Genetic variation that protected against Black Death still helps protect against infection but increases autoimmune disease

illustration depicting black plague victims

Illustration depicting victims of the black plague

Press release issued: 7 March 2023

The same genetics that helped some of our ancestors fight the plague is still likely to be at work in our bodies today, potentially providing some of the population with extra protection against respiratory diseases such as COVID-19, according to research led by scientists at University of Bristol. However, there is a trade-off, where this same variation is also linked to increased autoimmune diseases such as rheumatoid arthritis and inflammatory bowel disease.

Previous studies have revealed that survivors of the Black Death, the devastating bubonic plague pandemic in the Middle Ages were more likely to carry certain variants ("alleles") in a gene called ERAP2 than those who didn't survive.

In new research published in The American Journal of Human Genetics today [7 March], Dr Fergus Hamilton and co-authors from the University's MRC Integrative Epidemiology Unit (MRC IEU), in collaboration with colleagues at the universities of Edinburgh, Oxford, Cardiff and Imperial College London, reveal that the same variants are present in humans today and providing similar protection against not only bubonic plagues but also other infections including pneumonia and COVID-19. However, this is a situation of balance, and the same genetic makeup is likely to be linked with increases in various autoimmune diseases.

"This gene essentially chops up proteins for the immune system," explained lead author Dr Hamilton, Wellcome GW4 Clinical Doctoral Fellow at the MRC IEU and North Bristol NHS Trust. "Although we don't know the exact mechanism influencing disease risk, carriers of alleles that provide more protection against respiratory disease seem to have an increased risk of autoimmune disease. It is potentially a great example of a phenomenon termed 'balancing selection' - where the same allele has different effect on different diseases."

Dr Hamilton and colleagues looked at infection, autoimmune disease, and parental longevity across participants in three large contemporary genetic studies (UK Biobank, FinnGen, and GenOMICC). They used an analytical technique known as Mendelian Randomization to find associations between variation in the ERAP2 gene and risk of autoimmune disease and infection.

Their findings point to antagonistic effects across these two groups of diseases driven by pressures likely to be more or less present in different human eras.

Nicholas Timpson, Professor of Genetic Epidemiology at the MRC IEU and co-author, added: "This is a theoretical story of balance - relating to historical and contemporary disease profiles - which reflects our past and is rarely seen in real human examples."

Identifying links between genetics and susceptibility to disease can pave the way for potential treatments. However, it also highlights potential challenges; therapeutics to target ERAP2 are currently being developed to target Crohn’s disease and cancer so it is important to consider potential effects on the risk of infection from these agents.

Paper

'Variation in ERAP2 has opposing effects on severe respiratory infection and autoimmune disease' by Fergus Hamilton, George Davey Smith, Nicholas J Timpson, et al. in The American Journal of Human Genetics [open access]

Further information

About the MRC IEU
The MRC Integrative Epidemiology Unit (IEU) at the University of Bristol conducts some of the UK's most advanced population health science research. It uses genetics, population data and experimental interventions to look for the underlying causes of chronic disease. The unit exploits the latest advances in genetic and epigenetic technologies. They develop new analytic methods to improve our understanding of how our family background behaviours and genes interact to influence health outcomes.

About Mendelian Randomization
Information on Mendelian Randomization: a method of using variation in genes of known function between people to examine the causal effect of a modifiable exposure (i.e., diet) on disease (i.e. cancer) in observational studies. The use of genetics reduces any potential measurement or human, error associated with questionnaires and participant recall which are often used to record lifestyle factors such as level of physical activity. University of Bristol researchers have published guides in the BMJ and Nature Reviews Methods, contributed to bmj and freakonomics podcasts, and produced a two-minute video primer.