Microbiosthma: a prospective study following respiratory microbiota in young children with severe preschool wheezing to better understand their respiratory future.

Preschool wheeze is a frequent infant disease, which can be severe. A continuous infection/inflammation loop at the heart of the pathophysiology is described, which could lead to a dysbiosis. In this context, the main objective of the "Microbiosthma" project is to assess whether dysbiosis of the upper and lower respiratory microbiomes could constitute a physiopathological biomarker of severe preschool wheeze in young children. This project will be divided into three parts: (i) determine the basal composition of the respiratory microbiomes (ii) monitor these microbiomes longitudinally over the course of the severe preschool wheeze, with a one-year follow-up, and (iii) assess the role of immune cell activation and inflammation in the pathogenesis of severe preschool wheeze. The "Microbiosthma" project is a bicentric, prospective study. Bronchial fibroscopy is performed on children aged < 24 months with severe preschool wheeze. One hundred infant nasopharyngeal, bronchoalveolar lavage and sputum samples will be collected over 2 years, and patients will be followed for 12 months. This collection started in September 2023. Microbiome analyses will use a metatranscriptomic approach and immunological analyses for all samples collected. For immunological analysis, key inflammatory cytokines in bronchoalveolar lavage samples will be measured. Host sequencing data obtained by NGS sequencing will be analysed for transcriptomic signatures of inflammatory profiles. The aim of the "Microbiosthma" project is to understand the respiratory microbiome of the physiopathological process involved in the development of severe preschool wheeze. This original project will therefore identify the nature of potential dysbiosis, the relationship between different respiratory microbiomes and the potential role of the immune system in this pathogenesis. The registration number is NCT06044051 (CCP Nord-Ouest, 07/11/2023).