US virologist decodes how COVID-19 virus attacks our immune system

SARS-CoV-2, the virus that causes COVID-19, rewires the alarm system that cells use to warn others about infection, say US researchers.

The novel coronavirus that causes COVID-19 can wreak havoc on the immune system, leaving the patient unable to fight off the infection. Scientists across the globe are trying to understand how the SARS-CoV-2 attacks the immune cells. A US virologist has finally managed to decode its destructive path.

Virologist Benjamin tenOever studied the nature of the novel coronavirus in an isolated laboratory at the Icahn School of Medicine at Mount Sinai in East Harlem. He claimed that the COVID-19 attack the immune system, wreaking havoc like no other virus he's studied before.

Every cell in our body shares the same DNA and single-strand RNA, which acts like software, programming the cell to make proteins.

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tenOever's team found that SARS-CoV-2 was uncannily good at disrupting this cellular programming. While a typical virus replaces less than one per cent of the software in the cells it infects, the novel coronavirus replaces about 60 per cent of the RNA in an infected cell.

"This is the highest I've ever seen. Polio comes close," The New Yorker quoted tenOever as saying.

SARS-CoV-2is more dangerous than other viruses

According to tenOever, SARS-CoV-2 rewires the alarm system that cells use to warn others about infection.

Normally during immune response, a cell sends out two kinds of signals: one transmitted through molecules called interferons and other carried by molecules called cytokines. While the first signal alerts the neighboring cells to defend themselves against viral spread, the second signal summons the white blood cells, which don't just eat invaders and infected cells, but also gather up their dismembered protein parts. These fragments are used to create virus-specific antibodies.

Usually, most of the viruses known to infect humans shut down both these signalling programs, but SARS-CoV-2 inhibits only the interferon response, said tenOever.

tenOever and team maintained that that it's this imbalanced immune response causes the potentially deadly blood clots, strange swelling in children, and ultra-inflammatory "cytokine storms"" that health experts have reported in COVID-19 patients. The results of their study were published in the biweekly journal Cell.

In subsequent studies, tenOever and his team also found the immune systems in older victims were less adaptive, which make them more prone to the destruction caused by the virus.

How the COVID-19 infection begins

SARS-CoV-2 first enters through the nose and throat when someone inhales virus-laden air droplets expelled by an infected person. The cells in the lining of the nose are rich in angiotensin-converting enzyme 2 (ACE2) that the virus requires to enter a cell. ACE2 is present throughout the body.

Once inside a cell, the virus hijacks the cell's machinery and make myriad copies of itself which then invade new cells. An infected person may show no symptoms or may develop a fever, dry cough, sore throat, loss of smell and taste, or head and body aches during the first week or so. But the patient may shed copious amounts of the virus during this time.

If the immune system doesn't destroy SARS-CoV-2 during this initial phase, it can reach the windpipe to attack the lungs, where it can turn deadly. The virus is also known to affect other key organs like kidneys, heart and brain.

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