Salmonella landau as a live vaccine against Escherichia coli 0157 : H7 investigated in a mouse model of intestinal colonization

The present study was performed to assess the potential of a humoral mucosa l immune response directed against the O157 antigen of Escherichia coli O15 7:H7 to prevent intestinal colonization by the pathogen. To this end, mice were gavaged with inocula of Salmonella landau, a Salmonella strain that na turally expresses the O157 antigen. Salmonella landau was avirulent for mic e. Despite this, mice exposed to S. landau developed high titres of serum a nd coproantibodies against the O157 antigen. These mice, compared with cont rols, demonstrated some ability to resist transient intestinal colonization by an oral inoculum of an isolate of E. coli O157:H7. These findings sugge st that a local immune response directed against the O157 antigen might inc rease host resistance to this pathogen.