Construction and immunogenicity of pseudotype baculovirus expressing Toxoplasma gondii SAG1 protein in BALB/c mice...

Toxoplasma gondii is a protozoan parasite causing toxoplasmosis to almost one-third of population all over the world. One of the most efficient ways to control this disease is immunization. However, so far, there is no effective vaccine available against this pathogen. Recently, a baculovirus pseudotype with vesicular stomatitis virus G protein (Bac-VSV-G) was found to efficiently transduce and express transgenes on mammalian cells, so it was considered as an excellent expressing vector. In this study, the value of Bac-VSV-G in delivering T. gondii antigen was investigated. T. gondii SAG1 gene was cloned into Bac-VSV-G, and recombinant baculovirus BV-G-SAG1 was obtained. Indirect immunofluorescence test showed BV-G-SAG1 was efficiently transduced and expressed in pig kidney cells. Then BALB/c mice were immunized with BV-G-SAG1 at different doses (1 x 10(8), 1 x 10(9), and 1 x 10(10)PFU/mouse) and challenged with T. gondii RH strain tachyzoites after immunization. The levels of specific T. gondii antibody, interferon (IFN)-gamma, IL-4, IL-10 expression and release, and the survival rate of treated mice were evaluated. Compared with the mice immunized with DNA vaccine (pcDNA/SAG1) encoding the same gene, BV-G-SAG1 induced higher levels of specific T. gondii antibody and (IFN)-gamma expression with dose-dependent manner and the survival rate of mice with BV-G-SAG1 was significantly improved. These results indicated that pseudotype baculovirus-mediated gene delivery can be utilized as an alternative strategy to develop new generation of vaccines against T. gondii infection.