Among the vaccine candidates, the SAG1 protein is the best characterized. This 30-kDa protein is the main surface antigen of T. gondii tachyzoites, is highly conserved in T. gondii strains, induces high antibody levels in humans, and is recognized by all the serum samples from infected subjects. Several vaccination studies using the SAG1 protein combined with type 1 adjuvants or, more recently, DNA vaccines including the SAG1 gene have demonstrated their effectiveness in acute toxoplasmosis models.