Tissue Myeloid Cells in SIV-Infected Primates Acquire Viral DNA through Phagocytosis of Infected T Cells

The viral accessory protein Vpx, expressed by certain simian and human immunodeficiency viruses (SIVs and HIVs), is thought to improve viral infectivity of myeloid cells. We infected 35 Asian macaques and African green monkeys with viruses that do or do not express Vpx and examined viral targeting of cells in vivo. While lack of Vpx expression affected viral dynamics in vivo, with decreased viral loads and infection of CD4+ T cells, Vpx expression had no detectable effect on infectivity of myeloid cells. Moreover, viral DNA was observed only within myeloid cells in tissues not massively depleted of CD4+ T cells. Myeloid cells containing viral DNA also showed evidence of T cell phagocytosis in vivo, suggesting that their viral DNA may be attributed to phagocytosis of SIV-infected T cells. These data suggest that myeloid cells are not a major source of SIV in vivo, irrespective of Vpx expression. •Viral DNA is detected in myeloid cells irrespective of SIV Vpx expression•Myeloid cells contain viral DNA only in tissues containing CD4+ T cells•Myeloid cells containing viral DNA have recently phagocytosed T cells in vivo Vpx is thought to improve SIV infectivity of myeloid cells. Brenchley and colleagues find that tissue myeloid cells in SIV-infected primates acquire viral DNA through phagocytosis of infected T cells, irrespective of viral Vpx expression, suggesting that myeloid cells are not a major reservoir of SIV.