Bat Immune Systems: The Original Antivirus Programs

Bats stay healthy while hosting some of the world’s deadliest viruses. Scientists are just beginning to understand how.

Hannah Thomasy, PhD headshot
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Bats have many adaptations, some of which are consistent across different species, that possibly contribute to their unusual resiliency to viral infections. However, bats are a heterogeneous group, with major lineages diverging more than 50 million years ago, so different evolutionary pressures may have given rise to important species-specific adaptations.

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A) DNA Sensors

Several species of bats have lost the entire PYHIN gene family.1 Pyrin and hematopoietic interferon-inducible nuclear domain (PYHIN) proteins sense DNA, either from pathogens or the host’s own damaged DNA, and trigger an inflammatory response. Loss of this gene family may explain bats’ ability to limit harmful virus-induced inflammation.

B) Escape From Viral Antagonism

While some pathogen sensors have been lost, others have diversified. Protein kinase R (PKR) proteins are activated by double-stranded RNA, which signals the presence of a viral infection, and can then initiate an antiviral response. Many viruses, including some poxviruses, herpesvirus, and influenza viruses, have evolved ways to interfere with PKR function. Researchers think that PKR gene diversification may help bats escape this viral interference.2

C) Interferons

Interferons are key players in the antiviral response. Different bat species display differences in interferon genes and regulation of interferon expression. Some species show constitutive expression of interferon-α, while others have a notable expansion of the less studied interferon-ω genes.3,4

D) Inflammasomes

Bat ASC2 (apoptosis-associated speck-like protein containing a CARD 2) inhibits activation of the inflammasome. While inflammasome signaling is important for the antiviral response, overactivation has also been implicated in mortality for certain viruses, including influenza. Indeed, researchers showed that bat ASC2 increased the survival of influenza-infected mice.5

E) Possible Self-vaccination

A recent study on bat induced pluripotent stem cells revealed an unusually large number of endogenous viral sequences.6 While still unsubstantiated, the study’s authors suggested that future research should test whether these endogenous viral sequences serve to “defend against viruses and microbes and encode viral proteins in a self-vaccination scheme.”

F) Undiscovered Mechanisms

Bats are a diverse group with more than 1,400 species. According to approximate counts from the Bat1K gene sequencing initiative, very few species have fully sequenced genomes.7 Thus, many potential antiviral or anti-inflammatory mechanisms remain to be discovered.

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Meet the Author

  • Hannah Thomasy, PhD headshot

    Hannah Thomasy, PhD

    Hannah joined The Scientist as an assistant editor in 2023. She earned her PhD in neuroscience from the University of Washington in 2017 and completed the Dalla Lana Fellowship in Global Journalism in 2020.

Published In

Spring 2024 cover
Spring 2024

Turning on the Bat Signal

Research into bat immune systems may help keep humans safe from viral attacks.

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