The role of complement in the diagnosis and management of allergic rhinitis and allergic asthma

Advances in the pharmacotherapeutic management of eosinophilic granulomatosis with polyangiitis

INTRODUCTION

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare but potentially lethal systemic vasculitis. Only a few prospective therapeutic trials had been conducted in EGPA, and its treatment was mostly adapted from other vasculitides. Monoclonal antibodies inhibiting various pathways (e.g. interleukin-5 [IL5] or B cells) have been investigated.

AREAS COVERED

Published studies on treatments for EGPA using glucocorticoids, conventional immunosuppressants (such as cyclophosphamide or azathioprine), antiIL5 pathway agents (mepolizumab, approved by the Food and Drug Administration (FDA) and European Medicines Agency (EMA) for EGPA; benralizumab and reslizumab), other and future possible treatments [PubMed search, 01/1990-02/2023] are reviewed.

EXPERT OPINION

With advances made in the pharmacotherapeutic management of EGPA, the prognosis has gradually shifted from a potentially fatal to a more chronic course, for which more targeted and safer treatments can be used. However, glucocorticoids remain central. Rituximab is now a possible alternative to cyclophosphamide for induction, although data are still limited. AntiIL5 pathway therapies have been shown to be safe and effective in relapsing patients with EGPA, who often experience asthma and/or ears, nose, and throat (ENT) manifestations, but long-term data are needed. Treatment strategies need to be optimized based on individual patient characteristics, likely with sequential, combination-based approaches, while topical airway treatments should not be forgotten.

Age-related macular degeneration and premorbid allergic diseases: a population-based case-control study

Evidence indicates that age-related macular degeneration (AMD) is associated with the prior presence of allergic diseases; however, large-scale studies in the literature are limited. A case-control study was conducted to describe the relationship between premorbid allergic diseases and AMD using Taiwan's National Health Insurance database. Eligibility criteria for inclusion of new adult AMD cases from 2000 to 2013 were set up. We defined the year of diagnosis as the index year. Age-, gender-, index year- matched controls who were drawn from the same database. The case control ratio was 1:4. For all participants, all premorbid conditions staring 1996 to index year were documented. Binary logistic regression was used to describe factors related to AMD occurrence. The AMD group consisted of 10,911 patients, and the comparison group consisted of 43,644 individuals. Patients with AMD showed significant associations with premorbid allergic diseases (aOR 1.54, 95% CI 1.47-1.61), specifically with allergic conjunctivitis (aOR 2.07, 95% CI 1.94-2.20), allergic rhinitis (aOR 1.32, 95% CI 1.25-1.39), asthma (aOR 0.99, 95% CI 0.93-1.06), and atopic dermatitis (aOR 1.04, 95% CI 0.94-1.17). Further analyses indicated that patients with more concurrent allergic diseases have higher associations with AMD than those with fewer concurrent diseases. Patients with more annual medical visits for their allergic diseases also showed higher associations with AMD than those with fewer visits. AMD is significantly associated with premorbid allergic diseases. The underlying mechanisms must be further investigated.

Nasal mucus proteome and its involvement in allergic rhinitis

Introduction: Nasal mucus is the first line defense barrier against various pathogens including allergens. Proteins in nasal mucus maybe used as biomarkers for diagnosis or future therapeutic strategies. Proteomics opens the possibility to investigate whole human proteomes.

Areas Covered: We aimed to analyze the existing literature on nasal mucus and nasal secretions proteomic approaches especially in allergic rhinitis. A PubMed/Medline search was conducted entering the following keywords and combinations: “nasal mucus”, “nasal lavage fluid,” nasal secretions,” “nasal swabs,” “allergic rhinitis,” ”proteins,” and “proteomics.”

Expert opinion: The majority of studies focus on single proteins or protein groups mainly using ELISA techniques. Four studies met the criteria using mass spectrometry in the analysis of nasal mucus proteomes in rhinologic diseases. In these studies, 7, 35, 267, and 430 proteins were identified, respectively. These four studies are discussed in this review and put in relation to seven other proteomic studies that focus on nasal lavage fluid and nasal secretions obtained by swabs or filter paper. To put it in a nutshell, proteomics facilitates the investigation of the nasal secretome and its role in healthy and diseased state and as potential biomarkers for new diagnostic or therapeutic approaches.

Complement regulatory protein CD46 induces autophagy against oxidative stress-mediated apoptosis in normal and asthmatic airway epithelium

Autophagy plays a major role in defending against oxidative stress in respiratory epithelial cells. The complement regulatory protein CD46 can enhance autophagy and decrease local complement activation at sites of inflammation. This study investigated the mechanism by which CD46 protects against oxidative stress-mediated apoptosis in respiratory epithelium in asthmatic patients. Nasal mucosa samples were obtained from 60 adults with mild asthma who received turbinectomy and 30 controls. A decreased expression of CD46 and increased apoptosis were noted in the damaged nasal epithelium from the asthmatic patients. Primary epithelial cells cultured with Dermatophagoides pteronyssinus 2 showed decreased CD46 and increased cleaved CASPASE-3A expressions. Crosslinking CD46 mAb could induce the formation of autophagosomes and LC3-II expression in primary epithelial cells. CD46 engagement could induce autophagy against hydrogen peroxide-induced epithelial cell death, whereas the autophagy inhibitor 3-methyladenine decreased this effect. In addition, CD46 engagement decreased the expressions of PRO-IL-1β and NLRP3, enhanced the expression of scaffold protein GOPC, and diminished hydrogen peroxide-induced 8-OHdG, IL-1β and IL-6 production. Silencing ATG5 in human lung epithelial A549 cells decreased CD46-activated autophagy with LC3-II. CD46 induced autophagy and decreased the oxidative stress-mediated apoptosis of respiratory epithelium, and this may offer a new therapeutic strategy to treat asthma.

Unexpected Roles for Intracellular Complement in the Regulation of Th1 Responses

The complement system is generally recognized as an evolutionarily ancient and critical part of innate immunity required for the removal of pathogens that have breached the protective host barriers. It was originally defined as a liver-derived serum surveillance system that induces the opsonization and killing of invading microbes and amplifies the general inflammatory reactions. However, studies spanning the last four decades have established complement also as a vital bridge between innate and adaptive immunity. Furthermore, recent work on complement, and in particular its impact on human T helper 1 (Th1) responses, has led to the unexpected findings that the complement system also functions within cells and that it participates in the regulation of basic processes of the cell, including metabolism. These recent new insights into the unanticipated noncanonical activities of this ancient system suggest that the functions of complement extend well beyond mere host protection and into cellular physiology.

The "ins and outs" of complement-driven immune responses

The complement system represents an evolutionary old and critical component of innate immunity where it forms the first line of defense against invading pathogens. Originally described as a heat-labile fraction of the serum responsible for the opsonization and subsequent lytic killing of bacteria, work over the last century firmly established complement as a key mediator of the general inflammatory response but also as an acknowledged vital bridge between innate and adaptive immunity. However, recent studies particularly spanning the last decade have provided new insights into the novel modes and locations of complement activation and highlighted unexpected additional biological functions for this ancient system, for example, in regulating basic processes of the cell. In this review, we will cover the current knowledge about complement's established and novel roles in innate and adaptive immunity with a focus on the functional differences between serum circulating and intracellularly active complement and will describe and discuss the newly discovered cross-talks of complement with other cell effector systems particularly during T-cell induction and contraction.

Th17 response and its regulation in inflammatory upper airway diseases

Allergic rhinitis (AR) and chronic rhinosinusitis (CRS) are two widely prevalent inflammatory diseases in the upper airways. T cell immunity has been suggested to play an important pathogenic role in many chronic inflammatory diseases including inflammatory upper airway diseases. Inappropriate CD4(+) T cell responses, especially the dysregulation of the Th1/Th2 balance leading to excessive Th1 or Th2 cell activation, have been associated with allergic rhinitis and chronic rhinosinusitis. Nevertheless, recent studies suggest that IL-17A and IL-17A-producing Th17 cell subset, a distinct pro-inflammatory CD4(+) T cell lineage, may also play an important role in the pathophysiology of inflammatory upper airway diseases. Th17 cells may promote both eosinophilic and neutrophilic inflammation in AR and CRS. In addition, a few, but accumulating evidence shows that the Th17 responses can be tightly regulated by endogenous and exogenous substances in the context of AR and CRS. This review discusses recent advances in our understanding of the expression and function of the Th17 response and its regulation in inflammatory upper airway diseases, and the perspective for future investigation and clinical utility.

Human T cell derived, cell-bound complement iC3b is integrally involved in T cell activation

Although the complement system is thought to be mainly involved in innate immunity and in the humoral arm of adaptive responses, evidence implicating that complement impacts T cell responses are accumulating recently. The role of the various activation products of the major complement component C3 were mainly studied so far in animal systems, and investigations regarding the effect of different C3-fragments on human T cells are sparse. Here we show that anti-CD3 activated human T lymphocytes derived from the blood and tonsil of healthy individuals produce C3, and the major cleavage fragment that appears on the T cell surface is iC3b. Based on studies carried out in allogenic system we demonstrate that the T cell membrane bound iC3b binds to the CR3 and probably to CR4 receptors expressed on monocyte-derived dendritic cells, and this interaction leads to significantly enhanced T-cell proliferation. Since neither C3aR and nor C3a binding could be detected on the membrane of anti-CD3 activated T cells, our findings indicate that in humans – in contrast to mice – the C3a peptide is most probably not involved directly in the T cell activation process.