Abstract: Objective To express the MIIV nucleocapsid (N) gene with Bac-to-Bac baculovirus expression system. Method According to N gene sequence of MHV A59 strain in Genbank, a pair of specific primers was designed and synthesized. The ORF of N gene was amplified by RT-PCR, and then inserted into the transfer vehicle pFastbacHTa to obtain the recombinant transfer vectors pFastBHa-N,which was used to transform into E. coli DHlOBac, producing specific transposition with Bacmid to yield the recombinant shuttle vehicles, Bacmid-N. Then the Bacmid-N was further used to transfect Sf9 insect cells by lipofectin to generate recombinant baculovirus expressing N recombination protein. Results Recombinant baculovirus, rBN，was obtained. IFA and Western blotting detection confirnl ed that the gene had been expressed in sf9 cells, and the expression product could specially react to the sera of MHV. Conclusion The MHV N protein is expressed successfully by Bac-to-Bac baeulovirus expression system, which may lay foundation for development of diagnostic technique.

Key words: Mouse Hepatitis Virus, Nucleocapsid gene, Baculovirus expression