Rapid HIV-1 spread between CD4 T lymphocytes occurs at retrovirus-induced immune cell contacts called virological synapses (VS). VS are associated with striking T cell polarization and localized virus budding at the site of contact that facilitates cell-cell spread. In addition to this, spatial clustering of organelles including mitochondria to the contact zone has been previously shown. However, whether cell-cell contact specifically induces dynamic T cell remodeling during VS formation and what regulates this process remains unclear. Here we report that contact between an HIV-1 infected T cell and an uninfected target T cell specifically triggers polarization of mitochondria concomitant with recruitment of the major HIV-1 structural protein Gag to the site of cell-cell contact. Using fixed and live cell imaging we show that mitochondria and Gag polarization in HIV-1 infected T cells occurs within minutes of contact with target T cells, requires the formation of stable cell-cell contacts and is an active, calcium-dependent process. We also find that perturbation of mitochondria polarization impairs cell-cell spread of HIV-1 at the VS. Taken together these data suggest that HIV-1 infected T cells are able to sense and respond to contact with susceptible target cells and undergo dynamic cytoplasmic remodeling to create a synaptic environment that supports efficient HIV-1 VS formation between CD4 T lymphocytes
