Bats can harbour some of the world's most deadly viruses without ever getting sick and researchers in Singapore are trying to find out how they do it. By investigating the creatures' genetic structure, the scientists hope to eventually find the key for humans to fight infectious disesases.Ian Mendenhall, a researcher at Duke-National University of Singapore's Emerging Infectious Diseases department, says bats have been found to harbour a variety of viruses including rabies, influenza, SARS and Ebola, without ever being effected by them.
"Absolutely. When we're catching live bats, we typically take an oral swab, an anal swab, some feces and also some blood. Most pathogens have a particular cell tropism, or an affinity where they like to infect specific cells, so if we sample the mucus membranes, there are specific viruses that we expect to find there," he said.
While those viruses can be fatal when transmitted to humans and other animals, they have almost no effect on bats.
Mendenhall and his colleague, Wang Lin-Fa, the head of the Duke-National University of Singapore's Emerging Infectious Diseases department, are trying to find out why. Based on their experiments, they believe there is a connection between the bats ability to fly and the unsual durability of their cell structure.
Wang says bats are the only flying mammals, and flight takes a great deal of energy. The higher metabolic rates required to supply this energy also produces toxic by-products called free radicals that damage DNA. Through analysis of bat genomes the team has concluded that the animals have evolved ways to protect their cells against this damage.
"Some genes involved in DNA damage repair also play a role in the immunity, so immunity is very important for our body to fight infection. So what we think, is that that explains bats carry a lot of deadly viruses, but they don't develop the disease when humans or animals do," Wang said.
He says it might also explain the creatures' exceptional longevity relative to its size and high metabolic rate.
He says a group of genes involved in inflammation is completely absent in bats. Inflammation is the body's response to an invader, such as a virus, resulting in viral illness.
Mendenhall and Wang used a whole-genome sequencing technique to examine the genomes of two bat species, a study that Wang says revealed insights into their unique biological structures. The species are distantly related - the fruit bat Pteropus alecto, is native to Australia, Papua New Guinea, and Indonesia, while the insect-eating bat Myotis davidii, also known as David's mouse-eared bat, is found in China.
The team, which also included researchers from China, Denmark, and Australia, then compared the two bat genomes with genomes of other mammals which, they say, revealed genetic clues that might account for the bats' unique characteristics.
Wang says he hopes that within the next five years, his team will be able to develop a way to map DNA variants at the core of bats' immunity, and adapt them for use on humans.
"Because humans and bats, although we're very different, but we're all mammals, so we still share certain genes and pathways. It may be just the level of expression of certain genes that are different, or the location of the expression is different, so if we understand how bats do that, we may be able to apply that in humans either by -- nowadays we can do genes therapy, and we can design new drugs, to induce this sort of genes as what they are doing in bats," he said.
Wang says he hopes the findings will shed light on new ways to prevent and control emerging infectious diseases that affect both humans and livestock.