Tear N-glycomics in vernal and atopic keratoconjunctivitis

Diagnostic Challenges of Ocular Rosacea

OBJECTIVE

This study aims to address the issues surrounding the diagnosis of ocular rosacea and to evaluate the development of the patients’ condition after treatment, as well as to distinguish between healthy and diseased patients using a glycomic analysis of tears.

METHODOLOGY

A prospective study was conducted to assess a total of 68 eyes in 34 patients over a six-week period. These patients were diagnosed with ocular rosacea based on subjective symptoms and clinical examination. The study monitored the development of objective and subjective values. The difference between patients with the pathology and healthy controls was established by means of analysis of glycans in tears.

RESULTS

Skin lesions were diagnosed in 94% of patients with ocular rosacea, with the most commonly observed phenotype being erythematotelangiectatic (68.8%). The mean duration of symptoms was 29.3 months (range 0.5–126 months) with a median of 12 months. Throughout the study, an improvement in all monitored parameters was observed, including Meibomian gland dysfunction, bulbar conjunctival hyperemia, telangiectasia of the eyelid margin, anterior blepharitis, uneven and reddened eyelid margins, and corneal neovascularization. The study also observed improvements in subjective manifestations of the disease, such as foreign body sensation, burning, dryness, lachrymation, itching eyes, photophobia, and morning discomfort. The analysis of glycans in tears partially separated tear samples based on their origin, which allowed for the differentiation of patients with rosacea from healthy controls. In the first sample, the pathology was determined in a total of 63 eyes (98.4%) of 32 patients, with further samples showing a change in the glycomic profile of patients’ tears during treatment.

CONCLUSION

The study demonstrated objective and subjective improvements in all the patients. Tear sampling and analysis could provide a means of timely diagnosis of ocular rosacea.

Diagnostic criteria of chronic conjunctivitis: atopic keratoconjunctivitis and vernal keratoconjunctivitis

PURPOSE OF REVIEW

Chronic ocular allergies, vernal (VKC) and atopic keratoconjunctivitis (AKC) are relatively rare conditions that require definite diagnostic criteria to the most appropriate therapeutical approach.

RECENT FINDINGS

The diagnosis of both VKC and AKC is generally based on clinical history, signs and symptoms, and the results of allergic tests, which allow to identify the different diseases phenotypes. However, other subtypes of the two diseases and/or overlaps may occur making the diagnosis non always so clear, such as VKC and AKC overlaps or adult-like VKC disease. Each of these phenotypes may be sustained by different mechanisms which are still not well defined but not only related to a type 2 inflammation. The further challenges will be to correlate clinical or molecular biomarkers to a single subtype or disease severity.

SUMMARY

Definite criteria of chronic allergies will further guide to more specific therapeutical approaches.

Vernal Keratoconjunctivitis: A Systematic Review

Vernal keratoconjunctivitis (VKC) is a chronic, bilateral corneal and conjunctival problem which typically presents in young individuals. VKC is characterized by itching, photophobia, white mucous discharge, lacrimation, foreign body sensation, and pain due to corneal involvement of shield ulcers. Vernal keratoconjunctivitis is categorized within ocular diseases. The diagnosis is clinical, as no sure biomarkers pathognomonic of the disease have yet been identified. The VKC therapy relies on different types of drugs, from antihistamines and topical steroids to cyclosporine or tacrolimus eye drops. In extremely rare cases, there is also the need for surgical treatment for the debridement of ulcers, as well as for advanced glaucoma and cataracts, caused by excessive prolonged use of steroid eye drops. We performed a systematic review of the literature, according to PRISMA guideline recommendations. We searched the PubMed database from January 2016 to June 2023. Search terms were Vernal, Vernal keratoconjunctivitis, and VKC. We initially identified 211 articles. After the screening process, 168 studies were eligible according to our criteria and were included in the review. In this study, we performed a systematic literature review to provide a comprehensive overview of currently available diagnostic methods, management of VKC, and its treatments.

The protective role of conjunctival goblet cell mucin sialylation

Gel-forming mucins secreted by conjunctival goblet cells have been implicated in the clearance of allergens, pathogens, and debris. However, their roles remain incompletely understood. Here we show that human and mouse conjunctival goblet cell mucins have Alcian blue-detectable sialic acids, but not sulfates in the steady state. Interestingly, Balb/c mouse strain lacks this sialylation due to a point mutation in a sialyltransferase gene, St6galnac1, which is responsible for sialyl-Tn synthesis. Introduction of intact St6galnac1 to Balb/c restores the sialylation of conjunctival goblet cell mucus. Sialylated mucus efficiently captures and encapsulates the allergen particles in an impenetrable layer, leading to the protection of mice from the development of allergic conjunctivitis. Expression of ST6GALNAC1 and sialyl-Tn is upregulated in humans under conditions with chronic stimuli. These results indicate that the sialylated glycans on the ocular mucins play an essential role in maintaining the conjunctival mucosa by protecting from the incoming foreign bodies such as allergen particles.

Lectin-Based Affinity Enrichment and Characterization of N-Glycoproteins from Human Tear Film by Mass Spectrometry

The glycosylation of proteins is one of the most common post-translational modifications (PTMs) and plays important regulatory functions in diverse biological processes such as protein stability or cell signaling. Accordingly, glycoproteins are also a consistent part of the human tear film proteome, maintaining the proper function of the ocular surface and forming the first defense barrier of the ocular immune system. Irregularities in the glycoproteomic composition of tear film might promote the development of chronic eye diseases, indicating glycoproteins as a valuable source for biomarker discovery or drug target identification. Therefore, the present study aimed to develop a lectin-based affinity method for the enrichment and concentration of tear glycoproteins/glycopeptides and to characterize their specific N-glycosylation sites by high-resolution mass spectrometry (MS). For method development and evaluation, we first accumulated native glycoproteins from human tear sample pools and assessed the enrichment efficiency of different lectin column systems by 1D gel electrophoresis and specific protein stainings (Coomassie and glycoproteins). The best-performing multi-lectin column system (comprising the four lectins ConA, JAC, WGA, and UEA I, termed 4L) was applied to glycopeptide enrichment from human tear sample digests, followed by MS-based detection and localization of their specific N-glycosylation sites. As the main result, our study identified a total of 26 N glycosylation sites of 11 N-glycoproteins in the tear sample pools of healthy individuals (n = 3 biological sample pools). Amongst others, we identified tear film proteins lactotransferrin (N497 and N642, LTF), Ig heavy chain constant α-1 (N144 and 340, IGHA1), prolactin-inducible protein (N105, PIP), and extracellular lacritin (N105, LACRT) as highly reliable and significant N glycoproteins, already associated with the pathogenesis of various chronic eye diseases such as dry eye syndrome (DES). In conclusion, the results of the present study will serve as an important tear film N-glycoprotein catalog for future studies focusing on human tear film and ocular surface-related inflammatory diseases.

Omics technologies in allergy and asthma research: An EAACI position paper

Allergic diseases and asthma are heterogenous chronic inflammatory conditions with several distinct complex endotypes. Both environmental and genetic factors can influence the development and progression of allergy. Complex pathogenetic pathways observed in allergic disorders present a challenge in patient management and successful targeted treatment strategies. The increasing availability of high-throughput omics technologies, such as genomics, epigenomics, transcriptomics, proteomics, and metabolomics allows studying biochemical systems and pathophysiological processes underlying allergic responses. Additionally, omics techniques present clinical applicability by functional identification and validation of biomarkers. Therefore, finding molecules or patterns characteristic for distinct immune-inflammatory endotypes, can subsequently influence its development, progression, and treatment. There is a great potential to further increase the effectiveness of single omics approaches by integrating them with other omics, and nonomics data. Systems biology aims to simultaneously and longitudinally understand multiple layers of a complex and multifactorial disease, such as allergy, or asthma by integrating several, separated data sets and generating a complete molecular profile of the condition. With the use of sophisticated biostatistics and machine learning techniques, these approaches provide in-depth insight into individual biological systems and will allow efficient and customized healthcare approaches, called precision medicine. In this EAACI Position Paper, the Task Force "Omics technologies in allergic research" broadly reviewed current advances and applicability of omics techniques in allergic diseases and asthma research, with a focus on methodology and data analysis, aiming to provide researchers (basic and clinical) with a desk reference in the field. The potential of omics strategies in understanding disease pathophysiology and key tools to reach unmet needs in allergy precision medicine, such as successful patients' stratification, accurate disease prognosis, and prediction of treatment efficacy and successful prevention measures are highlighted.

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.

Epithelial barrier dysfunction in ocular allergy

The epithelial barrier is the first line of defense that forms a protective barrier against pathogens, pollutants, and allergens. Epithelial barrier dysfunction has been recently implicated in the development of allergic diseases such as asthma, atopic dermatitis, food allergy, and rhinitis. However, there is limited knowledge on epithelial barrier dysfunction in ocular allergy (OA). Since the ocular surface is directly exposed to the environment, it is important to understand the role of ocular epithelia and their dysfunction in OA. Impaired epithelial barrier enhances allergen uptake, which lead to activation of immune responses and development of chronic inflammation as seen in allergies. Abnormal expression of tight junction proteins that helps to maintain epithelial integrity has been reported in OA but sufficient data not available in chronic atopic (AKC) and vernal keratoconjunctivitis (VKC), the pathophysiology of which is not just complex, but also the current treatments are not completely effective. This review provides an overview of studies, which indicates the role of barrier dysfunction in OA, and highlights how ocular barrier dysfunction possibly contributes to the disease pathogenesis. The review also explores the potential of ocular epithelial barrier repair strategies as preventive and therapeutic approach.

N-Glycosylation Patterns across the Age-Related Macular Degeneration Spectrum

The pathogenesis of age-related macular degeneration (AMD) remains elusive, despite numerous research studies. Therefore, we aimed to investigate the changes of plasma and IgG-specific N-glycosylation across the disease severity spectrum. We examined 2835 subjects from the 10.001 Dalmatians project, originating from the isolated Croatian islands of Vis and Korčula. All subjects were classified into four groups, namely (i) bilateral AMD, (ii) unilateral AMD, (iii) early-onset drusen, and (iv) controls. We analysed plasma and IgG N-glycans measured by HPLC and their association with retinal fundus photographs. There were 106 (3.7%) detected cases of AMD; 66 of them were bilateral. In addition, 45 (0.9%) subjects were recorded as having early-onset retinal drusen. We detected several interesting differences across the analysed groups, suggesting that N-glycans can be used as a biomarker for AMD. Multivariate analysis suggested a significant decrease in the immunomodulatory bi-antennary glycan structures in unilateral AMD (adjusted odds ratio 0.43 (95% confidence interval 0.22–0.79)). We also detected a substantial increase in the pro-inflammatory tetra-antennary plasma glycans in bilateral AMD (7.90 (2.94–20.95)). Notably, some of these associations were not identified in the aggregated analysis, where all three disease stages were collapsed into a single category, suggesting the need for better-refined phenotypes and the use of disease severity stages in the analysis of more complex diseases. Age-related macular degeneration progression is characterised by the complex interplay of various mechanisms, some of which can be detected by measuring plasma and IgG N-glycans. As opposed to a simple case-control study, more advanced and refined study designs are needed to understand the pathogenesis of complex diseases.