Kei Morohoshi

Autoimmunity in retinal degeneration: Autoimmune retinopathy and age-related macular degeneration

Autoantibody production is associated with a variety of ocular disorders, including autoimmune retinopathy (AIR) and age-related macular degeneration (AMD). A breakdown of immunologic tolerance (ocular immune privilege), including the blood-retinal barrier, anti-immune and anti-inflammatory proteins, and anterior chamber-associated immune deviation may play important roles in these disorders. Although the exact triggers for ocular autoimmunity are unknown, autoimmune targeting of retinal tissue is clearly associated with and may contribute to the pathogenesis of both AIR and AMD. Autoantibody production has long been associated with AIR, a collection of disorders that includes cancer-associated retinopathy, melanoma-associated retinopathy and non-paraneoplastic autoimmune retinopathy. A growing body of evidence indicates that AMD pathogenesis, too, involves ocular inflammation and autoimmunity. Identification and quantification of autoantibodies produced in patients with AIR and AMD may assist with diagnosis, prognosis, and choice of treatments. Animal models that allow investigation of ocular autoimmunity will also be needed to better understand the disease processes and to develop novel therapies. In this review we discuss ocular immune privilege and potential mechanisms of autoimmunity in the eye. We describe how autoimmunity relates to the pathogenesis of AIR and AMD. We explain how the antigen microarray technique is used to detect autoantibodies in patient serum samples, and discuss how current animal models for AMD can be used to investigate autoimmune pathogenesis. Finally, we outline unanswered questions and exciting areas of future study related to autoimmune retinal degeneration.

Identification of anti-retinal antibodies in patients with age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in industrial counties. Recent findings indicate that the autoimmunity is involved in the pathogenesis of the disease. However, there is no autoantibody biomarker applied in a clinical setting for diagnosis and prognosis of AMD. In order to reveal retinal antigens targeted by serum IgG from AMD patients, mouse retinal tissue proteins were separated by 2-dimensional electrophoresis and the proteins in the immunoblots that were specific for dry and wet AMD patients IgG were identified by LC-MS/MS. Retinol-binding protein 3 and aldolase C (ALDOC) were mainly recognized by IgG form wet AMD patients. Pyruvate kinase M2 (PKM2) was targeted by both dry and wet AMD and level of anti-PKM2 IgG antibody was correlated best with the stage of AMD. Expression of ALDOC and PKM2 was decreased in mouse retina from aging whereas PKM2 deposit on RPE was increased in aged mice. Our data demonstrate that sera of AMD patients contain autoantibodies against retinal proteins and anti-PKM2 IgG serves as a biomarker for diagnosis and prognosis of AMD. Further investigation of the association of anti-retinal antibody level with expression level of antigens in retina will be needed to reveal the disease pathogenesis.

Serum autoantibody biomarkers for age-related macular degeneration and possible regulators of neovascularization

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in industrial counties. Its pathogenesis is at least partially mediated by immunological factors, including a possible autoimmune response. To date, only a few antibodies have been identified in sera from patients with AMD. In order to reveal an autoantibody profile for AMD and identify biomarkers for progression of this disease, we have performed an antigen microarray analysis of serum samples from patients with AMD and healthy controls. Sera from the AMD groups contained high levels of IgG and IgM autoantibodies to some systemic antigens when compared to the normal group. Targeted antigens included cyclic nucleotide phosphodiesterase, phosphatidylserine (PS) and proliferating cell nuclear antigen. The IgG/IgM ratio for antibodies to PS was notably elevated in the AMD group compared to the normal group, and this ratio correlated best with the stage of AMD patients with an anti-PS ratio greater than the cut-off value had a 44-fold risk for advanced AMD with choroidal neovascularization. PS immunoreactivity was also elevated in AMD retina. Moreover, IgG autoantibodies purified from sera of AMD patients induced more tube formation on choroidal-retinal endothelial cells compared to those of healthy donors. Hence, sera from patients with AMD contain specific autoantibodies which may be used as biomarkers for AMD, and the IgG/M ratio for autoantibodies to PS might allow better monitoring of AMD progression.

Macular and retinal dysfunction of unknown origin in adults with normal fundi: evidence for an autoimmune pathophysiology.

Here we report the discovery of and phenotypic characterization of a retinal disorder of unknown origin in adults using clinical, electrophysiological and psychophysical techniques, and to seek the presence of circulating retinal autoantibodies in the sera of these patients. Sixteen patients were identified with progressive bilateral visual loss over a period of months. Ten of the patients were male, and the average age was 55.3 years (range from 43 to 76 years). Known causes such as carcinoma-associated retinopathy, acute zonal occult outer retinopathy and hereditary cone dystrophy appeared unlikely. Investigations included electrophysiology, fundus autofluorescence imaging and psychophysical tests. The sera of these patients were analyzed with indirect immunocytochemistry and Western immunoblot analysis on murine (BALB/c) retinal tissue for the presence of retinal autoantibodies. Bilateral visual loss and photophobia progressed over a period of months to years (average 28.7 months, range 3-67) and subsequently stabilized. No abnormality was observed by biomicroscopy, angiography or autofluorescence imaging. Electrophysiology indicated predominant cone-system dysfunction, either macular or generalized, and post-phototransduction involvement in 9 patients (56%). Photopic and scotopic visual fields and dark adaptation kinetics showed both cone and rod system involvement in all cases. Heterogeneous immunohistochemical staining patterns were seen with the sera of these patients as compared with controls. A majority of the affected patients (9/15) stained with an antinuclear pattern. The retinal autoantibodies from the sera of most patients reacted with the retinal proteins of molecular weight between 34 and 40 kDa. The aetiology of this distinctive retinal disorder therefore appears to be mediated through an autoimmune mechanism.

Role of β‐chemokines in mast cell activation and type I hypersensitivity reactions in the conjunctiva: in vivo and in vitro studies

Summary:  Chemokines have a clearly defined role in mobilizing the recruitment of leukocytes to both healthy and inflamed tissues. This review details work from our and other laboratories, indicating that β‐chemokines may play important roles (i) in driving the terminal differentiation of mast cell precursors in mucosal tissues and (ii) in providing priming or costimulatory signals required for mast cell activation, leading to an antigen‐driven inflammatory response. These data stem from in vivo, ex vivo, and in vitro studies. Data are also presented that suggest that FcɛRI:chemokine receptor cross talk may involve spatiotemporal dynamics that may control the strength and nature of the complex activating signals controlling mast cell effector function.

Glaucomatous-Type Optic Discs in High Myopia

Purpose To assess the prevalence of glaucoma in patients with high myopia defined as myopic refractive error of >-8 diopters or axial length ≥26.5 mm. Methods The hospital-based observational study included 172 patients (336 eyes) with a mean age of 61.9±12.3 years and mean axial length of 30.1±2.3 mm (range: 24.7–39.1mm). Glaucomatous-type optic discs were defined by glaucomatous optic disc appearance. Glaucoma was defined by glaucomatous optic disc appearance and glaucomatous Goldmann visual field defects not corresponding with myopic macular changes. Results Larger disc area (mean: 3.18±1.94 mm2) was associated with longer axial length (P<0.001; standardized correlation coefficient: 0.45). Glaucoma was detected in 94 (28%; 95% Confidence intervals: 23%, 33%) eyes. In multivariate analysis, glaucoma prevalence was 3.2 times higher (P<0.001) in megalodiscs (>3.79 mm2) than in normal-sized discs or small discs (<1.51 mm2) after adjusting for older age. Axial length was not significantly (P = 0.38) associated with glaucoma prevalence in that model. Glaucoma prevalence increased by a factor of 1.39 for each increase in optic disc area by one mm2. Again, axial length was not significantly (P = 0.38) associated with glaucoma prevalence when added to this multivariate model. Conclusion Within highly myopic individuals, glaucoma prevalence increased with larger optic disc size beyond a disc area of 3.8 mm2. Highly myopic megalodiscs as compared to normal sized discs or small discs had a 3.2 times higher risk for glaucomatous optic nerve neuropathy. The increased glaucoma prevalence in axial high myopia was primarily associated with axial myopia associated disc enlargement and not with axial elongation itself.

SIX-YEAR OUTCOMES OF INTRAVITREAL BEVACIZUMAB FOR CHOROIDAL NEOVASCULARIZATION IN PATIENTS WITH PATHOLOGIC MYOPIA.

Purpose: To investigate the 6-year outcome of intravitreal bevacizumab (IVB) to treat eyes with active choroidal neovascularization (CNV) due to pathologic myopia. Methods: Medical records of 36 eyes of 35 consecutive patients with high myopia (refractive error ≥8 D or axial length ≥26.5 mm) and active CNV, who had been treated with IVB and followed for ≥6 years were analyzed. The factors that predicted the best-corrected visual acuity (BCVA) at 6 years after IVB were determined by multiple regression analyses. Results: The mean age of the subjects was 58 years, and the mean axial length was 29 mm. Twenty-one eyes had subfoveal CNV and 15 eyes had nonsubfoveal CNV. During the 6-year follow-up, the mean number of IVB was 1.78. The mean BCVA logMAR (equivalent Snellen visual acuity) was 0.50 (20/63), 0.31 (20/40), 0.39 (20/50), and 0.45 (20/63) at the baseline, and at 2, 4, and 6 years after the IVB. The BCVA was significantly improved at 2 and 4 years compared with baseline values but not at 6 years. Stepwise multiple regression analyses showed that the BVCA at 6 years was significantly correlated with the size of the CNV-related macular atrophy, and the baseline BCVA and CNV size. Conclusion: The significant correlation between the BCVA at 6 years and the size of the macular atrophy indicates that treatments to prevent the development of macular atrophy are important for the long-term visual outcome in eyes with active CNV.

The role of TRB3 in mast cells sensitized with monomeric IgE

Mast cells play a key role in immunoglobulin E (IgE)-associated allergic disorders; however, the cellular effects of sensitization remain poorly understood. Using gene microarrays and the multiplexing ELISA method, we examined the effects of sensitization on RBL-CCR1 cell transcription and chemokine/cytokine secretion. Sensitization most prominently increased transcription of Trb3, the gene for tribbles homolog 3 (TRB3), and also increased the release of most of the cytokines and chemokines tested. Knockdown of TRB3 via RNAi significantly induced the production of tumor necrosis factor-α (TNF-α), interleukin-4 (IL-4), interleukin-6 (IL-6), and the chemokine mast cell protease-1 (MCP-1). TRB3 deficiency also induced IκBα phosphorylation. TRB3 may therefore serve as a negative regulator of pro-inflammatory cytokines and chemokines, controlling the extent of the inflammatory response.

The Role of Histamine in Ocular Allergy

Ocular allergy is a disorder affecting increasing numbers of individuals worldwide. Among the inflammatory mediators that contribute to ocular allergy, histamine is perhaps the best characterized. This monoamine is released by sensitized mast cells upon exposure to allergen and causes symptoms such as redness and tearing. Histamine may also recruit immune cells that can cause long-term damage to ocular surfaces. In this chapter we will discuss the known functions of histamine and histamine receptors in ocular allergy and will describe promising therapies targeting the histamine-signaling pathway.

Polypoidal choroidal vasculopathy in a case with retinitis pigmentosa

There have been no reports describing polypoidal choroidal vasculopathy (PCV) in eyes with retinitis pigmentosa (RP). A 63-year-old woman who had been diagnosed as having RP was referred to us because of sudden onset of blurred vision in her right eye. Funduscopic examination revealed retinal findings typical of RP in both eyes. The macular area of the right fundus showed polypoidal lesions with massive hemorrhages. Fluorescein angiography and indocyanine green angiography showed multiple polypoidal lesions. Optical coherence tomography showed a large hemorrhagic retinal pigment epithelial (RPE) detachment and polypoidal lesions. The PCV subsided after three applications of anti-vascular endothelial growth factor (VEGF) therapy and a single application of photodynamic therapy, but “mottled lesions” with hyper- and hypofluorescence appeared temporal to the macula after disappearance of hemorrhage. We present a case of PCV in an eye with RP. Further studies are necessary to clarify whether anti-VEGF therapies could affect RPE status in eyes with RP.