MicroRNA-155 is a main part of proinflammatory puzzle during severe coronavirus disease 2019 (COVID-19).

Genetic and epigenetic parameters play critical roles in determining the outcomes of the severe acute respiratory syndrome coronavirus type 19 (SARS-CoV-2) infection. MicroRNAs (miRNAs) are an important part of the epigenetic factors that regulate several functions of the immune cells and also viruses. Accordingly, the molecules can regulate expression of the immune cell proteins and virus in the host cells. Among the miRNAs, miRNA-155 (miR-155) is well-studied in patients suffering from severe coronavirus disease 2019 (COVID-19). It has been reported that the SARS-CoV-2 infected patients may be directed to induce a cytokine storm or severe proinflammatory responses. This review article discusses the pathological roles of miR-155 during COVID-19 infection.

MicroRNA-155 and 194 alter expression of Th17 and T regulatory-related transcription factors in the patients with severe coronavirus disease 2019 (COVID-19).

INTRODUCTION: It has been demonstrated that the patients with severe acute respiratory syndrome coronavirus 2 (SARS­CoV­2) suffer from severe inflammation. Due to the ethnics, the immune responses may be different. Additionally, microRNAs may alter immune responses in the patients. The current study was aimed to evaluate the expression of T helper subsets-related transcription factors, some T helper 17 (Th17) products, and two microRNAs, including miR-155 and miR-194, in the Iranian hospitalized patients. METHODS: In this study, T-box expressed in T cells (T-bet), GATA binding protein 3, The retinoid orphan receptor gamma t (RORγt), forkhead box P3 (FOXP3), interleukin (IL)-17A, IL-8, and CC ligand 20 (CCL20) mRNA levels and, miR-155 and miR-194 levels were evaluated in 70 patients suffered from severe coronavirus disease 2019 (COVID-19) and 70 healthy subjects using Real-Time qPCR technique. RESULTS: The findings showed that RORγt, and FOXP3 mRNA levels were significantly increased, while IL-17A, IL-8, and CCL20 mRNA levels were significantly decreased in the hospitalized SARS-CoV-2 infected patients. Although the levels of miR-155 and miR-194 were not different between groups, miR-194 has negative and positive correlations with RORγt and IL-17A in the Iranian healthy controls. CONCLUSION: This study reports although RORγt was up-regulated, IL-17A, IL-8, and CCL20 mRNA levels were significantly decreased in the hospitalized SARS-CoV-2 infected patients. It may be concluded that up-regulation of FOXP3, via development of T regulatory lymphocytes suppresses Th17 functions and neutralizes Th17 activities. MiR-194 may play crucial roles in regulation of RORγt and IL-17A expression in healthy people, the phenomenon that is disrupted in the severe SARS-CoV-2 infected patients.