Australians scientists have discovered why bats do not get sick from viruses like Ebola, which could provide the key to combating the deadly diseases in humans.
Bats have long been known to carry more than 100 viruses, including Ebola, Hendra and the Middle Eastern Respiratory Syndrome (MERS), but the big question has always been why they do not get sick or show any signs of disease from the viruses.
The scientists at the CSIRO’s Australian Animal Health Laboratory in Geelong have discovered that unlike humans, bats keep their immune systems switched on 24/7 and the results have been published in the journal Proceedings of the National Academy of Sciences.
Bat immunologist Dr Michelle Baker said the bat’s immune system worked essentially as a preventative barrier, maintaining an elevated innate immune response even when they were not infected with any detectable virus.
In comparison, the human immune system operates in response to a foreign organism such as a virus or bacteria entering the body.
“Unlike people and mice, who activate their immune systems only in response to infection, the bat’s interferon-alpha is constantly ‘switched on’ acting as a 24/7 frontline defence against diseases,” Dr Baker said.
“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.
“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.”
The scientists found that bats have only three chemical hormones – or interferons – which fight off infection, much less than the number of interferons found in humans.
“This is surprising given bats have this unique ability to control viral infections that are lethal in people and yet they can do this with a lower number of interferons,” Dr Baker said.
Scientists will now be able to look at how they can redirect other species’ immune responses to behave in a similar manner to bats, which could dramatically cut death rates associated with diseases, such as Ebola.
Interferon therapy is already used to treat patients with conditions such as hepatitis C and multiple sclerosis but there are toxic side effects from large doses of interferons.
“If we can redirect that response so it doesn’t stimulate the toxic effects but it does trigger the anti-viral responses, that would be fantastic,” Dr Baker said.
The next step, in what will be a long process, will be to understand how bats are able to tolerate high levels of interferon without toxic side effects seen in humans.
Early indications are the bat interferon induces genes which are less inflammatory than those which are switched on in other species.
The international research has been led by the CSIRO, along with Duke-NUS Medical School and the Burnet Institute.