Oral immunization of mice with a glycoconjugate vaccine containing the O157 antigen of Escherichia coli O157 : H7 admixed with cholera toxin fails toelicit protection against subsequent colonization by the pathogen

It has been postulated that a humoral immune response directed against the O157 antigen of Escherichia coli O157:H7, and expressed in the intestine, m ight afford protection from colonization and consequent infection by this e nteric pathogen. The present study was conducted to determine whether such an immune response can be experimentally generated in mice. To this end, mi ce were orally immunized with a glycoconjugate vaccine consisting of horse serum albumin and the O157 polysaccharide admixed with the mucosal adjuvant , cholera toxin. Mice consistently developed robust local and systemic immu ne responses to the cholera toxin adjuvant, but were far from uniformly rea ctive to the test vaccine. Moreover, vaccinated mice were as susceptible to transient intestinal colonization following challenge with an isolate of E . coli O157:H7 as unvaccinated control mice. These results indicate that th is vaccination approach is unlikely to be straightforward in target bovine or human hosts.