Immune Response against a Cross-Reactive Epitope on the Heat Shock Protein 60 Homologue ofHelicobacter pylori

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Abstract
We previously established a monoclonal antibody (MAb), designated H9, which reacts with the heat shock protein 60 (HSP60) homologue ofHelicobacter pylorias well as with other bacterial and human HSP60s. To determine the importance of a cross-reactive epitope onH. pyloriHSP60 inH. pyloriimmunopathogenesis, we performed (i) mapping of an epitope onH. pyloriHSP60 recognized by the H9 MAb, (ii) analysis of immunoglobulin G responses of patients with or withoutH. pyloriinfection to its epitope region, and (iii) studies of the protective effect of immunization with its epitope region onH. pyloriinfection in mice. The epitope recognized by the H9 MAb was mapped to the sequence of amino acids 189 to 203 (VEGMQFDRGYLSPYF) on theH. pyloriHSP60 molecule. It was confirmed that the synthesized peptide designated pH9 was recognized by the H9 MAb. Enzyme-linked immunosorbent assay analysis showed that patients withH. pyloriinfection (n= 349) had significantly lower titers of pH9 antibody than did uninfected patients (n= 200) (P< 0.001), but this was not the case with purifiedH. pyloriHSP60 recombinantEscherichia coliGroEL, or recombinant human HSP60. In C57BL/6 mice immunized with the pH9 peptide with Freund's complete adjuvant (FCA), the number ofH. pyloriorganisms colonizing the stomach was significantly lower than that in mice immunized with pCont plus FCA (P< 0.0001) or FCA only (P< 0.005). The results suggest that the immune response to the cross-reactive epitope (pH9 region) onH. pyloriHSP60 is unique and might be associated with protection againstH. pyloriinfection.