The trophoblastic epithelial barrier is not infected in full-term placentae of human immunodeficiency virus-seropositive mothers undergoing antiretroviral therapy

To study the mechanism of the placental barrier function, we examined 10 ma tched samples of term placentae, cord blood, and maternal blood obtained at delivery from human immunodeficiency virus (HN)infected mothers with child ren diagnosed as HIV negative in Sweden. All placentae were histologically normal, and immunochemistry for HIV type 1 p24 and gp120 antigens was negat ive. Highly purified trophoblasts (93 to 99% purity) were negative for HIV DNA and RNA, indicating that the trophoblasts were uninfected. Although HIV DNA was detected in placenta-derived T lymphocytes and monocytes, microsat ellite analysis showed that these cells were a mixture of maternal and feta l cells. Our study indicates that the placental barrier, i.e., the trophobl astic layer, is not HIV infected and, consequently, HIV infection of the fe tus is likely to occur through other routes, such as breaks in the placenta l barrier.