HIV-1 specific immunoglobulin A antibodies as an effective marker of perinatal infection in developing countries.

HIV-1 specific IgA antibody testing using commercially available reagents was evaluated at birth to 15 months in a group of infants born to HIV-seropositive South African women. Following IgG depletion of serum samples, 33/35 (94 per cent) of the infected infants and 3/99 (3 per cent) of the uninfected infants showed positive IgA reactivity. Sensitivity at birth was 24 per cent and improved with age; 82 per cent at 3 months, 87 per cent at 6 months and 94 per cent at 12 months. The overall positive and negative predictive values were 92 and 98 per cent, respectively. An evaluation of IgA and PCR in a subsample of infants indicated a better sensitivity of PCR within 3 months of birth, but IgA detection offered a higher overall sensitivity (87 v. 83 per cent) and specificity (91 v. 85 per cent). No significant difference in IgA level was observed between transmitting mothers and non-transmitting mothers. A moderate correlation existed between IgA level in the infant and the cumulative morbidity score, however a stronger association was observed between high IgA levels in the infected infant and rapid disease progression. The viral specific IgA assay is a simple, reliable and cost-effective diagnostic and prognostic test for perinatal HIV infection in developing countries.