Bats May Have Taken on Viruses To Stay in Flight

Dampening the immune response to stay up in the air may have helped bats become tolerant to viral infections.

Feb 22, 2018
Ashley Yeager

WIKIMEDIA, JAMES NILANDBats have a lot of viruses floating about in their bodies, but they don’t get sick like humans do. That could be because bats fly.

“We were interested [in] why and how bats’ immune systems could deal with so many deadly viruses,” Peng Zhou, a virologist at Wuhan Institute of Virology in China, tells The BBC.

Zhou and his colleagues reported yesterday (February 22) in Cell Host & Microbe that bats may have evolved to dampen certain immune pathways to have milder responses to viruses. The team focused on the stimulator of interferon genes, or STING, pathway, which plays a role in antiviral immunity by screening cells for free-floating DNA. In non-flying mammals, free-floating DNA is minimal, so if STING sensor molecules detect it, they send a flood of interferons to the cells.

Flying, however, takes effort and, in turn, releases a lot of free-floating DNA into bats’ cells. So to stop an immune attack at every flap of the wing, the animals’ STING sensor molecule evolved to lack a key amino acid that triggers the immune response. As a result, when viruses invade and add free-floating DNA to bats’ cells, the animal’s immune system doesn’t kick into high gear and the bats don’t get sick.

“Viral infection is the compromise that the bats have made for flight,” Kate Stacey, an immunologist at University of Queensland who was not involved in the work, tells COSMOS.

John Mackenzie of Curtin University in Perth, Western Australia, who also didn’t take part in the study, tells New Scientist that researchers need to “learn how the bats remain well and unaffected” because the viruses they carry could spark new global pandemics.

Still, some researchers have questions about the new results. Victor DeFilippis of the Oregon Health and Science University tells The BBC that it’s not clear whether scientists can “draw broad conclusions that a dampened Sting-dependent interferon response is allowing bats to harbor a large array of viruses.”

The research is not a “smoking-gun” showing that STING is a “direct or indirect factor in increased viral occupation of bat species,” he says.