Protective Efficacy of the Killed Toxoplasma gondii Vaccine in Nano-alum Adjuvant

Background and purpose: Toxoplasma gondii (T. gondii) as a causative agent of toxoplasmosis, is an obligate intracellular parasite which is excreted by the cat's feces. Efforts have been made for the development of toxoplasmosis vaccine, but none led to developing a vaccine with protective immune response to the parasite. Adjuvants are essential for vaccine formulation to create strong immune responses. As an adjuvant, nanomaterials such as nano-alum, can stimulate both humoral and cellular immune responses. The present report aimed to investigate the protective effects of the alum-based nano-adjuvant formulated in killed T. gondii. Materials and methods: In this experimental study, the vaccine candidates were separately formulated in alum, complete Freund, and nano-alum adjuvants. The BALB/c mice were immunized three times with two-week intervals. To investigate the type of induced immune response, sera were analyzed by ELISA for total IgG, IgG1, and IgG2a isotypes and also IL-4, IFN-γ, TNF-α, and IL-2 cytokines. To evaluate lymphocyte proliferation, BrdU method was performed. Results: Immunization of mice with killed Toxoplasma vaccine formulated with nano-alum adjuvant increased lymphocyte proliferation, TNF-α, IL-4, IL-2, and IFN-γ cytokine responses, total antibodies, as well as IgG1 and IgG2a subtypes compared with those of other experimental groups. Conclusion: Compared with alum-based killed Toxoplasma vaccine, the nano-alum adjuvant could strongly induce cellular and humoral immune responses.