Fate, It’s in Your Genes
Written by Claire Fargeix
Edited by Priya Ram
May 2, 2021
Edited by Priya Ram
May 2, 2021
Why are some people more affected than others by infectious diseases? Why do some have minor symptoms while others never recover? These are questions that investigators Jean-Laurent Casanova and Laurent Abel seek to answer in their article, “The human genetic determinism of life-threatening infectious diseases: genetic heterogeneity and physiological homogeneity?”
It has been known for a long time that some differences in the response to infectious diseases are due to variability in virulence, or the ability of the germ to cause disease in the host. We can see this in the difference between reactions to the common cold versus something much more deadly such as Ebola or COVID-19. This is due to the virulence of the virus or bacteria responsible for the infection. The virulence can also change seasonally, with the flu being a good example of this.
While there has been some investigation into why some people are more susceptible to infection, this research has been more focused on patients with previous infections or those under immunosuppressive treatments. HIV, for example, is a virus that weakens the immune system of the host, making future infections significantly more dangerous. These studies are important, but now scientists are starting to focus more on the role of genetics in how well a person fights off infection, or does not.
The answer to this question is never simple. Each person is different, and more specifically, each cell is unique and will respond as such. Microbes are also extremely diverse—even within species—and their proclivity for mutations further solidifies their differences. This means that each interaction between a human and a microbe will be different, and each will be fluid.
Even with these challenges, progress is being made. New genetic sequencing technologies that allow us to directly read our genetic code are opening opportunities for studies of human genes. Scientists have uncovered genes responsible for resistance to the microbes that cause malaria and HIV, ones correlated with successfully removing the hepatitis C virus, and one that confers susceptibility to tuberculosis. Given the specificities of each microbe, it comes as a surprise that many of these diseases are impacted by singular genes.
This research is incredibly important for the future of human health. Identifying genes that make people susceptible to disease will allow for discerning and notifying people who are more at risk. It will also better inform preventative treatments for these individuals. Above this, this research will also allow scientists to better understand the biological mechanism of infection and disease. This knowledge can also be critical in vaccine development because knowing genetic predisposition or resistance will allow scientists to know who requires the vaccine and who is at a lower priority. It could also remove confounding factors from vaccine trials, as those with resistant genes would bias the results. This research is particularly relevant because of the current COVID-19 pandemic, which we have seen has vastly different effects on different people, but the explanation is unclear.
References
Casanova, J. L., & Abel, L. (2020). The human genetic determinism of life-threatening infectious diseases: genetic heterogeneity and physiological homogeneity?. Human genetics, 139(6-7), 681–694. https://doi.org/10.1007/s00439-020-02184-w