The impact of COVID-19 infection on eosinophil dynamics

<bold>Background:</bold> Recent studies report significantly lower leukocyte counts, particularly eosinophils, during COVID-19 infection. We hypothesized that eosinophils migrate from blood to the airway tissue in response to chemoattractants expressed by airway epithelials cells during the viral invasion, where they release their granule proteins. <bold>Methods:</bold> Blood samples were obtained from 65 COVID-ve and 84 COVID+ve patients. CBC results were extracted from medical records upon admission (day 0), during hospitalization (day 10) and at follow up (3 months). Eosinophil granule proteins were quantified from blood sampled during hospitalization using the Luminex assay. <bold>Results:</bold> Eosinophil counts were consistently lower in COVID +ve patients across all three time points (p < 0.01), with a slower rate of recovery compared to COVID -ve patients. Levels of all eosinophil granule proteins were significantly lower in COVID +ve compared to COVID -ve patients (p < 0.05). <bold>Conclusion:</bold> Eosinophil levels and their associated degranulation products were both consistently lower in patients with COVID-19, suggesting these cells were not accumulating and degranulating in the infected airway tissue. The slow recovery of eosinophil in these patients during the follow-up visit suggests a potential role of the viral infection in depleting these immune cells from the bloodstream. The underlying mechanisms and implications for COVID-19 pathogenesis requires further elucidation. <fig><object-id>erj;64/suppl_68/PA1510/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>