1. Administration of a bacterial lysate to the airway compartment is sufficient to inhibit allergen-induced lung eosinophilia in germ-free mice.
- Author
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Michael AN, Pivniouk O, Ezeh PC, Banskar S, Hahn S, DeVries A, O'Connell K, Pivniouk V, and Vercelli D
- Subjects
- Animals, Mice, Asthma immunology, Pulmonary Eosinophilia immunology, Pulmonary Eosinophilia etiology, Pulmonary Eosinophilia pathology, Ovalbumin immunology, Female, Bronchoalveolar Lavage Fluid immunology, Lung pathology, Lung immunology, Lung microbiology, Mice, Inbred BALB C, Cell Extracts pharmacology, Disease Models, Animal, Bacterial Lysates, Allergens immunology, Germ-Free Life
- Abstract
The nexus between eosinophils and microbes is attracting increasing attention. We previously showed that airway administration of sterile microbial products contained in dust collected from traditional dairy farms virtually abrogated bronchoalveolar lavage (BAL) eosinophilia and other cardinal asthma phenotypes in allergen-sensitized specific pathogen-free (SPF) mice. Interestingly, comparable inhibition of allergen-induced BAL eosinophilia and promotion of airway barrier integrity were found upon administration of a sterile, pharmacological-grade bacterial lysate, OM-85, to the airway compartment of allergen-sensitized SPF mice. Here, we asked whether intrinsic properties of airway-delivered microbial products were sufficient to inhibit allergic lung inflammation or whether these effects were mediated by reprogramming of the host microbiota. We compared germ-free (GF) mice and offspring of GF mice associated with healthy mouse gut microbiota and maintained under SPF conditions for multiple generations (Ex-GF mice). These mice were treated intranasally with OM-85 and evaluated in the ovalbumin and Alternaria models of allergic asthma focusing primarily on BAL eosinophilia. Levels of allergen-induced BAL eosinophilia were comparable in GF and conventionalized Ex-GF mice. Airway administration of the OM-85 bacterial lysate was sufficient to inhibit allergen-induced lung eosinophilia in both Ex-GF and GF mice, suggesting that host microbiota are not required for the protective effects of bacterial products in these models and local airway exposure to microbial products is an effective source of protection. OM-85-dependent inhibition of BAL eosinophilia in GF mice was accompanied by suppression of lung type 2 cytokines and eosinophil-attracting chemokines, suggesting that OM-85 may work at least by decreasing eosinophil lung recruitment., Competing Interests: Conflict of interest statement. D.V. and V.P. are inventors in PCT/EP2019/074562 (“Method of Treating and/or Preventing Asthma, Asthma Exacerbations, Allergic Asthma and/or Associated Conditions with Microbiota Related to Respiratory Disorders”). The rest of the authors have no relevant conflicts of interest., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for Leukocyte Biology.)
- Published
- 2024
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