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Infectious Diseases

Updated 13 May 2020

Can suppressing the immune system early in Covid-19 prevent severe symptoms?

Research shows that various immune responses in the body might cause more severe symptoms and complications – but can immune suppression help with that?

A new study from the Keck School of Medicine of USX suggests that temporarily suppressing the body’s immune system early on during Covid-19 might help a patient avoid the worst outcome.

According to their research that was published in the Journal of Medical Virology, the body’s two main lines of defence, the innate and adaptive immune responses cause the immune system to go into overdrive in some patients, which may lead to fatal consequences.

What is the difference between innate and adaptive immune response?

When the body gets threatened by an infection, there are two lines of defence. The first line of defence, the innate immune response, kicks in right after the body gets infected by pathogens like viruses or bacteria.

The innate immune response targets the specific pathogen and tries to kill it and any cells damaged by it.

The second line of defence, the adaptive immune response, only kicks in days later if there are still any signs of the virus in the body. This response uses mechanisms such as T and B cells to help fight the virus.

But why would your own immune system harm you?

Your immune system responds differently to various viruses and bacteria. In the case of flu, the infection moves swiftly and the immune system kills almost all of the targeted cells within days.

But, in the case of Covid-19, the disease progresses much more slowly. When the immune system realises there is imminent danger, the second line of defence, the adaptive reaction, may kick in long before the sick cells are killed, interfering with the innate immune response’s ability to properly attack the intruder.

"The danger is, as the infection keeps going on, it will mobilize the whole of the adaptive immune response with its multiple layers," explained Weiming Yuan, associate professor in the Department of Molecular Microbiology and Immunology at the Keck School of Medicine of USC, and co-corresponding author of the study in the press release.

"This longer duration of viral activity may lead to an overreaction of the immune system, called a cytokine storm, which kills healthy cells, causing tissue damage."

Better, then suddenly worse

This may also explain why some Covid-19 patients seem to think they are on the mend, only to feel much worse.

"Some Covid-19 patients may experience a resurgence of the disease after an apparent easing of symptoms," said Sean Du, adjunct researcher and lead author of the study. "It's possible that the combined effect of the adaptive and the innate immune responses may reduce the virus to a low level temporarily. However, if the virus is not completely cleared, and the target cells regenerate, the virus can take hold again and reach another peak."

A possible solution?

The research resulted in the possibility of treating this reaction in Covid-19 patients by trying to prevent this response from the immune system.

The team suggests proper immunosuppressant drugs early in the disease to avoid a serious onset of symptoms.

Small Chinese studies did show that immunosuppressants such as corticosteroids resulted in a more favourable outcome in patients with Covid-19.

The researchers will need to see if their data validates their current mathematical modelling, and they will have to do more pre-clinical studies first to see if this treatment is viable.

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