Objective: To evaluate the presence of HIV-specific IgA antibodies as a diagnostic marker for vertical HIV infection in babies.

Study Design: A modified IgA antibody-capture enzyme-linked immunoabsorbent assay was used to detect HIV-specific IgA antibodies in serial plasma samples collected from 65 infants born to HIV infected mothers.

Results: HIV-specific IgA antibodies were detected in 80 out of 85 plasma specimens (94%) from 21 HIV infected babies. All the 71 specimens collected during the first 3 months from 44 HIV negative infants were also HIV-IgA positive (100%). Starting from four months of age, the number of samples in the seroreverter group that tested negative for HIV-IgA increased. All samples collected from these babies after eight months of age were negative for HIV-IgA. There is a significant correlation (r=0.93; p<0.005) between decline of HIV-IgA antibodies (expressed as a OD/CO ratio) and the babies' age. The predictive value of a positive result or a negative result after 8 months of age is 100%. The specificity of this assay when evaluated for babies born to seronegative women is 100%.

Conclusion: These studies present evidence for transplacental HIV-specific IgA antibodies in babies of HIV-infected mothers. Loss of these antibodies in 100% of uninfected babies after 8 months of age and its continued presence in infected babies makes this test useful in the diagnosis of HIV infection in areas where other serological tests are not reliable.