Toxoplasmosis in the outer retina.

Objective: To present a case of ocular toxoplasmosis. Materials and methods: A sixteen-year-old female patient presented to our clinic with complaints regarding decreased vision in her right eye (BCVA 0.5), starting five days before the exam. Her anamnestic data revealed a previous history of ocular toxoplasmosis in her left eye. OCT scans of the inner retina identified a huge cystic space, located posterior to the inner line, off the outer plexiform layer, with a small amount of hyperreflective foci. Other features of OCT included membranous-like structures on inner borders and elongation and splitting of the inner segment/outer segment junction. In later stages, beginning signs of retinitis and scaring could be observed. Results: The patient was treated with sulfamethoxazole/trimethoprim and prednisolone. After two weeks, total regression occurred and visual acuity and OCT remained stable for 6 months (BCVA 1.0). Discussion: Ocular toxoplasmosis can cause significant vision loss due to retinitis and scarring. Following treatment with sulfamethoxazole/trimethoprim and prednisolone, the patient's condition improved significantly and her visual acuity remained stable. Conclusion: On clinical examination and using OCT, rare morphological cystoid spaces (CS) can be identified as huge outer retina cysts (HORC), which are pathognomonic for posterior uveitis. Abbreviations: HORC = huge outer retinal cyst, OCT = optical coherence tomography, BCVA = best corrected visual acuity, CS = cyst space, OPL = outer plexiform layer, HRF = hyper reflective foci, RPE = retinal pigment epithelium, IS = inner segment, OS = outer segment, ERM = epiretinal membrane, PORT = punctate outer retinal toxoplasmosis, ELM = external limiting membrane.

Murine Model of Primary Acquired Ocular Toxoplasmosis: Fluorescein Angiography and Multiplex Immune Mediator Profiles in the Aqueous Humor.

Purpose: To establish a murine model of primary acquired ocular toxoplasmosis (OT) and to investigate the immune mediator profiles in the aqueous humor (AH). Methods: C57BL/6 mice were perorally infected with Toxoplasma gondii. The ocular fundus was observed, and fluorescein angiography (FA) was performed. The AH, cerebrospinal fluid (CSF), and serum were collected before infection and at 28 days post-infection (dpi); the immune mediator levels in these samples were analyzed using multiplex bead assay. Results: Fundus imaging revealed soft retinochoroidal lesions at 14 dpi; many of these lesions became harder by 28 dpi. FA abnormalities, such as leakage from retinal vessels and dilation and tortuosity of the retinal veins, were observed at 14 dpi. Nearly all these abnormalities resolved spontaneously at 28 dpi. In the AH, interferon-γ, interleukin (IL)-1α, IL-1ß, IL-6, IL-10, IL-12(p40), IL-12(p70), CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1ß, CCL5/RANTES, and CXCL1/KC levels increased after infection. All these molecules except IL-1α, IL-4, and IL-13 showed almost the same postinfection patterns in the CSF as they did in the AH. The tumor necrosis factor α, IL-4, and IL-5 levels in the AH and CSF of the T. gondii-infected mice were lower than those in the serum. The postinfection IL-1α, IL-6, CCL2/MCP-1, CCL4/MIP-1ß, and granulocyte colony-stimulating factor levels in the AH were significantly higher than those in the CSF and serum. Conclusions: A murine model of primary acquired OT induced via the natural infection route was established. This OT model allows detailed ophthalmologic, histopathologic, and immunologic evaluations of human OT. Investigation of AH immune modulators provides new insight into OT immunopathogenesis.

Case Report: Acute Vision Loss in a Young Returning Traveler with Dengue Fever.

Ocular complications are rare in patients with dengue fever, but may cause permanent loss of vision. We present the case of a 29-year-old German woman who developed severe acute vision loss because of dengue-associated maculopathy after traveling to Vietnam and Cambodia. Initially, the optical coherence tomography showed detachment of the retinal pigment epithelium, a central shift in the retinal pigmentation and intraretinal cysts. The patient was hospitalized and treated with a short course of intravenous prednisolone. Vision improved, and the patient showed full recovery at 9 months after the onset. This case highlights the importance of awareness and adequate management for ocular involvement in patients with dengue fever, including travelers.

CD40 in Endothelial Cells Restricts Neural Tissue Invasion by Toxoplasma gondii.

Little is known about whether pathogen invasion of neural tissue is affected by immune-based mechanisms in endothelial cells. We examined the effects of endothelial cell CD40 on Toxoplasma gondii invasion of the retina and brain, organs seeded hematogenously. T. gondii circulates in the bloodstream within infected leukocytes (including monocytes and dendritic cells) and as extracellular tachyzoites. After T. gondii infection, mice that expressed CD40 restricted to endothelial cells exhibited diminished parasite loads and histopathology in the retina and brain. These mice also had lower parasite loads in the retina and brain after intravenous (i.v.) injection of infected monocytes or dendritic cells. The protective effect of endothelial cell CD40 was not explained by changes in cellular or humoral immunity, reduced transmigration of leukocytes into neural tissue, or reduced invasion by extracellular parasites. Circulating T. gondii-infected leukocytes (dendritic cells used as a model) led to infection of neural endothelial cells. The number of foci of infection in these cells were reduced if endothelial cells expressed CD40. Infected dendritic cells and macrophages expressed membrane-associated inducible Hsp70. Infected leukocytes triggered Hsp70-dependent autophagy in CD40+ endothelial cells and anti-T. gondii activity dependent on ULK1 and beclin 1. Reduced parasite load in the retina and brain not only required CD40 expression in endothelial cells but was also dependent on beclin 1 and the expression of inducible Hsp70 in dendritic cells. These studies suggest that during endothelial cell-leukocyte interaction, CD40 restricts T. gondii invasion of neural tissue through a mechanism that appears mediated by endothelial cell anti-parasitic activity stimulated by Hsp70.

Isolation of viable Toxoplasma gondii from organs and Brazilian commercial meat cuts of experimentally infected pigs.

The present study evaluated the distribution and viability of Toxoplasma gondii tissue cysts in the organs and Brazilian commercial cuts of experimentally infected pigs. The pigs were infected with 3 × 103 oocysts of the T. gondii isolate TgCkBr57 (Type BrII). Mouse bioassays were performed on the brain, retina, tongue, diaphragm, and heart as well as the following muscle cuts: loin (longissimus), coppa (longissimus, spinalis dorsi, rhomboideus), tenderloin (psoas major), outside flat (biceps femoris), topside (semimembranosus), and top sirloin (gluteus medius). Toxoplasma gondii was isolated from the coppa, heart, diaphragm, and tongue of three pigs; from the tenderloin, outside flat, and brain of two pigs; and from the top sirloin and loin of one pig. Thus, the viability of T. gondii cysts was observed in all of the organs and cuts evaluated (except for the topside and retina), demonstrating the broad distribution of this parasite in pig organs and commercial meat cuts, and the importance of this species as a source of human infection.

Epidermal growth factor receptor promotes cerebral and retinal invasion by Toxoplasma gondii.

Little is known about strategies used by pathogens to facilitate CNS invasion. Toxoplasma gondii reaches the CNS by circulating in blood within leukocytes or as extracellular tachyzoites. T. gondii induces EGFR signaling in vitro during invasion of mammalian cells. We examined the effects of endothelial cell EGFR on CNS invasion. Transgenic mice whose endothelial cells expressed a dominant negative (DN) EGFR (inhibits EGFR signaling) exhibited diminished parasite load and histopathology in the brain and retina after T. gondii infection. I.V. administration of infected leukocytes or extracellular tachyzoites led to reduced parasite loads in mice with DN EGFR. This was not explained by enhanced immunity or reduced leukocyte recruitment. Endothelial cell infection is key for CNS invasion. Parasite foci in brain endothelial cells were reduced by DN EGFR. DN EGFR in these cells led to recruitment of the autophagy protein LC3 around T. gondii and spontaneous parasite killing dependent on the autophagy protein ULK1 and lysosomal enzymes. The autophagy inhibitor 3-MA prevented DN EGFR mice from exhibiting reduced CNS invasion. Altogether, EGFR is a novel regulator of T. gondii invasion of neural tissue, enhancing invasion likely by promoting survival of the parasite within endothelial cells.

Subretinal Cysticercosis Extraction With Bimanual, 3-D, Heads-Up-Assisted Pars Plana Vitrectomy: Clinicopathological Correlation and Surgical Technique.

A 16-year-old male presented with blurred vision in the right eye after recent travel to Nicaragua. Funduscopic examination revealed subretinal cysticercosis superior to the optic nerve. The cyst was drained and excised using a bimanual, three-dimensional, heads-up-assisted pars plana vitrectomy without complications. Technical maneuvers for cyst extraction along with clinicopathological correlation are described. Postoperatively, the patient exhibits no signs of recurrence and has excellent vision. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:708-711.].

Investigation of tissue cysts in the retina in a mouse model of ocular toxoplasmosis: distribution and interaction with glial cells.

The conversion of tachyzoites into bradyzoites is a way for Toxoplasma gondii to establish a chronic and asymptomatic infection and achieve lifelong persistence in the host. The bradyzoites form tissue cysts in the retina, but not much is known about the horizontal distribution of the cysts or their interactions with glial cells in the retina. A chronic ocular toxoplasmosis model was induced by per oral administration of T. gondii Me49 strain cysts to BALB/c mice. Two months after the infection, retinas were flat-mounted and immunostained to detect cysts, ganglion cells, Müller cells, astrocytes, and microglial cells, followed by observation under fluorescence and confocal microscope. The horizontal distribution showed a rather clustered pattern, but the clusters were not restricted to certain location of the retina. Axial distribution was confined to the inner retina, mostly in ganglion cell layer or the inner plexiform layer. Both ganglion cells, a type of retinal neurons, and Müller cells, predominant retinal glial cells, could harbor cysts. The cysts were spatially separated from astrocytes, the most abundant glial cells in the ganglion cell layer, while close spatial distribution of microglial cells was observed in two thirds of retinal cysts. In this study, we demonstrated that the retinal cysts were not evenly distributed horizontally and were confined to the inner retina axially. Both neurons and one type of glial cells could harbor cysts, and topographic analysis of other glial cells suggests role of microglial cells in chronic ocular toxoplasmosis.

Cerebral malaria induces electrophysiological and neurochemical impairment in mice retinal tissue: possible effect on glutathione and glutamatergic system.

BACKGROUND: Cerebral malaria (CM) is a severe complication resulting from Plasmodium falciparum infection. This condition has usually been associated with cognitive, behavioural and motor dysfunctions, being the retinopathy the most serious consequence resulting from the disease. The pathophysiological mechanisms underlying this complication remain incompletely understood. Several experimental models of CM have already been developed in order to clarify those mechanisms related to this syndrome. In this context, the present work has been performed to investigate which possible electrophysiological and neurochemistry alterations could be involved in the CM pathology. METHODS: Experimental CM was induced in Plasmodium berghei-infected male and female C57Bl/6 mice. The survival and neurological symptoms of CM were registered. Brains and retina were assayed for TNF levels and NOS2 expression. Electroretinography measurements were recorded to assessed a- and b-wave amplitudes and neurochemicals changes were evaluated by determination of glutamate and glutathione levels by HPLC. RESULTS: Susceptible C57Bl/6 mice infected with ≈ 106 parasitized red blood cells (P. berghei ANKA strain), showed a low parasitaemia, with evident clinical signs as: respiratory failure, ataxia, hemiplegia, and coma followed by animal death. In parallel to the clinical characterization of CM, the retinal electrophysiological analysis showed an intense decrease of a- and-b-wave amplitude associated to cone photoreceptor response only at the 7 days post-infection. Neurochemical results demonstrated that the disease led to a decrease in the glutathione levels with 2 days post inoculation. It was also demonstrated that the increase in the glutathione levels during the infection was followed by the increase in the 3H-glutamate uptake rate (4 and 7 days post-infection), suggesting that CM condition causes an up-regulation of the transporters systems. Furthermore, these findings also highlighted that the electrophysiological and neurochemical alterations occurs in a manner independent on the establishment of an inflammatory response, once tumour necrosis factor levels and inducible nitric oxide synthase expression were altered only in the cerebral tissue but not in the retina. CONCLUSIONS: In summary, these findings indicate for the first time that CM induces neurochemical and electrophysiological impairment in the mice retinal tissue, in a TNF-independent manner.

Pars Plana Vitrectomy With in Vivo Cyst Lysis for Intraocular Cysticercosis.

BACKGROUND AND OBJECTIVE: To evaluate efficacy and safety of pars plana vitrectomy (PPV) and in vivo cyst lysis for intraocular cysticercosis. PATIENTS AND METHODS: Retrospective analysis of the records of 15 patients undergoing PPV for intraocular cysticercosis at a tertiary eye care center was done. All patients had undergone in vivo cyst lysis. Of these 15 patients, one had intravitreal cysticercosis (IVC) with vitritis, two cases had IVC with vitritis with tractional retinal detachment (TRD), four cases had subretinal cysticercosis (SRC), four cases had SRC with extensive fibrosis without TRD, and five cases had SRC with fibrosis with TRD. Postoperative visual acuity at 3 months of follow-up was analyzed as the primary outcome measure. RESULTS: Mean age of patients was 26 years ± 12.27 years. Four out of 15 patients were female. Mean preoperative best-corrected visual acuity (BCVA) was 1.55 logMAR units ± 0.62 logMAR units, whereas mean postoperative BCVA at last follow-up (3 months) was 1.26 logMAR units ± 0.65 log-MAR units. Mean visual gain (0.29 logMAR units) post-surgery was statistically significant (P = .018). The final visual acuity correlated with preoperative BCVA with Pearson's coefficient being 0.78 (95% CI, 0.44-0.92; P = .001). Anatomical success was achieved in 13 of 15 (87%) cases. In one case the cyst was dead and calcified and could not be removed. TRD was associated with poor visual gain. CONCLUSION: Intravitreal cyst lysis is a safe and successful approach for managing intraocular cysticercosis. Visual results depend on preoperative condition. TRD implicates poor visual prognoses. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:665-669.].

Diffuse Unilateral Subacute Neuroretinitis From Raccoon Exposure Resistant to Laser Photocoagulation.

Diffuse unilateral subacute neuroretinitis (DUSN) is an ocular disease caused by a subretinal nematode worm. The authors present a unique case of a 9-year-old girl with DUSN due to presumed Baylisascaris procyonis, given the size of the worm and previous raccoon exposure. The worm was located in the inner retina and treated with laser photocoagulation and albendazole. At the 1-week follow-up, the worm was still mobile despite being inactive immediately after the initial laser treatment and required a more prolonged laser session. This case serves to highlight the importance of close follow-up in patients with DUSN to ensure the worm is inactivated. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:686-690.].

Morphometric changes in C57BL/6 mice retina infected by Toxoplasma gondii ME 49 strain.

This study evaluated the morphometric implications in C57BL/6 mouse retina infected by Toxoplasma gondii, ME 49 strain. Twenty C57BL/6 female mice were divided into group 1 (n=8, intraperitoneally infected with 30 cysts of T. gondii ME 49 strain) and group 2 (n=12 non-infected controls). The eyes were enucleated on the 60th day after infection, fixed and processed for light microscopy. Changes in retinal thickness and in the perimeter/area ratio (P/A) of the retinal layers were analyzed by digital morphometry. We considered that P/A was the measurement of retinal architecture distortion induced by toxoplasmosis. This study considered the ganglion cells and nerve fiber layers as a monolayer, thus six layers of retina were evaluated: photoreceptors (PRL), outer nuclear (ONL), outer plexiform (OPL), inner nuclear (INL), inner plexiform (IPL) and ganglion cells/nerve fiber monolayer (GNL). Histological analysis of infected mouse retina showed inflammatory infiltrate, necrosis, glial reaction and distortion of the retina architecture. It also presented increased thickness (167.8±24.9µm versus 121.1±15.4µm, in controls) and increased retinal thickness within the retinitis foci (187.7±16.6µm versus 147.9±12.2µm out of the retinitis foci). A statistically significant difference in P/A was observed between infected and uninfected mouse retinas. The same was observed in PRL, OPL, INL and GNL. Retinal morphometry may be used to demonstrate differences between infected and uninfected mouse retinas.

Spectral-domain optical coherence tomography appearance of a retinal nematode.

A 65-year-old man presented with decreased visual acuity in his left eye of 10 days' duration. Ocular examination revealed visual acuity of 20/200 in the left eye caused by a visible retinal nematode (roundworm) located close to the fovea. Spectral-domain optical coherence tomography imaging showed the nematode in the retinal nerve fiber layer. The patient was followed up without treatment, and the nematode disappeared spontaneously after 5 weeks. Visual acuity in the affected eye improved to 20/25.

Toxoplasma gondii: flat-mounting of retina as a new tool for the observation of ocular infection in mice.

Ocular toxoplasmosis is the principal cause of posterior uveitis and a leading cause of blindness. Animal models are required to improve our understanding of the pathogenesis of this disease. The method currently used for the detection of retinal cysts in animals involves the observation, under a microscope, of all the sections from infected eyes. However, this method is time-consuming and lacks sensitivity. We have developed a rapid, sensitive method for observing retinal cysts in mice infected with Toxoplasma gondii. This method involves combining the flat-mounting of retina - a compromise between macroscopic observation and global analysis of this tissue - and the use of an avirulent recombinant strain of T. gondii expressing the Escherichia coli beta-galactosidase gene, visually detectable at the submacroscopic level. Single cyst unilateral infection was found in six out of 17 mice killed within 28 days of infection, whereas a bilateral infection was found in only one mouse. There was no correlation between brain cysts number and ocular infection.

Retinal pathology of pediatric cerebral malaria in Malawi.

INTRODUCTION: The causes of coma and death in cerebral malaria remain unknown. Malarial retinopathy has been identified as an important clinical sign in the diagnosis and prognosis of cerebral malaria. As part of a larger autopsy study to determine causes of death in children with coma presenting to hospital in Blantyre, Malawi, who were fully evaluated clinically prior to death, we examined the histopathology of eyes of patients who died and underwent autopsy. METHODOLOGY/PRINCIPAL FINDINGS: Children with coma were admitted to the pediatric research ward, classified according to clinical definitions as having cerebral malaria or another cause of coma, evaluated and treated. The eyes were examined by direct and indirect ophthalmoscopy. If a child died and permission was given, a standardized autopsy was carried out. The patient was then assigned an actual cause of death according to the autopsy findings. The eyes were examined pathologically for hemorrhages, cystoid macular edema, parasite sequestration and thrombi. They were stained immunohistochemically for fibrin and CD61 to identify the components of thrombi, beta-amyloid precursor protein to detect axonal damage, for fibrinogen to identify vascular leakage and for glial fibrillary acidic protein to detect gliosis. Sixty-four eyes from 64 patients were examined: 35 with cerebral malaria and 29 with comas of other causes. Cerebral malaria was distinguished by sequestration of parasitized erythrocytes, the presence and severity of retinal hemorrhages, the presence of cystoid macular edema, the occurrence and number of fibrin-platelet thrombi, the presence and amount of axonal damage and vascular leakage. CONCLUSIONS/SIGNIFICANCE: We found significant differences in retinal histopathology between patients who died of cerebral malaria and those with other diagnoses. These histopathological findings offer insights into the etiology of malarial retinopathy and provide a pathological basis for recently described retinal capillary non-perfusion in children with malarial retinopathy. Because of the similarities between the retina and the brain it also suggests mechanisms that may contribute to coma and death in cerebral malaria.

Ocular toxoplasmosis: the role of retinal pigment epithelium migration in infection.

Our aim was to study the migration of retinal pigmented epithelium (RPE) into the retinal layer during infection of C57BL/6 mice with Toxoplasma gondii. Eyes from infected and non-infected animals were analyzed on the 60th day of infection by light and transmission electron microscopy. Non-infected eyes showed a normal morphology. In contrast, we observed free parasites in the retinal vasculature, the presence of mononuclear inflammatory infiltrate (MNII) and parasites in the vasculature of choroids in infected eyes. No inflammatory infiltrate was observed; RPE cells were identified near the MNII in nuclear and plexiforme layers. RPE cells were also found on the ganglion cell layer and in the outer segments of the photoreceptor. The morphology showed that RPE cells caused a discontinuity in the nuclear and plexiforme layers. Clusters of parasites were found surrounded by RPE cells and MNII in the inner plexiforme layers. Ultrastructural analysis showed that RPE cells migrated through the epithelium into the inner retinal layers. We did not observe Toxoplasma cysts in many eyes in which pathological changes were detected. Only 8.3% of the animals had Toxoplasma cysts in the inner nuclear layer in the absence of inflammatory cells. The migration of RPE cells can be triggered by a disruption of the RPE monolayer or injury to the neural retina, as in the case of toxoplasmosis.