PhD Scientific Days 2023

Translational Medicine - Posters P

CD62Llow Eosinophils Correlate with Clinical Outcomes of Asthma and Chronic Rhinosinusitis and in Vivo/in Vitro Effect of Mepolizumab on Eosinophil Subpopulations

Text of the abstract

Introduction: In mice, eosinophils are distinguished in subpopulations that differ in CD62L expression on surface membrane. Even in human, two different eosinophil subphenotypes are identified in peripheral blood (PB) of Severe Asthma (SEA) patients that differ in CD62L expression level, in particular inflammatory eosinophils show a CD62Llow phenotype, while resident eosinophils a CD62Lbright phenotype, based on flow cytometric analysis.
Aims: Verify the correlation between CD62L eosinophils expression and clinical parameters of SEA patients and analyze the effect of Mepolizumab on eosinophil subpopulations in vivo and in vitro.

Methods: We recruited 51 SEA patients never exposed at biological drug and 19 patients analysed before and after treatment with Mepolizumab.
Peripheral blood (PB) cells were collected and extracted cells were labeled with fluorescent antibodies for the identification of eosinophil subpopulations through flow cytometry.
Finally, extracted eosinophils from 5 HD and 5 SEA patients were cultured in vitro with rhIL-5 (10 ng/ml), rhIL-5+Mepolizumab (1 µg/ml) and rhIL-5+mIgG1k isotype control (1 µg/ml). Expression of CD62Llow eosinophils was analyzed before and after 1 hour of culture.

Results: A significant negative correlation between the percentage of CD62Llow eosinophils and ACT and a positive correlation of these cells and ACQ5 was observed. Concerning the CRS score a positive correlation between CD62Llow cells and SNOT22 was observed. Moreover, we observed a positive correlation between CD62Llow eosinophils and the number of annual asthma exacerbations. In mepolizumab treated patients we observed a decrease of CD62Llow eosinophils percentage.
Finally, we observed an increase of CD62Llow eosinophils after IL-5 stimulation and a restoration of unstimulated conditions after Mepolizumab addition.

Conclusions: The percentage of PB CD62Llow eosinophils is correlated with asthma and CRS severity parameters. The decrease of PB eosinophils and specifically of inflammatory CD62Llow cells after Mepolizumab treatment represents a possible rationale for the efficacy of the drug in SEA patients. In vitro stimulation with rhIL-5 suggests an important role of this cytokine in eosinophil subpopulation switch. The addition of Mepolizumab shows a reduction of IL-5 effect on CD62Llow percentage, reflecting the action of the drug in vivo.

Funding: Department of Clinical and Experimental Medicine; University of Florence