Heterogeneous ILC responses in severe asthma patients undergoing anti-IL5/5Ra therapy

<bold>Rationale:</bold> Innate lymphoid cells (ILCs) are a heterogeneous group of effector cells. Asthma is classically a type 2 disease, and dysregulated ILC2s are implicated in pathology. However, severe asthma (SA) is a heterogeneous disease, for which there is little known about the role of other ILC subsets. This study sought to exhaustively characterise ILCs in SA relative to healthy controls (HC), and infer the impact of anti-IL5/5Ra therapy on these populations. <bold>Methods:</bold> Patient demographics, spirometry and FeNO were prospectively collected with blood and induced sputum from HCs (n=20) and SA subjects pre and post benralizumab/mepolizumab (n=26) for ≥3 months. 21-colour full-spectrum flow cytometry was used for ILC evaluation and proteomics performed via Olink. <bold>Results:</bold> SA was associated with increased ILC progenitors (ILCPs) in the blood and sputum, as well as elevated T-bet+ ILC1s, GATA-3+ ILC2s and RORγt+ ILC3s within the airways only of SA subjects. Increased sputum ILCP, ILC1 and ILC2 populations correlated with ACQ-7 score and FEV1 % predicted. Anti-IL5/5Ra therapy did not alter ILC subset numbers in the blood or sputum, however there was a reduction in ILCs displaying type 2 features within the airways. Proteomic profiling highlighted a significant positive correlation between total ILCs within the airways of SA subjects and expression of the type 2-associated cytokines IL-5, IL-13 and IL-33, with all correlations absent following anti-IL5/5Ra therapy. <bold>Conclusion:</bold> SA subjects exhibit a multifaceted ILC subset response in their airways that correlates with type 2 cytokines and clinical prognosis. Importantly, pathogenic airways ILC2 responses are selectively dampened following anti-IL5/5Ra therapy.