Abstract: For preventing the outbreak of viral ulcerative syndrome in largemouth bass（Micropterus salmoides）in Guangdong province,the ORF of major capsid protein（MCP）gene,as target antigen protein gene,from largemouth bass ulcerative syndrome virus（LBUSV）was inserted in vector pBV220,then transformed into Escherichia coli DH5α,and the recombinant engineering bacterium for expressing MCP was constructed. Following 42℃ temperature inducement and SDS-PAGE analysis,the recombinant bacterium was detected to produce a special expression protein with molecular weight about 51 kD,and the proportion of recombinant MCP protein was nearly 30% of total bacterial protein. After washed,purified,dissolved,renatured and dialyzed,the purity of the recombinant protein reached over 90%. The purified protein was mixed and emulsified with incomplete Freund's adjuvant,then was injected in largemouth bass as vaccine. The immunized fish were challenged with LBUSV,and the highest relative percentage of survival reached 67.7% after 20 days. The results indicate that the MCP of LBUSV has the immunogenicity and can be selected as candidate protein for recombinant vaccine.

Key words: largemouth bass（Micropterus salmoides）, ulcerative syndrome virus, major capsid protein, prokaryotic expression, immune effect