Ocular Toxoplasmosis: Mechanisms of Retinal Infection and Experimental Models

Abstract

Ocular toxoplasmosis (OT) is caused by the parasite Toxoplasma gondii and affects many individuals throughout the world. Infection may occur through congenital or acquired routes. The parasites enter the blood circulation and reach both the retina and the retinal pigment epithelium, where they may cause cell damage and cell death. Different routes of access are used by T. gondii to reach the retina through the retinal endothelium: by transmission inside leukocytes, as free parasites through a paracellular route, or after endothelial cell infection. A main feature of OT is the induction of an important inflammatory state, and the course of infection has been shown to be influenced by the host immunogenetics. On the other hand, there is evidence that the T. gondii phenotype also has an impact on the distribution of the pathology in different areas. Although considerable knowledge has been acquired on OT, a deeper knowledge of its mechanisms is necessary to provide new, more targeted treatment strategies. In particular, in addition to in vitro and in vivo experimental models, organotypic, ex vivo retinal explants may be useful in this direction.

Environmental Risk Factors Associated with Retinochoroiditis Caused by <em>Toxoplasma gondii</em>

“…[16,17] 2 Lesions caused by the parasite usually heal in two to four months in immunocompetent patients and a study reveals that in about 70 % of cases of patients who seek an ophthalmologist, the lesions resulting from OT that heal are associated with other lesions. [17,18] The study carried out by our research group revealed that OT represents 27 % of eye diseases affecting patients in the northwest region of the state of São Paulo, Brazil. [19] Infection by the parasite is recognized as the most common zoonotic disease in the world, due to its worldwide distribution and the large number of intermediate hosts.…”