Toxoplasmosis, a
zoonotic disease caused by Toxoplasma gondii, is an important public health problem and veterinary concern. Although there is no
vaccine for human
toxoplasmosis, many attempts have been made to develop one. Promising
vaccine candidates utilize
proteins, or their genes, from microneme organelle of T. gondii that are involved in the initial stages of host cell invasion by the parasite. In the present study, we used different recombinant microneme
proteins (TgMIC1, TgMIC4, or TgMIC6) or combinations of these
proteins (TgMIC1-4 and TgMIC1-4-6) to evaluate the immune response and protection against experimental
toxoplasmosis in C57BL/6 mice. Vaccination with recombinant TgMIC1, TgMIC4, or TgMIC6 alone conferred partial protection, as demonstrated by reduced brain
cyst burden and mortality rates after challenge. Immunization with TgMIC1-4 or TgMIC1-4-6
vaccines provided the most effective protection, since 70% and 80% of mice, respectively, survived to the acute phase of
infection. In addition, these vaccinated mice, in comparison to non-vaccinated ones, showed reduced parasite burden by 59% and 68%, respectively. The protective effect was related to the cellular and humoral immune responses induced by vaccination and included the release of Th1
cytokines IFN-γ and
IL-12,
antigen-stimulated spleen cell proliferation, and production of
antigen-specific serum
antibodies. Our results demonstrate that microneme
proteins are potential
vaccines against T. gondii, since their inoculation prevents or decreases the deleterious effects of the
infection.