Serum levels of type I interferon (IFN-I) is associated with the severity of COVID-19.

Caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, coronavirus disease 2019 (COVID-19) has threatened global public health. Immune damage mechanisms are essential guidelines for clinical treatment and immune prevention. The dysregulated type I interferon (IFN-I) responses, lymphocytopenia and hypercytokinemia during SARS-CoV-2 infection have been reported. However, whether there is a correlation between levels of IFN-I and the severity of COVID-19 has not been reported yet. To investigate the source of IFN-I and detect the exact roles of them in the pathogenesis of COVID-19. Here ELISA was used to detect serum IFN-I (IFN-α and IFN-β) for 137 cases with laboratory-confirmed COVID-19 admitted into one hospital in Wuhan from December 2019 to March 2020, and the relationships between IFN-α/β concentrations and patients' clinical parameters were conducted by statistical analysis. Both IFN-α and IFN-β concentrations dramatically increased in COVID-19 patients, especially in old patients (>80 years) and severe cases. Statistical analysis demonstrated that serum IFN-α/β concentrations were negatively correlated with the counts of total CD3T CD4 and CD8T cells, especially in critically ill cases. Moreover, serum IFN-α levels were positively correlated to IL-6 and TNF-α. Finally, immunofluorescent double staining showed that IFN-α and IFN-β are major secretions from macrophages and dendritic cells (DCs) in lymph nodes from COVID-19 autopsies. These results demonstrate that macrophages and DCs are the main origination of IFN-I, and erum levels of IFN-I are positively associated with lymphopenia and cytokine storm, suggesting that IFN-α/β deteriorated the severity of COVID-19. Anti-interferon or IFN-I signalling block drugs are needed to treat ICU patients.