cholera toxin b subunit (ctxb) is a homopantameric, nontoxic subunit of cholera toxin that is responsible for its binding to the cell and has been known as a mucosal adjuvant for vaccines that could increase homoral and mocusal immunity response. in this work, the ctxb gene was fused to the stxb gene from shigella dysenteriae type i a vaccine antigen candidate against this pathogen, by a nonfur...