Immune response against a cross-reactive epitope on the heat shock protein60 homologue of Helicobacter pylori

We previously established a monoclonal antibody (MAb), designated H9, which reacts with the heat shock protein 60 (HSP60) homologue of Helicobacter py lori as well as with other bacterial and human HSP60s. To determine the imp ortance of a cross-reactive epitope on H. pylori HSP60 in H. pylori immunop athogenesis, me performed (i) mapping of an epitope on H. pylori HSP60 reco gnized by the H9 MAb, (ii) analysis of immunoglobulin G responses of patien ts with or without H. pylori infection to its epitope region, and (iii) stu dies of the protective effect of immunization with its epitope region on H. pylori infection in mice. The epitope recognized by the H9 MAb was mapped to the sequence of amino acids 189 to 203 (VEGMQFDRGYLSPYF) on the H. pylor i HSP60 molecule. It was confirmed that the synthesized peptide designated pH9 was recognized by the H9 MAb. Enzyme-linked immunosorbent assay analysi s showed that patients with H. pylori infection (n = 319) had significantly lower titers of pH9 antibody than did uninfected patients (n = 200) (P < 0 .001), but this was not the case with purified H. pylori HSP60 recombinant Escherichia coli GroEL, or recombinant human HSP60. In C57BL/6 mice immuniz ed with the pH9 peptide with Freund's complete adjuvant (PCA), the number o f H. pylori organisms colonizing the stomach was significantly lower than t hat in mice immunized with pCont plus FCA (P < 0.0001) or FCA only (P < 0.0 05). The results suggest that the immune response to the cross-reactive epi tope (pH9 region) on H, pylori HSP60 is unique and might be associated with protection against H. pylori infection.