Experimental autoimmune uveitis in the athymic nude rat

Biocompatibility of Human Induced Pluripotent Stem Cell-Derived Retinal Progenitor Cell Grafts in Immunocompromised Rats

Loss of photoreceptor cells is a primary feature of inherited retinal degenerative disorders including age-related macular degeneration and retinitis pigmentosa. To restore vision in affected patients, photoreceptor cell replacement will be required. The ideal donor cells for this application are induced pluripotent stem cells (iPSCs) because they can be derived from and transplanted into the same patient obviating the need for long-term immunosuppression. A major limitation for retinal cell replacement therapy is donor cell loss associated with simple methods of cell delivery such as subretinal injections of bolus cell suspensions. Transplantation with supportive biomaterials can help maintain cellular integrity, increase cell survival, and encourage proper cellular alignment and improve integration with the host retina. Using a pig model of retinal degeneration, we recently demonstrated that polycaprolactone (PCL) scaffolds fabricated with two photon lithography have excellent local and systemic tolerability. In this study, we describe rapid photopolymerization-mediated production of PCL-based bioabsorbable scaffolds, a technique for loading iPSC-derived retinal progenitor cells onto the scaffold, methods of surgical transplantation in an immunocompromised rat model and tolerability of the subretinal grafts at 1, 3, and 6 months of follow-up (n = 150). We observed no local or systemic toxicity, nor did we observe any tumor formation despite extensive clinical evaluation, clinical chemistry, hematology, gross tissue examination and detailed histopathology. Demonstrating the local and systemic compatibility of biodegradable scaffolds carrying human iPSC-derived retinal progenitor cells is an important step toward clinical safety trials of this approach in humans.

Overexpressing Kallistatin Aggravates Experimental Autoimmune Uveitis Through Promoting Th17 Differentiation

Kallistatin or kallikrein-binding protein (KBP) has been reported to regulate angiogenesis, inflammation and tumor progression. Autoimmune uveitis is a common, sight-threatening inflammatory intraocular disease. However, the roles of kallistatin in autoimmunity and autoreactive T cells are poorly investigated. Compared to non-uveitis controls, we found that plasma levels of kallistatin were significantly upregulated in patients with Vogt-Koyanagi-Harada (VKH) disease, one of the non-infectious uveitis. Using an experimental autoimmune uveitis (EAU) model induced by human interphotoreceptor retinoid-binding protein peptide 651-670 (hIRBP_651-670), we examined the effects of kallistatin on the pathogenesis of autoimmune diseases. Compared to wild type (WT) mice, kallistatin transgenic (KS) mice developed severe uveitis with dominant Th17 infiltrates in the eye. In addition, the proliferative antigen-specific T cells isolated from KS EAU mice produced increased levels of IL-17A, but not IFN-γ or IL-10 cytokines. Moreover, splenic CD4⁺ T cells from naïve KS mice expressed higher levels of Il17a mRNA compared to WT naïve mice. Under Th17 polarization conditions, KS mice exhibited enhanced differentiation of naïve CD4⁺ T cells into Th17 cells compared to WT controls. Together, our results indicate that kallistatin promotes Th17 differentiation and is a key regulator of aggravating autoinflammation in EAU. Targeting kallistatin might be a potential to treat autoimmune disease.

Comparison of Aqueous and Vitreous Lymphocyte Populations From Two Rat Models of Experimental Uveitis

Purpose

To compare lymphocyte populations present within inflamed eyes in two rat models of autoimmune uveitis.

Methods

Experimental autoimmune uveitis (EAU) and primed mycobacterial uveitis (PMU) were initiated in Lewis rats. Aqueous and vitreous were collected at peak inflammation (PMU at day 2, EAU at day 14). The number of cells in the aqueous and vitreous was determined and compared for each eye and between the two models. Intraocular CD-19⁺ B cells, CD3⁺ T cells, and CD4⁺ or CD8⁺ T-cell subpopulations were identified by flow cytometry and compared between EAU and PMU.

Results

The median number of cells/mL collected from PMU aqueous (7.98 × 10⁷ cells/mL), was not significantly different from the number of cells collected from EAU aqueous (1.61 × 10⁷ cells/mL, P = 0.94). EAU aqueous contains a significantly larger mononuclear population (median 61%, interquartile range [IQR] 44%–67%) than PMU (median 9%, IQR 8%–10% [P < 0.0001]). Within the mononuclear population, EAU and PMU aqueous demonstrate similar proportions of CD3⁺, CD4⁺ T cells. However, EAU has a larger CD3⁺, CD8⁺, T-cell population than PMU, and this population also demonstrates co-expression of CD45R. B cells comprise a significantly larger median percentage of cells in EAU aqueous (median 18%, IQR 15%–20%) compared to PMU (median 13%, IQR 9%–15%, P = 0.006).

Conclusions

Flow cytometry analysis of intraocular lymphocytes from EAU and PMU identifies similarities and differences between the T-cell and B-cell populations present at peak inflammation. Complementary animal models that have well-defined mechanistic differences will improve our ability to test potential new therapies and bring meaningful advances into clinical practice for patients with uveitis.

The Use of Human Mesenchymal Stem Cells as Therapeutic Agents for the in vivo Treatment of Immune-Related Diseases: A Systematic Review

Background: One of the greatest challenges for medicine is to find a safe and effective treatment for immune-related diseases. However, due to the low efficacy of the treatment available and the occurrence of serious adverse effects, many groups are currently searching for alternatives to the traditional therapy. In this regard, the use of human mesenchymal stem cells (hMSCs) represents a great promise for the treatment of a variety of immune-related diseases due to their potent immunomodulatory properties. The main objective of this study is, therefore, to present and summarize, through a systematic review of the literature, in vivo studies in which the efficacy of the administration of hMSCs for the treatment of immune-related diseases was evaluated. Methods: The article search was conducted in PubMed/MEDLINE, Scopus and Web of Science databases. Original research articles assessing the therapeutic potential of hMSCs administration for the in vivo treatment immune-related diseases, published from 1984 to December 2017, were selected and evaluated. Results: A total of 132 manuscripts formed the basis of this systematic review. Most of the studies analyzed reported positive results after hMSCs administration. Clinical effects commonly observed include an increase in the survival rates and a reduction in the severity and incidence of the immune-related diseases studied. In addition, hMSCs administration resulted in an inhibition in the proliferation and activation of CD19⁺ B cells, CD4⁺ Th1 and Th17 cells, CD8⁺ T cells, NK cells, macrophages, monocytes, and neutrophils. The clonal expansion of both Bregs and Tregs cells, however, was stimulated. Administration of hMSCs also resulted in a reduction in the levels of pro-inflammatory cytokines such as IFN-γ, TNF-α, IL-1, IL-2, IL-12, and IL-17 and in an increase in the levels of immunoregulatory cytokines such as IL-4, IL-10, and IL-13. Conclusions: The results obtained in this study open new avenues for the treatment of immune-related diseases through the administration of hMSCs and emphasize the importance of the conduction of further studies in this area.

Immunological homeostasis of the eye

Uveitis is a sight-threatening disease caused by autoimmune or infection-related immune responses. Studies in experimental autoimmune uveitis and in human diseases imply that activated CD4(+) T cells, Th1 and Th17 cells, play an effector role in ocular inflammation. The eye has a unique regional immune system to protect vision-related cells and tissues from these effector T cells. The immunological balance between the pathogenic CD4(+) T cells and regional immune system in the eye contributes to the maintenance of ocular homeostasis and good vision. Current studies have demonstrated that ocular parenchymal cells at the inner surface of the blood-ocular barrier, i.e. corneal endothelial (CE) cells, iris pigment epithelial (PE) cells, ciliary body PE cells, and retinal PE cells, contribute to the regional immune system of the eye. Murine ocular resident cells directly suppress activation of bystander T cells and production of inflammatory cytokines. The ocular resident cells possess distinct properties of immunoregulation that are related to disparate anatomical location. CE cells and iris PE cells, which are located at the anterior segment of the eye and face the aqueous humor, suppress activation of T cells via cell-to-cell contact mechanisms, whereas retinal PE cells suppress the activation of T cells via soluble factors. In addition to direct immune suppression, the ocular resident cells have another unique immunosuppressive property, the induction of CD25(+)Foxp3(+) Treg cells that also suppress the activation of bystander T cells. Iris PE cells convert CD8(+) T cells into Treg cells, while retinal PE cells convert CD4(+) T cells greatly and CD8(+) T cells moderately into Treg cells. CE cells also convert both CD4(+) T cells and CD8(+) T cells into Treg cells. The immunomodulation by ocular resident cells is mediated by various soluble or membrane-bound molecules that include TGF-β TSP-1, B7-2 (CD86), CTLA-2α, PD-L1 (B7-H1), galectin 1, pigment epithelial-derived factor PEDF), GIRTL, and retinoic acid. Human retinal PE cells also possess similar immune properties to induce Treg cells. Although there are many issues to be answered, human Treg cells induced by ocular resident cells such as retinal PE cells and related immunosuppressive molecules can be applied as immune therapy for refractive autoimmune uveitis in humans in the future.

Fragile privileges: autoimmunity in brain and eye

Brain and eye tissues are subject to a reduced version of immune surveillance, which has evolved to protect the particularly sensitive tissues from accidental bystander damage created by regular inflammatory responses. Yet, there are autoimmune diseases in both organs. This review discusses the nature of immune reactivity in the healthy eye and brain tissues, and mechanisms that can overcome the protective barriers to create tissue specific disease.

Regional immunity of the eye

This article reviews molecular mechanism of intraocular inflammation in animal models and in humans, and the immunological defence system of the eye with particular attention to ocular pigment epithelium. In experimental autoimmune uveitis (EAU), T lymphocytes, particularly CD4(+) T lymphocytes, play a central role in its immunopathogenic mechanisms. In humans, activated CD4(+) T cells also play a central role in the immunopathogenic mechanisms. This notion is demonstrated in two human diseases: one is Vogt-Koyanagi-Harada disease, and the other is human T-cell leukemia virus type 1 (HTLV-1) uveitis. Activated CD4(+) T cells infiltrating the eye are harmful to vision-related cells and tissues in the eye and cause sight-threatening conditions. However, the eye has regional defence systems to protect itself from these harmful activated T cells. We focus on ocular pigment epithelium (PE) and demonstrate immunoregulatory activity of iris PE and retinal PE. Iris PE suppresses activated CD4(+) T cells by cell-to-cell contact with a crucial role played by B7-2 molecule on iris PE and CTLA4 on T cells. The actual immunosuppressive factor being membrane bound TGF-beta. In contrast, retinal PE suppresses activated CD4(+) T cells by soluble factors, such as soluble TGF-beta and thrombospondin 1. In addition to the direct T-cell suppression by ocular PE, ocular PE has the capacity to promote activated T cells to regulatory T cells and use them as a tool to amplify the immune down regulation in the eye. The molecular mechanisms of generation of T regulatory cells by iris PE and retinal PE is also discussed.

The pathology and pathogenesis of retinal vasculitis

Retinal vasculitis is a rare, but potentially blinding intraocular inflammatory condition with diverse aetiology. Although commonly idiopathic, it has a strong association with systemic inflammatory diseases known to involve other areas of the central nervous system, most notably Behcet's disease, sarcoidosis, systemic lupus erythematosis and multiple sclerosis. This article describes the clinicopathologic features of retinal vasculitis and its visually damaging sequelae, reviewing available human histopathologic studies and work with experimental models to discuss the pathogenesis and immunopathology. Evidence indicates that noninfective retinal vasculitis is an autoimmune condition that may be induced by antecedent infection with microbes cross-reacting with putative autoantigens, influenced by genetic susceptibility of both HLA associations and cytokine polymorphisms. The growing understanding of the cellular mechanisms involved in the effector immune response is already providing a rationale for more specific therapeutic approaches.

Marrow-derived activated macrophages are required during the effector phase of experimental autoimmune uveoretinitis in rats

PURPOSE

Experimental autoimmune uveoretinitis (EAU), an established model for human endogenous (autoimmune) posterior uveitis, is a CD4+ T cell-mediated disease inducible in Lewis rats by intradermal inoculation with retinal antigens. Immunohistochemical studies have previously documented the lymphocyte profiles during various stages of the disease process. The purpose of the present study was to investigate the role of macrophages in EAU.

METHODS

EAU was induced in Lewis rats, and the effect of macrophage depletion, using the drug dichlorodimethylene diphosphonate (Cl2MDP) encapsulated in liposomes and administered intravenously, was assessed based on the clinical and histological profile of the disease.

RESULTS

The results have shown that in control animals macrophages occur early, feature prominently throughout the course of the disease and display considerable heterogeneity: marrow-derived ED1+ cells and ED3+ cells are the major infiltrating cells, with many cells also expressing ED7 and ED8. In contrast, few cells expressed the ED2 antigen during EAU, even though ED2+ "resident" macrophages occur in the normal choroid. Macrophage depletion, using intravenously injected dichloromethylene diphosphonate (Cl2MDP) enclosed in liposomes, caused a delay in the onset and a reduction in the severity of EAU when administered during the "effector" stage of the disease, i.e. 9-11 days after inoculation with retinal antigen. The delay in disease onset was greater when liposomes were mannosylated and was accompanied by a reduction in the overall inflammatory cell infiltrate into the eye and reduced tissue damage. In addition, there was a reduction in the level of expression of MHC Class II antigen and CR3 (ED7) antigen, a marker of macrophage activation, in Cl2MDP-treated animals compared to controls.

CONCLUSION

These results suggest that blood-borne, activated macrophages are major effectors of tissue damage during EAU.

Suppression of actively induced experimental autoimmune uveoretinitis by CD4+ T cells

BACKGROUND

Helper/inducer T cells that exert an inhibitory effect on disease induction have been recently found in many experimental models. In order to clarify the mechanisms of spontaneous remission of experimental autoimmune uveoretinitis (EAU), we investigated the inhibitory effect and the phenotype of the post-recovery suppressor cells.

METHODS

In a series of experiments, we separated spleen cells of rats that had recovered from EAU. Three groups of spleen cells, CD4+ T, CD8+ T and B cells, were each adoptively transferred into naive syngeneic rats before active immunization with retinal soluble antigen (S-Ag) and Freund's complete adjuvant or passive immunization with uveitogenic T cells from donor rats. Inflammation was examined clinically and histologically.

RESULTS

The development of EAU could be significantly prevented by adoptive transfer of CD4+ T cells, whereas CD8+ T cells could not suppress the onset. However, post-recovery CD4+ T cells failed to inhibit EAU induced by passive immunization with uveitogenic T cells.

CONCLUSION

These findings indicate that CD4+ post-recovery (suppressor) T cells may play an important role in the remission of EAU.

Experimental autoimmune uveitis: molecular mimicry and oral tolerance

Intraocular inflammatory disease or uveitis, which affects the uveal tract and the retina of the eyes in human, is the major cause of visual impairment. Experimental autoimmune uveitis (EAU) is a T-cell-mediated autoimmune disease directed against retinal proteins and has been studied in several mammalian species including subhuman primates as a model for human posterior uveitis. Autoimmune responses provoked by molecular mimicry occur when the nonself and host determinants are similar enough to cross-react yet different enough to break immunological tolerance, and is one of the proposed mechanisms for induction of autoimmune diseases. Therapeutic immunomodulatory strategies have been used to induce antigen-specific peripheral immune tolerance in animal models of T-cell-mediated autoimmune diseases by oral administration of autoantigens. Oral tolerance leads to unique mechanisms of tissue and disease-specific immunosuppression, which would circumvent the immunotherapeutic problem of multiple target tissue autoreactivity. Several groups have investigated the effects of delivering autoantigens across gastric mucosal surfaces. This review briefly discusses molecular mimicry and the mechanism of induction of oral tolerance with respect to immunopathogenesis of T-cell-mediated autoimmune disease in general and EAU in particular.

Recruitment of antigen-nonspecific cells plays a pivotal role in the pathogenesis of a T cell-mediated organ-specific autoimmune disease, experimental autoimmune uveoretinitis

Experimental autoimmune uveoretinitis (EAU) is a prototypic T cell-mediated autoimmune disease, whose target tissue is the neural retina, that is used as a model for a number of human blinding ocular diseases of a presumed autoimmune nature. EAU in rats can be induced by adoptive transfer of small numbers of retinal antigen-specific CD4+ T cell lines. Although recruitment mechanisms were assumed to play a role in the immunopathogenesis of uveitis, there is no direct evidence that would permit assessment of the importance of recruited non-antigen-specific T cells in retinal autoimmunity. In the present study, we addressed this question by using congenitally athymic Lewis rats (LEW.rnu/rnu), that are deficient in functional endogenous T cells, but are otherwise syngeneic with the euthymic Lewis rats that develop characteristically severe EAU. The uveitogenic stimulus was delivered in the form of phenotypically and functionally homogeneous pathogenic T cell lines, specific to the major pathogenic epitope of either the intracellular photoreceptor protein, S-Ag, or the extracellular photoreceptor matrix protein, IRBP. Depending on the T cell line used, EAU in athymic rats was either drastically reduced in severity (IRBP), or essentially absent (S-Ag). Susceptibility was restored when the athymic animals were reconstituted with immunocompetent T cells from syngeneic euthymic donors. While the intraocular infiltrate in euthymic rats was predominantly lymphocytic, with smaller numbers of monocyte/macrophages and even fewer neutrophils, the sparse infiltrate in athymics was largely monocytic, and with a relatively high proportion of neutrophils and eosinophils. Reconstituted animals had an intermediate histological picture with respect to the infiltrating cell types and disease severity. Our data are consistent with the interpretation that recruitment of naive T cells constitutes an amplification mechanism that is central to the expression and pathogenesis of uveitis. The extent of dependence on this phenomenon appears to be influenced by the antigenic specificity of the T cell line, and could be connected to the 'accessibility' of the target antigen in vivo.

Characterization of rat LECAM-1 (L-selectin) by the use of monoclonal antibodies and evidence for the presence of soluble LECAM-1 in rat sera

We have characterized the rat LECAM-1 (L-selectin) by the use of newly generated hamster anti-rat LECAM-1 monoclonal antibodies (mAb) (HRL1, HRL2, HRL3, HRL4), with respect to the biochemistry, cellular distribution and function, and developed an ELISA system to detect the soluble form of rat LECAM-1. In the rat, lymphocyte and neutrophil LECAM-1 have apparent molecular masses of 65 and 62 kDa, respectively, and differential glycosylation may account for the molecular heterogeneity. Readily detectable levels of LECAM-1 are expressed on peripheral blood lymphocytes and neutrophils, but not on thymocytes. Lymphocyte LECAM-1 is rapidly shed from the cell surface upon cell activation with PMA, but not with interleukin (IL)-8. In contrast, neutrophil LECAM-1 showed rapid shedding upon stimulation with phorbol 12-myristate 13-acetate (PMA) or IL-8. Concomitantly there is up-regulated expression of Mac-1 in PMA- and IL-8-stimulated neutrophils. Neutrophil rolling in mesenteric venules was significantly inhibited by administration of function-blocking anti-rat LECAM-1 mAb HRL3, but not by non-blocking HRL4, indicating that LECAM-1 plays a significant role in leukocyte rolling. Given that LECAM-1 is rapidly shed from the cell surface, we attempted to develop an ELISA system for detecting LECAM-1 is soluble form, and measured the levels in experimental autoimmune uveitis. The circulating levels of LECAM-1 increased from day 4, which preceded the appearance of clinical signs of uveitis and remained high until uveitis subsided, suggesting that soluble LECAM-1 is potentially a useful parameter to monitor certain types of inflammatory or immune disorders.

Treatment of autoimmune uveoretinitis in the rat with rapamycin, an inhibitor of lymphocyte growth factor signal transduction

Rapamycin (RAPA) is a macrolide antibiotic with unique immunosuppressive properties. RAPA inhibits T-cell function by interfering with IL-2 and IL-4 signal transduction. It does not prevent IL-2 production or IL-2R expression. The efficacy of RAPA in the treatment of autoimmune diseases was evaluated using the experimental autoimmune uveoretinitis (EAU) model. EAU was actively induced in Lewis rats by immunization with S-antigen in Hunter's adjuvant. RAPA and control vehicle were administered by continuous intravenous infusion over a 14 day period by miniosmotic pump. RAPA treatment initiated on the day of immunization or 7 days later was found to efficiently inhibit EAU induction. The minimal effective dose was 0.1 mg/kg/d. EAU inhibition was correlated with reduced number of cells in the immunization site draining lymph nodes, as well as with a shift and lowering of the peak of the lymphocyte proliferative response curve. The anti-S-antigen antibody response was delayed by 3 days under RAPA treatment and the serum levels lowered in a dose dependent manner. An initial body weight loss was observed during the first week of drug administration, but there was a normal weight gain afterward.

A new effective and non-harmful chemical adjuvant for the induction of experimental autoimmune uveoretinitis

The induction of T cell mediated disease models in animals is usually dependent on the use of complete Freund's adjuvant (CFA). In order to avoid the painful side effects of CFA on the animals, we tested the capacity to induce experimental autoimmune uveoretinitis (EAU) with Hunter's adjuvant (HA). This new adjuvant makes use of nonionic copolymer surfactants, and does not cause deleterious effects to animals. We have found that EAU could be efficiently induced in rats with low doses of S-Ag (10 micrograms) in very small quantity of HA (10 microliters). The biologic parameters of EAU induction showed a potent stimulation of lymphocytes proliferation maximal 11 days after immunization, as well as high levels of antibody production.

Effects of a new immunosuppressive agent, FK 506, on the efferent limb of the immune responses

The effects of a novel immunosuppressant, FK 506, on the efferent limb of the immune response were studied in the experimental autoimmune uveoretinitis (EAU) in the rat, using two different treatment schedules. First, rats actively immunized with S-antigen were treated with FK 506 only after the onset of EAU. FK 506 (1 or 3 mg kg-1 day-1) reduced the intensity of EAU as compared to that of non-treated rats. Especially, a daily dose of 3 mg kg-1 completely suppressed further development of EAU. It is, therefore, suggested that FK 506 treatment is effective in suppressing the ongoing process of the immune response, even after the disease has been initiated. Second, FK 506 (0.3 mg kg-1 day-1) was given only to the recipient rats which received IRBP-sensitized lymphocytes. None of FK 506-treated recipients developed EAU, while all control recipients developed the disease approximately 4 days after the cell transfer. The immune responses of FK 506-treated rats in the two experiments were also significantly suppressed. The antibody levels to S-antigen, the antigen-specific proliferative responses of lymphocytes, and even the proliferative responses to Con A were markedly suppressed in the rats in which FK 506 was given only during the efferent limb of the immune response.

Auxiliary production of antibodies to ocular antigens in experimental autoimmune uveoretinitis

In experimental autoimmune uveoretinitis (EAU), there are concurrent autoreactive humoral and cellular immune responses. Many studies have recently focused on T-cell reactivities in EAU, while analysis of autoantibody responses to uveitogenic epitopes has been less well characterized. In this study, a defined 16-mer uveitogenic interphotoreceptor retinoid binding protein (IRBP) peptide, designated #896, was used to induce EAU. Histological analysis of eyes at day 10 demonstrated extensive leukocyte infiltration of the anterior segment, with mononuclear and plasma cells in the posterior segment. The presence of plasma cells suggests local production of antibodies within the eye. ELISA analyses of serum, aqueous, and vitreous from rats with IRBP-induced, severe EAU revealed the presence of antibodies against peptide #896. There was little difference between the serum and intraocular antibody titers, presumably due to breakdown of the blood-ocular barriers. In addition to the anti-#896-IRBP antibodies, there were detectable antibodies reactive against separate and distinct IRBP epitopes, as well as, against epitopes on retinal-S antigen. These results indicate that in #896-peptide-induced severe EAU, humoral immune responses are induced to the primary immunogen and that there is also auxiliary production of autoreactive antibodies against other epitopes present on intraocular antigens. These auxiliary responses may contribute to the immunopathogenesis of severe EAU.

A new method for induction of experimental autoimmune uveoretinitis (EAU) in mice

Experimental autoimmune uveoretinitis (EAU) was induced in two strains of mice by repeated-immunization protocol. SMA mice (H-2 nondefined) and C57BL/6 mice (H-2b) were immunized with S-antigen mixed with Klebsiella 03 lipopolysaccharide (K03 LPS) repeatedly at intervals of 1 to 4 weeks. Following the tertiary immunization, the mice exhibited histopathological changes of EAU as well as significant immune responses to the antigen. The antigen doses required for successful EAU induction were 4 micrograms or more at each immunization time. The histopathology of EAU was characterized by mild infiltration of mononuclear cells in the retina and the choroid, particularly, at the retinal blood vessels and the photoreceptor cell layer. The anterior segment of the eye was not affected by inflammation, and therefore clinical signs of EAU were not detected even under an operating microscope. Since the mouse is a genetically and immunologically well-defined species, this model is useful for study of immunopathogenic mechanisms of EAU.

Effects of FK506, 15-deoxyspergualin, and cyclosporine on experimental autoimmune uveoretinitis in the rat

The effects of two novel immunosuppressants, FK506 and 15-deoxyspergualin (15-DSG), on experimental autoimmune uveoretinitis (EAU) were evaluated in the rat. Rats were immunized with retinal soluble antigen (S-antigen) and treated with FK506 or 15-DSG, and the disease induction as well as the immune responses to the antigen were examined. The results were compared with animals treated with cyclosporine (CsA) which has been widely used to treat refractory uveitis in humans. A dose-response study showed that FK506 suppressed EAU induction at doses 10-30 times lower CsA when given on days 0-14 postimmunization, while 15-DSG suppressed the disease development at doses very similar to CsA. As with CsA, FK506 suppressed EAU induction when given only in the induction phase (days 0-5 postimmunization) or in the effector phase (days 7-12), but at doses much lower than CsA. On the other hand, 15-DSG suppressed EAU only at toxic doses with these schedules. The antigen specific mitotic response of lymphocytes was markedly suppressed by the three agents, while the antigen specific antibodies in sera were suppressed by 15-DSG and FK506 but not by CsA at doses effective in suppressing the disease induction. More significant findings were uniquely prolonged immunosuppressive effects of FK506: EAU induction as well as the immune responses to S-antigen were suppressed long after the cessation of drug treatment.

Experimental autoimmune uveoretinitis: idiotypic regulation and disease suppression

Experimental autoimmune uveoretinitis (EAU), a mostly T-cell dependent disease, was induced in laboratory animals by a single immunization with retinal extract or purified S-antigen in complete Freund's adjuvant. It can be prevented or suppressed by injections of either the autoantigen or monoclonal antibodies against the autoantigen. The suppression of EAU by these antibodies was associated with an anti-idiotypic antibody response. The inhibition of the pathogenic immune response by the antigen or the antibodies could be explained, according to Jerne's hypothesis of immunoregulation, by a disturbance of the network of idiotype and anti-idiotype interactions.

Sequence homology between yeast histone H3 and uveitopathogenic site of S-antigen: lymphocyte cross-reaction and adoptive transfer of the disease

Experimental autoimmune uveitis (EAU) serves as an animal model of ocular inflammation. The disease is caused by the immunization of microgram amounts of a soluble retinal protein, designated S-antigen, in susceptible animal strains, including primates. We induced EAU and experimental autoimmune pinealitis (EAP) in Lewis rats with a small synthetic peptide corresponding to amino acid positions 106-121 in yeast histone H3. This peptide contains five consecutive amino acids identical to a uveitopathogenic site (peptide M) in human S-antigen. Lymph node or mononuclear cells from different species of animals immunized either with histone H3 or with peptide M showed significant cross-reaction as measured by in vitro lymphocyte mitogenesis assay using [3H]thymidine. Also, we adoptively transferred the EAU and EAP in naive rats by immune lymph node cells. These findings support the fact that selected bacterial, viral, or fungal proteins with amino acid sequence homologies to normal retinal proteins are uveitopathogenic and, as such, provide a basis for autoimmune inflammatory diseases.

Histopathologic analysis of experimental autoimmune uveitis attenuated by intracameral injection of S-antigen

Pretreatment of rats and mice with intracameral injections of soluble protein antigens induces Anterior Chamber Associated Immune Deviation, an unusual spectrum of immune reactivities that is dominated by suppression of the efferent limb of the immune response. Pretreatment of Lewis rats with an intracameral injection of S antigen (S Ag) mitigates against the development of clinically detectable experimental autoimmune uveitis if these rats are subsequently injected with a uveitogenic dose of S Ag. In this report, we describe a series of histopathologic studies designed to determine the extent and severity of changes that occur in the eyes of rats pretreated with intracameral S Ag. The results indicate that pretreatment with intracameral injection of S Ag alone or mixed with Complete Freund's Adjuvant significantly inhibited the development of severe uveoretinitis. In the eyes of the majority of rats, the histologic appearance was completely normal, without any evidence of pathologic changes. A minority of rats displayed clinical evidence of uveitis, and their eyes contained histopathologic changes. These changes suggested that a mild form of uveoretinitis had taken place. It is proposed that S Ag-specific suppression of delayed hypersensitivity is induced by the anterior chamber injection of this antigen, and that this suppressor activity accounts for the reduced severity of disease in the eyes of treated rats. The potential physiologic significance of suppression in response to exposure to unique ocular antigens is discussed.

Immune response to intraocular injection of retinal S-antigen in adjuvant

It has been proposed that the introduction of foreign material into the eye at the moment of a penetrating trauma provides an adjuvant effect which, coupled with the release of antigen, might be responsible for sensitizing the immune system to produce a contralateral "sympathetic ophthalmia." We addressed that hypothesis by injecting S-antigen with complete Freund's adjuvant (CFA) into the anterior chamber (AC) of the eye of Lewis rats. The injection of an identical dose of antigen (30 micrograms S-Ag in CFA in a total volume of 10 microliters) via the foodpad (FP) or under the conjunctiva (SC) could induce typical experimental autoimmune uveitis (EAU). By immunizing via the AC route, we could demonstrate a positive sensitization of the immune system, manifested by serum antibody production against S-Ag and by the presence of S-Ag-specific, responsive T-lymphocytes in the spleen. However, immunization via the AC route did not induce contralateral uveitis, and the animals did not produce a DTH skin response when challenged intradermally with S-Ag as they did after FP immunization. In the light of these results, we evaluated the possibility that a DTH suppressive response was elicited by intracameral (IC) injection as seen in anterior chamber-associated immune deviation (ACAID): we tested the effect of splenectomy and cyclophosphamide pretreatment before IC immunization and the effect of secondary footpad immunization as well as T-helper cell transfer after IC immunization. The results given by these approaches argue against the induction of suppressor cells by IC immunization.(ABSTRACT TRUNCATED AT 250 WORDS)

Human S-antigen: characterization of uveitopathogenic sites

Human S-antigen (HSA) is a 50,000 molecular weight photoreceptor cell protein capable of inducing an experimental autoimmune uveitis (EAU) in susceptible animal strains. In order to determine specific sites responsible for its uveitopathogenicity, we synthesized 39 overlapping peptides corresponding to its entire 404 amino acid sequence and tested each peptide for its ability to induce an EAU in Lewis rats. Two synthetic peptides designated peptide HSA 319 (amino acid positions 286 to 305) and peptide HSA 320 (amino acid positions 306 to 325) were uveitopathogenic when used at 50 and 100 micrograms immunizing doses. Smaller peptides corresponding to the amino, mid, and carboxy terminal portions of each peptide further refined each uveitopathogenic site to 12 amino acids. A computerized analysis of the amino acid sequence of S-antigen indicates that these uveitopathogenic sites are complex and may be related to a two-fold symmetry in the molecule. Our present and previous studies provide a basis for the uveitopathogenicity of human and bovine S-antigen in the pathogenesis of EAU as well as the pathogenesis of certain forms of uveitis in humans.

Cyclosporine-induced specific unresponsiveness to retinal soluble antigen in experimental autoimmune uveoretinitis

Cyclosporine (CsA) was previously reported to effectively suppress the induction of experimental autoimmune uveoretinitis (EAU) in rats immunized with S-antigen. The present study provides information concerning the development of specific unresponsiveness in the CsA-treated rats. The majority of Lewis rats immunized with S-antigen and treated with CsA from Day 0 to Day 14 failed to develop EAU when reimmunized with S-antigen on Day 30. In contrast, similarly treated rats were fully susceptible to induction of experimental allergic encephalomyelitis when immunized with myelin basic protein, or even to EAU when immunized with another retinal antigen, interphotoreceptor retinoid-binding protein (IRBP). The possible involvement of suppressor cells in establishing the unresponsiveness state was indicated by experiments both in vitro and in vivo. The enriched fractions of suppressor cells from rats unresponsive to induction of EAU by S-antigen were found to inhibit the specific mitotic response of lymphocytes to S-antigen, but had no effect on the response to IRBP. In vivo, injection of such enriched suppressor cell fractions to naive syngenic rats inhibited or delayed the development of EAU following immunization with S-antigen. It is proposed, therefore, that specific unresponsiveness plays a role in the suppression of EAU by CsA and that the unresponsiveness is mediated in part by specific suppressor cells.

Uveoretinitis in rabbits following immunization with interphotoreceptor retinoid-binding protein

Interphotoreceptor retinoid-binding protein (IRBP) is a glycoprotein found in the interphotoreceptor matrix between the neurosensory retina and the retinal pigment epithelium and is thought to shuttle retinol among cells that border the interphotoreceptor space. Immunization of rabbits with bovine IRBP caused subsequent photoreceptor degeneration, as documented by light- and electron microscopy. Beginning on post-injection day 18, scattered regions had photoreceptor outer segments that were disorganized and shortened or absent. Macrophages were found between the retinal pigment epithelium and neurosensory retina and within choroidal interstitium and blood vessels. Labeling of these cells with a marker specific for monocytic macrophages (RAM11) and absence of labeling with a marker for retinal pigment epithelium (rabbit anti-bovine cellular retinaldehyde-binding protein) suggest that these macrophages were hematogenous in origin. Staining of retinas with fluorescein isothiocyanate (FITC)-conjugated sheep anti-rabbit IgG revealed leakage of rabbit IgG into the interphotoreceptor matrix on and after day 18 in experimental animals but not in controls, suggesting breakdown of the outer blood-retinal barrier. Indirect immunofluorescence with anti-glial fibrillary acidic protein revealed labeling of Müller cells in experimental retinas on and after day 18, but not in control or shorter survival experimental retinas. There were foci of increased cellularity in the choroid on days 18, 26 and 39. From days 26 through 67, the retinal pathology became more widespread. Varying degrees of outer-segment degeneration were present in all parts of the retina and in many areas there was total loss of outer segments and loss of some photoreceptor-cell bodies. The inner retina appeared unaffected in all experimental and control retinas. These results demonstrate that injection of rabbits with bovine IRBP causes retinal photoreceptor degeneration as anti-IRBP titers increase and breakdown of the outer blood-retinal barrier ensues. Further studies will be required to elucidate factor(s) that control accessibility of the neurosensory retina to circulating antibodies against IRBP and other intrinsic retinal proteins.

The effects of pertussis toxin on the induction and transfer of experimental autoimmune uveoretinitis

Experimental autoimmune uveoretinitis (EAU), an intraocular inflammatory disease, is induced in experimental animals by immunization with a retinal specific antigen, S-antigen (S-Ag), emulsified in complete Freund's adjuvant (CFA). The induction of EAU is enhanced by treating S-Ag-immunized animals with Bordetella pertussis. This study examined the effects of a purified component of B. pertussis, pertussis toxin (Ptx), on EAU induction as well as the mode of action of this toxin. Treatment of Lewis rats with Ptx concurrent with S-Ag and CFA enhanced EAU induction as shown by an earlier onset of disease, increased severity of ocular changes, and the reduction of the threshold amount of S-Ag needed for EAU induction. Treatment with Ptx selectively enhanced delayed-type hypersensitivity responses to S-Ag but did not affect specific antibody production. The mode of action of Ptx was analyzed by using the adoptive transfer of EAU by sensitized lymphocytes. Ptx treatment of donor rats enhanced the capacity of lymphocytes to transfer EAU. However, Ptx treatment of recipient rats on the day of cell transfer resulted in a delay in the onset of disease. These results indicate that Ptx enhances the immunopathogenic processes of EAU by enhancing lymphocyte activation and/or increasing their pathogenic activities.

Immunological abnormalities in patients with untreated retinal vasculitis

Peripheral blood immunological features were assessed in 21 patients with clinical and angiographic evidence of retinal vasculitis (RV). Abnormalities of humoral and cellular immunity were frequent in this group of patients. Lymphopenia was the most common immunological abnormality, being present in 76% of patients at presentation (p less than 0.05). Peripheral blood T and B cells were decreased with a normal helper (OKT4) to suppressor (OKT8) T cell ratio in 11 patients tested (five with Behçet's syndrome and six with idiopathic RV). Significantly increased concentrations of serum immune complexes were present in 55% of patients (p less than 0.05). Results of the present study indicate the frequent association of peripheral blood immunological abnormalities in patients with active RV and indicate the possible role of immunological mechanisms in its pathogenesis.

Induction of experimental autoimmune uveoretinitis and pinealitis by IRBP. Comparison to uveoretinitis induced by S-antigen and opsin

Microgram quantities bovine IRBP (interphotoreceptor retinoid binding protein) injected in Freund's complete adjuvant induced severe autoimmune uveoretinitis and pinealitis in Lewis rats. At low doses the onset was accelerated and intensified by co-injection of Hemophilus pertussis bacteria. Wistar, BN and PVG rats were less susceptible, while the eyes of athymic, nude rats did not respond. The disease developed similar to but faster than S-antigen-induced uveoretinitis, while its onset was one day earlier and the reactions were slightly more severe. As distinct from these two types of uveoretinitis, opsin (in much higher doses) caused milder reactions in the anterior segment, while retinitis dominated. In each type of inflammation the photoreceptor cell layer was totally destroyed. All three ocular diseases were inhibited by cyclosporine treatment, which indicates that T cell-dependent mechanisms are essential for the development.

Inhibition of experimental autoimmune uveoretinitis in rats by S-antigen-specific monoclonal antibodies

Mouse monoclonal antibodies (mAb), of either IgG2a or IgG2b isotypes, specific for the retinal S-autoantigen (S-Ag) or a pool of rat anti-S-Ag sera prevented experimental autoimmune uveoretinitis in Lewis rats when injected i.p. at the time of immunization. Control mAb of the same isotypes, irrelevant to S-Ag, had no inhibitory effect. The humoral response to S-Ag, as studied by enzyme-linked immunosorbent assay using a mouse mAb specific for rat kappa chain, was moderately but significantly reduced in suppressed animals. The rapid disappearance of the injected mAb from rat sera, as measured using a rat mAb specific for mouse kappa chain, could be explained by its complexing with either autologous antigen released from the retina at the site of inflammation, or anti-idiotypic antibodies.

Experimental autoimmune uveoretinitis in athymic rats: specific IgE response to retinal S-antigen and disease

Experimental autoimmune uveoretinitis (EAU) is an ocular autoimmune disease induced in rats by immunization with retinal S-antigen. Athymic nude rats (rnu/rnu) have been previously shown to be refractory to EAU induction and antibody production to S-antigen, while heterozygous (rnu/+) are good responders. Increasing the antigen dose and adding pertussis adjuvant produced ocular disease in some nude rats, and antibody response in most of them. Specific IgE antibodies were demonstrated by ELI-SA only in the serum of nude rats presenting the disease. However, most immunized nude rats had evidence of mast cell sensitization to S-antigen (direct degranulation test) and of circulating specific IgE detected by passive sensitization of normal mast cells (indirect degranulation test). This positive response could be explained by an incomplete depletion of the different T lymphocyte subsets.

Cyclosporine therapy for uveitis: long-term followup

Long term followup in 52 uveitis patients treated with Cyclosporine (CsA) is presented here. The patients included in this study all had intermediate or posterior uveitis of noninfectious etiology; and all were considered therapeutic failures to systemic corticosteroids and/or cytotoxic agents. Patients were considered a therapeutic success if the visual acuity in either eye improved two lines or more and/or the vitreal haze improved more than two grading levels. While five patients stopped therapy before the three month interval, 41 of 52 patients or 79% were therapeutic successes at three months after the initiation of CsA as the sole systemic immunosuppressive agent for their disease. Twenty-five of a potential 35 patients (71%) remained on CsA after one year's time, with 63% (22/35) of these individuals receiving the medication considered a therapeutic success. The patients who appeared to respond particularly well to CsA therapy were those with pars planitis, intermediate uveitis of the non-pars planitis type, VKH, and Behcet's disease. In vitro S-antigen (S-Ag) testing did not appear to have a predictive value in determining which patients would be therapeutic successes (improvement in visual acuity), however the S-Ag responder group did appear to have a statistically greater improvement in vitreal haze. Renal toxicity was by far the most common adverse effect, which we have found to be reversible with our approach to therapy. However, adverse reactions required a reduction in CsA dosage in some patients, making it not feasible to maintain therapeutically effective CsA levels. In those patients, low dose prednisone was added to these patients' CsA regimens with generally good results. We did not observe opportunistic infections nor CsA associated neoplasms in our patients. This long term study demonstrates the potential efficacy of CsA in the treatment of severe intra-ocular inflammatory disorders. However, we firmly believe that only in the context of a randomized clinical trial that a definitive evaluation as to the true effectiveness of CsA will be reached.

Longitudinal study of serum antibody responses to bovine retinal S-antigen in endogenous granulomatous uveitis

Twelve patients with granulomatous uveitis were followed up longitudinally for as long as 20 months after their initial visit, and multiple serum antibody titres to bovine retinal S-antigen were determined and compared with the clinical activity at the time of each sampling. In those patients who presented with highly active lesions which then resolved during the course of the study without recurrences (7 toxoplasmosis and 1 pars planitis) the antibody titres reached a peak approximately 2 months after the initial visit and declined thereafter. No correlation of serum anti-S titres with clinical activity or predictable pattern of titres could be found in those patients who had recurrences during the course of the study (3 granulomatous iridocyclitis and 1 ocular sarcoidosis).