Mechanisms and biomarkers of successful allergen-specific immunotherapy

Allergen-specific B cell responses in oral immunotherapy-induced desensitization, remission, and natural outgrowth in cow's milk allergy

BACKGROUND

Antigen-specific memory B cells play a key role in the induction of desensitization and remission to food allergens in oral immunotherapy and in the development of natural tolerance (NT). Here, we characterized milk allergen Bos d 9-specific B cells in oral allergen-specific immunotherapy (OIT) and in children spontaneously outgrowing cow's milk allergy (CMA) due to NT.

METHODS

Samples from children with CMA who received oral OIT (before, during, and after), children who naturally outgrew CMA (NT), and healthy individuals were received from Stanford biobank. Bos d 9-specific B cells were isolated by flow cytometry and RNA-sequencing was performed. Protein profile of Bos d 9-specific B cells was analyzed by proximity extension assay.

RESULTS

Increased frequencies of circulating milk allergen Bos d 9-specific B cells were observed after OIT and NT. Milk-desensitized subjects showed the partial acquisition of phenotypic features of remission, suggesting that desensitization is an earlier stage of remission. Within these most significantly expressed genes, IL10RA and TGFB3 were highly expressed in desensitized OIT patients. In both the remission and desensitized groups, B cell activation-, Breg cells-, BCR-signaling-, and differentiation-related genes were upregulated. In NT, pathways associated with innate immunity characteristics, development of marginal zone B cells, and a more established suppressor function of B cells prevail that may play a role in long-term tolerance. The analyses of immunoglobulin heavy chain genes in specific B cells demonstrated that IgG2 in desensitization, IgG1, IgA1, IgA2, IgG4, and IgD in remission, and IgD in NT were predominating. Secreted proteins from allergen-specific B cells revealed higher levels of regulatory cytokines, IL-10, and TGF-β after OIT and NT.

CONCLUSION

Allergen-specific B cells are essential elements in regulating food allergy towards remission in OIT-received and naturally resolved individuals.

Subcutaneous immunotherapy for bee venom allergy induces epitope spreading and immunophenotypic changes in allergen-specific memory B cells

BACKGROUND

Allergen immunotherapy (AIT) is the only disease-modifying treatment for allergic disorders. We have recently discovered that allergen-specific memory B cells (Bmem) are phenotypically altered after 4 months of sublingual AIT for ryegrass pollen allergy. Whether these effects are shared with subcutaneous allergen immunotherapy (SCIT) and affect the epitope specificity of Bmem remain unknown.

OBJECTIVE

The study aimed to evaluate the phenotype and antigen receptor sequences of Bmem specific to the major bee venom (BV) allergen Api m 1 before and after ultra-rush SCIT for BV allergy.

METHODS

Recombinant Api m 1 protein tetramers were generated to evaluate basophil activation in a cohort of individuals with BV allergy before and after BV SCIT. Comprehensive flow cytometry was performed to evaluate and purify Api m 1-specific Bmem. Immunoglobulin genes from single Api m 1-specific Bmem were sequenced and structurally modeled onto Api m 1.

RESULTS

SCIT promoted class switching of Api m 1-specific Bmem to IgG2 and IgG4 with increased expression of CD23 and CD29. Furthermore, modeling of Api m 1-specific immunoglobulin from Bmem identified a suite of possible new and diverse allergen epitopes on Api m 1 and highlighted epitopes that may preferentially be bound by immunoglobulin after SCIT.

CONCLUSIONS

AIT induces shifting of epitope specificity and phenotypic changes in allergen-specific Bmem.

Allergen immunotherapy in asthma

Allergen immunotherapy (AIT), including SCIT and SLIT, is a treatment that involves the administration of allergens to which patients with allergic diseases have been sensitized. HDM-SCIT for asthma is indicated in cases of HDM-sensitized allergic asthma with normal lung function. HDM-SCIT improves asthma symptoms and AHR, and decreases the medication dose. Importantly, AIT can improve other allergic diseases complicated by asthma, such as allergic rhinitis, which can also contribute to the improvement of asthma symptoms. Several studies have suggested that HDM-SLIT also attenuates the risk of asthma exacerbations, and improves lung function in asthma cases with allergic rhinitis. Furthermore, AIT can modify the natural course of allergic diseases, including asthma. For example, the effects of AIT are maintained for at least several years after treatment discontinuation. AIT can prevent the onset of asthma when introduced in allergic rhinitis, and can also inhibit or reduce new allergen sensitizations. Recent data have suggested that AIT may suppress non-targeted allergen-induced immune responses in addition to targeted allergen-induced responses, and suppress infections of the lower respiratory tract by enhancing IFN responses.

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.

Hot topics in allergen immunotherapy, 2023: Current status and future perspective

The importance of allergen immunotherapy (AIT) is multifaceted, encompassing both clinical and quality-of-life improvements and cost-effectiveness in the long term. Key mechanisms of allergen tolerance induced by AIT include changes in memory type allergen-specific T- and B-cell responses towards a regulatory phenotype with decreased Type 2 responses, suppression of allergen-specific IgE and increased IgG1 and IgG4, decreased mast cell and eosinophil numbers in allergic tissues and increased activation thresholds. The potential of novel patient enrolment strategies for AIT is taking into account recent advances in biomarkers discoveries, molecular allergy diagnostics and mobile health applications contributing to a personalized approach enhancement that can increase AIT efficacy and compliance. Artificial intelligence can help manage and interpret complex and heterogeneous data, including big data from omics and non-omics research, potentially predict disease subtypes, identify biomarkers and monitor patient responses to AIT. Novel AIT preparations, such as synthetic compounds, innovative carrier systems and adjuvants, are also of great promise. Advances in clinical trial models, including adaptive, complex and hybrid designs as well as real-world evidence, allow more flexibility and cost reduction. The analyses of AIT cost-effectiveness show a clear long-term advantage compared to pharmacotherapy. Important research questions, such as defining clinical endpoints, biomarkers of patient selection and efficacy, mechanisms and the modulation of the placebo effect and alternatives to conventional field trials, including allergen exposure chamber studies are still to be elucidated. This review demonstrates that AIT is still in its growth phase and shows immense development prospects.

Vitamin D3 reverses immune tolerance and enhances the cytotoxicity of effector T cells in coal pneumoconiosis

Coal worker's pneumoconiosis (CWP) is a common occupational disease that coal miners are highly susceptible due to long-term exposure to coal dust particles (CDP). CWP can induce the accumulation of immune cells surrounding the bronchioles and alveoli in the lungs, resulting in pulmonary fibrosis and compromised immune function. Using single-cell RNA sequencing (scRNA-Seq), our previous studies disclose that CDP exposure triggers heterogeneity of transcriptional profiles in mouse pneumoconiosis, while Vitamin D3 (VitD3) supplementation reduces CDP-induced cytotoxicity; however, the mechanism by which how VitD3 regulates immune status in coal pneumoconiosis remains unclear. In this study, we elucidated the heterogeneity of pulmonary lymphocytes in mice exposed to CDP and demonstrated the therapeutic efficacy of VitD3 using scRNA-Seq dataset. The validation of key lymphocyte markers and their functional molecules was performed using immunofluorescence. The results demonstrated that VitD3 increased the number of naive T cells by modulating CD4 + T cell differentiation and decreased the number of Treg cells in CDP-exposed mice, thereby enhancing the cytotoxic activity of CD8 + effector T cells. These effects markedly alleviated lung fibrosis and symptoms. Taken together, the mechanism by which VitD3 regulates the functions of lymphocytes in CWP provides a new perspective for further research on the prevention and treatment of CWP.

Advancing precision medicine in asthma: Evolution of treatment outcomes

The article discusses the historical evolution of asthma treatment and highlights recent advancements in personalized medicine, specifically the use of biologics in severe asthma therapy and its potential combination with allergen immunotherapy (AIT). One of the major breakthroughs of biologics is their potential effect on airway remodeling, a crucial aspect of asthma chronicity. The article introduces the concept of disease-modifying antiasthmatic drugs, which aim to modify the course of asthma and possibly modulate or prevent airway remodeling. Furthermore, the critical importance of patient-centered outcome measures to evaluate the efficacy and effectiveness of asthma treatments is emphasized, with the innovative concept of asthma remission introduced as a potential outcome. Recent studies suggest that AIT can be used as an additional therapy to biologic agents for the treatment of allergic asthma. The combination of these treatments has been shown to induce improved clinical outcomes. However, AIT is actually not recommended for use in patients with severe asthma, but encouraging results from studies investigating the combined use of AIT and biologics indicate a novel approach to exploring these treatment modalities. In conclusion, the introduction of biologics and AIT has changed the scenario of respiratory allergy treatment, from a "one size fits all" approach to embracing "individual treatments."

Potential Effects of AIT on Nonspecific Allergic Immune Responses or Symptoms

Allergen immunotherapy (AIT) is a treatment in which clinically corresponding allergens are administered to patients with allergic diseases, either by subcutaneous immunotherapy (SCIT) or sublingual immunotherapy (SLIT), or by oral immunotherapy (OIT) in the case of food allergy. Since etiological allergens are administered to patients, AIT is presumed to modify mainly allergen-specific immune responses. In bronchial asthma, AIT with house dust mites (HDM) alleviates clinical symptoms, suppresses airway hyperresponsiveness, and reduces medication doses of HDM-sensitive asthmatics. Moreover, AIT can suppress the symptoms of other allergic diseases associated with asthma including allergic rhinitis. However, AIT sometimes reduces allergic symptoms not induced by the responsible allergens, such as non-targeted allergens, in clinical settings. Furthermore, AIT can suppress the spread of sensitization to new allergens that are not targeted allergens by AIT, suggesting the suppression of allergic immune responses in an allergen-nonspecific manner. In this review, the nonspecific suppression of allergic immune responses by AIT is discussed. AIT has been reported to increase regulatory T cells that produce IL-10, transforming growth factor-β, and IL-35, IL-10-producing regulatory B cells, and IL-10-producing innate lymphoid cells. These cells can suppress type-2 mediated immune responses mainly through the production of anti-inflammatory cytokines or a cell-cell contact mechanism, which may be involved in the nonspecific suppression of allergic immune responses by AIT.

Allergen immunotherapy: progress and future outlook

INTRODUCTION

Allergy, the immunological hypersensitivity to innocuous environmental compounds, is a global health problem. The disease triggers, allergens, are mostly proteins contained in various natural sources such as plant pollen, animal dander, dust mites, foods, fungi and insect venoms. Allergies can manifest with a wide range of symptoms in various organs, and be anything from just tedious to life-threatening. A majority of all allergy patients are self-treated with symptom-relieving medicines, while allergen immunotherapy (AIT) is the only causative treatment option.

AREAS COVERED

This review will aim to give an overview of the state-of-the-art allergy management, including the use of new biologics and the application of biomarkers, and a special emphasis and discussion on current research trends in the field of AIT.

EXPERT OPINION

Conventional AIT has proven effective, but the years-long treatment compromises patient compliance. Moreover, AIT is typically not offered in food allergy. Hence, there is a need for new, effective and safe AIT methods. Novel routes of administration (e.g. oral and intralymphatic), hypoallergenic AIT products and more effective adjuvants holds great promise. Most recently, the development of allergen-specific monoclonal antibodies for passive immunotherapy may also allow treatment of patients currently not treated or treatable.