Bats: Corona Without Symptoms

Bats are fascinating due to their unique characteristics. As the only mammals capable of flight, they play an important role in the ecosystem: they pollinate plants, spread seeds, and contribute to the balance of insect populations with their feeding habits. Thanks to their exceptional orientation by means of ultrasonic echolocation, they are ideally adapted to their nocturnal lifestyle. “In addition, bats are also of great interest for medical research: The analysis of their immune system and their unique viral tolerance can provide valuable insights for the development of new therapies and drugs,” explains Prof. Dr. Michael Hiller, spokesperson of the former Hessian LOEWE Center for Translational Biodiversity Genomics and Professor of Comparative Genomics at Frankfurt’s Goethe University and the Senckenberg Research Institute and Natural History Museum Frankfurt, and he continues, “They are also known to carry numerous viruses, including those that are transmissible to humans, such as coronaviruses. However, it is interesting to note that bats do not show any symptoms of disease when infected with such viruses.”

Together with an international research team, Hiller sequenced high-quality genomes of ten bat species as part of the “Bat1K” project, including species known to carry coronaviruses and other viruses. “The bats’ ability to control viral infections without getting sick is probably due to special adaptations of their immune system. To determine which genes are involved, we used the new bat genomes to analyze a total of 115 mammalian genomes and systematically searched their genes for signs of genetic adaptations,” explains Hiller. Such adaptations can be detected as traces of positive selection and may indicate functional changes.

The result of the extensive analysis shows that bats exhibit such adaptations in immune genes much more frequently than other mammals. The study’s first author, Dr. Ariadna Morales, formerly of the LOEWE-TBG and now with the Senckenberg Research Institute and Natural History Museum Frankfurt, emphasizes, “Our investigations show that the common ancestor of all bats has an unexpectedly high number of immune genes with selection signatures. This suggests that the evolution of the bats’ immune system could be closely linked to the development of their ability to fly.”

The research team paid particular attention to the ISG15 gene, which is associated with a severe course of COVID-19 in humans. The examined bats showed important changes in the protein sequence in this gene. Experiments in cell lines conducted by Prof. Dr. Aaron Irving from the Zhejiang University School of Medicine in China and Prof. Dr. Arinjay Banerjee from the University of Saskatchewan in Canada showed that in some bats, the ISG15 gene is able reduce the production of SARS-CoV-2 viruses by 80 to 90 percent. In contrast, ISG15 from the human genome showed no antiviral effect in this experiment.

“Thus, the ISG15 gene is likely one of several factors that contribute to viral disease resistance in bats,” summarizes Hiller, and he continues, “These promising results can be used as a basis for further experimental studies, which are necessary to decipher the unique adaptations of the bats’ immune system.”

The study highlights the potential for gaining new insights into the management of viral diseases through research into bat genomes. Together with other “Bat1K” researchers, Hiller will address this question as part of an ERC Synergy Grant. The results could lead to innovative strategies in medicine in the long term.

Publication: Ariadna E. Morales et. al. (2025): Bat genomes illuminate adaptations to viral tolerance and disease resistance. https://www.nature.com/articles/s41586-024-08471-0