What bat genes can tell us about coronaviruses

Bats have proteins in their cells that are more pressured by coronaviruses than the same proteins in other mammals, researchers found. That information may help scientists understand more about potential future pandemics.

Scientists have wondered about the relationship between these receptors and coronaviruses in different types of mammals, but they are especially interested in bats, since biologists suspect the virus responsible for the COVID-19 pandemic likely evolved from viruses found in bats.

“COVID-19 hit and everybody is thinking about bats and coronaviruses,” said Hannah Frank, an assistant professor at Tulane University and lead author of a study published recently in Proceedings of the Royal Society B.

Like many of us, Frank was sitting at home in March 2020, at the start of the pandemic in the United States, when she realized the data she had been collecting on bat evolution along with public data might help us better understand bats’ relationships with coronaviruses.

“In previous studies, people have gone out and actually taken samples from bats,” she said, “and there’s this clear link between bats having a lot of diverse coronaviruses, especially ones related to SARS. But it’s a little unclear whether that’s a recent link or if bats have evolved with these coronaviruses.”

SARS-related coronaviruses enter mammal cells by attaching themselves to proteins used for other purposes. In the case of SARS-CoV-2, the virus binds to the ACE2 protein, which helps regulate blood pressure. Another widespread coronavirus, MERS-CoV, which causes Middle East Respiratory Syndrome, binds to the DPP4 protein, which is used for breaking up peptides in the body.

Generally, if a species has similar ACE2 to humans, there’s a good chance they can be infected with SARS-CoV-2, Frank said. But, Frank and her colleagues found, even if a mammal species’ ACE2 is strikingly different from humans, both species can be affected. That can make it difficult to predict which species will be infected by this virus, she said.

By reviewing the genetic sequence of ACE2 and DPP4 in bats and other mammals, the researchers found evidence that bats have been evolving with coronaviruses for a long time. They also found that these “proteins were more likely to have an excess amount of change in bats than in other mammals,” she said.

Across the protein, there are points where there’s more pressure to change, they discovered. In bats, the amino acids that are contacted by the virus were more likely to change compared to amino acids in other parts of the protein. “That suggests the virus is causing it to change,” Frank said. There was more frequent pressure for the receptors to change in bats than in other mammal species. This could be one reason why bats are more likely to carry coronaviruses than other species. Looking across evolutionary lineages, they found that bats have been under pressure from these types of viruses for millennia.

As the world contemplates potential future coronavirus outbreaks, knowing that bats have diverse coronaviruses that they have evolved with for millennia may help researchers pinpoint where certain viruses may have evolved, Frank said, and avoiding contact with bats will help reduce spillover. Researchers may want to delve further into bats’ immune systems to better understand why bats don’t get sick from coronaviruses related to ones that can be fatal to humans.

This doesn’t mean we should be scared of bats, she said. They provide important ecosystem services, like pest control and pollination. But they are taxa that researchers need to pay attention to if we are going to understand the spread of coronaviruses, Frank said.

Header Image: Researcher Hannah Frank looked at the complex interactions between bats and coronaviruses and how they evolved together. Credit: Rusty Costanza