Dendritic Cells and Their Role in Allergy: Uptake, Proteolytic Processing and Presentation of Allergens

Cellular metabolism and hypoxia interfacing with allergic diseases

Allergic diseases display significant heterogeneity in their pathogenesis. Understanding the influencing factors, pathogenesis, and advancing new treatments for allergic diseases is becoming more and more vital as currently, prevalence continues to rise, and mechanisms of allergic diseases are not fully understood. The upregulation of the hypoxia response is linked to an elevated infiltration of activated inflammatory cells, accompanied by elevated metabolic requirements. An enhanced hypoxia response may potentially contribute to inflammation, remodeling, and the onset of allergic diseases. It has become increasingly clear that the process underlying immune and stromal cell activation during allergic sensitization requires well-tuned and dynamic changes in cellular metabolism. The purpose of this review is to examine current perspectives regarding metabolic dysfunction in allergic diseases. In the past decade, new technological platforms such as "omic" techniques have been applied, allowing for the identification of different biomarkers in multiple models ranging from altered lipid species content, increased nutrient transporters, and altered serum amino acids in various allergic diseases. Better understanding, recognition, and integration of these alterations would increase our knowledge of pathogenesis and potentially actuate a novel repertoire of targeted treatment approaches that regulate immune metabolic pathways.

To stay or not to stay intact as an allergen: the endolysosomal degradation assay used as tool to analyze protein immunogenicity and T cell epitopes

Antigen uptake and processing of exogenous proteins is critical for adaptive immunity, particularly for T helper cell activation. Proteins undergo distinct proteolytic processing in endolysosomal compartments of antigen-presenting cells. The resulting peptides are presented on MHC class II molecules and specifically recognized by T cells. The in vitro endolysosomal degradation assay mimics antigen processing by incubating a protein of interest with a protease cocktail derived from the endolysosomal compartments of antigen presenting cells. The kinetics of protein degradation is monitored by gel electrophoresis and allows calculation of a protein's half-life and thus endolysosomal stability. Processed peptides are analyzed by mass spectrometry and abundant peptide clusters are shown to harbor T cell epitopes. The endolysosomal degradation assay has been widely used to study allergens, which are IgE-binding proteins involved in type I hypersensitivity. In this review article, we provide the first comprehensive overview of the endolysosomal degradation of 29 isoallergens and variants originating from the PR-10, Ole e 1-like, pectate lyase, defensin polyproline-linked, non-specific lipid transfer, mite group 1, 2, and 5, and tropomyosin protein families. The assay method is described in detail and suggestions for improved standardization and reproducibility are provided. The current hypothesis implies that proteins with high endolysosomal stability can induce an efficient immune response, whereas highly unstable proteins are degraded early during antigen processing and therefore not efficient for MHC II peptide presentation. To validate this concept, systematic analyses of high and low allergenic representatives of protein families should be investigated. In addition to purified molecules, allergen extracts should be degraded to analyze potential matrix effects and gastrointestinal proteolysis of food allergens. In conclusion, individual protein susceptibility and peptides obtained from the endolysosomal degradation assay are powerful tools for understanding protein immunogenicity and T cell reactivity. Systematic studies and linkage with in vivo sensitization data will allow the establishment of (machine-learning) tools to aid prediction of immunogenicity and allergenicity. The orthogonal method could in the future be used for risk assessment of novel foods and in the generation of protein-based immunotherapeutics.

Dietary Polyphenols, Plant Metabolites, and Allergic Disorders: A Comprehensive Review

Given the ongoing rise in the occurrence of allergic disorders, alterations in dietary patterns have been proposed as a possible factor contributing to the emergence and progression of these conditions. Currently, there is a significant focus on the development of dietary therapies that utilize natural compounds possessing anti-allergy properties. Dietary polyphenols and plant metabolites have been intensively researched due to their well-documented anti-inflammatory, antioxidant, and immunomodulatory characteristics, making them one of the most prominent natural bioactive chemicals. This study seeks to discuss the in-depth mechanisms by which these molecules may exert anti-allergic effects, namely through their capacity to diminish the allergenicity of proteins, modulate immune responses, and modify the composition of the gut microbiota. However, further investigation is required to fully understand these effects. This paper examines the existing evidence from experimental and clinical studies that supports the idea that different polyphenols, such as catechins, resveratrol, curcumin, quercetin, and others, can reduce allergic inflammation, relieve symptoms of food allergy, asthma, atopic dermatitis, and allergic rhinitis, and prevent the progression of the allergic immune response. In summary, dietary polyphenols and plant metabolites possess significant anti-allergic properties and can be utilized for developing both preventative and therapeutic strategies for targeting allergic conditions. The paper also discusses the constraints in investigating and broad usage of polyphenols, as well as potential avenues for future research.

Long-chain acyl-CoA synthetase 4-mediated mitochondrial fatty acid metabolism and dendritic cell antigen presentation

OBJECTIVE

This study aims to investigate the role of Acyl-CoA synthetase 4 (ACSL4) in mediating mitochondrial fatty acid metabolism and dendritic cell (DC) antigen presentation in the immune response associated with asthma.

METHODS

RNA sequencing was employed to identify key genes associated with mitochondrial function and fatty acid metabolism in DCs. ELISA was employed to assess the levels of fatty acid metabolism in DCs. Mitochondrial morphology was evaluated using laser confocal microscopy, structured illumination microscopy, and transmission electron microscopy. Flow cytometry and immunofluorescence were utilized to detect changes in mitochondrial superoxide generation in DCs, followed by immunofluorescence co-localization analysis of ACSL4 and the mitochondrial marker protein COXIV. Subsequently, pathological changes and immune responses in mouse lung tissue were observed. ELISA was conducted to measure the levels of fatty acid metabolism in lung tissue DCs. qRT-PCR and western blotting were employed to respectively assess the expression levels of mitochondrial-associated genes (ATP5F1A, VDAC1, COXIV, TFAM, iNOS) and proteins (ATP5F1A, VDAC1, COXIV, TOMM20, iNOS) in lung tissue DCs. Flow cytometry was utilized to analyze changes in the expression of surface antigens presented by DCs in lung tissue, specifically the MHCII molecule and the co-stimulatory molecules CD80/86.

RESULTS

The sequencing results reveal that ACSL4 is a crucial gene regulating mitochondrial function and fatty acid metabolism in DCs. Inhibiting ACSL4 reduces the levels of fatty acid oxidases in DCs, increases arachidonic acid levels, and decreases A-CoA synthesis. Simultaneously, ACSL4 inhibition leads to an increase in mitochondrial superoxide production (MitoSOX) in DCs, causing mitochondrial rupture, vacuolization, and sparse mitochondrial cristae. In mice, ACSL4 inhibition exacerbates pulmonary pathological changes and immune responses, reducing the fatty acid metabolism levels within lung tissue DCs and the expression of mitochondria-associated genes and proteins. This inhibition induces an increase in the expression of MHCII antigen presentation molecules and co-stimulatory molecules CD80/86 in DCs.

CONCLUSIONS

The research findings indicate that ACSL4-mediated mitochondrial fatty acid metabolism and dendritic cell antigen presentation play a crucial regulatory role in the immune response of asthma. This discovery holds promise for enhancing our understanding of the mechanisms underlying asthma pathogenesis and potentially identifying novel targets for its prevention and treatment.

Exploring the immunopathology of type 2 inflammatory airway diseases

Significant advancements have been achieved in understanding the roles of different immune cells, as well as cytokines and chemokines, in the pathogenesis of eosinophilic airway conditions. This review examines the pathogenesis of Chronic Rhinosinusitis with Nasal Polyps (CRSwNP), marked by complex immune dysregulation, with major contributions from type 2 inflammation and dysfunctional airway epithelium. The presence of eosinophils and the role of T-cell subsets, particularly an imbalance between Treg and Th17 cells, are crucial to the disease's pathogenesis. The review also investigates the pathogenesis of eosinophilic asthma, a unique asthma subtype. It is characterized by inflammation and high eosinophil levels, with eosinophils playing a pivotal role in triggering type 2 inflammation. The immune response involves Th2 cells, eosinophils, and IgE, among others, all activated by genetic and environmental factors. The intricate interplay among these elements, chemokines, and innate lymphoid cells results in airway inflammation and hyper-responsiveness, contributing to the pathogenesis of eosinophilic asthma. Another scope of this review is the pathogenesis of Eosinophilic Granulomatosis with Polyangiitis (EGPA); a complex inflammatory disease that commonly affects the respiratory tract and small to medium-sized blood vessels. It is characterized by elevated eosinophil levels in blood and tissues. The pathogenesis involves the activation of adaptive immune responses by antigens leading to T and B cell activation and eosinophil stimulation, which causes tissue and vessel damage. On the other hand, Allergic Bronchopulmonary Aspergillosis (ABPA) is a hypersensitive response that occurs when the airways become colonized by aspergillus fungus, with the pathogenesis involving activation of Th2 immune responses, production of IgE antibodies, and eosinophilic action leading to bronchial inflammation and subsequent lung damage. This analysis scrutinizes how an imbalanced immune system contributes to these eosinophilic diseases. The understanding derived from this assessment can steer researchers toward designing new potential therapeutic targets for efficient control of these disorders.

Coculture of Human Dendritic and T Cells for the Study of Specific T Cell-Mediated Responses Against Food Allergens

Dendritic cells (DCs) connect innate and adaptive immunity by sampling, capturing, processing, and presenting the allergen to distinct subsets of CD4+ T cells. In food allergy, this process leads to the generation of allergen-specific Th2 responses and the production of type 2 cytokines that ultimately induce the synthesis of IgE by allergen-specific B cells. In this chapter, we have described different protocols for the isolation of circulating DCs as well as the generation of DC-like cells derived from autologous peripheral monocytes and the human monocytic THP-1 cell line. Coculture of isolated/generated DCs with CD4+ T cells obtained from PBMCs of allergic subjects allows the study of antigen-specific T cell immune responses against food allergens. Early responses upon allergen recognition can be determined by the upregulation of activation markers such as CD154 (CD40 ligand) and the detection of type 2 cytokines (IL-4, IL-5, IL-9, and IL-13). Delayed allergen-specific CD4+ T cell responses induce the proliferation of these cells and the accumulation of type 2 cytokines in coculture supernatants that can be quantified by different approaches (ELISA, EllaTM, and multiplex assays). Together, the protocols described in this chapter can be used to investigate the features of food proteins to induce food allergy, the influence of environmental factors to generate Th2-polarization, the function of DCs to generate differential immune responses in allergic versus tolerant individuals, and to assess the immunomodulating properties of potential therapeutic substances.

Antigen cross-presentation in dendric cells: From bench to bedside

Cross-presentation (XPT) is an adaptation of the cellular process in which dendritic cells (DCs) present exogenous antigens on major histocompatibility complex (MHC) class I molecules for recognition of the cytotoxic T lymphocytes (CTL) and natural killer (NK) cells, resulting in immunity or tolerance. Recent advances in DCs have broadened our understanding of the underlying mechanisms of XPT and strengthened their application in tumor immunotherapy. In this review, we summarized the known mechanisms of XPT, including the receptor-mediated internalization of exogenous antigens, endosome escape, engagement of the other XPT-related proteins, and adjuvants, which significantly enhance the XPT capacity of DCs. Consequently, various strategies to enhance XPT can be adopted and optimized to improve outcomes of DC-based therapy.

Clinical Approach to Patients with Moderate-to-Severe Atopic Dermatitis: A Spanish Delphi Consensus

Despite emerging evidence and advances in the management of atopic dermatitis there a lack of consensus regarding the diagnostic criteria, therapeutic approach, method to assess severity, and patient follow-up for this condition. An expert consensus study was conducted to provide recommendations on the management of patients with moderate-to-severe atopic dermatitis. The study used Delphi-like methodology based on a literature review, a summary of the scientific evidence, and a 2-round survey. The agreement of 60 panellists on 21 statements was evaluated. Consensus was pre-defined as ≥ 80% agreement of all respondents. In the first round 6 statements reached consensus. Unanimous consensus was achieved regarding therapeutic goals and patient satisfaction (maintained in the long term and periodic goals reassessment recommended every 3-6 months). In the second round, half of the statements reached consensus, all related to patient follow-up, treatment goals, and atopic comorbidities. The statements that did not reach consensus were related to diagnosis (biomarkers, allergy, and food testing) and starting patients on conventional systemic treatment rather than advanced treatment. The study assessed expert opinion regarding a variety of topics related to the clinical approach to patients with moderate-to-severe atopic dermatitis, in order to provide guidance on the diagnosis and management of patients with atopic dermatitis.

Dietary Polyphenols-Natural Bioactive Compounds with Potential for Preventing and Treating Some Allergic Conditions

In light of the constantly increasing prevalence of allergic diseases, changes in dietary patterns have been suggested as a plausible environmental explanation for the development and progression of these diseases. Nowadays, much attention has been paid to the development of dietary interventions using natural substances with anti-allergy activities. In this respect, dietary polyphenols have been studied extensively as one of the most prominent natural bioactive compounds with well-documented anti-inflammatory, antioxidant, and immunomodulatory properties. This review aims to discuss the mechanisms underlying the potential anti-allergic actions of polyphenols related to their ability to reduce protein allergenicity, regulate immune response, and gut microbiome modification; however, these issues need to be elucidated in detail. This paper reviews the current evidence from experimental and clinical studies confirming that various polyphenols such as quercetin, curcumin, resveratrol, catechins, and many others could attenuate allergic inflammation, alleviate the symptoms of food allergy, asthma, and allergic rhinitis, and prevent the development of allergic immune response. Conclusively, dietary polyphenols are endowed with great anti-allergic potential and therefore could be used either for preventive approaches or therapeutic interventions in relation to allergic diseases. Limitations in studying and widespread use of polyphenols as well as future research directions are also discussed.

Increased dendritic cell density and altered morphology in allergic conjunctivitis

BACKGROUND

Corneal and conjunctival epithelial dendritic cells (DC) have an established role in vernal keratoconjunctivitis, however, their role in more prevalent forms of allergic eye disease remains unclear. This study evaluated corneal and conjunctival epithelial DC density, morphology, and distribution observed using in vivo confocal microscopy (IVCM) in allergic conjunctivitis.

METHODS

In this prospective, observational study, 66 participants (mean age 36.6 ± 12.0 years, 56% female): 33 with allergic conjunctivitis and 33 controls were recruited. IVCM was performed at the corneal centre, inferior whorl, corneal periphery, corneal limbus, and temporal bulbar conjunctiva. DC were counted and their morphology was assessed as follows: largest cell body size, presence of dendrites, and presence of long and thick dendrites. Mixed model analysis (DC density) and non-parametric tests (DC morphology) were used.

RESULTS

DC density was higher in allergic participants at all locations (p ≤ 0.01), (corneal centre median (IQR) 21.9 (8.7-50.9) cells/mm2 vs 13.1 (2.8-22.8) cells/mm2; periphery 37.5 (15.6-67.2) cells/mm2 vs 20 (9.4-32.5) cells/mm2; limbus 75 (60-120) cells/mm2 vs 58.1 (44.4-66.2) cells/mm2; conjunctiva 10 (0-54.4) cells/mm2 vs 0.6 (0-5.6) cells/mm2, but not at the inferior whorl 21.9 (6.2-34.4) cells/mm2 vs 12.5 (1.9-37.5) cells/mm2, p = 0.20. At the corneal centre, allergic participants had larger DC bodies (p = 0.02), a higher proportion of DC with dendrites (p = 0.02) and long dendrites (p = 0.003) compared to controls.

CONCLUSIONS

Corneal and conjunctival DC density was increased, and morphology altered in allergic conjunctivitis. These findings imply that the ocular surface immune response was upregulated and support an increased antigen-capture capacity of DC in allergic conjunctivitis.

Multiple Vaccines and Strategies for Pandemic Preparedness of Avian Influenza Virus

Avian influenza viruses (AIV) are a continuous cause of concern due to their pandemic potential and devasting effects on poultry, birds, and human health. The low pathogenic avian influenza virus has the potential to evolve into a highly pathogenic avian influenza virus, resulting in its rapid spread and significant outbreaks in poultry. Over the years, a wide array of traditional and novel strategies has been implemented to prevent the transmission of AIV in poultry. Mass vaccination is still an economical and effective approach to establish immune protection against clinical virus infection. At present, some AIV vaccines have been licensed for large-scale production and use in the poultry industry; however, other new types of AIV vaccines are currently under research and development. In this review, we assess the recent progress surrounding the various types of AIV vaccines, which are based on the classical and next-generation platforms. Additionally, the delivery systems for nucleic acid vaccines are discussed, since these vaccines have attracted significant attention following their significant role in the fight against COVID-19. We also provide a general introduction to the dendritic targeting strategy, which can be used to enhance the immune efficiency of AIV vaccines. This review may be beneficial for the avian influenza research community, providing ideas for the design and development of new AIV vaccines.

Eosinophilic Airway Diseases: From Pathophysiological Mechanisms to Clinical Practice

Eosinophils play a key role in airway inflammation in many diseases, such as allergic and non-allergic asthma, chronic rhinosinusitis with nasal polyps, and chronic obstructive pulmonary disease. In these chronic disabling conditions, eosinophils contribute to tissue damage, repair, remodeling, and disease persistence through the production a variety of mediators. With the introduction of biological drugs for the treatment of these respiratory diseases, the classification of patients based on clinical characteristics (phenotype) and pathobiological mechanisms (endotype) has become mandatory. This need is particularly evident in severe asthma, where, despite the great scientific efforts to understand the immunological pathways underlying clinical phenotypes, the identification of specific biomarkers defining endotypes or predicting pharmacological response remains unsatisfied. In addition, a significant heterogeneity also exists among patients with other airway diseases. In this review, we describe some of the immunological differences in eosinophilic airway inflammation associated with severe asthma and other airway diseases and how these factors might influence the clinical presentation, with the aim of clarifying when eosinophils play a key pathogenic role and, therefore, represent the preferred therapeutic target.

C-Type Lectin Receptor Mediated Modulation of T2 Immune Responses to Allergens

PURPOSE OF REVIEW

Allergic diseases represent a major health problem of increasing prevalence worldwide. In allergy, dendritic cells (DCs) contribute to both the pathophysiology and the induction of healthy immune responses to the allergens. Different studies have reported that some common allergens contain glycans in their structure. C-type lectin receptors (CLRs) expressed by DCs recognize carbohydrate structures and are crucial in allergen uptake, presentation, and polarization of T cell responses. This review summarizes the recent literature regarding the role of CLRs in the regulation of type 2 immune responses to allergens.

RECENT FINDINGS

In this review, we highlight the capacity of CLRs to recognize carbohydrates in common allergens triggering different signaling pathways involved in the polarization of CD4⁺ T cells towards specific Th2 responses. Under certain conditions, specific CLRs could also promote tolerogenic responses to allergens, which might well be exploited to develop novel therapeutic approaches of allergen-specific immunotherapy (AIT), the single treatment with potential disease-modifying capacity for allergic disease. At this regard, polymerized allergens conjugated to non-oxidized mannan (allergoid-mannan conjugated) are next-generation vaccines targeting DCs via CLRs that promote regulatory T cells, thus favoring allergen tolerance both in preclinical models and clinical trials. A better understanding of the role of CLRs in the development of allergy and in the induction of allergen tolerance might well pave the way for the design of novel strategies for allergic diseases.

Epicutaneous Sensitization and Food Allergy: Preventive Strategies Targeting Skin Barrier Repair-Facts and Challenges

Food allergy represents a growing public health and socio-economic problem with an increasing prevalence over the last two decades. Despite its substantial impact on the quality of life, current treatment options for food allergy are limited to strict allergen avoidance and emergency management, creating an urgent need for effective preventive strategies. Advances in the understanding of the food allergy pathogenesis allow to develop more precise approaches targeting specific pathophysiological pathways. Recently, the skin has become an important target for food allergy prevention strategies, as it has been hypothesized that allergen exposure through the impaired skin barrier might induce an immune response resulting in subsequent development of food allergy. This review aims to discuss current evidence supporting this complex interplay between the skin barrier dysfunction and food allergy by highlighting the crucial role of epicutaneous sensitization in the causality pathway leading to food allergen sensitization and progression to clinical food allergy. We also summarize recently studied prophylactic and therapeutic interventions targeting the skin barrier repair as an emerging food allergy prevention strategy and discuss current evidence controversies and future challenges. Further studies are needed before these promising strategies can be routinely implemented as prevention advice for the general population.

Peach extract induces systemic and local immune responses in an experimental food allergy model

Peach allergy is among the most frequent food allergies in the Mediterranean area, often eliciting severe anaphylactic reactions in patients. Due to the risk of severe symptoms, studies in humans are limited, leading to a lack of therapeutic options. This study aimed to develop a peach allergy mouse model as a tool to better understand the pathomechanism and to allow preclinical investigations on the development of optimized strategies for immunotherapy. CBA/J mice were sensitized intraperitoneally with peach extract or PBS, using alum as adjuvant. Afterwards, extract was administered intragastrically to involve the intestinal tract. Allergen provocation was performed via intraperitoneal injection of extract, measuring drop of body temperature as main read out of anaphylaxis. The model induced allergy-related symptoms in mice, including decrease of body temperature. Antibody levels in serum and intestinal homogenates revealed a Th2 response with increased levels of mMCPT-1, peach- and Pru p 3-specific IgE, IgG1 and IgG2a as well as increased levels of IL-4 and IL-13. FACS analysis of small intestine lamina propria revealed increased amounts of T cells, neutrophils and DCs in peach allergic mice. These data suggest the successful establishment of a peach allergy mouse model, inducing systemic as well as local gastrointestinal reactions.

Effect of early postnatal supplementation of newborns with probiotic strain E. coli O83:K24:H31 on allergy incidence, dendritic cells, and microbiota

Introduction

Probiotic administration seems to be a rational approach to promote maturation of the neonatal immune system. Mutual interaction of the microbiota with the host immune system is critical for the setting of appropriate immune responses including a tolerogenic one and thevmaintenance of homeostasis. On the other hand, our knowledge on the modes of actions of probiotics is still scarce.

Methods

In our study, probiotic strain Escherichia coli O83:K24:H31 (EcO83) was administered to neonates of allergic mothers (AMs; neonates with increased risk for allergy development) within 48 h after the delivery, and the impact of this early postnatal supplementation on allergy incidence and selected immune markers has been analyzed 10 years after the primary EcO83 administration.

Results

We have observed decreased allergy incidence in 10-year-old children supplemented with EcO83 (13 of 52 children were allergic) in comparison with non-supplemented children of AMs (16 of 42 children were allergic). The early postnatal EcO83 supplementation appeared to limit the allergy in the high-risk group (children of AMs) compared to that in the low-risk group (children of healthy mothers). Dendritic cells (DCs) in the peripheral blood of EcO83-supplemented children do not differ significantly in cell surface presence of CD83. The immunomodulatory capacity of EcO83 on DCs was tested in vitro as well. Both directly isolated myeloid and in vitro monocyte-derived DCs from cord blood increased CD83 expression together with interleukin (IL)-10 secretion after EcO83 stimulation. The effect of early postnatal EcO83 supplementation on the microbiota composition of 10-year-old children was characterized by next-generation sequencing, and we have not observed significant changes in the microbiota composition of EcO83-supplemented and non-supplemented children at the age of 10 years.

Conclusions

Early postnatal EcO83 supplementation appears to lower allergy incidence in children of AMs. It seems that the beneficial effect of EcO83 is mediated via modulation of DC functional capacities without impacting the microbiota composition. Larger-scale studies will be necessary to confirm these preliminary findings.

Allergy, asthma, and proteomics: opportunities with immediate impact

Allergy is widely discussed by researchers due to its complex mechanism that leads to disorders and injuries, but the reason behind the allergic status remains unclear. Current treatments are insufficient to improve the patient's quality of life significantly. New technologies in scientific and technological development are emerging. For instance, the union between allergy and peptidomics and bioinformatics tools may help fill the gaps in this field, diagnosis, and treatment. In this review, we look at peptidomics and address some findings, such as target proteins or biomarkers that help better understand mechanisms that lead to inflammation, organ damage, and, consequently, poor quality of life or even death.

Aryl hydrocarbon receptor: The master regulator of immune responses in allergic diseases

The aryl hydrocarbon receptor (AhR) is a widely studied ligand-activated cytosolic transcriptional factor that has been associated with the initiation and progression of various diseases, including autoimmune diseases, cancers, metabolic syndromes, and allergies. Generally, AhR responds and binds to environmental toxins/ligands, dietary ligands, and allergens to regulate toxicological, biological, cellular responses. In a canonical signaling manner, activation of AhR is responsible for the increase in cytochrome P450 enzymes which help individuals to degrade and metabolize these environmental toxins and ligands. However, canonical signaling cannot be applied to all the effects mediated by AhR. Recent findings indicate that activation of AhR signaling also interacts with some non-canonical factors like Kruppel-like-factor-6 (KLF6) or estrogen-receptor-alpha (Erα) to affect the expression of downstream genes. Meanwhile, enormous research has been conducted to evaluate the effect of AhR signaling on innate and adaptive immunity. It has been shown that AhR exerts numerous effects on mast cells, B cells, macrophages, antigen-presenting cells (APCs), Th1/Th2 cell balance, Th17, and regulatory T cells, thus, playing a significant role in allergens-induced diseases. This review discussed how AhR mediates immune responses in allergic diseases. Meanwhile, we believe that understanding the role of AhR in immune responses will enhance our knowledge of AhR-mediated immune regulation in allergic diseases. Also, it will help researchers to understand the role of AhR in regulating immune responses in autoimmune diseases, cancers, metabolic syndromes, and infectious diseases.

Nanovaccines against Viral Infectious Diseases

Infectious diseases have always been regarded as one of the greatest global threats for the last century. The current ongoing COVID-19 pandemic caused by SARS-CoV-2 is living proof that the world is still threatened by emerging infectious diseases. Morbidity and mortality rates of diseases caused by Coronavirus have inflicted devastating social and economic outcomes. Undoubtedly, vaccination is the most effective method of eradicating infections and infectious diseases that have been eradicated by vaccinations, including Smallpox and Polio. To date, next-generation vaccine candidates with novel platforms are being approved for emergency use, such as the mRNA and viral vectored vaccines against SARS-CoV-2. Nanoparticle based vaccines are the perfect candidates as they demonstrated targeted antigen delivery, improved antigen presentation, and sustained antigen release while providing self-adjuvanting functions to stimulate potent immune responses. In this review, we discussed most of the recent nanovaccines that have found success in immunization and challenge studies in animal models in comparison with their naked vaccine counterparts. Nanovaccines that are currently in clinical trials are also reviewed.

Effect of trichloroethanol on TLR2 and TLR4/NF-κB-mediated antigen processing and presentation in HLA-B* 13:01-transfected antigen-presenting cells

Trichloroethanol (TCOH), as a metabolite of trichloroethylene, has sensitization in the pathogenesis of trichloroethylene-induced hypersensitivity dermatitis (TIHD) which the human leukocyte antigen (HLA)-B∗13:01 gene is strongly associated with it. However, it is still obscure how TCOH participates in the pathogenesis of TIHD. Here, we demonstrate that TLR2 and TLR4 signaling through MyD88 and TRAF6-dependent pathway could activate NF-κB by promoting degradation of the inhibitor IκB-α to stimulate the process of NF-κB nuclear translocation. Besides, the crucial molecules of antigen processing and presentation, including TAP1, LMP2, LMP7, and HLA-B* 13:01, were all enhanced and the abundance of HLA-B* 13:01 on the surface of CIR-B* 13:01 cells was also up-regulated with the TCOH concentration increasing. Notably, we used 50 μM pyrrolidinedithiocarbamate (ammonium) to effectively inhibit the activation of NF-κB, which could effectively reverse the stimulation of antigen processing and presentation in TCOH-treated CIR-B* 13:01 cells. Taken together, we speculated that TCOH could promote the abundance of HLA complex on the antigen-presenting cells via TLR2 and TLR4/NF-κB to induce the severe reactivation of T lymphocytes, leading to the extreme immune response.

Allergic Inflammation: Effect of Propolis and Its Flavonoids

The incidence of allergic diseases and their complications are increasing worldwide. Today, people increasingly use natural products, which has been termed a "return to nature". Natural products with healing properties, especially those obtained from plants and bees, have been used in the prevention and treatment of numerous chronic diseases, including allergy and/or inflammation. Propolis is a multi-component resin rich in flavonoids, collected and transformed by honeybees from buds and plant wounds for the construction and adaptation of their nests. This article describes the current views regarding the possible mechanisms and multiple benefits of flavonoids in combating allergy and allergy-related complications. These benefits arise from flavonoid anti-allergic, anti-inflammatory, antioxidative, and wound healing activities and their effects on microbe-immune system interactions in developing host responses to different allergens. Finally, this article presents various aspects of allergy pathobiology and possible molecular approaches in their treatment. Possible mechanisms regarding the antiallergic action of propolis on the microbiota of the digestive and respiratory tracts and skin diseases as a method to selectively remove allergenic molecules by the process of bacterial biotransformation are also reported.

Effects of Echinocystic Acid on Atopic Dermatitis and Allergic Inflammation of the Skin and Lungs

BACKGROUND

Echinocystic acid (ECA), a pentacyclic triterpene enriched in various herbs, promotes anti-inflammatory and antioxidant activity; however, its therapeutic effects on atopic dermatitis (AD) or atopic march and the underlying mechanisms of action have not yet been fully elucidated.

PURPOSE

This study aimed to elucidate the effects and molecular mechanisms of ECA on AD and allergic inflammation.

METHODS

We evaluated the inhibitory effects of ECA using a house dust mite (HDM)-induced AD mouse model and human keratinocytes.

RESULTS

The results revealed that ECA improved AD symptoms by decreasing epidermal/dermal thickness, immune cell infiltration, and restoring skin barrier function, as well as an imbalanced immune response. In addition, repeated epicutaneous HDM challenges aggravated allergic inflammation in mice lungs, which was caused by the infiltration of immune cells and collagen deposition, whereas ECA alleviated these symptoms. Moreover, ECA suppressed the expression of T helper cell-derived cytokines, phosphorylation of extracellular signal-regulated kinase, and signal transducer and activator of transcription 1 in the skin and lungs of mice with HDM-induced AD, as well as inhibited the translocation of nuclear factor-κB in HaCaT keratinocytes.

CONCLUSION

This is the meaningful study to demonstrate that ECA improves allergic inflammation of the skin and lungs through recovery of the skin barrier, regulation of immune balance, and alleviation of lung inflammation, suggesting that ECA has therapeutic potential as an antiatopic and antiallergic agent that blocks the progression of AD to atopic march.

Anti-inflammatory effects of Eclipta prostrata Linné on house dust mite-induced atopic dermatitis in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Atopic dermatitis (AD) is a kind of inflammation on the skin following with swollen, itchy, dryness and cracked skin. Though the exact cause of AD is unknown, there are evidence that people with AD have a compromised skin barrier along with inflammation. Eclipta prostrata Linné is a traditional herbal medicinal plant, has been used for the diabetes, obesity, jaundice, and inflammation. We supposed E. prostrata L. has an anti-inflammatory effect on the skin.

AIM OF THE STUDY

We aimed to assess the effect of E. prostrata L. EtOH extract (EP) and elucidate the associated molecular mechanisms.

MATERIALS AND METHODS

The effect of EP and the molecular mechanisms were eluciated in house dust mite (HDM)-induced AD mice model and TNF-α/IFN-γ-stimulated HaCaT keratinocytes by histological analysis, enzyme-linked immunosorbent assay, quantitative real time polymerase chain reaction, and Western blot.

RESULTS

The results revealed that EP improved the progression of AD symptoms, decreasing epidermis/dermis thickness, infiltrated immune cells, and restored the skin barrier dysfunction and imbalanced immune response. EP suppressed the expressions of T helper (Th)1, Th2, Th17 cytokines, phosphorylation of extracellular signal-regulated kinase/signal transducer and activator of transcription 1 in skin of HDM-induced AD mice as well as inhibition the translocation of nuclear factor-κB in HaCaT keratinocytes.

CONCLUSIONS

Collectively, EP improved the allergic inflammation of the skin through recovery the skin barrier, and regulation the immune balance. These results suggest EP may have therapeutic potential as an anti-atopic agent.

How Do Pollen Allergens Sensitize?

Plant pollen is one of the main sources of allergens causing allergic diseases such as allergic rhinitis and asthma. Several allergens in plant pollen are panallergens which are also present in other allergen sources. As a result, sensitized individuals may also experience food allergies. The mechanism of sensitization and development of allergic inflammation is a consequence of the interaction of allergens with a large number of molecular factors that often are acting in a complex with other compounds, for example low-molecular-mass ligands, which contribute to the induction a type 2-driven response of immune system. In this review, special attention is paid not only to properties of allergens but also to an important role of their interaction with lipids and other hydrophobic molecules in pollen sensitization. The reactions of epithelial cells lining the nasal and bronchial mucosa and of other immunocompetent cells will also be considered, in particular the mechanisms of the activation of B and T lymphocytes and the formation of allergen-specific antibody responses.

Epigenetic Regulation of IFI44L Expression in Monocytes Affects the Functions of Monocyte-Derived Dendritic Cells in Systemic Lupus Erythematosus

Background

Interferon-inducible 44 like (IFI44L) is a newly discovered interferon-induced gene and has been reported to overexpress in systemic lupus erythematosus (SLE). However, little is known about the mechanism and function of IFI44L overexpression in SLE. In this study, we aimed to investigate the epigenetic mechanism of IFI44L overexpression in SLE monocyte and its potential functions contributing to the pathogenesis of SLE.

Methods

We collected peripheral blood from 20 SLE patients and 20 healthy controls. Expression of IFI44L in monocytes and effects of different signal transducers and activators of transcription (STAT) pathway inhibitors on IFI44L expression were detected. Recruitment of ten-eleven translocation protein (TET) by STAT and methylation of IFI44L promoter were evaluated. Effects of IFI44L overexpression on the expression of surface markers on monocyte-derived dendritic cells (Mo-DCs) were analyzed. T cell differentiation mediated by Mo-DCs and related cytokines production were also analyzed.

Results

Expression level of IFI44L was significantly increased in SLE monocyte. IFI44L expression was decreased most significantly in STAT3 inhibitor compared with other inhibitors. STAT3 regulated IFI44L expression and interacted with TET2 which induced DNA demethylation of IFI44L promoter. Overexpression of IFI44L in monocyte enhanced the maturation and functions of Mo-DC by upregulating costimulatory receptors and inducing Th1/Th17-related cytokines when cocultured with naïve CD4+ T cells.

Conclusion

TET2 recruited by STAT3 induces DNA demethylation of IFI44L promoter which promotes IFI44L overexpression in monocyte contributing to the pathogenesis of SLE by enhancing the maturation and functions of Mo-DC. IFI44L is expected to become a new target for treatment of SLE.

Emerging Roles of Platelets in Allergic Asthma

Allergic asthma is a complex chronic inflammatory disease of the airways, driven by Th2 immune responses and characterized by eosinophilic pulmonary inflammation, airway hyperresponsiveness, excessive mucus production, and airway remodeling. Overwhelming evidence from studies in animal models and allergic asthmatic patients suggests that platelets are aberrantly activated and recruited to the lungs. It has been established that platelets can interact with other immune cells and secrete various biochemical mediators to promote allergic sensitization and airway inflammatory response, and platelet deficiency may alleviate the pathological features and symptoms of allergic asthma. However, the comprehensive roles of platelets in allergic asthma have not been fully clarified, leaving attempts to treat allergic asthma with antiplatelet agents questionable. In this review, we summarize the role of platelet activation and pulmonary accumulation in allergic asthma; emphasis is placed on the different interactions between platelets with crucial immune cell types and the contribution of platelet-derived mediators in this context. Furthermore, clinical antiplatelet approaches to treat allergic asthma are discussed. This review provides a clearer understanding of the roles of platelets in the pathogenesis of allergic asthma and could be informative in the development of novel strategies for the treatment of allergic asthma.

Alternatives to Cow’s Milk-Based Infant Formulas in the Prevention and Management of Cow’s Milk Allergy

Cow’s milk-based infant formulas are the most common substitute to mother’s milk in infancy when breastfeeding is impossible or insufficient, as cow’s milk is a globally available source of mammalian proteins with high nutritional value. However, cow’s milk allergy (CMA) is the most prevalent type of food allergy among infants, affecting up to 3.8% of small children. Hypoallergenic infant formulas based on hydrolysed cow’s milk proteins are commercially available for the management of CMA. Yet, there is a growing demand for more options for infant feeding, both in general but especially for the prevention and management of CMA. Milk from other mammalian sources than the cow, such as goat, sheep, camel, donkey, and horse, has received some attention in the last decade due to the different protein composition profile and protein amino acid sequences, resulting in a potentially low cross-reactivity with cow’s milk proteins. Recently, proteins from plant sources, such as potato, lentil, chickpeas, quinoa, in addition to soy and rice, have gained increased interest due to their climate friendly and vegan status as well as potential lower allergenicity. In this review, we provide an overview of current and potential future infant formulas and their relevance in CMA prevention and management.

Reduction in Allergenicity and Induction of Oral Tolerance of Glycated Tropomyosin from Crab

Tropomyosin (TM) is an important crustacean (Scylla paramamosain) allergen. This study aimed to assess Maillard-reacted TM (TM-G) induction of allergenic responses with cell and mouse models. We analyzed the difference of sensitization and the ability to induce immune tolerance between TM and TM-G by in vitro and in vivo models, then we compared the relationship between glycation sites of TM-G and epitopes of TM. In the in vitro assay, we discovered that the sensitization of TM-G was lower than TM, and the ability to stimulate mast cell degranulation decreased from 55.07 ± 4.23% to 27.86 ± 3.21%. In the serum of sensitized Balb/c mice, the level of specific IgE produced by TM-G sensitized mice was significantly lower than TM, and the levels of interleukins 4 and interleukins 13 produced by Th2 cells in spleen lymphocytes decreased by 82.35 ± 5.88% and 83.64 ± 9.09%, respectively. In the oral tolerance model, the ratio of Th2/Th1 decreased from 4.05 ± 0.38 to 1.69 ± 0.19. Maillard reaction masked the B cell epitopes of TM and retained some T cell epitopes. Potentially, Maillard reaction products (MRPs) can be used as tolerance inducers for allergen-specific immunotherapy.

Early intervention and prevention of allergic diseases

Food allergy (FA) is now one of the most common chronic diseases of childhood often lasting throughout life and leading to significant worldwide healthcare burden. The precise mechanisms responsible for the development of this inflammatory condition are largely unknown; however, a multifactorial aetiology involving both environmental and genetic contributions is well accepted. A precise understanding of the pathogenesis of FA is an essential first step to developing comprehensive prevention strategies that could mitigate this epidemic. As it is frequently preceded by atopic dermatitis and can be prevented by early antigen introduction, the development of FA is likely facilitated by the improper initial presentation of antigen to the developing immune system. Primary oral exposure of antigens allowing for presentation via a well-developed mucosal immune system, rather than through a disrupted skin epidermal barrier, is essential to prevent FA. In this review, we present the data supporting the necessity of (1) an intact epidermal barrier to prevent epicutaneous antigen presentation, (2) the presence of specific commensal bacteria to maintain an intact mucosal immune system and (3) maternal/infant diet diversity, including vitamins and minerals, and appropriately timed allergenic food introduction to prevent FA.

Different Phenotypes in Asthma: Clinical Findings and Experimental Animal Models

Asthma is a respiratory allergic disease presenting a high prevalence worldwide, and it is responsible for several complications throughout life, including death. Fortunately, asthma is no longer recognized as a unique manifestation but as a very heterogenic manifestation. Its phenotypes and endotypes are known, respectively, as pathologic and molecular features that might not be directly associated with each other. The increasing number of studies covering this issue has brought significant insights and knowledge that are constantly expanding. In this review, we intended to summarize this new information obtained from clinical studies, which not only allowed for the creation of patient clusters by means of personalized medicine and a deeper molecular evaluation, but also created a connection with data obtained from experimental models, especially murine models. We gathered information regarding sensitization and trigger and emphasizing the most relevant phenotypes and endotypes, such as Th2-^high asthma and Th2-^low asthma, which included smoking and obesity-related asthma and mixed and paucigranulocytic asthma, not only in physiopathology and the clinic but also in how these phenotypes can be determined with relative similarity using murine models. We also further investigated how clinical studies have been treating patients using newly developed drugs focusing on specific biomarkers that are more relevant according to the patient's clinical manifestation of the disease.

In vitro co-culture model of human monocyte-derived dendritic cells and T cells to evaluate the sensitization of dinitrochlorobenzene

Exposure to sensitizer has been suggested to be hazardous to human health, evaluation the sensitization of sensitizer is particularly important and urgently needed. Dendritic cells (DCs) exert an irreplaceable function in immunity, and the T cell receptor (TCR) repertoire is key to ensuring immune response to foreign antigens. We hypothesized that a co-culture model of human monocyte-derived dendritic cells (Mo-DCs) and T cells could be employed to evaluate the sensitization of DNCB. An experimental model of DNCB-induced sensitization in rat was employed to examine alterations of cluster of differentiation CD103⁺ DCs and T cells. A co-cultured model of Mo-DCs and T cells was developed in vitro to assess the sensitization of DNCB through the phenotypic and functional alterations of Mo-DCs, as well as the TCR repertoire. We found that the CD103⁺ DCs phenotype and T-helper (Th) cells polarization altered in sensitization rats. In vitro, phenotypic alteration of Mo-DCs caused by DNCB were consistent with in vivo results, antigen uptake capacity of Mo-DCs diminished and capacity of Mo-DCs to prime T cell increased. Clones of the TCR repertoire and the diversity of TCR repertoire were enhanced, changes were noted in the usage of variable, joining, and variable-joining gene combinations. DNCB exposure potentiated alterations and characteristics of Mo-DCs and the TCR repertoire in a co-culture model. Such changes provided innovative ideas for evaluating sensitization of DNCB.

CpG-ODN Signaling via Dendritic Cells-Expressing MyD88, but Not IL-10, Inhibits Allergic Sensitization

Allergen-specific T helper (Th)2 cells orchestrate upon allergen challenge the development of allergic eosinophilic lung inflammation. Sensitization with alum adjuvant, a type 2 adjuvant, has been used extensively in animal models of allergic lung disease. In contrast, type 1 adjuvants like CpG-ODN, a synthetic toll-like receptor 9 agonist, inhibit the development of Th2 immunity. CpG-ODN induce type 1 and suppressive cytokines that influence Th2 cell differentiation. Here, we investigated the immune modulatory effect of CpG-ODN on allergic sensitization to OVA with alum focusing on dendritic cells (DCs) expressing the MyD88 molecule and the suppressive IL-10 cytokine. Using mice with specific cell deletion of MyD88 molecule, we showed that CpG-ODN suppressed allergic sensitization and consequent lung allergic inflammation signaling through the MyD88 pathway on dendritic cells, but not on B-cells. This inhibition was associated with an increased production of IL-10 in the bronchoalveolar lavage fluid. Sensitization to OVA with CpG-ODN of IL-10-deficient, but not wild-type mice, induced a shift towards Th1 pattern of inflammation. Employing bone marrow-derived dendritic cells (BM-DCs) pulsed with OVA for sensitizations with or without CpG-ODN, we showed that IL-10 is dispensable for the inhibition of allergic lung Th2 responses by CpG-ODN. Moreover, the lack of IL-10 on DCs was not sufficient for the CpG-ODN-induced immune-deviation towards a Th1 pattern. Accordingly, we confirmed directly the role of MyD88 pathway on DCs in the inhibition of allergic sensitization.

Impact of Probiotic Bacteria on Respiratory Allergy Disorders

Respiratory allergy is a common disease with an increased prevalence worldwide. The effective remedy is still unknown, and a new therapeutic approach is highly desirable. The review elaborates the influence of probiotic bacteria on respiratory allergy prevention and treatment with particular emphasis on the impact of the current methods of their administration – oral and intranasal. The background of the respiratory allergy is complex thus, we focused on the usefulness of probiotics in the alleviation of different allergy factors, in particular involved in pathomechanism, local hypersensitive evidence and the importance of epithelial barrier. In this review, we have shown that (1) probiotic strains may vary in modulatory potential in respiratory allergy, (2) probiotic bacteria are beneficial in oral and intranasal administration, (3) recombinant probiotic bacteria can modulate the course of respiratory allergy.

Combined Treatment With H1 and H4 Receptor Antagonists Improves Th2 Inflammatory Responses in the Nasal Mucosa of Allergic Rhinitis Rats

BACKGROUND

Histamine H1 receptor (H1R) antagonists are the first-line drugs for the treatment of allergic rhinitis (AR) at present. Emerging evidence supports an important role of histamine H4 receptor (H4R) in allergic diseases. However, information regarding the effects of combined treatment with H1 and H4 receptor antagonists in AR is limited.

OBJECTIVES

We aimed to assess the effects of combined treatment with H1R and H4R antagonists on Th2 inflammatory responses in the nasal mucosa of AR rats.

METHODS

Sprague Dawley rats were sensitized with ovalbumin and treated with H1R antagonist desloratadine or/and H4R antagonist JNJ7777120. Western blotting was used to assay the phenotypic markers of mature dendritic cells in the nasal mucosa, including major histocompatibility complex class II (MHC-II) and co-stimulatory molecules CD80, CD86 and OX40 ligand (OX40L). Th2 inflammatory cytokines including interleukin-4, 5 and 13 in nasal lavage fluids were determined by using enzyme-linked immunoassay.

RESULTS

The treatment with desloratadine alone down-regulated the CD86 expression, and decreased the production of Th2 cytokines, but had no impact on the expression of MHC-II, CD80 and OX40L. The administration of NJ7777120 alone reduced the levels of CD86, OX40L and Th2 cytokines, whereas MHC-II and CD80 expression was unaffected. The combination of desloratadine and JNJ7777120 showed more significant synergistic therapeutic effects than monotherapy.

CONCLUSION

H4R antagonist acted synergistically with H1R antagonist to reduce Th2 inflammatory responses by down-regulating CD86 and OX40L expression in the nasal mucosa of AR rats. The combination with H1R and H4R antagonists might be a new strategy for AR treatment.

Sublingual dendritic cells targeting by aptamer: Possible approach for improvement of sublingual immunotherapy efficacy

The efficacy improvement of current sublingual immunotherapy (SLIT) for preventing and treating respiratory airway allergic diseases is the main purpose of many investigations. In this study, we aimed to assess whether ovalbumin (Ova) encapsulated poly (lactic-co-glycolic) acid nanoparticles (PLGA NPs) decorated with dendritic cells (DCs)-specific aptamer could be applied for this purpose.The nanoparticles containing Ova were synthesized by emulsion/solvent evaporation method and attached to DCs-specific aptamer. Ova-sensitized BALB/c mice have been treated in five ways: subcutaneously with free Ova (SCIT), sublingually either with free Ova, Ova-PLGA NPs (two doses), Apt-Ova-PLGA NPs (two doses) and placebo/control Apt-Ova-PLGA NPs. For assessment of immunologic responses, IL-4, IFN-γ, IL-17, IL10, and TGF-β and IgE antibody levels were measured by ELISA and T cell proliferation were evaluated by MTT. In addition, lung and nasal histological examinations, NALF cells counting were carried out. Results declared that the lowest IgE and IL- 4 levels were observed in Apt-Ova-PLGA NPs (both doses). In the other hands, Apt-Ova-PLGA NPs (high dose) showed the highest increase of IFN- γ and TGF- β, decrease of IL-17 levels, total cell count and T-cell proliferation. IL-10 levels showed more decrease in SCIT, Apt-Ova-PLGA NPs (high dose) and Ova-PLGA NPs (high dose) than other groups. Histopathological examinations also confirmed in vitro results. Our findings suggest SLIT with this functionalized delivery system could be a promising approach for promoting the SLIT efficiency by decreasing the required allergen doses through specific delivery of allergen to sublingual DCs and enhancing the suppression of allergic responses.

Nanotechnology-Based Vaccines for Allergen-Specific Immunotherapy: Potentials and Challenges of Conventional and Novel Adjuvants under Research

The increasing prevalence of allergic diseases demands efficient therapeutic strategies for their mitigation. Allergen-specific immunotherapy (AIT) is the only causal rather than symptomatic treatment method available for allergy. Currently, AIT is being administered using immune response modifiers or adjuvants. Adjuvants aid in the induction of a vigorous and long-lasting immune response, thereby improving the efficiency of AIT. The successful development of a novel adjuvant requires a thorough understanding of the conventional and novel adjuvants under development. Thus, this review discusses the potentials and challenges of these adjuvants and their mechanism of action. Vaccine development based on nanoparticles is a promising strategy for AIT, due to their inherent physicochemical properties, along with their ease of production and ability to stimulate innate immunity. Although nanoparticles have provided promising results as an adjuvant for AIT in in vivo studies, a deeper insight into the interaction of nanoparticle-allergen complexes with the immune system is necessary. This review focuses on the methods of harnessing the adjuvant effect of nanoparticles by detailing the molecular mechanisms underlying the immune response, which includes allergen uptake, processing, presentation, and induction of T cell differentiation.

Hydrophobic ligands influence the structure, stability, and processing of the major cockroach allergen Bla g 1

The cockroach allergen Bla g 1 forms a novel fold consisting of 12 amphipathic alpha-helices enclosing an exceptionally large hydrophobic cavity which was previously demonstrated to bind a variety of lipids. Since lipid-dependent immunoactivity is observed in numerous allergens, understanding the structural basis of this interaction could yield insights into the molecular determinants of allergenicity. Here, we report atomic modelling of Bla g 1 bound to both fatty-acid and phospholipids ligands, with 8 acyl chains suggested to represent full stoichiometric binding. This unusually high occupancy was verified experimentally, though both modelling and circular dichroism indicate that the general alpha-helical structure is maintained regardless of cargo loading. Fatty-acid cargoes significantly enhanced thermostability while inhibiting cleavage by cathepsin S, an endosomal protease essential for antigen processing and presentation; the latter of which was found to correlate to a decreased production of known T-cell epitopes. Both effects were strongly dependent on acyl chain length, with 18-20 carbons providing the maximal increase in melting temperature (~20 °C) while completely abolishing proteolysis. Diacyl chain cargoes provided similar enhancements to thermostability, but yielded reduced levels of proteolytic resistance. This study describes how the biophysical properties of Bla g 1 ligand binding and digestion may relate to antigen processing, with potential downstream implications for immunogenicity.

Metal nanomaterials: Immune effects and implications of physicochemical properties on sensitization, elicitation, and exacerbation of allergic disease

The recent surge in incorporation of metallic and metal oxide nanomaterials into consumer products and their corresponding use in occupational settings have raised concerns over the potential for metals to induce size-specific adverse toxicological effects. Although nano-metals have been shown to induce greater lung injury and inflammation than their larger metal counterparts, their size-related effects on the immune system and allergic disease remain largely unknown. This knowledge gap is particularly concerning since metals are historically recognized as common inducers of allergic contact dermatitis, occupational asthma, and allergic adjuvancy. The investigation into the potential for adverse immune effects following exposure to metal nanomaterials is becoming an area of scientific interest since these characteristically lightweight materials are easily aerosolized and inhaled, and their small size may allow for penetration of the skin, which may promote unique size-specific immune effects with implications for allergic disease. Additionally, alterations in physicochemical properties of metals in the nano-scale greatly influence their interactions with components of biological systems, potentially leading to implications for inducing or exacerbating allergic disease. Although some research has been directed toward addressing these concerns, many aspects of metal nanomaterial-induced immune effects remain unclear. Overall, more scientific knowledge exists in regards to the potential for metal nanomaterials to exacerbate allergic disease than to their potential to induce allergic disease. Furthermore, effects of metal nanomaterial exposure on respiratory allergy have been more thoroughly-characterized than their potential influence on dermal allergy. Current knowledge regarding metal nanomaterials and their potential to induce/exacerbate dermal and respiratory allergy are summarized in this review. In addition, an examination of several remaining knowledge gaps and considerations for future studies is provided.

Dendritic Cells/Macrophages-Targeting Feature of Ebola Glycoprotein and its Potential as Immunological Facilitator for Antiviral Vaccine Approach

In the prevention of epidemic and pandemic viral infection, the use of the antiviral vaccine has been the most successful biotechnological and biomedical approach. In recent times, vaccine development studies have focused on recruiting and targeting immunogens to dendritic cells (DCs) and macrophages to induce innate and adaptive immune responses. Interestingly, Ebola virus (EBOV) glycoprotein (GP) has a strong binding affinity with DCs and macrophages. Shreds of evidence have also shown that the interaction between EBOV GP with DCs and macrophages leads to massive recruitment of DCs and macrophages capable of regulating innate and adaptive immune responses. Therefore, studies for the development of vaccine can utilize the affinity between EBOV GP and DCs/macrophages as a novel immunological approach to induce both innate and acquired immune responses. In this review, we will discuss the unique features of EBOV GP to target the DC, and its potential to elicit strong immune responses while targeting DCs/macrophages. This review hopes to suggest and stimulate thoughts of developing a stronger and effective DC-targeting vaccine for diverse virus infection using EBOV GP.

Estrogen and estrogen receptor signaling promotes allergic immune responses: Effects on immune cells, cytokines, and inflammatory factors involved in allergy

Hypersensitivity occurs when the body is stimulated by an antigen, resulting in an immune response, and leads to a physiological disorder or abnormal tissue trauma. Various immune cells, cytokines, and inflammatory mediators are involved in the immune responses related to allergic diseases, which are the core of anaphylaxis. Estrogen receptors are widely distributed in immune cells, which combine with estrogen and participate in allergic responses by affecting immune cells, cytokines, and inflammatory factors. We aimed to summarize the association between estrogen and allergic reactions to provide a scientific basis for understanding and studying the mechanisms of allergic diseases.

Thymic stromal lymphopoietin epigenetically upregulates Fc receptor γ subunit-related receptors on antigen-presenting cells and induces TH2/TH17 polarization through dectin-2

BACKGROUND

Fc receptor γ subunit (FcRγ)-related receptors expressed on antigen-presenting cells (APCs) enhance allergen sensitization and allergic inflammation. DNA demethylation of the high-affinity IgE receptor γ subunit gene (FCER1G) leads to FcRγ and FcεRI overexpression on monocytes from patients with atopic dermatitis.

OBJECTIVE

We investigated epigenetic mechanisms underlying FCER1G demethylation and upregulation of FcRγ-related receptors on APCs and the consequent effect on allergic responses.

METHODS

Effects of thymic stromal lymphopoietin (TSLP) on expression of FcRγ and its related receptors and methylation or hydroxymethylation of FCER1G in human monocytes were assessed. Recruitment of ten-eleven translocation protein (TET) 2 to FCER1G by TSLP-activated phosphorylated signal transducer and activator of transcription 5 (pSTAT5) was evaluated. Effects of TSLP on expression of FcRγ-related receptors and costimulatory receptors on monocyte-derived dendritic cells (DCs) and the ability of DCs to take up ovalbumin were analyzed. TSLP-induced T_H polarization and related cytokine production were also analyzed.

RESULTS

pSTAT5 activation by TSLP resulted in TET2 recruitment to FCER1G, leading to FCER1G demethylation and subsequent upregulation of FcRγ-related receptors on monocytes. TSLP not only stimulated monocyte-derived DC maturation but also maintained their allergen uptake ability, likely through maintenance and upregulation of FcRγ-related receptors. Allergen sensitization and upregulation of T_H2/T_H17-related cytokines contributed to TSLP-DC-induced T_H2/T_H17 polarization. The latter was attenuated on neutralization with a dectin-2 antibody.

CONCLUSIONS

TSLP mediated upregulation of FcRγ-related receptors on APCs through activation of pSTAT5, which recruited TET2 to induce FCER1G demethylation. TSLP-induced allergic T_H2/T_H17 polarization likely depends on dectin-2-mediated allergen sensitization and upregulation of T_H2/T_H17-related cytokines.

Therapeutic Potential of Hematopoietic Prostaglandin D2 Synthase in Allergic Inflammation

Worldwide, there is a rise in the prevalence of allergic diseases, and novel efficient therapeutic approaches are still needed to alleviate disease burden. Prostaglandin D₂ (PGD₂) has emerged as a central inflammatory lipid mediator associated with increased migration, activation and survival of leukocytes in various allergy-associated disorders. In the periphery, the hematopoietic PGD synthase (hPGDS) acts downstream of the arachidonic acid/COX pathway catalysing the isomerisation of PGH₂ to PGD₂, which makes it an interesting target to treat allergic inflammation. Although much effort has been put into developing efficient hPGDS inhibitors, no compound has made it to the market yet, which indicates that more light needs to be shed on potential PGD₂ sources and targets to determine which particular condition and patient will benefit most and thereby improve therapeutic efficacy. In this review, we want to revisit current knowledge about hPGDS function, expression in allergy-associated cell types and their contribution to PGD₂ levels as well as beneficial effects of hPGDS inhibition in allergic asthma, rhinitis, atopic dermatitis, food allergy, gastrointestinal allergic disorders and anaphylaxis.

Probiotics against airway allergy: host factors to consider

The worldwide prevalence of allergic diseases has drastically increased in the past decades. Recent studies underline the importance of microbial exposure for the development of a balanced immune system. Consequently, probiotic bacteria are emerging as a safe and natural strategy for allergy prevention and treatment. However, clinical probiotic intervention studies have so far yielded conflicting results. There is increasing awareness about the importance of host-associated factors that determine whether an individual will respond to a specific probiotic treatment, and it is therefore crucial to promote a knowledge-based instead of an empirical selection of promising probiotic strains and their administration regimen.In this Review, we summarize the insights from animal model studies of allergic disease, which reveal how host-related factors - such as genetic makeup, sex, age and microbiological status - can impact the outcomes of preventive or curative probiotic treatment. We explore why and how these factors can influence the results of probiotic studies and negatively impact the reproducibility in animal experiments. These same factors might profoundly influence the outcomes of human clinical trials, and can potentially explain the conflicting results from probiotic intervention studies. Therefore, we also link these host-related factors to human probiotic study outcomes in the context of airway allergies.

Plasticizer, di(2-ethylhexyl)phthalate (DEHP) enhances cockroach allergen extract-driven airway inflammation by enhancing pulmonary Th2 as well as Th17 immune responses in mice

In recent decades, there has been a gradual increase in the prevalence of asthma. Various factors including environmental pollutants have contributed to this phenomenon. Plasticizer, di(2-ethylhexyl)phthalate (DEHP) is one of the commonest environmental pollutants due to its association with plastic products. DEHP gets released from plastic products easily leading to respiratory exposure in humans. As a consequence, DEHP is associated with allergic asthma in humans and animals. DEHP is reported to act as an adjuvant in ovalbumin-induced mouse models of asthma at high doses. However, these studies mostly looked into the role of DEHP on Th2 cytokines/eosinophilic inflammation without investigating the role of airway epithelial cells (AECs)/dendritic cells (DCs)/Th17 cells. Its adjuvant activity with natural allergens such as cockroach allergens at tolerable daily intake needs to be explored. Cockroach allergens and DEHP may be inhaled together due to their coexistence in work place as well as household environments. Therefore, effect of DEHP was assessed in cockroach allergens extract (CE)-induced mouse model of asthma. Airway inflammation, histopathology, mucus secretion, and immune responses related to Th2/Th17/DCs and AECs were assessed in mice with DEHP exposure alone and in combination with CE. Our study shows that DEHP converts CE-induced eosinophilic inflammation into mixed granulocytic inflammation by promoting Th2 as well as Th17 immune responses. This was probably due to downregulation of E-cadherin in AECs, and enhancement of costimulatory molecules (MHCII/CD86/CD40)/pro-inflammatory cytokines (IL-6/MCP-1) in DCs by DEHP. This suggests that DEHP facilitates development of mixed granulocytic airway inflammation in the presence of a natural allergen.

PKCδ-Mediated Nox2 Activation Promotes Fluid-Phase Pinocytosis of Antigens by Immature Dendritic Cells

Aims

Macropinocytosis is a major endocytic pathway by which dendritic cells (DCs) internalize antigens in the periphery. Despite the importance of DCs in the initiation and control of adaptive immune responses, the signaling mechanisms mediating DC macropinocytosis of antigens remain largely unknown. The goal of the present study was to investigate whether protein kinase C (PKC) is involved in stimulation of DC macropinocytosis and, if so, to identify the specific PKC isoform(s) and downstream signaling mechanisms involved.

Methods

Various cellular, molecular and immunological techniques, pharmacological approaches and genetic knockout mice were utilized to investigate the signaling mechanisms mediating DC macropinocytosis.

Results

Confocal laser scanning microscopy confirmed that DCs internalize fluorescent antigens (ovalbumin) using macropinocytosis. Pharmacological blockade of classical and novel PKC isoforms using calphostin C abolished both phorbol ester- and hepatocyte growth factor-induced antigen macropinocytosis in DCs. The qRT-PCR experiments identified PKCδ as the dominant PKC isoform in DCs. Genetic studies demonstrated the functional role of PKCδ in DC macropinocytosis of antigens, their subsequent maturation, and secretion of various T-cell stimulatory cytokines, including IL-1α, TNF-α and IFN-β. Additional mechanistic studies identified NADPH oxidase 2 (Nox2) and intracellular superoxide anion as important players in DC macropinocytosis of antigens downstream of PKCδ activation.

Conclusion

The findings of the present study demonstrate a novel mechanism by which PKCδ activation via stimulation of Nox2 activity and downstream redox signaling promotes DC macropinocytosis of antigens. PKCδ/Nox2-mediated antigen macropinocytosis stimulates maturation of DCs and secretion of T-cell stimulatory cytokines. These findings may contribute to a better understanding of the regulatory mechanisms in DC macropinocytosis and downstream regulation of T-cell-mediated responses.