Immunogenicity of a Recombinant Multi-Epitope Vaccine Incorporating GRA14, SAG1, and GRA1 Antigens of Toxoplasma gondii in BALB/c Mice

Background: The high incidence and severe health threat of Toxoplasma gondii (T. gondii) infection, particularly in immunocompromised patients, underscore the urgent need for the development of a safe and effective vaccine. The aim of this study was to develop a novel multi-epitope vaccine (USM.TOXOII) incorporating the T. gondii GRA14, SAG1, and GRA1 antigens, and to assess its immunogenicity in BALB/c mice. Methods: Using bioinformatics approach, the USM.TOXOII was designed and evaluated. The encoding gene (471 bp) was then constructed and cloned into the pET-30a (+) plasmid before being transformed into E. coli expression system. The recombinant USM.TOXOII protein was subsequently expressed and purified. Finally, an animal study was performed to assess the vaccine’s immunogenicity. Results: The USM.TOXOII protein (17.27 kDa) was soluble and contained a His tag protein. Immunization of BALB/c mice with USM.TOXOII significantly elevated serum levels of total IgG, IgG1, and IgG2a (p < 0.05). Cytokine analysis revealed a significant increase in IFN-γ production, whereas IL-4 levels remained unchanged, suggesting a Th1-biased immune response. Conclusions: Collectively, these findings indicate that USM.TOXOII possesses immunogenic potential and is capable of inducing both humoral and cellular immune responses in BALB/c mice. Future challenge studies with live T. gondii tachyzoites are warranted to evaluate its protective efficacy in vivo.