Construction And Efficacy Evaluation Of Codon-optimized DNA Vaccines Expressing The E2 Gene Of Classical Swine Fever Virus

The envelope glycoprotein E2 of Classical swine fever virus (CSFV) is responsible for the elicitation of neutralizing antibodies. It is often used in developing new-type vaccines, clinical diagnostic reagents and immunopathological mechanism study of the virus. In this study, we rewrited the E2 gene of CSFV Shimen strain with codons prefered by mammalian cells. Full-length codon-optimized E2 gene, transmembrane region (TMR)-deleted codon-optimized E2 gene, and full-length wild-type E2 gene were each cloned into the eukaryotic expression vector pcDNA3.1(+), generating recombinant plasmids pcDoptiE2, pcDoptiE2delTMR and pcDwtE2. In vitro transient expression experiment showed that E2 gene can be expressed in 293T cells transfected with the plasmids, as demonstrated by indirect immunofluorescent antibody test. To verify the potential of the three DNA plasmids as candidate marker vaccines against CSFV, we immunized rabbits three times with the the plasmids at a 3-week interval. The results showed that codon-optimized TMR-deleted E2 gene expressing DNA vaccine peDoptiE2delTMR induced robust antibody titers in rabbits (n=5), whereas the other two failed to induce antibody response in rabbits (n=5). We conclude that it is feasible to develop a DNA vaccine based on codon-optimized E2 gene of CSFV, and the removal of TMR can result in enhanced efficacy of the DNA vaccine.