Abstract: The antigenicity of the p72 protein of African swine fever virus (ASFV) was compared with that of a truncated p72 protein (p72s) to provide experimental basis for ASFV specific antibody detection. The p72 and p72s proteins were expressed by Escherichia coli expression system, and the expressed protein was identified by Western blotting and Liquid chromatography mass spectrometer (LC-MS/MS), and the epitopes of the protein were analyzed. Mice were immunized with the purified intact p72 protein or p72s protein, respectively, and the immunogenicity of p72 and p72s proteins was compared. The immunoreactivity of the p72 and p72s proteins with ASFV-positive serum was evaluated by ELISA and Western blotting.Both recombinant p72 and p72s proteins were expressed as inclusion bodies with molecular weights of 76 and 42 kDa, respectively, which were consistent with the expected molecular weight. The coverage of predicted amino acid sequences of p72 and p72s by the hydrolysate peptide of the expression proteins was 89.3% and 88.39%, respectively, which included 27 and 17 epitopes. After mice were immunized with p72 or p72s for three times, the serum specific antibody titers were in the range of 1∶200 to 1∶25 600 and 1∶12 800 to 1∶409 600, respectively. Among 108 swine sera, 78 (72.2%) and 85 (78.7%) positive sera were detected by ELISA based on p72 and p72s proteins with a good consistency (kappa=0.826, P=0.016). Seven of the 10 ASFV positive sera detected by Western blotting reacted with p72 protein, and all of them reacted with the p72s protein. The truncated p72 protein has better antigenicity than the intact p72 protein, and it is more suitable for ASFV antibody detection.

Key words: African swine fever virus, intact/truncated p72 protein, prokaryotic expression, antigenicity