The Asiatic Black Death epidemic that plagued Europe in the mid-1300s, killing 200 million people, selected who should live or die through DNA, establishing how we respond to disease today and how the immune system has continued. to evolve since then.
Researchers from McMaster University, the University of Chicago, the Pasteur Institute and other organizations have analyzed and identified the genes that protected some from the devastating Black Death pandemic that has affected nearly 700 Europe, Asia and Africa. Years ago. Their study was published on October 19 in the journal Nature.
The same genes that once conferred protection against the Black Death are now associated with increased susceptibility to autoimmune diseases such as Crohn’s and rheumatoid arthritis, the researchers report.
The team focused on a 100-year window before, during and after the Black Death, which reached London in the mid-1300s. It remains the largest human mortality event in recorded history, killing over 50% of the people in those who back then they were some of the most densely populated parts of the world.
More than 500 ancient DNA samples have been extracted and screened from the remains of individuals who had died before the plague, died of it or survived the Black Death in London, including individuals buried in the East Smithfield plague pits used to mass burials in 1348-9 . Additional samples were taken from remains buried in five other locations across Denmark.
Black plague and human adaptation
Scientists looked for signs of genetic adaptation linked to the plague, caused by the bacterium Yersinia pestis. They identified four genes that were being selected, all involved in the production of proteins that defend our systems from invading pathogens, and found that versions of those genes, called alleles, protected or made one susceptible to plague.
Individuals with two identical copies of a particular gene, known as ERAP2, survived the pandemic a much higher rates than those with the opposite set of copies, because copies “Good” enabled more efficient neutralization of Y. pestis by immune cells.
“When a pandemic of this nature occurs, killing 30 to 50 percent of the population, there is bound to be selection for protective alleles in humans, meaning people sensitive to the circulating pathogen will succumb. Even a small advantage means the difference between surviving or dying. Of course, survivors of reproductive age will pass on their genes “
explains evolutionary geneticist Hendrik Poinar, author of the Nature article, director of McMaster’s Ancient DNA Center and principal investigator with the Michael G. DeGroote Institute for Infectious Disease Research and McMaster’s Global Nexus for Pandemics & Biological Threats.
The Europeans who lived at the time of the Black Death they were initially very vulnerable because they had not had recent exposure to Yersinia pestis. As the waves of the pandemic repeated over and over in the following centuries, mortality rates have dropped.
Researchers estimate that people with the protective ERAP2 allele (the good copy of the gene, or trait), were 40 to 50 percent more likely to survive than those who didn’t.
“The selective advantage associated with the selected loci is among the strongest ever reported in humans, showing how a single pathogen can have such a strong impact on the evolution of the immune system,” says human geneticist Luis Barreiro, an author of article, and Professor of Genetic Medicine at the University of Chicago.
The team reports that over time our immune systems have evolved to respond in different ways to pathogens, to the point where what was once a protective gene against plague in the Middle Ages is now associated with increased susceptibility to autoimmune diseases. This is the balancing act upon which evolution plays with our genome.
“This highly original work was only possible through a successful collaboration between very complementary teams working on ancient DNA, human population genetics and the interaction between Yersinia pestis virulenta viva and immune cells”says Javier Pizarro-Cerda, head of the Yersinia Research Unit and director of the World Health Organization’s Collaborating Center for Plague at the Pasteur Institute.
“Understanding the dynamics that have shaped the human immune system is the key to understanding how the pandemics of the pastlike the plague, contribute to our susceptibility to disease in modern times “says Poinar.
The findings, the result of seven years of work by graduate student Jennifer Klunk, formally of McMaster’s Ancient DNA Center and postdoctoral fellow Tauras Vigylas, of the University of Chicago, allowed an unprecedented look at the immune genes of plague victims. Black.
The research was funded in part by the Social Sciences and Humanities Research Council of Canada (SSHRC), the National Institutes of Health (NIH) and the Canadian Institute for Advanced Research, under the Humans and the Microbiome program.
#Black #Death #shaped #evolution #immune #genes