Summary in seconds: exploring bats’ distinctive features, bats’ role as asymptomatic viral reservoirs, bats’ avoidance of viruses, revealing an antiviral protein in bat genes, and an ongoing 60-million-year arms race between bats and viruses.
Ranked as the second most diverse and geographically widespread mammalian order, bats emerge as truly unusual creatures. Beyond their unique capability of powered flight, certain bat species function as asymptomatic reservoirs for many viruses1. Furthermore, with more than 1200 species and approximately 60 million years of divergence, bats have coevolved with a large diversity of viral pathogens2. This intricate journey alongside a myriad of viral pathogens has granted bats specific adaptive changes enabled bats to efficiently control viral infections.
Numerous bat species are natural reservoirs for viruses that are highly virulent in other mammals, such as Marburg virus, Nipah virus, and severe acute respiratory syndrome (SARS) coronaviruses. Remarkably, bats carry these viruses without displaying any noticeable symptoms themselves1. This intriguing contrast between bats and other mammals, notably humans and nonhuman primates, has sparked significant research endeavors aimed at elucidating the antiviral mechanisms employed by these airborne creatures.
According to a recently published research paper1, the remarkable ability of bats to host a plethora of viruses, fraught with danger or fatality for other mammals, while maintaining their own well-being, can be attributed to distinctive genetic mutations inherent to bats. These genetic mutations include the ability to replicate the gene housing the genetic code responsible for producing an antiviral protein known as “protein kinase R” (PKR) which is a major antiviral innate defense system.
These duplicated PKRs have undergone genetic diversification, which enable bats to collaboratively counteract and refine the control of DNA and RNA viruses. These findings suggest that viral-driven adaptations in PKR, potentially giving rise to immunity unique to bats2.
Furthermore, this study provides compelling evidence illustrating the evolutionary progression of the antiviral protein (PKR), stemming from repeated advantageous selection in the genomic duplication of the gene encoding this pivotal protein. This process of positive selection occurred repeatedly across successive bat generations spanning millions of years, setting bats apart from all other examined mammals which possess only a single copy of the gene responsible for PKR synthesis2.
Researchers believe that the duplication of the antiviral protein gene (PKR) stems from an ongoing evolutionary “arms race,” between bats and viruses, resulting in the emergence of immunity in bats to a wide range of viruses, over the course of their evolutionary history3.
Nevertheless, efforts to characterize the genetic diversity of bats broadly and comprehensively, compared to other mammals, remain very limited. In particular, conclusions primarily drawn from the study of a specific bat species and its related virus system. Therefore, there exists a pertinent requirement for meticulous comparative studies of bat antiviral effectors based on representative species. Such studies are essential for unraveling the intricacies and distinct attributes of antiviral immune mechanisms within the realm of chiropteran organisms.
Sources
1. A. T. Irving, M. Ahn, G. Goh, D. E. Anderson, L.-F. Wang, Lessons from the host defenses of bats, a unique viral reservoir. Nature 589, 363–370 (2021).
2. S. Jacquet, M. Culbertson, C. Zhang, et al., Adaptive duplication and genetic diversification of protein kinase R contribute to the specificity of bat-virus interaction. Science Advances. Vol. 8, issue 7 (2022).
https://www.science.org/doi/10.1126/sciadv.add7540