A CssA, CssB and LTB chimeric protein induces protection against Enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC), a major cause of diarrhea in children under 5, is an important agent for traveler's diarrhea. Heat-labile enterotoxin (LT) and colonization factors (CFs) are two main virulence mechanisms in ETEC. CS6 is one of the most prevalent CFs consisting of two structural subunits viz., CssA, CssB, necessary for attachment to the intestinal cells.

In the present research, a chimeric trivalent protein composed of CssB, CssA and LTB was constructed. The chimeric gene was synthesized with codon bias of E. coli for enhanced expression of the protein. Recombinant proteins were expressed and purified. Mice were immunized with the recombinant protein. The antibody titer and specificity of the immune sera were analyzed by ELISA and Western blotting. Efficiency of the immune sera against ETEC was evaluated.

Antibody induction was followed by immunization of mice with the chimeric protein. Pretreatment of the ETEC cells with immunized animal antisera remarkably decreased their adhesion to Caco-2 cells.

The results indicate efficacy of the recombinant chimeric protein as an effective immunogen, which induces strong humoral response as well as protection against ETEC adherence and toxicity.