SARS-Cov-2 is the virus that causes the disease COVID-19. While most patients who contract the disease experience mild symptoms, a significant percentage has severe symptoms, sometimes leading to death. In this paper, the immune response to SARS-Cov-2 infection is reviewed, highlighting differences between patients with severe disease and patients with mild disease. Findings suggest that, with severe disease, there is an exaggerated inflammatory reaction to the virus while both the humoral (B cell) and cytotoxic (NK-cell and CD8+ T cell) arms of the immune system are weak and delayed. Possible treatment options are also explored. Studies in other settings have shown that IL-15 supports the cytotoxic arm of the immune response. IL-21 has been shown to support both the cytotoxic and humoral arms of the immune response. In addition, in some settings, IL-21 has been shown to actually decrease the production of IL-6 and TNF-α, reducing the inflammatory proteins involved in the cytokine storm. In other settings, the combination of IL-15 and IL-21 has been shown to be more effective than either interleukin alone in promoting an effective immune response. So if the combination of IL-15 and IL-21 is given early in the course of the disease to patients with early predictors of severe disease, the devastating effects of the infection may be avoided. Therefore, a clinical trial of these interleukins for SARS-Cov-2 disease is warranted.

COVID-19, SARS-Cov-2, Immune cells, Interleukin-15, Interleukin-21, Immune Treatment, Severe vs. Mild COVID-19 Disease