotoxicity of HIV-infected cells. We address these areas by a study of chronically HIV-1-infected subjects followed through antiretroviral therapy (ART) interruption and by testing PDC cytolytic function against autologous HIV-infected CD4 T cells. Rebound in viremia induced by therapy interruption showed a positive association between TRAIL and viral load or T-cell activation, but comparable levels of plasma IFN-/ were found in viremic ART-treated and control subjects. While PDC from HIV-infected subjects expressed less interferon regulator factor 7 (IRF-7) and produced significantly less IFN- upon Toll-like receptor 7/9 (TLR7/9) engagement than controls, membrane TRAIL expression in PDC from HIV subjects was increased. Moreover, no significant increase in death receptor 5 (DR5) expression was seen in CD4 T cells from viremic HIV subjects compared to controls or following in vitro infection/exposure to infectious and noninfectious virus or exogenous IFN-, respectively. Although activated PDC killed the DR5-expressing HIV-infected Sup-T1 cell line, PDC did not lyse primary autologous HIV CD4 T cells yet could provide accessory help for NK cells in killing HIV-infected autologous CD4 T cells. Taken together, our data show