HLA antigen frequencies in children born to HIV-infected mothers.

Tissue-typing for HLA-A, B, and DR antigens was carried out on 53 babies, 47 of them unrelated, born to mothers known to be HIV-infected from intravenous drug usage or sexual contact with drug users. These babies were followed up to assess whether HLA phenotype was associated with vertical transmission of HIV infection or disease progression. Of the 47 unrelated babies, eight became infected with HIV. The frequency of HLA-DR3 was three times higher in the HIV-positive infants compared to the HIV-negative infants (43 per cent vs 15 per cent) in our study population. Conversely, HLA-A3 was three times less common in the HIV-positive infants (12.5 per cent vs 42 per cent). A comparison of HLA antigens between our study group babies and babies born to healthy mothers unselected for HIV status revealed higher proportions of HLA-B18, B7, and DR2 in the study group. Moreover, the combination, A3, B7, DR2 was four times commoner in our study population relative to controls (RR = 3.9; p less than 0.003), but was found only in babies who were not HIV infected. The combination A1, B8, DR3, in contrast, was found less often than expected in our study group (RR = 0.39) and was disproportionately represented amongst the infected babies. We have observed an unexpectedly low (6 per cent) mother-to-infant transmission rate of HIV among prospectively studied intravenous drug users. We speculate that the unusually high ratio of the common antigen combinations (often halotypes), A3, B7, DR2 to A1, B8, DR3 in this population may be contributory.