Abstract:

【Objective】 Porcine circovirus type 2 (PCV2) is an important causative agent of postweaning multisystemic syndrome in pigs and capsid protein (Cap) encoded by ORF2 as the main structural protein is involved in the host immune protective response, so it is very important to identify the antigenic epitopes of PCV2 Cap. 【Method】 In this study, five monoclonal antibodies (MAbs) against recombinant PCV2-ORF2 Cap expressed by baculovirus system were generated and preliminary epitopes region was localized using the five MAbs after expression of truncated fragments from ORF2 gene in Echerichia coli system. Subsequently, peptides were synthesized to further accurately identify epitopes on the Cap. 【Result】 Of the five MAbs, four MAbs were against the same core epitope (26RPWLVHPRHRY36) verified by peptides mapping, locating in nuclear localization signal region at the N terminal of Cap. Besides, another MAb (1D2) could not react with the four truncated fragments only to react with the whole recombinant Cap, and it may be a conformational epitope based on its neutralizing effect against PCV2. 【Conclusion】 It was concluded that an epitope located in nuclear localization signal region of Cap was firstly reported, which will provide a basis for further studies on the functions of Cap as well as on the mechanism of Cap localization into nuclear.

Key words: porcine circovirus type 2, capsid protein, antigenic epitope, peptide mapping, nuclear localization signal