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Graphical abstract
Highlights • According to WHO, COVID-19 pandemic belongs to very high-risk category. • Potentially lethal manifestations of COVID-19 are due to cytokine storm syndrome. • Cytokine storm in COVID-19 patients with co-morbidities is associated with elevated cytokine synergism. • Exacerbation of ‘cytokine storm’ in high risk patients could be responsible for the high mortality. • Antiviral state imparted by BCG vaccine confers early protection against SARS-CoV2. • Trained immunity of BCG vaccine involves the release of cytokine IL-1β, TNF-α and IL-6 from epigenetically modified monocytes.
The seventh human coronavirus SARS-CoV2 belongs to the cluster of extremely pathogenic coronaviruses like SARS-CoV and MERS-CoV, which are established to cause lower respiratory tract infection. The viral infection can be fatal as the disease advances to pneumonia followed by acute respiratory distress syndrome (ARDS). Increasingly higher cytokine concentration on account of over-stimulated immune response against the virus, or the ‘cytokine storm’, is the reason behind the manifestation of lethal clinical symptoms. In this article, we discuss the immune pathogenesis of cytokine storm and its relation with SARS-CoV2/COVID-19 risk factors. People with underlying risk factors are more susceptible to fatal complications of COVID-19 infection leading to poor clinical outcome. The increased pro-inflammatory immune status in patients with risk factors (diabetes, hypertension, cardiovascular disease, COPD) exacerbates the Cytokine-storm of COVID-19 to a Cytokine Super Cyclone. We also overviewed antiviral immune response provided by BCG vaccine involving the IL-1β, IL-6 and TNF-α secretion via ‘trained monocytes’, which confers early protection against SARS-CoV2. |
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