Where Ebola has killed more than 10,000 people, bats can happily carry diseases without so much as a slight temperature. How their “super immunity” works has been a mystery – until now.
Australian scientists discovered bats have a small set of immune molecules that work 24/7, and this knowledge could protect humans from lethal diseases.
In a paper published in the Proceedings of the National Academy of Sciences, a team from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) sequenced the genome of the Australian black flying fox, focusing on genes coding for molecules called “interferons”.
In humans and some animals, interferons are the first line of defence against a virus. Once riled up, they stimulate other genes to help stop the virus replicating.
Somewhat paradoxically, the black flying fox has fewer interferon genes than humans – or any other mammal sequenced to date.
So how can the bat’s immunity be supercharged by fewer interferons?
It turns out bat interferons run nonstop on autopilot. Where the cells of humans and other mammals only pump out interferons when they’re needed to fight off an infection, the team found bats constantly produce three of their interferons.
Having these interferons constantly on leaves their immune system ready to attack all the time, which the authors believe gives them the ability to coexist – quite healthily – with the otherwise lethal viruses they carry.
“In other mammalian species, having the immune response constantly switched on is dangerous – for example it's toxic to tissue and cells – whereas the bat immune system operates in harmony,” study author Michelle Baker said.
“If we can redirect other species' immune responses to behave in a similar manner to that of bats, then the high death rate associated with diseases, such as Ebola, could be a thing of the past.”
Meanwhile, a team of UK and Australian scientists have called for a new way to use the bats’ stellar virus-carrying ability to stop infectious disease from spreading in the first place.
In an Expert Review of Vaccines article they outlined that so-called “self-disseminating vaccines”, viruses genetically engineered to transmit but not cause disease, could be released to wild bat populations.
“You might infect a number of animals in a group and then hope that it the vaccine spreads naturally […] and reduces the incidence of transmission to humans,” author Alec Redwood from Perth’s Murdoch University's Institute for Immunology and Infectious Diseases told the ABC.
There are concerns – introducing genetically-engineered viruses may change the bats’ physiology or immunology, said CSIRO’s Gary Crameri. But “we must look to ever more novel means to manage the increasing risk [of emerging infectious diseases]", he added.
Looks like bats may prove to be much more than flying disease-carriers yet.
Viviane Richter is a freelance science writer based in Melbourne.
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