Anti-IL-5 therapy and the airway microbiome in asthma

Introduction: The cytokine IL-5 is highly involved in eosinophilic development. IL-5 monoclonal antibodies result in downregulation of the eosinophilic inflammatory pathway and have demonstrated clinical benefit in patients with severe, eosinophilic asthma. Aims and Objectives: Our aim was to investigate if anti-IL-5 treatment induced changes in the airway microbiome in severe asthmatics. Methods: Eight well characterised severe asthmatic patients underwent bronchoscopy with bronchoalveolar lavage (BAL) pre- anti-IL-5 monoclonal antibody therapy with follow up bronchoscopy within 2 years of first starting anti-IL-5 monoclonal therapy (relizumab). Molecular analyses of BAL microbial composition by qPCR pre- and post- anti-IL-5 therapy was performed. Results: Anti-IL-5 therapy reduced BAL eosinophil counts (7.1% to 0.4%). Differences were also observed in the detection of bacterial strains after anti-IL-5 therapy. The largest increases were seen in M. pneumoniae (25% to 75%), N. meningitidis (38% to 100%) and H. influenzae (63% to 100%) in BAL by qPCR. At follow up bronchoscopy BAL monocyte cell counts positively correlated with M. pneumoniae presence (p Conclusions: Anti-IL-5 therapy modulates the composition of the lung microbiota in severe asthma.