Human S-antigen: peptide determinant recognition in uveitis patients

Retina-arrestin specific CD8+ T cells are not implicated in HLA-A29-positive birdshot chorioretinitis

BACKGROUND

HLA-A29-positive birdshot chorioretinitis (BCR) is an inflammatory eye disorder that is generally assumed to be caused by an autoimmune response to HLA-A29-presented peptides from retinal arrestin (SAG), yet the epitopes recognized by CD8+ T cells from patients remain to be identified.

OBJECTIVES

The identification of natural ligands of SAG presented by HLA-A29. To quantify CD8+ T cells reactive to antigenic SAG peptides presented by HLA-A29 in patients and controls.

METHODS

We performed mass-spectrometry based immunopeptidomics of HLA-A29 of antigen-presenting cell lines from patients engineered to express SAG. MHC-I Dextramer technology was utilised to determine expansion of antigen-specific CD8+ T cells reactive to SAG peptides in complex with HLA-A29 in a cohort of BCR patients, HLA-A29-positive controls, and HLA-A29-negative controls.

RESULTS

We report on the naturally presented antigenic SAG peptides identified by sequencing the HLA-A29 immunopeptidome of antigen-presenting cells of patients. We show that the N-terminally extended SAG peptide precursors can be trimmed in vitro by the antigen-processing aminopeptidases ERAP1 and ERAP2. Unexpectedly, no enhanced antigen engagement by CD8+ T cells upon stimulation with SAG peptides was observed in patients or HLA-A29-positive controls. Multiplexed HLA-A29-peptide dextramer profiling of a case-control cohort revealed that CD8+ T cells specific for these SAG peptides were neither detectable in peripheral blood nor in eye biopsies of patients.

CONCLUSIONS

Collectively, these findings demonstrate that SAG is not a CD8+ T cell autoantigen and sharply contrast the paradigm in the pathogenesis of BCR. Therefore, the mechanism by which HLA-A29 is associated with BCR does not involve SAG.

Tubercular serpiginous choroiditis

Tubercular association with serpiginous choroiditis, also called ‘serpiginous-like choroiditis’ or ‘multifocal serpiginoid choroiditis’ (MSC) is reported from world over, especially from endemic countries. Though the exact mechanism is not yet clear, a direct or indirect infectious trigger by Mycobacterium tuberculosis (MTB) is believed to cause choroiditis.

The link of immune mechanisms with ocular inflammation caused by MTB is emerging, and has been supported by both experimental and human data. The molecular and histopathological findings of tubercular serpiginous-like choroiditis have been demonstrated in clinicopathological reports, as well as in animal models. Young to middle-aged healthy males are more frequently affected. The choroiditis lesions of tubercular serpiginous-like choroiditis evolve as multifocal lesions, affecting the retinal periphery as well as posterior pole. They begin as discrete lesions, and spread in a serpiginoid pattern to become confluent. Fundus imaging including autofluorescence is extremely helpful in monitoring patients for response to therapy. Its diagnosis is essentially clinical. Corroborative evidence is obtained by a positive tuberculin skin test, or a positive QuantiFERON-TB Gold (Cellestis, Carnegie, Victoria, Australia) test, and/or radiological (chest X-ray or chest CT scan) evidence of TB elsewhere in the body. Systemic corticosteroids are the mainstay of therapy to control active inflammation, while ATT helps to reduce recurrence of inflammatory attacks. Immunosuppressive agents are indicated in cases with relentless progression, paradoxical worsening, or recurrent choroiditis.

Disrupted Neural Activity in Individuals With Iridocyclitis Using Regional Homogeneity: A Resting-State Functional Magnetic Resonance Imaging Study

Objective: This study used the regional homogeneity (ReHo) technique to explore whether spontaneous brain activity is altered in patients with iridocyclitis.

Methods: Twenty-six patients with iridocyclitis (14 men and 12 women) and 26 healthy volunteers (15 men and 11 women) matched for sex and age were enrolled in this study. The ReHo technique was used to comprehensively assess changes in whole-brain synchronous neuronal activity. The diagnostic ability of the ReHo method was evaluated by means of receive operating characteristic (ROC) curve analysis. Moreover, associations of average ReHo values in different brain areas and clinical characteristics were analyzed using correlation analysis.

Result: Compared with healthy volunteers, reduced ReHo values were observed in patients with iridocyclitis in the following brain regions: the right inferior occipital gyrus, bilateral calcarine, right middle temporal gyrus, right postcentral gyrus, left superior occipital gyrus, and left precuneus. In contrast, ReHo values were significantly enhanced in the right cerebellum, left putamen, left supplementary motor area, and left inferior frontal gyrus in patients with iridocyclitis, compared with healthy volunteers (false discovery rate correction, P < 0.05).

Conclusion: Patients with iridocyclitis exhibited disturbed synchronous neural activities in specific brain areas, including the visual, motor, and somatosensory regions, as well as the default mode network. These findings offer a novel image-guided research strategy that might aid in exploration of neuropathological or compensatory mechanisms in patients with iridocyclitis.

Hypomethylation of Notch1 DNA is associated with the occurrence of uveitis

Uveitis is a serious intra-ocular inflammatory disease that can lead to visual impairment even blindness worldwide. Notch signaling can regulate the differentiation of naive CD4⁺ T cells, influencing the development of uveitis. DNA methylation is closely related to the autoimmune diseases. In this study, we measured the Notch1 DNA methylation level, determined the Notch1 and related DNA methylases mRNA expression and evaluated the ratio of T helper type 17 regulatory T cell (Th17/T_reg ) in peripheral blood mononuclear cells (PBMCs) from uveitis patients and normal control subjects; we also tested the levels of relevant inflammatory cytokines in serum from the participants. Results indicated that compared with those in normal control individuals, the expression of ten-eleven translocation 2 (TET2) and Notch1 mRNA is elevated in uveitis patients, whereas the methylation level in Notch1 DNA promotor region [-842 ~ -646 base pairs (bp)] is down-regulated, and is unrelated to anatomical location. Moreover, the Th17/T_reg ratio is up-regulated in PBMCs from uveitis patients, accompanied by the elevated levels of proinflammatory cytokines [e.g. interleukin (IL)-2, IL-6, IL-17 and interferon (IFN)-γ] in serum from uveitis patients. These findings suggest that the over-expression of TET2 DNA demethylase may lead to hypomethylation of Notch1, activate the Notch1 signaling, induce naive CD4⁺ T cells to differentiate theTh17 subset and thus disturb the balance of the Th17/T_reg ratio in uveitis patients. Overall, hypomethylation of Notch1 DNA is closely associated with the occurrence of uveitis. Our study preliminarily reveals the underlying mechanism for the occurrence of uveitis related to the hypomethylation of Notch1 DNA, providing a novel therapeutic strategy against uveitis in clinical practice.

Autoimmunity, Autoinflammation, and Infection in Uveitis

PURPOSE

To review the pathogenesis of uveitis in light of recent advances in our understanding of innate and adaptive immune responses and their regulation.

DESIGN

Perspective.

METHODS

Methods included a review of prevailing views on the pathogenesis of uveitis and an analysis of developments in immunology that impact on its conceptual basis, particularly the concept of immunologic tolerance and its loss in autoimmunity. Importantly, the role of infection in the pathogenesis of uveitis is evaluated.

RESULTS

The results comprise a reappraisal of the pathogenesis of anterior vs posterior uveitis in the context of the blood-retinal barrier and its relation to autoimmune, autoinflammatory, and infectious uveitis. Autoimmunity is seen as a possible cause of certain forms of uveitis but definitive proof is lacking. Autoinflammatory disease, involving activated innate immune mechanisms, is considered causative in a second set of uveitis conditions. A place for infection in uveitis generally is proposed within a unifying concept for the pathogenesis of uveitis.

CONCLUSION

Infection may be implicated directly or indirectly in many forms of noninfectious or undifferentiated uveitis. In addition to the growing recognition that foreign antigen, including reactivatable infectious agents, might hide within ocular tissues, the possibility that a dysregulated microbiome might generate T cells that cause immune-mediated ocular inflammation has now been demonstrated experimentally. An uncontrolled, overexuberant host immune response may cause continuing irreversible tissue damage even after the infection has been cleared.

Effective Arrestin-Specific Immunotherapy of Experimental Autoimmune Uveitis with RTL: A Prospect for Treatment of Human Uveitis

PURPOSE

To evaluate the immunotherapeutic efficacy of recombinant T cell receptor ligands (RTLs) specific for arrestin immunity in treatment of experimental autoimmune uveitis (EAU) in humanized leukocyte antigen (HLA-DR3) transgenic (Tg) mice.

METHODS

We generated de novo recombinant human DR3-derived RTLs bearing covalently tethered arrestin peptides 291-310 (RTL351) or 305-324 (RTL352). EAU was induced by immunization of HLA-DR3 mice with arrestin or arrestin peptide and treated with RTLs by subcutaneous delivery. T cell proliferation and cytokine expression was measured in RTL-treated and control mice.

RESULTS

RTL351 prevented the migration of cells outside of the spleen and the recruitment of inflammatory cells into the eye, and provided full protection against inflammation from EAU induced with arrestin or arrestin peptides. RTL351 significantly inhibited T cell proliferation and secretion of inflammatory cytokines interleukin 2 (IL-2), interferon γ (IFN-γ), IL-6, and IL-17 and chemokines (macrophage inflammatory proteins [MIP-1a] and regulated and normal T cell expressed and secreted [RANTES]), which is in agreement with the suppression of intraocular inflammation. RTL350 ("empty," no peptide) and RTL352 were not effective.

CONCLUSIONS

Immunotherapy with a single RTL351 successfully prevented and treated arrestin-induced EAU in HLA-DR3 mice and provided proof of concept for therapy of autoimmune uveitis in human patients. The beneficial effects of RTL351 should be attributed to a significant decrease in Th1/Th17 mediated inflammation.

TRANSLATIONAL RELEVANCE

Successful therapies for autoimmune uveitis must specifically inhibit pathogenic inflammation without inducing generalized immunosuppression. RTLs can offer such an option. The single retina-specific RTLs may have a value as potential immunotherapeutic drug for human autoimmune uveitis because they effectively prevent disease induced by multiple T cell specificities.

IFN-β inhibits the increased expression of IL-9 during experimental autoimmune uveoretinitis

Purpose

It has been shown that IL-9 plays a proinflammatory role in the pathogenesis of certain autoimmune diseases. This study was designed to investigate the possible role of IL-9 in the development of experimental autoimmune uveoretinitis (EAU) and the effect of IFN-β on its expression.

Methods

EAU was induced in B10RIII mice by immunization with interphotoreceptor retinoid-binding protein peptide 161–180 (IRBP_161–180). IFN-β was administered subcutaneously to IRBP_161–180 immunized mice every other day from day one before immunization to the end of the study. Splenocytes and draining lymph node (DLN) cells from EAU mice or control mice or EAU mice treated with IFN-β or PBS were stimulated with anti-CD3/CD28 or IRBP_161–180 for 3 days. Naïve T cells cultured under Th1 or Th17 polarizing conditions were incubated in the presence or absence of IFN-β for 4 days. Effector/memory T cells were activated by anti-CD3/CD28 in the presence or absence of IFN-β for 3 days. IFN-β-treated monocytes were cocultured with naïve T cells or effector/memory T cells for 3 days. Culture supernatants were collected and IL-9 was detected by ELISA.

Results

IL-9 expression in splenocytes and DLN cells was increased in EAU mice during the inflammatory phase and returned back to lower levels during the recovery phase. IFN-β in vivo treatment significantly inhibited EAU activity in association with a down-regulated expression of IL-9. In vitro polarized Th1 and Th17 cells both secreted IL-9 and the addition of IFN-β suppressed production of IL-9 by both Th subsets. Beside its effect on polarized Th cells, IFN-β also suppressed the secretion of IL-9 by effector/memory T cells. However, IFN-β-treated monocytes had no effect on the production of IL-9 when cocultured with naïve or effector/memory T cells.

Conclusion

IL-9 expression is increased during EAU which could be suppressed by IFN-β.

Tumor necrosis factor-α-mediated severity of idiopathic retinal periphlebitis in young adults (Eales' disease): implication for anti-TNF-α therapy

Tumor necrosis factor-alpha (TNF-α) is a pleiotropic inflammatory cytokine. Tumor necrosis factor-alpha was evaluated in the serum samples of patients with idiopathic retinal periphlebitis in young adults (Eales' disease). Retinal periphlebitis was graded according to a new grading system based on severity of inflammation (grade 1-4). Quantification of the TNF-α levels was carried out using ELISA kit in the serum samples of young adults with idiopathic retinal periphlebitis (n = 17) and healthy controls (n = 17) of similar age. Tumor necrosis factor-α level was found to be significantly raised in cases with retinal periphlebitis as compared with controls (p < 0.001). Higher levels of TNF-α were found to be associated with increased severity of retinal periphlebitis. Tumor necrosis factor-α represents a novel target for controlling inflammatory activity in idiopathic retinal periphlebitis. Higher levels of TNF-α, in association with the increased severity of retinal periphlebitis, have implications for early anti-TNF-α therapy.

Interleukin-1 and tumor necrosis factor-alpha: novel targets for immunotherapy in Eales disease

BACKGROUND

Eales disease is an idiopathic obliterative vasculopathy that primarily affects the peripheral retina of young adults. The authors evaluated interleukin 1 beta (IL-1beta), interleukin-6 (IL-6), Interleukin-10 (IL-10), and tumor necrosis factor-alpha (TNF-alpha) in the serum of patients with Eales disease stages for the first time.

METHODS

The study group consisted of 45 consecutive patients of Eales disease [inflammatory stage (n = 15) and proliferative stage (n = 30)] and 28 healthy controls. Immunoassays for the quantification of the levels of four cytokines including IL-1beta, IL-6, IL-10, and TNF-alpha in the serum samples were performed using ELISA kits.

RESULTS

IL-1beta, IL-6, IL-10, and TNF-alpha levels were found to be increased significantly in the inflammatory stage of Eales disease as compared to controls (p < .001). IL-1beta levels decreased significantly during the proliferative stage of the disease as compared to the inflammatory stage (p = .03). TNF-alpha levels increased significantly during the proliferative stage as compared to the inflammatory stage (p = .02).

CONCLUSIONS

Raised levels of IL-1beta and TNF-alpha were observed in the inflammatory stage and persisted in the proliferative stage of the disease. The IL-1 system and TNF-alpha represent novel target for immunotherapy for controlling inflammatory activity and/or the associated long-term sequelae related to angiogenesis in Eales disease.

Immunotherapy of autoimmunity and cancer: the penalty for success

Advances in our understanding of autoimmunity and tumour immunity have led to improvements in immunotherapy for these diseases. Ironically, effective tumour immunity requires the induction of the same responses that underlie autoimmunity, whereas autoimmunity is driven by dysregulation of the same mechanisms that are involved in host defence and immune surveillance. Therefore, as we manipulate the immune system to treat cancer or autoimmunity, we inevitably unbalance the vital mechanisms that regulate self tolerance and antimicrobial resistance. This Science and Society article aims to dissect the conundrum that is inherent to the concept of immunotherapy and highlights the need for new and more specific therapeutic approaches.

Identification of Leishmania donovani antigens stimulating cellular immune responses in exposed immune individuals

Human visceral leishmaniasis (VL), also known as kala azar (KA) in India, is a systemic progressive disease caused by Leishmania donovani. In VL, Th1 responses correlate with recovery from and resistance to disease and resolution of infection results in lifelong immunity against the disease. However, recent data suggest an important role for interleukin (IL)-10 in maintaining the resistant state. We evaluated whole cell extract (WE) and 11 antigenic fractions [F1-F11, molecular weight (MW) range of 139-24.2 kDa] from L. donovani (2001 strain, a fresh field isolate from Bihar), for their ability to induce in vitro T cell proliferation and production of interferon (IFN)-gamma, interleukin (IL)-12, IL-10 and IL-4 by peripheral blood mononuclear cells (PBMCs) of exposed immune individuals (14 patients with history of VL, 10 household endemic contacts) and 20 non-endemic healthy controls. Twenty-one of 24 exposed individuals and no healthy controls showed proliferative response to WE. Whole-extract activated IFN-gamma, IL-12, IL-10 levels were higher in the exposed group than in controls; IL-4 was not detectable in any of the samples. Among 21 responders to WE, frequent proliferative responses were seen to fractions F1-F4 (MW > 64.2 kDa) and none to fractions F5-F11; fractions F1-F11 stimulated comparable levels of IFN-gamma and IL-12 while IL-10 levels were higher in response to F5-F11 compared to F1-F4. These data demonstrate the presence of immunostimulatory antigens in the high MW fractions of whole L. donovani antigen. However, these fractions do not stimulate a Th1 response and produce variable amounts of IFN-gamma and the regulatory cytokine, IL-10. Hence, these high MW immunostimulatory fractions need to be evaluated in greater depth for their possible role as protective antigens.