Baculovirus-mediated gene transfer has been developed as a vaccine design strategy against a number of diseases without apparent viral replication. However, it has been hampered by complement-dependent inactivation, thus hindering the in vivo application of baculovirus. A variety of approaches have been exploited to bypass the complement system in the serum. In this study, we constructed and screened a series of baculovirus vectors displaying complement interfering factors, of which a baculovirus vector displaying swine IgG1 Fc (pFc) showed the highest complement antagonism (75.6%). Flow cytometry analysis of transduced cells demonstrated that the baculovirus display of pFc had a significant increase in transduction efficiency and transgene expression of reporter genes. On this basis, a VSV-G-pseudotyped with swine IgG1 Fc surface displayed baculovirus vector was developed to express the classical swine fever virus (CSFV) E2 gene. The translational enhancers Syn21 and P10UTR were incorporated to improve the antigen expression. The E2 gene was efficiently expressed in both insect and mammalian cells. Pigs immunized with this recombinant baculovirus developed high levels of E2-specific antibody, CSFV-specific neutralizing antibody and IFN-γ-secreting cellular immune responses. These results demonstrate that the strategy of surface-displaying swine IgG1 Fc has a great potential to improve the efficiency of baculovirus-vectored vaccine for CSFV and other swine pathogens.

Porcine deltacoronavirus (PDCoV) causes diarrhea and vomiting in neonatal piglets worldwide and has the potential for cross-species transmission. Therefore, virus-like particles (VLPs) are promising vaccine candidates because of their safety and strong immunogenicity. To the best of our knowledge, the present study reported for the first time the generation of PDCoV VLPs using a baculovirus expression vector system, and electron micrograph analyses revealed that PDCoV VLPs appeared as spherical particles with a diameter similar to that of the native virions. Furthermore, PDCoV VLPs effectively induced mice to produce PDCoV-specific IgG and neutralizing antibodies. In addition, VLPs could stimulate mouse splenocytes to produce high levels of cytokines IL-4 and IFN-γ. Moreover, the combination of PDCoV VLPs and Freund’s adjuvant could improve the level of the immune response. Together, these data showed that PDCoV VLPs could effectively elicit humoral and cellular immunity in mice, laying a solid foundation for developing VLP-based vaccines to prevent PDCoV infections.

Porcine deltacoronavirus (PDCoV) is a newly emerging coronavirus that causes severe diarrhea and dehydration in newborn piglets, and can infect multiple an

Background : Canine parvovirus (CPV) is now recognized as a serious threat to dog industry worldwide. Vaccination remains the principal tool to control CPV infection. However, due to low yield, production of VP2 protein of CPV in baculovirus expression system remains challenging. The aim of this study was to increase the VP2 protein production by using a improved baculovirus expression system (Multibac) and evaluate the immunogenicity of the purified VP2 protein in mice. Results: The results showed that CPV VP2 protein was successfully expressed in the improved baculovirus expression system efficiently. A high level of expression of the full length VP2 protein was achieved using our modified system. The recombinant virus carrying two copies of VP2 showed the highest expression level, with a productivity of 186 mg/L, which is about 1.4-1.6 fold that of the recombinant viruses carrying only one copy. The purified protein could react with Mouse anti-His tag monoclonal antibody and Rabbit anti-VP2 polyclonal antibody with good reactogenicity. The mice were then immunized with purified full length VP2 protein to evaluate its immunogenicity. After vaccination, VP2 protein could induce the mice produce high level of hemagglutination inhibition antibodies. Conclusions: Full length CPV VP2 protein was successfully expressed at high level and purified efficiently. And it stimulated mice to produce high level of antibody. The full length VP2 expressed in this study could be used as a putative economic and efficient subunit vaccine against CPV infection.