How Bats Live With Viruses

Bats present a biological paradox: they harbor viruses capable of causing severe disease in humans yet seldom show symptoms themselves. A study published in Science Advances by researchers at Tulane University, with collaborators at Stanford University and the Centers for Disease Control, now points to a previously unknown feature of the bat immune system that may help explain this tolerance.

The team discovered that vesper bats—the world’s largest bat family, with more than 500 species on every continent except Antarctica—possess two distinct copies of the genes that produce the heavy chains of antibodies. In all other known mammals, including humans, only a single set of heavy-chain genes exists. This duplication provides vesper bats with an additional route for generating antibody diversity, the variation needed to recognize and neutralize a wide array of pathogens.

Antibodies are composed of two heavy protein chains and two light protein chains. Typically, the heavy chains are assembled from one gene system. In vesper bats, however, two separate heavy-chain gene systems operate in parallel. “We’ve never seen anything like this in a mammal before,” said Hannah Frank, corresponding author of the study. “This completely changes our understanding of how mammalian immune systems can be organized and raises exciting new questions about why bats have been so evolutionarily successful and how they respond to viruses.”

While past research has emphasized bats’ innate immune defenses, this finding shifts attention toward their adaptive immune system. “We think this discovery is an important piece of the puzzle,” Frank said. “It doesn’t fully explain why bats are such effective viral reservoirs, but it reveals a level of immune variety we didn’t know existed and gives us an entirely new direction to explore.”

Bats play vital ecological roles as pollinators, seed dispersers, and natural pest controllers, yet they also serve as natural hosts for many viruses. Understanding how they coexist with these viruses without becoming ill may eventually help scientists better understand immune responses across species and improve strategies for preventing disease spillover.