Unique epitopes for carbonic anhydrase II autoantibodies related to autoimmune retinopathy and cancer-associated retinopathy

Association of autoantibody levels with different stages of age-related macular degeneration (AMD): Results from the population-based Gutenberg Health Study (GHS)

PURPOSE

Anti-retinal autoantibodies are assumed to be associated with age-related macular degeneration (AMD). To our knowledge, this is the first evaluation of autoantibodies in human sera of participants with different stages of AMD in a large population-based, observational cohort study in Germany.

METHODS

The Gutenberg Health Study (GHS) is a population-based, observational cohort study in Germany, including 15,010 participants aged between 35 and 74. Amongst others, non-mydriatic fundus photography (Visucam PRO NM™, Carl Zeiss Meditec AG, Jena, Germany) was performed. Fundus images of the first 5000 participants were graded based on the Rotterdam Eye Study classification. Sera of participants with AMD (n=541) and sera of age-matched participants without AMD (n=490) were analyzed by antigen-microarrays. Besides descriptive statistics, autoantibody-levels were compared by Mann-Whitney-U test and the associations of level of autoantibodies with AMD were calculated by logistic regression analysis. Likewise, possible associations of the autoantibodies and both clinical and laboratory parameters on AMD subjects were analyzed.

RESULTS

Autoantibodies against transferrin (p<0.001) were significantly downregulated in participants with early AMD and soft, distinct drusen (≥63 μm) or pigmentary abnormalities only compared to Controls. Mitogen-activated protein kinase 3 (p=0.041), glutathione peroxidase 4 (p=0.048), clusterin (p=0.045), lysozyme (p=0.19), protein kinase C substrate 80K-H (p=0.02), heat shock 70 kDa protein 1A (p=0.04) and insulin (p=0.018) show a trend between Control and participants with early AMD and soft, distinct drusen (≥63 μm) or pigmentary abnormalities only.

CONCLUSIONS

This study contributes to a growing knowledge of autoantibodies in association with different AMD stages compared to controls in the context of a large population-based study in Germany. Especially autoantibodies against inflammatory proteins were downregulated in participants with early AMD and soft, distinct drusen (≥63 μm) or pigmentary abnormalities only.

Autoimmune retinopathy: clinical, electrophysiological, and immunological features in nine patients with long-term follow-up

PURPOSE

We aim to report on the clinical, imaging, immunological, and electrophysiological features of patients with autoimmune retinopathy (AIR) with long-term follow-up.

METHODS

Single-center, retrospective study of a consecutive group of AIR patients treated in a tertiary academic medical center.

RESULTS

Included were nine patients with a mean ± SD age at presentation of 65 ± 13 years and a median follow-up of 63 months (range 18-120). Five patients were known to have cancer. Median interval between onset of ocular symptoms and diagnosis of AIR was 36 months. Mean baseline and final LogMAR visual acuity were 0.72 ± 0.9 and 1.1 ± 1.2, respectively (p = 0.17). The most common funduscopic findings included optic atrophy and bone-spicule-like pigmentation. Thinning of the nerve fiber layer was the most frequent optical coherence tomographic abnormality. Electroretinographic (ERG) recordings demonstrated variably reduced cone- and rod-derived amplitudes in the majority of eyes at presentation. The most commonly detected anti-retinal antibody was anti-α-enolase. Treatment included immunomodulatory therapy and plasmapheresis. ERG tests showed stability in 64% of eyes throughout the treatment period.

CONCLUSION

This study highlights the importance of maintaining a high index of suspicion of AIR, particularly in late middle-aged and elderly patients with "unexplained" visual loss, in light of the non-specific posterior segment signs and the inconsistency of the routinely used ancillary tests.

IMMUNE RETINOPATHY ASSOCIATED WITH NIVOLUMAB ADMINISTRATION FOR METASTATIC NON-SMALL CELL LUNG CANCER

PURPOSE

To present a novel case of immune retinopathy associated with nivolumab therapy for non-small cell lung cancer.

METHODS

Retrospective chart review.

RESULTS

A 64-year-old woman presented with photoreceptor injury evidenced by hypoautofluorescent and hyperautofluorescent patches on fundus autofluorescence, loss of the ellipsoid zone on optical coherence tomography, and dysfunction of the rods and cones on electroretinogram. She had a history of Stage IV lung adenocarcinoma, treated with nivolumab, a checkpoint inhibitor. Serology testing was negative for paraneoplastic antibody panel, antirecoverin and antienolase antibodies, but positive for antiretinal antibodies against 30-kDa (carbonic anhydrase II), 35-kDa (GADPH), 38-kDA, 58-kDa (PKM2), and 112-kDa proteins. Cessation of the medication and high-dose oral steroids resulted in resolution of her symptoms and stability of ocular findings.

CONCLUSION

The checkpoint inhibitors, including nivolumab, have significant ocular side effects. All patients receiving nivolumab should undergo a baseline comprehensive eye examination and should be counseled to seek medical attention immediately if visual changes occur.

Utilization of the common functional groups in bioactive molecules: Exploring dual inhibitory potential and computational analysis of keto esters against α-glucosidase and carbonic anhydrase-II enzymes

Diabetes mellitus, a progressive chronic disease, characterized by the abnormal carbohydrate metabolism is associated with severe health complications including long term dysfunction or failure of several organs, cardiovascular and micro-angiopathic problems (neuropathy, nephropathy, retinopathy). Despite the existence of diverse chemical structural libraries of α-glucosidase inhibitors, the limited diabetic treatment due to the adverse side effects such as abdominal distention, flatulence, diarrhoea, and liver damage associated with these inhibitors encourage the medicinal research community to design and develop new and potent inhibitors of α-glucosidase with better pharmacokinetic properties. In this perspective, we demonstrate the successful integration of common functional groups (ketone & ester) in one combined pharmacophore which is favorable for the formation of hydrogen bonds and other weaker interactions with the target proteins. These keto ester derivatives were screened for their α-glucosidase inhibition potential and the in vitro results revealed compound 3c as the highly active inhibitor with an IC₅₀ value of 12.4 ± 0.16 μM compared to acarbose (IC₅₀ = 942 ± 0.74 μM). This inhibition potency was ~76-fold higher than acarbose. Other potent compounds were 3f (IC₅₀ = 28.0 ± 0.28 μM), 3h (IC₅₀ = 33.9 ± 0.09 μM), 3g (IC₅₀ = 34.1 ± 0.04 μM), and 3d (IC₅₀ = 76.5 ± 2.0 μM). In addition, the emerging use of carbonic anhydrase inhibitors for the treatment of diabetic retinopathy (a leading cause of vision loss) prompted us to screen the keto ester derivatives for the inhibition of carbonic anhydrase-II. Compound 3b was found significantly active against carbonic anhydrase-II with an IC₅₀ of 16.5 ± 0.92 μM (acetazolamide; IC₅₀ = 18.2 ± 1.23 μM). Compound 3a also exhibited comparable potency with an IC₅₀ value of 18.9 ± 1.08 μM. Several structure-activity relationship analyses depicted the influence of the substitution pattern on both the aromatic rings. Molecular docking analysis revealed the formation of several H-bonding interactions through the ester carbonyl and the nitro oxygens of 3c with the side chains of His348, Arg212 and His279 in the active pocket of α-glucosidase whereas 3b interacted with His95, -OH of Thr197, Thr198 and WAT462 in the active site of carbonic anhydrase-II. Furthermore, evaluation of ADME properties suggests the safer pharmacological profile of the tested derivatives.

Ocular Paraneoplastic Syndromes

Ocular-involving paraneoplastic syndromes present a wide variety of clinical symptoms. Understanding the background pathophysiological and immunopathological factors can help make a more refined differential diagnosis consistent with the signs and symptoms presented by patients. There are two main pathophysiology arms: (1) autoimmune pathomechanism, which is presented with cancer-associated retinopathy (CAR), melanoma-associated retinopathy (MAR), cancer-associated cone dysfunction (CACD), paraneoplastic vitelliform maculopathy (PVM), and paraneoplastic optic neuritis (PON), and (2) ectopic peptides, which is often caused by tumor-expressed growth factors (T-exGF) and presented with bilateral diffuse uveal melanocytic proliferation (BDUMP). Meticulous systematic analysis of patient symptoms is a critical diagnostic step, complemented by multimodal imaging, which includes fundus photography, optical coherent tomography, fundus autofluorescence, fundus fluorescein angiography, electrophysiological examination, and sometimes fundus indocyjanin green angiography if prescribed by the clinician. Assessment of the presence of circulating antibodies is required for diagnosis. Antiretinal autoantibodies are highly associated with visual paraneoplastic syndromes and may guide diagnosis by classifying clinical manifestations in addition to monitoring treatment.

Current Techniques to Accurately Measure Anti-retinal Autoantibodies

Introduction

Autoimmune retinopathy (AR) is a sight-threating retinal disorder that is mediated by autoantibodies (AAbs) against retinal proteins. The visual paraneoplastic syndromes, including cancer-associated retinopathy (CAR) and melanoma-associated retinopathy (MAR) are mediated by anti-retinal AAbs. A number of immunochemical techniques have been used to detect serum anti-retinal autoantibodies in patients to help with autoimmune diagnosis.

Area covered

We review techniques used for serum autoantibody evaluation in patients with suspected autoimmune retinopathy.

Expert opinion

Detection of serum AAbs have served as the standard diagnostic tool for autoimmune retinopathies and for management of retinal disorders. An identification of anti-retinal autoantibody or multiple autoantibodies can be useful for not only for diagnosis of autoimmune retinopathies but also for management of retinal disorders. We propose that the line-blotting technique used in conjunction with immunohistochemistry are the best and most reliable assays for detection of serum anti-retinal AAb in the context of clinical history and findings. Clinician should recognize that the majority of antigenic targets identified to date in retinal autoimmunity are ubiquitously expressed proteins (e.g. enolase), which may be difficult to reconcile with the specific patterns of retinal damage observed in CAR, MAR, or AR.

Are Anti-Retinal Autoantibodies a Cause or a Consequence of Retinal Degeneration in Autoimmune Retinopathies?

Autoantibodies (AAbs) against various retinal proteins have been associated with vision loss in paraneoplastic and non-paraneoplastic autoimmune retinopathies (AR). There are two major paraneoplastic syndromes associated anti-retinal AAbs, cancer-associated retinopathy (CAR), and melanoma-associated retinopathy. Some people without a cancer diagnosis may present symptoms of CAR and have anti-retinal AAbs. The etiology and pathogenesis of those entities are not fully understood. In this review, we provide evidence for the role of AAbs in retinal death and degeneration. Studies of epitope mapping for anti-recoverin, anti-enolase, and anti-carbonic anhydrase II revealed that although patients' AAbs may recognize the same retinal protein as normal individuals they bind to different molecular domains, which allows distinguishing between normal and diseased AAbs. Given the great diversity of anti-retinal AAbs, it is likely some antibodies have greater pathogenic potential than others. Pathogenic, but not normal antibodies penetrate the target cell, reach their specific antigen, induce apoptosis, and impact retinal pathophysiology. Photoreceptors, dying by apoptosis, induced by other than immunologic mechanisms produce substantial amounts of metabolic debris, which consequently leads to autoimmunization and enhanced permeability of the blood-retinal barrier. AAbs that were made as a part of anti-cancer response are likely to be the cause of retinal degeneration, whereas others, generated against released antigens from damaged retina, contribute to the progression of retinopathy. Altogether, AAbs may trigger retinal degeneration and may also exacerbate the degenerative process in response to the release of sequestered antigens and influence disease progression.

In Vivo Adaptive Optics Ophthalmoscopy Correlated with Histopathologic Results in Cancer-Associated Retinopathy

PURPOSE

To demonstrate the validity of adaptive optics scanning laser ophthalmoscopy (AOSLO) imaging of the retina in human disease based on clinicopathologic correlation in a patient with cancer-associated retinopathy (CAR).

DESIGN

Case report.

PARTICIPANT

Sixty-four-year-old man with CAR.

METHODS

Fundus photography, electroretinography, visual field testing, fundus autofluorescent imaging, spectral-domain OCT scans, AOSLO, and histopathologic analysis were performed.

MAIN OUTCOME MEASURE

Comparison of AOSLO with histopathologic results.

RESULTS

Changes in photoreceptor morphologic features were correlated highly between AOSLO and histopathologic results.

CONCLUSIONS

We present a unique case where a patient with a rare and fatal disease, CAR, underwent AOSLO imaging during the course of the disease, and then shortly thereafter, postmortem histopathologic analysis of the eyes was carried out. This is the first report of use of AOSLO to elucidate further the retinal changes that occur in CAR and the first study to demonstrate correlation of AOSLO with histopathologic results in any human disease.

Impact of Autoantibodies against Glycolytic Enzymes on Pathogenicity of Autoimmune Retinopathy and Other Autoimmune Disorders

Autoantibodies (AAbs) against glycolytic enzymes: aldolase, α-enolase, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase are prevalent in sera of patients with blinding retinal diseases, such as paraneoplastic [cancer-associated retinopathy (CAR)] and non-paraneoplastic autoimmune retinopathies, as well as in many other autoimmune diseases. CAR is a degenerative disease of the retina characterized by sudden vision loss in patients with cancer and serum anti-retinal AAbs. In this review, we discuss the widespread serum presence of anti-glycolytic enzyme AAbs and their significance in autoimmune diseases. There are multiple mechanisms responsible for antibody generation, including the innate anti-microbial response, anti-tumor response, or autoimmune response against released self-antigens from damaged, inflamed tissue. AAbs against enolase, GADPH, and aldolase exist in a single patient in elevated titers, suggesting their participation in pathogenicity. The lack of restriction of AAbs to one disease may be related to an increased expression of glycolytic enzymes in various metabolically active tissues that triggers an autoimmune response and generation of AAbs with the same specificity in several chronic and autoimmune conditions. In CAR, the importance of serum anti-glycolytic enzyme AAbs had been previously dismissed, but the retina may be without pathological consequence until a failure of the blood–retinal barrier function, which would then allow pathogenic AAbs access to their retinal targets, ultimately leading to damaging effects.