Immune Mediator Profile in Aqueous Humor Differs in Patients with Primary Acquired Ocular Toxoplasmosis and Recurrent Acute Ocular Toxoplasmosis

The role of age in ocular toxoplasmosis: clinical signs of immunosenescence and inflammaging

Purpose

This study aimed to investigate the association between age, immune response, and clinical presentation of ocular toxoplasmosis (OT).

Design

This was a monocentric, retrospective, observational cohort study.

Methods

A review of the medical records of patients with active OT at the Uveitis Center, Charité Universitätsmedizin, was conducted. Baseline parameters included age at presentation, visual acuity, intraocular pressure (IOP), size and location of active lesions, inflammatory activity, antibody index (AI), and complications of intraocular inflammation. The data were presented as the mean ± standard deviation (SD). The level of significance was set at a p-value of <0.05.

Results

Between 1998 and 2019, 290 patients with active OT were diagnosed at our tertiary reference center. The mean age of the participants was 37.7 ± 17.1 years, 53.8% of them were female individuals, and 195 patients (70.9%) showed recurrent disease. Older age was associated with lower baseline visual acuity (p = 0.043), poor visual outcome (p = 0.019), increased inflammatory activity (p < 0.005), and larger retinal lesions (p < 0.005). Older patients presented a lower AI (<35 years: 45.1 ± 82.7, median: 12.1; ≥35 years: 18.6 ± 50.5, median: 5.8; p = 0.046), confirmed by a decrease in AI with increasing age (R2 = 0.045; p = 0.024). Finally, AI was correlated with lesion size (multiple linear regression analysis: p = 0.043). Macular involvement (24.3% of patients) was positively correlated with complications (macular/peripapillary edema and retinal detachment, p < 0.005) and poor visual outcome (p < 0.005) and was negatively correlated with inflammatory activity (p < 0.005).

Conclusion

We found a strong and clinically relevant impact of age on the clinical presentation and course of OT. While an unspecific inflammatory response increased with age, the specific, local humoral immune response declined. These findings are well in line with the concept of immunosenescence and inflammaging in uveitis.

Dynamic immune profile in French toxoplasmosis patients

BACKGROUND

Toxoplasma gondii infection is usually benign in Europe due to the strong predominance of type II strains. Few studies have been conducted to examine the immunological course of infection in humans and have yielded conflicting results, maybe influenced by heterogeneous parasite strains.

METHODS

We measured 23 immune mediators in 39, 40, and 29 sera of French non-infected, acutely infected, and chronically infected immunocompetent pregnant women, respectively.

RESULTS

Four different cytokine patterns were identified regarding their dynamics through infection phases. For eleven of the cytokines, IFN-β, IFN-γ, IL-4, IL5, IL-6, IL-10, IL-12, IL-15, CXCL9, CCL2 and CSF2, the serum levels were significantly elevated during acute infection. The inflammatory mediators IL-1β, IL-17A, IL-18, TNF-α and CSF3 remained unchanged during acute infection, while they were significantly lower in chronically infected compared to non-infected patients. As for the anti-inflammatory cytokines TGF-β and CCL5, their levels remained significantly elevated during chronic infection. We also observed a significant negative correlation of several cytokine concentrations with IgG levels, indicating a rapid decline of serum concentrations during the acute phase.

DISCUSSION

These results indicate an anti-inflammatory pattern in chronically infected patients in a type II dominated setting and demonstrate the highly dynamic immune situation during acute infection.

Local and systemic gene expression levels of IL-10, IL-17 and TGF-β in active ocular toxoplasmosis in humans

BACKGROUND

To compare mRNA expression of interleukin 10 (IL-10), interleukin 17 (IL-17) and Transforming Growth Factor-β (TGF-β) in aqueous humor (AH) and peripheral blood mononuclear cells (PBMCs) in human ocular toxoplasmosis (OT) and controls.

METHOD

RNA isolation, cDNA synthesis and real-time polymerase chain reaction were performed on AH sediments and PBMCs of 16 patients with active OT and 21 controls at the Khatam-al-Anbia Eye Hospital, Iran. For comparison, Mann Whitney U test was used at a discrimination level of p < 0.05. Pearson and Spearman rank correlation test were applied for correlation with clinical parameters.

RESULTS

The expression for IL-10 and IL-17 in the AH was 3.7- and 88.0-fold higher in OT than in controls (P = 0.04 and P = 0.03, respectively) whereas that of TGF-β was 7.7-fold lower (P < 0.001). The expression levels for these cytokines in PBMC followed a similar pattern (IL-10 13.8-fold down-regulated (P = 0.001), IL-17 with 1.9-fold insignificantly upregulated (p = 0.43), TGF-β 452.8-fold down-regulated (P = 0.002). Compared to PBMC, IL-10 coding mRNA was 1876-fold higher in the almost cell-free AH in OT (39.2-fold in controls), IL-17 coding mRNA was 9.4-fold higher (17.7-fold down-regulated in controls), and that coding for TGF-β 207-fold higher in OT (7x10⁵-fold in controls). The expression for IL-10, IL-17 and TGF-β in AH thus followed an opposite pattern compared to that in PBMC.

CONCLUSION

OT induces a highly-specific local immunoregulatory process as evidenced by an intraocular up-regulation of IL-10 and down-regulation of TGF-β mRNA. This could indicate an attempt to prevent unnecessary tissue damage which is in line with a moderate local mRNA up-regulation for IL-17 which seems sufficient to control parasite proliferation. That this regulation is opposite to that in PBMC may be linked to intraocular immune deviation in the course of disease.

Structural Endpoints and Outcome Measures in Uveitis

Most uveitis entities are rare diseases but, taken together, are responsible for 5-10% of worldwide visual impairment which largely affects persons of working age. As with many rare diseases, there is a lack of high-level evidence regarding its clinical management, partly due to a dearth of reliable and objective quantitative endpoints for clinical trials. This review provides an overview of available structural outcome measures for uveitis disease activity and damage in an anatomical order from the anterior to the posterior segment of the eye. While there is a multitude of available structural outcome measures, not all might qualify as endpoints for clinical uveitis trials, and thorough testing of applicability is warranted. Furthermore, a consensus on endpoint definition, standardization, and "core outcomes" is required. As stipulated by regulatory agencies, endpoints should be precisely defined, clinically important, internally consistent, reliable, responsive to treatment, and relevant for the respective subtype of uveitis. Out of all modalities used for assessment of the reviewed structural outcome measures, optical coherence tomography, color fundus photography, fundus autofluorescence, and fluorescein/indocyanine green angiography represent current "core modalities" for reliable and objective quantification of uveitis outcome measures, based on their practical availability and the evidence provided so far.

Treatment Strategy in Human Ocular Toxoplasmosis: Why Antibiotics Have Failed

Background: There is currently no clear evidence of the effectiveness of antibiotic therapy in acute ocular toxoplasmosis (OT), but its effect as a secondary prophylaxis is undisputed. The majority of uveitis specialists advocate treatment. This meta-analytic review aims to critically analyze determinants of treatment success and to update current treatment strategies for OT in order to explain this discrepancy. Methods: A systematic literature search was performed in NCBI/PubMed, Clinical Trials, Google Scholar and ScienceDirect to retrieve pro- and retrospective studies using the key terms “ocular toxoplasmosis” or “retinochoroiditis” and “immunocompetent” and “treatment” or “therapy” and “human.” Of these, larger case series and prospective clinical studies and cross references identified from meta-analyses were selected by a manual search, and primary and secondary outcome parameters were extracted. Results: Ten case series and clinical trials reported success parameters for treatment outcomes, and four additional for recurrence prophylaxis. Five treatment studies were randomized clinical trials, three comparative and two noncomparative case series. Though several outcome parameters were reported, five of them defined time to healing, four visual gain and one lesion size as primary and secondary outcome parameters, recurrence rate as a secondary outcome parameter was reported once. No conclusive evidence was found for an antibiotic treatment effect. Four prophylaxis studies addressed the prevention of recurrences after treatment. The primary outcome in all studies was the effect of treatment and prophylaxis on recurrences, and all four found a significant effect on the risk of and time to recurrences. Conclusions: Antibiotic treatment of OT aims at controlling parasite proliferation. The absence of an effect on visual acuity and time to healing is thus not surprising. The fact that time to and number of recurrences respond to recurrence of prophylaxis proves the antibiotic effect on parasite activity.

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-1β, IL-6, IL-10, IL-12(p40), IL-12(p70), CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β, 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-1β, 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.

Pathophysiology of ocular toxoplasmosis: Facts and open questions

Infections with the protozoan parasite Toxoplasma gondii are frequent, but one of its main consequences, ocular toxoplasmosis (OT), remains poorly understood. While its clinical description has recently attracted more attention and publications, the underlying pathophysiological mechanisms are only sparsely elucidated, which is partly due to the inherent difficulties to establish relevant animal models. Furthermore, the particularities of the ocular environment explain why the abundant knowledge on systemic toxoplasmosis cannot be just transferred to the ocular situation. However, studies undertaken in mouse models have revealed a central role of interferon gamma (IFNγ) and, more surprisingly, interleukin 17 (IL17), in ocular pathology and parasite control. These studies also show the importance of the genetic background of the infective Toxoplasma strain. Indeed, infections due to exotic strains show a completely different pathophysiology, which translates in a different clinical outcome. These elements should lead to more individualized therapy. Furthermore, the recent advance in understanding the immune response during OT paved the way to new research leads, involving immune pathways poorly studied in this particular setting, such as type I and type III interferons. In any case, deeper knowledge of the mechanisms of this pathology is needed to establish new, more targeted treatment schemes.

Putative biomarkers for early diagnosis and prognosis of congenital ocular toxoplasmosis

In the present study we have evaluated the performance of several immunological biomarkers for early diagnosis and prognosis of congenital toxoplasmosis. Our results showed that ex vivo serum levels of CXCL9, and the frequencies of circulating CD4⁺CD25⁺ T-cells and T. gondii-specific IFN-γ⁺CD4⁺ T-cells measured 30–45 days after birth presented high accuracy to distinguish T. gondii-infected infants from healthy age-matched controls (Global Accuracy/AUC = 0.9; 0.9 and 0.8, respectively). Of note was the enhanced performance (Accuracy = 96%) achieved by using a combined stepwise analysis of CD4⁺CD25⁺ T-cells and CXCL9. In addition, high global accuracy (AUC = 0.9) with elevated sensitivity (Se = 98%) was also reached by using the total frequency of in vitro IFN-γ-producing T. gondii-specific T-cells (∑ IFN-γ⁺ CD4⁺ & CD8⁺) as a biomarker of congenital toxoplasmosis. Furthermore, the analysis of in vitro T. gondii-specific IL5⁺CD4⁺ T-cells and IFN-γ⁺NK-cells displayed a high accuracy for early prognosis of ocular lesion in infant with congenital toxoplasmosis (Global Accuracy/AUC = 0.8 and 0.9, respectively). Together, these findings support the relevance of employing the elements of the cell-mediated immune response as biomarkers with potential to endorse early diagnosis and prognosis of congenital ocular toxoplasmosis to contribute for a precise clinical management and effective therapeutic intervention.

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.

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

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.

A study of 51 subtypes of peripheral blood immune cells in newly diagnosed young type 1 diabetes patients

Type 1 diabetes (T1D) results from autoimmune destruction of insulin-producing beta cells in pancreatic islets. Various immune cell populations are involved in disease development and natural course. However, to our knowledge, so far there are no comprehensive comparative investigations of all main immune cell populations and their most important subsets at the onset of disease. Therefore, in the current study, we analyzed 51 peripheral blood immune cell populations in 22 young T1D patients and in 25 age-matched controls using a comprehensive polychromatic flow cytometry panel developed for whole blood by the COST Action no. BM0907 ENTIRE (European Network for Translational Immunology Research and Education: From Immunomonitoring to Personalized Immunotherapy) consortium. We found that in T1D patients, frequencies and absolute counts of natural killer (NK) cells, dendritic cells (DC) and T cells, as well as their respective subsets, were significantly altered compared to controls. Further, we observed that changes in several cell populations (e.g. CD14⁺ CD16⁺ non-classical monocytes, plasmablasts) were dependent on the age of the patient. In addition to age-related changes, we also found that alterations in immune cell patterns were associated with parameters such as the presence of ketoacidosis and C-peptide serum levels. Our study provides a foundation for future studies investigating different cell lineages and their role in T1D and illustrates the value of polychromatic flow cytometry for evaluating all main peripheral immune cells and their subsets in whole blood samples.

Case Report: Ocular toxoplasmosis in a WHIM syndrome immunodeficiency patient

A patient with WHIM syndrome immunodeficiency presented with sudden painless right eye blindness associated with advanced retinal and optic nerve damage. Toxoplasma gondii was detected by PCR in vitreous fluid but not serum.  The patient was treated with pyrimethamine/sulfadiazine for 6 weeks due to evidence of active ocular inflammation and then received prophylaxis with trimethoprim-sulfamethoxazole due to his immunosuppression.  Vision did not return; however, the infection did not spread to involve other sites.  Toxoplasmosis is rare in primary immunodeficiency disorders and is the first protozoan infection reported in WHIM syndrome.

Case Report: Ocular toxoplasmosis in a WHIM syndrome immunodeficiency patient

A patient with WHIM syndrome immunodeficiency presented with sudden painless right eye blindness associated with advanced retinal and optic nerve damage. Toxoplasma gondii was detected by PCR in vitreous fluid but not serum.  The patient was treated with trimethoprim-sulfamethoxazole.  Vision did not return; however, the infection did not spread to involve other sites.  Toxoplasmosis is rare in primary immunodeficiency disorders and is the first protozoan infection reported in WHIM syndrome.