Some people get really sick from COVID-19, and others don’t. Nobody knows why.
In a new study, researchers have turned up immunological deviations and lapses that appear to spell the difference between severe and mild cases of COVID-19.
That difference may stem from how our evolutionarily ancient innate immune system responds to SARS-CoV-2, the virus that causes the disease.
Found in all creatures from fruit flies to humans, the innate immune system rapidly senses viruses and other pathogens.
As soon as it does, it launches an immediate though a somewhat indiscriminate attack on them and mobilizes more precisely targeted, but slower-to-get-moving, “sharpshooter” cells belonging to a different branch of the body’s pathogen-defense forces, the adaptive immune system.
These findings reveal how the immune system goes awry during coronavirus infections, leading to severe disease, and point to potential treatments.
The research was conducted by a team at the Stanford University of Medicine and other institutions.
In the study, the team analyzed the immune response in 76 people with COVID-19 and in 69 healthy people.
They found enhanced levels of molecules that promote inflammation in the blood of severely ill COVID-19 patients.
Three of the molecules they identified have been shown to be associated with lung inflammation in other diseases but had not been shown previously in COVID-19 infections.
These three molecules and their receptors could represent attractive therapeutic targets in combating COVID-19.
The scientists also found elevated levels of bacterial debris, such as bacterial DNA and cell-wall materials, in the blood of those COVID-19 patients with severe cases.
The more debris, the sicker the patient—and the more pro-inflammatory substances circulating in his or her blood.
The findings suggest that in cases of severe COVID-19, bacterial products ordinarily present only in places such as the gut, lungs, and throat may make their way into the bloodstream, kick-starting enhanced inflammation that is conveyed to all points via the circulatory system.
But the study also revealed that the key cells of the innate immune system in the blood of COVID-19 patients became increasingly paralyzed as the disease got worse.
Instead of being aroused by the presence of viruses or bacteria, these normally vigilant cells remained functionally sluggish.
If high blood levels of inflammation-promoting molecules set COVID-19 patients apart from those with milder cases, but blood cells are not producing these molecules, where do they come from?
The team believes they originate in tissues somewhere in the body—most likely patients’ lungs, the site of infection.
One author of the study is Bali Pulendran, Ph.D., a professor of pathology and of microbiology and immunology.
The study is published in Science.
Copyright © 2020 Knowridge Science Report. All rights reserved.
