THE Black Death epidemic, which caused millions of deaths in the mid-14th century, is believed to have resulted in a genetic mutation that helped survivors fight off this bacterial disease. According to a British study, this genetic variation is still present in some people today, and it could give them extra protection against Covid-19.

A recent British study, conducted by researchers from the UK's University of Bristol, in collaboration with colleagues at the universities of Edinburgh, Oxford, Cardiff and Imperial College London, has revealed that the modification of the ERAP 2 gene, which occurred in the Middle Ages in response to the Black Death epidemic, is still present in the bodies of some humans.

Nearly 700 years later, this genetic variant is believed to help carriers fight respiratory diseases such as Covid-19 and pneumonia.

On the other hand, this genetic makeup could be linked to an increase in autoimmune diseases, such as rheumatoid arthritis and inflammatory bowel disease.

To reach this conclusion, the researchers sought to assess whether variation in the ERAP2 gene was associated with severe infection, autoimmune disease and parental longevity. To do this, they used health data from thousands of UK residents from three large databases (UK Biobank, FinnGen and GenOMICC).

"This gene essentially chops up proteins for the immune system," explains the study's lead author, Dr Hamilton of the University of Bristol, in a news release.

"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."

"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," adds Nicholas Timpson, professor of genetic epidemiology and co-author of the study.

Identifying causal links between genetics and disease susceptibility may pave the way for potential treatments, the researchers say.

"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," the researchers' news release concludes.