Identification of a 33 kDa antigen associated with an adhesive and colonizing strain of Vibrio cholerae El Tor and its role in protection.

Proteins from the cell-free lysates of the wild-type strain KB207 of Vibrio cholerae El Tor and the isogenic non-adhesive mutant CD11 were analysed by native and denaturing polyacrylamide gel electrophoresis. A protein of 33 kDa present in KB207 was absent from CD11. Antiserum to the surface antigens of KB207 was absorbed with CD11. Antibodies remaining in the serum after absorption reacted to KB207 but not to CD11 as judged by slide agglutination, double gel diffusion and dot blot ELISA. Antibodies in the absorbed serum inhibited adherence of KB207 to rabbit intestinal mucosa and colonization in an infant mice model. The 33 kDa protein was isolated from KB207 by immunoaffinity chromatography. Antibodies present in the absorbed serum were used as ligand. The 33 kDa antigen was immunogenic and conferred protection in the rabbit ileal loop model. Combined administration of 33 kDa protein and B-subunit of cholera toxin offered full protection.