Generation Of A BacMam Virus Expressing The E2 Protein Of Classical Swine Fever Virus And Its Immunogenicity In A Mouse Model

Classical swine fever (CSF) is a highly contagious and lethal disease of pigs caused by classical swine fever virus (CSFV), which is one of OIE listed diseases. Vaccination has been an important measure to prevent CSF. At present, the most frequently used vaccine in china is the Chinese lapinized attenuated vaccine (C-strain), which can induce complete protection against CSF. A great disadvantage of this vaccine is that vaccinated animals cannot be distinguished from those infected with wild-type CSFV. It is urgent to develop novel CSFV vaccines capable of inducing rapid protection combined with the possibility to differentiate infected from vaccinated animals.Recombinant baculovirus vectors containing mammalian cell-active promoter elements (also known as BacMam virus) have been used successfully for gene delivery into mammalian cell lines without any apparent viral replication. Since the initial discovery of an efficient gene transduction into mammalian cells by BacMam virus, numerous efforts have been made to harness baculovirus as a vector for gene therapy and vaccine development. As a vaccine vector, baculovirus vectors have many particular advantages over others. So BacMam virus is very suitable for developing non-replicative vector vaccines.Our previous studies have demonstrated that the BacMam virus with an EGFP reporter gene under the control of the white spot syndrome virus (WSSV) ie1 promoter exhibited high transduction efficiency and high-level expression of the reporter protein in mammalian cells. To explore the potential of baculovirus-based vaccine against CSFV virus, in the present study, a baculovirus pseudotyped with the glycoprotein of vesicular stomatitis virus was used as vector to construct the recombinant baculovirus expressing CSFV E2 protein under the control of ie1 promoter from WSSV. The E2 gene was shown to be efficiently expressed in both insect and mammalian cells by detecting with indirect immunofluorescent assay and Western blot. Intramuscular injection of mice with the recombinant baculovirus resulted in the production of high-level CSFV-specific antibodies. Specific lymphoproliferative responses to the CSFV stimulation were induced in the splenocytes of the immunized mice as demonstrated by CFSE staining assay and WST-8 assay. This study indicates that the pseudotyped baculovirus-delivered gene can be a potential non-replicative vaccine against CSFV infection.