Baculovirus surface display of NS3 nonstructural protein of classical swine fever virus

Classical swine fever virus (CSFV) causes significant losses in the pig industry in many countries. NS3 proteins of CSFV, which include serine protease and RNA helicase/nucleotide triphosphatase (NTPase) activities, are multifunctional proteins involved in polyprotein processing and viral replication. Previous reports showed that NS3 protein can induce apoptosis in host cells that present cytopathic effects (CPE). Baculovirus/insect cell systems are used widely for recombinant protein production. In this study, one recombinant baculovirus BacSC-NS3 expressing histidine-tagged NS3 with the transmembrane domain (TM) and cytoplasmic domain (CTD) derived from baculovirus envelope protein gp64 of baculovirus was constructed. After infection, NS3 was expressed and anchored to the plasma membrane of Sf-9 cells, as demonstrated by Western blot assay and confocal microscopy. Immunogold electron microscopy demonstrated that the NS3 glycoprotein successfully displayed on the baculoviral envelope. Animal vaccine tests showed that recombinant baculovirus BacSC-NS3 elicited significantly higher NS3 antibody titers in the treated mouse models than the control group. This report demonstrated the potential of NS3-pseudotyped baculovirus expression of NS3 protein successfully.