Dendrite cell-T cell mixtures, isolated from the skin and mucosae of macaques, support the replication of SIV.

Previous studies have shown that HIV-1 exploits dendritic cells (DCs) to replicate and spread among CD4+ T cells. The DCs within mucosal surfaces may be especially important, but these are more difficult to access. To study more extensively the properties of DCs and other leukocytes from skin and different mucosae, DCs were isolated from uninfected macaques and their sensitivity assessed to infection with SIV in vitro. Dendritic cells and T cells readily emigrated from organ cultures of macaque skin, as described previously for humans. In addition, characteristic cells emigrated from explants of mucosae, both nasopharyngeal (adenoid and tonsil) and genital (vagina and cervix). The macaque DCs reacted with the monoclonals that are used to study human DCs, such as MAbs to CD40, CD86, CD83, and the p55 protein. When SIV was added to the DC-T cell mixtures from these different organs, extensive replication was observed in all but the cervical leukocytes. SIV replication occurred without the use mitogens, and with virus that had been grown in a cell line in the absence of mitogens and IL-2. Most of the newly synthesized viral protein is observed in syncytia. Therefore, mixtures of DCs and T cells isolated from mucosal surfaces served as a naturally permissive environment for SIV replication.