Prokaryotic expression, purification and antigenicity analysis of African swine fever virus pK205R protein.

African swine fever is an acute, febrile and highly virulent porcine disease causing serious economic losses worldwide. The pK205R protein of the African swine fever virus (ASFV) is largely expressed in the early stages of infection, which has given the K205R gene extensive attention. In this study, the ASFV K205R was cloned and expressed in Escherichia coli BL21 (DE3). Expression of histidine-tagged pK205R with a molecular mass of 44 kDa was determined by 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis. Optimisation of culture conditions allowed induction of the recombinant protein with 0.4 mM Isopropyl β-D-thiogalactoside (IPTG) at 37°C for 2 h. The protein existed in cellular supernatant and was purified using a Ni-NTA resin column. The purified protein was used to immunize rabbits four times to enable the production of polyclonal antibodies, and the antiserum titre was detected by ELISA. The results showed that the purified pK205R can react with ASFV positive serum specifically by Western blotting. The pK205R had high antigenicity, which indicated that pK205R could be used as an antigen for detection of ASFV-specific antibodies in ELISA testing, and the recombinant protein could contribute to further research of the action and structure of pK205R.