Ocular Toxoplasmosis: Recent Aspects of Pathophysiology and Clinical Implications

Abstract

Toxoplasma gondii is an extremely successful opportunistic parasite which infects approximately one third of the human population worldwide. The impact of this parasite on human health becomes particularly manifest in congenital damage with infection and subsequent inflammation of neuronal tissues including the retina. Although advances in our understanding could be achieved in ocular toxoplasmosis, large gaps still exist on factors influencing the epidemiology and pathophysiology of this potentially blinding disease. We are only at the beginning of understanding the complex biology of this parasite and its mechanisms of invasion, virulence and interaction with the host's immune response. Since it is a preventable cause of blindness, it is necessary to assess factors that have the potential to control this disease in the future. This mini review will focus on recent advances in postnatal acquired ocular infection and the factors that may influence its prevalence and functional outcome.

Ocular toxoplasmosis: susceptibility in respect to the genes encoding the KIR receptors and their HLA class I ligands

“…Possible causes of ocular manifestations of toxoplasmosis have not been fully elucidated, but it is believed that factors related both to the parasite and the host contribute to the development of this disease428. Therefore, the study of the impact of genes on infections, such as toxoplasmosis, is extremely important because it provides information about the contribution of the host’s genetic factors on the development of this type of disease.…”

“…Furthermore, the high imunopathogenicity responsible for tissue damage and deterioration of ocular toxoplasmosis may be due to the presence of a potent inducer of inflammation, IL-1756, which is also produced by NK cells7. On the other hand, ocular toxoplasmosis may be linked to autoimmunity14.…”

“…The damage to ocular tissues led to the proposal of phenomena that may be related to pathogenic mechanisms of ocular toxoplasmosis, including autoimmune mechanisms14. Now it is known that an exaggerated T-helper 1 (Th-1) response, in particular by Th-17 cells, can cause tissue damage and contribute to the severity of ocular toxoplasmosis due to the production of interleukin-17 (IL-17), a potent inducer of inflammation56.…”

ToxoplasmaGRA15 limits parasite growth in IFNγ-activated fibroblasts through TRAF ubiquitin ligases

“…Toxoplasma is a highly successful obligate intracellular parasite that can establish lifelong chronic infections in a wide range of warm-blooded animals. In humans it causes opportunistic infections in immunosuppressed patients, congenital infections (Hill & Dubey, 2002), and blindness (Pleyer et al, 2014). Many different Toxoplasma strains exist but in Europe and North-America human infections are dominated by the type I and type II clonal lineages (Howe & Sibley, 1995;Saeij et al, 2005).…”

Ocular Toxoplasmosis

“…Last, while the overall recurrence rates in the cited studies appear to be similar, it may be that populations exposed to different strains of T. gondii experience different rates of reactivation. 20,21 Yusuf et al…”