An experimental model for acquired and congenital ocular toxoplasmosis as well
as a model to induce experimental autoimmune uveitis (EAU) was investigated in
Calomys callosus. Toxoplasma gondii, ME-49 strain, was used to infect males and
pregnant- and not pregnant-females while S-antigen, a major glycoprotein of the retinal
photoreceptor cell, was used to induce EAU. The ocular lesions elicited by T. gondii
were characterized by the presence of cysts, free tachyzoites and inflammatory cells in the
retina or related tissues. 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 unilateral ocular cysts both at 21 and 47 days
post-infection. It was also demonstrated that S-antigen was not uveitogenic in the C.
callosus model. No lesion was observed in the animals exclusively immunized with this
retinal component, even when jacalin was used as additional adjuvant for polyclonal response
to the retinal antigen. It can be concluded that C. callosus may constitute in a
promising model for study both acquired and congenital ocular toxoplasmosis, particularly
when it is important to make sure that a non autoimmune process is involved in the genesis of
the ocular infection.
