DIVERSITY OF THE IMMUNODOMINANT EPITOPE OF GP41 OF HIV-1 SUBTYPE-O AND ITS VALIDITY FOR ANTIBODY DETECTION

The immunodominant regions of the gp41 from 13 HIV-1 subtype O strains from Cameroon, 11 from France and one from Germany were sequenced. Th e amino acid sequences were compared to those of the 3 published HIV-1 subtype O isolates, ANT70, MVP-5180 and VAU, All HIV-1 subtype O isol ates had a very conserved amino acid sequence in this region and showe d a subtype O specific structure. Within the cysteine loop there was a positive charge of two basic amino acids, arginine and lysine. Only t wo strains (CM.6778 and CM.8161) showed an acidic amino acid in this l oop. None of the isolates showed the same amino acid sequence in this immunodominant region. A 25 residue peptide from the immunodominat dom ain of gp41 of the MVP-5180 strain was synthesized, cycled to form the cysteine-loop and coated to microtiter plates. Antibody binding was d etected by indirect ELISA using an enzyme labeled anti-human IgG. Out of 111 anti-HIV-1 positive specimens, collected mainly from Cameroonia n HIV infected patients, only 10 were not reactive in this assay. The 42 anti-HIV-1 subtype O positive specimens gave all a reaction above c ut off. Despite the diversity found in the amino acid sequences within the 25 isolates a peptide-based indirect ELISA representing the immun odominant epitope of the strain MVP-5180 successfully detected ah the anti-HIV-O sera so far tested, pointing to the importance of adding su ch a peptide for correct identification of HIV-1 subtype O infected pa tients, while some assays without HIV-O specific antigens partially fa il to detect all anti-HIV-O specimens. (C) 1997 Elsevier Science B.V.