To find out the reason why some COVID-19 patients experience only mild symptoms while others get really severe ones and need hospitalization, a study conducted by Yale researchers used “humanized mice!”
And sure enough, they managed to gain some valuable insight, linking the body’s inflammatory response to the infection!
Furthermore, the team of researchers also confirmed that two of the most well-known therapies, monoclonal antibodies and the steroid dexamethasone, are really helpful in treating COVID infections, but in crucially different ways.
As mentioned before, the research was done on mice “engineered to possess human-like immune systems” as per the Yale report published in the journal Nature Biotechnology.
The whole research started by trying to answer the following question: “why do 80% to 90% of people infected with COVID experience only mild cases while 10% to 20% face more severe or life-threatening symptoms?”
Many other scientists have been trying to find the solution to this question but comparing the virus in humans to infected lab animals “made it difficult for scientists to identify the tipping point between mild and severe cases of COVID-19.”
This is where the use of rats with humanized immune systems came in handy.
The senior author of this paper and a Sterling Professor of Immunobiology at Yale explained that “If you infect a standard lab mouse with SARS-CoV-2 they will get infected, but not seriously ill. But our humanized mice get sick and don’t just get better. Their whole immune system is on fire.”
The research team was led by Howard Hughes Medical Institute (HHMI) Fellow, Esen Sefik, who introduced SARS-CoV-2 samples taken directly from seriously ill patients into humanized mice’s nasal passages.
The next step was just following the natural course of the disease.
They noticed that the mice had the same severe symptoms as the really ill human patients, including weight loss, lung damage, as well as a persistent and heightened inflammatory immune response that actually damages tissues!
The researchers went on to treat the lab mice with monoclonal antibodies, which tend to target the virus specifically.
What they learned was that this treatment was highly efficient when administered before the infection or very early on after.
However, it, unfortunately, did very little to treat the severe symptoms whenever administered in the later infection stages.
Furthermore, in the early stages of infection, administering the immune suppressant dexamethasone led to the mice dying due to the fact that it suppressed their initial immune response, which is really important in fighting the virus.
On the other hand, when administered during the later stages of infection, it helped clear it out by suppressing the inflammatory response that, at that point, would start to damage organs!
The conclusion was clear: “Early in the course of the disease, a really strong immune response is crucial for survival. Later in the disease, however, it can be fatal.”