Uveitis induced in primates by IRBP: humoral and cellular immune responses

Detection of Complement Activators in Immune Attack Eyes After iPS-Derived Retinal Pigment Epithelial Cell Transplantation

Purpose

To determine whether human induced pluripotent stem (iPS) cell-derived retinal pigment epithelial (RPE) cells (iPS-RPE) can express complement factors.

Methods

To confirm expression of complement factors in human iPS-RPE cells, we performed flow cytometry, immunohistochemistry, ELISA, and quantitative RT-PCR for the following: C3, C5, CFB (Factor B), C5b-9 (membrane attack complex [MAC]), CFH (Factor H), CFI (Factor I), CD46, CD55, CD59, clusterin, and vitronectin. We also prepared iPS-RPE cells in the presence of recombinant IFN-γ, recombinant TNF-α, lipopolysaccharide, supernatants of naïve T cells, and T helper 1 (Th1) cells. For the transplantation, after preparation of iPS-RPE cells from cynomolgus monkeys, the iPS-RPE cells (allografts) were transplanted into the subretinal space in monkeys. After surgery, monkeys were euthanized for IHC evaluation of the retinal section and determination of complement factors (C3, C5, CFB, MAC, and C1q), cytokines, and immunoglobulin G (IgG).

Results

Human iPS-RPE cells expressed complement activators and inhibitors. iPS-RPE cells highly expressed complement factors during inflammatory conditions, especially IFN-γ exposure including Th1 cell supernatants. In immune attack eyes after allogeneic iPS-RPE cell transplantation, complement activators such as C3, CFB, C5, and MAC were detected around the host RPE layer, grafted RPE cells, inflammatory retinal lesions, and transplanted subretinal space. In addition, we observed a large number of C1q and IgG double positive and IFN-γ positive inflammatory cells in the retinal sections.

Conclusions

iPS-derived RPE cells greatly expressed complement factors. Thus, RPE cells might be activated and produce complement factors after exposure to infiltrating inflammatory cells in the eye.

Diagnostic techniques for inflammatory eye disease: past, present and future: a review

Investigations used to aid diagnosis and prognosticate outcomes in ocular inflammatory disorders are based on techniques that have evolved over the last two centuries have dramatically evolved with the advances in molecular biological and imaging technology. Our improved understanding of basic biological processes of infective drives of innate immunity bridging the engagement of adaptive immunity have formed techniques to tailor and develop assays, and deliver targeted treatment options. Diagnostic techniques are paramount to distinguish infective from non-infective intraocular inflammatory disease, particularly in atypical cases. The advances have enabled our ability to multiplex assay small amount of specimen quantities of intraocular samples including aqueous, vitreous or small tissue samples. Nevertheless to achieve diagnosis, techniques often require a range of assays from traditional hypersensitivity reactions and microbe specific immunoglobulin analysis to modern molecular techniques and cytokine analysis. Such approaches capitalise on the advantages of each technique, thereby improving the sensitivity and specificity of diagnoses. This review article highlights the development of laboratory diagnostic techniques for intraocular inflammatory disorders now readily available to assist in accurate identification of infective agents and appropriation of appropriate therapies as well as formulating patient stratification alongside clinical diagnoses into disease groups for clinical trials.

Biologic agents in experimental autoimmune uveitis

Experimental uveitis models were developed in an effort to elucidate the pathogenesis of human uveitis. The therapeutic effects of numerous anti-inflammatory agents including corticosteroids and immunomodulatory agents including biologic response modifiers have been investigated in both experimental and human uveitis. Monoclonal antibodies to tumor necrosis factor alpha and anti-interleukins, among others, demonstrate efficacy and are employed in the treatment of uveitis refractory to conventional immunomodulatory agents.

A hapten generated from an oxidation fragment of docosahexaenoic acid is sufficient to initiate age-related macular degeneration

The protein adduct carboxyethylpyrrole (CEP) is present in age-related macular degeneration (AMD) eye tissue and in the blood of AMD patients at higher levels than found in age-matched non-AMD tissues. Autoantibodies to CEP are also higher in AMD blood samples than in controls. To test the hypothesis that this hapten is causally involved in initiating an inflammatory response in AMD, we immunized C57BL/6J mice with mouse serum albumin (MSA) adducted with CEP. Immunized mice develop antibodies to CEP, fix complement component-3 in Bruch's membrane, accumulate drusen below the retinal pigment epithelium during aging, show decreased a- and b-wave amplitudes in response to light, and develop lesions in the retinal pigment epithelium mimicking geographic atrophy, the blinding end-stage condition characteristic of the dry form of AMD. Inflammatory cells are present in the region of lesions and may be actively involved in the pathology observed. We conclude that early immunization of mice with CEP-adducted MSA sensitizes these animals to the ongoing production of CEP adducts in the outer retina where DHA is abundant and the conditions for oxidative damage are permissive. In response to this early sensitization, the immune system mounts a complement-mediated attack on the cells of the outer retina where CEP adducts are formed. This animal model for AMD is the first that was developed from an inflammatory signal discovered in eye tissue and blood from AMD patients. It provides a novel opportunity for dissecting the early pathology of AMD and the immune response contributing to this disorder. The availability of a mouse with a mechanistically based AMD-like disease that progresses rapidly is highly desirable. Such a model will allow for the efficient preclinical testing of the much-needed therapeutics quickly and inexpensively.

Current opinion of immunotherapy for ocular allergy

PURPOSE OF REVIEW

Allergic conjunctivitis is common and may be the most prominent or the only feature of allergies. Immunotherapy has been used as a primary treatment for allergies since the early 1900s. Currently the use of immunotherapy for allergic rhinoconjunctivitis is well established and has been shown to decrease the development of bronchial hyperreactivity and asthma. However, the role of immunotherapy for primary treatment of allergic conjunctivitis is unclear. We reviewed the studies where immunotherapy was used with particular attention to the affects on ocular allergies.

RECENT FINDINGS

There are many schedules and methods of delivering immunotherapy. Recent studies have started to assess ocular symptoms as one of the parameters to monitor efficacy of therapy. They follow the affects of immunotherapy on conjunctival provocation tests, ocular symptoms, or the use of eye drops. The literature suggests that using the various immunotherapy modalities at different schedules, ocular symptoms improved even when immunotherapy was used on a rush schedule.

SUMMARY

The initiation of immunotherapy for allergic rhinoconjunctivitis has been shown to switch the immune response to T helper 1 and thus avoid the progression of other atopic conditions. Current literature shows that using many allergens with different forms of immunotherapy appear to have a significant improvement in ocular allergy symptoms and this can be achieved rapidly and safely in most patients. Whether using immunotherapy early in allergic conjunctivitis will alter the progression of other atopic conditions remains to be investigated.

Ocular allergy guidelines: a practical treatment algorithm

The treatment of ocular allergy requires a better understanding of the spectrum of clinical disorders involving various components of the immune system, and of interactions at the conjunctival surface. The immune response focuses primarily on the different levels of activity of Th2 lymphocytes and various other immune cells associated with allergic disorders, including mast cells, eosinophils, fibroblasts, and epithelial and endothelial cells. Ocular allergic disorders include seasonal allergic conjunctivitis (SAC), perennial allergic conjunctivitis (PAC), vernal keratoconjunctivitis (VKC), giant papillary conjunctivitis (GPC) and atopic keratoconjunctivitis (AKC), which, through immunopathological and molecular immunological techniques, can all be better appreciated as being part of a larger spectrum of an atopic disease state. In SAC, pathological changes, such as increased mast-cell activation, the presence of migratory inflammatory cells, and early signs of cellular activation at the molecular level, are minimal. In PAC, these changes are more pronounced in line with the increased duration of allergenic stimulation. In more chronic forms of allergic conjunctivitis, such as VKC in children and AKC in adults, the following changes are evident: a persistent state of mast cell, eosinophil and lymphocyte activation; noted switching from connective-tissue to mucosal-type mast cells; increased involvement of corneal pathology; and follicular development and fibrosis. The treatment of acute and more chronic forms of allergic conjunctivitis has focused in the past on symptomatic relief of symptoms, but with a better understanding of the mechanisms involved we can now provide interventional therapeutic strategies and symptomatic relief. Our advances in the basic understanding of these conditions are providing the foundation for guidelines that improve the ocular health of patients with ocular allergies.

The pathogenesis and clinical presentation of macular edema in inflammatory diseases

Cystoid macular edema (CME) is a classical complication of ocular inflammation. This syndrome was already described by Irvine in 1953 but the pathogenesis of this condition remains unclear. Cystoid macular edema can result either from a rupture of the inner or from the outer blood ocular barrier. Clinical CME that is responsible for a low visual acuity must be differentiated from angiographic CME that can be present even without any decrease in visual acuity. Fluid progressively accumulates into the outer plexiform layer of the retina and pools into cystic spaces. Fluid accumulation can now be better seen with optical coherence tomography (OCT). In chronic CME fluid accumulation is associated with thinning of the retina and fibrosis. At this stage irreversible lesions are present and CME does not respond to medical therapies. Inflammatory CME must be differentiated from CME resulting from irreversible vascular damage such as in diabetic CME or due to vein occlusions. Experimental research on cystoid macular edema has been hampered by the lack of animal model: most of laboratory animals have no macula, monkeys appear to be highly resistant to macular edema. Five major causes have been suspected to be at the origin of CME: (1) photic retinopathy, (2) trauma of ocular tissue, (3) secondary irritation of the ciliary body, (4) vitreous traction and (5) pharmaceutically induced CME. Clinical experience has shown that pseudophakic CME usually responds well to local therapy of steroids and non-steroidal antiinflammatory drugs (NSAIDs) and/or in association with systemic acetazolamide. Acetazolamide is increasing fluid resorption through the retinal pigment epithelium. Postoperative CME rarely needs additional posterior subtenon's injections to resolve. But in CME occurring secondary to uveitis additional posterior sub-Tenon's steroid injections or systemic steroids may be necessary to decrease the constant release of inflammatory mediators.

The pathogenesis and clinical presentation of macular edema in inflammatory diseases

Cystoid macular edema (CME) is a classical complication of ocular inflammation. This syndrome was already described by Irvine in 1953 but the pathogenesis of this condition remains unclear. Cystoid macular edema can result either from a rupture of the inner or from the outer blood ocular barrier. Clinical CME that is responsible for a low visual acuity must be differentiated from angiographic CME that can be present even without any decrease in visual acuity. Fluid progressively accumulates into the outer plexiform layer of the retina and pools into cystic spaces. Fluid accumulation can now be better seen with optical coherence tomography (OCT). In chronic CME fluid accumulation is associated with thinning of the retina and fibrosis. At this stage irreversible lesions are present and CME does not respond to medical therapies. Inflammatory CME must be differentiated from CME resulting from irreversible vascular damage such as in diabetic CME or due to vein occlusions. Experimental research on cystoid macular edema has been hampered by the lack of animal model: most of laboratory animals have no macula, monkeys appear to be highly resistant to macular edema. Five major causes have been suspected to be at the origin of CME: (1) photic retinopathy, (2) trauma of ocular tissue, (3) secondary irritation of the ciliary body, (4) vitreous traction and (5) pharmaceutically induced CME. Clinical experience has shown that pseudophakic CME usually responds well to local therapy of steroids and non-steroidal antiinflammatory drugs (NSAIDs) and/or in association with systemic acetazolamide. Acetazolamide is increasing fluid resorption through the retinal pigment epithelium. Postoperative CME rarely needs additional posterior subtenon's injections to resolve. But in CME occurring secondary to uveitis additional posterior sub-Tenon's steroid injections or systemic steroids may be necessary to decrease the constant release of inflammatory mediators.

Uveitis and immune responses in primates immunized with IRBP-derived synthetic peptides

Monkeys immunized with bovine IRBP-derived synthetic peptides R4 (sequence 1158-1180) or R14 (1169-1191) developed EAU which was detected by both clinical and histological examinations. The inflammation localized mainly in the choroid, with only minor changes being noticed in the adjacent retinal tissue. EAU developed in only one of the two monkeys immunized with each of the peptides and the animals with disease also showed higher levels of cellular immunity toward the immunizing peptide than did the monkeys with no disease. The cellular immune responses, measured by the lymphocyte proliferation assay, were specific toward the immunizing peptides, with no cross responsiveness to whole IRBP. This finding suggests that the two uveitogenic peptides were non-immunodominant in the tested monkeys. In contrast, peptide R14 is highly immunodominant in the Lewis rat. Also, the fine specificity of the monkey response to R14 differed from that of the Lewis rat. The possible genetic control of the monkey susceptibility to EAU induction by the peptides is discussed and the unique finding of an autoimmune disease induction by a non-immunodominant peptide is underscored.

Synthetic peptides derived from IRBP induce EAU and EAP in Lewis rats

In an earlier study we isolated three cyanogen bromide cleavage fragments of bovine IRBP that exhibited high levels of immunopathogenicity, producing inflammatory changes in the eyes (EAU) and pineal gland (EAP) of Lewis rats. These fragments have been localized within the IRBP sequence. In order to identify these putative immunopathogenic epitopes of IRBP, nine selected peptide sequences were synthesized and tested for the induction of disease in Lewis rats. Seven of the peptides were found inactive in producing disease while two closely related peptides, designated R4 (23-mer) and R9 (27-mer) were found to reproducibly induce EAU and EAP in immunized rats. No good correlation was found between the immunopathogenicity of the nine tested peptides and their amphipathicity: peptides R4 and R9 were not predicted to form strong amphipathic helices, while peptides selected for their high predicted helical amphipathicity were not immunopathogenic. EAU induced by peptides R4 and R9 was less severe and had a longer onset time than the disease induced by whole IRBP. In addition, the inflammatory changes induced by R4 and R9 in the posterior segment of the eye were less acute than those induced by whole IRBP and included granuloma formation and perivasculitis, features which are not generally seen in rats immunized with whole IRBP. Thus, the changes induced by R4 and R9 more closely resemble those which are characteristically found in human eyes affected by certain uveitic diseases than do changes produced by the intact protein.