Expression of optimized gene of Enterotoxigenic Escherichia coli CFA/I major subunit

Enterotoxigenic Escherichia coli is considered as the most important agent of children diarrhea and mortality in developing countries. This bacterium causes 300-600 thousands of deaths in the children under 5 years of age per year. With difficulties in treatment as well as its wide prevalence, designing an effective vaccine against this microorganism is the objective of world Health Organization (WHO). The CfaB protein as immunogen and major subunit of fimberia has a critical role in the bacterial attachment to small intestine epithelium and the produced antibody against this protein can prevent attachment of bacterium to epithelial surface. Hence, this molecule alone or with other virulent factors has been considered by many researchers in vaccine designing. In this study, expression of colonization factor B with the aim of studying the immunogenesity of this protein as a component of vaccine candidate was performed.

cfaB gene was amplified by PCR and cloned into pET28a and its expression was evaluated. Since there was no expression, which was due to presence of rare codon, the cfaB gene was again cloned into pET28a using codon bias in E.coli and subsequently expressed.

Presence of a 20KD band on SDS-PAGE gel indicated the expression of CfaB protein, which was later confirmed by immunoblotting with anti-His tag and anti CfaB antibodies and purified on Ni-NTA column.

Codon optimization and expression in heterologous hosts is a useful approach for obtaining large quantities of recombinant protein.