Primary Acquired Toxoplasma Retinochoroiditis: Choroidal Neovascular Membrane as an Early Complication

Use of optical coherence tomography angiography in the uveitis clinic

As optical coherence tomography angiography is revolutionizing the ophthalmology world, the uveitis community is learning to understand where and how this new powerful imaging tool fits into the management of the panorama of ocular inflammations and infections. A non-invasive method of studying the retinal and choroidal vasculature, OCTA allows for the assessment of vessel density changes during active and inactive uveitis making it the natural imaging application of choice in uveitis clinical trials. However, these data and results are of limited utility to the ophthalmologists who are looking to apply OCTA in their everyday uveitis clinic. If employed strategically, OCTA can be a powerful tool for the uveitis specialist to evaluate iris involvement in viral uveitis; to assess the integrity of the vascular layers in the settings of white dot syndromes; to distinguish inflammatory choroidal neovascularization from outer retinal avascular inflammatory material; and to diagnose and follow infectious choroidal granulomas and satellite foci of chorioretinal inflammation without the need to administer dyes. The present review will analyze all the recent publications that apply OCTA in uveitis to offer the reader a guide on how to maximize the utility of this imaging modality in a clinical practice.

Toxoplasma Retinochoroiditis with Chorioretinal Neovascularization in a Young Patient

We present a pediatric case to highlight the clinical appearance and management of choroidal neovascularization in the setting of active toxoplasma retinochoroiditis (TRC). A 17-year-old female presented with 2 days of blurry vision in her left eye. Retinal examination demonstrated a pigmented chorioretinal lesion with associated subretinal fluid, vessel sheathing, and adjacent intraretinal hemorrhage. She was diagnosed with active choroidal neovascularization and successful treatment with bevacizumab revealed an underlying active toxoplasmosis lesion. Choroidal neovascularization may rarely present during an acute case of TRC. Dual therapy with anti-vascular endothelial growth factor antibody and anti-parasitic agents leads to improved visual outcomes.

New findings useful for clinical practice using swept-source optical coherence tomography angiography in the follow-up of active ocular toxoplasmosis

Background

Ocular toxoplasmosis is one of the most common causes of intraocular inflammation and posterior uveitis in immunocompetent patients. This paper aims to investigate swept-source optical coherence tomography angiography (SS-OCTA) findings in eyes with active toxoplasmic retinochoroiditis.

Methods

This case series was conducted from November 2017 through October 2019 in two Brazilian centers. 15 eyes of 15 patients with active toxoplasmic retinochoroiditis were included, and were imaged at baseline and after at least 4 weeks of follow-up. All patients underwent ophthalmic examinations and multimodal imaging including SS-OCT and SS-OCTA before and after treatment of ocular toxoplasmosis. The differential diagnoses included toxoplasmosis, syphilis, and human immunodeficiency virus, which were eliminated through serologic and clinical evaluations.

Results

All 15 patients presented with positive anti-Toxoplasma gondii immunoglobulin G titers and three also presented with positive anti-T. gondii immunoglobulin M titers. The mean age at examination was 32.4 years ± 12.7 years (range 15–59 years). Sixty percent of the patients were female. In all eyes, the inner retinal layers were abnormally hyperreflective with full-thickness disorganization of the retinal reflective layers at the site of the active toxoplasmic retinochoroiditis. At baseline, 80% of eyes had focal choroidal thickening beneath the retinitis area, and all eyes had a choroidal hyporeflective signal. Before treatment, SS-OCTA showed no OCTA decorrelation signal next to the lesion site in all eyes, and flow signal improvement was noticed after treatment. Three eyes presented with intraretinal vascular abnormalities during follow-up. SS-OCTA showed retinal neovascularization in one patient and a presumed subclinical choroidal neovascular membrane in another patient.

Conclusions

SS-OCT and SS-OCTA are useful for assessing unexpected structural and vascular retinal and choroidal changes in active and post-treatment toxoplasmic retinochoroiditis and these findings are useful for clinical practice.

VEGF Production Is Regulated by the AKT/ERK1/2 Signaling Pathway and Controls the Proliferation of Toxoplasma gondii in ARPE-19 Cells

The retina is the primary site of Toxoplasma gondii infection in the eye, and choroidal neovascularization in ocular toxoplasmosis is one of the most important causes of visual impairment. Vascular endothelial growth factor (VEGF) is one of the key regulators of blood vessel development, however, little is known about the mechanisms of T. gondii-induced VEGF production in ocular toxoplasmosis. Here, we investigate the effect of T. gondii on VEGF production regulation in human retinal pigment epithelium ARPE-19 cells and attempted to unveil the underlying mechanism of this event by focusing on the interaction between parasite and the selected host intracellular signaling pathways. T. gondii infection increased the expression of VEGF mRNA and protein in ARPE-19 cells in parasite burden- and infection time-dependent manner. The proportional increase of VEGF upstream regulators, HIF-1α and HO-1, was also observed. T. gondii induced the activation of host p-AKT, p-ERK1/2, and p-p38 MAPK in ARPE-19 cells in a parasite-burden dependent manner. However, VEGF expression decreased after the pre-treatment with PI3K inhibitors (LY294002 and GDC-0941), ERK1/2 inhibitor (PD098059), and p38 MAPK inhibitor (SB203580), but not JNK inhibitor (SP600125), in a dose-dependent manner. The anti-VEGF agent bevacizumab or VEGF siRNA transfection prominently inhibited the activation of p-AKT and p-ERK1/2, but not p-p38 MAPK and JNK1/2 in T. gondii-infected ARPE-19 cells. Bevacizumab treatment or VEGF siRNA transfection significantly inhibited the proliferation of T. gondii tachyzoites in the host cell, dose-dependently, but not invasion of parasites. VEGF-receptor 2 (VEGF-R2) antagonist, SU5416, attenuated VEGF production and tachyzoite proliferation in T. gondii-infected ARPE-19 cells in a dose-dependent manner. Collectively, T. gondii prominently induces VEGF production in ARPE-19 cells, and VEGF and AKT/ERK1/2 signaling pathways mutually regulate each other in T. gondii-infected ARPE-19 cells, but not p38 MAPK and JNK1/2 signaling pathways. VEGF and VEGF-R2 control the parasite proliferation in T. gondii-infected ARPE-19 cells. From this study, we revealed the putative mechanisms for VEGF induction as well as the existence of positive feedback between VEGF and PI3K/MAPK signaling pathways in T. gondii-infected retinal pigment epithelium.