Expression and Purification of a Recombinant Enterotoxin Protein Using Different E. coli Host Strains and Expression Vectors.

Infection by Enterotoxigenic Escherichia coli is a common cause of diarrhea in animals. The development of vaccines against enterotoxins can effectively control the infection. We have previously constructed a recombinant antigen SLS fused by STa, LTB and STb enterotoxin and it showed a high immunogenicity in mice. Herein, we evaluated the expression of SLS in three different E. coli cells with corresponding plasmids. SLS proteins expressed in E. coli BL21 (DE3) and Rosetta-gami B (DE3) were aggregated as inclusion bodies, and the proteins solubility were not obviously promoted in low temperature combined with adjustment of inducer concentration. In contrast, SLS protein with maltose-binding protein (MBP) yielded from TB1 (DE3) cells were partially soluble. After increasing the IPTG concentration in the medium up to 2 mM and incubating at 37 ℃ for 4 h, the soluble protein yield reached the highest level (4.533 mg/0.2 L culture), which was significantly higher than the expression of SLS protein in Rosetta-gami B (DE3) (P < 0.05). Therefore, the TB1-pMAL expression system can be used for mass extraction and purification of SLS antigen prior to measuring its immunogenicity in pregnant mammals.