Efficacy of Heterologous Vaccination Using Virus-Like Particles and Vaccinia Virus Containing MIC8 and AMA1 Proteins of Toxoplasma gondii.

Background:Toxoplasma gondii (T. gondii) infection causes serious diseases in immunocompromised patients and causes congenital toxoplasmosis in infants. T. gondii microneme protein 8 (MIC8) and apical membrane antigen 1 (AMA1) are essential proteins involved in parasitic invasion. Methods: In this study, we generated virus-like particles (VLPs) and recombinant vaccinia virus (rVV) containing MIC8 or AMA1 proteins. Vaccine efficacy was evaluated in mice (BALB/c) upon challenge infection with T. gondii ME49. Results: Intramuscular immunization with heterologous vaccines (rVV + VLPs; rVV for prime and VLPs for boost) elicited T. gondii-specific IgG antibody responses in mice. Four weeks after the boost, all mice were orally challenged with T. gondii ME49, and protective immunity was assessed. The responses of antibody-secreting cells for IgG2a and IgG2b and those of memory B cells and CD4+ and CD8+ T cells were higher in the rVV + VLP group than in the VLP + VLP group. The rVV + VLP group exhibited a significant reduction in cyst count in the brain. Conclusions: These findings indicate that heterologous vaccination with vaccinia viruses and VLPs improves vaccine efficacy.