New research suggests that recovering from COVID-19 could help protect against severe cases of the flu by strengthening the immune system’s memory.
Scientists from Rockefeller University and Weill Cornell Medicine found that mice previously infected with SARS-CoV-2 (the virus causing COVID-19) were better able to fight off the flu later.
This protection came from an unexpected source in the immune system: macrophages, which are among the body’s first responders to infections.
The study, published in the journal Immunity, offers exciting insights into how the immune system builds memory to fight not just one virus, but potentially several.
This discovery may one day lead to therapies that boost our overall immunity against multiple viruses.
Our immune system has two main lines of defense: the innate immune system and the adaptive immune system. The innate immune system, which includes macrophages, acts quickly and fights infections broadly.
The adaptive immune system, made up of specialized cells like T cells, targets specific pathogens and remembers them for future attacks.
Until recently, scientists believed that only the adaptive immune system could create long-term memory of infections. However, the new study shows that macrophages, part of the innate immune system, can also develop memory after an infection like COVID-19. This memory helps them respond more effectively to future infections, even by different viruses, like the flu.
The researchers began by infecting mice with COVID-19.
After the mice recovered, they were exposed to influenza A, a common flu virus. Surprisingly, the mice that had previously recovered from COVID-19 were better at fighting the flu compared to those that hadn’t been infected with COVID-19. They showed fewer symptoms and had lower death rates.
The researchers discovered that this protection came from changes in the macrophages in the mice’s lungs. After the mice recovered from COVID-19, their macrophages underwent “epigenetic reprogramming.” This means that the genes responsible for fighting viruses became more accessible and ready to act when needed. These changes allowed the macrophages to respond faster and more efficiently to the flu.
Interestingly, this immune memory wasn’t limited to mice. When the scientists looked at samples from people who had recovered from mild cases of COVID-19, they found similar changes in their immune cells, suggesting that humans may also experience this broad immune memory.
What’s remarkable about this study is that the immune memory in macrophages wasn’t specific to COVID-19.
Instead, it recognized common patterns found in many viruses. This explains why the mice were better at fighting off the flu, even though it’s a completely different virus. When the researchers exposed the mice to a synthetic mimic of an RNA virus, they observed the same memory response.
The study also showed that these memory-enhanced macrophages outperformed adaptive immune cells like T cells in fighting the flu.
To further test this, the researchers transferred macrophages from COVID-recovered mice to healthy mice.
When these healthy mice were later exposed to the flu, they fared much better than those without the memory-boosted macrophages.
The findings from this study open up exciting possibilities for future therapies. If scientists can figure out exactly how this immune memory works, they may be able to develop treatments that boost our immune defenses against multiple viruses.
This could be particularly useful in preparing for future pandemics, where having a therapy that boosts general antiviral immunity could buy time while specific vaccines or treatments are developed.
“One day, we may be able to use this knowledge to develop therapies that provide broad protection against several viruses,” said Dr. Charles Rice, one of the study’s authors. While more research is needed, this discovery could eventually lead to treatments that help people stay protected against different viral infections for months at a time.
In the future, this approach could play a key role in preventing serious viral outbreaks and improving overall pandemic preparedness.
If you care about COVID, please read studies about vitamin D deficiency linked to severe COVID-19, death, and how diets could help manage post-COVID syndrome.
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