AN ASSESSMENT OF THE TIMING OF MOTHER-TO-CHILD TRANSMISSION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 BY MEANS OF POLYMERASE CHAIN-REACTION

To approximate the contributions of in utero, intrapartum, and postnat al transmission of human immunodeficiency virus type-1 (HIV-1) and to evaluate polymerase chain reaction (PCR) as a diagnostic tool for pedi atric HIV infection, blood was collected at birth (cord blood), and at 3, 6-12, and 13-24 months in 218 children born to HIV-1-seropositive mothers in Kigali, Rwanda. Proviral DNA was detected by a double PCR u sing two sets of three primers (gag, poi, and env). Pediatric HIV-1 in fection was defined according to serological and clinical criteria. Th e probability of having a positive PCR at a given time was calculated by a nonparametric method. Among children with unequivocal evidence of infection (n = 47), it was 30.5% on cord blood and 80.6% at 3 months. Thus, in children born to HIV-1-infected mothers, the estimated rate of transmission in the late postnatal period is 4.9%, and the rate of transmission in the intrapartum plus postnatal periods is 17.6%. Among 117 HIV-1-uninfected children born to HIV-1-infected mothers, six (5% ) had a false-positive PCR on cord blood. These results should be take n into account in designing intervention trials aimed at reducing moth er-to-child transmission of HIV-1.