[Simultaneous expression of CS3 colonization factor antigen and LT-B/ST fusion enterotoxin antigen of enterotoxigenic Escherichia coli by attenuated Shigella flexneri 2a].

Enterotoxigenic Escherichia coli (ETEC) causes watery dehydrating diarrhea in infants in developing countries, and is the most common cause of travelers diarrhea. It has been known that the colonazition factor antigens (CFAs) and enterotoxins are important virulence factors of ETEC, and these two kinds of proteins should be included in any effective vaccine against ETEC. In this study, a host-plasmid lethal balancing system was constructed based on asd gene in an avirulent strain of S.flexneri to express CS3 antigens and the fusion LT-B/ST enterotoxins of Escherichia coli. Both of these antigens were expressed steadily in the S. flexneri vector without any antibiotic markers. Antibodies against CS3, LT, ST and LPS of Shigella were detected in sera of mice that were immunized with recombinant bacteria either oragastrically (o.g.) or intranasally (i.n.). SIgA against CS3 and enterotoxins were detected simultaneously in feces of mice. This work is helpful for constructing multivalent recombinant vaccine for prevention of bacterial diarrhea.