Compromising between European and US allergen immunotherapy schools: Discussions from GUIMIT, the Mexican immunotherapy guidelines

Preventive allergen immunotherapy with inhalant allergens in children

The efficacy and safety of preventive allergen immunotherapy (pAIT) in children are currently under investigation. Here, we provide an overview of pAIT with respiratory allergens concerning the prevention of new sensitizations, allergic disease onset and progression as well as further immunomodulatory effects. Three databases were searched for clinical pAIT studies in children. Selected publications were reviewed for preventive outcomes according to prevention level (primary, secondary, and tertiary), allergen type, administration route, dose, and treatment duration. The primary prevention approach appears safe but showed no allergen-specific effect on new sensitizations. Secondary prevention seems feasible and may induce regulatory T cell-mediated immunotolerance. The number of studies at these prevention levels is limited. Tertiary prevention with grass and/or tree pollen-based pAIT has shown efficacy in preventing disease progression from allergic rhinitis/conjunctivitis to asthma. Data on tertiary pAIT with house dust mites and other allergen types are inconclusive. Subcutaneous and sublingual routes appear similarly effective, but head-to-head comparative paediatric studies are scarce. Additionally, there are fewer placebo-controlled studies. Nevertheless, immunomodulatory outcomes of pAIT are encouraging. Currently, limited but favourably suggestive evidence is available for preventing respiratory allergic diseases in children by pAIT. Primary and secondary prevention have potential and warrant further investigation through well-designed studies.

How can we improve our use of allergen immunotherapy as a treatment option for asthma and severe asthma?

INTRODUCTION

In patients suffering from allergic asthma, especially in the pediatric age-group, allergen immunotherapy (AIT) could be of benefit and has the potential of long-term disease modification.

AREAS COVERED

We reviewed the evidence for a beneficial effect of AIT in allergic asthma. A correct selection of the possible candidates for AIT is crucial. We define the comprehensive allergic asthma diagnosis: confirming asthma, confirming allergic sensitization and having symptoms on exposure to the relevant allergens.We analyze why the first trials on AIT for asthma were contradictory; we consider the results of systematic reviews and discuss the high degree of heterogeneity often found in meta-analysis. We assess recent, double-blind, placebo-controlled trials in sublingual AIT that provide robust evidence for a reduction in acute asthma exacerbations and a decrease in the use of inhaled corticosteroids. Further, we demonstrate how real-world trials and large pharmacy data-based analyses confirm these findings for SLIT and SCIT. Finally, we explore the option of AIT in severe asthma patients, once well-controlled on biologic therapy.

EXPERT OPINION

Clear indications for AIT in asthma guidelines would benefit allergic asthmatics. AIT is a therapeutic option in appropriately selected asthmatics. Three years treatment has the potential for long-term tolerance, with persisting benefits years after discontinuation.

Comparison of allergen immunotherapy practice patterns in inhalant allergies in the United States of America and Europe: Similarities and differences 2023

IgE-mediated atopic diseases such as allergic rhinitis and rhinoconjunctivitis are common chronic diseases in the western world. Allergen immunotherapy (AIT) plays a fundamental role in the treatment of allergic patients by modulating the underlying immune mechanisms. Though this treatment is integrated in practice-patterns globally, many differences are found in the application of AIT on the national or international level due to heterogeneous methods, and clinical recommendations are given in different parts of the world. This review from authors in Europe and the United States highlights differences and similarities in important aspects of AIT application in the 2 global regions. First, the regulatory situation differs regarding marketing authorization and licensing. Secondly, differences are elaborated in manufacturing practices, marketing distribution and formulations of AIT products. Thirdly, clinical administration patterns in the current guidelines show similarities in indications and contraindications of AIT, but also are divergent in some practical aspects. Informing the readership on similarities, as well as differences of standards in AIT in the United States and Europe, the authors highlight the unmet need of thorough harmonization of standards of AIT, as it is the only disease modifying treatment option available for patients with allergic rhinitis and rhinoconjunctivitis.

Allergen Release Profiles of Fast-Dissolving Freeze-Dried Orodispersible Sublingual Allergy Immunotherapy Tablets

Background

Sublingual allergy immunotherapy tablets (SLIT-tablets) provide a well-tolerated and clinically efficacious treatment for allergic disease such as allergic rhinitis and allergic asthma. In SLIT, uptake of allergen by immune-competent cells in the oral mucosa activates the immune system and leads to tolerance toward the sensitizing allergen. The ability to deliver the full allergen content into solution within the recommended sublingual holding time is therefore an essential quality of SLIT-tablets that must be supported by the tablet formulation for all relevant allergen sources. SLIT-tablets based on a fast-dissolving orodispersible freeze-dried formulation (Zydis) are currently available for 5 of the most prevalent allergens: tree (birch and related species from the birch-homologous group), grass, ragweed, Japanese cedar, and house dust mite.

Objectives

The purpose of this study was to examine the allergen release properties of three freeze-dried SLIT-tablets containing tree, ragweed, and Japanese cedar extracts, respectively. The correlation between SLIT-tablet allergen release and the level of allergen-specific T-cell activation was examined for the tree SLIT-tablet.

Methods

Allergen release kinetics and tablet disintegration times for the 3 freeze-dried SLIT-tablets were examined. For all 3 tablets, the magnitude of solubilized major allergen relative to time in solution was compared to external controls to achieve a measure of the total allergen release. Additional assessments of allergen release occurring after the initial timepoint (15 or 30 seconds in solution) were done independently of external controls by linear regression analyses. For the tree SLIT-tablet, the immunological potency of the released major allergen was assessed at each experimental timepoint by a Bet v-specific T-cell activation assay.

Results

All 3 SLIT-tablets disintegrated within 1 second after contact with assay buffer without any detectible residue. Complete release of major allergens (Bet v 1, Amb a 1, and Cry j 1, respectively) was seen at the earliest experimental time points (15 or 30 seconds). For the tree SLIT-tablet, full T-cell activation was achieved at 30 seconds (earliest experimental time point).

Conclusions

The freeze-dried SLIT-tablet formulation consistently provides rapid and complete release of allergen from a wide range of species in a standardized in vitro assay. Full release of the SLIT-tablet allergen content within the sublingual holding time is a prerequisite for maximal exposure of allergens to the sublingual mucosa immune system. The freeze-dried SLIT-tablet formulation examined here supports short sublingual holding times and furthermore offers a convenient administration form of allergy immunotherapy.

Allergens and Adjuvants in Allergen Immunotherapy for Immune Activation, Tolerance, and Resilience

Allergen immunotherapy (AIT) is the only setting in which a vaccine is applied in patients allergic exactly to the active principle in the vaccine. Therefore, AIT products need to be not only effective but also safe. In Europe, for subcutaneous AIT, this has been achieved by the allergoid strategy in which IgE epitopes are destroyed or masked. In addition, adjuvants physically precipitate the allergen at the injection site to prevent too rapid systemic distribution. The choice of adjuvant critically shapes the efficacy and type of immune response to the injected allergen. In contrast to T_H2-promoting adjuvants, others clearly counteract allergy. Marketed products in Europe are formulated with aluminum hydroxide (alum) (66.7%), microcrystalline tyrosine (16.7%), calcium phosphate (11.1%), or the T_H1 adjuvant monophosphoryl lipid A (5.6%). In contrast to the European practice, in the United States mostly nonadjuvanted extracts and no allergoids are used for subcutaneous AIT, highlighting not only a regulatory but maybe a "historic preference." Sublingual AIT in the form of drops or tablets is currently applied worldwide without adjuvants, usually with higher safety but lower patient adherence than subcutaneous AIT. This article will discuss how AIT and adjuvants modulate the immune response in the treated patient toward immune activation, modulation, or-with new developments in the pipeline-immune resilience.