Nonlipopolysaccharide protective antigens shared by classical and El Tor biotypes of Vibrio cholerae

The prophylactic significance of the nonlipopolysaccharide (non-LPS) antigens of Vibrio cholerae was investigated further with use of the infant mouse cholera model. Of 16 strains examined to date, 12-including eight recent field isolates of both biotypes and both common serotypes-express common non-LPS protective antigens. The exceptional strains are four old isolates of El Tor biotype, the outer membrane proteins of which are not atypical when analyzed by immunoblotting. The protective activities of antibodies to the shared non-LPS components correlated with their capacities to inhibit the in vitro attachment of Vibrio organisms to isolated murine enterocytes.