Viability Status-Dependent Effect of Bifidobacterium longum ssp. longum CCM 7952 on Prevention of Allergic Inflammation in Mouse Model

Marcelina Joanna Pyclik,Agnieszka Razim,Petra Hermanova,Tereza Svabova,Katarzyna Pacyga,Martin Schwarzer,Sabina Górska,Dagmar Srutkova

doi:10.3389/fimmu.2021.707728

Abstract

The classical definition of probiotics states that bacteria must be alive to be beneficial for human organism. However, recent reports show that inactivated bacteria or their effector molecules can also possess such properties. In this study, we investigated the physical and immunomodulatory properties of four Bifidobacterium strains in the heat-treated (HT) and untreated (UN) forms. We showed that temperature treatment of bacteria changes their size and charge, which affects their interaction with epithelial and immune cells. Based on the in vitro assays, we observed that all tested strains reduced the level of OVA-induced IL-4, IL-5, and IL-13 in the spleen culture of OVA-sensitized mice. We selected Bifidobacterium longum ssp. longum CCM 7952 (Bl 7952) for further analysis. In vivo experiments confirmed that untreated Bl 7952 exhibited allergy-reducing properties when administered intranasally to OVA-sensitized mice, which manifested in significant suppression of airway inflammation. Untreated Bl 7952 decreased local and systemic levels of Th2 related cytokines, OVA-specific IgE antibodies and simultaneously inhibited airway eosinophilia. In contrast, heat-treated Bl 7952 was only able to reduce IL-4 levels in the lungs and eosinophils in bronchoalveolar lavage, but increased neutrophil and macrophage numbers. We demonstrated that the viability status of Bl 7952 is a prerequisite for the beneficial effects of bacteria, and that heat treatment reduces but does not completely abolish these properties. Further research on bacterial effector molecules to elucidate the beneficial effects of probiotics in the prevention of allergic diseases is warranted.

Highlights

Food and respiratory allergies have become a significant health burden in both developed and developing countries
Changes in size did not correspond with changes in bacteria zeta potential (Figure 2B) since only two strains, Bin 369 and B. adolescentis CCDM 373 (Bad 373), have significantly lower zeta potential after heat inactivation
In the current study we compared four Bifidobacterium strains in order to evaluate the impact of heat inactivation on their physical and immunomodulatory properties

Summary

Introduction

Food and respiratory allergies have become a significant health burden in both developed and developing countries. Allergies are characterized by an abnormal reaction of the body to a commonly harmless substance. Bl 7952 Prevents Allergic Inflammation is associated with Th2 polarized lymphocyte response and involves production of IL-4, IL-5, and IL-13 cytokines and allergen-specific IgE antibodies. IL-4 and IL-13 regulate many aspects of allergic response, i.e., in B cells prompt the immunoglobulin switch to IgG1 and IgE, activate and recruit eosinophils and induce mucus hypersecretion in lung tissue [3]. Nasal and lung epithelial cells are the first cells encountering allergen, such as house-dust mite faeces, fungal spores or plant pollen. Epithelial cells are able to secrete a large number of cytokines and chemokines that regulate the activation of T and/ or B lymphocytes, eosinophils, mast cells, and ILC2 cells [5, 6]

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