Long-lived bats offer clues on diseases
2012-12-21 14:13
Hong Kong - 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
minimise 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 000km 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."
