Clinical Severity and Tear Biomarkers, Eosinophil Cationic Protein and CCL23, in Chronic Allergic Conjunctival Diseases

Eosinophilic mucus diseases

Eosinophilic inflammation is primarily characterized by type 2 immune responses against parasitic organisms. In the contemporary human being especially in developed countries, eosinophilic inflammation is strongly associated with allergic/sterile inflammation, and constitutes an undesired immune reaction. This situation is in stark contrast to neutrophilic inflammation, which is indispensable for the host defense against bacterial infections. Among eosinophilic inflammatory disorders, massive accumulation of eosinophils within mucus is observed in certain cases, and is often linked to the distinctive clinical finding of mucus with high viscosity. Eosinophilic mucus is found in a variety of diseases, including chronic allergic keratoconjunctivitis, chronic rhinosinusitis encompassing allergic fungal sinusitis, eosinophilic otitis media, eosinophilic sialodochitis, allergic bronchopulmonary aspergillosis/mycosis, eosinophilic plastic bronchitis, and eosinophilic asthma. In these pathological conditions, chronic inflammation and tissue remodeling coupled with irreversible organ damage due to persistent adhesion of toxic substances and luminal obstruction may impose a significant burden on the body. Eosinophils aggregate in the hyperconcentrated mucus together with cell-derived crystals, macromolecules, and polymers, thereby affecting the biophysical properties of the mucus. This review focuses on the clinically significant challenges of mucus and discusses the consequences of activated eosinophils on the mucosal surface that impact mucus and persistent inflammation.

Emerging therapies targeting eosinophil-mediated inflammation in chronic allergic conjunctivitis

Ocular allergy remains a significant burden to the population while the treatment for the severe, chronic forms of allergic conjunctivitis remains largely limited to non-specific immunosuppressants. Eosinophils are central to the pathophysiology and sustaining the immunologic response found in the chronic forms of ocular allergy such as vernal keratoconjunctivitis and atopic keratoconjunctivitis. Several mediators of eosinophil recruitment, chemotaxis, adhesion, activation, and survival have been identified that offer potential therapeutic targets for ocular allergy. Based on preclinical and clinical data available in both ocular and non-ocular allergy studies, these emerging therapies warrant further investigation in reducing the severity of disease in patients with chronic ocular allergy.

Tear and ocular surface disease biomarkers: A diagnostic and clinical perspective for ocular allergies and dry eye disease

Validated biomarkers to be used as biological tools for managing ocular surface diseases (OSDs) are still an unmet need in daily clinical practice. Many studies have contributed to the already extensive list of candidate biomarkers for these disorders. Dry eye (DE) and ocular allergy (OA) are complex and multifactorial diseases, often coexisting and with overlapping symptoms. The purpose of this review is to present a comprehensive updated revision of the most relevant biomarkers of DE and OA, with an emphasis on quantitative analyses and correlations with clinical parameter data. Analysis of biomarkers common for these pathologies has highlighted an important physiological process. Namely, the interleukin proteins (IL-1α, IL-1β and IL-17), tumour necrotic factor (TNFα) and interferon gamma (IFNγ; Th1-Th7 pathway) and IL-4, IL-5 and IL-13 (Th2 pathway) seem to represent similar inflammatory mechanisms. Moreover, changes in the levels of mucins (MUC1, MUC2, MUC4, MUC5 and MUC16) are common alterations in the tear film mucous layer. We also examine the current state of medical devices and the main limitations to their use in clinical practice. Translational research in biomarkers for clinical practice depends on a feasible transition from the laboratory to the point-of-care. This requires large-scale, coordinated clinical validation campaigns to select the biomarkers with the highest specificity and sensitivity and significant correlation with clinical parameters. Moreover, technical limitations of multiplexed quantitation systems must be overcome to detect and measure the levels of several biomarkers in very small samples. To ensure the future of biomarker research, significant progress is necessary in a number of fields. There is an urgent need for global unification of clinical classification and diagnostics criteria. Widespread integration of proteomic and transcriptomic data is paramount for performing meaningful analyses using appropriate bioinformatics tools and artificial intelligence systems.

Role of Damage-Associated Molecular Patterns (DAMPs/Alarmins) in Severe Ocular Allergic Diseases

Severe ocular allergic diseases, such as atopic keratoconjunctivitis and vernal keratoconjunctivitis, cause severe allergic inflammation in the conjunctiva and corneal epithelial damage, resulting in visual disturbances. The involvement of damage (danger)-associated molecular patterns (DAMPs/alarmins) in the pathogenesis of these diseases has been recognized. Alarmins released from damaged corneal epithelial cells or eosinophils play a critical role in the induction of corneal lesions, vicious loop of corneal injury, and exacerbation of conjunctival allergic inflammation. Alarmins in the conjunctiva also play an essential role in the development of both allergic inflammation, based on the acquired immune system, and type 2 inflammation by innate immune responses in the ocular surface. Therefore, alarmins may be a potentially important therapeutic target in severe refractory ocular allergic diseases.

Alterations in Mucin-Associated Gene Expression on the Ocular Surface in Active and Stable Stages of Atopic and Vernal Keratoconjunctivitis

Purpose

To evaluate the presence of ocular surface mucin in patients with atopic and vernal keratoconjunctivitis (AKC/VKC), we investigated the mRNA expression levels of SAM-pointed domain-containing ETS-like factor (SPDEF) and mucin-related genes on the ocular surface.

Methods

Nineteen patients with AKC or VKC were divided into two groups based on the severity of the disease as determined by their clinical scores for AKC/VKC: the stable group and the active group. Impression cytology was performed in all patients using filter paper, and the expression levels of SPDEF, MUC1, MUC4, MUC5AC, MUC16, and eotaxin-2 mRNA were determined by real-time reverse-transcription polymerase chain reaction.

Results

The results showed that the expression levels of SPDEF and MUC5AC mRNA in the active group were significantly decreased compared with those in the stable group. Furthermore, clinical scores were significantly negatively correlated with the expression levels of SPDEF mRNA and significantly positively correlated with the expression levels of eotaxin-2, which is a biomarker for eosinophilic inflammation on the ocular surface. Cluster analysis classified the patients with AKC/VKC into three clusters, and the stable group was divided into two clusters according to the condition of ocular surface mucin.

Conclusions

Ocular surface mucin in patients with AKC/VKC is altered in accordance with the clinical severity of the disease.

IL-1α antibody inhibits dose-dependent exacerbation of eosinophilic inflammation by crude house-dust-mite antigen in the conjunctiva of an atopic keratoconjunctivitis mouse model

PURPOSE

To investigate whether crude house-dust-mite antigen exacerbates eosinophilic inflammation in the conjunctival tissues of an atopic keratoconjunctivitis mouse model in a dose-dependent manner.

MATERIALS AND METHODS

An atopic keratoconjunctivitis mouse model was established by percutaneous sensitization and crude house-dust-mite antigen application in NC/Nga mice. To assess the dose-dependent response, conjunctival specimens from groups that were administered high- (High-HDM) or low-dose house-dust-mite antigen (Low-HDM) following percutaneous sensitization and the control without house-dust-mite antigen administration (control group) were evaluated. Histological examination and immunofluorescence staining were performed to determine eosinophil density and the number of IL-13-positive cells. Polymerase chain reaction array was used to obtain adaptive and innate immunity-related factor profile, and quantitative polymerase chain reaction was used to determine Il13, Il17a, Ccl11, and Ccl24 expression. Atopic keratoconjunctivitis model mice injected with anti-IL-1α antibody (IL-1α group) or vehicle (vehicle group) to the upper and lower eyelids before atopic keratoconjunctivitis development were evaluated.

RESULTS

Eosinophil density in the conjunctiva increased with house-dust-mite antigen application in a dose-dependent manner. CD4, CXCL10, CCR6, C3, and IL-13 mRNA levels increased more than 5-fold in the conjunctiva of the High-HDM group animals compared to those in control animals. mRNA expression of Il13 and Ccl11 in the conjunctiva of the High-HDM group animals significantly increased compared with that in the Low-HDM and control group animals. Conversely, the eosinophil density and Il13 mRNA expression significantly decreased in the IL-1α group compared with those in the vehicle group.

CONCLUSIONS

The house-dust-mite antigen increased eosinophilic infiltration and Il13 mRNA expression in the conjunctiva of an atopic keratoconjunctivitis mouse model in a dose-dependent manner. These inflammatory alterations were partially alleviated by eyelid injection of anti-IL-1α antibody. These findings indicate that IL-1α-induced IL-13 production constitutes a major exacerbating factor for house-dust-mite antigen-induced atopic keratoconjunctivitis.

Ocular allergy test and biomarkers on the ocular surface: Clinical test for evaluating the ocular surface condition in allergic conjunctival diseases

Allergic conjunctival diseases (ACDs) are inflammatory diseases of the conjunctiva and cornea caused predominantly by the IgE-mediated immediate hypersensitivity response. Allergic conjunctival diseases include allergic conjunctivitis, vernal keratoconjunctivitis (VKC), atopic keratoconjunctivitis (AKC), and giant papillary conjunctivitis. In clinical practice of ACDs, an ocular allergy test using biomarker measurement is a crucial examination technique for diagnosing, evaluating severity, and determining the efficacy of medical treatment. The ocular allergy test includes the tear test for evaluating the concentration of biomarkers in tears and an ocular surface test for assessing the expression levels of messenger ribonucleic acid (mRNA) biomarkers on the ocular surface. The clinical usefulness of several biomarkers has been demonstrated in patients with ACDs; specifically, eosinophil cationic protein and eotaxin-2 as eosinophilic inflammation biomarkers; interleukin-4 and thymus and activation regulated chemokine (CCL17/TARC) as Th2 inflammation biomarkers; eotaxin, tumor necrosis factor-alpha and soluble IL-6 receptor as giant papillae biomarkers; and osteopontin and periostin as allergic inflammation and remodeling biomarkers. Furthermore, the ocular allergy test, quantitative evaluation methods using biomarkers have allowed for better understanding of the immunological and pathophysiological mechanisms of ACDs. Therefore, the search for a biomarker is important to make an ocular allergy test useful. In previous ocular allergy tests, the biomarkers for allergic inflammation in patients with chronic ACDs including VKC and AKC were substantial. However, the selection of biomarkers associated with the early phase reaction of immediate hypersensitivity and innate immunity responses needs to be addressed in future investigations.

Chemokines in allergic conjunctivitis

PURPOSE OF REVIEW

Chemokines are a large group of low molecular weight cytokines that attract and activate leukocytes throughout the body and therefore have a key role in the framework of late-phase allergic responses. The purpose of this article is to provide an overview of the main chemokines involved in allergic conjunctivitis, their primary functions and their physiological roles, and therapies targeted at chemokines and their receptors for ocular allergic diseases.

RECENT FINDINGS

In recent years, there have been considerable advances in the understanding of ocular pathophysiology of ocular surface inflammatory diseases including both allergic eye diseases and dry eye syndrome. Several therapies being developed for dry eye inflammation are recognized as possible therapies for ocular allergic diseases as there are often common chemokines involved in both disease spectra.

SUMMARY

Chemokines represent an integral part of the late-phase cascade of ocular allergic inflammation. A deep understanding of specific chemokines and their interactions will help in targeting therapies to effectively manage ocular clinical findings and symptoms of allergic eye disease.

Potential Biomarkers for Allergic Conjunctival Diseases

Allergic conjunctival diseases (ACDs) are a group of ocular allergies that include allergic conjunctivitis, atopic keratoconjunctivitis, vernal keratoconjunctivitis, and giant papillary conjunctivitis. Although a large body of information exists on the pathophysiology of ACDs, this has not yet lead to the development of clear recommendations and guidelines for the diagnosis of ACDs or development of conclusive and objective diagnostic tools. Identification of objectively measurable biomarkers that represent the molecular and cellular mechanisms associated with ACDs will be an important step toward achieving these aims. This is a comprehensive review of biological markers that have the potential to become "biomarker(s)" for ACDs and aid in the classification, diagnosis, and development of new therapeutic strategies for these group of allergic conditions.

Evaluation of Chemokine mRNA Expression to Assess Allergic Inflammation of the Ocular Surface in Chronic Allergic Conjunctival Diseases

Purpose:

We validated the use of chemokine messenger RNA (mRNA) expression analysis for the assessment of ocular surface allergic inflammation in chronic allergic conjunctival diseases (ACDs) with proliferative lesions, including giant papillae and gelatinous infiltration of the limbus.

Methods:

This prospective sectional study included 19 patients with chronic ACDs and 10 healthy volunteers as controls. Patients with chronic ACDs were divided into 2 subgroups according to the severity of the clinical score: active stage ACD subgroup (n = 9) and stable stage ACD subgroup (n = 10). Impression cytology using a filter paper for each upper tarsal conjunctiva of the patients with chronic ACDs and control subjects was performed, and the expression levels of IL1A, CXCL8, IL16, and CCL24 mRNAs encoding interleukin (IL)-1α, CXCL8/IL-8, IL-16, and CCL24/eotaxin-2, respectively, were determined by quantitative real-time polymerase chain reaction using impression cytology specimens.

Results:

CCL24 and IL16 mRNA levels in the active ACD subgroup were significantly higher than those in the control group (P = 0.003 and 0.004, respectively). IL1A and CXCL8 expression levels in the active ACD subgroup were significantly higher than those in the stable ACD (P = 0.008 and 0.029, respectively) and control (P = 0.008 and 0.014, respectively) subgroups. Furthermore, significant correlations were detected between IL16 and CCL24 mRNA levels (r = 0.76, P = 0.0001) and between IL1A and CXCL8 (r = 0.67, P = 0.0004).

Conclusions:

At least 2 kinds of inflammatory reactions, IL-1α- and CXCL8-associated inflammation and CCL24- and IL-16-associated inflammation, may be involved in the exacerbation of chronic ACDs.

Vernal Keratoconjunctivitis: an update focused on clinical grading system

INTRODUCTION

Vernal keratoconjunctivitis (VKC) is a severe disease with a prevalence of < 1 case out of 10,000 in Europe, which occurs mainly in pediatric age and is characterized by a severe and often bilateral chronic inflammation of the ocular surface. The diagnosis is generally confirmed by the finding at the ocular examination of conjunctival hyperemia, papillary hypertrophy in the tarsal conjunctiva, giant papillae, papillae in the limbus region.

OBJECTIVE

Aim of this review is to provide an updated overview on the disease focused on clinical grading system, searching papers published in the last decade on VKC in scientific databases.

RESULTS

Currently there are no standardized criteria for diagnosis of VKC and there is no uniformity to define disease severity, which makes difficult to diagnose and treat the disease.

CONCLUSIONS

Given the wide overlap of the symptoms of VKC with the allergic conjunctivitis, criteria of probable, possible or improbable diagnosis are needed, providing pediatricians with parameters useful for deciding whether to drive the patient to the ophthalmologist for diagnostic confirmation.

Distinct transcriptomic profiles of early-onset atopic dermatitis in blood and skin of pediatric patients

BACKGROUND

Atopic dermatitis (AD) predominantly affects young children, but our understanding of AD pathogenesis is based on skin and blood samples from long-standing adult AD. Genomic biopsy profiling from early pediatric AD showed significant Th2 and Th17/Th22-skewing, without the characteristic adult Th1 up-regulation. Because obtaining pediatric biopsies is difficult, blood gene expression profiling may provide a surrogate for the pediatric skin signature.

OBJECTIVE

To define the blood profile and associated biomarkers of early moderate-to-severe pediatric AD.

METHODS

We compared microarrays and reverse transcription polymerase chain reaction (RT-PCR) of blood cells from 28 AD children (<5 years and within 6 months of disease onset) to healthy control blood cells. Differentially expressed genes (DEGs) in blood (fold change [FCH] > 1.2 and false discovery rate [FDR] < 0.05) were then compared with skin DEGs.

RESULTS

Eosinophil and Th2 markers (IL5RA, IL1RL1/ST2, HRH4, CCR3, SIGLEC8, PRSS33, CLC from gene arrays; IL13/IL4/CCL22 from RT-PCR) were up-regulated in early pediatric AD blood, whereas IFNG/Th1 was decreased. Th1 markers were negatively correlated with clinical severity (EASI, pruritus, transepidermal water loss [TEWL]), whereas Th2/Th17-induced interleukin (IL)-19 was positively correlated with SCORAD. Although a few RT-PCR-defined immune markers (IL-13/CCL22) were increased in blood, as previously also reported for skin, minimal overlap based on gene array DEGs was seen.

CONCLUSION

The whole blood signature of early moderate-to-severe pediatric AD blood cells show predominantly a Th2/eosinophil profile; however, markers largely differ from the skin profile. Given their complementarity, pooling of biomarkers from blood and skin may improve profiling and predictions, providing insight regarding disease course, allergic comorbidity development, and response to systemic medications.