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Open AccessArticle

Molecular Basis of The Retinal Pigment Epithelial Changes That Characterize The Ocular Lesion in Toxoplasmosis

1
College of Medicine & Public Health, Flinders University, Adelaide 5042, Australia
2
Division of Ophthalmology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto 14049-900, Brazil
*
Author to whom correspondence should be addressed.
Microorganisms 2019, 7(10), 405; https://doi.org/10.3390/microorganisms7100405
Received: 21 August 2019 / Revised: 11 September 2019 / Accepted: 19 September 2019 / Published: 29 September 2019
(This article belongs to the Special Issue Insights Into The Molecular Pathogenesis of Ocular Infections)
When a person becomes infected with Toxoplasma gondii, ocular toxoplasmosis is the most common clinical presentation. The medical literature describes retinitis with surrounding hyperpigmentation secondary to proliferative changes in the retinal pigment epithelium, which is sufficiently characteristic that investigation often is not needed to make the diagnosis. We aimed to establish the frequency of “typical” ocular toxoplasmosis and delineate its molecular basis. Among 263 patients presenting consecutively with ocular toxoplasmosis to Ribeirão Preto General Hospital in Brazil, where T. gondii infection is endemic, 94.2% of 345 eyes had retinal hyperpigmentation. In ARPE-19 and primary human retinal pigment epithelial cell monolayers exposed to minimal numbers of T. gondii tachyzoites, the proliferation marker–KI-67–was increased in uninfected cells, which also were rendered more susceptible to infection. RT-qPCR and ELISA detected increased expression of vascular endothelial growth factor A (VEGF) and insulin-like growth factor (IGF)1, and decreased expression of thrombospondin (TSP)1 by infected cells. Blockade of VEGF and IGF1—or supplementation of TSP1—reversed the proliferation phenotype in uninfected cells. Our findings confirm that hyperpigmentation is a characteristic feature of retinitis in ocular toxoplasmosis, and demonstrate that T. gondii-infected human retinal pigment epithelial cells secrete VEGF and IGF1, and reduce production of TSP1, to promote proliferation of adjacent uninfected cells and create this disease-specific appearance. View Full-Text
Keywords: ocular toxoplasmosis; retinal pigment epithelium; retinochoroiditis; Toxoplasma gondii ocular toxoplasmosis; retinal pigment epithelium; retinochoroiditis; Toxoplasma gondii
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Lie, S.; Vieira, B.R.; Arruda, S.; Simões, M.; Ashander, L.M.; Furtado, J.M.; Smith, J.R. Molecular Basis of The Retinal Pigment Epithelial Changes That Characterize The Ocular Lesion in Toxoplasmosis. Microorganisms 2019, 7, 405.

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