A shift towards an immature myeloid profile in peripheral blood of critically ill COVID-19 patients

SARS-CoV-2 , the etiological agent causing COVID-19, has infected more than 8.7 million people with over 461000 deaths worldwide since its emergence in December 2019. Factors for severe disease, such as diabetes, hypertension and obesity have been identified however, the precise pathogenesis is poorly understood. In order to understand its pathophysiology and to develop effective therapeutic strategies, it is essential to define the prevailing immune cellular subsets. We performed circulating immune cells scRNAseq from five critically ill COVID-19 patients. Immature myeloid populations, such as promyelocytes-myelocytes, metamyelocytes, band neutrophils, monocytoid precursors and activated monocytes predominated. Trajectory with pseudotime analysis supported the finding of immature cell states. Gene ontology showed myeloid cell activation in immune response, DNA and RNA processing, defense response to virus and response to type 1 interferon. Lymphoid lineage was scarce. Our results uncover a transcriptomic profiles related to immature myeloid lineages and suggest the potential induction of trained immunity.