Inhibition of interphotoreceptor retinoid-binding protein-induced uveitis by monoclonal antibodies

Immunization of Lewis rats with interphotoreceptor retinoid-binding protein (IRBP) resulted in development of uveoretinitis in 100% (12/12) of the animals so injected. In the present study, we attempted immunotherapy of this intraocular inflammation using the monoclonal antibodies anti-I-A and anti-I-E. The antibodies were injected 1 day before and on days 1 and 2 after IRBP sensitization, and the animals were killed 16 days later. Anti-I-A treatment inhibited the disease in 83% (10/12) of the animals, while anti-I-E antibodies resulted in inhibition of the disease in 67% (8/12) of the animals. All rats injected with preimmune IgG (control animals) developed uveoretinitis. The anti-I-A and anti-I-E antibodies exerted a specific suppressor effect on the immune response of these animals. Thus, anti-I-A and anti-I-E antibodies administered at the time of antigen priming abolished the immune function and inhibited the development of autoimmune uveitis.

Predominant usage of V beta 8.3 T cell receptor in a T cell line that induces experimental autoimmune uveoretinitis (EAU)

Experimental autoimmune uveoretinitis (EAU) is a T cell-mediated autoimmune disease induced in animals by immunization with retinal proteins (or synthetic fragments derived from them) in adjuvant, and it is considered a model of human autoimmune diseases of the eye. To study the T cell clonotypes that may be involved in EAU, we analyzed the T cell repertoire of three related T cell lines: the pathogenic line LR16, specific to the major uveitogenic epitope of IRBP; its pathogenic subline J; and its nonpathogenic subline A. We examined the expression of the genes coding for the variable regions of the 20 known Lewis rat T cell antigen receptor (TCR) V beta families. The nonpathogenic subline was found to contain mostly T cells expressing V beta 5, V beta 8.2, and V beta 19 while the pathogenic subline consisted mainly of cells expressing V beta 8.3 TCRs. Genomic Southern blot analysis of DNA from the pathogenic subline showed that V beta 8.3-expressing T cells were the dominant clonotype, and DNA sequence analyses of V beta 8.3 cDNAs revealed that two V beta 8.3 TCRs were expressed in the pathogenic subline. One of the V beta 8.3 cDNAs encoded a variable region gene segment identical to previously reported rat V beta 8.3 TCR while the other differed by two amino acids in the second complementarity determining region (CDR2). Taken together with previous data showing overrepresentation of V beta 8-expression in T cell lines that induce EAU, but not in nonuveitogenic T cell lines, our results suggest that V beta 8.3-expressing T cells represent a pathogenic clonotype in IRBP-induced EAU.

Does the lens serve as a 'sink' for iron during ocular inflammation?

Twenty-four hours after induction of ocular inflammation by intravitreal injection of endotoxin (10 ng), the intraocular fluid (IOF, aqueous and vitreous humors) concentration of iron (Fe) increased. This was presumably due to entry of the plasma Fe-binding protein, transferrin, into the IOFs through disrupted blood ocular barriers. After 1 day of inflammation the Fe concentration in lenses from the inflamed eye was 60% greater than that measured in contralateral control lenses. By day 15, lens Fe concentration had returned to levels of the contralateral control lenses. There was a distinct relationship between the dose of endotoxin used and the amount of Fe accumulated by the lens. The Fe concentration in lenses from eyes injected with 100 ng endotoxin was 0.376 +/- 0.027 micrograms g-1 wet weight compared to 0.214 +/- 0.014 micrograms g-1 in lenses from eyes injected with 0.25 ng endotoxin. In a previous study, copper (Cu) concentration in the IOFs was elevated to the same extent as Fe in response to intravitreal injection of endotoxin. However, in the present study, lenticular Cu concentration was unaltered at the highest (100 ng) dose of endotoxin. Since the increase in lens uptake was selective for Fe, there may be a specific Fe uptake mechanism in this ocular tissue. The physiological reasons for and possible pathological consequences of such a process are discussed.

Inhibition of experimental autoimmune uveitis by retinal photoreceptor antigens coupled to spleen cells

Experimental autoimmune uveitis (EAU) and experimental autoimmune pinealitis (EAP) are CD4+ T cell-mediated inflammatory diseases of the uveal tract and retina of the eye and of the pineal gland. EAU and EAP can be induced by several retinal autoantigens including S-antigen (S-Ag) and interphotoreceptor retinoid binding protein (IRBP). In this study we investigated the effect of intravenous administration of S-Ag and IRBP coupled to syngeneic spleen cells on the development of EAU and EAP. Injection of S-Ag or IRBP coupled to spleen cells 5 days prior to immunization with native S-Ag or IRBP, respectively, was effective in preventing the induction of EAU and EAP in LEW rats. Conversely, LEW rats receiving S-Ag-coupled spleen cells and challenged with IRBP or LEW rats receiving IRBP-coupled spleen cells and challenged with S-Ag developed a severe EAU within 10 days to 2 weeks following immunization, as did all control animals receiving sham-coupled spleen cells and challenged with the two retinal antigens. The results show that the administration of retinal autoantigens coupled to spleen cells effectively protects against the development of EAU when animals are subsequently challenged with the tolerizing antigen but not when challenged with another unrelated pathogenic retinal autoantigen.

Preclinical and clinical study of FK506 in uveitis

Efficacy of a new immunosuppressive agent, FK506, in refractory uveitis was studied in 8 patients: 5 with Behcet's disease and 3 with idiopathic retinal vasculitis. The agent was given by oral administration every 12 hours. The previous therapy with systemic corticosteroids or immunosuppressive agents including cyclosporine failed to subside uveitis in these cases. During the observation period of 21.6 +/- 7.8 weeks (mean +/- SD) under FK506 at doses with 0.05, 0.1, 0.15 or 0.2 mg/kg/day, the visual acuity was increased in 44% of treated eyes, unchanged in 44% and decreased in 12%. The inflammatory activity in the ocular fundus was improved in 69% and unchanged in 6% of treated eyes. The effects of FK506 on uveitis by the criteria of improvement of visual acuity and uveitis activity was dose-dependent: 0.05 and 0.1 mg/kg/day were ineffective but 0.15 and 0.2 mg/kg/day were effective in most cases. One patient with Behcet's disease converted from cyclosporine developed moderate renal impairment in 4 weeks under FK506 and the therapy was discontinued in 8 weeks, though the uveitis activity as well as visual acuity was markedly improved. Other 7 cases had no side effect of FK506. Although the number of cases was small and observation period was short, the present clinical data indicate that FK506 is effective to treat refractory uveitis.

[Participation of sodium iodate in the induction of experimental autoimmune uveoretinitis (EAU)]

It is known that Brown Norway (BN) rats show resistance to the development of experimental autoimmune uveoretinitis (EAU). Although BN rats don't develop EAU easily when they were immunized with S antigen containing emulsified complete Freund's adjuvant, this paper reports on the development of EAU at the rate of 40-60% in BN rats when immunization is preceded by an injection of more than 0.5 mg (1.79 mg/kg of body wt) of sodium iodate which leads to the destruction of retinal pigment epithelium (RPE). It was thought that the destruction of RPE participated in the induction of EAU. Therefore, it is considered that the existence of RPE may play an important role in the induction of EAU.

Glauline (metipranolol) induced uveitis and increase in intraocular pressure

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[Endogenous uveitis in disseminated intravascular coagulation induced by endotoxin]

A study was made of endogenous uveitis in experimental disseminated intravascular coagulation (DIC) in rabbits. Endotoxin was injected intravenously twice with a 24-hour interval. The time courses of the following were examined: 1) aqueous flare using a laser flare-cell meter 2) the number of leukocytes in the peripheral blood 3) the tumor necrosis factor (TNF) activity in the serum and 4) histopathological changes in the eye, lung, liver and kidney. Aqueous flare increased at 1 hour and was maximal at 6 hours, accompanied by a rapid increase in TNF activity at 1 hour following the first endotoxin administration. The number of leukocytes decreased to 963 +/- 266 cells/mm3 at 1.5 hours with subsequent leukocytosis within 12 hours. After the second injection of endotoxin, the aqueous flare peaked in 30 minutes and was twice as high as the first peak. Leukocyte number and TNF activity showed the same behavior. However, TNF activity was 20% that of the first peak. Histopathological examination indicated fibrin formation in the small vessels of systemic organs within 3 hours following the second administration of endotoxin. Endotoxin induced uveitis was induced in experimental DIC, and leukocytes and TNF activity may thus perform important roles.

The lysosomal enzymes of the iris-ciliary body are retained in their organelles and exhibit increased activities during acute uveal inflammation

Acute uveal inflammation, characterised by conjunctival hyperaemia, limbal vascular injection, iritis and aqueous flare, was induced in the rabbit eye by a single intravitreal injection of 10 micrograms of Shigella endotoxin. Twenty-four, 48 and 72 h after endotoxin administration, lysosomal-rich fractions and cytosolic supernatants were prepared from iris-ciliary bodies and the enzymatic activities of some lysosomal hydrolases in these fractions were assayed. Acid phosphatase, aryl sulphatase and N-acetyl-B-D-glucosaminidase exhibited increased activities in the lysosomal preparations from inflamed iris-ciliary bodies, relative to the activities of the same enzymes in lysosomal fractions from normal iris-ciliary bodies. No significant differences in activities were obtained for these enzymes in cytosolic supernatants from normal and inflamed iris-ciliary bodies. The results suggest that during acute ocular inflammation the lysosomal hydrolases are retained in their organelles at an elevated state of activity.

Prolonged effect of a new platelet-activating factor antagonist on ocular vascular permeability in an endotoxin model of uveitis

Platelet-activating factor (PAF) is a membrane-derived lipid mediator involved in inflammatory responses. In the present study, the effect of a new, synthetic PAF antagonist, BN 50726, on ocular-blood barrier breakdown was investigated in a model of anterior uveitis produced by injection of 5 microL 0.1% endotoxin into the midstroma of rabbit corneas. Severe keratitis and anterior uveitis were induced in 3-4 days. BN 50726 was applied once subconjunctivally and then topically four times daily for 5 days in a blind-designed experiment. Vascular permeability was measured each day with an automated fluorophotometer after injection of fluorescein-conjugated dextran. BN 50726 significantly decreased ocular vascular permeability up to the fifth day of treatment. In another series of animals, slit-lamp observation showed significant reduction in iris erythema and epithelial damage with BN 50726 treatment. These results show that the PAF antagonist reduces early and late responses in uveitis. The possibility that PAF interacts with other inflammatory mediators to affect breakdown of the blood-aqueous barrier is discussed.

Clinical and pathological effects on the rabbit's eye of some plant-derived ophthalmic swabs

The stems of corn, millet, sugar cane and the banana leaf frond excite some clinical and pathological effects in the rabbit's eye when implanted either into the anterior chamber (AC) or subconjunctivally. These effects have not been sight threatening. The materials can either be left to be cleared by the body's phagocytes when they produce mild inflammatory reaction or removed surgically if the inflammatory response is moderate when fragments have been left intraocularly.

Ocular inflammatory effects of intravitreally injected tumor necrosis factor-alpha and endotoxin

Intravitreal injection of human recombinant tumor necrosis factor-alpha (TNF) induced inflammation in the rabbit eye characterized by dilation of blood vessels in the iris, disruption of the blood-ocular barriers, infiltration of inflammatory cells into the anterior chamber, and accumulation of prostaglandin E in intraocular fluids. Inflammation first appeared on day 1, increased on day 2, and remained elevated on day 7. The inflammatory cell infiltrate in the anterior segment of the eye was largely monocytic on days 1 and 2; by day 7 large numbers of lymphocytes were also present. TNF-induced ocular inflammation therefore differed from that reported for intravitreally injected endotoxin in terms of time course and the types of inflammatory cells in the aqueous humor. In a series of experiments in which combinations of TNF and endotoxin were used, intravitreal injection of TNF, 24 h after a low dose of Escherichia coli endotoxin, produced no more inflammation than that produced by TNF following an injection of endotoxin vehicle. However, if TNF was injected 24 h before endotoxin, the resulting inflammation was greater than that observed in animals given TNF followed by endotoxin vehicle.

Dose-limiting toxicity of rifabutin in AIDS-related complex: syndrome of arthralgia/arthritis

We studied the tolerance of humans to rifabutin, a rifamycin with antimycobacterial and in vitro anti-HIV activity. Sixteen subjects with AIDS-related complex were treated for 4-66 weeks with stepwise increasing oral doses of rifabutin from 300 to 2400 mg/day. The highest dose attained was twice that previously reported for humans. Serum and cerebrospinal fluid levels of drug were detected by high-pressure liquid chromatography. A reversible syndrome of arthritis/arthralgia, not previously described, was seen in most (nine out of 10) of those given doses exceeding 1050 mg/day. Uveitis and aphthous stomatitis developed at doses of approximately 1800 mg in two of those with joint manifestations. Typical manifestations of Reiter's syndrome were not seen in any patient. An orange-tan skin pigmentation was almost universal. Other toxicities resembled those previously associated with rifampin. Serum levels did not approach those found to inhibit HIV significantly in vitro. No consistent antiviral or immunological effects were observed; even at the highest doses, rifabutin did not appear to inhibit cellular immunity. Rifabutin was well tolerated at daily doses blow 1 g.

Identification of multiple associative and dissociative proliferative and uveitogenic T-cell sites in human interstitial retinoid-binding protein

Human interstitial retinoid-binding protein (HIRBP) is a 136 kDa retinal protein capable of inducing experimental autoimmune uveoretinitis (EAU) and experimental autoimmune pinealitis (EAP) in Lewis (LEW) rats. In order to identify the T-cell recognition sites of HIRBP responsible for uveitogenic and proliferative responses, 125 overlapping peptides corresponding to its entire 1262 amino acid sequence were synthesized. Individual peptides were tested for their ability to induce EAU in LEW rats and to stimulate lymphocyte proliferation in rats immunized with the native molecule. Our previous results showed the presence of nine uveitogenic peptides in HIRBP with a minimum requirement of eight amino acids needed to induce EAU in LEW rats. Our present studies show nine proliferative peptides, four of which are also responsible for uveitogenicity. Another four peptides known to actively induce EAU were unable to elicit proliferative responses. However, these peptides overlapped or were adjacent to peptides that elicited good proliferative responses. A single, highly proliferative peptide was located on the amino terminus of HIRBP. In addition, EAU was adoptively transferred with lymph node cells (LNC) of LEW rats previously immunized with two synthetic peptides known to be uveitogenic. Our study indicates that human IRBP is a complex molecule containing multiple and spatially distinct T-cell epitopes responsible for its uveitogenicity, adoptive transfer of EAU and proliferative responses.

The use of synthetic peptides in the study of experimental autoimmune uveitis

S-antigen is a highly pathogenic retinal autoantigen for the induction of experimental autoimmune uveitis (EAU). EAU is predominantly a T cell mediated autoimmune disease of the uveal tract and retina of the eye and the pinealocytes of the pineal gland. Using synthetic peptides it has been possible to identify several B cell and T cell epitopes in the molecule. In addition, synthetic peptides derived from proteins of diverse origin with amino acid sequence homology to pathogenic regions of S-antigen induce an EAU which is indistinguishable from the disease induced by native S-antigen. These studies aid in the understanding of immune mechanisms in EAU and provide a basis for the pathogenesis of uveitis in humans.

A new perspective of S-antigen from immunochemical analysis

Elucidation of the amino acid sequences of retinal S-antigens from several species has allowed the fine dissection of T cell and antibody epitopes using synthetic peptides. S-antigen, isolated from retinal rod photoreceptor cells, elicits experimental autoimmune uveoretinitis (EAU), a predominantly CD4+ T-cell mediated autoimmune disease of the retina and uveal tract of the eye and pineal gland. Three uveitogenic T cell lines, R9, R17 and R208, prepared against native bovine S-antigen, human S-antigen and cyanogen bromide peptide CB123, respectively, were used to identify the T cell recognition sites responsible for uveitogenic and proliferative responses. T cell epitopes were found to be clustered into 6 regions, some of which were species-specific. The two synthetic peptides known to actively induce EAU, residues 286-297 and 303-314 of bovine S-antigen, were unable to induce significant proliferative responses in any of the three T cell lines. However, both of these sites were adjacent to synthetic peptides, residues 273-292 and 317-328, respectively, which were unable to actively induce EAU, but elicited proliferative responses from the T cell lines. We also report the presence of a new pathogenic site, also associated with an adjacent proliferative site, together in residues 343-362 of bovine S-Ag. Our results indicate that spatially separate and distinct T cell epitopes are present in S-antigen which are responsible for the active induction of EAU, lymphocyte proliferation, and adoptive transfer of EAU.

FR900506 (FK506) and 15-deoxyspergualin (15-DSG) modulate the kinetics of infiltrating cells in eyes with experimental autoimmune uveoretinitis

In order to evaluate two new immunosuppressive agents, FR900506 (FK 506) and 15-Deoxyspergualine (15-DSG), the kinetics of infiltrating cells in the eyes of Lewis rats with experimental autoimmune uveoretinitis (EAU) were studied. Rats were immunized with retinal S-antigen and treated with different doses of either FK 506 or 15-DSG. The inflammatory ocular tissues obtained at various intervals during the process of EAU were examined using an immunoperoxidase technique. The results were compared with those eyes developing EAU without treatment or with suboptimal doses or a suboptimal dose of Cyclosporine (CsA). Both FK 506 and 15-DSG, like CsA, delayed the cellular kinetics during the course of EAU. However, FK 506 had the greatest effect on the kinetics of T lymphocyte subsets by causing the greatest increase in the recruitment time of the T suppressor/cytotoxic population. FK506 treatment resulted not only in the highest inhibition of expression of IL-2 receptors on T cells, but also in the prevention of the expression of MHC class II antigens on ocular resident cells. Treatment with 15-DSG resulted in general immunosuppression on various infiltrating inflammatory cells.

Endotoxin-induced uveitis (EIU) in the rat: a study of inflammatory and immunological mechanisms

Endotoxin-induced uveitis (EIU) can be produced by systemic injection of endotoxin (ET). It is not clear yet why exclusive ocular involvement occurs in this model. To clarify this question and to establish the sequence of inflammatory events, EIU was induced in Lewis rats by footpad injection of Salmonella ET. Ocular inflammatory response (anterior chamber cells and proteins), aqueous inflammation mediators (thromboxane B2, prostaglandin E2, leukotriene B4 and substance P) and MHC class 2 (Ia) antigen expression in the ciliary body were monitored for 72 hours. Thromboxane B2 was detected early in the aqueous humor, peaking already 1 hour after ET injection. Prostaglandin E2 & leukotriene B4 peaks and a second peak of thromboxane B2 were recorded 18 hours after ET-injection, at the time of maximal ocular inflammation. MHC-class 2 expression was first detected in the ciliary body stroma at the vascular level 6 hours after ET injection and was massively expressed in the ciliary body epithelium at 18 and 72 hours. It is hypothesized that ciliary body endothelium is particularly sensitive to the effect of ET and is the site of thrombocyte adherence. Vascular damage leads in succession to cellular infiltration, release of inflammation mediators and disruption of blood-ocular barrier. MHC-class 2 expression is a secondary phenomenon and is probably at the origin of additional tissue damage from immune effector mechanisms.

The mouse as a model of experimental autoimmune uveoretinitis (EAU)

An EAU model has been developed in the mouse using the retinal soluble antigen (SAg), and the interphotoreceptor retinoid-binding protein (IRBP). Immunogenetic studies indicate that sensitivity to disease is H-2 dependent, but some data suggest that non-MHC genes may also contribute to the regulation of EAU. IRBP was a more potent uveitogen than SAg. Ability to mount lymphocyte and antibody responses was exhibited both by EAU-susceptible and by EAU-resistant strains, and could not be used as a predictive parameter. Dependence of disease induction on variables of immunization was studied in B10.A mice (I-Ak) immunized with IRBP. Use of Bordetella pertussis as additional adjuvant was a prerequisite for successful disease induction. Use of purified pertussis toxin (PTX), rather than a suspension of pertussis bacteria, allowed reduction of the immunization protocol to a single dose of IRBP in CFA. Severity and incidence of disease, as well as its clinical course, were directly affected by the dose of antigen and PTX, and could be controlled by varying their respective doses. A spectrum of disease, from hyperacute to chronic, could be obtained. The chronic type of EAU tended to relapse, with lesions reappearing after a brief period of essential quiescence. The special advantages of the murine EAU model for the study of ocular autoimmunity are discussed.

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.

Cellular immune response to Ia induction by intraocular gamma-interferon

BALB/c mice and Lewis rats were injected intraocularly with recombinant gamma-interferon (IFN-gamma). The distribution of Ia antigens and cellular infiltrates was studied over a 21-day time course. In mice, Ia antigens were induced on cells in the corneal stroma, corneal endothelium, iris, ciliary body, retinal pigment epithelium and cells in the retina. No detectable cellular infiltrate accompanied class II major histocompatibility (MHC) antigen induction in mice. In rats, cells in all of the intraocular tissues mentioned above were induced to express Ia antigens. However, in distinct contrast to mice, the induction of Ia antigens on intraocular structures in rats was accompanied by intense cellular inflammation composed predominantly of polymorphonuclear cells. These findings demonstrate that aberrant Ia expression on intraocular tissues by IFN-gamma is not sufficient to elicit a cellular autoimmune response in mice. The observed species-related differences in cellular immune response to class II MHC antigen induction on intraocular tissues parallels the susceptibility of mice and rats to experimental autoimmune uveitis.

2-(2-hydroxy-4-methylphenyl)aminothiazole hydrochloride as a dual inhibitor of cyclooxygenase/lipoxygenase and a free radical scavenger. 2nd communication: anti-inflammatory activity

The paper describes the topical anti-inflammatory activity of 2-(2-hydroxy-4-methylphenyl)aminothiazole hydrochloride (CBS-113 A), a dual inhibitor of cyclooxygenase/lipoxygenase and a potent free radical scavenger. When applied in eye drops (0.01 to 0.1% according to the model used), the drug inhibited inflammation in experimental conjunctivitis and uveitis induced by various procedures (e.g. paracentesis, endotoxin, S-antigen, albumin, Fe2+). The compound also inhibited leukocyte infiltration and histamine release when administered locally in pleural cavity with carrageenan. CBS-113 A could decrease plasma leakage induced by arachidonic acid or platelet activating factor in skin and airway, respectively. However, it was devoid of any activity when administered by systemic route. The compound appears as a potentially useful anti-inflammatory drug, in particular in ophthalmology and as an alternative to glucocorticoids, since it does not present the side effects of these steroids (e.g. worsening of herpetic keratitis).

Effect of antioxidant enzymes on experimental uveitis in rats

The antioxidant enzymes superoxide dismutase and glutathione peroxidase have been observed to be effective antiphlogistic agents in severe experimental allergic uveitis induced by retinal S antigen in rats. The role that the high concentration of antioxidants found in the eye may play in modulating acute inflammation is discussed.