Similar to any other virus, the symptoms of COVID-19 are amplified in patients who are of old age, have additional complications, or are unvaccinated. For instance, researchers found that unvaccinated individuals ages 50 and older are 12 times more likely to die from COVID-19 than individuals who are vaccinated with boosters (Hesman Saey). Additionally, cancer patients, especially those who are immunosuppressed, are at a higher risk of facing the serious impacts of COVID-19. Research suggests that baseline immunosuppression increases the risk of a cytokine storm. Cytokine storms result in extreme immune responses towards a pathogen which can result in harmful conditions for the body or in some cases death.
These factors play an important role in the severity of COVID-19, however, there are still some severe cases that are unaccounted for. Throughout the COVID-19 pandemic, one question that has perplexed many scientists is: why do certain healthy patients contract severe cases of COVID-19 while others merely experience the symptoms of the common cold? Recent research has found that genetics may be the answer. Studies have revealed that genes passed down from our ancient ancestors can both help and hurt individuals infected with COVID-19. A global study that took DNA samples from 28,000 patients infected with Covid-19 and about 600,000 healthy patients confirms this theory.
The two main genes taken into account are toll-like receptor 7 (TLR7) and TYK2. Variants in these genes are what can control the severity of a COVID-19 case. TLR7 is a gene whose protein is responsible for initiating an immune response by sending signals to other cells that a pathogen has invaded the body. If this process is not operating correctly, it is more difficult for the body to defend against a virus. So, if SARS-CoV-2 enters the body, a variation in TLR7 can cause a more severe case of COVID-19. TYK2 is responsible for producing interferons. A variation in TYK2 can cause an overproduction of interferons. When there is a virus present, such as SARS-CoV-2, the production of interferons can be helpful in the body’s defense.
The processes impacted by TRL7 and TYK2 directly relate to the body’s innate immune process. Innate immunity is the body’s first line of defense once a virus has passed through our innate immune system. The innate immune process involves mast cells which release histamines and macrophages which release cytokines. Interferons work in a similar way. All parts of innate immunity are focused on keeping the pathogen from advancing. Cell signaling is central to innate adaptive immunity, so any alterations in it would result in a less effective defense and therefore a more severe case of COVID-19.
I found this COVID-19 study to be intriguing because this past January a few members of my household were infected with COVID-19. However, only one experienced extreme symptoms. Since all were vaccinated, it may be possible that the alterations in TLR7 and TYK2 are the reason for the differences in reactions among my family.