American scientists revealed how bats managed to harbor and transmit deadly pathogens without getting sick themselves.
A study published online Thursday in the journal Cell examined the genome of the Egyptian fruit bat and found larger-than-expected families of genes related to the mammalian immune system.
Scientists from Boston University found large families of interferon and natural killer genes that differed dramatically from their counterparts in other mammals.
The findings may eventually lead to a deeper understanding of virus transmission, and better treatments for humans who become infected.
"What we learn from bats may help us in the development of pharmacological agents," said Thomas Kepler, a professor of microbiology at Boston University and the paper's author.
Bats are known to carry several deadly pathogens, including Marburg and a SARS-like coronavirus, and transmit disease via bite or exposure to saliva, feces, or urine.
The researchers compared the Egyptian fruit bat genome to the genomes of other mammals, including a handful of other bats, humans, and guinea pigs.
"We were looking for gene families that had grown either much larger or much smaller than was expected, given the evolutionary history of this bat," said Stephanie Pavlovich in Kepler's lab at Boston University, the lead author of the paper.
They also looked for genes with evidence of "positive selection," the evolutionary process that propels new, useful genetic variants throughout a population. "That allowed us to find a number of genes that were evolving at a faster rate in this bat, and then also a number of gene families that were much larger than we expected," said Pavlovich.
They found two gene families near the top of the "larger than expected" list. The first is type 1 interferon genes, which are often called "the first line of defense" against viruses and have been implicated in the disease course of filoviruses like Marburg and Ebola.
The second is natural killer or "NK" cell receptors. Natural killer cells are a critical part of the human immune system, able to quickly recognize and respond to virus-infected cells.
Those findings point to the possibility of the so-called "soft protection" from the bat immune system.
"Activation and inhibition are much more intermingled in the bat than they are in most other organisms," Kepler said, regarding the NK cell receptors. "The bat may be assuaging the virus for a short period of time, trying to prevent the virus' growth without making a full-on attack."
