EARLY DETECTION OF IGA SPECIFIC ANTIBODIES IN HIV-1-INFECTED CHILDRENBY PEPTIDE-ELISA AND PEPTIDE TIME-RESOLVED FLUORO-IMMUNOASSAY

The presence of specific IgA antibodies in sera from 25 infants born t o HIV-1 seropositive mothers was investigated by peptide-ELISA and pep tide time-resolved fluoro-immunoassay (TR-FIA). The infants had been m onitored at different times after birth for clinical signs and/or symp toms of HIV-1 infection and for detection of HIV-1 in lymphocyte cultu res. Serum samples had also been tested for HIV-1 IgG antibodies by co mmercial ELISA and Western blot and for p24 antigen. Eleven of 25 chil dren were then identified as infected. IgA detection was performed aft er rProtein G treatment to remove interfering IgG. In the infected gro up, IgA specific antibodies to a synthetic peptide representing a high ly conserved region of the transmembrane glycoprotein gp41 (env: 594-6 13) were detected in 27 (73%) out of 37 serum samples (9 of 11 childre n) by the peptide-ELISA test. IgA specific antibodies to the same pept ide were found in 30 (81%) sera (9 of 11 children) by the peptide-TR-F IA. Specific HIV-1 IgA antibodies were detected as early as 2 months o f age in serum samples from five out of seven children (71% sensitivit y) using peptide-ELISA and from six out of seven (86% sensitivity) by peptide-TR-FIA. Conversely, IgA specific antibodies to HIV-1 were abse nt in two infected children as well as in the sera of all uninfected c hildren tested during the follow up period. Since maternal IgA does no t cross the placenta, IgA detection in the serum of the infant is indi cative of HIV-1 infection. Indeed, the early demonstration of HIV-1 Ig A antibodies in infected infants shows that both peptide-ELISA and pep tide-TR-FIA can be used for an early diagnosis of HIV-1 infection.