Recombinant ROP2, ROP4, GRA4 and SAG1 antigen-cocktails as possible tools for immunoprophylaxis of toxoplasmosis: what's next?

Toxoplasmosis is a globally distributed foodborne zoonosis caused by a protozoan parasite Toxoplasma gondii. Usually asymptomatic in immunocompetent humans, toxoplasmosis is a serious clinical and veterinary problem often leading to lethal damage in an infected host. In order to overcome the exceptionally strong clinical and socio-economic impact of Toxoplasma infection, the construction of an effective vaccine inducing full immunoprotection against the parasite is an urgent issue. In the last two decades many live attenuated, subunit and DNA-based vaccines against toxoplasmosis have been studied, however only partial protection conferred by vaccination against chronic as well as acute infection has been achieved. Among various immunization strategies, no viable subunit vaccines based on recombinant secretory (ROP2, ROP4 and GRA4) and surface (SAG1) T. gondii proteins have been found as attractive tools for further studies. This is due to their high, but still partial, protective efficacy correlated with the induction of cellular and humoral immune responses.