Vesper bats, the largest family of bats on Earth, carry an antibody-generating system unlike anything previously documented in a mammal, according to a study led by researchers at Tulane University with collaborators at Stanford University and the Centers for Disease Control and Prevention. The findings, published in the journal Science Advances, describe more than 500 vesper bat species as possessing two entirely separate sets of antibody heavy-chain genes, where every other mammal studied to date has only one.
Working primarily with the big brown bat, a species common across North America, the team found the animal carries two distinct heavy-chain gene systems that are not redundant copies of each other. One set, built from 33 genes, undergoes heavy mutation and refinement to produce antibodies that bind a single target very precisely. The second, built from 99 genes, changes far less and instead produces a broader spread of antibodies that bind many targets loosely. In humans and all other mammals examined so far, antibody heavy chains are assembled from just one such gene locus.
"We've never seen anything like this in a mammal before. This completely changes our understanding of how mammalian immune systems can be organized," said corresponding author Hannah Frank, an associate professor of ecology and evolutionary biology at Tulane, whose team included coauthors from the CDC's virology programs and Stanford's Boyd Lab. Some of the underlying gene-sequencing work behind the discovery was first reported in late July, with the peer-reviewed paper and wider coverage of the finding following in early September.
A Long-Standing Mystery About Viral Tolerance
Vesper bats, found on every continent except Antarctica, belong to a family long studied for an unusual trait: many species can carry viruses that are lethal to humans and other mammals, including relatives of the pathogens behind Ebola, SARS and Nipah virus infection, without becoming seriously ill themselves. Scientists have proposed several explanations over the years, from dampened inflammatory responses to unusually efficient DNA repair linked to the physiological demands of flight. A second, more flexible antibody system gives researchers a new candidate mechanism to test.
Frank was careful to note the discovery is not a complete explanation. The dual gene system "doesn't fully explain" why bats tolerate so many viral infections, she said, but it "reveals a level of immune variety we didn't know existed" — meaning it may work alongside other adaptations rather than instead of them. Researchers say the next step is to determine whether the second antibody system is unique to vesper bats or turns up in other bat families once they are examined with the same methods.
The work adds to a growing body of research into bat immunology motivated partly by public health concerns, since several serious viral spillovers into humans have been traced to bat reservoirs. Understanding exactly how bats coexist with pathogens that are dangerous to people could eventually inform strategies for predicting or blunting future spillover events, though the authors caution that translating a genetic discovery in bats into practical tools for human medicine remains a long-term prospect.
