From longer lifespans to wings that make them the only mammals that can fly, bats are extremely unique animals. But the feature with the most scientific value is their unique immune systems. Bats have genes that allow them to host deadly viruses without getting sick. Scientists have discovered that bats manage to fight off Ebola, COVID-19, and even cancer.
Bats have a heightened innate immune response that stays on constantly, even when not infected with any detectable virus. This differs entirely from what happens in humans and mice, where immune systems are activated in response to infection.
A recent study by scientists at the Cold Spring Harbor Laboratory (CSHL) has identified the reason for this phenomenon – bat genes.
With the help of Nancy Simmons from the American Museum of Natural History, the scientists obtained genetic samples of the Jamaican fruit bat and the Mesoamerican mustached bat in Belize.
The experts sequenced the genomes of these bat species and compared them to those of other mammals. The comparison showed that the bat genomes have been streamlined over the years due to evolution, producing natural defensive abilities against infection and cancer.
Explaining the findings, Professor W. Richard McCombie demurred that the team never expected to see such a positive selection in bat genomes.
“We didn’t know immune system genes were so positively selected in bat genomes. Bats have a number of very unusual things about them. They don’t respond to infections the way we do. In retrospect, it’s not surprising this difference in the immune system may be involved in both the aging and cancer response,” he said.
Using the new Oxford Nanopore sequencing technology, the researchers sequenced the complete genomes of the two test bat species.
Upon comparing them to the sequences of 15 other bat and mammal genomes, including humans, they found an unexplained shift in the levels of two inflammatory protein-coding genes. These genes are called interferon-alpha and interferon-omega.
Armin Scheben, a postdoc and another scientist on the three-person team, said, “Bats have dialed down the immune system’s alarm by shedding genes that produce interferon-alpha. This may be responsible for their high viral tolerance. It prevents overactive immune responses that harm healthy tissue – one of the reasons infections are so damaging to humans.”
The scientists also found modifications in cancer-related genes in the bat genomes. These changes were more significant than what is found in other mammals, including six genes responsible for repairing DNA and 46 for suppressing tumors.
“Our work highlights how immunity and cancer response are deeply interconnected. The same immune genes and proteins play important roles in cancer resistance,” said Scheben.
The team plans to build on their findings by investigating the regulation of the immune genes in bats and their possible expression in different body parts. They hope their research can explain the links between cancer, aging, and immunity.
“Ultimately, we’ll take the work as far as we can and hand off the baton to experts in disease to work toward developing drugs or other therapeutics,” said study co-author Professor Adam Siepel.
The full study is published in the journal Genome Biology and Evolution.
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