The amount of cytokine-release defines different shades of Sars-Cov2 infection

Abstract

The recent outbreak of coronavirus disease (COVID 19), spreading from China all around the world in early 2020, has led scientists to investigate the immuno-mediated mechanisms underlying the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2) infection. Depending on the amount of cytokines released as the result of the immunological activation induced by SARS-CoV2, three major clinical phenotypes can be identified: “mild”,symbolized as a “drizzle” of cytokines, severe as a “storm”, and critical as a “hurricane”. In patients with mild symptoms, the release of pro-inflammatory cytokines is balanced to obtain a defense response against the virus which is often self-limiting and overcomes without tissue damage. In severe phenotype, resembling a “cytokine-release syndrome”, SARS-CoV2 causes the lysis of the immune-mediators leading to a cytokine storm able to induce lung epithelium damage and acute respiratory distress syndrome. In critical patients, the immune response may become uncontrolled, thus the cytokine burst resembles a form of secondary hemophagocytic lymphohistiocytosis which may result in a multi organ failure. In addition to the standard of care, an immune-modulatory therapy tailored to each one of the different phenotypes should be used in order to prevent or reduce the release of cytokines responsible for organ damage and disease progression.