Osteopontin Aggravates Experimental Autoimmune Uveoretinitis in Mice

Human endogenous uveitis is a common sight-threatening intraocular inflammatory disease and has been studied extensively using a murine model of experimental autoimmune uveoretinitis (EAU). It is possibly mediated by Th1 immune responses. In the present study, we investigated the role of osteopontin (OPN), a protein with pleiotropic functions that contributes to the development of Th1 cell-mediated immunity. Accompanying EAU progression, OPN was elevated in wild-type (WT) mice that had been immunized with human interphotoreceptor retinoid-binding protein (hIRBP) peptide 1-20. OPN-deficient (OPN-/-) mice showed milder EAU progression in clinical and histopathological scores compared with those of WT mice. The T cells from hIRBP-immunized OPN-/- mice exhibited reduced Ag-specific proliferation and proinflammatory cytokine (TNF-alpha and IFN-gamma) production compared with those of WT T cells. When hIRBP-immunized WT mice were administered M5 Ab reacting to SLAYGLR sequence, a cryptic binding site to integrins within OPN, EAU development was significantly ameliorated. T cells from hIRBP-immunized WT mice showed significantly reduced proliferative responses and proinflammatory cytokine production upon stimulation with hIRBP peptide in the presence of M5 Ab in the culture. Our present results demonstrate that OPN may represent a novel therapeutic target to control uveoretinitis.

Limited peripheral T cell anergy predisposes to retinal autoimmunity

Autoimmune uveoretinitis accounts for at least 10% of worldwide blindness, yet it is unclear why tolerance to retinal Ags is so fragile and, particularly, to what extent this might be due to defects in peripheral tolerance. To address this issue, we generated double-transgenic mice expressing hen egg lysozyme, under the retinal interphotoreceptor retinoid-binding promoter, and a hen egg lysozyme-specific CD4(+) TCR transgene. In this manner, we have tracked autoreactive CD4(+) T cells from their development in the thymus to their involvement in uveoretinitis and compared tolerogenic mechanisms induced in a variety of organs to the same self-Ag. Our findings show that central tolerance to retinal and pancreatic Ags is qualitatively similar and equally dependent on the transcriptional regulator protein AIRE. However, the lack of Ag presentation in the eye-draining lymph nodes results in a failure to induce high levels of T cell anergy. Under these circumstances, despite considerable central deletion, low levels of retinal-specific autoreactive CD4(+) T cells can induce severe autoimmune disease. The relative lack of anergy induction by retinal Ags, in contrast to the same Ag in other organs, helps to explain the unique susceptibility of the eye to spontaneous and experimentally induced autoimmune disease.

Treatment of experimental autoimmune uveoretinitis with atorvastatin and lovastatin

Statins, which are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, are approved for cholesterol reduction and are commonly used to treat atherosclerosis and coronary artery disease. Statins may also be potent immunomodulatory agents and may be beneficial in the treatment of autoimmune diseases. In this study, we investigated therapeutic effects of atorvastatin and lovastatin on experimental autoimmune uveoretinitis (EAU). EAU was induced in Lewis rats using bovine S-antigen (S-Ag) peptide. Atorvastatin was suspended in 0.5% aqueous methylcellulose and was administered orally at a dose of 10 mg/kg and at a low-dose of 1 mg/kg. Lovastatin was dissolved in DMSO:PBS (1:1) and was administered by intraperitoneal (i.p.) injection at a dose of 2 mg/kg. Both statin treatments were initiated after the clinical onset once daily for 14 days. The rats were examined every other day for clinical signs of EAU. The histological scores and delayed-type hypersensitivity (DTH) were evaluated on day 28 post-immunization. Morphologic and immunohistochemical examinations were performed with light and confocal microscopy, respectively. Lymphocyte proliferation was measured by [(3)H]thymidine incorporation into antigen-stimulated T cells from inguinal lymph nodes. After 72 h, supernatants were collected and assayed for IFN-gamma by ELISA. Clinical and histological scores of EAU were decreased in both the atorvastatin (10 mg/kg)- and lovastatin (2 mg/kg)-treated groups. The invasion of T cells and macrophages, and Müller cell proliferation, were inhibited in both atorvastatin- and lovastatin-treated groups. DTH was significantly inhibited in both groups, compared with vehicle-treated groups (controls). Lymphocyte proliferation assay demonstrated decreased proliferation in the presence of 25 microg/ml S-Ag peptide in both groups, compared with controls. In the supernatants of lymph node cells stimulated with S-Ag peptide (5 microg/ml), 77 or 87% inhibition of IFN-gamma production was observed in rats treated with atorvastatin or lovastatin, respectively, compared with controls. The current results indicate that atorvastatin administrated orally following the clinical onset has therapeutic effect in EAU as well as lovastatin administrated intraperitoneally. Statins may be useful for treating intraocular inflammation.

[Translational research with experimental autoimmune uveoretinitis (EAU)]

Experimental autoimmune uveoretinitis (EAU) induced by immunization with retinal antigen (Santigen or interphotoreceptor retinoid-binding protein; IRBP) serves as an animal model of human uveoretinitis. As the first stage, we demonstrated the similarities between EAU and ocular inflammation in Behçet's disease by investigating anti-retinal antibodies, leukocyte migration inhibition by retinal antigen, immunogenic antigens, aberrant functions of neutrophils, and dominant Th1 lymphocyte reaction. From these findings, we verified that EAU, which is not associated with the systemic disorders observed in Behçet's disease, is an appropriate model for translational research targeting ocular inflammation. In the second stage, we set 3 therapeutic strategies for uveitis in Behçet's disease to be conducted in the translational research: (1) intraocular administration of an immunosuppressive drug; (2) inhibition of Th1 lymphocytes; and (3) activation of immunoregulatory cells. In strategy 1, our studies indicated that intravitreal injection of 10 microg of tacrolimus (FK 506) was not harmful to the retina and was predominantly effective in suppressing ongoing EAU in rats. In strategy 2, two approaches were adopted to prevent differentiation of Thl cells. One is anti-cytokine antibody therapy using anti-IL-12 monoclonal antibodies(mAb). The other is blockade of co-stimulatory signals, especially the ICOS-B7RP-1 pathway. Administration of anti-IL-12 mAb at the time of IRBP immunization completely inhibited development of EAU, and antagonistic anti B7RP-1 mAb suppressed the severity of EAU even when administered after development of EAU. In strategy 3, adoptive transfer of antigen presenting cells treated with a neuropeptide (vasoactive intestinal peptide or calcitonin gene-related peptide) or CD 4+ CD 25+ regulatory T cells suppressed EAU. We look forward to the day when therapies that are being developed in our translational research using EAU will become available for treating intraocular inflammation in Behçet's disease.

The role of the ICOS/B7RP-1 T cell costimulatory pathway in murine experimental autoimmune uveoretinitis

ICOS/B7RP-1 is a new member of the CD28/B7 family of costimulatory molecules and plays differential roles in autoimmune diseases. In this study, we examined the role of ICOS/B7RP-1 pathway in the pathogenesis of mouse experimental autoimmune uveoretinitis (EAU), an animal model of human autoimmune uveitis. ICOS expression was found on infiltrating CD4+ T cells in the region of the retina in EAU-induced mice. The anti-B7RP-1 monoclonal antibody (mAb)-treated or ICOS-deficient mice showed a substantial reduction of disease scores. Blockade of ICOS/B7RP-1 interaction during the effector phase ameliorated the disease, whereas its blockade during the induction phase exhibited no significant effect. Moreover, administration of anti-B7RP-1 mAb effectively ameliorated the disease induced by adoptive transfer of pathogenic T cells. The anti-B7RP-1 mAb treatment inhibited the expansion and/or effector function of pathogenic T cells, given that proliferative response and IFN-gamma production by lymph node cells were reduced upon restimulation with the antigen peptide in vitro. These results suggest that the ICOS/B7RP-1 interaction plays a critical role in the pathogenesis of uveitis. We also indicated that ICOS-mediated costimulation plays differential roles in EAU and experimental autoimmune encephalomyelitis, which is also a Th1 disease induced in the same manner as EAU.

Chlamydia pneumoniae and age-related macular degeneration: a role in pathogenesis or merely a chance association?

The role of inflammation in the aetiology of age-related macular degeneration (AMD) has become very topical as the discovery that genetic variation in complement pathway genes influences the risk of developing AMD. Complement factor H gene, an inhibitor of the alternative complement activation pathway along with other complement pathway genes factor F (BF) and C2 show significant contribution to the risk of AMD. The alternative complement pathway is activated by a trigger, which is often microbial in nature. One current model of AMD aetiology implicates aberrant regulation of the alternative pathway of complement, in combination with some unknown infectious agents. Chlamydia pneumoniae could be one such potential trigger of the alternative complement pathway and several investigations have linked C. pneumoniae to AMD. However, there are only a few studies to date and numbers in most studies are small. Also there are many difficulties in verifying laboratory techniques for the detection of C. pneumoniae chronic infection. As such we need to be cautious not to over interpret the current results. However, the findings certainly give impetus for further work on C. pneumoniae and AMD. This paper provides an overview of work in this area.

Supplementation of CD4+CD25+ regulatory T cells suppresses experimental autoimmune uveoretinitis

AIMS

To investigate whether supplementation of natural CD4+CD25+ regulatory T cells ameliorates mouse experimental autoimmune uveoretinitis (EAU) induced by CD4+ T cell-dependent interphotoreceptor retinoid-binding protein (IRBP).

METHODS

C57BL/6 mice were immunised with human interphotoreceptor retinoid-binding protein peptide 1-20 (IRBP(1-20)), and IRBP(1-20)-sensitised T cells were obtained. CD4+CD25+ T cells derived from naive mice were cocultured with IRBP(1-20)-sensitised T cells, and their proliferation responses and cytokine production were measured. In addition, CD4+CD25+ T cells were transferred intravenously into mice 7 or 15 days after immunisation with IRBP(1-20), and the severity of EAU and T cell proliferation responses were evaluated.

RESULTS

CD4+CD25+ regulatory T cells effectively inhibited both the proliferation of, and interleukin (IL)2, IL5 and interferon (IFN)gamma production by, IRBP(1-20)-sensitised T cells. Adoptive transfer of CD4+CD25+ regulatory T cells to IRBP(1-20)-immunised mice conferred considerable protection from EAU development and inhibition of T cell proliferation responses to IRBP(1-20).

CONCLUSION

These findings show that natural CD4+CD25+ regulatory T cells possess the ability to inhibit activation of IRBP-reactive T cells that have been already sensitised in vivo, and adoptive transfer of these cells ameliorates EAU even in the effector phase. Supplementation of natural CD4+CD25+ regulatory T cells may have therapeutic potential for effective treatment of uveitis.

Photoreceptor mitochondrial oxidative stress in early experimental autoimmune uveoretinitis

AIMS

In early S-antigen induced experimental uveitis (EAU), photoreceptor mitochondrial proteins are nitrated prior to macrophage infiltration of the retina, suggesting that oxidative stress is an initial event in the development of EAU. We attempted to detect the oxidative stress and localise it in the EAU retina.

METHODS

Lewis rats were immunised with S-antigen in complete Freund's adjuvant (CFA). Animals were injected with CFA alone and non-immunised animals served as controls. Immunised and non-immunised animals were killed on day 5 and subsequent days. Isolated retinas were processed for inducible nitric oxide synthase (iNOS), tumour necrosis factor (TNF)alpha, interferon (IFN)gamma, interleukin (IL)Ialpha and CD28 expression by real time polymerase chain reaction. In addition, iNOS was colocalised with cytochrome c oxidase on day 5 of EAU. Oxidative stress was detected by 2', 7'-dichlorodihydrofluorescein diacetate and localised by a mitochondrial specific marker. Leucocyte and T cell infiltration in the retina/choroid was evaluated by immunohistochemistry.

RESULTS

The iNOS, TNFalpha, IFNgamma, IL1alpha and CD28 transcripts were significantly upregulated on day 5 in EAU, and iNOS was colocalised with cytochrome c oxidase in the photoreceptor mitochondria. Oxidative stress was seen primarily in the photoreceptor mitochondria. Occasional T cells were present in the retina at this stage.

CONCLUSIONS

During early EAU, mitochondrial oxidative stress is selectively noted in the photoreceptor inner segments. The oxidative stress appears to result from iNOS upregulation in the photoreceptor mitochondria and cytokine generation in the retina by a few antigen specific infiltrating T cells.

Sialoadhesin promotes the inflammatory response in experimental autoimmune uveoretinitis

Macrophages are a prominent component of the effector cell compartment in a number of CD4+ T cell-mediated organ-specific autoimmune diseases. In this study, we investigated the role of the sialic acid binding Ig-like lectin sialoadhesin (Sn, Siglec-1) in a model of interphotoreceptor retinal binding protein peptide-induced experimental autoimmune uveoretinitis in mice with targeted deletion of Sn. Our data show that compared with wild-type mice, experimental autoimmune uveoretinitis is reduced in severity in the initial stages in the Sn knockout (KO) mice. In addition, there is a reduction in the proliferative capacity of T cells from the KO mice draining lymph nodes after immunization with interphotoreceptor retinal binding protein peptides, which is manifest some days before disease onset and persists for the duration of disease. Furthermore, activated T cells from the draining lymph nodes of Sn KO mice secrete lower levels of IFN-gamma. The data suggest a role for Sn in "fine tuning" the immune response to autoantigens by modulating T cell priming.

Intravitreal injection of Tacrolimus (FK506) suppresses ongoing experimental autoimmune uveoretinitis in Rats

AIM

To determine whether intravitreal injection of tacrolimus suppresses ongoing experimental autoimmune uveoretinitis (EAU) in rats.

METHODS

Rats were immunised with interphotoreceptor retinoid-binding protein peptide (R14) and given an intravitreal injection of tacrolimus on day 12 after immunisation. Intraocular inflammation was assessed by slit-lamp biomicroscopy and histopathological examination. Interferon gamma and tumour necrosis factor alpha protein levels in the ocular tissues were measured. Gene expression of chemokines was determined in ocular tissues by reverse transcription-polymerase chain reaction. To evaluate the systemic effect of intravitreal injection of tacrolimus, delayed-type hypersensitivity was measured by ear swelling.

RESULTS

Clinical and pathological scores showed that ocular inflammation of tacrolimus-treated eyes was markedly less than that of vehicle-treated eyes. The amount of interferon gamma and tumour necrosis factor alpha was considerably inhibited in tacrolimus-treated eyes. The gene expression of monocyte chemattractant protein-1 (MCP-1) and regulated upon activation, normal T cell expressed and secreted (RANTES) was markedly reduced in tacrolimus-treated eyes. Delayed-type hypersensitivity responses were not impaired in tacrolimus-treated rats.

CONCLUSIONS

Intravitreal injection of tacrolimus was highly effective in suppressing the ongoing process of EAU without any side effects on systemic cellular immunity. This treatment may be useful in the management of patients with severe uveitis.

Regulatory T cells control uveoretinitis induced by pathogenic Th1 cells reacting to a specific retinal neoantigen

In many clinical cases, uveitis develops secondary to an infection. This could result from peripheral activation followed by ocular penetration and reactivation of T cells specific for microbial Ags expressed in the retina. To gain insights into the pathophysiology of uveitis, we developed a new mouse model based on stable retinal expression of influenza virus hemagglutinin (HA) neoantigen by adeno-associated virus-mediated gene transfer. One month thereafter, we adoptively transferred HA-specific T cells, which were activated in vitro or in vivo. Intraocular inflammation was clinically and histologically observed in all animals within 15 days. The ocular infiltrate was composed mostly of macrophages and HA-specific T cells with a proinflammatory cytokine profile. Depletion of CD4(+)CD25(+) regulatory T cells exacerbated the disease, whereas HA-specific CD4(+)CD25(+) T cells given i.v. controlled the disease. This novel model should allow to better study the pathophysiology and therapeutic of uveitis.

Melanocortin 5 receptor and ocular immunity

The nervous system contributes to the mechanisms of ocular immune privilege by the constitutive presence of the immunosuppressive neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) in the eye. Alpha-MSH through the melanocortin 5 receptor (MC5r) mediates induction of CD4+ regulatory T cells that suppress in an antigen specific manner autoimmune disease. We investigated whether there was a role for MC5r expression in ocular immunity and the natural induction of regulatory T cells that emerged following resolution of experimental autoimmune uveoretinitis (EAU). Unlike wild type mice, EAU in MC5r-/- mice caused severe retinal damage, did mice expressed a not induce the emergence of ocular autoantigen regulatory immunity in the spleen, and the MC5r-/- classical memory immune response when reimmunized with ocular autoantigen. There was expression of MC5r in retinal pigment epithelial cells, in the ganglion cell and neural outer plexiform layers of healthy wild type mice retinas. The recovery of the ocular microenvironment from EAU was not dependent on the expression of MC5r, nor was the recovery dependent on the induction of CD4+ regulatory T cells (Treg cells) in the spleen. However, protection of the retina from the inflammatory damage of EAU and the induction of ocular autoantigen-responsive CD4+ Treg cells in the post EAU spleen requires expression of MC5r.

Galectin-1 Suppresses Autoimmune Retinal Disease by Promoting Concomitant Th2- and T Regulatory-Mediated Anti-Inflammatory Responses

Intraocular inflammatory diseases are a common cause of severe visual impairment and blindness. In this study, we investigated the immunoregulatory role of galectin-1 (Gal-1), an endogenous lectin found at sites of T cell activation and immune privilege, in experimental autoimmune uveitis (EAU), a Th1-mediated model of retinal disease. Treatment with rGal-1 either early or late during the course of interphotoreceptor retinoid-binding protein-induced EAU was sufficient to suppress ocular pathology, inhibit leukocyte infiltration, and counteract pathogenic Th1 cells. Administration of rGal-1 at the early or late phases of EAU ameliorated disease by skewing the uveitogenic response toward nonpathogenic Th2 or T regulatory-mediated anti-inflammatory responses. Consistently, adoptive transfer of CD4(+) regulatory T cells obtained from rGal-1-treated mice prevented the development of active EAU in syngeneic recipients. In addition, increased levels of apoptosis were detected in lymph nodes from mice treated with rGal-1 during the efferent phase of the disease. Our results underscore the ability of Gal-1 to counteract Th1-mediated responses through different, but potentially overlapping anti-inflammatory mechanisms and suggest a possible therapeutic use of this protein for the treatment of human uveitic diseases of autoimmune etiology.

Mapping Immune Responses to mRBP-3 1-16 Peptide with Altered Peptide Ligands

PURPOSE

Experimental autoimmune uveoretinitis (EAU) can be induced in C57BL/6 mice (I-A(b)) using human retinoid-binding protein-3 (hRBP-3, previously IRBP) residues 1-20. This study of a truncated murine peptide (mRBP-3 1-16) was conducted to determine its pathogenic potential and to characterize partially its interaction with specific T cells.

METHODS

After immunization with mRBP-3 1-16 or hRBP-3 1-20, EAU was assessed by immunohistochemistry. The immune response was assessed by tritiated thymidine incorporation and cytokine production analyzed by enzyme-linked immunosorbent assay (ELISA). T-cell receptor (TCR)- and major histocompatibility complex (MHC)-binding of mRBP-3 1-16 was studied by modeling and by using altered peptide ligands (APLs) and T-cell clones.

RESULTS

mRBP-3 1-16 induced EAU in C57BL/6 mice, with severity and kinetics comparable to that after immunization with hRBP-3 1-20. T cells taken from mice immunized with mRBP-3 1-16 had a Th1 phenotype and proliferated in response to reactivation with mRBP-3 1-16, hRBP-3 1-20, or mRBP-3 1-16 APLs. mRBP-3 1-16 APLs elicited at least five distinct patterns of reactivity when tested with the mRBP-3 1-16-reactive T-cell clones.

CONCLUSIONS

mRBP-3 1-16 immunizes and causes EAU in C57BL/6 mice. The studies using T-cell clones and APLs demonstrate that the immune response to mRBP-3 1-16 is drawn from a diverse population of antigen-specific T cells with a Th1 phenotype. Modeling and analysis of clones indicate that nonpathogenic T cells of an mRBP-3 1-16-reactive T-cell line recognize the peptide in a single register.

Poststreptococcal syndrome uveitis: a descriptive case series and literature review

PURPOSE

To describe the clinical features in a series of patients with poststreptococcal uveitis and to review literature on the pathophysiology and management.

DESIGN

Retrospective and descriptive case series.

PARTICIPANTS

Ten consecutive cases of poststreptococcal syndrome uveitis diagnosed between 1996 and 2003.

METHODS

Review of patient case notes.

MAIN OUTCOME MEASURES

Age, laterality, clinical features, and anti-streptococcal lysin O titers.

RESULTS

Ten consecutive cases of poststreptococcal syndrome uveitis were identified. All our cases had bilateral nongranulomatous inflammation and raised anti-streptococcal lysin O titers. Collating data from previous reports and this series showed that 96% of the patients were below 40 years of age, and 87.5% had evidence of previous streptococcal infection. One third of the patients had posterior segment involvement. In our patients, this was in the form of vitritis, focal retinitis, optic disc swelling, and multifocal choroiditis.

CONCLUSIONS

Poststreptococcal syndrome uveitis should be considered in the etiology of acute bilateral nongranulomatous uveitis in children and young patients.

Treatment of experimental autoimmune uveoretinitis with poly(lactic acid) nanoparticles encapsulating betamethasone phosphate

We have developed nanoparticles (NPs), which are capable of targeting a specific lesion and gradually releasing the agent at the site over a prolonged time period after a single intravenous administration. In this study, we evaluated the effects of intravenously administered poly(lactic acid) nanoparticles encapsulating betamethasone phosphate (BP-PLA NPs) on experimental autoimmune uveoretinitis (EAU) in Lewis rats. To determine the localization of NPs within the retina and choroid of rats with EAU, rhodamine (Rh)-encapsulated PLA NPs were injected intravenously and visualized by confocal microscopy. After the disease onset of EAU induced by S-antigen peptide in Lewis rats, either BP-PLA NPs, BP, or saline was injected intravenously, and the eyes were obtained 7 days following treatment and the histological score was determined. The clinical course of EAU was examined using pathological findings and the expression of the glial fibrillary acidic protein, rod opsin, and the surface markers of inflammatory cells (ED1 and pan T-cell) were immunohistochemically determined. Furthermore, T-cell proliferation and delayed-type hypersensitivity (DTH) to S-antigen were assessed. Intravenously injected Rh-PLA NPs accumulated in the retina and choroid of rats with EAU within 3 hr and remained over the succeeding 7-day-period. Furthermore, systemically administered BP-PLA NPs reduced the clinical scores of rats with EAU in 1 day, which were maintained for 2 weeks and decreased the histological scores. In addition, the ocular infiltration of activated T-cells and macrophages in addition to the hypertrophy of Müller cells were markedly reduced with this treatment. Meanwhile, T-cell proliferation and DTH of BP-PLA NPs-treated rats against S-antigen peptide were not significantly different from those of saline-treated rats. Systemically administered BP-PLA NPs inhibit the development of EAU due to the targeting and the sustained release of steroids in situ. The results of these studies suggest that the systemic administration of BP-PLA NPs may lead to a new therapeutic strategy in controlling intraocular inflammation.

Toll-like receptors in ocular immunity and the immunopathogenesis of inflammatory eye disease

Microbial agents have an important role in the pathogenesis of various inflammatory eye diseases, such as uveitis and keratitis. Microbial infections of the eye such as microbial keratitis, ocular onchocerciasis, bacterial endophthalmitis, viral retinitis, and other infectious uveitis are unfortunately common. In addition, microbial agents have been implicated in the pathogenesis of "non-infectious" immune mediated diseases such as HLA-B27 associated acute anterior uveitis. Toll-like receptors (TLR) are a family of pattern recognition receptors that initiates rapid host innate immune response to microbial components known as pathogen associated molecular patterns, which are unique to a given class of microbes, such as lipopolysaccharide of Gram negative bacteria. Recent in vitro and in vivo studies have demonstrated the expression and function of TLRs in the eye, with significant implications for better understanding of ocular immunity and the pathogenesis of inflammatory eye diseases affecting the cornea, uvea, and retina.

Differentiation to the CCR2+ inflammatory phenotype in vivo is a constitutive, time-limited property of blood monocytes and is independent of local inflammatory mediators

It is proposed that CCR2+ monocytes are specifically recruited to inflammatory sites, whereas CCR2- monocytes are recruited to normal tissue to become resident macrophages. Whether these subsets represent separate lineages, how differential trafficking is regulated and whether monocytes undergo further differentiation is uncertain. Using a mouse model of autoimmune uveoretinitis we examined monocyte trafficking to the inflamed retina in vivo. We show that bone marrow-derived CD11b+ F4/80- monocytes require 24 to 48 h within the circulation and lymphoid system before acquiring the CCR2+ phenotype and trafficking to the inflamed retina is enabled. This phenotype, and the capacity to traffic were lost by 72 h. Monocyte CCR2 expression followed a similar time course in normal mice indicating that differentiation to an inflammatory phenotype is a constitutive, time-limited property, independent of local inflammatory mediators. Phenotypic analysis of adoptively transferred cells indicated that circulating inflammatory monocytes also differentiate into CD11c+ and B220+ dendritic cells and F4/80+ tissue macrophages in vivo. Our data supports the hypothesis of continuous extravasation and progressive differentiation over time of inflammatory monocytes in the circulation rather than replication within the actively inflamed tissue, and supports the concept of myeloid dendritic cell differentiation from trafficking monocytes under physiological conditions in vivo.

A selective role for the TNF p55 receptor in autocrine signaling following IFN-gamma stimulation in experimental autoimmune uveoretinitis

IFN-gamma stimulates macrophage activation and NO production, which leads to destruction of the retina in experimental autoimmune uveoretinitis. In this study, we investigate the mechanism of disease resistance in TNF p55 receptor-deficient animals. We show that although T cell priming is relatively unaffected, macrophages lacking the TNF p55 receptor fail to produce NO following IFN-gamma stimulation because of a requirement for autocrine TNF-alpha signaling through the TNF p55 receptor. In contrast to the impaired activation of NO synthesis, MHC class II up-regulation was indistinguishable in wild-type and TNFRp55-/- mice stimulated with IFN-gamma. These defects could be overcome by stimulating macrophages with LPS. Together, these results show that selected aspects of IFN-gamma activation are controlled by autocrine secretion of TNF-alpha, but that this control is lost in the presence of signals generated by pathogen-associated molecular patterns recognizing receptors.

CCR5-Deficient Mice Develop Experimental Autoimmune Uveoretinitis in the Context of a Deviant Effector Response

PURPOSE

Experimental autoimmune uveoretinitis (EAU) is an organ-specific, Th1-cell-mediated disease that targets the neural retina. CCR5 is a chemokine receptor expressed on Th1 cells that promotes their migration. In CCR5-deficient mice, we examined the role of CCR5 in the development of EAU induced by immunization with interphotoreceptor retinoid-binding protein (IRBP) peptide.

METHODS

Wild-type or CCR5-deficient B6 mice were immunized with human IRBP peptide 1-20 (hIRBP-p), and the severity of EAU was assessed clinically and histologically. Splenocytes and cells of regional lymph nodes near the eye were collected and their proliferation and production of IL-6, IL-10, IFN-gamma, and CCL2 (MCP-1) in response to hIRBP-p stimulation were measured. Moreover, the intraocular levels of these cytokines were analyzed.

RESULTS

Immunization with hIRBP-p induced EAU in CCR5-deficient mice with a severity comparable to that in wild-type mice. Histologically, T-cell infiltration of the eye was reduced, but granulocyte infiltration was augmented in CCR5-deficient mice. Although splenic T cells from CCR5-deficient mice produced IFN-gamma but not IL-10 on stimulation by hIRBP-p, T cells from the regional lymph nodes failed to produce both cytokines. IL-6 production in the eye and IL-6 and CCL2 production by splenic T cells were predominantly augmented in CCR5-deficient mice.

CONCLUSIONS

The development of EAU is not prevented in CCR5-deficient mice. Although T-cell infiltration into the eye is apparently reduced in CCR5-deficient mice, the defect is compensated for by granulocyte infiltration, supposedly mediated by augmented intraocular production of IL-6.

Genetic deficiency of C3 as well as CNS-targeted expression of the complement inhibitor sCrry ameliorates experimental autoimmune uveoretinitis

In this report, we describe the effect of complement deficiency and inhibition on experimental autoimmune uveoretinitis (EAU). C57BL/6 mice genetically deficient in C3 (C3-/-) or expressing a soluble complement activation inhibitor (soluble complement receptor related protein Y or sCrry) in a CNS-targeted fashion, (sCrry/GFAP) were induced for EAU via peripheral immunisation with a peptide of amino acids 1-20 of human interphotoreceptor retinoid binding protein in complete Freund's adjuvant with concurrent intraperitoneal pertussis toxin. The incidence and severity of EAU in the mutant mice was compared with that in simultaneously induced C57BL/6 wild type mice. The sCrry protein was detected in retinal extracts from transgenic but not wild type mice by western blot. C3-/- mice had a significant reduction in the incidence of EAU compared with wild type mice (incidence 44 versus 89%, respectively, p=0.0417) and a significant reduction in the severity of EAU (median disease score values 0 versus 1.3, respectively, p=0.0253). Similarly, sCrry mice had a significant reduction in the incidence of EAU compared with wild type mice (incidence 57 versus 100% respectively, p=0.0033) and a significant reduction in the severity of EAU (median disease score values 0.18 versus 1.85, respectively, p=0.0054). A genetic deficiency of C3 and production of a soluble complement inhibitor targeted to the CNS and eye are protective against EAU.

Disruption of CD40/CD40-ligand interactions in a retinal autoimmunity model results in protection without tolerance

We examined the role of CD40/CD40L interactions on the development of experimental autoimmune uveoretinitis (EAU), a cell-mediated, Th1-driven autoimmune disease that serves as a model for autoimmune uveitis in humans. EAU-susceptible B10.RIII mice immunized with the retinal autoantigen interphotoreceptor retinoid binding protein in CFA and treated with anti-CD40L Ab (MR1) had reduced incidence and severity of disease. Real-time PCR analysis revealed that the innate and adaptive responses of protected mice were reduced, without an obvious shift toward a Th2 cytokine profile. In contrast to some other reports, no evidence was found for regulatory cells in adoptive transfer experiments. To determine whether CD40L blockade resulted in long-term tolerance, mice protected by treatment with MR1 Ab were rechallenged for uveitis after circulating MR1 Ab levels dropped below the detection limit of ELISA. MR1-treated mice developed severe EAU and strong cellular responses to interphotoreceptor retinoid binding protein, comparable to those of control mice. These responses were higher than in mice that had not received the primary immunization concurrently with anti-CD40L treatment. We conclude that 1) CD40/CD40L interaction is required for EAU and its disruption prevents disease development; 2) CD40L blockade inhibits the innate response to immunization and reduces priming, but does not result in immune deviation; and 3) protection is dependent on persistence of anti-CD40L Abs, and long-term tolerance is not induced. Furthermore, immunological memory develops under cover of CD40L blockade causing enhanced responses upon rechallenge. Taken together, our data suggest that ongoing CD40/CD40L blockade might be required to maintain a therapeutic effect against uveitis.

Repertoire, diversity, and differentiation of specific CD8 T cells are associated with immune protection against human cytomegalovirus disease

To determine the correlates of immune recovery from active human CMV (HCMV) disease, we compared the antigenic repertoire, diversity, magnitude, and differentiation of HCMV-specific CD8+ T cells in HIV-HCMV coinfected subjects with no, cured, or active HCMV disease and in healthy HIV-negative HCMV-positive controls. ELISPOT-IFN-gamma assays using peptide pools spanning the pp65 and immediate early 1 (IE1) HCMV proteins showed that HCMV-specific CD8+ T cells had a significantly broader antigenic repertoire and greater diversity in HIV-positive patients controlling HCMV replication than in those with active HCMV disease, but the magnitude of the CD8 T cell response did not differ between the different groups. HCMV-specific T cells mainly were focused against IE1 during the short-term recovery from retinitis, and switched toward pp65 during long-term recovery. HCMV-specific T cells displaying an "early" (CD8+CD27+CD28+) and "intermediate" (CD8+CD27-CD28+) differentiation phenotype were increased significantly during long-term recovery compared with other HIV-positive patients and were nearly undetectable during active HCMV disease. HCMV-specific T cells with a "late" (CD8+CD27-28-) differentiation phenotype predominated in all cases. Therefore, restoration of immune protection against HCMV after active HCMV disease in immunodeficient individuals is associated with enlarged repertoire and diversity, and with early differentiation of virus-specific CD8+ T cells, thus defining immune correlates of protection against diseases caused by persistent viruses.

Mice lacking the IFN-gamma receptor or fyn develop severe experimental autoimmune uveoretinitis characterized by different immune responses

Endogenous interferon (IFN)-gamma negatively regulates experimental autoimmune uveoretinitis (EAU), a Th1-mediated disease. Although it is well known that IFN-gamma exerts its effects by binding to the IFN-gamma receptor (IFN-gammaR), the role that IFN-gammaR plays in the development of EAU has not been investigated. Fyn has been reported to inhibit Th2 differentiation. We aimed to investigate how endogenous IFN-gammaR and fyn, which influence Th1/Th2 differentiation, participate in the development of EAU. Sex-matched 6- to 10-week-old C57BL/6 wild-type (WT), IFN-gammaR knockout (GRKO) and fyn knockout (fyn KO) mice were compared. Mice were immunized subcutaneously with human interphotoreceptor retinoid-binding protein peptide 1-20 emulsified in Freund's complete adjuvant together with an intraperitoneal injection of Bordetella pertussis toxin. Three weeks later, mice were sacrificed, and their eyes and spleens were harvested for histopathologic analyses and examination of cellular immune responses, respectively. Cellular immune responses were evaluated by measuring the proliferative responses and cytokine production [interleukin (IL)-4, IL-5, IL-6, IL-13, IFN-gamma and tumor necrosis factor (TNF)-alpha] of splenocytes. The incidence of EAU was 40.0% in WT mice, 59.3% in GRKO mice and 78.6% in fyn KO mice. The average EAU score was 0.294 in WT mice, 0.917 in GRKO mice and 1.063 in fyn KO mice. Upon EAU induction, significant infiltration of eosinophils into the eyes was observed in GRKO and fyn KO mice compared to WT mice. Splenocytes from GRKO mice proliferated against the antigen and a mitogen more vigorously than those from WT and fyn KO mice. Stimulation of splenocytes with the antigen induced a higher production of IL-4, IL-6, IL-13 and IFN-gamma in GRKO mice compared to WT and fyn KO mice. In contrast, IL-5 and TNF-alpha were most abundantly produced by splenocytes from fyn KO mice compared to WT and GRKO mice. The incidence and mean severity of EAU were significantly higher in GRKO and fyn KO mice than in WT mice, suggesting that endogenous IFN-gammaR and fyn negatively regulate the development of EAU. The different cytokine production patterns by the GRKO and fyn KO mice indicate that the negative regulatory mechanism mediated by IFN-gammaR and fyn may differ.