Relationship between human immunodeficiency virus-1 RNA identification in placenta and perinatal transmission

The objectives of this study were to identify human immunodeficiency virus (HIV)-associated nucleic acids in placenta with 35S RNA in situ hybridization and to correlate the presence of virus with perinatal HIV transmission.

Blood from nine mother-infant pairs was collected for CD4+ lymphocyte count and p24 antigen analysis. Placental specimens were obtained for in situ hybridization, viral culture, and hematoxylin-eosin histologic analysis. Neonatal infection was diagnosed by p24 antigen analysis, polymerase chain reaction, and viral culture. Pediatric follow-up was obtained by personal communication and review of chart records.

Three of 10 placentas from nine HIV-positive pregnant women (one set of twins) were found to contain evidence of HIV infection by RNA in situ hybridization. Maternal age, gravidity, parity, previous number of terminations, duration HIV-seropositive, maternal CD4+ at delivery, and neonatal cord CD4+ count were similar in those whose placentas contained virus versus those in whom virus was not identified. The incidence of histologic changes was similar in the HIV-positive and negative placentas from seropositive subjects and was similar to the incidence of histologic changes in placentas from known seronegative subjects. Placental culture failed to demonstrate the presence of virus in vitro. Of the three placentas that had positive in situ hybridization, two infants became HIV-positive.

35S RNA in situ hybridization identified the presence of nucleic acids in syncytiotrophoblasts from formalin-fixed, paraffin-embedded placentas. This technique is a useful tool to screen placentas at birth for HIV-RNA to judge the likelihood of perinatal HIV transmission.