Vesper Bats Have a Double Set of Antibody Genes Never Seen in Mammals

Scientists have long been intrigued by how bats can carry viruses capable of causing severe disease in other animals while rarely becoming seriously ill themselves. Researchers at Tulane University, working with collaborators at Stanford University and the Centers for Disease Control and Prevention, may have identified part of the answer. A study published in Science Advances found that vesper bats, the world's largest family of bats, carry two distinct copies of the genes involved in producing antibodies — proteins that help the immune system identify and fight infections. Every other known mammal has only one such set of genes.

Vesper bats are a group of more than 500 species found on every continent except Antarctica. Antibodies are Y-shaped proteins built from two heavy protein chains and two light protein chains; in humans and all other known mammals, the heavy chains are produced using a single set of genes. Vesper bats, the researchers found, have two separate heavy-chain gene systems, potentially giving them another way to create a wider variety of antibodies.

"We've never seen anything like this in a mammal before," said Hannah Frank, associate professor of ecology and evolutionary biology at Tulane University and 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." Researchers studying bat immunity have traditionally focused more on the innate immune system, and Frank said the new findings show the antibody-producing adaptive immune system also deserves closer study.

Bats play important ecological roles as pollinators, seed dispersers and natural pest controllers, while also serving as natural hosts for many viruses. Frank said the discovery does not fully explain why bats are such effective viral reservoirs, but reveals a level of immune variety not previously known and opens a new direction for research that could eventually help scientists better understand immune responses in other species, including strategies for reducing the risk of disease spillover.