Acquired and congenital ocular Toxoplasmosis experimentally induced in Calomys callosus (Rodentia, Cricetidae)

An experimental model for acquired and congenital ocular toxoplasmosis as w ell as a model to induce experimental autoimmune uveitis (EAU) was investig ated in Calomys callosus. Toxoplasma gondii, ME-49 strain, was used to infe ct males and pregnant- and not pregnant-females while S-antigen, a major gl ycoprotein of the retinal photoreceptor cell, was used to induce EAU. The o cular lesions elicited by T. gondii were characterized by the presence of c ysts, free tachyzoites and inflammatory cells in the retina ol related tiss ues. In the congenital form, 40% of the fetus presented ocular lesions, i.e ., presence of cysts in the retina, vitreous, and extra-retinal tissues. In the acquired form, 75% of the females and 50% of the males presented unila teral ocular cysts both at 21 and 47 days post-infection. it was also demon strated that S-antigen was not uveitogenic in the C. callosus model. No les ion was observed in the animals exclusively immunized with this retinal com ponent, even when jacalin was used as additional adjuvant for polyclonal re sponse to the retinal antigen. It can be concluded that C. callosus may con stitute in a promising model for study both acquired and congenital ocular toxoplasmosis, particularly when it is important to make sure that a non au toimmune process is involved in the genesis of the ocular infection.