THE RELATIONSHIP BETWEEN MATERNAL-INFANT ANTIBODY-LEVELS AND VERTICALTRANSMISSION OF HIV-1 INFECTION

This study assesses the predictive value of the ratio of HIV-1 antibod ies in the newborn at birth to that in the mother for perinatally tran smitted infection confirmed subsequently by age 18 months, The ratio o f HIV-1 (EIA) antibody levels in the baby at birth to that in the sero positive mother after the first trimester (sequestration index SI) was available in 114 of a perinatal cohort of 137 infants, We related thi s ratio to the HIV infection status of the children by 18 months, HIV- l DNA PCR and HIV-specific IgA antibody detection at birth, between 3 and 6 months, and morbidity and mortality, Thirty-five of the 137 (26 per cent) children were diagnosed as infected by 18 months, The mean ( SD) HIV SI was 1.57 (0.88) in 29 infected and 0.83 (0.42) in 85 uninfe cted infants (P< 0.0001), Sensitivity and specificity of a threshold S I of 1.27 (mean + 2 SD of uninfected group) for the prediction of peri natal HIV-l infection were 41 and 98 per cent, respectively, The reaso n for the higher SI in the infected babies is the combination of lower antibody titres in the transmitting mothers with raised levels in the infected babies. A similar analysis of antibody ratios showed no stat istical differences for measles and tetanus (P> 0.1) between HIV infec ted and uninfected groups, There was a tendency to increased morbidity (Pearson's correlation coefficient r = 0.31) and more severe disease in those with higher HIV-1 SI, Three of 17 (18 per cent) peripheral bl ood samples from infected children at birth were PCR positive; all had SI's above the threshold, Overall sensitivity and specificity of PCR were 85 per cent each, Eleven of the 29 infected children were HIV-1 s pecific IgA positive at birth; six (64 per cent) of these had an SI>1. 27, This simple SI of HIV-1 EIA antibodies at birth is comparable to e laborate techniques in its power to predict perinatally acquired infec tion, It may be a cheap, reliable and rapid screening test for vertica lly transmitted HIV-1 infection.