By Tan Ee Lyn
HONG KONG (Reuters) - The bat, a reservoir for viruses like Ebola, SARS and Nipah, has for decades stumped scientists trying to figure out how it is immune to many deadly bugs but a recent study into its genes may finally shed some light, scientists said on Friday.
Studying the DNA of two distant bat species, the scientists discovered how genes dealing with the bats' immune system had undergone the most rapid change.
This may explain why they are relatively free of disease and live exceptionally long lives compared with other mammals of similar size, such as the rat, said Professor Lin-Fa Wang, an infectious disease expert at the Duke-NUS Graduate Medical School in Singapore who led the multi-centre study.
"We are not saying bats never get sick or never get infections. What we are saying is they handle infections a lot better," Wang said in a telephone interview.
What was missing from both species of bats was a gene segment known to trigger extreme, and potentially fatal, immune reactions to infections, called the cytokine storm.
Cytokine storms end up killing not only offending viruses in the body, but the host's own cells and tissues too.
"Viruses rarely kill the host. The killing comes from the host's immune response. So it looks like what bats are doing is depress the inflammation (cytokine storm). If we can learn that, we can design drugs to minimize the inflammation damage and control viral infection," Wang said.
The study, which saw the participation of researchers from China, Denmark, Australia and the United States, was published on Friday in the journal Science.
Compared with other mammals of similar size, bats live a long time, with lifespans of between 20 and 40 years. Rats live between 2 and 3 years, on average.
IMMUNE GENES LINKED TO FLIGHT
Interestingly, Wang and his colleagues found that the highly evolved genes that give bats their superior immune system also enable them to fly.
Out of more than 5,000 types of mammals on the planet, bats are the only one capable of sustained flight and some species can fly more than 1,000 km in a single night.
Such intense physical exertion is known to produce toxic "free radicals" that cause tissue damage and it is these same genes that give the bat the ability to repair itself, Wang said.
"What we found was the genes that evolved fastest were genes involved in repairing DNA damage. That makes sense ... because when you fly, metabolism goes up and it generates free radicals that are toxic to cells," Wang said.
"Because bats fly, they (would have had) to evolve and adapt ... to get genes that can repair DNA damage."
Wang said we have much to learn from the bat, which has evolved to avoid disease and live exceptionally long lives.
"Cancer, ageing and infectious disease, these are the three major areas of concern for people," he said.
"We have studied rats for 150 years to understand how to do better in these three areas. Now we have a system, the bat, that has done very well in evolution. We can learn from the bat. With modern techniques, we can design new drugs to slow down the ageing process, treat cancer, fight infections."
(Editing by Robert Birsel)