Immunologic characterization of 3 murine regimens of allergen-specific immunotherapy

International consensus statement on allergy and rhinology: Allergic rhinitis - 2023

BACKGROUND

In the 5 years that have passed since the publication of the 2018 International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis (ICAR-Allergic Rhinitis 2018), the literature has expanded substantially. The ICAR-Allergic Rhinitis 2023 update presents 144 individual topics on allergic rhinitis (AR), expanded by over 40 topics from the 2018 document. Originally presented topics from 2018 have also been reviewed and updated. The executive summary highlights key evidence-based findings and recommendation from the full document.

METHODS

ICAR-Allergic Rhinitis 2023 employed established evidence-based review with recommendation (EBRR) methodology to individually evaluate each topic. Stepwise iterative peer review and consensus was performed for each topic. The final document was then collated and includes the results of this work.

RESULTS

ICAR-Allergic Rhinitis 2023 includes 10 major content areas and 144 individual topics related to AR. For a substantial proportion of topics included, an aggregate grade of evidence is presented, which is determined by collating the levels of evidence for each available study identified in the literature. For topics in which a diagnostic or therapeutic intervention is considered, a recommendation summary is presented, which considers the aggregate grade of evidence, benefit, harm, and cost.

CONCLUSION

The ICAR-Allergic Rhinitis 2023 update provides a comprehensive evaluation of AR and the currently available evidence. It is this evidence that contributes to our current knowledge base and recommendations for patient evaluation and treatment.

Phenotype analyses of IL-10-producing Foxp3- CD4+ T cells increased by subcutaneous immunotherapy in allergic airway inflammation

INTRODUCTION

The mechanisms of allergen immunotherapy are not fully elucidated. Here, we sought to develop a murine model to demonstrate the effectiveness of subcutaneous immunotherapy (SCIT) for allergic responses. As excessive antigen dosages may induce immune tolerance in sensitized mice, the effects of SCIT were assessed by varying the antigen dosage. The mechanisms of SCIT were analyzed by focusing on the induction of Foxp3⁺ Treg cells and IL-10-producing Foxp3^- CD4⁺ T cells, as well as on the phenotype of the latter cells.

METHODS

Ovalbumin (OVA) + Al(OH)₃-sensitized mice received subcutaneous dosages of OVA at 0.01, 0.1 or 1 mg/animal for SCIT, followed by intratracheal challenges with OVA at 5, 50 or 500 μg/animal.

RESULTS

The maximum effects of SCIT were observed with 1 mg/animal of OVA for airway inflammation induced by 5 μg/animal of OVA, in which airway eosinophilia and Th2 cytokine production were markedly suppressed. The increase in the OVA-specific IgE level was significantly suppressed by SCIT. The development of bronchial epithelial thickening and mucus accumulation were also suppressed by SCIT. Concomitantly, IL-10-producing Foxp3^- CD4⁺ T cells were increased in the lungs by SCIT, but Foxp3⁺ Treg cells were not. Most of the induced IL-10-producing Foxp3^- CD4⁺ T cells were negative for either IL-5 or LAG-3, but positive for CD49b.

CONCLUSION

We successfully developed an airway allergic model for SCIT. It was suggested that most of IL-10-producing Foxp3^- CD4⁺ regulatory T cells increased by SCIT in the lungs were CD49b⁺ CD4⁺ regulatory T cells, but neither Th2 cells nor Tr1 cells.

International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis

BACKGROUND

Critical examination of the quality and validity of available allergic rhinitis (AR) literature is necessary to improve understanding and to appropriately translate this knowledge to clinical care of the AR patient. To evaluate the existing AR literature, international multidisciplinary experts with an interest in AR have produced the International Consensus statement on Allergy and Rhinology: Allergic Rhinitis (ICAR:AR).

METHODS

Using previously described methodology, specific topics were developed relating to AR. Each topic was assigned a literature review, evidence-based review (EBR), or evidence-based review with recommendations (EBRR) format as dictated by available evidence and purpose within the ICAR:AR document. Following iterative reviews of each topic, the ICAR:AR document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:AR document addresses over 100 individual topics related to AR, including diagnosis, pathophysiology, epidemiology, disease burden, risk factors for the development of AR, allergy testing modalities, treatment, and other conditions/comorbidities associated with AR.

CONCLUSION

This critical review of the AR literature has identified several strengths; providers can be confident that treatment decisions are supported by rigorous studies. However, there are also substantial gaps in the AR literature. These knowledge gaps should be viewed as opportunities for improvement, as often the things that we teach and the medicine that we practice are not based on the best quality evidence. This document aims to highlight the strengths and weaknesses of the AR literature to identify areas for future AR research and improved understanding.

Low-Dose Allergen-Specific Immunotherapy Induces Tolerance in a Murine Model of Shrimp Allergy

BACKGROUND

The efficacy and safety of allergen-specific immunotherapy (AIT) are highly dose-dependent.

METHODS

We investigated the dosage effects of AIT and the underlying mechanisms in a murine model of shrimp hypersensitivity. BALB/c mice were sensitized with recombinant shrimp allergen rMet e 1 and challenged orally with a high dose of rMet e 1 to elicit an allergic response. These sensitized mice were then treated with a low (0.01 mg), medium (0.05 mg), or high dosage (0.1 mg) of rMet e 1 intraperitoneally before receiving a second oral challenge. The allergic responses and immunological changes in the gut were compared between animals receiving different dosages.

RESULTS

We found that all sensitized mice that received rMet e 1 immunotherapy were desensitized, regardless of the dosage, and protected at the second oral challenge. Nevertheless, the mice in the high-dosage group experienced severe systemic reactions during the treatment phase. In contrast, regulatory T (Treg) cell-associated genes were upregulated only in the low- and medium-dosage groups, and Foxp3+ cells were more abundant in the gut lymphoid tissues than in the high-dosage group.

CONCLUSIONS

Our results demonstrate that low-dosage immunotherapy favors the induction of local Foxp3+ Treg cells and the upregulation of regulatory cytokines. The safety advantages and long-term efficacy of low-dosage immunotherapy should be taken into consideration when developing immunotherapy dose schedules.

Advances in allergen immunotherapy in 2015

The year 2015 saw a significant number of advances in allergen immunotherapy (AIT), and several of these are reviewed in this report. Although AIT has been used for more than 100 years, investigations into optimal treatment approaches and mechanisms are ongoing. Among the highlights was a report by an international group of experts who reviewed AIT guidelines from the major specialty societies and addressed potential unmet needs. Herein, advances in the effectiveness, safety, and mechanisms of sublingual and oral immunotherapy are reviewed. Development of hypoallergenic vaccines to enhance safety, newer routes and regimens to improve efficacy, and biomarkers to monitor immunotherapy are also discussed.

The Three-Herb Formula Shuang-Huang-Lian stabilizes mast cells through activation of mitochondrial calcium uniporter

Mast cells (MCs) are key effector cells of IgE-FcεRI- or MrgprX2-mediated signaling event. Shuang-Huang-Lian (SHL), a herbal formula from Chinese Pharmacopoeia, has been clinically used in type I hypersensitivity. Our previous study demonstrated that SHL exerted a non-negligible effect on MC stabilization. Herein, we sought to elucidate the molecular mechanisms of the prominent anti-allergic ability of SHL. MrgprX2- and IgE-FcεRI-mediated MC activation in vitro and in vivo models were developed by using compound 48/80 (C48/80) and shrimp tropomyosin (ST), respectively. Our data showed that SHL markedly dampened C48/80- or ST-induced MC degranulation in vitro and in vivo. Mechanistic study indicated that cytosolic Ca²⁺ (Ca²⁺_[c]) level decreased rapidly and sustainably after SHL treatment, and then returned to homeostasis when SHL was withdrawn. Moreover, SHL decreases Ca²⁺_[c] levels mainly through enhancing the mitochondrial Ca²⁺ (Ca²⁺_[m]) uptake. After genetically silencing or pharmacologic inhibiting mitochondrial calcium uniporter (MCU), the effect of SHL on the Ca²⁺_[c] level and MC degranulation was significantly weakened. Simultaneously, the activation of SHL on Ca²⁺_[m] uptake was completely lost. Collectively, by activating MCU, SHL decreases Ca²⁺_[c] level to stabilize MCs, thus exerting a remarkable anti-allergic activity, which could have considerable influences on clinical practice and research.

Factor XI deficiency enhances the pulmonary allergic response to house dust mite in mice independent of factor XII

Asthma is associated with activation of coagulation in the airways. The coagulation system can be initiated via the extrinsic tissue factor-dependent pathway or via the intrinsic pathway, in which the central player factor XI (FXI) can be either activated via active factor XII (FXIIa) or via thrombin. We aimed to determine the role of the intrinsic coagulation system and its possible route of activation in allergic lung inflammation induced by the clinically relevant human allergen house dust mite (HDM). Wild-type (WT), FXI knockout (KO), and FXII KO mice were subjected to repeated exposure to HDM via the airways, and inflammatory responses were compared. FXI KO mice showed increased influx of eosinophils into lung tissue, accompanied by elevated local levels of the main eosinophil chemoattractant eotaxin. Although gross lung pathology and airway mucus production did not differ between groups, FXI KO mice displayed an impaired endothelial/epithelial barrier function, as reflected by elevated levels of total protein and IgM in bronchoalveolar lavage fluid. FXI KO mice had a stronger systemic IgE response with an almost completely absent HDM-specific IgG₁ response. The phenotype of FXII KO mice was, except for a higher HDM-specific IgG₁ response, similar to that of WT mice. In conclusion, FXI attenuates part of the allergic response to repeated administration of HDM in the airways by a mechanism that is independent of activation via FXII.

International Consensus on Allergen Immunotherapy II: Mechanisms, standardization, and pharmacoeconomics

This article continues the comprehensive international consensus (ICON) statement on allergen immunotherapy (AIT). The initial article also recently appeared in the Journal. The conclusions below focus on key mechanisms of AIT-triggered tolerance, requirements in allergen standardization, AIT cost-effectiveness, and regulatory guidance. Potential barriers to and facilitators of the use of AIT are described in addition to future directions. International allergy specialists representing the European Academy of Allergy and Clinical Immunology; the American Academy of Allergy, Asthma & Immunology; the American College of Allergy, Asthma and Immunology; and the World Allergy Organization critically reviewed the existing literature and prepared this summary of recommendations for best AIT practice. The authors contributed equally and reached consensus on the statements presented herein.

Mechanisms of allergen-specific immunotherapy and immune tolerance to allergens

Substantial progress in understanding mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumors, organ transplantation and chronic infections has led to a variety of targeted therapeutic approaches. Allergen-specific immunotherapy (AIT) has been used for 100 years as a desensitizing therapy for allergic diseases and represents the potentially curative and specific way of treatment. The mechanisms by which allergen-AIT has its mechanisms of action include the very early desensitization effects, modulation of T- and B-cell responses and related antibody isotypes as well as inhibition of migration of eosinophils, basophils and mast cells to tissues and release of their mediators. Regulatory T cells (Treg) have been identified as key regulators of immunological processes in peripheral tolerance to allergens. Skewing of allergen-specific effector T cells to a regulatory phenotype appears as a key event in the development of healthy immune response to allergens and successful outcome in AIT. Naturally occurring FoxP3⁺ CD4⁺CD25⁺ Treg cells and inducible type 1 Treg (Tr1) cells contribute to the control of allergen-specific immune responses in several major ways, which can be summarized as suppression of dendritic cells that support the generation of effector T cells; suppression of effector Th1, Th2 and Th17 cells; suppression of allergen-specific IgE, and induction of IgG4; suppression of mast cells, basophils and eosinophils and suppression of effector T cell migration to tissues. New strategies for immune intervention will likely include targeting of the molecular mechanisms of allergen tolerance and reciprocal regulation of effector and regulatory T cell subsets.