Trophoblasts are productively infected by CD4-independent isolate of HIV type 1

Evidence for HIV-1 infection of trophoblasts is discordant. Utilizing highly purified full-term trophoblasts, we demonstrate that full-term trophoblasts express CXCR4 but are negative for CCR5 and CD4 cell surface proteins. Full-term trophoblasts were refractory to infection by HIV-1 IIIB and primary isolates of HIV-1. However, full-term trophoblasts could be infected by a CD4-independent, CXCR4-utilizing HIV-1 strain, as demonstrated by substantial p24 (5.5 ng/ml) levels and HIV-1 gag/pol DNA content (3050 copies/microg) 7 days postinfection. These data illustrate that trophoblasts express the essential host factors for productive HIV-1 infection and that the block to HIV-1 infection may be at the level of entry. In additional, our data suggest that CD4-independent mechanisms of infection may play a role in promoting in utero HIV-1 transmission.