Utility of plasma MicroRNA profiling as diagnostic biomarker in immune system activation and inflammation and early predictor of severity in patients with COVID-19.

The clinical course of Coronavirus disease 2019 (COVID-19) ranges from mild symptoms to severe complications, including respiratory failure and thromboembolic events. MicroRNAs (miRNAs) are small non-coding RNAs involved in gene regulation and may serve as biomarkers. This study aimed to identify plasma miRNAs that could serve as biomarkers for diagnosing immune system disorders and inflammation, and for prognostic stratification of patients with COVID-19. We enrolled 40 patients with suspected COVID-19 at Emergency Room admission; infection was confirmed in 30 of them. Ten non-COVID-19 patients and 10 healthy subjects were included for comparison. Among the COVID-19 group, 26 hospitalized patients were followed and stratified by disease severity (good vs. poor prognosis). Plasma miRNA profiling and single-tube validation were performed using qRT-PCR, supported by in silico miRNA-mRNA prediction and pathway enrichment analysis. Expressions of miR-199a-5p, miR-142-3p, miR-133a-3p and miR-545-3p were higher in COVID-19 patients vs. healthy subjects. Moreover, miR-133a-3p and miR-545-3p were increased in COVID-19 vs. non-COVID-19 patients. miR-423-3p, miR-106b-5p, miR-142-3p and miR-369-3p were significantly elevated in patients who later developed respiratory failure. Bioinformatics analysis suggested that these miRNAs are involved in immune and inflammation pathways. Plasma miRNA profiling may be a promising non-invasive tool for COVID-19 diagnosis and prediction of severity.