D21-12 Single Cell Analysis of Circulating Immune Cells and Airway Eosinophil Immunophenotypes in Adults With Severe Asthma Receiving Biologic Therapy

Abstract Rationale Approximately 5-10% of patients with asthma exhibit severe disease that remains uncontrolled despite inhaled corticosteroids. In this subset, biologic treatments significantly improve asthma control, reducing exacerbation frequency and need for oral corticosteroids. However, our current understanding of the immune mechanisms underlying clinical response to biologics is incomplete, and as a result, currently-available biomarkers for guiding biologic selection are imprecise. To address this gap, we performed an in-depth analysis of blood and sputum cells from biologic naïve and biologic-treated adults with severe asthma using mass cytometry (CyTOF) to clarify how biologics alter the immune cell repertoire in adults with asthma. Methods CyTOF was performed on sputum or blood collected from adults with severe asthma as part of the DILIGENT Study. Expression of 40 surface and intracellular markers was measured and manual gating of sputum and blood cells was performed using a standardized strategy based on surface lineage markers. Relative abundance of cell populations in blood or sputum (proportion of CD45+ cells), and median expression of surface and intracellular markers were compared between biologic-naïve and biologic-treated individuals (tezepelumab (n = 11), dupilumab (n = 6), benralizumab (n = 2), mepolizumab (n = 1), and omalizumab (n = 1)). Biologic naïve participants subsequently started biologic treatment (tezepelumab (n = 7), dupilumab (n = 7), benralizumab (n = 1), mepolizumab (n = 9)), and will undergo repeat sample collection on treatment for paired future analyses. Results 50 participants were enrolled in the study, including 28 biologic-naïve and 22 biologic-treated participants. A total of 21 blood samples (11 biologic-naïve, 10 biologic-treated) and 29 sputum samples (18 biologic-naïve, 11 biologic-treated) were analyzed. Biologic-treated participants exhibited a significantly lower proportion of circulating CD4+ T cells and B cells (7.2% vs 14.5%, p = 0.006; 7.5% vs 14.2%, p = 0.01, respectively), a higher proportion of circulating monocytes (15.8% vs 6.6%, p = 0.0003), and a lower proportion of sputum CD8+ T cells (10.7% vs 17.6%, p = 0.04), as compared to biologic-naïve participants. Among biologic-treated individuals, both blood and sputum eosinophils exhibited significantly lower median expression of CD62L compared to biologic-naïve counterparts (10.1 vs 18, p = 0.01, and 7.4 vs 13, p = 0.04). Conclusions Biologic treatment in adults with severe asthma is associated with an immunologic shift from lymphocyte predominant to monocyte predominant circulating immune cells. Furthermore, biologic treatment is associated with reductions in CD62L expression in circulating and airway eosinophils. This may correspond to a broader immunophenotypic shift in eosinophil subpopulations, which will be the focus of forthcoming analyses. Taken together these findings indicate potential mechanistic immune effects of biologic therapies beyond their targeted effects. This abstract is funded by: GSK, NIH