The cytokine storm of severe influenza and development of immunomodulatory therapy

Abstract

Severe influenza remains unusual in its virulence for humans. Complications or ultimately death arising from these infections are often associated with hyperinduction of proinflammatory cytokine production, which is also known as 'cytokine storm'. For this disease, it has been proposed that immunomodulatory therapy may improve the outcome, with or without the combination of antiviral agents. Here, we review the current literature on how various effectors of the immune system initiate the cytokine storm and exacerbate pathological damage in hosts. We also review some of the current immunomodulatory strategies for the treatment of cytokine storms in severe influenza, including corticosteroids, peroxisome proliferator-activated receptor agonists, sphingosine-1-phosphate receptor 1 agonists, cyclooxygenase-2 inhibitors, antioxidants, anti-tumour-necrosis factor therapy, intravenous immunoglobulin therapy, statins, arbidol, herbs, and other potential therapeutic strategies.

Figure 1

Cytokine storm in the lung following severe influenza infection. (1) Viruses infect lung epithelial cells and alveolar macrophages to produce progeny viruses and release cytokines/chemokines (mainly contains interferons). (2) Cytokine/chemokine-activated macrophages and virally infected dendritic cells lead to a more extensive immune response and the initiation of cytokine storm. (3) Released chemokines attract more inflammatory cells to migrate from blood vessels into the site of inflammation, and these cells release additional chemokines/cytokines to amplify cytokine storm.