Role of immune-inflammatory biomarkers and their derived ratio in predicting COVID-19 severity and mortality

The pathogenesis of the coronavirus disease 2019 (COVID-19) involves a complex group of cytokines and is significantly influenced by genetic and epigenetic factors. The current study aims to assess the association of COVID-19 severity and mortality with the relative expression of MicroRNA-155 (miR-155) and its association with serum levels of interleukin (IL)-6, IL-10, and their derived ratio. This pilot case-control study included 75 COVID-19 patients and 25 healthy controls. Serum levels of cytokines were analyzed by enzyme-linked immunosorbent assay (ELISA), and assessment of miR-155 relative expression level was done using quantitative real-time PCR in all participants. We found that IL-6, IL-10, IL-6/IL-10 ratio, and miR-155 expression levels were significantly higher in COVID-19 patients than in healthy controls (p-values < 0.001). The expression level of miR-155 showed significant differences between all severity categories of COVID-19, reaching its highest levels in the severe group. It was also significantly higher in ICU-admitted patients (p-value < 0.001) and those who died during their hospital stay (p-value = 0.001). It showed a significant negative correlation with serum IL-10 (r=-0.249, p-value = 0.031) and a significant positive correlation with IL-6/IL-10 ratio (r = 0.234, p-value = 0.043). It was also the only independent risk factor for COVID-19 severity by regression analysis and the best predictor for COVID-19 severity by ROC curve analysis. This study reported elevation of cytokines and miR-155 expression in COVID-19 patients. The level of miR-155 expression was associated with COVID-19 severity, mortality, and ICU admission, indicating its potential utility as a biomarker for monitoring the progression of COVID-19 and guiding patient follow-up.