Antibodies to MHC Class II Peptides are Present in HIV‐1‐Positive Sera

Seventy‐five per cent of sera from HIV‐I‐infected individuals bind to the human B‐lymphoma cells bearing the major histocompatibility class II molecule in enzyme‐linked immunosorbent assay (ELISA). The binding is caused by the antibodies against the class II molecule present in the serum samples which prevent the interaction of murine anti‐HLA.DR monoclonal antibody with B lymphoma in FACS analysis. The three highly conserved amino acid sequences in α‐ and β‐ chains of the class II molecule and three homologous fragments in HIV‐1 gp120 and gp41 were identified by computer search and synthesized. Using these peptides it was demonstrated that 28–48% of HIV‐positive sera contain antibodies that cross‐react with the peptide of HIV‐I origin and with the peptide from the class II molecule as well.