Characterization of an immunoreactive species-specific 19-kilodalton outer membrane protein from Helicobacter pylori by using a monoclonal antibody.

Immunoblotting experiments on hyperimmune rabbit serum and sera from patients with Helicobacter pylori gastritis showed a consistent antibody response to a 19-kDa outer membrane protein antigen. A monoclonal antibody, designated HP 40, which reacted by Western immunoblotting with this protein was produced. It was shared by all H. pylori strains tested (D 273, NCTC 11637, and 24 wild strains) but not by the thermophilic Campylobacter species, Campylobacter fetus, Helicobacter mustellae, or Helicobacter fennelliae. Immunogold staining suggested that the 19-kDa antigen was exposed on the outer surface of the bacteria. Its functional role and effectiveness as a serological diagnostic tool are under study.