Effects of tumor necrosis factor-α and interleukin-1ß on human retinal endothelial cells.

Uveitis, or intraocular inflammation, is a potentially blinding condition that mostly affects the working-age population. The cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-1ß, play a role in the pathogenesis of non-infectious uveitis and have been linked to the breakdown of the inner blood-retinal barrier, composed mainly of retinal endothelial cells, leading to macular oedema and vascular leakage. However, the effects of TNF-α and IL-1ß on human retinal endothelial function are not fully understood. In this work, we investigated the impact of TNF-α and IL-1ß on several aspects of human retinal endothelial cell biology. Through a real-time biosensor, the impact of TNF-α and IL-1ß on formation of a retinal endothelial cell barrier was analyzed. Changes in junctional components were assessed via RT-qPCR and immunolabelling. Cell survival, necrosis and apoptosis were appraised via cell proliferation and flow cytometric studies. Tumor necrosis factor-α and IL-1ß impaired the electrical resistance of the retinal endothelial cell barrier, while the addition of a potentially barrier-impairing cytokine, IL-6, did not enhance the effect of TNF-α and IL-1ß. Level of the gene transcript encoding zonula occludens (ZO)-1 was diminished, while ZO-1 protein configuration was changed by TNF-α and IL-1ß. Both cytokines affected human retinal endothelial cell proliferation and viability, while only TNF-α increased rates of necrosis. These results indicate that TNF-α and IL-1ß are important drivers of retinal endothelial dysfunction in non-infectious uveitis, suggesting that targeting these cytokines is critical when treating complications of uveitis, such as macular oedema and vascular leakage.

Selective Transcription Factor Blockade Reduces Human Retinal Endothelial Cell Expression of Intercellular Adhesion Molecule-1 and Leukocyte Binding.

The interaction between leukocytes and cytokine-activated retinal endothelium is an initiating step in non-infectious uveitis involving the posterior eye, mediated by cell adhesion molecules. However, because cell adhesion molecules are required for immune surveillance, therapeutic interventions would ideally be employed indirectly. Using 28 primary human retinal endothelial cell isolates, this study sought to identify transcription factor targets for reducing levels of the key retinal endothelial cell adhesion molecule, intercellular adhesion molecule (ICAM)-1, and limiting leukocyte binding to the retinal endothelium. Five candidate transcription factors-C2CD4B, EGR3, FOSB, IRF1, and JUNB-were identified by differential expression analysis of a transcriptome generated from IL-1ß- or TNF-α-stimulated human retinal endothelial cells, interpreted in the context of the published literature. Further filtering involved molecular studies: of the five candidates, C2CD4B and IRF1 consistently demonstrated extended induction in IL-1ß- or TNF-α-activated retinal endothelial cells and demonstrated a significant decrease in both ICAM-1 transcript and ICAM-1 membrane-bound protein expression by cytokine-activated retinal endothelial cells following treatment with small interfering RNA. RNA interference of C2CD4B or IRF1 significantly reduced leukocyte binding in a majority of human retinal endothelial cell isolates stimulated by IL-1ß or TNF-α. Our observations suggest that the transcription factors C2CD4B and IRF1 may be potential drug targets for limiting leukocyte-retinal endothelial cell interactions in non-infectious uveitis involving the posterior eye.

Erratum to "Molecular Responses of Human Retinal Cells to Infection with Dengue Virus".

[This corrects the article DOI: 10.1155/2017/3164375.].

Effect of NADPH oxidase 1 and 4 blockade in activated human retinal endothelial cells.

BACKGROUND: Over-production of reactive oxygen species (ROS) and resulting oxidative stress contribute to retinal damage in vascular diseases that include diabetic retinopathy, retinopathy of prematurity and major retinal vessel occlusions. NADPH oxidase (Nox) proteins are professional ROS-generating enzymes, and therapeutic targeting in these diseases has strong appeal. Pharmacological inhibition of Nox4 reduces the severity of experimental retinal vasculopathy. We investigated the potential application of this drug approach in humans. METHODS: Differential Nox enzyme expression was studied by real-time-quantitative polymerase chain reaction in primary human retinal endothelial cell isolates and a characterized human retinal endothelial cell line. Oxidative stress was triggered chemically in endothelial cells, by treatment with dimethyloxalylglycine (DMOG; 100 µM); Nox4 and vascular endothelial growth factor (VEGFA) transcript were measured; and production of ROS was detected by 2',7'-dichlorofluorescein. DMOG-stimulated endothelial cells were treated with two Nox1/Nox4 inhibitors, GKT136901 and GKT137831; cell growth was monitored by DNA quantification, in addition to VEGFA transcript and ROS production. RESULTS: Nox4 (isoform Nox4A) was the predominant Nox enzyme expressed by human retinal endothelial cells. Treatment with DMOG significantly increased endothelial cell expression of Nox4 over 72 h, accompanied by ROS production and increased VEGFA expression. Treatment with GKT136901 or GKT137831 significantly reduced DMOG-induced ROS production and VEGFA expression by endothelial cells, and the inhibitory effect of DMOG on cell growth. CONCLUSIONS: Our findings in experiments on activated human retinal endothelial cells provide translational corroboration of studies in experimental models of retinal vasculopathy and support the therapeutic application of Nox4 inhibition by GKT136901 and GKT137831 in patients with retinal vascular diseases.

Molecular Responses of Human Retinal Cells to Infection with Dengue Virus.

Recent clinical reports indicate that infection with dengue virus (DENV) commonly has ocular manifestations. The most serious threat to vision is dengue retinopathy, including retinal vasculopathy and macular edema. Mechanisms of retinopathy are unstudied, but observations in patients implicate retinal pigment epithelial cells and retinal endothelial cells. Human retinal cells were inoculated with DENV-2 and monitored for up to 72 hours. Epithelial and endothelial cells supported DENV replication and release, but epithelial cells alone demonstrated clear cytopathic effect, and infection was more productive in those cells. Infection induced type I interferon responses from both cells, but this was stronger in epithelial cells. Endothelial cells increased expression of adhesion molecules, with sustained overexpression of vascular adhesion molecule-1. Transcellular impedance decreased for epithelial monolayers, but not endothelial monolayers, coinciding with cytopathic effect. This reduction was accompanied by disorganization of intracellular filamentous-actin and decreased expression of junctional molecules, zonula occludens 1, and catenin-ß1. Changes in endothelial expression of adhesion molecules are consistent with the retinal vasculopathy seen in patients infected with DENV; decreases in epithelial junctional protein expression, paralleling loss of integrity of the epithelium, provide a molecular basis for DENV-associated macular edema. These molecular processes present potential therapeutic targets for vision-threatening dengue retinopathy.

Targeting Endothelial Adhesion Molecule Transcription for Treatment of Inflammatory Disease: A Proof-of-Concept Study.

Targeting the endothelial adhesion molecules that control leukocyte trafficking into a tissue has been explored as a biological therapy for inflammatory diseases. However, these molecules also participate in leukocyte migration for immune surveillance, and inhibiting the physiological level of an adhesion molecule might promote infection or malignancy. We explored the concept of targeting endothelial adhesion molecule transcription during inflammation in a human system. Intercellular adhesion molecule 1 (ICAM-1) mediates leukocyte migration across the retinal endothelium in noninfectious posterior uveitis. We observed an increase in the transcription factor, nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (NF-κB1), in parallel with ICAM-1, in human retinal endothelial cells treated with tumor necrosis factor-alpha (TNF-α), and identified putative binding sites for NF-κB1 within the ICAM-1 regulatory region. We targeted induced NF-κB1 expression in endothelial cells with small interfering (si)RNA. Knockdown of NF-κB1 significantly decreased cell surface expression of ICAM-1 protein induced by TNF-α but did not reduce constitutive ICAM-1 expression. Consistently, NF-κB1 knockdown significantly reduced leukocyte binding to cell monolayers in the presence of TNF-α but did not impact baseline binding. Findings of this proof-of-concept study indicate that induced transcription of endothelial adhesion molecules might be targeted therapeutically for inflammatory disease in humans.

Brief research report: ETS-1 blockade increases ICAM-1 expression in activated human retinal endothelial cells.

Intercellular adhesion molecule 1 (ICAM-1) is a central cell adhesion molecule for retinal transendothelial migration of the leukocytes in non-infectious posterior uveitis. Inhibiting ICAM1 gene transcription reduces induction of ICAM-1 in inflamed retinal endothelium. Based on published literature implicating transcription factor ETS-1 as an activator of ICAM1 gene transcription, we investigated the effect of ETS-1 blockade on ICAM-1 levels in cytokine-stimulated human retinal endothelial cells. We first examined ICAM1 and ETS1 transcript expression in human retinal endothelial cells exposed to tumor necrosis factor-alpha (TNF-α) or interleukin-1beta (IL-1ß). ICAM1 and ETS1 transcripts were increased in parallel in primary human retinal endothelial cell isolates (n = 5) after a 4-hour stimulation with TNF-α or IL-1ß (p ≤ 0.012 and ≤ 0.032, respectively). We then assessed the effect of ETS-1 blockade by small interfering (si)RNA on cellular ICAM1 transcript and membrane-bound ICAM-1 protein. ETS1 transcript was reduced by greater than 90% in cytokine-stimulated and non-stimulated human retinal endothelial cell monolayers following a 48-hour treatment with two ETS-1-targeted siRNA, in comparison to negative control non-targeted siRNA (p ≤ 0.0002). The ETS-1 blockade did not reduce ICAM1 transcript expression nor levels of membrane-bound ICAM-1 protein, rather it increased both for a majority of siRNA-treatment and cytokine-stimulation conditions (p ≤ 0.018 and ≤ 0.004, respectively). These unexpected findings indicate that ETS-1 blockade increases ICAM-1 transcript and protein levels in human retinal endothelial cells. Thus ETS-1-targeting would be expected to promote rather than inhibit retinal transendothelial migration of leukocytes in non-infectious posterior uveitis.

Oxidative Stress and Its Regulation in Diabetic Retinopathy.

Diabetic retinopathy is the retinal disease associated with hyperglycemia in patients who suffer from type 1 or type 2 diabetes. It includes maculopathy, involving the central retina and characterized by ischemia and/or edema, and peripheral retinopathy that progresses to a proliferative stage with neovascularization. Approximately 10% of the global population is estimated to suffer from diabetes, and around one in 5 of these individuals have diabetic retinopathy. One of the major effects of hyperglycemia is oxidative stress, the pathological state in which elevated production of reactive oxygen species damages tissues, cells, and macromolecules. The retina is relatively prone to oxidative stress due to its high metabolic activity. This review provides a summary of the role of oxidative stress in diabetic retinopathy, including a description of the retinal cell players and the molecular mechanisms. It discusses pathological processes, including the formation and effects of advanced glycation end-products, the impact of metabolic memory, and involvements of non-coding RNA. The opportunities for the therapeutic blockade of oxidative stress in diabetic retinopathy are also considered.

Expression of Long Non-Coding RNAs in Activated Human Retinal Vascular Endothelial Cells.

PURPOSE: Retinal endothelial cell activation is a central event in non-infectious posterior uveitis. There is recent interest in long non-coding (lnc)RNA-targeted therapeutics for retinal diseases. We aimed to identify human retinal endothelial cell lncRNAs that might be involved in activation. METHODS: Eleven candidate lncRNAs were identified: GAS5, KCNQ1OT1, LINC00294, MALAT1, MEG3, MIR155HG, NEAT1, NORAD, OIP5-AS1, SENCR, TUG1. Expression was assessed by RT-PCR in human retinal endothelial cells, at baseline and following activation with interleukin (IL)-1ß and tumor necrosis factor (TNF)-α. RESULTS: IL-1ß significantly upregulated MEG3 and SENCR at 4 and 24 hours; LINC00294, NORAD, OIP5-AS1 and TUG1 at 24 hours; and MIR155HG at 4, 24 and 48 hours; but downregulated GAS5 at 24 and 48 hours. TNF-α significantly upregulated KCNQ1OT1, LINC00294, MEG3, NORAD and SENCR at 4 hours; SENCR and TUG1 at 24 hours; and MIR155HG at all time points. CONCLUSIONS: Future studies involving manipulation of MIR155HG may be warranted to explore potential therapeutic applications for non-infectious posterior uveitis.

Intercellular Adhesion Molecule 1: More than a Leukocyte Adhesion Molecule.

Intercellular adhesion molecule 1 (ICAM-1) is a transmembrane protein in the immunoglobulin superfamily expressed on the surface of multiple cell populations and upregulated by inflammatory stimuli. It mediates cellular adhesive interactions by binding to the ß2 integrins macrophage antigen 1 and leukocyte function-associated antigen 1, as well as other ligands. It has important roles in the immune system, including in leukocyte adhesion to the endothelium and transendothelial migration, and at the immunological synapse formed between lymphocytes and antigen-presenting cells. ICAM-1 has also been implicated in the pathophysiology of diverse diseases from cardiovascular diseases to autoimmune disorders, certain infections, and cancer. In this review, we summarize the current understanding of the structure and regulation of the ICAM1 gene and the ICAM-1 protein. We discuss the roles of ICAM-1 in the normal immune system and a selection of diseases to highlight the breadth and often double-edged nature of its functions. Finally, we discuss current therapeutics and opportunities for advancements.

Dengue Virus Infection of Human Retinal Müller Glial Cells.

Retinopathy is a recently recognized complication of dengue, affecting up to 10% of hospitalized patients. Research on the pathogenesis has focused largely on effects of dengue virus (DENV) at the blood-retinal barrier. Involvement of retinal Müller glial cells has received little attention, although this cell population contributes to the pathology of other intraocular infections. The goal of our work was to establish the susceptibility of Müller cells to infection with DENV and to identify characteristics of the cellular antiviral, inflammatory, and immunomodulatory responses to DENV infection in vitro. Primary human Müller cell isolates and the MIO-M1 human Müller cell line were infected with the laboratory-adapted Mon601 strain and DENV serotype 1 and 2 field isolates, and cell-DENV interactions were investigated by immunolabelling and quantitative real-time polymerase chain reaction. Müller cells were susceptible to DENV infection, but experiments involving primary cell isolates indicated inter-individual variation. Viral infection induced an inflammatory response (including tumour necrosis factor-α, interleukin [IL]-1ß, and IL-6) and an immunomodulatory response (including programmed death-ligand [PD-L]1 and PD-L2). The type I interferon response was muted in the Müller cell line compared to primary cell isolates. The highest infectivity and cell responses were observed in the laboratory-adapted strain, and overall, infectivity and cell responses were stronger in DENV2 strains. This work demonstrates that Müller cells mount an antiviral and immune response to DENV infection, and that this response varies across cell isolates and DENV strain. The research provides a direction for future efforts to understand the role of human retinal Müller glial cells in dengue retinopathy.

Human retinal endothelial cells express functional interleukin-6 receptor.

BACKGROUND: Interleukin (IL)-6 is an inflammatory cytokine present in the eye during non-infectious uveitis, where it contributes to the progression of inflammation. There are two major IL-6 signaling pathways: classic signaling and trans-signaling. Classic signaling requires cellular expression of the IL-6 receptor (IL-6R), which exists in membrane-bound (mIL-6R) and soluble (sIL-6R) forms. Prevailing dogma is that vascular endothelial cells do not produce IL-6R, relying on trans-signaling during inflammation. However, the literature is inconsistent, including with respect to human retinal endothelial cells. FINDINGS: We examined IL-6R transcript and protein expression in multiple primary human retinal endothelial cell isolates, and assessed the effect of IL-6 on the transcellular electrical resistance of monolayers. Using reverse transcription-polymerase chain reaction, IL-6R, mIL-6R and sIL-6R transcripts were amplified in 6  primary human retinal endothelial isolates. Flow cytometry on 5 primary human retinal endothelial cell isolates under non-permeabilizing conditions and following permeabilization demonstrated intracellular stores of IL-6R and the presence of mIL-6R. When measured in real-time, transcellular electrical resistance of an expanded human retinal endothelial cell isolate, also shown to express IL-6R, decreased significantly on treatment with recombinant IL-6 in comparison to non-treated cells across 5 independent experiments. CONCLUSIONS: Our findings indicate that human retinal endothelial cells produce IL-6R transcript and functional IL-6R protein. The potential for classic signaling in human retinal endothelial cells has implications for the development of therapeutics targeted against IL-6-mediated pathology in non-infectious uveitis.

Toxoplasma gondii tachyzoites cross retinal endothelium assisted by intercellular adhesion molecule-1 in vitro.

Retinal infection is the most common clinical manifestation of toxoplasmosis. The route by which circulating Toxoplasma gondii tachyzoites cross the vascular endothelium to enter the human retina is unknown. Convincing studies using murine encephalitis models have strongly implicated leukocyte taxis as one pathway used by the parasite to access target organs. To establish whether tachyzoites might also interact directly with vascular endothelium, we populated a transwell system with human ocular endothelial cells. Human retinal endothelial monolayers permitted transmigration of tachyzoites of RH and three natural isolate strains. Antibody blockade of intercellular adhesion molecule-1 significantly reduced this migration, but did not impact tachyzoite movement across an endothelial monolayer derived from the choroid, which lies adjacent to the retina within the eye. In demonstrating that tachyzoites are capable of independent migration across human vascular endothelium in vitro, this study carries implications for the development of therapeutics aimed at preventing access of T. gondii to the retina.

Transcriptomic Responses of Human Retinal Vascular Endothelial Cells to Inflammatory Cytokines.

Purpose: Molecular profiling of human retinal endothelial cells provides opportunities to understand the roles of this cell population in maintenance of the blood-ocular barrier, and its involvements in diverse retinal vasculopathies. We aimed to generate a transcriptome of human retinal endothelial cells in the unstimulated state, and following treatment with inflammatory cytokines linked to cell dysfunction. Methods: Endothelial cells were isolated from retinae of five human cadaveric donors, and treated for 60 minutes and 24 hours with interleukin-1ß or tumor necrosis factor-α, or exposed to medium alone for the same intervals. Expression of intercellular adhesion molecule-1 was measured by RT-qPCR to confirm cytokine-induced activation of the cells. RNA was sequenced on the Illumina NovaSeq 6000 platform. Reads were aligned to the human GRCh38 genome, and reads that aligned to Ensembl-annotated genes were counted. Quality control of sequencing was performed with FastQC, and sequences were classified by Kraken. Results: A human retinal endothelial cell RNA-sequencing dataset with mean of 99% reads aligned to the human genome was produced as raw RNA sequence data (FASTQ files) and processed read data (XLSX files). Multidimensional scaling analysis showed a strong donor effect, which was readily controlled by ComBat. Conclusions: Our dataset may be useful for human retinal endothelial cell transcriptomic assemblies, functional gene annotating and/or gene expression and enrichment analyses, as well as cross-dataset harmonization. Translational Relevance: The molecular profile of the human retinal endothelium is a source of candidate biologic targets for retinal vasculopathies.

Infection of Human Retinal Pigment Epithelial Cells with Dengue Virus Strains Isolated during Outbreaks in Singapore.

Prevalence of dengue retinopathy varies across epidemics, with the disease linked to circulation of dengue virus serotype 1 (DENV-1). The retinal pigment epithelium has been implicated in the pathology. We investigated infectivity, molecular response, and barrier function of epithelial cells inoculated with DENV strains from different outbreaks in Singapore. Monolayers of human retinal pigment epithelial cells (multiple primary cell isolates and the ARPE-19 cell line) were inoculated with six DENV strains, at multiplicity of infection of 10; uninfected and recombinant strain-infected controls were included where relevant. Infectivity and cell response were assessed primarily by RT-qPCR on total cellular RNA, and barrier function was evaluated as electrical resistance across monolayers. Higher viral RNA loads were measured in human retinal pigment epithelial cells infected with DENV-1 strains from the 2005 Singapore epidemic, when retinopathy was prevalent, versus DENV-1 strains from the 2007 Singapore epidemic, when retinopathy was not observed. Type I interferon (IFN) transcripts (IFN-ß and multiple IFN-stimulated genes) were up-regulated, and impact on barrier function was more pronounced, for cells infected with DENV-1 strains from the 2005 versus the 2007 Singapore epidemics. Aside from serotype, strain of DENV may determine the potential to induce retinal pathology. Identification of molecular markers of disease-associated DENV strains may provide insights into the pathogenesis of dengue retinopathy.

Pathogenesis of ocular toxoplasmosis.

Ocular toxoplasmosis is a retinitis -almost always accompanied by vitritis and choroiditis- caused by intraocular infection with Toxoplasma gondii. Depending on retinal location, this condition may cause substantial vision impairment. T. gondii is an obligate intracellular protozoan parasite, with both sexual and asexual life cycles, and infection is typically contracted orally by consuming encysted bradyzoites in undercooked meat, or oocysts on unwashed garden produce or in contaminated water. Presently available anti-parasitic drugs cannot eliminate T. gondii from the body. In vitro studies using T. gondii tachyzoites, and human retinal cells and tissue have provided important insights into the pathogenesis of ocular toxoplasmosis. T. gondii may cross the vascular endothelium to access human retina by at least three routes: in leukocyte taxis; as a transmigrating tachyzoite; and after infecting endothelial cells. The parasite is capable of navigating the human neuroretina, gaining access to a range of cell populations. Retinal Müller glial cells are preferred initial host cells. T. gondii infection of the retinal pigment epithelial cells alters the secretion of growth factors and induces proliferation of adjacent uninfected epithelial cells. This increases susceptibility of the cells to parasite infection, and may be the basis of the characteristic hyperpigmented toxoplasmic retinal lesion. Infected epithelial cells also generate a vigorous immunologic response, and influence the activity of leukocytes that infiltrate the retina. A range of T. gondii genotypes are associated with human ocular toxoplasmosis, and individual immunogenetics -including polymorphisms in genes encoding innate immune receptors, human leukocyte antigens and cytokines- impacts the clinical manifestations. Research into basic pathogenic mechanisms of ocular toxoplasmosis highlights the importance of prevention and suggests new biological drug targets for established disease.

Zika Virus Infection of Human Iris Pigment Epithelial Cells.

During recent Zika epidemics, adults infected with Zika virus (ZIKV) have developed organ-specific inflammatory complications. The most serious Zika-associated inflammatory eye disease is uveitis, which is commonly anterior in type, affecting both eyes and responding to corticosteroid eye drops. Mechanisms of Zika-associated anterior uveitis are unknown, but ZIKV has been identified in the aqueous humor of affected individuals. The iris pigment epithelium is a target cell population in viral anterior uveitis, and it acts to maintain immune privilege within the anterior eye. Interactions between ZIKV and human iris pigment epithelial cells were investigated with infectivity assays and RNA-sequencing. Primary cell isolates were prepared from eyes of 20 cadaveric donors, and infected for 24 hours with PRVABC59 strain ZIKV or incubated uninfected as control. Cytoimmunofluorescence, RT-qPCR on total cellular RNA, and focus-forming assays of culture supernatant showed cell isolates were permissive to infection, and supported replication and release of infectious ZIKV. To explore molecular responses of cell isolates to ZIKV infection at the whole transcriptome level, RNA was sequenced on the Illumina NextSeq 500 platform, and results were aligned to the human GRCh38 genome. Multidimensional scaling showed clear separation between transcriptomes of infected and uninfected cell isolates. Differential expression analysis indicated a vigorous molecular response of the cell to ZIKV: 7,935 genes were differentially expressed between ZIKV-infected and uninfected cells (FDR < 0.05), and 99% of 613 genes that changed at least two-fold were up-regulated. Reactome and KEGG pathway and Gene Ontology enrichment analyses indicated strong activation of viral recognition and defense, in addition to biosynthesis processes. A CHAT network included 6275 molecular nodes and 24 contextual hubs in the cell response to ZIKV infection. Receptor-interacting serine/threonine kinase 1 (RIPK1) was the most significantly connected contextual hub. Correlation of gene expression with read counts assigned to the ZIKV genome identified a negative correlation between interferon signaling and viral load across isolates. This work represents the first investigation of mechanisms of Zika-associated anterior uveitis using an in vitro human cell model. The results suggest the iris pigment epithelium mounts a molecular response that limits intraocular pathology in most individuals.

Model Systems for Studying Mechanisms of Ocular Toxoplasmosis.

The most common human disease caused by infection with Toxoplasma gondii is ocular toxoplasmosis, which typically is manifest as recurrent attacks of necrotizing retinal inflammation with subsequent scarring. The multilayered retina contains specialized cell populations, including endothelial cells, epithelial cells, neurons and supporting cells, all of which may be involved in this condition. In vitro investigations of basic mechanisms operating in human ocular toxoplasmosis use cellular and molecular methods that are common to the study of many pathological processes, and the novel aspect of this research is the use of human retinal cell subsets. Most in vivo research on ocular toxoplasmosis is conducted in the laboratory mouse. Experimental models involve local or systemic inoculation of parasites to induce acute disease, or sequential systemic and local parasite inoculations to trigger recurrent disease. We present methods for in vitro and in vivo studies of ocular toxoplasmosis, including dissection of the human eye, and culture and infection of differentiated cell populations from the retina, as well as induction of mouse ocular toxoplasmosis by intraocular, or sequential systemic and intraocular, inoculations, and imaging of toxoplasmic retinal lesions.

Lamb as a potential source of Toxoplasma gondii infection for Australians.

OBJECTIVE: Toxoplasmosis may follow consumption of undercooked meat containing Toxoplasma gondii cysts. Lamb is considered to pose the highest risk for contamination across meats. Red meat is often served undercooked, yet there are no current data on T. gondii contamination of Australian sourced and retailed lamb. We sought to address this gap in public health knowledge. METHODS: Lamb mincemeat was purchased at the supermarket counter three times weekly for six months. T. gondii was detected by real-time polymerase chain reaction (PCR) of DNA extracted from the meat following homogenisation. Purchases were also tested for common foodborne bacterial pathogens. RESULTS: Conservative interpretation of PCR testing (i.e. parasite DNA detected in three of four tests) gave a probability of 43% (95% confidence interval, 32%-54%) that lamb mincemeat was contaminated with T. gondii. None of the purchases were contaminated with Campylobacter jejuni, Salmonella species or S. enterica serovar Typhimurium, indicating sanitary meat processing. CONCLUSIONS: Australian lamb is commonly contaminated with T. gondii. Future studies should be directed at testing a range of red meats and meat cuts. Implications for public health: Consuming undercooked Australian lamb has potential to result in toxoplasmosis. There may be value in health education around this risk.

Expression of Long Non-Coding RNAs by Human Retinal Müller Glial Cells Infected with Clonal and Exotic Virulent Toxoplasma gondii.

Retinal infection with Toxoplasma gondii-ocular toxoplasmosis-is a common cause of vision impairment worldwide. Pathology combines parasite-induced retinal cell death and reactive intraocular inflammation. Müller glial cells, which represent the supporting cell population of the retina, are relatively susceptible to infection with T. gondii. We investigated expression of long non-coding RNAs (lncRNAs) with immunologic regulatory activity in Müller cells infected with virulent T. gondii strains-GT1 (haplogroup 1, type I) and GPHT (haplogroup 6). We first confirmed expression of 33 lncRNA in primary cell isolates. MIO-M1 human retinal Müller cell monolayers were infected with T. gondii tachyzoites (multiplicity of infection = 5) and harvested at 4, 12, 24, and 36 h post-infection, with infection being tracked by the expression of parasite surface antigen 1 (SAG1). Significant fold-changes were observed for 31 lncRNAs at one or more time intervals. Similar changes between strains were measured for BANCR, CYTOR, FOXD3-AS1, GAS5, GSTT1-AS1, LINC-ROR, LUCAT1, MALAT1, MIR22HG, MIR143HG, PVT1, RMRP, SNHG15, and SOCS2-AS1. Changes differing between strains were measured for APTR, FIRRE, HOTAIR, HOXD-AS1, KCNQ1OT1, LINC00968, LINC01105, lnc-SGK1, MEG3, MHRT, MIAT, MIR17HG, MIR155HG, NEAT1, NeST, NRON, and PACER. Our findings suggest roles for lncRNAs in regulating retinal Müller cell immune responses to T. gondii, and encourage future studies on lncRNA as biomarkers and/or drug targets in ocular toxoplasmosis.