Allergen Challenge Research Articles

Fetal microchimeric cells influence maternal lung health following term and preterm births

Fetal microchimerism, the presence of fetal cells in maternal tissues, has garnered interest for its potential role in maternal physiology. In this study, we aimed to explore the impact of fetal microchimeric cells on maternal lung health following term and preterm delivery, particularly in the context of infection-induced preterm birth and subsequent allergic challenges. We characterized the immune cells in maternal lungs using a transgenic mouse model (mT+ Ve, Td Tomato) and high dimensional mass cytometry (CyTOF) techniques. We evaluated their influence on lung function and inflammation. Our findings revealed distinct differences in the immune cell composition of maternal lungs between term and preterm deliveries. Mice delivered preterm significantly increased in fetal-specific cells, such as activated macrophages and Tbet + Ve memory B-cells, compared to term-delivered mice. Conversely, term deliveries showed elevated levels of CD4 cells. Furthermore, preterm-delivered dams demonstrated heightened airway hyperresponsiveness, pro-inflammatory cytokine expression, cellular infiltration, and lung mucous production compared to term-delivered dams. Co-culture experiments demonstrated that microchimeric cells from preterm births stimulated the production of inflammatory cytokines IL-6 and TNF-α in lung epithelial cells. These findings shed light on the complex immune dynamics postpartum and their role in lung complications after preterm birth. Understanding these mechanisms could provide insights for targeted interventions to improve maternal lung health in at-risk populations.

Investigation of the diagnostic accuracy of basophil activation test for allergic phenotypes of rhinitis.

Basophil activation test (BAT) might be an alternative to nasal allergen challenge (NAC) to identify the allergic etiology in rhinitis patients. Here, we investigate the diagnostic performance of BAT for allergic phenotypes of rhinitis. Rhinitis patients and healthy controls were subjected to NAC with Dermatophagoides pteronyssinus (DP), Alternaria alternata (AA), grass (GP) and olive (OP) pollens. Rhinitis subjects also underwent skin prick test (SPT) with relevant allergens. Patients were classified into allergic rhinitis (AR, positive NAC and SPT), local allergic rhinitis (LAR, positive NAC and negative SPT), dual allergic rhinitis (DAR, defined as AR for ≥1 allergen and LAR for ≥1 allergen), and non-allergic rhinitis (NAR, negative NAC and SPT) phenotypes. BAT with DP, AA, GP and OP was conducted in study individuals and compared with NAC results. A total of 47 AR, 31 DAR, 26 LAR, 12 NAR and 21 control subjects were recruited. The best positivity cut-offs of BAT for DP-, AA-, GP- and OP-driven allergy (all phenotypes) were a %CD63 cells of 8.650, 14.250, 26.200, and 12.780, respectively (AUC 0.851, 0.701, 0.887, and 0.921, respectively). Sensitivity, specificity, negative and positive predictive values of BAT (all phenotypes) ranged 43.5%(AA)-83.3%(OP), 88.9%(GP)-100%(AA), 87%(GP)-100%(AA), and 61.1%(DP)-80.0%(pollens), respectively. BAT identified 79%-100% of SPT-positive allergies (AR and DAR), and 25%-75% of SPT-negative allergies (LAR and DAR), while ≤10% of NAR/HC subjects tested positive. BAT positivity correlated with rhinitis severity in LAR patients (p = 0.018), and associated with conjunctivitis (p = 0.015) in allergic subjects. BAT can replace NAC for AR confirmation, and limit the number of NAC required for LAR and DAR diagnosis. BAT can demonstrate sIgE in SPT-negative allergies.

Nasal allergen challenge with Blomia tropicalis in children and adolescents.

Local allergic rhinitis (LAR) is a well-defined phenotype in adults, but still there is little data available on children. This scarcity of data can be partly attributed to the lack of standardized protocols for Nasal Allergen Challenges (NAC) in this demographic. 20 controls (control group) and 24 patients (rhinitis group) with allergic rhinitis diagnosis sensitized to Blomia tropicalis (Bt) underwent the NAC with Bt. The acoustic rhinometry was performed after instillation of increasing concentrations of Bt (5,000 BU/mL). The median reduction in the volume of the nasal cavity in its first five centimeters (V5) by the conclusion of the NAC in the rhinitis group was markedly higher than that observed in the control group, at -22.9% (range: -21.1% to -26.2%) compared to -7.7% (ranging: -4.8% to +12.8%). Our research demonstrates the efficacy and safety of the NAC protocol utilizing Bt in distinguishing allergic from non-allergic children.

Eosinophil-Airway Epithelial Cells crosstalk reveals the eosinophils-mediated DUOX1 up-regulation in a murine allergic inflammation setting.

Blood and airway eosinophilia represent markers for the endotype-driven treatment of allergic asthma. Little is known on mechanisms that link eosinophils and airway epithelial cells before and after these cells are infiltrated by eosinophils during allergic response. Given that innate immune mechanisms, mainly mediated by epithelial-derived cytokines (IL-33, IL-25, TSLP), induce eosinophil-maturing/attractive substances, we thought to evaluate the crosstalk between eosinophils and airway epithelial cells in the context of IL-33-mediated allergic inflammation. DUOX1 was previously described in clinically relevant aspects of allergic inflammation in a HDM -induced allergic asthma mice model, and in patients with chronic sinusitis or allergic asthma. Thus, we evaluated the involvement of HDM and eosinophils in the regulation of DUOX1 in airway epithelial cells. To recapitulate the lung environment present at the allergen challenge time in acute asthma, we set up an in vitro model based on murine bone marrow-derived eosinophils differentiated with IL-5 and then activated with IL-33 (EOs33) and TC1 or C57 airway epithelial cells. We found that treatment of epithelial cells with HDM induced an eosinophil-attractive environment and increased DUOX1 expression. Importantly, we found that the co-culture of airway epithelial cells with EOs33 or with conditioned medium from EOs33 enhanced the expression of DUOX1, which was further increased by combined stimulation (HDM plus EOs33). Our results suggest that lung recruited EOs once activated by IL-33 could be involved in a crosstalk loop with airway epithelial cells by DUOX1-mediated IL-33 secretion.

Investigation into the Effects of Allergen Exposure and Topical Vinegar and Water Spray on Skin Barrier Parameters in Atopic Dogs.

Increased skin pH and transepidermal water loss (TEWL) are documented in atopic people and dogs but no study has investigated how these parameters change during an allergy flare. Our primary aim was to challenge atopic beagles to dust mites and measure pH and TEWL during a flare of atopic dermatitis and correlate these parameters to clinical signs. A secondary aim was to evaluate in a randomized placebo-controlled study whether the daily application of 50/50 vinegar spray improves clinical signs and affects skin parameters despite the allergen challenge. Fifteen atopic dogs were challenged epicutaneously twice weekly for 2 weeks with allergen application on the inguinal and medial thigh areas. The severity of dermatitis was scored daily (CADESI-03). TEWL and pH were measured daily on the inguinal and medial thigh areas. A repeated measures ANOVA showed the significant effect of time, with increased pH (p < 0.0001), TEWL (p < 0.0001), and CADESI (p < 0.0001) during allergen challenge. Significant positive correlations were found between CADESI and pH (r = 0.3556; p < 0.0001), CADESI and TEWL (r = 0.36; p < 0.0001), and pH and TEWL (r = 0.45; p < 0.0001). Daily application of 50/50 vinegar did not improve dermatitis, pH, and TEWL compared to the control treatment. It can be concluded that both pH and TEWL are markers of disease severity in canine atopic dermatitis.

Nasal allergen and methacholine provocation tests influence co‑expression patterns of TGF‑β/SMAD and MAPK signaling pathway genes in patients with asthma.

Asthma is characterized by chronic bronchial inflammation and is a highly heterogeneous disease strongly influenced by both specific and non-specific exogenous factors. The present study was performed to assess the effect of nasal allergen provocation tests and methacholine provocation tests on the mRNA co-expression patterns of genes (SMAD1/3/6/7, MPK1/3 and TGFB1/3) involved in SMAD and non-SMAD TGF-β signaling pathways in patients with asthma. Reverse transcription-quantitative PCR was performed on blood samples taken pre-provocation and 1 h post-provocation to assess gene expression changes. Of the 59 patients studied, allergen provocations were administered to 27 patients and methacholine provocations to 32 patients. Correlations between expression levels of studied genes were found to be influenced markedly by the challenge administered, challenge test result and time elapsed since challenge. Importantly, increases in expression levels for four gene pairs (MAPK1-SMAD3, MAPK3-SMAD3, SMAD1-SMAD3 and SMAD3-TGFB1) were found to correlate significantly with asthma occurrence in the allergen provocation cohort, but not in the methacholine provocation cohort. The present study allows us to draw the conclusion that both intranasal allergen and bronchial methacholine challenges influence mRNA co-expression patterns of the SMAD1/3/6/7, MPK1/3 and TGFB1/3 genes.

PreAlgPro: Prediction of allergenic proteins with pre-trained protein language model and efficient neutral network

Allergy is a prevalent phenomenon, involving allergens such as nuts and milk. Avoiding exposure to allergens is the most effective preventive measure against allergic reactions. However, current homology-based methods for identifying allergenic proteins encounter challenges when dealing with non-homologous data. Traditional machine learning approaches rely on manually extracted features, which lack important protein functional characteristics, including evolutionary information. Consequently, there is still considerable room for improvement in existing methods. In this study, we present PreAlgPro, a method for identifying allergenic proteins based on pre-trained protein language models and deep learning techniques. Specifically, we employed the ProtT5 model to extract protein embedding features, replacing the manual feature extraction step. Furthermore, we devised an Attention-CNN neural network architecture to identify potential features that contribute to the classification of allergenic proteins. The performance of our model was evaluated on four independent test sets, and the experimental results demonstrate that PreAlgPro surpasses existing state-of-the-art methods. Additionally, we collected allergenic protein samples to validate the robustness of the model and conducted an analysis of model interpretability.

Interleukin-33-activated basophils promote asthma by regulating Th2 cell entry into lung tissue.

Asthma is characterized by lung eosinophilia, remodeling, and mucus plugging, controlled by adaptive Th2 effector cells secreting IL-4, IL-5, and IL-13. Inhaled house dust mite (HDM) causes the release of barrier epithelial cytokines that activate various innate immune cells like DCs and basophils that can promote Th2 adaptive immunity directly or indirectly. Here, we show that basophils play a crucial role in the development of type 2 immunity and eosinophilic inflammation, mucus production, and bronchial hyperreactivity in response to HDM inhalation in C57Bl/6 mice. Interestingly, conditional depletion of basophils during sensitization did not reduce Th2 priming or asthma inception, whereas depletion during allergen challenge did. During the challenge of sensitized mice, basophil-intrinsic IL-33/ST2 signaling, and not FcεRI engagement, promoted basophil IL-4 production and subsequent Th2 cell recruitment to the lungs via vascular integrin expression. Basophil-intrinsic loss of the ubiquitin modifying molecule Tnfaip3, involved in dampening IL-33 signaling, enhanced key asthma features. Thus, IL-33-activated basophils are gatekeepers that boost allergic airway inflammation by controlling Th2 tissue entry.

Benralizumab for allergic asthma: a randomised, double-blind, placebo-controlled trial.

Benralizumab induces rapid and near-complete depletion of eosinophils from blood and lung tissue. We investigated whether benralizumab could attenuate the allergen-induced late asthmatic response (LAR) in participants with allergic asthma. Participants with allergic asthma who demonstrated increased sputum eosinophils and LAR at screening were randomised to benralizumab 30 mg or matched placebo given every 4 weeks for 8 weeks (3 doses). Allergen challenges were performed at weeks 9 and 12 when blood, sputum, bone marrow and bronchial tissue eosinophils and LAR were assessed. 46 participants (mean age 30.9 years) were randomised to benralizumab (n=23) or placebo (n=23). Eosinophils were significantly reduced in the benralizumab group compared with placebo in blood at 4 weeks and sputum and bone marrow at 9 weeks after treatment initiation. At 7 h after an allergen challenge at week 9, sputum eosinophilia was significantly attenuated in the benralizumab group compared to placebo (least squares mean difference -5.81%, 95% CI -10.69- -0.94%; p=0.021); however, the LAR was not significantly different (least squares mean difference 2.54%, 95% CI 3.05-8.12%; p=0.363). Adverse events were reported for seven (30.4%) and 14 (60.9%) participants in the benralizumab and placebo groups, respectively. Benralizumab administration over 8 weeks resulted in a significant attenuation of blood, bone marrow and sputum eosinophilia in participants with mild allergic asthma; however, there was no change in the LAR, suggesting that eosinophils alone are not a key component of allergen-induced bronchoconstriction.

Allergen immunotherapy effectiveness in specific nasal reactivity of children with local allergic rhinitis.

Background.Allergen immunotherapy (AIT) is the only disease-modifying treatment in allergy. Its efficacy has been demonstrated in the treatment of Local Allergic Rhinitis (LAR) in adults. This study intends to evaluate the effectiveness of AIT in specific nasal reactivity of paediatric patients with LAR. Methods.Patients diagnosed with LAR to Dermatophagoides pteronyssinus (Dp) were submitted to subcutaneous AIT (SCIT) (depigmented-polymerized Dp allergen extracts) for 3 years. Nasal allergen challenge (NACs) with Dp extract were performed before and 3 years after AIT. NAC response was assessed with peak nasal inspiratory flow (PNIF) and symptom score of Lebel. NACs were considered positive when there was a flow decrease of ≥ 20% in PNIF and a score of symptoms ≥ 3 points. Demographic data and NAC results were analysed. Results.We included 32 paediatric patients (mean age 9.9±3.08 years, 18 female) and 10 adult patients, (mean age 30.4±12.2 years, 7 female). The symptom score obtained at the 1st minute, 5th minute, 15th minute and 30th minute in response to NAC, were reduced after AIT. The nasal inspiratory flow decrease induced by NAC was also reduced after AIT. This reduction in nasal reactivity was observed in paediatric and in adult patients, both with statistical significance. Conclusions.AIT induced a decrease in Dp-nasal specific reactivity in children with LAR. This decline of nasal response to allergen exposure, after AIT treatment, emphasis the interest of this therapeutic approach in LAR, even in paediatric patients.

The Efficacy and Safety of Dexamethasone Intracanalicular Insert Use in Patients with Chronic Seasonal/Perennial Allergic Conjunctivitis: A Systematic Review and Meta-Analysis.

This meta-analysis evaluated the efficacy and safety of DEXTENZA, an intracanalicular dexamethasone insert, for the treatment of seasonal/perennial allergic conjunctivitis. Multiple databases, including PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov, the Directory of Open Access Journals, and Scopus, were searched for randomized controlled trials (RCTs) comparing the efficacy of DEXTENZA with a placebo. The primary efficacy endpoint was the change in the conjunctival allergen challenge (CAC) model. The GRADE approach was used to assess the certainty of evidence, and the revised Cochrane risk of bias tool for randomized trials was employed to assess bias. Four RCTs involving 323 participants met the eligibility criteria, and all had a low risk of bias. A meta-analysis revealed a statistically significant increase in the mean CAC change for conjunctival itching, with low heterogeneity among measurements at 3 minutes (P<0.00001, I2=47%), 5 minutes (P<0.00001, I2=46%), and 7 minutes (P<0.00001, I2=41%). Additionally, the meta-analysis found a statistically significant increase in the mean CAC change for conjunctival redness with low heterogeneity (P<0.00001, I2=15%). The pooled analysis showed no significant difference (P=0.57, I2=0%) between the DEXTENZA and placebo groups in the frequency of adverse events. DEXTENZA has emerged as a promising and viable treatment option for patients with seasonal/perennial allergic conjunctivitis and is an effective alternative to current therapeutic modalities.

Allosteric inhibition of IgE–FcεRI interactions by simultaneous targeting of IgE F(ab’)2 epitopes

Immunoglobulin E (IgE) plays pivotal roles in allergic diseases through interaction with a high-affinity receptor (FcεRI). We established that Fab fragments of anti-IgE antibodies (HMK-12 Fab) rapidly dissociate preformed IgE-FcεRI complexes in a temperature-dependent manner and inhibit IgE-mediated anaphylactic reactions, even after allergen challenge. X-ray crystallographic studies revealed that HMK-12 Fab interacts with each of two equivalent epitopes on the Cε2 homodimer domain involved in IgE F(ab’)2. Consequently, HMK-12 Fab-mediated targeting of Cε2 reduced the binding affinity of Fc domains and resulted in rapid removal of IgE from the receptor complex. This unexpected finding of allosteric inhibition of IgE-FcεRI interactions by simultaneous targeting of two epitope sites on the Cε2 homodimer domain of IgE F(ab’)2 may have implications for the development of novel therapies for allergic disease.

IL-2 family cytokines IL-9 and IL-21 differentially regulate innate and adaptive type 2 immunity in asthma

BackgroundAsthma is often accompanied by type 2 immunity rich in IL-4, IL-5 and IL-13 cytokines produced by TH2 lymphocytes or type 2 innate lymphoid cells (ILC2s). Interleukin-2 family cytokines play a key role in the differentiation, homeostasis and effector function of innate and adaptive lymphocytes. ObjectiveIL-9 and IL-21 boost the activation and proliferation of TH2 and ILC2s, but the relative importance and potential synergism between these γc cytokines is currently unknown. MethodsUsing newly generated antibodies, we inhibited IL-9 and IL-21 alone or in combination, in various murine models of asthma. In a translational approach using segmental allergen challenge, we recently described elevated IL-9 levels in human allergic asthmatics in comparison to non-asthmatic controls. Here, we also measured IL-21 in both groups. ResultsIL-9 played a central role in controlling innate IL-33 induced lung inflammation by promoting proliferation and activation of ILC2s, in an IL-21 independent manner. Conversely, chronic house dust mite induced airway inflammation, mainly driven by adaptive immunity, was solely dependent on IL-21, that controlled TH2 activation, eosinophilia, total serum IgE and formation of tertiary lymphoid structures. In a model of innate on adaptive immunity driven by papain allergen, a clear synergy was found between both pathways, since combined anti-IL-9 or anti-IL-21 blockade was superior in reducing key asthma features. In human bronchoalveolar lavage (BAL) samples we measured elevated IL-21 protein within the allergic asthmatic group, compared with the allergic control group. We also found increased IL21R transcripts and predicted IL-21 ligand activity in various disease-associated cell subsets. ConclusionIL-9 and IL-21 play important and non-redundant roles in allergic asthma by boosting ILC2s and TH2 cells, revealing a dual IL-9 and IL-21 targeting strategy as a new and testable approach.

ILC2-derived LIF licences progress from tissue to systemic immunity

Migration and homing of immune cells are critical for immune surveillance. Trafficking is mediated by combinations of adhesion and chemokine receptors that guide immune cells, in response to chemokine signals, to specific locations within tissues and the lymphatic system to support tissue-localized immune reactions and systemic immunity1,2. Here we show that disruption of leukaemia inhibitory factor (LIF) production from group 2 innate lymphoid cells (ILC2s) prevents immune cells leaving the lungs to migrate to the lymph nodes (LNs). In the absence of LIF, viral infection leads to plasmacytoid dendritic cells (pDCs) becoming retained in the lungs where they improve tissue-localized, antiviral immunity, whereas chronic pulmonary allergen challenge leads to marked immune cell accumulation and the formation of tertiary lymphoid structures in the lung. In both cases immune cells fail to migrate to the lymphatics, leading to highly compromised LN reactions. Mechanistically, ILC2-derived LIF induces the production of the chemokine CCL21 from lymphatic endothelial cells lining the pulmonary lymphatic vessels, thus licensing the homing of CCR7+ immune cells (including dendritic cells) to LNs. Consequently, ILC2-derived LIF dictates the egress of immune cells from the lungs to regulate tissue-localized versus systemic immunity and the balance between allergen and viral responsiveness in the lungs.

Itaconate suppresses house dust mite-induced allergic airways disease and Th2 cell differentiation

Itaconate was initially identified as an antimicrobial compound produced by myeloid cells. Beyond its antimicrobial role, itaconate may also serve as a crucial metabolic and immune modulator. We therefore examined the roles of aconitate decarboxylase 1 (Acod1) and itaconate in house dust mite (HDM)-sensitized and −challenged mice, a model of T helper 2 (Th2)-driven allergic airways disease. HDM treatment induced lung Acod1 mRNA expression and bronchoalveolar lavage (BAL) itaconate levels in wild-type C57BL/6 mice. Acod1 knockout mice (Acod1-KO) with negligible BAL itaconate showed heightened HDM-induced type 2 cytokine expression, increased serum IgE, and enhanced recruitment of Th2 cells in the lung, indicating a shift towards a more pronounced Th2 immune response. Acod1-KO mice also showed increased eosinophilic airway inflammation and hyperresponsiveness. Experiments in chimeric mice demonstrated that bone marrow from Acod1-KO mice is sufficient to increase type 2 cytokine expression in wild-type mice, and that restitution of bone marrow from wild type mice attenuates mRNA expression of Th2 cytokines in Acod1-KO mice. Specific deletion of Acod1 in lysozyme-secreting macrophages (LysM-cre+Acod1flox/flox) recapitulated the exaggerated phenotype observed in whole-body Acod1-KO mice. Adoptive transfer of Acod1-KO bone marrow-derived macrophages also increased lung mRNA expression of Th2 cytokines. In addition, treatment of Th2-polarized CD4 cells with itaconate impeded Th2 cell differentiation, as shown by reduced expression of Gata3 and decreased release of IL-5 and IL-13. Finally, public datasets of human samples show lower Acod1 expression in subjects with allergic asthma, consistent with a protective role of itaconate in asthma pathogenesis. Together, these data suggest that itaconate plays a protective, immunomodulatory role in limiting airway type 2 inflammation after allergen challenge by attenuating T cell responses.

Local Allergic Rhinitis-A Challenge for Allergology and Otorhinolaryngology Cooperation (Scoping Review).

Local allergic rhinitis (LAR) represents a medical provocation for allergists and otorhinolaryngologists. LAR is considered to be a subtype of allergic rhinitis (AR) that affects a great percentage of patients who were, for decades, diagnosed as having chronic non-allergic rhinitis. The clinical picture is represented by rhinorrhea, sneezing, and nasal itching correlated with specific pollen season or dust, mold, or pet interior exposure. Usual assessment of AR (skin prick testing and serum IgE assessment) produces negative results. Specialized centers in allergology and ENT around the globe use a nasal allergen challenge, assessment of local IgE, basophil activation test (BAT), and nasal cytology in the diagnostic approach to the disease, taking into account their current limitations. The impact of LAR on quality-of-life indicators is the same as in AR. Treatment for LAR is similar to that for AR and is the same as for AR: allergen exposure avoidance, drug therapy, and allergen immunotherapy. This scoping review gathers the current up-to-date open access evidence available on PubMed on the subject of LAR.

Effect of benralizumab on inflammation in skin after intradermal allergen challenge in patients with moderate-to-severe atopic dermatitis

BackgroundAtopic dermatitis is a skin barrier dysfunction characterized by tissue eosinophilia. Objective: In patients with atopic dermatitis (AD) we evaluated the effect of eosinophil depletion with benralizumab on markers of inflammation in skin after intradermal allergen challenge. Methods20 patients with moderate to severe AD completed a randomized, double-blind, placebo-controlled parallel-group study comparing 3 doses q4wk 30 mg subcutaneous benralizumab (n=9) to placebo (n=11). Allergen and saline control intradermal challenges were conducted before and after treatment with skin biopsies collected 24 hours after challenge. Early (ECR) and late cutaneous responses (LAR) were measured by skin wheal size. Eosinophils and IL-5Rα -bearing cells including eosinophil progenitor cells (EoP), basophils and mast cells were measured in papillary dermis by immunofluorescence microscopy, and EoP, hemopoietic progenitor cells (HPC) and ILC2 were measured in blood by flow cytometry. Outcomes were compared between placebo and benralizumab treatment groups using Mann-Whitney U-test. ResultsBenralizumab reduced eosinophils in blood (p<0.0001), and allergen challenged skin as measured by H&E and EG2 (p<0.05). Benralizumab lowered levels of EoP, mast cells and basophil numbers in skin, as well as EoP, HPC and ILC2s in blood (all p<0.05). There was a trend for improvement in the ECR response (p=0.095), but no effect on the LCR. ConclusionIn patients with moderate to severe AD, benralizumab treatment significantly inhibited accumulation of eosinophils and other IL-5Rα expressing cells in the papillary dermis after intradermal allergen challenge. Targeting IL-5Rα positive cells did not modulate the size of the allergen-induced skin wheal. (ClincialTrials.gov number, NCT03563066).

Brainstem Dbh+ neurons control allergen-induced airway hyperreactivity

Exaggerated airway constriction triggered by repeated exposure to allergen, also called hyperreactivity, is a hallmark of asthma. Whereas vagal sensory neurons are known to function in allergen-induced hyperreactivity1–3, the identity of downstream nodes remains poorly understood. Here we mapped a full allergen circuit from the lung to the brainstem and back to the lung. Repeated exposure of mice to inhaled allergen activated the nuclei of solitary tract (nTS) neurons in a mast cell-, interleukin-4 (IL-4)- and vagal nerve-dependent manner. Single-nucleus RNA sequencing, followed by RNAscope assay at baseline and allergen challenges, showed that a Dbh+ nTS population is preferentially activated. Ablation or chemogenetic inactivation of Dbh+ nTS neurons blunted hyperreactivity whereas chemogenetic activation promoted it. Viral tracing indicated that Dbh+ nTS neurons project to the nucleus ambiguus (NA) and that NA neurons are necessary and sufficient to relay allergen signals to postganglionic neurons that directly drive airway constriction. Delivery of noradrenaline antagonists to the NA blunted hyperreactivity, suggesting noradrenaline as the transmitter between Dbh+ nTS and NA. Together, these findings provide molecular, anatomical and functional definitions of key nodes of a canonical allergen response circuit. This knowledge informs how neural modulation could be used to control allergen-induced airway hyperreactivity.

A synbiotic of Anaerostipes caccae and lactulose prevents and treats food allergy in mice

Depletion of beneficial microbes by modern lifestyle factors correlates with the rising prevalence of food allergies. Re-introduction of allergy-protective bacteria may be an effective treatment strategy. We characterized the fecal microbiota of healthy and food-allergic infants and found that the anaerobe Anaerostipes caccae (A.caccae) was representative of the protective capacity of the healthy microbiota. We isolated a strain of A.caccae from the feces of a healthy infant and identified lactulose as a prebiotic to optimize butyrate production by A.caccae invitro. Administration of a synbiotic composed of our isolated A.caccae strain and lactulose increased luminal butyrate in gnotobiotic mice colonized with feces from an allergic infant and in antibiotic-treated specific pathogen-free (SPF) mice, and prevented or treated an anaphylactic response to allergen challenge. The synbiotic's efficacy in two models and microbial contexts suggests that it may be a promising approach for the treatment of food allergy.

Bilastine 0.6% Preservative-free Eye Drops: A Once-daily Treatment for Allergic Conjunctivitis.

Bilastine is a second-generation antihistamine approved for the symptomatic treatment of allergic rhinoconjunctivitis and urticaria. The present trial evaluated the efficacy and safety of a new bilastine 0.6% preservative-free eye drop formulation for the symptomatic treatment of allergic conjunctivitis. This phase 3, multicenter, double-masked, randomized study compared the efficacy, safety, and tolerability profile of bilastine 0.6% ophthalmic solution with that of ketotifen 0.025% and vehicle. The primary efficacy endpoint was reduction in ocular itching. The Ora-CAC® Allergen Challenge Model was used to assess ocular and nasal symptoms at 15 minutes (onset of action) and 16 hours after treatment. Patients (N=228) were 59.6% male, and the mean (SD) age was 44.1 (13.4) years. Bilastine demonstrated efficacy in reducing ocular itching compared to vehicle at both onset of action and 16 hours after treatment (P<.001). Symptoms improved with ketotifen compared to vehicle 15 minutes after treatment (P<.001). Bilastine demonstrated statistical noninferiority to ketotifen for all 3 post-CAC timepoints at 15 minutes after instillation, based on an inferiority margin of 0.4. Compared with vehicle, bilastine improved in conjunctival redness, ciliary redness, episcleral redness, chemosis, eyelid swelling, tearing, rhinorrhea, ear and palate pruritus, and nasal congestion at 15 minutes after treatment (P<.05). Ophthalmic bilastine was safe and well tolerated. Mean drop comfort scores were significantly better for bilastine than for ketotifen immediately upon instillation (P<.05) and similar to those of vehicle. Ophthalmic bilastine effectively reduced ocular itching for 16 hours after administration, suggesting that it could be used as a once-daily treatment for the signs and symptoms of allergic conjunctivitis. ClinicalTrials.gov identifier: NCT03479307.