Spontaneous retinopathy in HLA-A29 transgenic mice

Diagnosing and Managing Uveitis Associated with Immune Checkpoint Inhibitors: A Review

This review aims to provide an understanding of the diagnostic and therapeutic challenges of uveitis associated with immune checkpoint inhibitors (ICI). In the wake of these molecules being increasingly employed as a treatment against different cancers, cases of uveitis post-ICI therapy have also been increasingly reported in the literature, warranting an extensive exploration of the clinical presentations, risk factors, and pathophysiological mechanisms of ICI-induced uveitis. This review further provides an understanding of the association between ICIs and uveitis, and assesses the efficacy of current diagnostic tools, underscoring the need for advanced techniques to enable early detection and accurate assessment. Further, it investigates the therapeutic strategies for ICI-related uveitis, weighing the benefits and limitations of existing treatment regimens, and discussing current challenges and emerging therapies in the context of their potential efficacy and side effects. Through an overview of the short-term and long-term outcomes, this article suggests recommendations and emphasizes the importance of multidisciplinary collaboration between ophthalmologists and oncologists. Finally, the review highlights promising avenues for future research and development in the field, potentially informing transformative approaches in the ocular assessment of patients under immunotherapy and the management of uveitis following ICI therapy.

Birdshot Chorioretinopathy in Early Adulthood: Review of Current Literature and Case Report

Purpose

We describe the course of a patient diagnosed with birdshot chorioretinopathy (BSCR) in early adulthood and summarize clinical findings from similar BSCR patients reported in the literature.

Observations

A 37-year-old male presented to our tertiary uveitis facility with bilateral ocular discomfort, hazy vision, and floaters. Ocular examination was notable for vitritis, optic disc edema, and ovoid hypopigmented chorioretinal lesions, visible on indocyanine green chorioangiography as multiple hypocyanescent spots in the intermediate phase. Full-field electroretinography and visual evoked potential showed global retinal dysfunction and optic nerve dysfunction. Laboratory evaluations were notable only for human leukocyte antigen (HLA)-A29 positivity. The patient was diagnosed with BSCR and started on oral prednisone and eventually managed with infliximab.

Conclusions and Importance

BSCR can affect patients in early adulthood. Proper diagnostic work-up, including assessing HLA-A29 positivity, is needed to manage atypical cases.

Classification Criteria for Birdshot Chorioretinitis

PURPOSE

To determine classification criteria for birdshot chorioretinitis.

DESIGN

Machine learning of cases with birdshot chorioretinitis and 8 other posterior uveitides.

METHODS

Cases of posterior uveitides were collected in an informatics-designed preliminary database, and a final database was constructed of cases achieving supermajority agreement on diagnosis, using formal consensus techniques. Cases were split into a training set and a validation set. Machine learning using multinomial logistic regression was used on the training set to determine a parsimonious set of criteria that minimized the misclassification rate among the infectious posterior uveitides / panuveitides. The resulting criteria were evaluated on the validation set.

RESULTS

One thousand sixty-eight cases of posterior uveitides, including 207 cases of birdshot chorioretinitis, were evaluated by machine learning. Key criteria for birdshot chorioretinitis included a multifocal choroiditis with (1) the characteristic appearance of a bilateral multifocal choroiditis with cream-colored or yellow-orange, oval or round choroidal spots ("birdshot" spots); (2) absent to mild anterior chamber inflammation; and (3) absent to moderate vitreous inflammation; or multifocal choroiditis with positive HLA-A29 testing and either classic "birdshot spots" or characteristic imaging on indocyanine green angiography. Overall accuracy for posterior uveitides was 93.9% in the training set and 98.0% (95% confidence interval 94.3, 99.3) in the validation set. The misclassification rates for birdshot chorioretinitis were 10% in the training set and 0% in the validation set.

CONCLUSIONS

The criteria for birdshot chorioretinitis had a low misclassification rate and seemed to perform sufficiently well for use in clinical and translational research.

Blocking the inflammasome: A novel approach to treat uveitis

Uveitis is a complex ocular inflammatory disease often accompanied by bacterial or viral infections (infectious uveitis) or underlying autoimmune diseases (non-infectious uveitis). Treatment of the underlying infection along with corticosteroid-mediated suppression of acute inflammation usually resolves infectious uveitis. However, to develop more effective therapies for non-infectious uveitis and to better address acute inflammation in infectious disease, an improved understanding of the underlying inflammatory pathways is needed. In this review, we discuss the disease aetiology, preclinical in vitro and in vivo uveitis models, the role of inflammatory pathways, as well as current and future therapies. In particular, we highlight the involvement of the inflammasome in the development of non-infectious uveitis and how it could be a future target for effective treatment of the disease.

HLA-A29 and Birdshot Uveitis: Further Down the Rabbit Hole

HLA class I alleles constitute established risk factors for non-infectious uveitis and preemptive genotyping of HLA class I alleles is standard practice in the diagnostic work-up. The HLA-A29 serotype is indispensable to Birdshot Uveitis (BU) and renders this enigmatic eye condition a unique model to better understand how the antigen processing and presentation machinery contributes to non-infectious uveitis or chronic inflammatory conditions in general. This review will discuss salient points regarding the protein structure of HLA-A29 and how key amino acid positions impact the peptide binding preference and interaction with T cells. We discuss to what extent the risk genes ERAP1 and ERAP2 uniquely affect HLA-A29 and how the discovery of a HLA-A29-specific submotif may impact autoantigen discovery. We further provide a compelling argument to solve the long-standing question why BU only affects HLA-A29-positive individuals from Western-European ancestry by exploiting data from the 1000 Genomes Project. We combine novel insights from structural and immunopeptidomic studies and discuss the functional implications of genetic associations across the HLA class I antigen presentation pathway to refine the etiological basis of Birdshot Uveitis.

HLA transgenic mice: application in reproducing idiosyncratic drug toxicity

Various types of transgenic mice carrying either class I or II human leukocyte antigen (HLA) molecules are readily available, and reports describing their use in a variety of studies have been published for more than 30 years. Examples of their use include the discovery of HLA-specific antigens against viral infection as well as the reproduction of HLA-mediated autoimmune diseases for the development of therapeutic strategies. Recently, HLA transgenic mice have been used to reproduce HLA-mediated idiosyncratic drug toxicity (IDT), a rare and unpredictable adverse drug reaction that can result in death. For example, abacavir-induced IDT has successfully been reproduced in HLA-B*57:01 transgenic mice. Several reports using HLA transgenic mice for IDT have proven the utility of this concept for the evaluation of IDT using various HLA allele combinations and drugs. It has become apparent that such models may be a valuable tool to investigate the mechanisms underlying HLA-mediated IDT. This review summarizes the latest findings in the area of HLA transgenic mouse models and discusses the current challenges that must be overcome to maximize the potential of this unique animal model.

Experimental autoimmune uveitis and other animal models of uveitis: An update

Over the past several decades, animal models of autoimmune uveitis directed at eye-specific antigens (Ags) have been developed. These have allowed researchers to understand the basic mechanisms that lead to these diseases and also recently helped the researchers in translational research for therapeutic interventions. Experimental autoimmune uveitis (EAU) is an animal disease model of human endogenous uveitis and can be induced in susceptible animals by immunization with retinal Ags. Ever since the first description of EAU in mice in 1988, several animal models of uveitis has been described by researchers. Disease-specific model for cytomegalovirus retinitis and tubercular uveitis has evolved our understanding of these complex entities. Endotoxin induced uveitis is another useful model for anterior uveitis, which is not an autoimmune process and is triggered by injection of bacterial endotoxin (lipopolysaccharides) resulting in a rapid short lasting uveitis. The current article will give an insight into the various EAU animal models and their current implications in translational research. The article will also highlight the different grading systems for EAU in the animal model.

Birdshot chorioretinopathy: current knowledge and new concepts in pathophysiology, diagnosis, monitoring and treatment

Birdshot chorioretinopathy (BCR) is a rare form of chronic, bilateral, posterior uveitis with a distinctive clinical phenotype, and a strong association with HLA-A29. It predominantly affects people in middle age. Given its rarity, patients often encounter delays in diagnosis leading to delays in adequate treatment, and thus risking significant visual loss. Recent advances have helped increase our understanding of the underlying autoimmune mechanisms involved in disease pathogenesis, and new diagnostic approaches such as multimodality imaging have improved our ability to both diagnose and monitor disease activity. Whilst traditional immunosuppressants may be effective in BCR, increased understanding of immune pathways is enabling development of newer treatment modalities, offering the potential for targeted modulation of immune mediators. In this review, we will discuss current understanding of BCR and explore recent developments in diagnosis, monitoring and treatment of this disease. Synonyms for BCR: Birdshot chorioretinopathy, Birdshot retinochoroiditis, Birdshot retino-choroidopathy, Vitiliginous choroiditis. Orphanet number: ORPHA179 OMIM: 605808.

Involvement of B cells in non-infectious uveitis

Non-infectious uveitis-or intraocular inflammatory disease-causes substantial visual morbidity and reduced quality of life amongst affected individuals. To date, research of pathogenic mechanisms has largely been focused on processes involving T lymphocyte and/or myeloid leukocyte populations. Involvement of B lymphocytes has received relatively little attention. In contrast, B-cell pathobiology is a major field within general immunological research, and large clinical trials have showed that treatments targeting B cells are highly effective for multiple systemic inflammatory diseases. B cells, including the terminally differentiated plasma cell that produces antibody, are found in the human eye in different forms of non-infectious uveitis; in some cases, these cells outnumber other leukocyte subsets. Recent case reports and small case series suggest that B-cell blockade may be therapeutic for patients with non-infectious uveitis. As well as secretion of antibody, B cells may promote intraocular inflammation by presentation of antigen to T cells, production of multiple inflammatory cytokines and support of T-cell survival. B cells may also perform various immunomodulatory activities within the eye. This translational review summarizes the evidence for B-cell involvement in non-infectious uveitis, and considers the potential contributions of B cells to the development and control of the disease. Manipulations of B cells and/or their products are promising new approaches to the treatment of non-infectious uveitis.

HLA-A29-POSITIVE BIRDSHOT CHORIORETINOPATHY IN AN AFRICAN AMERICAN PATIENT

PURPOSE

To report the first documented case of HLA-A29-positive birdshot chorioretinopathy in an African American patient.

METHODS

A 51-year-old African American woman presented with a 10-year history of photopsia, progressive decrease in visual acuity, metamorphopsia, and new nyctalopia. Both fundi showed evidence of periphlebitis, arterial attenuation, macular edema, and diffuse chorioretinal atrophy.

RESULTS

Fluorescein angiography revealed diffuse vascular leakage, and indocyanine green showed evenly distributed and symmetrical hypofluorescent spots, which were difficult to appreciate on fundoscopy. Workup revealed a positive HLA-A29 and was negative for sarcoid, tuberculosis, and syphilis.

CONCLUSION

Birdshot chorioretinopathy overwhelmingly affects non-Hispanic Caucasians, but there have been rare reported cases in other ethnicities including Hispanics and African Americans. This patient's ethnicity may have contributed to the 10-year delay in diagnosis. To our knowledge, this is the first documented HLA-A29 positive case of birdshot chorioretinopathy in an African American. HLA-A29 may be a useful supportive test in cases with classic clinical presentation in non-Caucasian patients to enable the correct diagnose in a timely manner.

OCT and Fundus Autofluorescence Enhances Visualization of White Dot Syndromes

PURPOSE

White dot syndromes (WDS) are a group of inflammatory conditions characterized by white lesions at the retina and choroid level. Detection and monitoring of these syndromes are currently hampered by the subtlety of these lesions, making them difficult to image using traditional clinical techniques. New imaging modalities such as optical coherence tomography (OCT) and fundus autofluorescence (FAF) offer new opportunities for clinicians to noninvasively image WDS.

METHODS

A literature search was performed using a variety of WDS as the search terms. All articles from January 2004 to May 2014 were analyzed for clinical information regarding imaging of the diseases using OCT or FAF.

RESULTS

Current descriptions of OCT and FAF imaging of WDS are fragmented across case reports and small-scale studies. Assessing clinical presentation of WDS using OCT and FAF, however, is useful as the retinal layers affected in these syndromes are well characterized by these technologies. Furthermore, the new information revealed by OCT and FAF is helpful to elucidate the underlying mechanisms of these diseases in combination with known clinical and angiographic findings.

CONCLUSIONS

This review collates current literature and provides a succinct overview of the clinical presentation of WDS using OCT and FAF.

Immunotherapeutic strategies in autoimmune uveitis

Autoimmune uveitis is an organ-specific disorder characterized by irreversible lesions to the eye that predominantly affect people in their most productive years and is among the leading causes of visual deficit and blindness. Currently available therapies are effective in the treatment of a wide spectrum of uveitis, but are often associated with severe side effects. Here, we review ongoing research with promising immunomodulatory therapeutic strategies, describing their specific features, interactions and the responses triggered by the targeted immune molecules that aim to minimize clinical complications and the likelihood of disease relapse. We first review the main features of the disease, diagnostic tools, and traditional forms of therapy, as well as the animal models predominantly used to understand the pathogenesis and test the novel intervention approaches aiming to control the acute immune and inflammatory responses and to dampen chronic responses. Both exploratory research and clinical trials have targeted either the blockade of effector pathways or of their companion co-stimulatory molecules. Examples of targets are T cell receptors (CD3), their co-stimulatory receptors (CD28, CTLA-4) and corresponding ligands (B7-1 and B7-2, also known as CD80 and CD86), and cytokines like IL-2 and their receptors. Here, we summarize the available evidence on effectiveness of these treatments in human and experimental uveitis and highlight a novel CD28 antagonist monovalent Fab′ antibody, FR104, which has shown preclinical efficacy suppressing effector T cells while enhancing regulatory T cell function and immune tolerance in a humanized graft-versus-host disease (GVHD) mice model and is currently being tested in a mouse autoimmune uveitis model with encouraging results.

Birdshot uveitis: current and emerging treatment options

Birdshot chorioretinopathy is a relatively uncommon subtype of idiopathic posterior uveitis with distinct clinical characteristics and a strong genetic association with the Human Leukocyte Antigen (HLA)-A29 allele. The diagnosis remains clinical and is based on the presence of typical clinical features, including multiple, distinctive, hypopigmented choroidal lesions throughout the fundus. The long-term visual prognosis of this disorder, however, remains guarded – central visual acuity can be preserved until late in the disease and it is not uncommon for patients to receive inadequate immunosuppressive treatment, leading to a poor long-term outcome in which peripheral retinal damage eventually leads to visual deterioration. Birdshot chorioretinopathy has proven a particularly attractive area of study within the field of uveitis, as it is a relatively easily defined disease with an associated human leukocyte antigen haplotype. Despite this, however, the immune mechanisms involved in its pathogenesis remain unclear, and some patients continue to lose retinal function despite therapy with corticosteroids and conventional immunosuppressive agents. Laboratory research continues to investigate the underlying mechanisms of disease, and clinical research is now being driven to improve the phenotyping and monitoring of this condition as, in the era of so-called personalized medicine, it is becoming increasingly important to identify patients at risk of visual loss early so that they can be treated more aggressively with targeted therapies such as the newer biological agents. This approach requires the formation of collaborative groups, as the relative rarity of the condition makes it difficult for one center to accumulate enough patients for worthwhile studies. Nevertheless, results obtained with newer therapies, such as biological agents directed against particular cytokines or cell-surface receptors, demonstrate ever improving control of the inflammation in refractory cases, providing hope that the outlook for visual function in this condition can only improve.

Variation and linkage disequilibrium between a structurally polymorphic Alu located near the OR12D2 gene of the extended major histocompatibility complex class I region and HLA-A alleles

We investigated the genetic structure and population frequency of an Alu repeat dimorphism (absence or presence) located near the OR12D2 gene within the olfactory receptor gene region telomeric of the alpha HLA class I region (HLA-J, -A, -G, -F). The structurally polymorphic Alu insertion (POALIN) locus rs33972478 that we designated as AluOR and its allele and haplotype frequencies and association with HLA-A and six other structurally polymorphic retroelements (3 Alu, 2 SVA and an HERVK9) were determined in 100 Japanese, 174 Caucasians and 100 African American DNA samples. The AluOR insertion varied in population frequency between 14.4% and 31.5% with significant differences between the Japanese and Caucasians, but not between the Caucasian and African Americans. Although AluOR is located 600 kb from the HLA-A gene, there was a significant linkage disequilibrium between the two loci and a high percentage association of the AluOR insertion with HLA-A29 (79%) in Caucasians and HLA-A31 (69.4%) in Japanese. Inferred haplotypes among three-locus to eight-locus haplotype structures showed maximum differences between the populations with the eight-locus haplotypes. The most frequent multilocus haplotype shared between the populations was the HLA-A2 allele in combination with the AluHG insertion. The AluOR whether investigated alone or together with the HLA class I alleles and other dimorphic retroelements is an informative ancestral marker for the identification of lineages and variations within the same and/or different populations and for examining the linkage and crossing-over between the HLA and OR genomic regions in the extended MHC.

Interleukin 21, interleukin 23, and transforming growth factor β1 in HLA-A29-associated birdshot retinochoroidopathy

PURPOSE

To determine the peripheral levels of 20 immune mediators in serum samples from patients with birdshot retinochoroidopathy (BSRC).

DESIGN

Single-center prospective case-control study.

METHODS

The serum of 17 BSRC patients during different phases of disease activity and therapy were analyzed with a quantitative multiplex sandwich enzyme-linked immunosorbent assay-based microarray to determine the levels of 20 immune mediators (T cell and proinflammatory). The serum of 12 healthy volunteers was used as controls.

RESULTS

Serum levels of interleukin (IL)-21 (P = .0005), IL-23 (P = .0005), and transforming growth factor (TGF)-β1 (P = .0011) were elevated in BSRC patients with active disease naïve to systemic therapy compared with that of controls. There was no significant difference in the serum levels of immune mediators between controls and BSRC patients who had a current or past history of IMT or who were in remission. The levels of IL-21, IL-23, and TGF-β1 were positively correlated (IL-23/IL-21, r = 0.91; TGF-β1/IL-21, r = 0.97; TGF-β1/IL-23, r = 0.87; for all, P < .0001).

CONCLUSIONS

BSRC patients with active disease naïve to systemic therapy have elevated serum levels of 3 key immune mediators known to promote T helper 17 (Th17) cells in autoimmune disease. Our results suggest that IL-21, IL-23, and TGF-β1 may play an important role in the development of site-specific Th17 cell-mediated inflammation in BSRC, which underscore the importance of systemic therapy and offer new insights into the potential of targeted treatments.

Uveitis in mouse and man

Uveitis is underappreciated as a sight-threatening cause of blindness. There are two broad causative classes of uveitis: infectious and non-infectious. Non-infectious uveitis is considered a prototypical autoimmune disorder based mainly on data from experimental models in the mouse. Several different experimental models exist that reflect the different types of uveitis in man (anterior, intermediate, and posterior uveitis). These models have demonstrated that uveitis is predominantly a Th1/Th17 mediated disease, although innate immune cells play a significant role both in induction of disease and in tissue damage. Most experimental models of uveitis rely on activation of the innate immune system by use of adjuvants that activate a range of pathogen recognition receptors (PRRs). This begs the question of the underlying role of initial and/or persistent infection, including latent infection, in immune-mediated uveitis in which active infection cannot be demonstrated. This further raises the possibility of pathogenic mechanisms such as antigenic cross-reactivity and molecular mimicry. Alternatively, residual/latent antigen from infectious agents may act as "endogenous" adjuvants for induction of immune reactions to damaged/altered self antigen, suggesting a commonality in pathogenesis for both infectious and non-infectious uveitis in man.

Breakdown of immune privilege and spontaneous autoimmunity in mice expressing a transgenic T cell receptor specific for a retinal autoantigen

Despite presence of circulating retina-specific T cells in healthy individuals, ocular immune privilege usually averts development of autoimmune uveitis. To study the breakdown of immune privilege and development of disease, we generated transgenic (Tg) mice that express a T cell receptor (TCR) specific for interphotoreceptor retinoid-binding protein (IRBP), which serves as an autoimmune target in uveitis induced by immunization. Three lines of TCR Tg mice, with different levels of expression of the transgenic R161 TCR and different proportions of IRBP-specific CD4⁺ T cells in their peripheral repertoire, were successfully established. Importantly, two of the lines rapidly developed spontaneous uveitis, reaching 100% incidence by 2 and 3 months of age, respectively, whereas the third appeared "poised" and only developed appreciable disease upon immune perturbation. Susceptibility roughly paralleled expression of the R161 TCR. In all three lines, peripheral CD4⁺ T cells displayed a naïve phenotype, but proliferated in vitro in response to IRBP and elicited uveitis upon adoptive transfer. In contrast, CD4⁺ T cells infiltrating uveitic eyes mostly showed an effector/memory phenotype, and included Th1, Th17 as well as T regulatory cells that appeared to have been peripherally converted from conventional CD4⁺ T cells rather than thymically derived. Thus, R161 mice provide a new and valuable model of spontaneous autoimmune disease that circumvents the limitations of active immunization and adjuvants, and allows to study basic mechanisms involved in maintenance and breakdown of immune homeostasis affecting immunologically privileged sites such as the eye.

HLA-A*01:03, HLA-A*24:02, HLA-B*08:01, HLA-B*27:05, HLA-B*35:01, HLA-B*44:02, and HLA-C*07:01 monochain transgenic/H-2 class I null mice: novel versatile preclinical models of human T cell responses

We have generated a panel of transgenic mice expressing HLA-A*01:03, -A*24:02, -B*08:01, -B*27:05, -B*35:01, -B*44:02, or -C*07:01 as chimeric monochain molecules (i.e., appropriate HLA α1α2 H chain domains fused with a mouse α3 domain and covalently linked to human β2-microglobulin). Whereas surface expression of several transgenes was markedly reduced in recipient mice that coexpressed endogenous H-2 class I molecules, substantial surface expression of all human transgenes was observed in mice lacking H-2 class I molecules. In these HLA monochain transgenic/H-2 class I null mice, we observed a quantitative and qualitative restoration of the peripheral CD8(+) T cell repertoire, which exhibited a TCR diversity comparable with C57BL/6 WT mice. Potent epitope-specific, HLA-restricted, IFN-γ-producing CD8(+) T cell responses were generated against known reference T cell epitopes after either peptide or DNA immunization. HLA-wise, these new transgenic strains encompass a large proportion of individuals from all major human races and ethnicities. In combination with the previously created HLA-A*02:01 and -B*07:02 transgenic mice, the novel HLA transgenic mice described in this report should be a versatile preclinical animal model that will speed up the identification and optimization of HLA-restricted CD8(+) T cell epitopes of potential interest in various autoimmune human diseases and in preclinical evaluation of T cell-based vaccines.

The Rd8 mutation of the Crb1 gene is present in vendor lines of C57BL/6N mice and embryonic stem cells, and confounds ocular induced mutant phenotypes

PURPOSE

We noted an unexpected inheritance pattern of lesions in several strains of gene-manipulated mice with ocular phenotypes. The lesions, which appeared at various stages of backcross to C57BL/6, bore resemblance to the rd8 retinal degeneration phenotype. We set out to examine the prevalence of this mutation in induced mutant mouse lines, vendor C57BL/6 mice and in widely used embryonic stem cells.

METHODS

Ocular lesions were evaluated by fundus examination and histopathology. Detection of the rd8 mutation at the genetic level was performed by PCR with appropriate primers. Data were confirmed by DNA sequencing in selected cases.

RESULTS

Analysis of several induced mutant mouse lines with ocular disease phenotypes revealed that the disease was associated 100% with the presence of the rd8 mutation in the Crb1 gene rather than with the gene of interest. DNA analysis of C57BL/6 mice from common commercial vendors demonstrated the presence of the rd8 mutation in homozygous form in all C57BL/6N substrains, but not in the C57BL/6J substrain. A series of commercially available embryonic stem cells of C57BL/6N origin and C57BL/6N mouse lines used to generate ES cells also contained the rd8 mutation. Affected mice displayed ocular lesions typical of rd8, which were detectable by funduscopy and histopathology as early as 6 weeks of age.

CONCLUSIONS

These findings identify the presence of the rd8 mutation in the C57BL/6N mouse substrain used widely to produce transgenic and knockout mice. The results have grave implications for the vision research community who develop mouse lines to study eye disease, as presence of rd8 can produce significant disease phenotypes unrelated to the gene or genes of interest. It is suggested that researchers screen for rd8 if their mouse lines were generated on the C57BL/6N background, bear resemblance to the rd8 phenotype, or are of indeterminate origin.

Rodent models of experimental autoimmune uveitis

The model of experimental autoimmune uveitis (EAU) in mice and in rats is described. EAU targets immunologically privileged retinal antigens and serves as a model of autoimmune uveitis in humans as well as a model for autoimmunity in a more general sense. EAU is a well-characterized, robust, and reproducible model that is easily followed and quantitated. It is inducible with synthetic peptides derived from retinal autoantigens in commonly available strains of rats and mice. The ability to induce EAU in various gene-manipulated, including HLA-transgenic, mouse strains makes the EAU model suitable for the study of basic mechanisms as well as in clinically relevant interventions.

Efficacy of low-dose methotrexate treatment in birdshot chorioretinopathy

PURPOSE

To ascertain the effect of treatment with methotrexate (MTX) on the visual prognosis of birdshot chorioretinopathy (BSCR).

METHODS

Retrospective case series of 76 consecutive patients with HLA-A29-positive BSCR, of whom 46 were followed for at least 5 years and 18 for longer than 10 years. A review of the medical records of 76 patients with BSCR. Treatment regimens were subdivided into the following groups: 1) No systemic immunomodulatory treatment; 2) Treatment with systemic corticosteroids; and 3) Treatments which comprised MTX. First, we calculated eye-years for the different therapeutic regimens and second, we subdivided the patients according to their initial treatment regimen and assessed visual outcomes.

RESULTS

Mean visual acuity increased over time in the MTX-treated patients; remained unchanged in patients on systemic corticosteroids and decreased in the patients without systemic treatment (yearly change in LogMar -0.020, -0.034 and 0.028 with P = 0.034, P = 0.71 and P = 0.006 respectively). In the group treated initially with MTX, VA gradually increased in contrast to the remaining groups of patients (P = 0.003).

CONCLUSION

In this series, treatment comprising MTX showed better visual outcomes than the untreated patients and corticosteroid-based treatment regimens.

Genetics in ocular inflammation--basic principles

The ability to identify individuals at risk of ocular disease, or to determine the potential severity of disease or response to therapy is the current focus of much research. These studies are being led by genetic analysis of individuals to determine associations with alterations in gens that may explain manifestations of particular diseases. In this review we consider the basic principles behind genetic studies in general and of ocular disease in particular. We address the methodologies being utilised, and the results derived so far. The potential and pitfalls of such studies are relevant to the concept of personalised medicine and better defined clinical trials.

A look at autoimmunity and inflammation in the eye

Autoimmune and inflammatory uveitis are a group of potentially blinding intraocular inflammatory diseases that arise without a known infectious trigger and are often associated with immunological responses to unique retinal proteins. In the United States, about 10% of the cases of severe visual handicap are attributed to this group of disorders. As I discuss here, experimental models of ocular autoimmunity targeting retinal proteins have brought about a better understanding of the basic immunological mechanisms involved in the pathogenesis of uveitis and are serving as templates for the development of novel therapies.

Clinical features, treatment methods, and evolution of birdshot chorioretinopathy in 5 different families

PURPOSE

To report familial cases of birdshot chorioretinopathy (BSCR).

DESIGN

Retrospective, observational case series.

METHODS

Five families with 2 members in each (10 patients) with BSCR were included in this case series from a cohort of 225 patients followed up for BSCR. A review of medical and angiographic records of familial cases of BSCR was performed. We described and compared in each family the histocompatibility leukocyte antigen (HLA) typing, age at onset, ethnic group, clinical features, fluorescein and indocyanine green angiography results, evolution of disease, and treatment used with efficiency.

RESULTS

HLA-A29 and HLA-B44 results were positive in 100% of patients tested. Mean age at onset was 46.5 years. All patients were White. Corticosteroids were required in 7 patients, and 3 patients had no treatment because of mild or moderate lesions. Cyclosporine A was administered in 2 patients from the same family. Period of follow-up ranged from 1 to 32 years (median, 7 years).

CONCLUSIONS

Familial forms of BSCR remain rare and do not justify systematic examination in relatives of patients with BSCR.

Genetics of birdshot chorioretinopathy

Birdshot chorioretinopathy is a bilateral, posterior uveitis that affects primarily Caucasians. Although the genetic basis of disease is not completely understood, certain factors are known, such as the strong association with human leukocyte antigen (HLA)-A29. However, given the prevalence of the HLA-A29 allele in the general population, if it were the only factor required for disease, many more people would have birdshot chorioretinopathy. It has been suggested that some environmental factor may trigger this disease entity in those who are genetically predisposed based on inheritance of the HLA-A29 allele.

Birdshot chorioretinopathy

PURPOSE OF REVIEW

Birdshot chorioretinopathy is the disease with the strongest link to a human leukocyte antigen class I allele. Current research aims at understanding its immunogenetic mechanisms, focusing on the A29 allele, its subtypes, and on other loci of the human leukocyte antigen region. Research criteria can be applied to define birdshot chorioretinopathy. Its heterogeneous presentations and its multiple consequences on visual function are being delineated.

RECENT FINDINGS

HLA-A*2902 is the most frequent subtype in Caucasians and in patients with birdshot chorioretinopathy. The condition has also been observed, however, in a few HLA-A*2901 Caucasian patients, but remains absent or extremely rare in Asia where HLA-A*2901 is the most prevalent subtype. Birdshot chorioretinopathy affects visual acuity, color vision, contrast sensitivity or visual field and pigmentation of birdshot spots could be a marker of disease severity. Electroretinography has been used to monitor the course of the disease; abnormalities may be due to altered outer retinal function or to inner retinal dysfunction. Various therapeutic regimens have been tested and most studies confirm that corticosteroids alone are not a sustainable treatment for patients with birdshot chorioretinopathy.

SUMMARY

Progress has been made in understanding the spectrum of manifestations of birdshot chorioretinopathy. The disease remains of unknown cause and many decisions regarding the management of patients are still empirical.

HLA and eye disease: a synopsis

Human leukocyte antigen (HLA) gene products have been implicated in the pathogenesis of an increasing number of eye diseases, mainly inflammatory in nature. This perspective reviews the current hypotheses for why HLA polymorphisms are associated with specific eye diseases. Statistical problems in studies involving HLA associations are discussed, and possible solutions outlined. The relevance of HLA testing in routine ophthalmic practice, its practical and cost implications is also assessed.

Birdshot Chorioretinopathy

Birdshot chorioretinopathy is a well-known, yet poorly understood, form of posterior uveitis, characterized by multiple, distinctive, hypopigmented choroidal lesions, and strongly associated with human leukocyte antigen (HLA)-A29. We reviewed all English language publications regarding birdshot chorioretinopathy and performed analyses of combined patient data taken from these articles. The mean age at presentation was 53 years, with a slight female predominance (54.1%). At least 95.7% of reported patients have been HLA-A29-positive. Blurring of vision and floaters are the most prevalent presenting complaints, even in patients with visual acuity of 20/20 or better in both eyes. Birdshot chorioretinopathy is a slowly progressive disease with profound dysfunction of vision that may not be reflected in Snellen visual acuity. Two or more lines of Snellen visual acuity were lost in approximately 20% of eyes over a median follow-up of 3.5 years; macular edema was the most common cause of reduced visual acuity. Overall, patients had a slow decline in visual acuity, despite the fact that nearly all were treated with anti-inflammatory therapies. Final visual acuity in the better eye was 20/40 or better in 75.1% of patients and 20/200 or worse in 9.8% of patients. Oral corticosteroids and cyclosporine were the most commonly used medications. Using a regression model, patients in the literature that have been treated with cyclosporine alone had better final visual acuity than patients treated with oral corticosteroids alone. Further study is needed to determine the optimal methods for treating and monitoring patients with birdshot chorioretinopathy.

Self-peptide/MHC and TCR antagonism: physiological role and therapeutic potential

TCR antagonists are peptides that bind MHC molecules and can specifically inhibit T cell activation induced by antigens. Studying TCR antagonism has taken an important place in immunology for both theoretical and practical reasons. Deciphering the mechanism(s) of action of TCR antagonists can yield important information about interactions of the TCR with ligands, T cell development, and TCR signaling. Moreover, microorganisms may employ TCR antagonism to elude the attention of the immune system. Finally, specificity of inhibition makes TCR antagonists an ideal tool to seek antigen-specific immunomodulation. Present state of knowledge on these topics is reviewed.

Electrophysiological characterisation and monitoring in the management of birdshot chorioretinopathy

AIMS

To characterise patients with birdshot chorioretinopathy (BCR) clinically and electrophysiologically in order to monitor changes in retinal function before and after treatment with corticosteroids and/or immunosuppression.

METHODS

18 patients with BCR were characterised clinically and electrophysiologically. Serial studies were performed on 14 patients in order to monitor changes in retinal function before and after treatment with corticosteroids and/or immunosuppression.

RESULTS

Most patients presented with characteristic subretinal pale spots, were HLA-A29 positive, and had diverse signs of ocular inflammation. Various electrophysiological abnormalities were present. Moderately severe bilateral pattern electroretinogram (PERG) abnormalities at presentation were common, reflecting macular dysfunction. Cone mediated 30 Hz flicker electroretinograms (ERGs) were consistently delayed before treatment, and were the most sensitive parameter of retinal dysfunction. Scotopic maximal ERG responses were abnormal in 13 patients; 10 had an electronegative maximal ERG or a reduced b:a ratio in one or both eyes. Single flash photopic ERGs were less often and less severely affected. Photopic ON and OFF ERG responses often revealed predominant ON response b-wave abnormalities with relative OFF response preservation. ERGs improved in treated cases, sometimes preceding clinical signs of recovery. Pattern ERG improvements occurred, possibly reflecting the resolution of macular oedema.

CONCLUSIONS

The ERG data confirm that BCR frequently affects inner retinal function of cone and rod systems. Clinical features were not reliable indicators of functional deterioration or recovery. Objective electrophysiological assessment of retinal function demonstrated improvement following treatment and provides a reliable method of monitoring treatment efficacy, enabling management decisions to be taken with greater confidence and allowing early initiation or modification of treatment.

Dual, HLA-B27 subtype-dependent conformation of a self-peptide

The products of the human leukocyte antigen subtypes HLA-B*2705 and HLA-B*2709 differ only in residue 116 (Asp vs. His) within the peptide binding groove but are differentially associated with the autoimmune disease ankylosing spondylitis (AS); HLA-B*2705 occurs in AS-patients, whereas HLA-B*2709 does not. The subtypes also generate differential T cell repertoires as exemplified by distinct T cell responses against the self-peptide pVIPR (RRKWRRWHL). The crystal structures described here show that pVIPR binds in an unprecedented dual conformation only to HLA-B*2705 molecules. In one binding mode, peptide pArg5 forms a salt bridge to Asp116, connected with drastically different interactions between peptide and heavy chain, contrasting with the second, conventional conformation, which is exclusively found in the case of B*2709. These subtype-dependent differences in pVIPR binding link the emergence of dissimilar T cell repertoires in individuals with HLA-B*2705 or HLA-B*2709 to the buried Asp116/His116 polymorphism and provide novel insights into peptide presentation by major histocompatibility antigens.

A humanized model of experimental autoimmune uveitis in HLA class II transgenic mice

Experimental autoimmune uveitis (EAU) is a disease of the neural retina induced by immunization with retinal antigens, such as interphotoreceptor retinoid-binding protein (IRBP) and arrestin (retinal soluble antigen, S-Ag). EAU serves as a model for human autoimmune uveitic diseases associated with major histocompatibility complex (HLA) genes, in which patients exhibit immunological responses to retinal antigens. Here we report the development of a humanized EAU model in HLA transgenic (TG) mice. HLA-DR3, -DR4, -DQ6, and -DQ8 TG mice were susceptible to IRBP-induced EAU. Importantly, HLA-DR3 TG mice developed severe EAU with S-Ag, to which wild-type mice are highly resistant. Lymphocyte proliferation was blocked by anti-HLA antibodies, confirming that antigen is functionally presented by the human MHC molecules. Disease could be transferred by immune cells with a Th1-like cytokine profile. Antigen-specific T cell repertoire, as manifested by responses to overlapping peptides derived from S-Ag or IRBP, differed from that of wild-type mice. Interestingly, DR3 TG mice, but not wild-type mice, recognized an immunodominant S-Ag epitope between residues 291 and 310 that overlaps with a region of S-Ag recognized by uveitis patients. Thus, EAU in HLA TG mice offers a new model of uveitis that should represent human disease more faithfully than currently existing models.

Could TCR antagonism explain associations between MHC genes and disease?

Alleles of major histocompatibility complex (MHC) loci are associated with certain types of diseases, including those of infectious and autoimmune origin. MHC products can promote susceptibility or resistance to disease by stimulating or inhibiting immune responses. Recent evidence suggests that MHC-associated peptides derived from self-proteins can act as antagonists of T-cell activation, thereby inhibiting immune responses to antigens. We suggest that self-peptide-promoted antagonism might explain some associations between MHC alleles and particular chronic diseases.

A 320-kilobase artificial chromosome encoding the human HLA DR3-DQ2 MHC haplotype confers HLA restriction in transgenic mice

MHC class II haplotypes control the specificity of Th immune responses and susceptibility to many autoimmune diseases. Understanding the role of HLA class II haplotypes in immunity is hampered by the lack of animal models expressing these genes as authentic cis-haplotypes. In this study we describe transgenic expression of the autoimmune prone HLA DR3-DQ2 haplotype from a yeast artificial chromosome (YAC) containing an intact similar320-kb region from HLA DRA to DQB2. In YAC-transgenic mice HLA DR and DQ gene products were expressed on B cells, macrophages, and dendritic cells, but not on T cells indicating cell-specific regulation. Positive selection of the CD4 compartment by human class II molecules was 67% efficient in YAC-homozygous mice lacking endogenous class II molecules (Abeta(null/null)) and expressing only murine CD4. A broad range of TCR Vbeta families was used in the peripheral T cell repertoire, which was also purged of Vbeta5-, Vbeta11-, and Vbeta12-bearing T cells by endogenous mouse mammary tumor virus-encoded superantigens. Expression of the HLA DR3-DQ2 haplotype on the Abeta(null/null) background was associated with normal CD8-dependent clearance of virus from influenza-infected mice and development of CD4-dependent protection from otherwise lethal infection with Salmonella typhimurium. HLA DR- and DQ-restricted T cell responses were also elicited following immunization with known T cell determinants presented by these molecules. These findings demonstrate the potential for human MHC class II haplotypes to function efficiently in transgenic mice and should provide valuable tools for developing humanized models of MHC-associated autoimmune diseases.