Ocular allergy: implications for the clinical immunologist

Dendritiform immune cells with reduced antigen-capture capacity persist in the cornea during the asymptomatic phase of allergic conjunctivitis

BACKGROUND

Increased density and altered morphology of dendritic cells (DC) in the cornea and conjunctiva occur during active allergic conjunctivitis. This study investigated whether inflammation (characterised by altered DC density and morphology) persists during the symptom-free phase of allergic conjunctivitis.

METHODS

Twenty participants (age 43.3 ± 14.3 years, 55% female) assessed during their active (symptomatic) phase of allergic conjunctivitis were re-examined during the asymptomatic phase. Ocular allergy symptoms and signs were evaluated during both phases, and five ocular surface locations (corneal centre, inferior whorl, corneal periphery, corneal limbus, and bulbar conjunctiva) were examined using in vivo confocal microscopy (HRT III). DC were counted manually, and their morphology was assessed for cell body size, presence of dendrites, presence of long dendrites and presence of thick dendrites using a grading system. Mixed model analysis (DC density) and non-parametric tests (DC morphology) were used to examine differences between phases.

RESULTS

DC density at corneal locations did not change between the active and asymptomatic phases (p ≥ 0.22). However, corneal DC body size was smaller and fewer DC presented with long dendrites during the asymptomatic phase (p ≤ 0.02). In contrast, at the bulbar conjunctiva, DC density was reduced during the asymptomatic phase compared to the active phase (p = 0.01), but there were no changes in DC morphology.

CONCLUSIONS

Dendritiform immune cell numbers persist in the cornea during the symptom-free phase of allergic conjunctivitis, whereas conjunctival DC appear to return to a baseline state. The morphology of these persisting corneal DC suggests their antigen-capture capacity is reduced during the asymptomatic phase.

Trifuhalol A Suppresses Allergic Inflammation through Dual Inhibition of TAK1 and MK2 Mediated by IgE and IL-33

The activation and degranulation of immune cells play a pivotal role in allergic inflammation, a pathological condition that includes anaphylaxis, pruritus, and allergic march-related diseases. In this study, trifuhalol A, a phlorotannin isolated from Agarum cribrosum, inhibited the degranulation of immune cells and the biosynthesis of IL-33 and IgE in differentiated B cells and keratinocytes, respectively. Additionally, trifuhalol A suppressed the IL-33 and IgE-mediated activation of RBL-2H3 cells through the regulation of the TAK1 and MK2 pathways. Hence, the effect of trifuhalol A on allergic inflammation was evaluated using a Compound 48/80-induced systemic anaphylaxis mouse model and a house dust mite (HDM)-induced atopic dermatitis (AD) mouse model. Trifuhalol A alleviated anaphylactic death and pruritus, which appeared as an early-phase reaction to allergic inflammation in the Compound 48/80-induced systemic anaphylaxis model. In addition, trifuhalol A improved symptoms such as itching, edema, erythema, and hyperkeratinization in HDM-induced AD mice as a late-phase reaction. Moreover, the expression of IL-33 and thymic stromal lymphopoietin, inflammatory cytokines secreted from activated keratinocytes, was significantly reduced by trifuhalol A administration, resulting in the reduced infiltration of immune cells into the skin and a reduction in the blood levels of IgE and IL-4. In summarizing the above results, these results confirm that trifuhalol A is a potential therapeutic candidate for the regulation of allergic inflammation.

DS-70, a novel and potent α4 integrin antagonist, is an effective treatment for experimental allergic conjunctivitis in guinea pigs

BACKGROUND AND PURPOSE

Allergic conjunctivitis is an eye inflammation that involves the infiltration of immune cells into the conjunctiva via cell surface-adhesion receptors, such as integrin α₄ β₁ . These receptors interact with adhesion molecules expressed on the conjunctival endothelium and may be a target to treat this disease. We synthesized DS-70, a novel α/β-peptidomimetic α₄ integrin antagonist, to prevent the conjunctival infiltration of immune cells and clinical symptoms in a model of allergic conjunctivitis.

EXPERIMENTAL APPROACH

In vitro, DS-70 was pharmacologically characterized using a scintillation proximity procedure to measure its affinity for α₄ β₁ integrin, and its effect on cell adhesion mediated by different integrins was also evaluated. The effects of DS-70 on vascular cell adhesion molecule-1 (VCAM-1)-mediated degranulation of a human mast cell line and an eosinophilic cell line, which both express α₄ β₁ , and on VCAM-1-mediated phosphorylation of ERK 1/2 in Jurkat E6.1 cells were investigated. Effects of DS-70 administered in the conjunctival fornix of ovalbumin-sensitized guinea pigs were evaluated.

KEY RESULTS

DS-70 bound to integrin α₄ β₁ with nanomolar affinity, prevented the adhesion of α₄ integrin-expressing cells, antagonized VCAM-1-mediated degranulation of mast cells and eosinophils and ERK 1/2 phosphorylation. Only 20% was degraded after an 8 h incubation with serum. DS-70 dose-dependently reduced the clinical symptoms of allergic conjunctivitis, conjunctival α₄ integrin expression and conjunctival levels of chemokines and cytokines in ovalbumin-sensitized guinea pigs.

CONCLUSIONS AND IMPLICATIONS

These findings highlight the role of α₄ integrin in allergic conjunctivitis and suggest that DS-70 is a potential treatment for this condition.

MAST CELLS DISTINGUISH EOSINOPHILIC ESOPHAGITIS IN PEDIATRIC PATIENTS

ABSTRACT BACKGROUND: Mast cells exert a substantial role in gastrointestinal allergic diseases. Therefore, it is reasonable to presume that mast cell may aid diagnosis in eosinophilic gastroenteropathy. OBJECTIVE: To evaluate whether mast cell count in the esophageal epithelium can discriminate eosinophilic esophagitis, proton-pump inhibitor (PPI)-responsive eosinophilic esophagitis and gastroesophageal reflux esophagitis. METHODS: Retrospectively we reviewed the files of 53 consecutive patients (age: 7.8 years; range: 8-14 years) with definitive diagnose established during clinical follow up in a universitary outpatient clinic as follow: eosinophilic esophagitis (N=23), PPI-responsive eosinophilic esophagitis (N=15) and gastroesophageal reflux esophagitis (N=15). Eosinophil count in the esophageal epithelium in slides stained with H-E was reviewed and immunohistochemistry for mast cell tryptase was performed. RESULTS: Count of eosinophils/high-power field (HPF) higher than 15 were found in 14 out of 15 reflux esophagitis patients. The mean count of eosinophils/HPF was similar in eosinophilic esophagitis patients and in those with PPI-responsive eosinophilic esophagitis (42 and 39 eosinophils/HPF, respectively, P=0.47). Values of mast cell tryptase (+) were higher in eosinophilic esophagitis [median: 25 mast cells/HPF; range (17-43) ] and in PPI-responsive eosinophilic esophagitis patients [25 (16-32) ], compared to reflux esophagitis [4 (2-14) ], P<0.001. There was no difference between the mean count of mast cells/HPF in the esophageal epithelium of eosinophilic esophagitis patients and PPI-responsive eosinophilic esophagitis patients, respectively, 26 and 24 mast cells/HPF, P=0.391. CONCLUSION: Tryptase staining of mast cells differentiates eosinophilic esophagitis from reflux esophagitis.

Allergic conjunctivitis and the most common allergens in Northern Greece

Background

Ocular allergies affect a great part of the general population and often co exist with other allergic manifestations. In the present study, the prevalence of allergic conjunctivitis and the commonest allergens in allergic patients at an outpatient unit in Thessaloniki, Greece were evaluated.

Methods

This is a retrospective study regarding allergic patients who referred to an outpatient clinic between the 1st of January of 1996 and the 31st of December 2010. They completed relative questionnaires concerning their allergic condition. The patients who were included in our study had allergic conjunctivitis confirmed by ophthalmologists and were divided into 4 groups. The criteria used were the existence of allergic conjunctivitis alone or with other allergic co- morbidities. The patients then underwent skin prick tests after consent according to current guidelines.

Results

The archives of 1239 allergic patients were evaluated and 497 patients (40,11%) who manifested eye allergic symptoms were included in our study. 448 patients (90.14%) had allergic conjunctivitis in conjunction with asthma or rhinitis or both. 370 patients underwent skin prick tests and 284 of them (124 males-160 females) were positive for at least 1 of the 8 tested allergens (76.75%). 166 were positive to a grass mix (58.45%), 130 to olea European (45.77%), 124 to dust mites mix (43.66%), 58 to cypress (20.42%), 71 to parietaria officinalis (25.00%), 67 to cat dander (23.59%), 35 to dog dander (12.32%) and 32 to Altenaria (11.26%).

Conclusions

Symptoms of ocular allergy are very common in patients with allergic rhinitis and asthma. Men had slightly higher percentages of positive skin prick tests, except for dog dander and Altenaria. Conjunctivitis should not be overlooked as an allergic entity when evaluating allergic patients.

Ocular allergy in the Asia Pacific region

Allergic conjunctivitis (AC) represents a spectrum of disorders, comprising seasonal allergic conjunctivitis (SAC), perennial allergic conjunctivitis (PAC), atopic keratoconjunctivitis (AKC), vernal keratoconjunctivitis (VKC) and giant papillary conjunctivitis. Of these ocular allergy types, SAC and PAC are the most common.The most striking difference within this group of ocular diseases is that SAC and PAC remain self-limited without ocular surface damage, while AKC and VKC can compromise the cornea, causing ulcers and scarring and can ultimately lead to vision loss. Data on AC in the Asia Pacific is scarce however some understanding of prevalence of the condition has been obtained from the International Study of Asthma and Allergies in Childhood (ISAAC) studies and more recently from the Allergies in Asia Pacific study as well as some information from individual country surveys. Unfortunately none of this data has been collected using validated survey instruments specifically designed for AC. Surveys such as ISAAC have been predominantly concerned with respiratory allergic symptoms with questions added that incorporate some ocular symptoms. These questionnaires do not detect individuals who may have AC in the absence of allergic rhinitis. Using hospital ophthalmology outpatient populations for prevalence studies of ocular allergy immediately introduces a bias towards the more severe, complex forms of the condition as patients with the milder forms of SAR and PAR will rarely present to a hospital outpatient clinic. There is a real need for the development of validated questionnaires specifically addressing ocular allergy. There are no widely accessible studies examining prevalence of the complex forms of ocular allergy (AKC, VKC) in Asia Pacific region. This review will provide an overview of ocular allergy, its classification, clinical presentation and differential diagnosis, and will also discuss what is known about the epidemiology of ocular allergy in the Asian Pacific region.

Analysis of Ag-presenting cells in the conjunctiva during the development of experimental immune-mediated blepharoconjunctivitis

PURPOSE

The aim of this study was to investigate the phenotypes of antigen (Ag) presenting cells (APCs) in the conjunctiva during the development of experimental immune-mediated blepharoconjunctivitis (EC), which serves as a model for investigation of severe types of human allergic conjunctivitis.

METHODS

Brown Norway rats treated by ovalbumin (OVA) were used in this study. To confirm the restriction of MHC class II by OVA-specific T cells, monoclonal Abs against MHC class II were added to the conventional proliferation assay. To evaluate the MHC class II expression in the conjunctiva during the development of EC, an immunohistochemical analysis, either as the single or double staining, was performed. Conjunctival fibroblast cell lines were established from naive rats and the MHC class II expression was evaluated by flow cytometric analysis. To examine the roles of costimulatory molecules, OVA-specific T cells were stimulated with anti-TcR Ab and anti-CD28 Ab and then subjected for Western blotting to evaluate the ERK phosphorylation. Finally, in vivo expression of B7 molecules was examined immunohistochemically.

RESULTS

OVA-specific T cells recognized OVA in the context of MHC class II. MHC class II was expressed in conjunctival macrophages but not in fibroblasts. EC induction was accompanied by abundant infiltration of macrophages positive for MHC class II. MHC class II was also expressed in conjunctival epithelial cells by EC induction. Stimulation from CD28 was necessary for ERK phosphorylation. B7-2, but not B7-1, was expressed in the conjunctiva.

CONCLUSION

Conjunctival macrophages may represent a major source of APCs for the induction of EC in the conjunctiva.

Contribution of alpha4beta1 integrin to the antiallergic effect of levocabastine

Levocabastine is an antiallergic drug acting as a histamine H1-receptor antagonist. In allergic conjunctivitis (AC), it may also antagonize up-regulation of the intercellular adhesion molecule-1 (ICAM-1) expressed on epithelial conjunctival cells. However, little is known about its effects on eosinophils, important effector cells in AC. The adhesion molecule integrin alpha(4)beta(1) is expressed in eosinophils; it interacts with the vascular cell adhesion molecule-1 (VCAM-1) and fibronectin (FN) in vascular endothelial cells and contributes to eosinophil activation and infiltration in AC. This study provides evidence that in a scintillation proximity assay levocabastine (IC(50) 406 microM), but not the first-generation antihistamine chlorpheniramine, displaced (125)I-FN binding to human integrin alpha(4)beta(1) and, in flow cytometry analysis, levocabastine antagonized the binding of a primary antibody to integrin alpha(4) expressed on the Jurkat cell surface. Levocabastine, but not chlorpheniramine, binds the alpha(4)beta(1) integrin and prevents eosinophil adhesion to VCAM-1, FN or human umbilical vascular endothelial cells (HUVEC) in vitro. Similarly, levocabastine affects alpha(L)beta(2)/ICAM-1-mediated adhesion of Jurkat cells. In a model of AC levocabastine eye drops reduced the clinical aspects of the late-phase reaction and the conjunctival expression of alpha(4)beta(1) integrin by reducing infiltrated eosinophils. We propose that blockade of integrin-mediated cell adhesion might be a target of the antiallergic action of levocabastine and may play a role in preventing eosinophil adhesion and infiltration in AC.

Differential contributions of B7-1 and B7-2 to the development of murine experimental allergic conjunctivitis

B7-1 and B7-2 are the co-stimulatory molecules that are involved in activation of T cells. We investigated whether B7-1 and B7-2 play a role in the development of T cell-mediated experimental allergic conjunctivitis (EC). EC was induced in Balb/c mice by active immunization with ragweed (RW) followed by RW challenge in eye drops. These mice were treated with neutralizing anti-B7-1 Ab, anti-B7-2 Ab, both Abs, anti-cytotoxic T lymphocyte-associated Ag-4 (CTLA-4) Ab or normal IgGs as controls either during the induction phase or the effector phase. With regard to the induction phase treatment, EC was significantly attenuated when both anti-B7-1 and anti-B7-2 Abs were injected. In contrast, anti-CTLA-4 Ab treatment significantly exacerbated EC. With regard to the effector phase treatment, anti-B7-2 Ab alone significantly attenuated EC, while anti-CTLA-4 Ab tended to exacerbate EC. Collectively, B7-1 and B7-2 differently contribute to the development of EC during the induction and effector phases.

Omalizumab: a future innovation for treatment of severe ocular allergy?

Conjunctival and corneal manifestations of atopic keratoconjunctivitis (AKC) are chronic, disabling and may be blinding. In common with other allergic diseases, such as asthma and atopic dermatitis, AKC is characterised by an allergen-induced immune response mediated through expression of IgE. The humanised monoclonal IgE antibody Xolair (omalizumab) complexes with free circulating IgE, thereby preventing binding of IgE to FcepsilonRI receptors on immune cells. Omalizumab effectively alleviates the signs and symptoms of asthma. Given the pivotal role of IgE in the allergic cascade, it is hypothesised that omalizumab has potential as an entirely new therapeutic approach to AKC.

Efficacy and tolerability of newer antihistamines in the treatment of allergic conjunctivitis

Treatment for allergic conjunctivitis has markedly expanded in recent years, providing opportunities for more focused therapy, but often leaving both physicians and patients confused over the variety of options. As monotherapy, oral antihistamines are an excellent choice when attempting to control multiple early-phase, and some late-phase, allergic symptoms in the eyes, nose and pharynx. Unfortunately, despite their efficacy in relief of allergic symptoms, systemic antihistamines may result in unwanted adverse effects, such as drowsiness and dry mouth. Newer second-generation antihistamines (cetirizine, fexofenadine, loratadine and desloratadine) are preferred over older first-generation antihistamines in order to avoid the sedative and anticholinergic effects that are associated with first-generation agents. When the allergic symptom or complaint, such as ocular pruritus, is isolated, focused therapy with topical (ophthalmic) antihistamines is often efficacious and clearly superior to systemic antihistamines, either as monotherapy or in conjunction with an oral or intranasal agent. Topical antihistaminic agents not only provide faster and superior relief than systemic antihistamines, but they may also possess a longer duration of action than other classes including vasoconstrictors, pure mast cell stabilisers, NSAIDs and corticosteroids. Many antihistamines have anti-inflammatory properties as well. Some of this anti-inflammatory effect seen with 'pure' antihistamines (levocabastine and emedastine) may be directly attributed to the blocking of the histamine receptor that has been shown to downregulate intercellular adhesion molecule-1 expression and, in turn, limit chemotaxis of inflammatory cells. Some topical multiple-action histamine H(1)-receptor antagonists (olopatadine, ketotifen, azelastine and epinastine) have been shown to prevent activation of neutrophils, eosinophils and macrophages, or inhibit release of leukotrienes, platelet-activating factors and other inflammatory mediators. Topical vasoconstrictor agents provide rapid relief, especially for redness; however, the relief is often short-lived, and overuse of vasoconstrictors may lead to rebound hyperaemia and irritation. Another class of topical agents, mast cell stabilisers (sodium cromoglicate [cromolyn sodium], nedocromil and lodoxamide), may be considered; however, they generally have a much slower onset of action. The efficacy of mast cell stabilisers may be attributed to anti-inflammatory properties in addition to mast cell stabilisation. In the class of topical NSAIDs, ketorolac has been promoted for ocular itching but has been found to be inferior for relief of allergic conjunctivitis when compared with olopatadine and emedastine. Lastly, topical corticosteroids may be considered for severe seasonal ocular allergy symptoms, although long-term use should be avoided because of risks of ocular adverse effects, including glaucoma and cataract formation.