Egyptian Bat Genome Blows Open the Species’ Secret to Antiviral Immunity
Bats host a number of the planet’s high-profile viruses asymptomatically, including Ebola, rabies, Marburg and the SARS coronavirus notorious for causing extreme virulence in humans. Bats and others that chronically harbor viruses, such as rats or mice, are feared as disease reservoirs. Most of the time, these reservoirs stay intact, with infected animals rarely exhibiting symptoms of disease.
But at times when they cannot contain the virus, the pathogens infect new, much more vulnerable species. And this is almost certainly what happened with the Ebola trouble in West Africa, which began with a trickle and then went on to infected at least 8,900 people and killed more than 4,400.
Now, in order to shed light on the secret to the bats’ immunity, and point to new therapies to fight lethal viruses, a team of scientists sequenced, assembled, and analyzed the genome of Rousettus aegyptiacus, a natural reservoir of Ma
rburg virus and the only known reservoir for any filovirus.“Using that DNA, we generated the most contiguous bat genome to date and used it to understand the evolution of immune genes and gene families in bats. This is classical comparative immunology and a good example of the link between basic and applied sciences,” explained co-senior author Gustavo Palacios, Ph.D., who heads the Center for Genome Sciences at the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID).
The team discovered a MHC class I genes, and type I interferons belonging to bats which dramatically differ from their counterparts in other mammals; a theoretical function evaluation of these genes suggested that a higher threshold of activation of some component of the immune system may exist in bats.
NK cells are immune cells that play a crucial role against viral infections and their activity is regulated by an array of activating and inhibiting receptors. In this work, the team describes finding genomic evidence of a bias toward the inhibitory signal in NK cells.
“Further evaluation of these expanded sets of genes suggests that other key components of the immune system like the MHC- and the IFN-loci in bats may have evolved toward a state of immune tolerance,” said Mariano Sanchez-Lockhart, Ph.D., of USAMRIID.
The team says their next step is to build on the knowledge gained thus far to compare antiviral responses between bats and non-human primates. Ultimately, this information could be employed to understand the correlation of protection in bats and therapeutics against Marburg virus and other lethal filovirus infections.
