HIV-1 in placentas of untreated HIV-1-infected women in relation to viral transmission, infectious HIV-1 and RNA load in plasma

The presence of HIV in the placenta was analysed in relation to virological and immunological factors and vertical transmission of HIV in 39 pregnanci es between 1989 and 1993 among 37 HIV-1-infected women without zidovudine p rophylaxis. HIV-1 was detected in 12 of 37 (31%) placentas by immunohistoch emistry and in 3 of 18 by PCR. Altogether 14/39 (36%) placentas bore eviden ce of HIV-1 infection, although there was no relation with the outcome of H IV infection in the child. Neither was there a relation between placental i nfection and either CD4 cell counts or HIV-1 RNA levels. However, HIV-1 was isolated from plasma in 20 of 39 (50%) pregnancies, which,vas inversely re lated to the presence of HIV in the placenta. When HIV-1 was identified in the placenta, HIV-I was isolated from plasma in 3/14 (21%) pregnancies, vs 17/25 (68%) when it was not (p = 0.01), with a relative risk of having a pl acenta positive for HIV of 3.9 in pregnancies with a negative plasma HIV is olation. This inverse relation may point to differences in tropism between HIV-I in placenta and plasma. The results show that the placental barrier p revents HIV transmission, irrespective of whether HIV enters the placenta o r not.