Abstract: The study was aimed to highly express Cap protein of porcine torque teno virus type 2 in E.coli, and determine the optimal expression conditions and purify it. ORF1 gene was amplified by PCR and cloned into the prokaryotic expression vector pGEX-4T-1 to construct recombinant plasmid pGEX-4T-1-ORF1, which was identified by restriction and sequence analysis, then transformed into E.coli BL21(DE3) and expressed under the induction of IPTG. The expression product was identified by SDS-PAGE and Western blotting. The induction time, induction temperature and IPTG concentrations were optimized. Both PCR and restriction analysis proved that the recombinant plasmid was constructed correctly. The best induction condition was 37 ℃ for 5 h, whereas IPTG concentration had no significant impact on protein expression. The recombinant fusion protein pGEX-4T-1-ORF1 was approximately 80 ku in a form of inclusion body, which was recognized specially by mouse anti-GST monoclonal antibody. It was the first time to use cutting the gel slice’s method for purification of TTV2 Cap protein, which was cost-effective and convenient. Recombinant plasmid pGEX-4T-1-ORF1 was constructed and the Cap protein was highly expressed in E.coli which provided antigen for indirect ELISA and preparation of monoclonal antibodies.

Key words: porcine torque teno virus; Cap protein; prokaryotic expression; purification