Human immune response to the 18-kDa outer-membrane antigen of Vibrio cholerae

The serum IgG response of human volunteers challenged with Vibrio cholerae O1 was analysed for reactivity to V. cholerae O1 outer-membrane antigens by enzyme-linked immunosorbent assay (ELISA) and the immunoblot technique. Purified outer-membrane antigen preparations from vibrios grown in low-iron conditions were separated by SDS-PAGE. Specific immunoblot reactions of human sera showed that an 18-kDa antigen, cholera protective antigen, was the major antigen with which sera reacted. ELISA revealed an increase in antibody to the 18-kDa antigen in nine of 10 challenged volunteers. This response was independent of the biotype and serotype of the V. cholerae O1 challenge strain. Cholera protective antigen appears to be one of the major outer-membrane antigens involved in the human immune response to infection with V. cholerae.