Abstract:

Objective To construct the prokaryotic expression vector of Coxsackievirus A16 （CA16） viral protein 1 （Vp1）， express it in Escherichia coli （E.coli） BL21， purify the protein， prepare rabbit polyclonal antibodies， and identify the immunoreactivity of the antibodies. Methods Bioinformatics online tools were used to predict the amino acid composition， conserved domains， secondary and tertiary structures of the Vp1 protein. The Vp1 gene of CA16 was amplified and cloned into the prokaryotic expression vector pET28a（+）. The pET28a-Vp1 was transformed into E.coli BL21， and the expression was induced using isopropyl β-D-thiogalactopyranoside （IPTG）. Western blotting method was used to identify the induced expression of Vp1 protein， and the induction time and temperature were optimized to improve the expression efficiency. Two female SPF New Zealand white rabbits were taken， and the purified recombinant protein Vp1 was used to immunize the rabbits to prepare rabbit anti-Vp1 protein polyclonal antibodies. The antibody titer was determined by ELISA method， and the immunoreactivity of the antibodies was identified by Western blotting method. Results The bioinformatics analysis results showed that the Vp1 gene encoded 297 amino acids， with a relative molecular mass of 33 046.39 and an isoelectric point of 8.32， belonging to a hydrophilic protein； in the secondary structure， α-helix accounted for 15.15%， random coil accounted for 67.68%， and extended strand accounted for 17.17%. Sequencing of the recombinant plasmid pET28a-Vp1 confirmed that the pET28a-Vp1 plasmid was correctly constructed. The Western blotting results showed that the target protein was expressed in the IPTG induction group at a relative molecular mass of 33 000， and the target protein was mainly expressed in inclusion bodies. The optimal induction conditions for protein expression were IPTG concentration of 0.4 mmol·L^-1， temperature of 16 ℃， and induction time of 20 h. The ELISA assay results showed that the titer of the rabbit polyclonal antibody was 1∶1 024 000. The Western blotting results showed that the Vp1 rabbit polyclonal antibody could bind to the viral Vp1 protein in the CA16-infected cells. Conclusion The polyclonal antibody against CA16 Vp1 is successfully prepared， and this antibody has significant binding characteristics to CA16 Vp1， which can be used for the diagnosis of enterovirus infection and the development of treatment methods.

Key words: Coxsackievirus A16, Viral protein 1, Prokaryotic expression, Polyclonal antibody, Escherichia coli