Replication of human immunodeficiency virus type 1 in primary cultured placental cells

The role of placental cells in transplacental transmission of human immunodeficiency virus type 1 (HIV 1) was investigated. Placental macrophages and trophoblasts, which together represent the main cell components of the placenta, were cultivated separately and then compared to foetal monocyte-derived macrophages for susceptibility to HIV 1 infection. Placental macrophages treated with granulocyte-macrophage colony-stimulating factor (GM-CSF) were less easily infected with HIV 1 than were GM-CSF-treated foetal monocyte-derived macrophages. HIV 1 replication in cocultures consisting of infected placental macrophages together with a highly HIV 1-permissive cell line (CEM) was detected persistently for at least 6 weeks by reverse transcriptase assay, even though placental macrophages expressed no detectable CD4 receptor, as indicated by indirect immunofluorescence. HIV 1-specific DNA sequences were also detected in infected placental macrophages. Trophoblasts exhibited no detectable CD4 expression and did not support the replication of HIV 1, although low levels of HIV 1-specific DNA sequences could be detected in infected trophoblasts. Placental macrophages or trophoblasts (or both) may thus play an important role in transplacental HIV 1 transmission.