Why do bats host many viruses without developing symptoms?

Bats carry a multitude of viruses, pathogenic to most mammals, without developing symptoms. How did animal immunity evolve to defend against it? This is the question answered by scientists, mainly from the CNRS, the University Claude Bernard Lyon 1 and ENS Lyon, in a new publication to be published on November 24 in The progress of science. The answer lies, among other things, in the number of copies of the PKR gene, which participates in the immune response against viruses. While most mammals have only one copy of this gene, some bats have several. So many copies that have allowed the animal to diversify its antiviral repertoire, and therefore to face a diversity of viruses. This characteristic was made possible thanks to the duplications of the PKR gene, and to the “positive natural selection” of the latter, during the evolution of the animal. To reach this conclusion, the scientists took an interdisciplinary approach, integrating data from the field, genetics, ecoepidemiology, molecular and cell biology, and virology. They thus traced the evolutionary history of the PKR gene in different bat species, and analyzed, at the molecular level, the adaptations acquired as a result of past epidemics encountered by bats. This work notably contributes to a better understanding of virus transmission between host species.