Construction of Enkaryotie Expression Plasm ids of CSFV E2 Gene and the Study on DNA Vaccine

Four kinds of eukaryotic expressing plasmids of classical swine fever virus (CSFV) E2 gene, either containing or lacking the signal sequence and transmembrane region sequence, were constructed. The antibodies against CSFV were induced after immunization of mice by intramuscular (IM) injection with the plasmids of E2 gene with a signal sequence, pcDST and pcDSW, but not with the plasmids of E2 gene lacking a signal sequence, pcDWT and pcDWW. The level of antibodies elicited by pcDSW lacking transmembrane region sequence was higher than that elicited by pcDST with transmembrane region sequence. The results indicated the plasmid expressing a secreted antigen may be more efficient for induction of immune response when administered by IM injection than that expressing non secreted antigen. Immunization with pcDSW could protect rabbits against challenge with at least 10 MID hog cholera lapinized virus (HCLV) and protect pig from the challenge of lethal dose of CSFV strain, Shimenmen.