Helicobacter pylori infection elicits a local and systemic immune response against bacterial antigens, including a heat-shock protein of 60 kDa (HSP60). The homology between microbial and human HSP suggests that the immune response to bacterial HSP may play a role in the pathogenesis of autoimmune disorders. Since gastric involvement and H. pylori have been reported in Sjögren's syndrome (SS), we investigated the prevalence of antibodies against H. pylori and its specific HSP60 in sera from patients with SS.
Four groups of patients were studied. Group 1, 34 patients with primary SS (pSS); Group 2.19 patients with secondary SS; Group 3, 22 patients with various autoimmune diseases and Group 4, 43 healthy controls. Serum IgG levels against HSP60 were determined by an ELISA using recombinant full length HSP60 expressed in Escherichia coli, as the antigen. To confirm the H. pylori infection, a commercial ELISA was used.
Out of 34 patients in Group 1, 27 (79.4%) and 30 (88.2%) had antibodies against H. pylori and its HSP60, respectively. The prevalence was significantly higher than that found in Group 3 (18.2%, p < 0.0001 and 27.3%, p < 0.0001) and in Group 4 (48.8%, p < 0.005 and 37.2%, p < 0.0001) but not than that of Group 2 (48.8% and 37.2%). If the prevalence of patients either positive or negative for both antibodies was considered, a statistically significant difference was found between Group I and respectively Groups 3 and 4.
The hypothetical role of HSP60 in the development of the immune response both in pSS and secondary SS seems strictly linked to the prevalence rate of H. pylori infection.