Immunotherapy With Recombinant Alt a 1 Suppresses Allergic Asthma and Influences T Follicular Cells and Regulatory B Cells in Mice.

Juan Liu,Jia Yin

doi:10.3389/fimmu.2021.747730

Abstract

Background Alternaria is a major source of asthma-inducing allergens. Allergen-specific immunotherapy improves the progression of allergic asthma. The current treatment is based on crude Alternaria extracts. Alt a 1 is the predominant allergen in Alternaria. However, the treatment efficacy of recombinant Alt a 1 (rAlt a 1) in an asthmatic animal model and its influence on Tfh and Breg cells are unknown.ObjectiveTo explore the therapeutic treatment effects of rAlt a 1 on the progress of an asthmatic mouse model and its effect on Tfh and Breg cells.MethodsWe synthesized and purified rAlt a 1. Alternaria-sensitized and challenged mice received subcutaneous immunotherapy (SCIT) with four different rAlt a 1 dosages (5, 50, 100, and 150 µg) or PBS only. Finally, lung and airway inflammation, mouse mast cell protease 1 (MMCP-1), serum immunoglobulin responses, Tfh and Breg cell levels, and the correlation between asthmatic features (inflammation grades and IL-4 and IL-10 levels) and these two cell types were measured after Alternaria rechallenge.ResultsHigh purity and allergenic potency of rAlt a 1 protein were obtained. Following treatment with four different rAlt a 1 dosages, both lung and airway inflammation ameliorated, including lung pathology, serum MMCP-1 levels, inflammatory cell numbers, and cytokine levels in bronchoalveolar lavage fluid (BALF). Additionally, rAlt a 1-SCIT increased the expression of Alternaria-sIgG1, rAlt a 1-sIgG1, rAlt a 1-sIgG2a, and rAlt a 1-sIgG2b in serum. Moreover, the number and percentage of CXCR5+PD-1+Tfh cells were increased in the PC control, while they decreased in the rAlt a 1-SCIT groups. Meanwhile, the absolute numbers and proportions of Breg cells were evaluated after administration of rAlt a 1. A positive correlation was observed between CXCR5+PD-1+Tfh cells and inflammation grades (r = 0.50, p = 0.01), as well as a slightly strong positive relationship with IL-4 (r = 0.55, p = 0.005) and IL-10 (r = 0.58, p = 0.003) levels; Breg cells showed an opposite correlation with the grades of inflammation (r = -0.68, p = 0.0003), along with a negative correlation to IL-4 (r = -0.61, p = 0.001) and IL-10 (r = -0.53, p = 0.008) levels.ConclusionsWe verified that treatment with rAlt a 1 can alleviate asthma progression and further have a regulatory effect on Tfh and Breg cells in an Alternaria-induced asthmatic mouse model.

Highlights

Alternaria alternata is considered the most common and abundant species that causes allergic asthma, especially in children, and is associated with its severity and persistence [1, 2]
We found that Allergen-specific immunotherapy (AIT) with rAlt a 1 alleviated lung and airway immune responses and decreased the percentage of Tfh cells, whereas that of Breg cells increased after AIT, and their total contrary variations were closely related to inflammation factors
We found that rAlt a 1 could bind to IgE epitopes of samples from patients with Alternaria-allergy, but no reaction with negative serum (Figure 1B)

Summary

Introduction

Alternaria alternata is considered the most common and abundant species that causes allergic asthma, especially in children, and is associated with its severity and persistence [1, 2]. A. alternata predominates in outdoor environments, its spores are ubiquitous in the indoor atmosphere and are principally related to sensitization [5]. Alt a 1 is the major allergen produced by A. alternata and is mainly located in the spore wall [6]. Alternaria is a major source of asthma-inducing allergens. Allergen-specific immunotherapy improves the progression of allergic asthma. Alt a 1 is the predominant allergen in Alternaria. The treatment efficacy of recombinant Alt a 1 (rAlt a 1) in an asthmatic animal model and its influence on Tfh and Breg cells are unknown

Methods

Results

Conclusion