Fusion of CtxB with StxB, Cloning and Expression of in Esherichia coli: A challenge for Improvement of Immune Response Against StxB

Abstract

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 <em>Shigella</em> <em>dysenteriae </em>type I a vaccine antigen candidate against this pathogen, by a nonfurin<em> </em>linker then ligated with pGEM vector and subcloned in the pET28a(+) as an expression vector . The CtxB-StxB fusion protein was expressed in Escherichia coli, and purified by a Ni-NTA resin column, then detected molecular weight and immunogenicity by SDS-PAGE and Western-blot. StxB has low molecular weight, so immune response against it is low, while CtxB is a potent mucosal adjuvant. In this method, the CtxB-StxB fusion protein was expressed in <em>Escherichia coli</em> in order to use its natural adjuvanticity of the CtxB which will enhance immune response against StxB, as well as, it will produce immune response against both shiga and cholera toxins.