High expression of the nonstructural 1 genes of Japanese encephalitis virus (JEV) strain SA14-14-2 in E.coli and the antigenicity analysis of its expressed products / 解放军医学杂志

ABSTRACT

Objective To construct prokaryotic expression vector carrying Japanese encephalitis virus (JEV) NS1 gene, and to express the vector in E. coli, so to lay a foundation for the further development of JEV early diagnosis kit. Methods The NS1 gene was amplified by RT-PCR, the target gene and prokaryotic expression plasmid pET28a(+) were digested by BamH I and Hind Ⅲ respectively. The target gene was then purified by DNA extraction kit. A 1∶3 molar ratio of vector: insert DNA ligated with T4 DNA ligase to construct the recombinant plasmid pET28a(+)-NS1. The ligated products were transformed into E. coli BL21 (DE3) and the colonies were selected on LB medium with karamycin. After cultivation, positive colonies were picked out and the recombinant plasmid were identified by endonuclease digestions, PCR rand sequencing. The target protein was expressed with induction of IPTG. The expressed proteins mentioned above were then identified and analyzed by SDS-PAGE and Western-blotting respectively. Results The sequencing results of amplified products showed that JEV-NS1 RNA fragments were about 1 300bp in length which were similar as respected. Compared with the published sequence of SA14-14-2 with Blast, the homology of the nucleotide sequence was 100%. The molecular weight of expressed protein was about 45kD, the result of Western blotting proved the specific antigenicity of the protein. Conclusion The specific JEV nonstructural protein 1 is expressed in E. coli successfully and shows high specificity to the antibody. The stable expression of the protein and the analysis of its antigenic specificity provide foundation to develop the early stage diagnosis kit.