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SARS-CoV-2 infection leads to miRNA expression changes in body fluids of COVID-19 patients. This review summarizes data on miRNAs that change expression during COVID-19 and can potentially be used as biomarkers for COVID-19 and/or disease severity.

Background The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is ongoing. The pathophysiology of SARS-CoV-2 infection is beginning to be elucidated but the role of microRNAs (miRNAs), small non-coding RNAs that regulate gene expression, remains incompletely understood. They play a role in the pathophysiology of viral infections with potential use as biomarkers. The objective of this study was to identify miRNAs as biomarkers of severe COVID-19 and to analyze their role in the pathophysiology of SARS-CoV-2 infection. Methods miRNA expression was measured in nasopharyngeal swabs from 20 patients with severe COVID-19, 21 patients with non-severe COVID-19 and 20 controls. Promising miRNAs to differentiate non-severe from severe COVID-19 patients were identified by differential expression analysis and sparse Partial Least Squares-Discriminant Analysis (sPLS-DA). ROC analysis, target prediction, GO enrichment and pathway analysis were used to analyze the role and the pertinence of these miRNAs in severe COVID-19. Results The number of expressed miRNAs was lower in severe COVID-19 patients compared to non-severe COVID-19 patients and controls. Among the differentially expressed miRNAs between severe COVID-19 and controls, 5 miRNAs were also differentially expressed between severe and non-severe COVID-19. sPLS-DA analysis highlighted 8 miRNAs, that allowed to discriminate the severe and non-severe COVID-19 cases. Target and functional analysis revealed enrichment for genes involved in viral infections and the cellular response to infection as well as one miRNA, hsa-miR-15b-5p, that targeted the SARS-CoV-2 RNA. The comparison of results of differential expression analysis and discriminant analysis revealed three miRNAs, namely hsa-miR-125a-5p, hsa-miR-491-5p and hsa-miR-200b-3p. These discriminated severe from non-severe cases with areas under the curve ranging from 0.76 to 0.80. Conclusions Our analysis of miRNA expression in nasopharyngeal swabs revealed several miRNAs of interest to discriminate severe and non-severe COVID-19. These miRNAs represent promising biomarkers and possibly targets for antiviral or anti-inflammatory treatment strategies.