Critical roles of regulatory B and T cells in helminth parasite-induced protection against allergic airway inflammation

Human Ascaris infection is associated with higher frequencies of IL-10 producing B cells

INTRODUCTION

Ascaris lumbricoides has dual effects on the immune system of infected hosts. The IgE response to this parasite has been thoroughly studied, but little is known about cellular responses induced by infection. This study aims to explore the interplay between A. lumbricoides infection and B cell responses, especially B regulatory cells.

METHODS

Participants from Santa Catalina, Bolívar, Colombia, a helminth-endemic town, were screened for soil-transmitted helminthiasis (STH) using stool examinations. Eighteen A. lumbricoides-infected and 11 non-infected subjects were selected. Blood samples were analyzed for Breg cells and related cytokines, and immunoglobulins specific to the A. lumbricoides excretory/secretory product, ABA-1.

RESULTS

Infected subjects exhibited higher frequencies of Breg cells, especially those with a higher A. lumbricoides egg burden. Higher frequencies of different Breg subsets were observed in infected individuals, with CD25+CD71+CD73- B cells being notably increased in strongly infected individuals. Additionally, A. lumbricoides infection was associated with reduced levels of circulating ABA-1-specific IgG1 and IgE. IL-10+ B cell frequencies correlated inversely with ABA-1-specific IgE.

CONCLUSIONS

A. lumbricoides infection has a significant impact on the immune response, particularly on Breg cell populations and antibody responses. Our findings suggest that A. lumbricoides infection mediates a dose-dependent immunosuppressive response characterized by an increase in Breg cells and concomitant suppression of ABA-1-specific humoral responses.

Targeted inhibition of m6A demethylase FTO by FB23 attenuates allergic inflammation in the airway epithelium

Epithelial cells play a crucial role in asthma, contributing to chronic inflammation and airway hyperresponsiveness. m6A modification, which involves key proteins such as the demethylase fat mass and obesity-associated protein (FTO), is crucial in the regulation of various diseases, including asthma. However, the role of FTO in epithelial cells and the development of asthma remains unclear. In this study, we investigated the demethylase activity of FTO using a small-molecule inhibitor FB23 in epithelial cells and allergic inflammation in vivo and in vitro. We examined the FTO-regulated transcriptome-wide m6A profiling by methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA-seq under FB23 treatment and allergic inflammation conditions. Immunofluorescence staining was performed to assess the tissue-specific expression of FTO in asthmatic bronchial mucosa. We demonstrated that FB23 alleviated allergic inflammation in IL-4/IL-13-treated epithelial cells and house dust mite (HDM)-induced allergic airway inflammation mouse model. The demethylase activity of FTO contributed to the regulation of TNF-α signaling via NF-κB and epithelial-mesenchymal transition-related pathways under allergic inflammation conditions in epithelial cells. FTO was expressed in epithelial, submucosal gland, and smooth muscle cells in human bronchial mucosa. In conclusion, FB23-induced inhibition of FTO alleviates allergic inflammation in epithelial cells and HDM-induced mice, potentially through diverse cellular processes and epithelial-mesenchymal transition signaling pathways, suggesting that FTO is a potential therapeutic target in asthma management.

Microbes little helpers and suppliers for therapeutic asthma approaches

Bronchial asthma is a prevalent and increasingly chronic inflammatory lung disease affecting over 300 million people globally. Initially considered an allergic disorder driven by mast cells and eosinophils, asthma is now recognized as a complex syndrome with various clinical phenotypes and immunological endotypes. These encompass type 2 inflammatory endotypes characterized by interleukin (IL)-4, IL-5, and IL-13 dominance, alongside others featuring mixed or non-eosinophilic inflammation. Therapeutic success varies significantly based on asthma phenotypes, with inhaled corticosteroids and beta-2 agonists effective for milder forms, but limited in severe cases. Novel antibody-based therapies have shown promise, primarily for severe allergic and type 2-high asthma. To address this gap, novel treatment strategies are essential for better control of asthma pathology, prevention, and exacerbation reduction. One promising approach involves stimulating endogenous anti-inflammatory responses through regulatory T cells (Tregs). Tregs play a vital role in maintaining immune homeostasis, preventing autoimmunity, and mitigating excessive inflammation after pathogenic encounters. Tregs have demonstrated their ability to control both type 2-high and type 2-low inflammation in murine models and dampen human cell-dependent allergic airway inflammation. Furthermore, microbes, typically associated with disease development, have shown immune-dampening properties that could be harnessed for therapeutic benefits. Both commensal microbiota and pathogenic microbes have demonstrated potential in bacterial-host interactions for therapeutic purposes. This review explores microbe-associated approaches as potential treatments for inflammatory diseases, shedding light on current and future therapeutics.

Feline heartworm disease and environmental allergens hypersensitivity: is there a link?

BACKGROUND

Cats can be infected by Dirofilaria immitis, the causative agent of heartworm disease, characterized by respiratory signs, airway hyperreactivity, remodelling and inflammation. Allergy is a multifactorial pathology, and the role of a number of helminth parasites in the development of allergies in humans and other species has been demonstrated in many studies. The aim of the present study was to verify whether cats seropositive for D. immitis present hypersensitivity to some environmental allergens.

METHODS

Blood samples were collected from 120 cats and tested for the presence of specific immunoglobulin G antibodies against D. immitis and for hypersensitivity to 20 allergens, using commercial allergen test kits.

RESULTS

Of the 120 cats tested, 72 (60.0%) were seropositive for anti-D. immitis IgG and 55 (45.8%) showed clinical signs of heartworm disease of a respiratory nature. The results of testing with the allergen kits showed that 50.8% of cats were seropositive for ≥ 1 allergens, with the most common allergens being Dermatophagoides farinae (25.8%), Dermatophagoides pteronyssinus (20.0%), Malassezia (17.5%) and Ctenocephalides felis (14.2%). The prevalence of allergies was significantly higher-by almost threefold-in cats seropositive for D. immitis (68.1% vs. 25%). There were no significant differences between the prevalence of allergic cats and presence/absence of symptoms, and the results confirmed that symptoms were not a decisive factor for the presence of allergies. The risk for developing allergies was 6.3-fold higher in cats seropositive for D. immitis than in cats that were seronegative, confirming that seropositivity for D. immitis is a risk factor.

CONCLUSIONS

Cats with confirmed heartworm can develop serious respiratory signs, potentially leading to progression to permanent lung injury and predisposing cats to hyperresponsive airway disease. Previous studies have shown that seropositivity for D. immitis and Wolbachia is related to the presence of bronchoconstriction and bronchospasm in the affected cat. The results support the suspicion that contact with D. immitis may be a risk factor for the presence of allergies.

Allergic disease and sensitization disparity in urban and rural China: A EuroPrevall-INCO study

BACKGROUND

Studies in comparison with allergic diseases and sensitization between rural and urban environments in westernized countries might be biased and not adequately reflect countries undergoing rapid transition.

METHODS

A total of 5542 schoolchildren from urban area and 5139 from rural area were recruited for the EuroPrevall-INCO survey. A subsequent case-control sample with 196 children from urban area and 202 from rural area was recruited for a detailed face-to-face questionnaire and assessment of sensitization. Skin prick tests and serum-specific IgE measurements were used to assess sensitizations against food and aeroallergens. Logistic regression analysis was used to determine associations between risk/protective factors, food adverse reactions (FAR), allergic diseases, and sensitizations.

RESULTS

Prevalence of self-reported allergic diseases, including asthma (6.6% vs.2.5%), rhinitis (23.2% vs.5.3%), and eczema (34.1% vs.25.9%), was higher in urban than in rural children. Urban children had a significantly higher prevalence of FAR and related allergic diseases, and lower food/inhalation allergen sensitization rate, than those of rural children. In urban children, frequent changing places of residency (odds ratio 2.85, 95% confidence interval: 1.45-5.81) and antibiotic usage (3.54, 1.77-7.32) in early life were risk factors for sensitization, while sensitization and family history of allergy were risk factors for allergic diseases. In rural children, exposure to rural environments in early life was protective against both allergen sensitizations (0.46, 0.21-0.96) and allergic diseases (0.03, 0.002-0.19).

CONCLUSION

We observed a disparity in rates of allergic diseases and allergen sensitization between rural and urban children. In addition to family history, the development of allergic diseases and allergen sensitization were associated with specific urban/rural environmental exposures in early life.

Rural environment reduces allergic inflammation by modulating the gut microbiota

Rural environments and microbiota are linked to a reduction in the prevalence of allergies. However, the mechanism underlying the reduced allergies modulated by rural residency is unclear. Here, we assessed gut bacterial composition and metagenomics in urban and rural children in the EuroPrevall-INCO cohort. Airborne dusts, including mattress and rural henhouse dusts, were profiled for bacterial and fungal composition by amplicon sequencing. Mice were repeatedly exposed to intranasal dust extracts and evaluated for their effects on ovalbumin (OVA)-induced allergic airway inflammation, and gut microbiota restoration was validated by fecal microbiota transplant (FMT) from dust-exposed donor mice. We found that rural children had fewer allergies and unique gut microbiota with fewer Bacteroides and more Prevotella. Indoor dusts in rural environments harbored higher endotoxin level and diversity of bacteria and fungi, whereas indoor urban dusts were enriched with Aspergillus and contained elevated pathogenic bacteria. Intranasal administration of rural dusts before OVA sensitization reduced respiratory eosinophils and blood IgE level in mice and also led to a recovery of gut bacterial diversity and Ruminiclostridium in the mouse model. FMT restored the protective effect by reducing OVA-induced lung eosinophils in recipient mice. Together, these results support a cause-effect relationship between exposure to dust microbiota and allergy susceptibility in children and mice. Specifically, rural environmental exposure modulated the gut microbiota, which was essential in reducing allergy in children from Southern China. Our findings support the notion that the modulation of gut microbiota by exposure to rural indoor dust may improve allergy prevention.

B cell-T cell interplay in immune regulation: A focus on follicular regulatory T and regulatory B cell functions

B cells are the core components of humoral immunity. A mature B cell can serve in multiple capacities, including antibody production, antigen presentation, and regulatory functions. Forkhead box P3 (FoxP3)-expressing regulatory T cells (Tregs) are key players in sustaining immune tolerance and keeping inflammation in check. Mounting evidence suggests complex communications between B cells and Tregs. In this review, we summarize the yin-yang regulatory relationships between B cells and Tregs mainly from the perspectives of T follicular regulatory (Tfr) cells and regulatory B cells (Bregs). We discuss the regulatory effects of Tfr cells on B cell proliferation and the germinal center response. Additionally, we review the indispensable role of B cells in ensuring homeostatic Treg survival and describe the function of Bregs in promoting Treg responses. Finally, we introduce a new subset of Tregs, termed Treg-of-B cells, which are induced by B cells, lake the expression of FoxP3 but still own immunomodulatory effects. In this article, we also enumerate a sequence of research from clinical patients and experimental models to clarify the role of Tfr cells in germinal centers and the role of convention B cells and Bregs to Tregs in the context of different diseases. This review offers an updated overview of immunoregulatory networks and unveils potential targets for therapeutic interventions against cancer, autoimmune diseases and allograft rejection.

Majie Cataplasm Promotes Th1 Response to Fight against Asthmatic Th2 Inflammation through NKs

Background

Immune cells are tightly bound up with the pathogenesis of asthma. Besides T cells, B cells, macrophages, and mast cells, the mechanism of innate lymphoid cells (ILCs) in asthma is gradually explicit. As a kind of traditional Chinese medicine, Majie cataplasm realizes its potential in the clinical setting as an adjuvant for asthma. In our previous experiments, Majie cataplasm inhibits the increasing Th1 and Th2 in allergic asthma inflammation and reshapes a balance between Th1 and Th2. As ILCs are the reflection of Th cells in lung tissues, we will figure out whether Majie cataplasm could have similar effects on ILCs or not.

Methods

A total of 40 female C57/BL6 mice were randomly divided into the control group (n = 10), the asthma model group (n = 10), the dexamethasone group (n = 10), and the Majie cataplasm group (n = 10). Except for the control group, mice were sensitized with ovalbumin (OVA) and excited to establish mice models of asthma. Lung tissue and splenic tissue were collected at 24 h after the last challenge with OVA, and the cell suspension of the lungs and spleen was prepared. The number of ILC1s, ILC2s, ILC3s, and NKs cells in the lungs and Tregs and B10s in the spleen were detected by flow cytometry (FCM). This was followed by simultaneous quantitative detection of 40 inflammatory cytokines and chemokines in the lung by a protein microarray.

Results

The dexamethasone and Majie cataplasm could restore the number of ILC1s, ILC2s, and ILC3s in lung tissue. Compared with the control group, these cells remained unchanged in the asthma model group, while ILC1s (P < 0.001, P < 0.01), ILC2s (P < 0.001, P < 0.01), and ILC3s (P < 0.01, P < 0.05) were restored after the intervention of dexamethasone and Majie cataplasm. The number of NKs was low among the control group, the asthma model group, and the dexamethasone group, while the number of NKs rocketed in the Majie cataplasm group (P < 0.0001). For splenic Tregs and B10s, Majie cataplasm could curb the increasing numbers of them in the asthma model group (P < 0.0001, P < 0.01), while only Tregs were suppressed by the dexamethasone (P < 0.0001). For the inflammatory cytokines in the lung, the contents of TNF-α, TNFR2, CXCL-9, CCL-12, CCL-9, CCL-2, and CCL-5 in the asthma model group were higher than those in the control group, while the contents of GM-CSF and IL-1α were decreased. Comparing the asthma model group to the dexamethasone group, the levels of G-CSF, CCL-9, CCL-5, and TNFR2 in the former group were higher. The levels of TNF-α, TNFR2, and CCL-9 in the asthma model group increase, while the levels of IFN-γ, IL-1α, ICAM-1, and IL-4 increased in the Majie cataplasm group, especially IFN-γ and IL-1α.

Conclusion

Both the dexamethasone and Majie cataplasm could control the asthmatic inflammation by reducing the inflammatory factors, inhibiting the adaptive inflammation reaction in the latter stage of inflammation and furtherly reversing the inhibition of ILC2s, ILC2s, and ILC3s. In addition, Majie cataplasm can promote the quantity of NKs and the content of IL-1α and IFN-γ, induce IFN-γ⁺NKs to shut down the Th2 response, and tend to elicit the Th1 response.

Microbial (co)infections: Powerful immune influencers

It is well established that by modulating various immune functions, host infection may alter the course of concomitant inflammatory diseases, of both infectious and autoimmune etiologies. Beyond the major impact of commensal microbiota on the immune status, host exposure to viral, bacterial, and/or parasitic microorganisms also dramatically influences inflammatory diseases in the host, in a beneficial or harmful manner. Moreover, by modifying pathogen control and host tolerance to tissue damage, a coinfection can profoundly affect the development of a concomitant infectious disease. Here, we review the diverse mechanisms that underlie the impact of (co)infections on inflammatory disorders. We discuss epidemiological studies in the context of the hygiene hypothesis and shed light on the sometimes dual impact of germ exposure on human susceptibility to inflammatory disease. We then summarize the immunomodulatory mechanisms at play, which can involve pleiotropic effects of immune players and discuss the possibility to harness pathogen-derived compounds to the host benefit.

Profiles of CD4+, CD8+, and regulatory T cells and circulating cytokines in hookworm-infected children in southern Thailand

Hookworm infection is the most common human helminthic infection in the rural areas of southern Thailand. There is little information on the induced cellular immune responses in hookworm-infected children. The present study aimed to investigate the cellular immune responses, regulatory T cells (Tregs), Th1-type cytokines (interleukin (IL)-2 and interferon (IFN)-γ), a Th2-type cytokine (IL-5) and IL-10, which is one of the cytokines secreted by Tregs in hookworm-infected children. Twenty-nine schoolchildren diagnosed with hookworm infections and 28 healthy controls were enrolled in the study. CD4+ and CD8+ T cells and Tregs in whole blood were analyzed using flow cytometry. Plasma IL-2, IL-5, IL-10 and IFN-γ concentrations were quantified by enzyme-linked immunosorbent assay (ELISA). The median CD4+ T cell frequency was significantly higher in hookworm-infected children than healthy controls. Compared to healthy controls, hookworm-infected children had a significantly increased absolute number of Tregs. No differences in circulating CD8+ T cell median frequency or absolute numbers were observed among hookworm-infected children or healthy controls. Elevated IL-2 and IL-10 concentrations were found in hookworm-infected children. Moreover, the absolute number of Tregs was significantly positively correlated with the plasma IL-10 concentration (r_s = 0.406, P = 0.029). This study showed that hookworm-infected schoolchildren had significantly different immune responses than healthy controls, including an increase in the CD4+ T cell number, a significant induction of Tregs and significantly elevated circulating IL-10 levels. These alterations could be the mechanism underlying the immunomodulation that alleviates allergic diseases among hookworm-infected individuals.

Remote regulation of type 2 immunity by intestinal parasites

The intestinal tract is the target organ of most parasitic infections, including those by helminths and protozoa. These parasites elicit prototypical type 2 immune activation in the host's immune system with striking impact on the local tissue microenvironment. Despite local containment of these parasites within the intestinal tract, parasitic infections also mediate immune adaptation in peripheral organs. In this review, we summarize the current knowledge on how such gut-tissue axes influence important immune-mediated resistance and disease tolerance in the context of coinfections, and elaborate on the implications of parasite-regulated gut-lung and gut-brain axes on the development and severity of airway inflammation and central nervous system diseases.

Regulatory B cells, A to Z

B cells play a central role in the immune system through the production of antibodies. During the past two decades, it has become increasingly clear that B cells also have the capacity to regulate immune responses through mechanisms that extend beyond antibody production. Several types of human and murine regulatory B cells have been reported that suppress inflammatory responses in autoimmune disease, allergy, infection, transplantation, and cancer. Key suppressive molecules associated with regulatory B-cell function include the cytokines IL-10, IL-35, and TGF-β as well as cell membrane-bound molecules such as programmed death-ligand 1, CD39, CD73, and aryl hydrocarbon receptor. Regulatory B cells can be induced by a range of different stimuli, including microbial products such as TLR4 or TLR9 ligands, inflammatory cytokines such as IL-6, IL-1β, and IFN-α, as well as CD40 ligation. This review provides an overview of our current knowledge on regulatory B cells. We discuss different types of regulatory B cells, the mechanisms through which they exert their regulatory functions, factors that lead to induction of regulatory B cells and their role in the alteration of inflammatory responses in different diseases.

Follicular T Helper and Breg Cell Balance in Severe Allergic Asthma Before and After Omalizumab Therapy

BACKGROUND

Severe allergic asthma (SAA) is based on type 2 (T2-high) immune responses to allergens promoting type 2 T helper (Th2) cell cytokine responses and production of IgE antibodies. Omalizumab was the first biological drug licensed for clinical use in the management of IgE-mediated SAA. Despite emerging evidence supporting the prominent role of follicular T cells (Tfh), Breg and Treg subsets, in the development and progression of SAA, no data are available on the impact of omalizumab therapy.

METHODS

Ten SAA patients monitored at the Respiratory Diseases Unit of Siena University Hospital and ten healthy sex- and age-matched controls were enrolled in the study. Clinical and functional parameters were collected at baseline (T0) and after 6 months of therapy (T6). Cellular population analysis was determined through multicolour flow cytometry.

RESULTS

SAA patients showed higher percentages of Th17.1, Tfh and Tfh2 while CD24hiCD27hi Breg cell, Treg and Tfr percentages were significantly lower than in controls. Higher percentages of Tfh2 in patients with nasal polyps than in those without and in controls were observed. At T6, significant decreases in Tfh and Tfh2 compared with T0 were observed. A slightly significant increase in Teffs was reported at T6 compared to T0. ΔIgE levels in serum were correlated with ΔCD19+CD24+CD27+ Breg cell percentages (r = - 0.86, p = 0.0022).

CONCLUSIONS

Our data explored the changes in Tfh cells, Tregs and Bregs in severe asthma. The restoration of immunological imbalance in SAA patients after omalizumab is certainly intriguing and represents a glimpse into the comprehension of immunological effects of treatment.

Extracellular vesicles of Echinococcus granulosus have therapeutic effects in allergic airway inflammation

BACKGROUND

Previous studies have shown that Echinococcus granulosus cystic fluid can alleviate Th2 allergic airway inflammatory responses by increasing the number of CD4⁺ CD25⁺ Foxp3⁺ T (regulatory T; Treg) cells. Parasite-derived extracellular vesicles (EV) are known to not only promote parasite infection by communicating between parasites but also regulate the inflammatory response by acting as an immunomodulatory agent in the host.

METHODS

To evaluate the effect of EV extracted from the cystic fluid of E. granulosus on allergic airway inflammation, gene expression was investigated after administering EV to mouse lung epithelial cells (MLE-12) following 2 h of pretreatment with Aspergillus proteins. An allergic airway inflammation animal model was used to investigate the regulation of the inflammatory response by EV and induced with ovalbumin.

RESULTS

EV treatment significantly reduced airway resistance and the number of eosinophils and other immune cells in the bronchoalveolar lavage fluid and Th2- and Th17-related cytokine levels. EV pretreatment decreased the number of IL-4⁺ CD4⁺ T cells and increased the number of Treg cells in the lung-draining lymph nodes and spleen.

CONCLUSIONS

Echinococcus granulosus cystic fluid derived EV ameliorated Th2 allergic airway inflammatory through Treg cells, similar to whole cystic fluid treatment. Thus, EV may be important immunomodulatory molecules in cystic fluid.

Immunosuppressive Mechanisms of Regulatory B Cells

Regulatory B cells (Bregs) is a term that encompasses all B cells that act to suppress immune responses. Bregs contribute to the maintenance of tolerance, limiting ongoing immune responses and reestablishing immune homeostasis. The important role of Bregs in restraining the pathology associated with exacerbated inflammatory responses in autoimmunity and graft rejection has been consistently demonstrated, while more recent studies have suggested a role for this population in other immune-related conditions, such as infections, allergy, cancer, and chronic metabolic diseases. Initial studies identified IL-10 as the hallmark of Breg function; nevertheless, the past decade has seen the discovery of other molecules utilized by human and murine B cells to regulate immune responses. This new arsenal includes other anti-inflammatory cytokines such IL-35 and TGF-β, as well as cell surface proteins like CD1d and PD-L1. In this review, we examine the main suppressive mechanisms employed by these novel Breg populations. We also discuss recent evidence that helps to unravel previously unknown aspects of the phenotype, development, activation, and function of IL-10-producing Bregs, incorporating an overview on those questions that remain obscure.

Mining Helminths for Novel Therapeutics

Helminths are an emerging source of therapeutics for dysregulated inflammatory diseases. Excretory/secretory (ES) molecules, released during infection, are responsible for many of these immunomodulatory effects and are likely to have evolved as a means for parasite survival in the host. While the mechanisms of action of these molecules have not been fully defined, evidence demonstrates that they target various pathways in the immune response, ranging from initiation to effector cell modulation. These molecules are applied in controlling specific effector mechanisms of type 1 and type 2 immune responses. Recently, studies have further focused on their therapeutic potential in specific disease models. Here we review recent findings on ES molecule modulation of immune functions, specifically highlighting their clinical implications for future use in inflammatory disease therapeutics.

The therapeutic implications of activated immune responses via the enigmatic immunoglobulin D

Immunoglobulin D (IgD) is an enigmatic antibody and the least appreciated member of the immunoglobulin (Ig) family. Since its discovery over half a century ago, the essence of its function in the immune system has been somewhat enigmatic and less well-defined than other antibody classes. Membrane-bound IgD (mIgD) is mostly recognized as B-cell receptor (BCR) while secreted IgD (sIgD) has been recently implicated in 'arming' basophils and mast cells in mucosal innate immunity. Activations of immune responses via mIgD-BCR or sIgD by specific antigens or anti-IgD antibody thereby produce a broad and complex mix of cellular, antibody and cytokine responses from both the innate and adaptive immune systems. Such broadly activated immune responses via IgD were initially deemed to potentiate and exacerbate the onset of autoimmune and allergic conditions. Paradoxically, treatments with anti-IgD antibody suppressed and ameliorated autoimmune conditions and allergic inflammations in mouse models without compromising the host's general immune defence, demonstrating a unique and novel therapeutic application for anti-IgD antibody treatment. Herein, this review endeavored to collate and summarize the evidence of the unique characteristics and features of activated immune responses via mIgD-BCR and sIgD that revealed an unappreciated immune-regulatory function of IgD in the immune system via an amplifying loop of anti-inflammatory Th2 and tolerogenic responses, and highlighted a novel therapeutic paradigm in harnessing these immune responses to treat human autoimmune and allergic conditions.

B cells and the microbiota: a missing connection in food allergy

Food allergies are a major public health concern due to their widespread and rising prevalence. The increase in food allergy is partially due to Western lifestyle habits which deplete protective commensal microbiota. These microbial perturbations can result in adverse host-microbe interactions, altering the phenotype of various immune cells and instigating allergic sensitization. Although B cells are critical to allergic pathology, microbial influences on B cells have been somewhat overlooked. Here, we focus on direct and indirect interactions between bacteria and B cells and how such interactions regulate B-cell phenotype, namely antibody production (IgA, IgE, IgG1, and IgG4) and regulatory B-cell (Breg) function. Understanding how microbes modulate B-cell activity in the context of food allergies is critical to both tracing the development of disease and assessing future treatment options.

B regulatory cells in allergy

B cells have classically been recognized for their unique and indispensable role in the production of antibodies. Their potential as immunoregulatory cells with anti-inflammatory functions has received increasing attention during the last two decades. Herein, we highlight pioneering studies in the field of regulatory B cell (Breg) research. We will review the literature on Bregs with a particular focus on their role in the regulation of allergic inflammation.

Inflammaging in Endemic Areas for Infectious Diseases

Immunosenescence is marked by a systemic process named inflammaging along with a series of defects in the immunological activity that results in poor responses to infectious agents and to vaccination. Inflammaging, a state of low-grade chronic inflammation, usually leads to chronic inflammatory diseases and frailty in the elderly. However, some elderly escape from frailty and reach advanced age free of the consequences of inflammaging. This process has been called immunological remodeling, and it is the hallmark of healthy aging as described in the studies of centenarians in Italy. The biological markers of healthy aging are still a matter of debate, and the studies on the topic have focused on inflammatory versus remodeling processes and molecules. The sub-clinical inflammatory status associated with aging might be a deleterious event for populations living in countries where chronic infectious diseases are not prevalent. Nevertheless, in other parts of the world where they are, two possibilities may occur. Inflammatory responses may have a protective effect against these infectious agents. At the same time, the long-term consequences of protective immune responses during chronic infections may result in accelerated immunosenescence in these individuals. Therefore, the biological markers of healthy aging can vary according to environmental, cultural, and geographical settings that reflect worldwide, and in a non-biased, non-westernized perspective, the changes that we experience regarding our contacts with microorganisms and the outcomes of such contacts.

Dirofilaria immitis Could Be a Risk Factor for the Development of Allergic Diseases in Humans

Simple Summary

Heartworm is a parasitic infection transmitted by mosquitoes to animals and humans. The risk of human infections is high in those areas with high canine prevalence, such as the Canary Islands. In these islands, there is also a high number of allergic inhabitants. Since some studies have shown a relationship between parasite infections and development of allergies, the aim of this study was to evaluate whether exposure to heartworm may contribute to the development of allergies. A survey carried out on dog owners in the Canary Islands showed that 51.3% of allergic owners had a heartworm-positive dog, and significant differences were found between allergic or not-allergic owners, according to whether the dog was negative or positive to heartworm. Furthermore, 66 serum samples from inhabitants of the Canary Islands were analyzed for the presence of unspecific allergy markers (Immunoglobulin E or IgE) and specific for heartworm (IgE against Dirofilaria immitis and Wolbachia) and the results show that people who were in contact with heartworm showed total IgE and specific IgE against heartworm more frequently. Contact with heartworm may be a risk factor for the development of allergic diseases, although further studies to elucidate the relationship between heartworm and allergies should be carried out.

Abstract

The Canary Islands are hyperendemic for canine heartworm and the risk of zoonotic infection is high. Additionally, there is evidence of development of allergies due to nematode infections in animals and humans. Since the population of the Canary Islands presents high prevalence of allergic comorbidities, and previous studies have shown a possible relationship between allergies and seropositivity to heartworm, the aim was to evaluate whether exposure to heartworm may contribute to the development of allergies in the human population. First, an epidemiological study was conducted on 248 owners of dogs with/without heartworm infection in the Canary Islands. Secondly, a serological analysis of the presence of total IgE and specific IgE against heartworm was conducted in 66 samples of inhabitants of the Canary Islands. The survey showed that allergic owners had heartworm-positive dogs more frequently (p < 0.01). Of the analyzed human samples, 43.9% were seropositive to heartworm and Wolbachia. Total IgE concentrations were increased in 34.5% seropositive samples and 8.1% seronegative samples. Specific IgE against heartworm was only found in human seropositive samples (17.2%). Contact with heartworm may be a risk factor for the development of allergic diseases, although further studies to elucidate the relationship between heartworm and allergies should be carried out.

What Can Parasites Tell Us About the Pathogenesis and Treatment of Asthma and Allergic Diseases

The same mechanisms that enable host defense against helminths also drive allergic inflammation. This suggests that pathomechanisms of allergic diseases represent evolutionary old responses against helminth parasites and that studying antihelminth immunity may provide insights into pathomechanisms of asthma. However, helminths have developed an intricate array of immunoregulatory mechanisms to modulate type 2 immune mechanisms. This has led to the hypothesis that the lack of helminth infection may contribute to the rise in allergic sensitization in modern societies. Indeed, the anti-inflammatory potential of helminth (worm) parasites and their products in allergy and asthma has been recognized for decades. As helminth infections bring about multiple undesired effects including an increased susceptibility to other infections, intended helminth infection is not a feasible approach to broadly prevent or treat allergic asthma. Thus, the development of new helminth-based biopharmaceutics may represent a safer approach of harnessing type 2–suppressive effects of helminths. However, progress regarding the mechanisms and molecules that are employed by helminths to modulate allergic inflammation has been relatively recent. The scavenging of alarmins and the modulation of lipid mediator pathways and macrophage function by helminth proteins have been identified as important immunoregulatory mechanisms targeting innate immunity in asthma and allergy. In addition, by regulating the activation of dendritic cells and by promoting regulatory T-cell responses, helminth proteins can counterregulate the adaptive T helper 2 cell response that drives allergic inflammation. Despite these insights, important open questions remain to be addressed before helminth molecules can be used for the prevention and treatment of asthma and other allergic diseases.

Harnessing helminth-driven immunoregulation in the search for novel therapeutic modalities

Parasitic helminths have coevolved with humans over millennia, intricately refining and developing an array of mechanisms to suppress or skew the host’s immune system, thereby promoting their long-term survival. Some helminths, such as hookworms, cause little to no overt pathology when present in modest numbers and may even confer benefits to their human host. To exploit this evolutionary phenomenon, clinical trials of human helminth infection have been established and assessed for safety and efficacy for a range of immune dysfunction diseases and have yielded mixed outcomes. Studies of live helminth therapy in mice and larger animals have convincingly shown that helminths and their excretory/secretory products possess anti-inflammatory drug-like properties and represent an untapped pharmacopeia. These anti-inflammatory moieties include extracellular vesicles, proteins, glycans, post-translational modifications, and various metabolites. Although the concept of helminth-inspired therapies holds promise, it also presents a challenge to the drug development community, which is generally unfamiliar with foreign biologics that do not behave like antibodies. Identification and characterization of helminth molecules and vesicles and the molecular pathways they target in the host present a unique opportunity to develop tailored drugs inspired by nature that are efficacious, safe, and have minimal immunogenicity. Even so, much work remains to mine and assess this out-of-the-box therapeutic modality. Industry-based organizations need to consider long-haul investments aimed at unraveling and exploiting unique and differentiated mechanisms of action as opposed to toe-dipping entries with an eye on rapid and profitable turnarounds.

Important Role of Immunological Responses to Environmental Exposure in the Development of Allergic Asthma

Allergic asthma is a public health problem that affects human health and socioeconomic development. Studies have found that the prevalence of asthma has significantly increased in recent years, which has become particularly pronounced in developed countries. With rapid urbanization in China in the last 3 decades, the prevalence of asthma has increased significantly in urban areas. As changes in genetic backgrounds of human populations are limited, environmental exposure may be a major factor that is responsible for the increased prevalence of asthma. This review focuses on environmental components of farms and rural areas that may have protective effects in reducing the development of asthma. Farm and rural related microorganism- and pathogen-associated molecular patterns are considered to be important environmental factors that modulate host's innate and adaptive immune system to induce protection effects later in life. Environmental microbial-related immunotherapy will also be discussed as the future research direction for the prevention of allergic asthma.