Sequential allergen desensitization of basophils is non-specific and may involve p38 MAPK

House dust mite induced mucosal barrier dysfunction and type 2 inflammatory responses via the MAPK/AP-1/IL-24 Signaling pathway in allergic rhinitis

The epithelial barrier, previously regarded only as a physical defense, is now understood to play a vital role in immune responses and the regulation of inflammation. Allergic rhinitis (AR) is a prevalent chronic inflammatory condition of the nasal mucosa, with House Dust Mite (HDM) identified as a significant inhalant allergen that can impair this barrier. IL-24 has emerged as a key cytokine in allergic diseases, involved in maintaining epithelial cell homeostasis. Nevertheless, the underlying mechanisms of these effects remain inadequately understood. This study explores HDM-induced IL-24 secretion and mucosal barrier impairment using patient and animal tissue samples. Our results confirm that HDM sensitization triggers inflammatory changes in the nasal cavity, with IL-24 acting as a key mediator of type 2 inflammation and AR severity. HDM enhances IL-24 secretion via the P38 MAPK pathway and transcription factor AP-1, while IL-24 downregulates occludin and ZO-1 expression through the STAT1/STAT3 signaling pathway, compromising barrier function and increasing permeability. Furthermore, IL-24 promotes IL-33 secretion, further exacerbating the inflammatory response in AR. These findings clarify the mechanisms of epithelial barrier disruption in HDM-sensitized allergic rhinitis and suggest that modulating the IL-24 signaling pathway may serve as a promising therapeutic strategy to restore barrier integrity in AR.

Inhibition of Allergic Reactivity through Targeting FcεRI-Bound IgE with Humanized Low-Affinity Antibodies

Options for effective prevention and treatment of epidemic allergic diseases remain limited, and particularly so for IgE-mediated food allergies. We previously found that mouse low-affinity anti-human IgE mAbs with K_D in the 10^-6-10^-8 M range were capable of blocking allergic reactivity without triggering immediate allergic mediator release. In this study, we humanized three parent low affinity allergic response inhibitor (LARI) mouse anti-human IgE mAbs and characterized their biological and immunological features, refined the lead candidate for further clinical development, examined their safety profiles, determined their therapeutic efficiency, and explored the mechanism of action potentially responsible for their therapeutic effects. LARI profoundly blocked cat- and peanut-allergic IgE-mediated basophil activation, inhibited acute release of both prestored and newly synthesized mediator from human mast cells, suppressed peanut-specific IgE-mediated passive cutaneous anaphylaxis, and attenuated dansyl IgE-mediated systemic anaphylaxis in human FcεRIα transgenic mice. Safety testing demonstrated that concentrations of LARI well above therapeutic levels failed to trigger immediate release of prestored and newly synthesized allergic mediators, failed to promote robust cytokine/chemokine production from allergic effector cells, and did not elicit allergic reactivity in an animal model of cutaneous and systemic anaphylaxis. Mechanistic studies revealed that LARI downregulated surface FcεRI receptors and IgE via internalization of the IgE/FcεRI, promoted a partial mediator depletion pathway leading to slow release of small amount of mediators, and functioned as a partial antagonist to inhibit FcεRI signaling phosphorylation of Syk, Akt, Erk, and p38 MAPK. These studies demonstrate that targeting surface-bound IgE with LARI profoundly suppresses human allergic reactivity while displaying an excellent safety profile.

Basophil Activation Test: Old and New Applications in Allergy

PURPOSE OF REVIEW

The basophil activation test (BAT) using flow cytometry has supplanted traditional methods of measuring basophil degranulation using histamine and other mediator release, and can be used for clinical applications as well as to explore the immune mechanisms of effector cell response to allergen. This review discusses the advancements made in clinical, diagnostic and laboratory research of allergy utilizing an ever-evolving BAT.

RECENT FINDINGS

Being an in vitro surrogate of the allergic reaction that happens in vivo in the sick patient, the BAT can be used to support the diagnosis of various allergic conditions, such as food, drug, respiratory and insect venom allergies, and the assessment of clinical response to allergen-specific immunotherapy and other immunomodulatory treatments. The BAT can also be used for research purposes to explore the mechanisms of allergy and tolerance at the level of the basophil, for instance by manipulating IgE and IgG and their receptors and by studying intracellular signalling cascade in response to allergen. This review covers the applications of the BAT to the clinical management of allergic patients and the increased understanding of the mechanisms of immune response to allergens as well as technological advancements made in recent years.

Changes in basophil activation during immunotherapy with house dust mite and mugwort in patients with allergic rhinitis

Background

The basophil activation test (BAT) is a promising tool for monitoring allergen-specific immunotherapy responses.

Objective

We aimed to investigate the changes in basophil activation in response to the inhalant allergens of house dust mite (HDM) and mugwort pollen during immunotherapy in patients with allergic rhinitis.

Methods

We enrolled patients with allergic rhinitis who were to receive subcutaneous immunotherapy for the inhalant allergens HDM or mugwort. A BAT was performed to assess CD63 upregulation in response to allergen stimulation using peripheral blood collected from the patients prior to immunotherapy and at 3, 6, 12, and 24 months after beginning immunotherapy. Rhinitis symptoms were evaluated using the rhinitis quality of life questionnaire (RQLQ) at 1-year intervals.

Results

Seventeen patients (10 with HDM sensitivity, 3 with mugwort sensitivity, and 4 with sensitivity to both HDM and mugwort) were enrolled in the study. Basophil reactivity to HDM did not change significantly during 24 months of immunotherapy. However, a significant reduction in basophil reactivity to mugwort was observed at 24-month follow-up. There was no significant association between the change in clinical symptoms by RQLQ and the change in basophil reactivity to either allergen. The change in allergen-specific basophil reactivity to HDM was well correlated with the change in nonspecific basophil activation induced by anti-FcεRI antibody, although basophil reactivity to anti-FcεRI antibody was not significantly reduced during immunotherapy.

Conclusion

Suppression of CD63 upregulation in the BAT was only observed with mugwort at 2-year follow-up. However, the basophil response did not reflect the clinical response to immunotherapy.

The role of basophils as innate immune regulatory cells in allergy and immunotherapy

Basophils are circulating cells that are associated quite exclusively with allergy response and hypersensitivity reactions but their role in the immune network might be much more intriguing and complex than previously expected. The feasibility of testing their biology in vitro for allergy research and diagnosis, due fundamentally to their quite easy availability in the peripheral blood, made them the major source for assessing allergy in the laboratory assay, when yet many further cells such as mast cells and eosinophils are much more involved as effector cells in allergy than circulating basophils. Interestingly, basophil numbers change rarely in peripheral blood during an atopic response, while we might yet observe an increase in eosinophils and modification in the biology of mast cells in the tissue during an hypersensitivity response. Furthermore, the fact that basophils are very scanty in numbers suggests that they should mainly serve as regulatory cells in immunity, rather than effector leukocytes, as still believed by the majority of physicians. In this review we will try to describe and elucidate the possible role of these cells, known as "innate IL4-producing cells" in the immune regulation of allergy and their function in allergen immunotherapy.

Pros and Cons of Clinical Basophil Testing (BAT)

PURPOSE OF REVIEW

We review basophil testing by flow cytometry with an emphasis on advantages and disadvantages.

RECENT FINDINGS

There are many tools available to assess the presence and severity of allergic diseases in patients. For 50 years, peripheral blood basophils have been used as tools to study these diseases. It is a very accessible cell that binds IgE antibody and secretes the classical mediators responsible for the symptoms of allergic reactions. In the last decade, an even more accessible methodology, using flow cytometry, has been developed to enhance the ability to use basophils for both mechanistic and clinical diagnostics. Basophil testing has been included in diagnostics for different forms of allergies as well as to monitor disease status. A variety of studies have begun to establish both precise methods and their clinical relevance for disease diagnosis, but there remain some important questions on how to take optimal advantage of the behaviours of basophils.

Novel approaches and perspectives in allergen immunotherapy

In this review, we report on relevant current topics in allergen immunotherapy (AIT) which were broadly discussed during the first Aarhus Immunotherapy Symposium (Aarhus, Denmark) in December 2015 by leading clinicians, scientists and industry representatives in the field. The aim of this symposium was to highlight AIT-related aspects of public health, clinical efficacy evaluation, mechanisms, development of new biomarkers and an overview of novel therapeutic approaches. Allergy is a public health issue of high socioeconomic relevance, and development of evidence-based action plans to address allergy as a public health issue ought to be on national and regional agendas. The underlying mechanisms are in the focus of current research that lays the ground for innovative therapies. Standardization and harmonization of clinical endpoints in AIT trials as well as current knowledge about potential biomarkers have substantiated proof of effectiveness of this disease-modifying therapeutic option. Novel treatments such as peptide immunotherapy, intralymphatic immunotherapy and use of recombinant allergens herald a new age in which AIT may address treatment of allergy as a public health issue by reaching a large fraction of patients.

Roxatidine attenuates mast cell-mediated allergic inflammation via inhibition of NF-κB and p38 MAPK activation

Roxatidine is an active metabolite of roxatidine acetate hydrochloride which is a histamine H₂-receptor antagonist that is used to treat gastric and duodenal ulcers. In this study, we investigated the anti-allergic inflammatory effects and the underlying molecular mechanism of roxatidine in phorbol 12-myristate 13-acetate and calcium ionophore (PMACI)-stimulated human mast cells-1 (HMC-1), compound 48/80-induced anaphylactic animal model and chemical allergen-induced contact hypersensitivity (CHS) models. Roxatidine suppressed the mRNA and protein expression of inflammatory cytokines such as TNF-α, IL-6, and IL-1β in PMACI-stimulated HMC-1 and compound 48/80-induced anaphylactic mice. In addition, roxatidine attenuated PMACI-induced nuclear translocation of NF-κB and the phosphorylation of MKK3/6 and MK2, which are both involved in the p38 MAPK pathway. Furthermore, we observed that roxatidine suppressed the activation of caspase-1, an IL-1β converting enzyme, in PMACI-stimulated HMC-1 and compound 48/80-induced anaphylactic mice. In CHS model, roxatidine significantly reduced ear swelling, increased number of mast cells, production levels of cytokines and migration of dendritic cells. Our findings provide evidence that the anti-allergic inflammatory properties of roxatidine are mediated by the inhibition of NF-κB and caspase-1 activation, p38 MAPK pathway and mast cell-derived cytokine production. Taken together, the in vitro and in vivo anti-allergic inflammatory effects suggest a possible therapeutic application of roxatidine in allergic inflammatory diseases.

Anti-Food Allergic Activity of Sulfated Polysaccharide from Gracilaria lemaneiformis is Dependent on Immunosuppression and Inhibition of p38 MAPK

Polysaccharides from Gracilaria lemaneiformis in particular possess various bioactive functions, but their antiallergic activity remains incompletely defined. Sulfated polysaccharide from Gracilaria lemaneiformis (GLSP) was obtained by water extraction and ethanol precipitation followed by column chromatography. BALB/c mice, RBL-2H3, and KU812 cells were used for verifying the anti food allergic activity of GLSP. According to the results of mice experiment, GLSP was able to alleviate allergy symptoms, to reduce TM-specific IgE and IgG1, to suppress Th2 cell polarization, and to promote the function of regulatory T (Treg) cells. In addition, GLSP had the ability to inhibit the function of RBL-2H3 cells. Furthermore, GLSP inhibited the activation of KU812 via suppression of p38 mitogen-activated protein kinase (MAPK). In conclusion, immunosuppression as well as the reduction in the level of p38 MAPK may contribute to GLSP's putative activity against food allergy. GLSP may be used as a functional food component for allergic patients.

Intralymphatic immunotherapy induces allergen specific plasmablasts and increases tolerance to skin prick testing in a pilot study

Background

Allergen Immunotherapy is a promising treatment of allergy. Seven patients with rhinoconjunctivitis to grass allergen were treated with intralymphatic immunotherapy (ILIT) to explore whether this treatment could be performed. Effect of treatment was assessed as change in symptom medication score, response in skin prick test and nasal allergen provocation. ILIT deposits allergen in an inguinal lymph node to elicit a strong immune stimulus. This allowed us to monitor appearance of allergen specific plasmablasts 7 days after allergen injection.

Findings

In an open trial of seven patients with a history of symptomatic allergic rhinoconjunctivitis due to grass pollen, three injections of allergen into inguinal lymph nodes were performed with monthly intervals. Allergen injections induced grass allergen specific plasmablasts expressing other isotypes than IgE after 7 days, induced a trend toward improvement in symptom and medication score and rhinoconjunctivitis-related quality of life during the grass pollen season 2013 and significantly raised the threshold in nasal allergen challenge and titrated skin prick testing. Mild side-effects were recorded after 3 of the 21 of injections (14 %).

Conclusions

This pilot study shows that ILIT may induce allergen specific plasmablasts, and confirms an effect on provocation of mast cells in skin and nasal mucosa during the ensuing winter.

Increasing time interval and decreasing allergen dose interval improves ex vivo desensitization of human blood basophils

BACKGROUND

Desensitization is a method for inducing temporary tolerance to allergen. The mechanism underlying desensitization is yet to be established.

METHODS

Basophil granulocytes in whole blood from grass pollen allergic subjects were desensitized ex vivo by sequential addition of increasing allergen concentrations. At each step basophil activation (CD193 ⁺ CD63⁺ ) was monitored with and without (background activation) allergen challenge at optimal concentration. The sequential desensitization protocol was compared to two single-dose desensitization protocols with threshold and subthreshold allergen concentrations. Incubation intervals and allergen concentrations were varied in order to optimise the protocol.

RESULTS

Sequential desensitization effectively reduced basophil response. The single-dose subthreshold protocol and single-dose threshold protocol did not reduce basophil activation with optimal allergen challenge from a mean 57.1 (95% CI: 32.7 - 81.5) to 50.4% (95% CI: 16.3 - 84.4; n = 5; P = 0.43) and 45.0% (95% CI: 23.1 - 66.9; P = 0.14) respectively, while the sequential desensitization protocol reduced activation to a mean 37.2% (95% CI: 16.3 - 58.1; P = 0.018). Reducing incubation time from 10 to 5 minutes increased mean background activation from 22.4 (95% CI: 11.7 - 33.1) to 30.0% (95% CI: 19.7 - 40.3; n = 5; P = 0.026). Increasing time intervals from 10 to 20 minutes reduced background activation from 30.9 (95% CI: 22.8 - 39.0) to 21.9% (95% CI: 16.0 - 27.7; n = 5; P = 0.020). Increasing allergen concentration intervals from 2-fold to 5- and 10-fold did not have significant effect on basophil activation.

CONCLUSIONS

Sequential desensitization ex vivo effectively attenuates the basophil response to allergen. Increasing the time spent at each step improves desensitization. This protocol could be valuable for investigation the mechanism of desensitization. © 2016 International Clinical Cytometry Society.

Latest developments in allergic rhinitis in Allergy for clinicians and researchers

Research efforts in allergic rhinitis have always been intense. Over the past 3 years, numerous breakthroughs in basic science and clinical research have been made, augmenting our understanding of this condition that afflicts a significant proportion of the global population. New epidemiological findings, novel insights into the molecular and cellular mechanisms of allergy, enhancement of current developmental theories, new concepts of the goals and endpoints of management, and latest therapeutic modalities that includes the harnessing of information technology and big data are some areas where important advances were made. We attempt to bring you a summary of the key research advances made in the field of allergic rhinitis from 2013 to 2015.

The clinical utility of basophil activation testing in diagnosis and monitoring of allergic disease

The basophil activation test (BAT) has become a pervasive test for allergic response through the development of flow cytometry, discovery of activation markers such as CD63 and unique markers identifying basophil granulocytes. Basophil activation test measures basophil response to allergen cross-linking IgE on between 150 and 2000 basophil granulocytes in <0.1 ml fresh blood. Dichotomous activation is assessed as the fraction of reacting basophils. In addition to clinical history, skin prick test, and specific IgE determination, BAT can be a part of the diagnostic evaluation of patients with food-, insect venom-, and drug allergy and chronic urticaria. It may be helpful in determining the clinically relevant allergen. Basophil sensitivity may be used to monitor patients on allergen immunotherapy, anti-IgE treatment or in the natural resolution of allergy. Basophil activation test may use fewer resources and be more reproducible than challenge testing. As it is less stressful for the patient and avoids severe allergic reactions, BAT ought to precede challenge testing. An important next step is to standardize BAT and make it available in diagnostic laboratories. The nature of basophil activation as an ex vivo challenge makes it a multifaceted and promising tool for the allergist. In this EAACI task force position paper, we provide an overview of the practical and technical details as well as the clinical utility of BAT in diagnosis and management of allergic diseases.