Comparison of two recombinant systems for expression of cholera toxin B subunit from Vibrio cholerae

The aim of this study was to assess the production of recombinant cholera toxin B subunit (rCTB) protein in two different expression systems (pAE_ctxB and pQE_ctxB constructs) in Escherichia coli BL21 (DE3).

The ctxB fragment was amplified from Vibrio cholerae O 1 ATCC14035 and cloned in pGETM-T easy vector after which it was transformed to E. coli Top 10F' and grown on LB-ampicillin agar medium. Sequence analysis confirmed the complete ctxB gene sequence in the construct which was further subcloned to pQE-30 vector. The construct was subsequently transformed to E. coli M15 (pREP4). The recombinant pAE_ctxB and pQE_ctxB were transformed to competent E. coli BL21 (DE3) cells to express CTB protein.

Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the maximum expression of rCTB in both systems at 5 h after induction and western blot analysis confirmed the presence of recombinant CTB in blotting membranes.

Expression of rCTB in pAE_ctxB construct was more efficient (15-fold) than pQE_ctxB, and it seems that Lac UV5 in E. coli BL21 (DE3) is more compatible with the former construct. This expression system can be used to produce recombinant CTB in high yield which may enable us to study the oral tolerance or mucosal adjuvant properties of rCTB using animal models.