HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INFECTION OF HUMAN PLACENTAL MACROPHAGES IN-VITRO

Placental macrophages (Hofbauer cells) were isolated and cultured in v itro to investigate their susceptibility to human immunodeficiency vir us type 1 (HIV-1) infection. Of adherent cells, 80% expressed CD14, an d >99% were nonspecific esterase-positive. CD4 antigen was expressed a t very low levels. CD4 mRNA could be detected in the cells by reverse transcription followed by polymerase chain reaction. The macrophages w ere infected productively after inoculation with low-passage blood iso lates of cell-free HIV-1. Peak virus titers were detected 3-7 days aft er infection by HIV-1 antigen ELISA and reverse transcriptase assay. R eplication of HIV-1 in placental macrophages was less than in blood mo nocytes. HIV-I RNA was detected in placental macrophages by in situ hy bridization 16 days after infection. Multinucleated giant cells were i dentified in some cultures, indicative of an HIV-induced cytopathic ef fect. Thus, placental macrophages can be infected productively with cl inical isolates of HIV-1, and such cells may act as a reservoir of vir us for transmission to the fetus in utero.