Epidemic How leprosy changed the genome of all Europeans

Old genetic material provides new insights into inflammatory diseases

In medieval Europe, leprosy was widespread until the 16th century and caused veritable epidemics. During the 16th century, the contagious infectious disease disappeared almost entirely from Europe. At this time, there were no antibiotics used today to treat this condition. An international research group examined bones of leprosy patients from the 12th and 13th centuries in the world's first study of this kind. The findings from this work should also allow conclusions about today's inflammatory diseases.

Apparently, an adaptation in the genome of Europeans has led to the disease not spreading further. According to the scientists around Professor Ben Krause-Kyora of the Institute of Clinical Molecular Biology (IKMB) of the Christian-Albrechts-University Kiel (CAU), a particular gene made people more susceptible to leprosy. Due to the consistent isolation of the sick from the rest of the population, this gene was increasingly passed on less and finally disappeared as far as possible and with it leprosy. The research results were recently published in the renowned journal "Nature Communications".

Leprosy today

The medieval disease is far from over. According to the IKMB, more than 200,000 people worldwide are still diagnosed with this infectious disease each year. The risk areas include Brazil, India and Indonesia. Today, however, leprosy with antibiotics is well curable. The World Health Organization (WHO) reports that leprosy with a few pathogens (paucibacillary leprosy) can be cured by six months of treatment with certain antibiotics. If many pathogens are present (multibacillary leprosy), antibiotic therapy is required over a two-year period.

Genome modification by isolation

The researchers report that in the European Middle Ages victims were isolated in major outbreaks in care facilities and buried in separate cemeteries. Due to the isolation and the fact that leprosy patients could not get offspring, the patients did not pass on a certain risk factor. "The adaptation of humans to this bacterium for centuries could have led to the disease slowly disappearing," reports study leader Krause-Kyora in a press release on the study results. This suggests that leprosy and other epidemics of the past have had a lasting effect on the composition of our genome today.

Danish bones

For their analyzes, the scientists used the bones of 85 particularly severe leprosy cases from the 12th and 13th centuries, which come from Odense in Denmark. Samples of 223 medieval Danish and North German skeletons, which showed no signs of leprosy, served as a control group. These analyzes indicated that a particular gene variant (HLA-DRB1) is associated with increased susceptibility to leprosy.

Conclusions about today's medicine

According to the scientists, the HLA gene variant still causes an increased incidence of inflammatory diseases such as sarcoidosis, the chronic inflammatory bowel disease ulcerative colitis, multiple sclerosis or type 1 diabetes. Usually, antigens provide for the recognition of bacteria and trigger a targeted immune response of the body. In the case of the identified HLA variant, this task is unsuccessful, especially in the case of the leprosy bacteria. Thus, it may come to a less successful immune response.

Interactions between pathogens and humans

"Exploring historical causes of disease is crucial to understanding the interactions between pathogens and humans, and the resulting changes in our genome over time," concludes Krause-Kyora. The team is already planning new research into other diseases of the Middle Ages in different population groups in order to keep track of how the genetic makeup of Europeans has changed. (Vb)