PERFORMANCE OF A MODIFIED HIV-1 P24 ANTIGEN-ASSAY FOR EARLY DIAGNOSISOF HIV-1 INFECTION IN INFANTS AND PREDICTION OF MOTHER-TO-INFANT TRANSMISSION OF HIV-I IN DAR-ES-SALAAM, TANZANIA

The aim of this study was to determine the utility of an amplified hum an immunodeficiency virus type 1 (HIV-I) p24 antigen tag) assay using heated plasma or serum samples for the early diagnosis of HIV-I infect ion in infants and for the prediction of the risk of mother-to-infant (MTI) transmission of HIV-1 in Dar es Salaam, Tanzania. The study incl uded 125 samples from 76 infants positive for HIV DNA by the polymeras e chain reaction (PCR), 106 samples from 101 PCR-negative infants and 116 and 160 samples from seropositive and seronegative mothers, respec tively. Samples were boiled to dissociate immune complexes and tested for HIV-I p24 ag using a p24 ag amplification assay. Reactive samples were confirmed by a neutralization assay. Altogether, 123 of 125 sampl es from 76 PCR-positive infants were positive for p24 ag (sensitivity = 98.7%). HIV-1 p24 ag was found in all 18 samples collected at 1-8 we eks, in 35 of 36 samples collected at 9-26 weeks, in all 40 samples co llected at 27-52 weeks, and in 30 of 31 samples collected >52 weeks af ter birth. Detection of HIV-I p24 ag was significantly more common in transmitting mothers (12 of 29, 41.4%) than in nontransmitting ,mother s (nine of 87, 10.3%) (p < 0.001). Among mothers with p24 antigenemia, the vertical transmission rate was significantly higher (12 of 21, 57 %) than in mothers without p24 antigenemia (17 of 95, 18%) (p < 0.001) . All samples from 101 PCR-negative children and 160 seronegative moth ers were negative for p24 ag (specificity = 100%). We conclude that us ing heated plasma or serum increases the sensitivity of the p24 ag ass ay significantly. This modified simple test may be sufficient for the early diagnosis of HIV-I infection in infants in settings with limited laboratory facilities. It is also useful for prediction of the risk o f MTI transmission of HIV-1.