Efficacity and safety of TOXO KO vaccine to prevent ocular toxoplasmosis in congenital murine model

Purpose Toxoplasmosis is a worldwide zoonotic disease caused by the protozoa Toxoplasma gondii and is a major cause of abortions but also of ocular lesions. Thus, ocular toxoplasmosis is a major health issue in certain parts of the world, especially in South America and Africa. Methods We have studied the efficacy of a live attenuated strain of T. gondii (i.e. Toxo mic1-3 KO mutant) as a vaccine against ocular toxoplasmosis in a congenital toxoplasmosis model in mice. Mice were vaccinated with Toxo mic1-3 KO strain, mated and infected during pregnancy. Nonvaccinated mice infected at mid gestation with T. gondii were used as control. One month after delivery, pups were sacrificed and ocular fundus, cytokine production in intra-camerular tissue and cysts formation in eye and in brain were analysed. Results We have demonstrated that: Retinal T. gondii cysts were detected in 71% of pups born to nonvaccinated dams (2.54 ± 4.10). A significantly smaller number of cysts in retinal tissue was seen in pups born to vaccinated dams 0.56 ± 1.18 (>86% reduction in cysts in ocular tissue). Clinical signs of ocular infection were detected in 73.2% of pups born to non vaccinated dams against 19% of pups born to vaccinated dams. Conclusions In conclusion, Toxo mic1-3 KO is an effective vaccine against ocular toxoplasmosis in a congenital mice model. This strain could be a promizing vaccine.