Dendritic cells promote the spread of human T-cell leukemia virus type 1 via bidirectional interactions with CD4+ T cells

Human T-cell leukemia virus type-1 (HTLV-1) propagates within and between individuals via cell-to-cell transmission, and primary infection typically occurs across juxtaposed mucosal surfaces during breastfeeding and sexual intercourse. It is therefore likely that dendritic cells (DCs) are among the first potential targets for HTLV-1. However, it remains unclear how DCs contribute to virus transmission and dissemination in the early stages of infection. We show that an HTLV-1-infected cell line (MT-2) and naturally-infected CD4+ T-cells transfer p19+ viral particles to the surface of allogeneic DCs via cell-to-cell contacts. Similarly organized cell-to-cell contacts facilitate DC-mediated transfer of HTLV-1 to autologous CD4+ T-cells. These findings shed light on the cellular structures involved in anterograde and retrograde transmission, and suggest a key role for DCs in the natural history and pathogenesis of HTLV-1 infection