Acutely infected Langerhans cells are more efficient than T cells in disseminating HIV type 1 to activated T cells following a short cell-cell contact.

Most human immunodeficiency virus type 1 (HIV-1) infections involve sexual contact and virus passage across mucosal surfaces. While Langerhans cells (LCs) and dendritic cells (DCs) have been implicated in mucosal infection, their role is undefined. Here we demonstrate that acutely HIV-1-infected LCs and DCs effectively transmit virus to uninfected, activated T cells. Cocultivation of these cells results in massive virus production that requires a short cell-cell contact; as little as 30 min contact time is sufficient for HIV-1-pulsed DCs to infect their target T cells. Furthermore, surface-bound virus inactivation by trypsin does not significantly decrease the efficiency of virus transmission by LC/DCs, suggesting rapid internalization of virus. This effective virus transfer by infected LCs and blood-derived DCs requires prior activation of T cells. Surprisingly, cocultivation of acutely infected T cells with uninfected, activated target T cells results only in low virus production, even with T cell-tropic virus. We conclude that LCs and DCs are not only important targets of HIV-1 infection, but may also play a key role in the early dissemination of virus to T cells they encounter in skin or lymphoid tissue.