Vesper Bats May Have Two Antibody Gene Systems, Offering New Clues to Their Viral Resistance
Bats can carry viruses that cause serious diseases in humans and other animals, yet they often remain remarkably healthy. New research has identified an unusual feature of bat immunity that may help explain how these mammals tolerate infections.
Scientists studying vesper bats — the world’s largest bat family — found evidence that the animals may have two separate genetic systems for producing the building blocks of antibodies. This type of immune-system arrangement has not previously been documented in mammals.
“It was really surprising,” study co-author Hannah Frank, an associate professor of ecology and evolutionary biology at Tulane University, told Live Science. “The only other vertebrates we see something similar in are fish.”
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The findings, published Wednesday (July 29) in the journal Science Advances, could provide new insights into viral infections, bat biology and the evolution of the mammalian immune system.
“The study provides a novel view into the evolution and diversity of adaptive immunity in bats,” said Daniel Becker, an associate professor of biology at the University of Oklahoma who was not involved in the research. “The duplication seen in vesper bats is really intriguing and suggests that we need more immunological study of this globally distributed family of bats.”
How bat antibodies may differ from those of other mammals
Antibodies are Y-shaped proteins that help the immune system identify and neutralize foreign invaders, including viruses, bacteria and toxins. Each antibody is made from two heavy chains and two light chains — structures that work together to recognize specific features of pathogens and other targets.
The tips of the Y-shaped molecule bind to a target, while other regions determine how the immune system responds. Antibodies may block pathogens from entering cells or flag them for destruction by other immune cells.
In humans and most other mammals, the genes that produce antibody heavy chains are arranged in one region of the genome, known as a locus. Immune cells generate many different antibodies by combining gene segments within that region.
When Frank and her colleagues analyzed 26 bat species, they discovered two complete heavy-chain loci on separate chromosomes. Further testing showed that both groups of genes were functional and actively used by immune cells to produce antibodies.
The result was so unexpected that the researchers initially considered whether it might have been caused by an error during genome assembly. However, Frank’s collaborator and former graduate student Dr. Taylor Pursell suspected that the finding was genuine.
“She said, ‘No, Hannah; this is really weird — this doesn’t happen,'” Frank recalled. “And I said, ‘Oh my God; you’re right. This is not just an experimental annoyance. This is actually super cool.'”
Hannah Frank holds a bat skeleton in her laboratory.
(Image credit: Kenny Lass/Tulane University)
Two antibody gene systems could increase immune diversity
Genetic analysis showed that one of the two antibody loci contained a larger and more varied collection of gene segments. These segments could help bats generate a broad, ready-made repertoire of antibodies.
The second locus contained fewer gene segments but appeared to depend more heavily on somatic hypermutation. During this process, antibody-producing cells make small genetic changes after encountering a pathogen. Those changes can help antibodies become more precisely adapted to a specific threat.
Frank compared the arrangement to the different layers of defense shown in the 1998 Disney movie Mulan. Guards at the Great Wall raise an alarm before knowing exactly who is attacking, much like the innate immune system, which provides a rapid and broad first line of defense. The adaptive immune system is more targeted and can respond to a specific pathogen, although it usually takes longer to develop.
This study suggests bats have more diversity to start with, which may allow for faster and more effective responses from the start of an infection.
Michael Letko, molecular virologist at Washington State University
Innate and adaptive immunity are not unique to bats. However, having two antibody-producing systems may give vesper bats an additional layer of immune protection.
“From each locus, bats can create a cache of trainable, customizable cells,” Frank said. This flexibility could help bats respond to a wider range of viruses and other threats than many other mammals can.
“This extra set of genes gives the animals more diversity in their antibodies,” said Michael Letko, a molecular virologist at Washington State University who was not involved in the study. “This study suggests bats have more diversity to start with, which may allow for faster and more effective responses from the start of an infection.”
Letko added that the study’s genetic analysis strengthens the findings. “It is hard to dispute the validity of information solidly founded on the genetic organization of these bats,” he said.
More research is needed to understand bat immunity
The proposed benefits of the two antibody systems remain a hypothesis. Frank and her team must observe how the systems respond when bats are exposed to viruses before scientists can determine exactly what advantages the duplicated antibody loci provide.
“We think this discovery is an important piece of the puzzle,” Frank said in a statement. “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.”
Earlier research has suggested that other features may also help bats tolerate viruses. These include higher body temperatures and a larger number of virus-filled packages in stem cells.
Understanding how bats tolerate infections could help scientists predict which bat species may pose the greatest risks to human health and identify ways to reduce those risks, Becker said. Bats also have unusually low rates of tumors and cancer, raising the possibility that their immune systems could offer clues about cancer resistance.
Although bats are often viewed primarily as carriers of infectious diseases, their biology is far more complex, Frank said.
“Let’s learn from the guys who’ve been evolving with them — viruses — for millions and millions of years,” Frank said. “But let’s try not to villainize them for surviving for millions and millions of years.”
Pursell, T., Reers, A., Mikelov, A., Kotagiri, P., Lam, B., Ellison, J. A., Boyd, S. D., & Frank, H. K. (2026). Immunoglobulin heavy chain locus duplication in bats. Science Advances, 12(31).
Source: www.livescience.com