Frequent detection of HIV- and IgG-specific IgM and IgA antibodies in HIV-positive cord-blood sera: fine analysis by western blot.

Cord-blood sera of 36 babies born to HIV-positive mothers in Switzerland were tested for immunoglobulin (Ig) M or IgA by HIV Western blot. IgM was found in 28, and IgA in 19 of unabsorbed sera. Preabsorption with immobilized protein A or G was used to remove IgG, which allowed differentiation between HIV-specific and IgG-specific IgM or IgA. Protein G proved superior and showed that 30% of 23 sera had HIV-specific IgM, while 48% had HIV-specific IgA. HIV-specific IgM and/or IgA was found in 13 out of 21 cases (62%); four out of 21 (19%) had both. HIV-specific IgM reacted most frequently with pol or env proteins, while HIV-specific IgA reacted more frequently with gag than pol; no IgA were directed against env proteins. IgG-specific IgM and IgA, mostly at gag bands, were present in 83 and 38%, respectively. Thus, a large percentage of children born to HIV-positive mothers have HIV-specific IgA and/or IgM which can be distinguished from IgG-specific IgA or IgM, which is also present in the majority of such children. Future studies will have to show whether these antibodies are of diagnostic relevance.