Abstract
The COVID-19 pandemic caused by SARS-CoV-2 virus infection is resulting in enormous loss of lives and devastating the global economy. Elderly populations and those with co-morbidities are often unable to clear the infection. With several hundred thousand people dead worldwide and many more infected, it is essential to understand the immunological response that results in beneficial or detrimental disease outcomes in this infection. Natural Killer (NK) cells from the innate immune system are early cytotoxic responders that can eradicate virus-infected cells and, therefore, may help control the infection. Besides, NK cells are not only responsible for target lysis but are also immunomodulators that produce pro-inflammatory or anti-inflammatory cytokines such as IFN-γ or IL-10, respectively. Notably, COVID-19 patients consistently experience a loss in total NK cell counts with increased expression of the NKG2A receptors, and such phenotypes are highly correlated to the severity of the disease. Several clinical trials have been initiated to perfuse NK cells to COVID-19 patients. Since numerous reports consistently indicate that COVID-19 patients develop a 'cytokine storm' with increased levels of multiple pro-inflammatory cytokines, trials employing NK cells holding the pro-inflammatory property would be not ideal. Here, we contemplate the impact of NK cell loss on NK cell immunity and cytokine storm in SARS-CoV-2 infection, and propose adequate NK cell therapies for COVID-19 patients.
Highlights
The spread of the coronavirus disease 2019 (COVID-19) pandemic has led to disastrous consequences, impacting social, economic, and medical systems, spanning both developed and developing countries [1]
The unprecedented impact of COVID-19 on social, economic, and medical systems urgently requires a deeper understanding of the immune responses associated with Severe Acute Respiratory Syndrome (SARS)-CoV-2 infection, to generate therapeutic responses
These include the hyperinflammatory response and cytokine storm associated with the disease as well as lower counts of particular immune cells such as Natural Killer (NK) cells
Summary
The spread of the coronavirus disease 2019 (COVID-19) pandemic has led to disastrous consequences, impacting social, economic, and medical systems, spanning both developed and developing countries [1]. While immunological characteristics of COVID-19 continue to be discovered with ongoing research, the findings surrounding a cytokine storm as well as lymphopenia in patients with SARS-CoV-2, have been consistently reported in most studies [4, 11, 18,19,20]. In a murine model of SARS-CoV-1 infection, increased production of chemokines was correlated with increased migration of various innate immune cells, including NK cells into the lungs [45].
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