Study of predominant bacterial antigens triggering antibody response in Salmonella reactive arthritis: apropos of a case.

Reactive arthritis (ReA) is a sterile arthritis triggered by distal mucosal infection, which suggests a contribution from bacterial products. The pathogenesis of ReA is unclear. There are no international standards for the serological methods used to confirm ReA. In the present work, we analyzed the predominant bacterial component that triggered an immune response in a 24-year-old woman with acute ReA. The candidate bacterial trigger was investigated by measuring the antibacterial antibodies (all immunoglobulin classes and IgA) to Salmonella enteritidis, Shigella flexneri and Yersinia enterocolitica. ELISA for Salmonella gave a positive result. To identify the bacterial component triggering ReA, antibodies to crude lysate, outer membrane proteins (OMP), cytosolic fraction, supernatant proteins and lipopolysaccharide of S. enteritidis were analyzed in sera and synovial fluid (SF) by ELISA, dot blot, and Western blot. Among the antigen preparations, the antibody response to OMP was dominant in both serum and SF; a strong reaction to seven OMP bands (50-21 kDa) was observed. We concluded that OMP were the main bacterial antigens that trigged ReA in the reported case. Determining the triggering bacterial components in each case can help elucidate the precise causes of ReA and will contribute to the designing of a specific serological diagnostic method for this arthritis.