The Th1/Th2 paradigm in ocular allergy

Conjunctival infiltrates and cytokines in an experimental immune-mediated blepharoconjunctivitis rat model

Purpose

To characterize the histopathological and immunological findings of a rat model of allergic blepharoconjunctivitis (BC) and demonstrate its potential utility for the assessment of BC therapies.

Methods

Sprague-Dawley (SD) rats were immunized with ovalbumin (OVA) and topically challenged with OVA (BC group) or PBS (control group), while a corticosteroid group was pre-treated with triamcinolone acetate 24 h before the challenge. Morphological features were evaluated and tissues were harvested for histological, flow cytometry and cytokine analysis.

Results

The BC group rats developed eyelid excoriations, redness, and conjunctival edema 24 h after the OVA challenge, while corticosteroid pre-treated and PBS-challenged rats were unaffected. The BC features were reduced despite repeated challenges for 5 days. Massive immune cell infiltration was observed in conjunctivae of BC rats, while no significant infiltration was seen in the other groups. Populations of T cells, mono-macrophages, neutrophils, and NK cells made up more than 77% of CD45⁺7AAD^- cells in the conjunctival tissues. T cell proportions were increased at 96 h compared to 24 h post-challenge, while macrophages decreased during the same time period. Eosinophils and intraepithelial neutrophils were detected in the BC rats, but not in the PBS and corticosteroid groups. BC eyes had significantly higher levels of IFN-γ and IL-2, while IL-4 and IL-6 levels were similar to controls.

Conclusion

A robust BC response was detected in this rat model which was suppressed by corticosteroid pre-treatment. Immune cell composition and cytokine profiles changed over time.

An ocular Th1 immune response promotes corneal nerve damage independently of the development of corneal epitheliopathy

Proper sight is not possible without a smooth, transparent cornea, which is highly exposed to environmental threats. The abundant corneal nerves are interspersed with epithelial cells in the anterior corneal surface and are instrumental to corneal integrity and immunoregulation. Conversely, corneal neuropathy is commonly observed in some immune-mediated corneal disorders but not in others, and its pathogenesis is poorly understood. Here we hypothesized that the type of adaptive immune response may influence the development of corneal neuropathy. To test this, we first immunized OT-II mice with different adjuvants that favor T helper (Th)1 or Th2 responses. Both Th1-skewed mice (measured by interferon-γ production) and Th2-skewed (measured by interleukin-4 production) developed comparable ocular surface inflammation and conjunctival CD4+ T cell recruitment but no appreciable corneal epithelial changes upon repeated local antigenic challenge. Th1-skewed mice showed decreased corneal mechanical sensitivity and altered corneal nerve morphology (signs of corneal neuropathy) upon antigenic challenge. However, Th2-skewed mice also developed milder corneal neuropathy immediately after immunization and independently of ocular challenge, suggestive of adjuvant-induced neurotoxicity. All these findings were confirmed in wild-type mice. To circumvent unwanted neurotoxicity, CD4+ T cells from immunized mice were adoptively transferred to T cell-deficient mice. In this setup, only Th1-transferred mice developed corneal neuropathy upon antigenic challenge. To further delineate the contribution of each profile, CD4+ T cells were polarized in vitro to either Th1, Th2, or Th17 cells and transferred to T cell-deficient mice. Upon local antigenic challenge, all groups had commensurate conjunctival CD4+ T cell recruitment and macroscopic ocular inflammation. However, none of the groups developed corneal epithelial changes and only Th1-transferred mice showed signs of corneal neuropathy. Altogether, the data show that corneal nerves, as opposed to corneal epithelial cells, are sensitive to immune-driven damage mediated by Th1 CD4+ T cells in the absence of other pathogenic factors. These findings have potential therapeutic implications for ocular surface disorders.

Biologics for allergy: therapeutic potential for ocular allergic diseases and adverse effects on the eye

Biologics applying antibodies against IgE, IL-5, IL-5 receptor α, IL-4 receptor α, and IL-13 have dramatically improved recent treatment outcomes in allergic diseases including asthma, rhinitis, and atopic dermatitis. However, these drugs have not been approved for ocular allergic diseases such as allergic conjunctivitis, vernal keratoconjunctivitis, and atopic keratoconjunctivitis. Although the putative mechanisms suggest that these drugs should have beneficial effects in patients with ocular allergies and some studies have reported such beneficial effects, various adverse ocular symptoms have also been observed in clinical trials and off-label use studies. Since ocular allergic diseases have distinct pathogeneses, each biologic drug must be examined regarding specific effects on each ocular allergy. For example, IgE-mediated type 1 hypersensitivity plays a critical role in allergic conjunctivitis. By contrast, T cells and eosinophilic and non-IgE-mediated type 2 inflammation play important roles in vernal keratoconjunctivitis. Allergists must fully understand the effects of each drug on the eye. This review outlines both potential therapeutic and adverse effects of various biologics on allergic diseases of the eye.

The role of ICOS in allergic disease: Positive or Negative?

With the rapid increase in the incidence of allergic diseases, the mechanisms underlying the development of these diseases have received a great deal of attention, and this is particularly true in regard to the role of ICOS in allergic diseases. Current studies have revealed that ICOS affects the functional activity of multiple immune cells that modulate the adaptive immune system. Additionally, ICOS also plays a crucial role in mediating cellular immunity and coordinating the response of the entire immune system, and thus, it plays a role in allergic reactions. However, the ICOS/ICOS-ligand (ICOS-L) axis functions in a dual role during the development of multiple allergic diseases. In this review, we explore the role of ICOS/ICOSL in the context of different immune cells that function in allergic diseases, and we summarize recent advances in their contribution to these diseases.

IL-33/ST2/IL-9/IL-9R signaling disrupts ocular surface barrier in allergic inflammation

This study was to explore a novel IL-33/ST2/IL-9/IL-9R signaling pathway that disrupts ocular surface barrier and amplifies allergic inflammation. Two murine models of experimental allergic conjunctivitis (EAC) and IL-9 topical challenge in wild type Balb/c and ST2^-/- mice, and two culture models of primarily human corneal epithelial cells (HCECs) and mouse CD4⁺ T cells were performed. Clinical manifestations, Oregon-Green Dextran (OGD) staining, the apical junction complexes (AJCs), IL-33/ST2 and IL-9/IL-9R signaling molecules were evaluated in ocular surface and its draining cervical lymph nodes (CLNs) by RT-qPCR, immunostaining and ELISA. The typical allergic signs, enhanced OGD staining intensity, disrupted morphology of AJCs, including ZO-1, claudin 1, occludin, and E-cadherin, and the stimulated signaling of IL-33/ST2 and IL-9/IL-9R were observed in ocular mucosa and draining CLNs in EAC-Balb/c mice, but significantly reduced or eliminated in EAC-ST2^-/- mice. Topical challenge of IL-9 resulted in the obvious OGD staining and disrupted ocular surface AJCs in Balb/c mice and in HCECs in vitro. IL-9 production was found to be stimulated by IL-33 in CD4⁺ cells from Balb/c mice in vitro. Our findings uncovered a novel phenomenon and mechanism by which ocular surface barrier integrity is disrupted in allergic conjunctivitis by IL-33/ST2/IL-9/IL-9R signaling pathway, which may amplify the allergic inflammation.

Qi-Wei-Du-Qi-Wan and its major constituents exert an anti-asthmatic effect by inhibiting mast cell degranulation

ETHNOPHARMACOLOGICAL RELEVANCE

In Asia, Qi-Wei-Du-Qi-Wan (QWDQW) is a traditional Chinese medicine that has been used to treat chest tightness, cough, shortness of breath, night sweats, frequent urination and asthma. QWDQW is recorded in Yi Zong Yi Ren Pian (Medical Physician's Compilation), which was written by Yang Cheng Liu during the Qing Dynasty.

AIM OF THE STUDY

The traditional Chinese medicine QWDQW is composed of 7 ingredients and has been used in the treatment of asthma in Asia for hundreds of years. However, the mechanism through which QWDQW affects the immune system in the treatment of asthma is not known. Therefore, this study aimed to investigate whether QWDQW alleviates asthmatic symptoms in mice with chronic asthma induced by repeated stimulation with Dermatophagoides pteronyssinus (Der p) and to explore the underlying immune modulatory mechanism.

MATERIALS AND METHODS

BALB/c mice were stimulated intratracheally (i.t.) with Der p (40 μl, 2.5 μg/μl) once weekly for 6 weeks. Thirty minutes prior to Der p stimulation, the mice were treated with QWDQW (0.5 g/kg and 0.17 g/kg) orally. Three days after the last stimulation, the mice were sacrificed, and infiltration of inflammatory cells, lung histological characteristics, gene expression of lung and serum total IgE were assessed. In other experiments, RBL-2H3 cells were stimulated with DNP-IgE/DNP-BSA and then treated with QWDQW, quercetin, β-carotene, luteolin or a mixture of the three chemicals (Mix13) for 30 min, and the effects of the drugs on RBL-2H3 cell degranulation after DNP stimulation were determined.

RESULTS

QWDQW significantly reduced Der p-induced airway hyperreactivity (AHR) and decreased total serum IgE and Der p-specific IgE levels. Histopathological examination showed that QWDQW reduced inflammatory cell infiltration and sputum secretion from goblet cells in the lungs. Gene expression analysis indicated that QWDQW reduced overproduction of IL-12、IFN-γ、IL-13、IL-4、RNATES、Eotaxin and MCP-1in lung. Additionally, QWDQW and Mix13 suppressed DNP induced RBL-2H3 degranulation, and the effect was maximal when quercetin, β-carotene and luteolin were administered together.

CONCLUSION

These results indicate that QWDQW plays a role in suppressing excessive airway reaction and in specific immune modulation in a mouse model of chronic asthma and that QWDQW suppresses mast cell degranulation at defined doses of quercetin, β-carotene and luteolin.

To See or Not to See: A Systematic Review of the Importance of Human Ocular Surface Cytokine Biosignatures in Ocular Allergy

Cytokines are key cell signalling proteins in a number of immune and homeostatic pathways of the human body. In particular, they mediate intracellular mechanisms of allergy on the ocular surface by triggering cellular responses that result in typical physiological ocular allergy symptoms, such as itchiness, watery eyes, irritation, and swelling. Given the recent research focus in optometry on the aetiology of corneal ectasia subtypes like keratoconus, there is an increasing need for the development of new clinical diagnostic methods. An increasing trend is evident among recent publications in cytokine studies, whereby the concentrations of cytokines in healthy and disease states are compared to derive a specific cytokine profile for that disease referred to as ‘biosignatures’. Biosignatures have diagnostic applications in ocular allergy as a cheap, non-invasive alternative to current techniques like IgE antibody testing and skin prick tests. Cytokine detection from tear samples collected via microcapillary flow can be analysed either by enzyme-linked immunosorbent assays (ELISA), multiplex magnetic bead assays, or immunoblot assays. Characterising patient hypersensitivities through diagnostic tests is the first step to managing exposure to triggers. Investigating cytokine biosignatures in ocular allergy and their links to physiology are imperative and will be the focus of this systematic review article.

Galectin-3: role in ocular allergy and potential as a predictive biomarker

Aims

To evaluate galectin-3 (Gal-3), a β-galactoside binding protein, as a possible biomarker in ocular allergy and further investigated the role of endogenous Gal-3 in a murine model of ovalbumin (OVA)-induced allergic conjunctivitis (AC).

Methods

Conjunctival impression cytology specimens from control and patients with severe vernal keratoconjunctivitis, treated or untreated, were used to evaluate Gal-3 expression by immunocytochemistry. To investigate the mechanism of action of Gal-3, OVA-immunised BALB/c male wild-type (WT) and Gal-3 null (Gal-3-/-) mice were challenged with eye drops containing OVA on days 14–16 with a subset of animals pretreated with 0.03% tacrolimus (TC) or dexamethasone (Dex).

Results

Patients with AC and OVA-sensitised WT mice exhibited increased levels of Gal-3 in the conjunctiva compared with control, an effect reverted by the action of Dex and TC therapy. Twenty-four hours after the final OVA challenge, total and anti-OVA IgE levels increased significantly in the blood of OVA-sensitised WT and Gal-3-/- mice compared with controls, supporting the efficacy of the AC model. The lack of endogenous Gal-3 exacerbated the local inflammatory response, increasing the influx of eosinophils and mast cell activation. Additionally, OVA-sensitised Gal-3-/- animals exhibited increased CD4+ expression in the eyes as well as eotaxin, IL-4, IL-13 and interferon-γ levels in the tear fluid compared with WT animals.

Conclusion

Gal-3 contributes to the pathogenesis of ocular allergy and represents a relevant therapeutic target.

Pollen/TLR4 Innate Immunity Signaling Initiates IL-33/ST2/Th2 Pathways in Allergic Inflammation

Innate immunity has been extended to respond environmental pathogen other than microbial components. Here we explore a novel pollen/TLR4 innate immunity in allergic inflammation. In experimental allergic conjunctivitis induced by short ragweed (SRW) pollen, typical allergic signs, stimulated IL-33/ST2 signaling and overproduced Th2 cytokine were observed in ocular surface, cervical lymph nodes and isolated CD4⁺ T cells of BALB/c mice. These clinical, cellular and molecular changes were significantly reduced/eliminated in TLR4 deficient (Tlr4-d) or MyD88 knockout (MyD88^−/−) mice. Aqueous SRW extract (SRWe) directly stimulated IL-33 mRNA and protein expression by corneal epithelium and conjunctiva in wild type, but not in Tlr4-d or MyD88^−/− mice with topical challenge. Furthermore, SRWe-stimulated IL-33 production was blocked by TLR4 antibody and NF-kB inhibitor in mouse and human corneal epithelial cells. These findings for the first time uncovered a novel mechanism by which SRW pollen initiates TLR4-dependent IL-33/ST2 signaling that triggers Th2-dominant allergic inflammation.

Beneficial effect of annexin A1 in a model of experimental allergic conjunctivitis

Annexin A1 (ANXA1), a 37 kDa glucocorticoid-regulated protein, is a potent anti-inflammatory mediator effective in terminating acute inflammatory response, and its role in allergic settings has been poorly studied. The aim of this investigation was to evaluate the mechanism of action of ANXA1 in intraocular inflammation using a classical model of ovalbumin (OVA)-induced allergic conjunctivitis (AC). OVA-immunised Balb/c mice, wild-type (WT) and ANXA1-deficient (AnxA1(-/-)), were challenged with eye drops containing OVA on days 14-16 with a subset of WT animals pretreated intraperitoneally with the peptide Ac2-26 (N-terminal region of ANXA1) or dexamethasone (DEX). After 24 h of the last ocular challenge, WT mice treated with Ac2-26 and DEX had significantly reduced clinical signs of conjunctivitis (chemosis, conjunctival hyperaemia, lid oedema and tearing), plasma IgE levels, leukocyte (eosinophil and neutrophil) influx and mast cell degranulation in the conjunctiva compared to WT controls. These anti-inflammatory effects of DEX were associated with high endogenous levels of ANXA1 in the ocular tissues as detected by immunohistochemistry. Additionally, Ac2-26 administration was effective to reduce IL-2, IL-4, IL-10, IL-13, eotaxin and RANTES in the eye and lymph nodes compared to untreated WT animals. The lack of ANXA1 produced an exacerbated allergic response as detected by the density of the inflammatory cell influx to the conjunctiva and the cytokine/chemokine release. These different effects observed for Ac2-26 were correlated with diminished level of activated ERK at 24 h in the ocular tissues compared to untreated OVA group. Our findings demonstrate the protective effect of ANXA1 during the inflammatory allergic response suggesting this protein as a potential target for new ocular inflammation therapies.

Cellular changes in tears associated with keratoconjunctival responses induced by nasal allergy

BACKGROUND

Allergic keratoconjunctivitis occurs in a primary form, caused by an allergic reaction localized in the conjunctiva, and in a secondary form, induced by an allergic reaction originating in the nasal mucosa. Various hypersensitivity mechanisms involved in the keratoconjunctivitis forms result in different keratoconjunctival response types.

PURPOSE

To investigate the cytologic changes in tears during the secondary immediate (SIKCR), late (SLKCR), and delayed (SDYKCR) keratoconjunctival responses.

METHODS

In 61 patients, comprising 20 SIKCRs, 23 SLKCRs, and 18 SDYKCRs, nasal provocation tests (NPTs) with allergens and 61 phosphate-buffered control challenges were repeated and supplemented with cell counting in the tears.

RESULTS

The SIKCR (P<0.01), appearing 10-120 min after the NPT, was associated with increased eosinophil and mast cell counts in tears. The SLKCR (P<0.01), appearing 5-12 h after the NPT, was accompanied by increased counts of eosinophils, neutrophils, basophils, and conjunctival epithelial and goblet cells. The SDYKCR (P<0.05), appearing 24-48 h after NPT, was associated with increased counts of lymphocytes, neutrophils, monocytes, basophils, conjunctival epithelial, corneal epithelial and goblet cells.

CONCLUSIONS

The SIKCR, SLKCR, and SDYKCR, induced by nasal allergy, were associated with different cellular profiles in the tears. The cells, except mast, epithelial and goblet cells, displaying no intracellular changes, migrated probably from the conjunctival capillaries, in response to the factors released during the primary allergic reaction in the nasal mucosa and subsequently penetrating into the conjunctiva. These results demonstrate a causal role of nasal allergy and diagnostic value of NPT combined with recording of ocular features and cellular profiles in tears in some keratoconjunctivitis patients.

Oral Administration of MBG to Modulate Immune Responses and Suppress OVA-Sensitized Allergy in a Murine Model

Recently studies performed on mushroom isolated polysaccharides demonstrated that β -(1,3)-glucan may affect the balance of Th1/Th2 cell response. Using ovalbumin (OVA) as a hypersensitivity inducer, we evaluated the ability of mushroom beta-glucan (MBG) in modulating Th1/Th2 cell responses in B6 mice. As compared to the control group, administration of MBG resulted in an increase of phagocytic activities, Th1 cytokine productions, immunoglobulins including IgG2A and IgA, and a significant expression of the splenic surface markers including CD3, CD4, CD8, and F4/80. In contrast, administration of MBG has significantly suppressed IgE and IgG1 levels and Th2 cytokines including IL-4, IL-5, and IL-6. Histopathological observation of MBG-treated followed by OVA-treated mice showed less filtration of eosinophil in pulmonary tissue sections. Our data suggested that administration of MBG treatments alters the natural course of the IgE-mediated hypersensitivities. In this investigation, we realize the mushroom beta glucan alter the Th2 response toward the Th1 in the allergic, resulting in a reduction in IgE productions which played a substantive role in reducing the severity of IgE-mediated hypersensitivity.

Expression of recombinant human IL-4 in Pichia pastoris and relationship between its glycosylation and biological activity

Secretory human interleukin 4 (hIL4) is an N-glycosylated pleiotropic cytokine. It is unknown if these N-linked glycans are required and essential for hIL4 protein stability, expression, secretion, and activity in vivo, and hIL4 expressed from Pichia pastoris yeast has not been tested to date. In this study, we successfully expressed human hIL4 in P. pastoris, the methylotrophic yeast, with a yield of 15.0mg/L. Using the site-directed mutagenesis technique, we made two mutant hIL4 cDNA clones (N38A and N105L) and subsequently expressed them in P. pastoris to analyze the relevant function of each N-glycosylation site on hIL4. Our results demonstrate that the glycosylation only occurs at position Asn38, but not Asn105. The glycosylated form of hIL4 unexpectedly has lower biological activity and lower stability when compared to its non-glycosylated form. The implications of this are discussed.

The chemokine receptor CCR7 expressed by dendritic cells: a key player in corneal and ocular surface inflammation

Dendritic cells (DCs) are highly potent stimulators of the immune system, and their contribution as such to the pathogenesis of corneal and ocular surface inflammatory disease has been well established. These vigorous antigen-presenting cells are reliant upon their effective migration from peripheral tissues (e.g., those of the ocular surface) to the lymphoid organs, where immune responses are triggered and can then cause disease. The chemokine receptor CCR7 expressed on DCs has emerged as the master mediator of this highly complex migratory process, and thus it is important in causing corneal and ocular surface inflammation. Furthermore, CCR7 has received considerable attention as a potential therapeutic target, as topically instilled antagonists of this receptor are quite effective therapeutically in a mouse model of ocular allergy. These findings and more are reviewed in the current article. In addition, the understanding regarding CCR7 function in mice and humans, and the biology of DCs that populate the ocular surface are also detailed herein. The involvement of DCs and their expression of CCR7 in corneal and ocular surface diseases such as in ocular allergy, dry eye disease, immune rejection and more, are also reviewed here.

Cytokine profiles in tears accompanying the secondary conjunctival responses induced by nasal allergy

PURPOSE/AIM

Allergic conjunctivitis (AC) occurs either in a primary form, due to the allergic reaction localized in the conjunctivae or in a secondary form, induced by an allergic reaction initiated primarily in the nasal mucosa. The purpose of this study was to investigate the cytokine profiles in tears associated with the secondary conjunctival response (SCR) types.

MATERIALS AND METHODS

In 47 AC patients developing 16 immediate (SICR; p < 0.01), 20 late (SLCR; p < 0.001) and 11 delayed (SDYCR; p < 0.05) responses to nasal provocation tests (NPTs) with allergens, the NPTs were repeated and combined with recording of cytokine concentrations in the tears.

RESULTS

The SCRs were associated with significant concentration changes of particular cytokines in tears (p < 0.05) as follows: (1): SICRs: interleukin (IL)-3, IL-4, IL-10 and granulocyte macrophage colony-stimulating factor (GM-CSF); (2) SLCRs: IL-3, IL-4, IL-5, IL-8, IL-10, IL-12p40, GM-CSF and granulocyte colony-stimulating factor (G-CSF); and (3) SDYCRs: IL-2, IL-8, IL-10, interferon gamma, G-CSF and tumor necrosis factor alpha. No significant cytokine changes were recorded in tears during the phosphate-buffered saline controls or negative SCRs.

CONCLUSIONS

Different cytokine profiles in the tears accompanying the immediate, late and delayed types of SCR, induced by nasal allergy, would indicate involvement of different hypersensitivity mechanisms in the particular SCR types. The low cytokine concentrations in tears recorded during the SCRs may suggest their origin from the nasal mucosa. These results emphasize the diagnostic value of NPTs with allergens combined with monitoring of various ocular features in patients suffering from the secondary form of AC. These results may also have an impact on the therapeutical approach to this clinical entity.

Ocular allergy modulation to hi-dose antigen sensitization is a Treg-dependent process

A reproducible method to inhibit allergic immune responses is accomplished with hi-dose Ag sensitization, via intraperitoneal (IP) injection. However, the role of CD4+ CD25+ FoxP3+ T regulatory cells (Treg) in this process is unknown, as is whether such modulation extends to ocular allergy. We therefore determined herein whether hi-dose sensitization modulates ocular allergy, and whether CD4+ CD25+ FoxP3+ Treg are involved. C57BL/6 mice were IP sensitized via low-dose (100 µg) versus hi-dose (1000 µg) ovalbumin (OVA), in aluminum hydroxide (1 mg) and pertussis-toxin (300 ng). Other mice received anti-CD25 Ab (PC61) to ablate Treg during sensitization. In another experiment, Treg from hi-dose sensitized mice were adoptively transferred into low-dose sensitized mice. Once daily OVA challenges were administered. Clinical signs, IgE, T cell cytokines, and eosinophils were assessed. Data revealed that hi-dose, but not low-dose, sensitization led to allergy modulation, indicated by decreased clinical signs, serum IgE levels, Th2 recall responses, and eosinophil recruitment. T cells from hi-dose sensitized mice showed a robust increase in TGF-b production, and Treg from these mice were able to efficiently suppress effector T cell proliferation in vitro. In addition, in vivo Treg ablation in hi-dose sensitized mice revoked allergy modulation. Lastly, Treg from hi-dose sensitized mice were able to adoptively transfer allergy modulation to their low-dose sensitized counterparts. Collectively, these findings indicate that modulation to hi-dose sensitization, which is extended to ocular allergy, occurs in a Treg-dependent manner. In addition, our data suggest that hi-dose sensitization may henceforth facilitate the further examination of CD4+ CD25+ FoxP3+ Treg in allergic disease.

Regulation of interleukin 33/ST2 signaling of human corneal epithelium in allergic diseases

AIM

To identify the function of ST2 and explore the role of IL-33/ST2 signaling in regulating the pro-allergic cytokine production in human corneal epithelial cells (HCECs).

METHODS

Human corneal tissues and cultured primary HCECs were treated with IL-33 in different concentrations without or with different inhibitors to evaluate the expression, location and signaling pathways of ST2 in regulating production of pro-allergic cytokine and chemokine. The expression of mRNA was determined by reverse transcription and real time PCR, and protein production was measured by enzyme-linked immunosorbent assay (ELISA), immunohistochemical and immunofluorescent staining. ST2 protein was detected in donor corneal epithelium, and ST2 signal was enhanced by exposure to IL-33.

RESULTS

IL-33 significantly stimulated production of pro-allergic cytokines thymic stromal lymphopoietin (TSLP) and chemokine (CCL2, CCL20, CCL22) in HCECs at both mRNA and protein levels. These stimulated productions of pro-allergic mediators by IL-33 were blocked by ST2 antibody or soluble ST2 protein (P<0.05). Interestingly, the IκB-α inhibitor BAY11-7082 or NF-κB activation inhibitor quinazoline blocked NF-κB p65 protein nuclear translocation, and also suppressed the productions of these pro-allergic cytokines and chemokine induced by IL-33.

CONCLUSION

These findings demonstrate that IL-33/ST2 signaling plays an important role in regulating IL-33 induced pro-allergic responses. IL-33 and ST2 could become novel molecular targets for the intervention of allergic diseases in ocular surface.

Novel anti(lymph)angiogenic treatment strategies for corneal and ocular surface diseases

The cornea is one of the few tissues which actively maintain an avascular state, i.e. the absence of blood and lymphatic vessels (corneal [lymph]angiogenic privilege). Nonetheless do several diseases interfere with this privilege and cause pathologic corneal hem- and lymphangiogenesis. The ingrowths of pathologic blood and lymphatic vessels into the cornea not only reduce transparency and thereby visual acuity up to blindness, but also significantly increases the rate of graft rejections after subsequent corneal transplantation. Therefore great interest exists in new strategies to target pathologic corneal (lymph)angiogenesis to promote graft survival. This review gives an overview on the vascular anatomy of the normal ocular surface, on the molecular mechanisms contributing to the corneal (lymph)angiogenic privilege and on the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea. In addition we summarize the current preclinical and clinical evidence for three novel treatment strategies against ocular surface diseases based on targeting pathologic (lymph)angiogenesis: (a) modulation of the immune responses after (corneal) transplantation by targeting pathologic (lymph)angiogenesis prior to and after transplantation, (b) novel concepts against metastasis and recurrence of ocular surface tumors such as malignant melanoma of the conjunctiva by anti(lymph)angiogenic therapy and (c) new ideas on how to target ocular surface inflammatory diseases such as dry eye by targeting conjunctival and corneal lymphatic vessels. Based on compelling preclinical evidence and early data from clinical trials the novel therapeutic concepts of promoting graft survival, inhibiting tumor metastasis and dampening ocular surface inflammation and dry eye disease by targeting (lymph)angiogenesis are on their way to translation into the clinic.

Short ragweed pollen triggers allergic inflammation through Toll-like receptor 4-dependent thymic stromal lymphopoietin/OX40 ligand/OX40 signaling pathways

BACKGROUND

Allergic diseases affect a large population. Pollen, an ubiquitous allergen, is the trigger of seasonal rhinitis, conjunctivitis, and asthma, as well as an exacerbating factor of atopic dermatitis. However, the underlying mechanism by which pollen induces thymic stromal lymphopoietin (TSLP)-triggered allergic inflammation through epithelial innate immunity is largely unknown.

OBJECTIVE

We sought to explore whether short ragweed (SRW) pollen induces TSLP/OX40 ligand (OX40L)/OX40 signaling through Toll-like receptor (TLR) 4-dependent pathways in patients with allergic disease.

METHODS

Three models were used for this study, a well-characterized murine model of allergic conjunctivitis induced by SRW pollen, a topical challenge model on the murine ocular surface, and a culture model of primary human corneal epithelium exposed to aqueous extract of defatted SRW pollen (SRWe).

RESULTS

The topical challenges with SRW pollen generated typical allergic conjunctivitis in BALB/c mice. Clinical signs, stimulated TSLP/OX40L/OX40 signaling, and T(H)2 cytokine levels in the ocular mucosa and draining cervical lymph nodes were significantly reduced or eliminated in TLR4-deficient (Tlr4-d) or myeloid differentiation primary response gene 88 (MyD88) knockout (MyD88(-/-)) mice compared with those seen in their wild-type littermates. SRWe stimulated TSLP production by ocular epithelia in wild-type but not Tlr4-d or MyD88(-/-) mice. SRWe-stimulated TSLP was blocked by TLR4 antibody and nuclear factor κB inhibitor in murine and human corneal epithelia.

CONCLUSION

For the first time, we have shown that SRW pollen, acting as a functional TLR4 agonist, initiates TLR4-dependent TSLP/OX40L/OX40 signaling, which triggers T(H)2-dominant allergic inflammation. These findings shed light on the understanding of mucosal epithelial innate immunity and create new therapeutic targets to cure allergic diseases.

Cytokines and chemokines in immune-based ocular surface inflammation

Altered levels of several cytokines and chemokines have been found in different types of inflammatory ocular surface diseases, such as allergy or dry-eye syndrome. It has also been demonstrated that epithelial cells play a key role in the persistence and even initiation of chronic mucosal inflammation. The recent development of 'multiplex detection' technologies has facilitated the identification of specific patterns of expression of these molecules in some ocular immune-based inflammatory disorders. Analysis of these molecules in tissues, cells (in vivo and in vitro) and tears has revealed that not only inflammatory cells but also epithelial and fibroblast resident cells are sources of these molecules. The purpose of this review is to summarize recent studies in this field.

Allergic conjunctivitis exacerbates corneal allograft rejection by activating Th1 and th2 alloimmune responses

Allergic conjunctivitis (AC) and airway hyperreactivity exacerbate corneal allograft rejection. Because AC and airway hyperreactivity are allergic diseases of mucosal tissues, we determined whether an allergic disease of a nonmucosal tissue would affect corneal allograft rejection and whether Th2 cells alone accounted for accelerated graft rejection in allergic mice. Hosts sensitized cutaneously with short ragweed pollen developed cutaneous immediate hypersensitivity but rejected corneal allografts at the same tempo and incidence as naive mice. Th2 immune deviation induced with keyhole limpet hemocyanin and IFA did not affect corneal allograft rejection. Thus, Th2 immune deviation alone does not account for the exacerbation of corneal allograft rejection that occurs in mice with AC. CD4(+) T cells from AC mice elaborated Th1 (IFN-gamma) and Th2 (IL-13) cytokines when challenged with donor alloantigens. Adoptive transfer of Th1 or Th2 cells to nude mice, from AC mice that had rejected corneal allografts, produced graft rejection in 70% and 20% of the hosts, respectively. In contrast, adoptive transfer of a combination of Th1 and Th2 cells produced 100% rejection. Administration of exogenous IFN-gamma could substitute for Th1 cells and produced 100% corneal allograft rejection in recipients of Th2 cells alone. By contrast, IFN-gamma did not significantly enhance corneal allograft rejection mediated by Th1 cells. Thus, exacerbation of corneal allograft rejection in mice with AC is associated with a mixed Th1 and Th2 alloimmune response, and the contribution of Th1 cells is through their production of IFN-gamma.

Pro-angiogenic effect of IFNgamma is dependent on the PI3K/mTOR/translational pathway in human retinal pigmented epithelial cells

Background

Mutations in COL8A2 gene which encodes the collagen alpha-2 (VIII) chain have been identified in both familial and sporadic cases of Fuchs endothelial corneal dystrophy (FECD). Heterozygous mutations in the SLC4A11 gene are also known to cause late-onset FECD. Therefore we screened for COL8A2, SLC4A11 gene variants in Indian FECD patients.

Methods

Eighty patients with clinically diagnosed FECD and 100 age matched normal individuals were recruited. Genomic DNA was isolated from peripheral blood leukocytes. Mutations in COL8A2, SLC4A11 coding regions were screened using bi-directional sequencing. Fischer's exact test or Pearson's chi squared test were used to predict the statistical association of genotypes with the phenotype.

Results

Screening of COL8A2 gene revealed 2 novel c.1610G>A, c.1643A>G and 3 reported variations c.112G>A, c.464G>A and c.1485G>A. In SLC4A11 gene, novel c.1659C>T, c.1974C>T and reported c.405G>A, c.481A>C and c.639G>A variants were identified. However all the variations in both the genes were also present in unaffected controls.

Conclusions

This is the first study analysing COL8A2 gene in Indian patients with FECD. No pathogenic mutations were identified in COL8A2. Merely silent changes, which showed statistically insignificant association with FECD, were identified in the screening of SLC4A11 gene. These results suggest that COL8A2, SLC4A11 genes may not be responsible for FECD in patients examined in this study.

TSLP and downstream molecules in experimental mouse allergic conjunctivitis

PURPOSE

To explore the potential role of thymic stromal lymphopoietin (TSLP) and its downstream molecules in the development of ocular allergic inflammation using a short ragweed (SRW)-induced mouse model of allergic conjunctivitis (AC).

METHODS

BALB/c mice were topically challenged with SRW pollen after they were sensitized with SRW in the footpad. After the last SRW challenge, the corneal epithelium, conjunctiva, and cervical lymph nodes were harvested for total RNA extraction and gene expression by RT and real-time PCR, and whole eye globes were collected to make cryosections for immunohistochemical staining.

RESULTS

Repeated topical challenges with SRW allergen generated typical signs of AC in mice. Compared with the untreated controls, TSLP mRNA expression and immunoreactivity were significantly increased in the corneal and conjunctival epithelia of SRW-induced AC mice. CD11c(+) and OX40L(+) immunoreactive cells largely infiltrated the conjunctiva with increased mRNA levels of CD11c, TSLPR, and OX40L detected in the corneal epithelium, conjunctiva, and cervical lymph nodes. CD4(+) Th2 cell infiltration was evidenced by increased levels of mRNA and immunoreactivity of CD4, IL-4, IL-5, and IL-13 in the ocular surface, mainly in the conjunctiva, accompanied by increased expression of OX40, STAT6, and GATA3, in AC mice. The maturation of immature DCs was observed with the use of TSLP containing conditioned media from corneal epithelial cultures exposed to polyI:C, which stimulates TSLP production.

CONCLUSIONS

This study provides new findings regarding the role of local mucosal epithelial cells in the initiation of ocular allergic inflammation by producing a novel proallergic cytokine, TSLP, which activates dendritic cells to prime Th2 differentiation and allergic inflammation through the TSLP-TSLPR and OX40L-OX40 signaling pathway.

Seasonal and perennial allergic conjunctivitis: the possible role of nasal allergy

BACKGROUND

There is a link between conjunctiva and nose. Nasal allergy is suspected to be involved in some cases of conjunctivitis. This work aims to investigate the possible role of nasal allergy in seasonal (SAC) and perennial (PAC) allergic conjunctivitis and the value of nasal challenges with allergens (nasal provocation tests [NPTs]) for the diagnostic procedures of the conjunctivitis.

METHODS

In 61 adults suffering from SAC or PAC with a positive history and skin tests, but responding insufficiently to the local treatment, 122 NPTs and 61 control nasal challenges with phosphate-buffered saline (PBS) were performed using rhinomanometry combined with recording of ocular response. In 16 control subjects suffering only from allergic rhinitis without a history of conjunctivitis, 16 positive NPTs were repeated and supplemented with registration of ocular features.

RESULTS

Of the 61 patients, 55 developed 103 positive nasal responses of various types (P < 0.01), 82 of which were accompanied by significant conjunctival response (P < 0.01) without any corneal involvement. No significant ocular responses were recorded during 61 control PBS challenges (P > 0.05) as well as during 16 challenges in control subjects (P > 0.1).

CONCLUSIONS

These results illustrate a possible involvement of nasal allergy in some patients with allergic conjunctivitis (SAC and PAC) and the value of the nasal challenges with allergen combined with registration of the ocular features in the diagnostic approach to these disorders.

Acidic mammalian chitinase in dry eye conditions

PURPOSE

An acidic mammalian chitinase (AMCase) seems to be implicated in allergic asthma and allergic ocular pathologies. The aim of this work was to investigate the role of AMCase during Sjögren's Syndrome (SS) and Meibomian Gland Dysfunction (MGD) dry eye diseases.

METHODS

Six patients with MGD dry eye (20-58 years, median 40) and six patients with dry eye associated to SS (32-60 years, median 47) were enrolled in this study. AMCase activity was measured in tears and AMCase mRNA expression was evaluated by real-time polymerase chain reaction from RNA extracted from epithelial cells of the conjunctiva. Six healthy adult subjects of the same age (34-44 years, median 39) were also studied as the control group.

RESULTS

AMCase activity was significantly increased in patients affected by MGD dry eye (18.54 +/- 1.5 nmol/ml/h) and SS dry eye (8.94 +/- 1.0 nmol/ml/h) respectively, compared to healthy controls (1.6 +/- 0.2 nmol/ml/h). AMCase activity was higher in the tears of subjects with MGD dry eye (P < 0.001). AMCase mRNA was detected in conjunctival epithelial cells and the expression was significantly higher in MGD dry eye than SS dry eye. A significant correlation between AMCase activity in the tears and mRNA in conjunctival epithelial cells was found.

CONCLUSION

AMCase may be an important marker in the pathogenesis of dry eye, suggesting the potential role of AMCase as a therapeutic target in these frequent pathologies.

Immunopathogenesis of ocular allergy: a schematic approach to different clinical entities

PURPOSE OF REVIEW

The immunopathogenesis of ocular allergic disorders is generally related to the specific immunoglobulin E-mediated mast cell activation and the following cascade of inflammatory mediators. Seasonal and perennial allergic conjunctivitis, however, are the only ocular diseases to involve solely type I hypersensitivity. The other main forms, vernal and atopic keratoconjunctivitis, have a more complex immunological basis and a chronic inflammatory component. Involvement of inflammatory cells, particularly eosinophils and T cells, cytokines and proteases can lead to more serious corneal damage with vision-threatening potential.

RECENT FINDINGS

Experimental allergic conjunctival models and clinical research studies have shown that T helper type 2-related mechanisms are definitely involved in the sensitization phase of ocular allergy, however, both T helper type 1 and type 2 cytokines are overexpressed in the active disease, contributing to the development of ocular inflammation.

SUMMARY

A review of the recent literature allows us to better understand the mechanisms involved in the development of ocular allergy and to guide us toward a more schematic approach, which could possibly be useful in forming a new classification, standardizing clinical phases and individuating new treatment targets.