One of the main concerns about COVID-19 is that we don’t truly understand why some people react worse than others to infection. Otherwise healthy young people have severe reactions, and some elderly people who have predisposing conditions are bouncing back from being sick. There are loads of contributing factors that influence a person’s response to infection (to more than just the current pandemic). Genetics play a significant factor in immune system development, and genetic variation between people could explain a lot about different immune reactions.
In June 2020, researchers wanted to find out why two pairs of brothers (previously healthy) needed intensive medical care and ventilation after contracting COVID-19. The researchers found that a gene (TLR7) is a crucial part of the immune system response to COVID-19. They did this by sequencing all the genes in the brothers and then focused on the genes that are known to play a role in immunity. A lot of immune system-related genes are found on the X chromosome (biologically females have XX and males XY). The TLR7 gene is part of a family of genes that recognize bacteria and viruses that enter the body and then activate the immune system accordingly.
Therefore if the TLR7 gene is not working correctly in some people, then the immune system is not as prepared to respond to an infection. The researchers found that people born with an error in this gene did not have protection from SARS-CoV-2, and the virus was able to replicate uncontrollably. The TLR7 protein was tested in the lab and is shown that a functioning TLR7 gene responds to the SARS-CoV-2 molecules and signals to the body’s immune system to attack the virus.
This research helps us understand more of the complex interactions between our genetics and our environment. Although the TLR7 gene doesn’t explain all the variation in COVID-19 cases, it might help medical staff to treat the disease more effectively and see who is more likely to get severely sick.
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