A tale of endurance: bats, viruses and immune dynamics
Creators: name: Apoorva
name: Singh, Sunit Kumar
Publisher: name: Taylor & Francis
Year: 2024
Subjects: subject: Medicine
subject: Microbiology
subject: FOS: Biological sciences
subject: Evolutionary Biology
subject: Environmental Sciences not elsewhere classified
subject: Ecology
subject: Biological Sciences not elsewhere classified
subject: Mental Health
subject: Infectious Diseases
subject: FOS: Health sciences
subject: Virology

description: The emergence of highly zoonotic viral infections has propelled bat research forward. The viral outbreaks including Hendra virus, Nipah virus, Marburg virus, Ebola virus, Rabies virus, Middle East respiratory syndrome coronavirus, SARS-CoV and the latest SARS-CoV-2 have been epidemiologically linked to various bat species. Bats possess unique immunological characteristics that allow them to serve as a potential viral reservoir. Bats are also known to protect themselves against viruses and maintain their immunity. Therefore, there is a need for in-depth understanding into bat-virus biology to unravel the major factors contributing to the coexistence and spread of viruses. Bats are the most diverse mammalian order, with over 1400 species found worldwide. Studies on bats have revealed that they frequently carry and transmit multiple viruses. They are also known to recover from viral infections. Further, human interference and climatic changes in bats' native habitat have led to virus spillover events from bats to human populations, posing a serious public health risk. A deeper understanding of the coexistence of bats and viruses, as well as the mechanisms of disease transmission to humans, is required to minimize the risk of future viral outbreaks. The review summarizes the existing literature on the co-existence between bats and viruses. Bats are the most diverse species in the mammalian order. Numerous coronaviruses, filoviruses, henipaviruses, lyssaviruses and paramyxoviruses have been identified in bats. Bats possess unique physiological and immunological characteristics and serve as a potential viral reservoir. Evolution of flight and altered metabolic activity in bats provide tolerance against viral infections. Constitutive expression of IFN and ISGs, increased expression of HSPs, and the always-on antiviral system limits viral replication in bats. Suppressed activation of DNA sensors like STING, dampened inflammasome sensor NLRP3, and loss of PHYIN gene family provide immune tolerance in bats. Geographical distribution, long lifespan, high-density roosting habits, echolocation aid in viral transmission/spillover events. Thermoregulation, food availability, climate change and reproductive patterns are also reported to influence the likelihood of viral spillover events. Mostly viral isolates from human and virus stocks produced in non-bat cell lines have been used for bat infection studies. Isolation of bat-borne viruses from their natural host will provide a more definitive picture. Many fundamental mechanisms driving immune dynamics and disease transmission remain inadequately characterized. Adaptive evolution has shaped bats' immune systems to balance defense and tolerance, resulting in an impressive ability to harbor viruses highly pathogenic to other host species. Continuous surveillance program and global initiatives based on the one health approach will help in early reporting of zoonotic viral infections.