Asthma Phenotypes and the Microbiome

Abstract

Asthma is characterised by episodic bronchospasm, airway hyperreactivity, and airway inflammation. Current treatment is aimed at reversing bronchospasm with bronchodilators and decreasing airway inflammation with corticosteroids. Asthma patients as a collective group, however, have variable responses to treatment, and our understanding and view of asthma as a single pathologic process has evolved substantially. We now recognise that asthma is a heterogeneous disease with many phenotypes, as reflected by differences in natural history, complexity, severity, and responses to treatment. The underlying aetiologies for many phenotypes are poorly understood and likely multifactorial. Recent evidence increasingly supports an important role for microbial exposures and our microbiota as factors mediating asthma pathogenesis. However, given the phenotypic heterogeneity of asthma, we further propose that microbiota may play an additional role in shaping asthma phenotype. Beginning with a brief overview of concepts of asthma phenotypes and endotypes, the intent of this article is to summarise current knowledge of the microbiome in asthma, highlighting recent studies that have examined relationships between microbiota and phenotypic features of asthma. We conclude with a discussion of future research directions, considering important issues and challenges in this area of investigation.

Keywords

• asthma
• endotype
• type 2 inflammation
• microbiota
• 16s rrna
• metagenomics