STUDIES ON THE PLACENTAL-TRANSFER OF CELL-FREE HUMAN-IMMUNODEFICIENCY-VIRUS AND P24 ANTIGEN IN AN EX-VIVO HUMAN PLACENTAL MODEL

OBJECTIVE: We studied whether the human placenta has the structural in tegrity to impede transplacental passage of cell-free human immunodefi ciency virus (HIV/)-1 or p24 antigen from the maternal to the fetal ci rculation. METHODS: Nine term human placentas from uncomplicated vagin al or cesarean section deliveries were studied ex vivo with a placenta l perfusion apparatus to determine whether cell-free HIV/-1 at 200-200 0 tissue culture infections dose (TCID50/mL) would pass to the fetal c irculation. Passage of virus or p24 was assessed by infectivity titrat ion and/or p24 antigen capture enzyme immunoassay. RESULTS: Infections HIV-1 was not detected in any of the fetal perfusate samples taken pe riodically during experiments. Low concentrations of HIV-1 p24 antigen , however, were detected in fetal perfusate samples from three placent as. CONCLUSIONS: The term human placenta effectively impedes passage o f cell-free HIV-1 from the maternal to the fetal circulation. However, it may be permeable to passage of p24 antigen.