Protective Efficacy Induced by Virus-like Particles Expressing Dense Granule Protein 5 of .

() causes severe disease in immunocompromised individuals and pregnant women, underscoring the urgent need for effective vaccines against toxoplasmosis. The dense granule protein 5 (GRA5) of plays a key role in parasitic cyst formation. This study evaluated the protective immune responses induced by a virus-like particle (VLP) vaccine expressing the -derived antigen GRA5 in a mouse model challenged with the ME49 strain of . GRA5 VLPs were generated using a baculovirus expression system, and VLP formation was confirmed by Western blotting and visualized using transmission electron microscopy. Mice were intranasally immunized with GRA5 VLPs three times at 4-week intervals to induce immune responses, followed by infection with ME49. Intranasal immunization with GRA5 VLPs induced parasite-specific IgG antibody responses in the serum and both IgG and IgA antibody responses in the brain. Compared to the non-immunized group, immunized mice exhibited significantly higher levels of germinal center B cells and antibody-secreting cell responses. Moreover, the VLP vaccine suppressed the production of IFN-γ and IL-6 cytokines, leading to a significant reduction in brain inflammation and decreased cyst counts following lethal challenge with ME49 infection. These findings suggest that the GRA5 VLP vaccine derived from elicits a protective immune response, highlighting its potential as an effective vaccine candidate against toxoplasmosis.