Tumor necrosis factor antagonists: preliminary evidence for an emerging approach in the treatment of ocular inflammation

Biological agents for the treatment of uveitis

INTRODUCTION

The conventional treatment of uveitis includes corticosteroids and immunosuppressive agents, which are highly efficacious, but can be associated with serious systemic side effects. Over the last two decades, advances in the understanding of the pathogenesis of inflammatory diseases, as well as improved biotechnology, have enabled selective targeting of the chemical mediators of diseases. Recently, a new class of drugs called biologics, that target the various mediators of the inflammation cascade, may potentially provide more effective and less toxic treatment.

AREAS COVERED

This article is a review and summary of the peer-reviewed evidence for biologic agents in the treatment of various forms of ocular inflammation and it focuses on the potential use of other biologic agents that have been tested in experimental autoimmune uveitis. Pubmed was used as our main tool for our literature search. Some additional references were taken from books written on the subject.

EXPERT OPINION

There are a wide variety of new and emerging biological agents currently being used in the treatment of uveitis which has expanded the therapeutic horizons far beyond previous limitations.

Update on peripheral ulcerative keratitis

Ulcerative inflammation of the cornea occurs in the perilimbal cornea, and is associated with autoimmune collagen vascular and arthritic diseases. Rheumatoid arthritis is the most frequent underlying disease. The tendency for peripheral location is due to the distinct morphologic and immunologic characteristics of the limbal conjunctiva, which provides access for circulating immune complexes to the peripheral cornea via the capillary network. Deposition of immune complexes in the terminal ends of limbal vessels initiates immune-mediated vasculitis, and causes inflammatory cell and protein leakage due to vessel wall damage. Development of peripheral ulcerative keratitis associated with systemic disease may represent worsening of a potentially life-threatening disease. Accompanying scleritis, particularly the necrotizing form, is usually observed in severe cases, which may result in corneal perforation and loss of vision. Although first-line treatment with systemic corticosteroids is indicated for acute phases, immunosuppressive and cytotoxic agents are required for treatment of peripheral ulcerative keratitis associated with multisystem disorders. Recently, infliximab, a chimeric antibody against proinflammatory cytokine tumor necrosis factor-alpha, was reported to be effective in cases refractory to conventional immunomodulatory therapy. The potential side effects of these therapies require close follow-up and regular laboratory surveillance.

[Bilateral recurrent blurred vision associated with halos around sources of light and headache]

A 21-year-old male presented with headache and blurred vision associated with halos around sources of light. The visual acuity was slightly reduced and the intraocular pressure in the left eye was elevated to 44 mmHg and in the right eye to 49 mmHg. Slit lamp examination of the anterior segment revealed bilateral cells and a Tyndall phenomenon 2 +, several cell clumps adherent to the corneal endothelium, known as mutton-fat keratic precipitates and a circumscribed inflammatory infiltration of the right iris. The posterior segment of both eyes was normal. The cause of the presumed clinical diagnosis secondary open angle glaucoma due to anterior granulomatous uveitis was sarcoidosis, confirmed by elevated serological markers of angiotensin-converting enzyme (ACE), soluble interleukin-2 receptor (sIL-2R) and by pulmonary hilar lymphadenopathy. The local and systemic corticosteroid therapy was successful and also normalized the intraocular pressure.

TNFα suppresses IFNγ-induced MHC class II expression on retinal pigmented epithelial cells cultures

PURPOSE

One major consequence of retinal pigment epithelium (RPE) cell activation during autoimmune uveitis is the induction of MHC II molecules expression at their surface. IFNγ is regarded as the main cytokine involved in this induction. As TNFα plays a central role in autoimmune uveitis, we investigated its effects on IFNγ-mediated MHC II induction on RPE cells.

METHODS

Retinal pigment epithelium cells (ARPE-19) were stimulated with IFNγ, TNFα and the anti-TNFα antibody infliximab. The expression of MHCII and ICAM-1 was analysed by flow cytometry. The activation and expression of IRF-1 and STAT-1, two proteins involved in IFNγ-signalling pathway, were analysed by WB. Class II transactivator (CIITA) expression was monitored by qRT-PCR and immunoprecipitation.

RESULTS

TNFα inhibits IFNγ-induced MHC II expression on ARPE cells in a dose-dependent manner. Infliximab completely reverses the inhibitory effect of TNFα. We did not observe an inhibitory effect of TNFα on the expression of ICAM-1 induced by IFNγ. Similarly, IFNγ-induced STAT1 phosphorylation and IRF1 expression were not affected by TNFα. On the contrary, we found that TNFα suppresses IFNγ-induced CIITA mRNA accumulation and protein expression.

CONCLUSION

TNFα inhibits IFNγ-induced MHC II expression in RPE cells. This inhibitory effect was reversed by infliximab and was not because of a global inhibition of IFNγ -mediated RPE cell activation but rather to a specific down-regulation of CIITA expression. Those findings are consistent with the role of TNFα in the resolution of inflammation and might help to elucidate the complex development of autoimmune uveitis.

Review and update of intraocular therapy in noninfectious uveitis

PURPOSE OF REVIEW

To review new clinically relevant data regarding the intraocular treatment of noninfectious uveitis.

RECENT FINDINGS

Triamcinolone acetonide, the most commonly used intravitreal corticosteroid for treatment of uveitis and uveitic macular oedema has a limited duration of action and is associated with a high risk of corticosteroid-induced intraocular pressure (IOP) rise and cataract. Recent advances have led to the development of sustained-release corticosteroid devices using different corticosteroids such as dexamethasone and fluocinolone acetonide. Treatment options for patients who have previously exhibited corticosteroid hypertensive response have also expanded through the use of new noncorticosteroid intravitreal therapeutics such as methotrexate and antivascular endothelial growth factor (anti-VEGF) agents.

SUMMARY

Ozurdex dexamethasone implant appears to have a better safety profile, and a slightly long-lasting effect than triamcinolone acetonide. The Retisert implant allows the release of corticosteroids at a constant rate for 2.5 years, but it requires surgical placement and its use is associated with a very high risk of cataract and requirement for IOP-lowering surgery. For patients who are steroid responders, methotrexate may offer a better alternative to corticosteroid treatment than anti-VEGF agents, but controlled trials are required to confirm this.

Current concepts and future directions in the pathogenesis and treatment of non-infectious intraocular inflammation

The blockbuster drug paradigm is under increasing scrutiny across the biopharmaceutical industry. Intraocular inflammation poses particular challenges to this, given the heterogeneity of conditions in the uveitis spectrum, and the increasing acknowledgement of individual patient and disease variance in underlying immune responses. This need has triggered a drive towards personalised and stratified medicine, supported and enabled as a result of continued development of both experimental models and molecular biological techniques and improved clinical classification. As such we have the ability now to systematically appraise at a genomic, transcriptomic, and proteomic level individual immunophenotype, and the promise that in the eye this can be augmented by in vivo immune imaging to identify individual immunopathology. With such advances all running in parallel, we are entering an era of experimental medicine that will facilitate early diagnosis, generate biomarkers for accurate prognostication, and enable the development of individualised and targeted therapies, which can progress rapidly into clinical practice.

Intraocular interleukin-17 and proinflammatory cytokines in HLA-A29-associated birdshot chorioretinopathy

PURPOSE

To determine the levels of 23 immune mediators in paired aqueous humor (AqH) and serum samples from patients with birdshot chorioretinopathy (BSCR).

DESIGN

Single-centre case-control study.

METHODS

A multiplex immunoassay was used to determine the levels of 23 immune mediators (T-cell, proinflammatory, and vascular-active mediators) in paired AqH and serum of 16 BSCR patients. The AqH of 11 age-related cataract controls served as controls.

RESULTS

AqH levels of the T-cell mediators interleukin (IL)-2 (P=.044) and IL-17 (P=.039) and proinflammatory mediators IL-1β (P=.032), IL-6 (P=.034), and tumor necrosis factor α (P=.041) were elevated compared with that of age-related cataract controls. The elevated intraocular levels of IL-1β, IL-17, and tumor necrosis factor α in BSCR samples were higher than their concurrent serum levels. A significant positive correlation of intraocular mediators was noted between IL-17 and both IL-2 (r=0.744; P<.0001) and IL-23 (r=0.921; P<.0001) and between IL-2 and IL-23 (r=0.776; P<.0001). AqH levels of vascular-active mediators were not distinct between the groups.

CONCLUSIONS

BSCR patients have elevated intraocular levels of proinflammatory and T cell-associated cytokines. Our results suggest the novel pathogenic concept that BSCR is an autoimmune inflammatory disease restricted to the eye and associated with elevated IL-17.

An ENU-induced mutation in the Mertk gene (Mertknmf12) leads to a slow form of retinal degeneration

PURPOSE

To determine the basis and to characterize the phenotype of a chemically induced mutation in a mouse model of retinal degeneration.

METHODS

Screening by indirect ophthalmoscopy identified a line of N-ethyl-N-nitrosourea (ENU) mutagenized mice demonstrating retinal patches. Longitudinal studies of retinal histologic sections showed photoreceptors in the peripheral retina undergoing slow, progressive degeneration. The mutation was named neuroscience mutagenesis facility 12 (nmf12), and mapping localized the critical region to Chromosome 2.

RESULTS

Sequencing of nmf12 DNA revealed a point mutation in the c-mer tyrosine kinase gene, designated Mertk(nmf12). We detected elevated levels of tumor necrosis factor (Tnf, previously Tnfa) in retinas of Mertk(nmf12) homozygotes relative to wild-type controls and investigated whether the increase of TNF, an inflammatory cytokine produced by macrophages/monocytes that signals intracellularly to cause necrosis or apoptosis, could underlie the retinal degeneration observed in Mertk(nmf12) homozygotes. Mertk(nmf12) homozygous mice were mated to mice lacking the entire Tnf gene and partial coding sequences of the Lta (Tnfb) and Ltb (Tnfc) genes.(2) B6.129P2-Ltb/Tnf/Lta(tm1Dvk)/J homozygotes did not exhibit a retinal degeneration phenotype and will, hereafter, be referred to as Tnfabc(-/-) mice. Surprisingly, mice homozygous for both the Mertk(nmf12) and the Ltb/Tnf/Lta(tm1Dvk) allele (Tnfabc(-/-)) demonstrated an increase in the rate of retinal degeneration.

CONCLUSIONS

These findings illustrate that a mutation in the Mertk gene leads to a significantly slower progressive retinal degeneration compared with other alleles of Mertk. These results demonstrate that TNF family members play a role in protecting photoreceptors of Mertk(nmf12) homozygotes from cell death.

Tumor necrosis factor inhibitors in the management of juvenile idiopathic arthritis: an evidence-based review

Juvenile idiopathic arthritis (JIA) is a chronic inflammatory disorder of unknown origin that is often treated with a variety of disease-modifying agents. Tumor necrosis factor (TNF) inhibitors are a group of genetically engineered biologic agents that target the proinflammatory cytokine TNF. This review focuses on the use of TNF inhibitors in JIA. Etanercept was the first TNF inhibitor approved for use in children with moderate to severe polyarticular-course JIA following encouraging results from a randomized, double-blind, placebo-controlled, multicenter trial in children. Open-label extension studies of the original trial involving 8 years of follow-up demonstrated the long-term safety and efficacy of etanercept in children. Other studies from established registries also corroborate the safety of etanercept in JIA. The second TNF inhibitor to be approved for use in JIA is adalimumab following recent favorable results from another randomized, placebo-controlled, multicenter study in polyarticular-course JIA. While infliximab is not approved by the US FDA for use in JIA, it is frequently used in clinical practice for this indication. However, because the chimeric structure of infliximab incorporates murine components, it has the potential for allergic and infusion reactions. Patient responses to individual TNF inhibitors may vary depending on concomitant medications such as methotrexate, and also on the category of JIA.

Scleral thickness following fluocinolone acetonide implant (Retisert)

PURPOSE

To evaluate whether intravitreal fluocinolone acetonide (FA) implantation (Retisert) leads to scleral thinning.

METHODS

Scleral thickness was measured at the pars plana region (4 quadrants) with anterior segment OCT (Visante) in FA implanted eyes (18) with noninfectious posterior uveitis in comparison to eyes with prior vitrectomy (8), and normal eyes without prior surgery (30).

RESULTS

Mean scleral thickness in normal (nonsurgical) eyes was 0.99/0.93/0.88/0.86, and 0.92 mm in the inferonasal/inferotemporal/superotemporal/superonasal quadrants, and overall, respectively. Sclera was thinner in each quadrant of the FA implanted eyes compared to the fellow or nonsurgical eyes, although none reached statistical significance, as the differences were small. However, a few FA implanted eyes demonstrated more dramatic scleral thinning than others.

CONCLUSIONS

FA implant appears to lead to statistically nonsignificant scleral thinning overall with few exceptions. Clinicians should be aware of potential scleral thinning in select cases, important for reimplantation and long-term follow-up.

Orbital lobular panniculitis in Weber-Christian disease: sustained response to anti-TNF treatment and review of the literature

Weber-Christian disease is a febrile, relapsing, non-suppurative panniculitis of unknown etiology. Lobular panniculitis is the essential feature in biopsy specimens and evolves through three recognizable stages. We report a case of Weber-Christian disease with bilateral orbital involvement, at different stages, affecting the orbital fat along with enophthalmos in one orbit, and the upper preaponeurotic fat pad in the other. Weber-Christian disease was refractory to treatment with conventional immunosuppressive regimens; however, early inflammatory-but not chronic fibrotic-orbital lesions responded dramatically to anti-tumor necrosis factor (TNF) therapy. A literature review revealed five additional cases of orbital Weber-Christian disease, none treated with anti-TNF antibodies. Of these, four presented initially with proptosis, representing early stages of inflammation, and two subsequently developed enophthalmos, representing late, inactive stage of the disease. Although orbital Weber-Christian disease is rare, ophthalmologists need to be aware of this entity. Depending on the stage of inflammation, Weber-Christian disease should be included in the differential diagnosis of both proptosis and enophthalmos. Anti-TNF antibodies can successfully treat patients at the early inflammatory stage.

Tumor necrosis factor-α-mediated severity of idiopathic retinal periphlebitis in young adults (Eales' disease): implication for anti-TNF-α therapy

Tumor necrosis factor-alpha (TNF-α) is a pleiotropic inflammatory cytokine. Tumor necrosis factor-alpha was evaluated in the serum samples of patients with idiopathic retinal periphlebitis in young adults (Eales' disease). Retinal periphlebitis was graded according to a new grading system based on severity of inflammation (grade 1-4). Quantification of the TNF-α levels was carried out using ELISA kit in the serum samples of young adults with idiopathic retinal periphlebitis (n = 17) and healthy controls (n = 17) of similar age. Tumor necrosis factor-α level was found to be significantly raised in cases with retinal periphlebitis as compared with controls (p < 0.001). Higher levels of TNF-α were found to be associated with increased severity of retinal periphlebitis. Tumor necrosis factor-α represents a novel target for controlling inflammatory activity in idiopathic retinal periphlebitis. Higher levels of TNF-α, in association with the increased severity of retinal periphlebitis, have implications for early anti-TNF-α therapy.

Infliximab for diabetic macular edema refractory to laser photocoagulation: a randomized, double-blind, placebo-controlled, crossover, 32-week study

OBJECTIVE

Because many patients with diabetic macular edema (DME) do not respond to focal/grid laser photocoagulation, the only currently approved treatment, alternatives are needed. Based on encouraging preliminary findings, we aimed to assess efficacy and safety of the anti-tumor necrosis factor (TNF) monoclonal antibody infliximab in this condition.

RESEARCH DESIGN AND METHODS

This was a single-center, double-blind, randomized, placebo-controlled, crossover study. Eleven patients with sight-threatening DME persisting after two sessions of laser photocoagulation received infliximab (5 mg/kg) intravenously at weeks 0, 2, 6, and 14, followed by placebo at weeks 16, 18, 22, and 30, or vice versa. Blinding was maintained to week 32, when the final assessments were performed. Best corrected visual acuity evaluated by a mixed-models approach for imbalanced crossover design using the percentage difference as the outcome variable was the primary study end point. Data were analyzed on an intention-to-treat basis.

RESULTS

Early Treatment of Diabetic Retinopathy Study (ETDRS) scores dropped from 31.6 +/- 5.1 (mean +/- SD) letters read at baseline to 28.8 +/- 11.6 letters read at week 16 in six placebo-treated eyes and improved to 35.4 +/- 11.2 letters read after infliximab. In contrast, visual acuity improved from 23.5 +/- 10.3 at baseline to 30.4 +/- 13.4 letters read at week 16 in eight infliximab-treated eyes and was sustained at completion of placebo treatment (31.4 +/- 12.1 letters read). The excess visual acuity in infliximab-treated eyes was greater by 24.3% compared with that in placebo-treated eyes (95% CI 4.8-43.7; P = 0.017). Infliximab treatment was well tolerated.

CONCLUSIONS

The positive results of this small phase III study suggest that larger and longer term trials should be conducted to assess the efficacy of systemic or intravitreal anti-TNF agent administration for primary treatment of DME.

Protein delivery for retinal diseases: from basic considerations to clinical applications

Because the eye is protected by ocular barriers but is also easily accessible, direct intravitreous injections of therapeutic proteins allow for specific and targeted treatment of retinal diseases. Low doses of proteins are required in this confined environment and a long time of residency in the vitreous is expected, making the eye the ideal organ for local proteic therapies. Monthly intravitreous injection of Ranibizumab, an anti-VEGF Fab has become the standard of care for patients presenting wet AMD. It has brought the proof of concept that administering proteins into the physiologically low proteic concentration vitreous can be performed safely. Other antibodies, Fab, peptides and growth factors have been shown to exert beneficial effects on animal models when administered within the therapeutic and safe window. To extend the use of such biomolecules in the ophthalmology practice, optimization of treatment regimens and efficacy is required. Basic knowledge remains to be increased on how different proteins/peptides penetrate into the eye and the ocular tissues, distribute in the vitreous, penetrate into the retinal layers and/or cells, are eliminated from the eye or metabolized. This should serve as a basis for designing novel drug delivery systems. The later should be non-or minimally invasive and should allow for a controlled, scalable and sustained release of the therapeutic proteins in the ocular media. This paper reviews the actual knowledge regarding protein delivery for eye diseases and describes novel non-viral gene therapy technologies particularly adapted for this purpose.

Tumor necrosis factor-alpha converting enzyme: Implications for ocular inflammatory diseases

Tumor necrosis factor-alpha (TNF-alpha) converting enzyme (TACE), a member of the family of metalloproteinase disintegrin proteins, is responsible for the conversion of inactive TNF-alpha precursor form to active mature form. TNF-alpha is a pleiotropic cytokine that contributes to cellular immunity and inflammatory response in wide range of inflammatory pathologies. Although a large number of studies indicate the use of TACE inhibitors, which prevents processing of TNF-alpha as potential therapeutic drugs for the treatment of inflammatory diseases including rheumatoid arthritis, Crohn's disease and cancer, very few studies indicate its use in ocular pathologies. It is still not clearly understood how the TACE-mediated shedding of cytokines and growth factors in various ocular tissues plays a critical role in the cytotoxic signals causing tissue dysfunction and damage leading to blindness. Regulation of TACE activity is likely to have wide implications for ocular immunology and inflammatory diseases. Specifically, since anti-TNF-alpha therapies have been used to prevent ocular inflammatory complications, the use of TACE inhibitors could be a novel therapeutic approach for ocular inflammatory diseases especially uveitis.

Infliximab for the treatment of refractory scleritis

Background

Scleritis is a potentially blinding inflammatory disorder. Standard care consists of systemic corticosteroids and immunosuppresants. The authors describe a series of 10 patients suffering from scleritis treated with the TNF inhibitor infliximab because this scleritis was refractory to standard therapy.

Methods

The authors reviewed the medical records of patients with scleritis at the Massachusetts Eye Research and Surgery Institution, treated with infliximab. All cases had non-infectious scleritis refractory to traditional immunomodulatory therapy and received 5 mg/kg of infliximab at 4–8-weekly intervals. The main outcome measures evaluated were clinical response, reduction in concomitant immunomodulatory therapy and adverse effects. Inflammation control and visual acuity were assessed using life-table methods.

Results

A favourable clinical response to infliximab was seen in 100% of the patients, with six (60%) of them achieving remission and cessation of concomitant immunosuppression. A clinical response to infliximab therapy occurred within 13.24 weeks on average. Based on clinical response, the authors found that repeat monthly infusions were required to maintain remission. One (10%) patient developed a lupus-like reaction necessitating discontinuation of infliximab.

Conclusion

Infliximab may be considered in the treatment of non-infectious scleritis refractory to other treatment.

Intravitreal infliximab in experimental endotoxin-induced uveitis

PURPOSE

Tumor necrosis factor-alpha (TNF-alpha) plays a central role in the pathogenesis of ocular inflammation and the level of TNF-alpha is increased in ocular fluids of patients with uveitis. Intravenous infliximab, a monoclonal antibody against TNF-alpha, has been used for the treatment of uveitis with promising preliminary results. The aim of this study was to evaluate the effect of intravitreal injection of infliximab on experimental uveitis.

METHODS

Thirty-three white New Zealand rabbits were divided randomly into three groups. Group 1 (n=5) received intravitreal injection of 1 mg/0.1 cc infliximab plus 0.1 cc normal saline, group 2 (n=14) received intravitreal injection of 2 microg Salmonella typhimurium endotoxin plus 1 mg/0.1 cc infliximab, and group 3 (n=14) animals received intravitreal endotoxin 2 microg/0.1 cc plus normal saline 0.1 cc. Inflammation was evaluated by clinical examinations on days 1, 3, 5, and 7 after the injections; measuring the protein concentration and inflammatory cell content of the aqueous humor; and histopathologic examination.

RESULTS

No inflammation occurred in group 1 animals. There was a statistically significant difference between group 2 and 3 animals with regard to clinical examination on the third, fifth, and seventh postinjection days. The differences between groups 2 and 3 were significant with regard to aqueous cell counts and protein content at day 7 (p=0.02 and p=0.001, respectively). Histopathologic examination results showed less inflammation in group 2 animals compared to group 3 animals (p=0.009).

CONCLUSIONS

The results provide evidence that intravitreal injection of infliximab suppresses ocular inflammation in a rabbit model of severe endotoxin-induced uveitis.

Intravitreal administration of the anti-tumor necrosis factor agent infliximab for neovascular age-related macular degeneration

PURPOSE

To present our preliminary experience on intravitreal administration of an anti-tumor necrosis factor (TNF) monoclonal antibody for neovascular age-related macular degeneration (AMD).

DESIGN

Prospective, noncomparative series of 3 patients previously treated with an anti-vascular endothelial growth factor agent.

METHODS

Two intravitreal injections of 0.05 ml containing infliximab were administered in the first (1 and 2 mg, 2 months apart), second (2 mg each, 2 months apart), and third patient (2 mg each, 3 months apart). Best-corrected visual acuity (BCVA) and central foveal thickness (CFT) were monthly assessed for up to 7 months.

RESULTS

In the first patient, BCVA increased from 20/200 to 20/100 and CFT decreased from 462 to 386 microm, 2 months after the first injection. The condition was further improved after the second injection (BCVA, 20/40; CFT, 210 microm), but recurrence occurred 7 months post-baseline. In the second patient, BCVA increased from 20/200 to 20/70 and CFT decreased from 512 to 420 and 184 microm, 2 and 4 months post-baseline, respectively. In the third patient, clinical improvement was documented after the first injection. A second injection attributable to recurrence resulted in improvement of BCVA from 20/100 to 20/30 and decrease of CFT from 388 to 282 microm, 2 months after the second injection.

CONCLUSIONS

These findings, although insufficient to consider "off-label" treatment with intravitreal infliximab, provide in vivo evidence of a pathogenetic link of locally produced and/or acting TNF to neovascular AMD. A randomized study of consecutive intravitreal injections of infliximab for AMD may be warranted.

Treatment strategies for Behçet's disease

BACKGROUND

Behçet's disease (BD) is a multisytemic vasculitis characterized by oral and genital ulceration, other skin lesions, uveitis and manifestations affecting the blood vessels, CNS and gastrointestinal system. It is rare in the Western world but is frequent in the Middle and Far East.

OBJECTIVE

The aim of this review is to discuss treatment strategies in BD. These might vary between simple reassurance and a combination of immunosuppressives.

METHODS

A systematic literature search was done using the Cochrane and Medline databases in June 2008. The EULAR recommendations for the management of BD were also taken into account.

CONCLUSION

The last two decades have witnessed considerable improvement in eye disease and musculoskeletal involvement. However, the treatment of thrombophlebitis, CNS, and gastrointestinal manifestations remains problematic.

Viral TNF inhibitors as potential therapeutics

The immune system functions by maintaining a delicate balance between the activities of pro-inflammatory and anti-inflammatory pathways. Unbalanced activation of these pathways often leads to the development of serious inflammatory diseases. TNF (Tumor Necrosis Factor) is a key pro-inflammatory cytokine, which can cause several inflammatory diseases when inappropriately up-regulated. Inhibition of TNF activities by using modulatory recombinant proteins has become a successful therapeutic approach to control TNF activity levels but these anti-TNF reagents also have risks and certain limitations. Biological molecules with a different mode of action in regulating TNF biology might provide a clinically useful alternative to the current therapeutics or in some cases might be efficacious in combination with existinganti-TNF therapies. TNF is also a powerful host defense cytokine commonly induced in the host response against various invading pathogens. Many viral pathogens can block TNF function by encoding modulators of TNF, its receptors or downstream signaling pathways. Here, we review the known virus-encoded TNF inhibitors and evaluate their potential as alternative future anti-TNF therapies.

Mediation of cannabidiol anti-inflammation in the retina by equilibrative nucleoside transporter and A2A adenosine receptor

PURPOSE

Cannabidiol (CBD), a nonpsychotropic, nontoxic compound has been shown to block diabetes- and endotoxin-induced retinal damage. However, the protective mechanism of this anti-inflammatory cannabinoid is not completely understood. The goal of this study is to determine the role of adenosine signaling in retinal inflammation and its potential modulation by CBD.

METHODS

The adenosine receptor (AR) subtypes expressed in rat retinal microglial cells were assessed by quantitative real-time RT-PCR. AR function was determined via in vitro and in vivo inflammatory models. Microglial cells or rats were treated with or without lipopolysaccharide (LPS) in the presence or absence of adenosine, adenosine receptor agonists/antagonists, or CBD. Adenosine uptake and tumor necrosis factor (TNF)-alpha release in cells or in retinas were determined.

RESULTS

The results showed that A(2A)ARs are abundantly expressed in rat retinal microglial cells. When the cells or rats were treated with LPS, activation of the A(2A)AR was the most efficient in mediating AR agonist- or CBD-induced TNF-alpha inhibition. CBD inhibited adenosine uptake via equilibrative nucleoside transporter 1 and synergistically enhanced adenosine's TNF-alpha suppression after treatment with LPS.

CONCLUSIONS

These results suggest that the activated A(2A)AR in the retinal microglial cells plays a major anti-inflammatory role in the retina and that CBD's anti-inflammatory effects are linked to the inhibition of adenosine uptake.

Intravitreal administration of the anti-TNF monoclonal antibody infliximab in the rabbit

BACKGROUND

Tumor necrosis factor (TNF) is known to play an important role in various immune-mediated ocular diseases; intravenous administration of the anti-TNF monoclonal antibody infliximab has proved beneficial in such cases. Since intravitreal injection (when available) is a substitute for systemic administration of various drugs targeting the eye, we aimed to evaluate the safety of intravitreal injection of infliximab in the rabbit eye.

METHODS

Seven groups of New Zealand white rabbits (four animals in each group) received a single unilateral intravitreal injection (0.1 ml) of increasing doses of infliximab (namely 1, 2, 5, 8, 10 or 20 mg infliximab [Remicade]) or a sham injection respectively. Slit-lamp biomicroscopy, fundoscopy and electrophysiology recordings, i.e. scotopic, photopic and flicker responses, were performed at baseline and after 1, 5, 10, 15, 30 and 45 days. Infliximab-injected eyes were compared with sham-injected and with uninjected fellow eyes (n = 28). Animals were euthanized on day 45 for histopathological examination of the retinas.

RESULTS

Clinical examination and electrophysiological testing were consistently unremarkable after either sham or 1 mg or 2 mg infliximab injections. In contrast, electrophysiological recordings were significantly reduced in a dose-dependent manner from day 1 through day 45, after 5, 8, 10 and 20 mg infliximab injections. Flicker responses were the most sensitive in detecting the lower toxic dose of 5 mg. Histopathological findings were similar in uninjected and sham-injected eyes, as well as after 1 mg or 2 mg infliximab injections. Consistent with the functional abnormalities, retinal deformities and diffuse edema were observed after injection of 5 mg or higher doses of infliximab.

CONCLUSIONS

Intravitreal infliximab may be safely administered up to a dose of 2 mg in the rabbit eye. Such doses can be used in the design of future clinical trials assessing the effects of infliximab for selected patients with immune-mediated ocular conditions.

Regression of vasoproliferative tumor with systemic infliximab

The anti-tumor necrosis factor (TNF) monoclonal antibody infliximab inhibits the pleiotropic actions of TNF and is widely used for the treatment of inflammatory diseases, such as uveitis. A pathogenetic role of TNF in ocular inflammatory conditions has recently emerged. The authors describe a patient with collagen mixed disease who had decreased vision in the left eye. Fundus examination disclosed bilateral peripheral vasoproliferative tumors and macular edema in the left eye. The patient underwent treatment with infliximab intravenously for his systemic condition. Regression of the vasoproliferative tumors in both eyes and improvement of macular edema in the left eye was observed. Although the data are limited, anti-TNF antibodies such as infliximab may be useful in the treatment of retinal vascular tumors.