Direct identification of class II histocompatibility DR proteins in preparations of human T-cell lymphotropic virus type III.

Class II histocompatibility DR antigen alpha and beta chains were isolated from preparations of human T-cell lymphotropic virus type III grown in human H-9 cells. The proteins were purified by reversed-phase high-pressure liquid chromatography and identified by direct N-terminal amino acid sequence analysis of each chain. The purified DR alpha chain had an N-terminal amino acid sequence identical to the known sequence of human DR alpha chain through the first 37 residues. The N-terminal amino acid sequence of the purified DR beta chain was identical to that of human DR4 beta chain. The DR alpha and beta chains appeared to be identical to the p34-36K and p30-32K proteins, respectively, concentrated in immunostimulatory complexes prepared from unfractionated virus and were the major immunogens in these complexes. These proteins represent a ready source of antigens which can cause false-positive enzyme-linked immunosorbent assay reactions in individuals previously exposed to allogenic histocompatibility antigens. The removal of the DR chains from virus preparations by use of available monoclonal antibodies or other means should result in a lower rate of initial false-positive enzyme-linked immunosorbent assay reactions.