High level expression and purification of recombinant 3ABC non-structural protein of foot-and-mouth disease virus using SUMO fusion system.

The detection of antibody to non-structural protein (NSP) of Foot-and-mouth disease virus (FMDV) is the reliable diagnostic method for differentiating infected from vaccinated animals (DIVA). For this purpose, the detection of antibodies to non-structural 3ABC protein is suitable for identification of virus activity in the animals exposed to FMDV infection. However, large-scale production of recombinant 3ABC protein is challenging due to the formation of inclusion bodies in Escherichia coli and low yield due to protein aggregation during in vitro refolding. In this study, 3ABC gene was fused with SUMO (small ubiquitin-like modifiers) fusion system which significantly enhanced expression of recombinant 3ABC protein in E. coli. The solubility of the recombinant 6xHis-SUMO 3ABC fusion protein was improved by mild detergent treatment and purified through Ni-NTA chromatography under non-denaturing conditions which yielded 9 mg protein obtained from 1-L bacterial fermentation culture. The diagnostic potential of recombinant 3ABC protein was also tested by ELISA that provided reliable diagnostic performance (DSn = 92%, DSp = 94%) upon comparison with commercially available kit. The thermal stability of fusion protein was also tested which presented reliable performance at different temperatures. In conclusion, we presented SUMO fusion for the enhanced expression in E. coli and purification of active recombinant 3ABC protein using non-denaturing conditions without refolding steps. This protein can be used as a suitable diagnostic antigen to detect antibodies following FMDV infection.