BioScience Taking Its Cue From Bat Genetics
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"It's very intriguing. I wake up thinking about it every day.""Why do bats have this immune response that's so different from ours and so different from other mammals."Arinjay Bannerjee, researcher, Toronto"Rather than trying to reinvent the wheel, we could learn from what evolution has developed in a bat where the outcome is not disease but it's something that enables survival upon infection with a particular virus.""If we figure that out, then maybe we can apply the same principles and modulate the immune response in humans."Judith Mandl, cellular immunologist, McGill University, Montreal
Dr.Bannerjee is an expert in bat virology, with experience in isolating dangerous pathogens -- who has studied how bats interact with viruses such as the virus causing Middle East respiratory syndrome, one of many coronaviruses harboured by mammals. We know bats as vectors of deadly viruses -- hosts of an older MERS version, which took the zoonotic role of leaping from animal to human.
Bats are suspected of acting as a viral reservoir of the Ebola virus, hosts for Hendra, Nipah and Marburg viruses each of which can be lethal in humans. The animals, on the other hand, appear not be harmed by these viruses they host and scientists would dearly like to know why that is and how it comes about. Many suspect the key to the mystery lies in the bat's immune system's special features that spark responses to viral invasion quite at variance from what happens when a human immune system reacts.
Viruses that live in wildlife are seen to cause little harm to their natural hosts. It is when they make that leap from animal host to human as a zoonotic that the problem arise,s for while the animals may have developed a long evolutionary history with these viruses, humans lack that and the human immune response may often go haywire, over-responding to the presence of a invasive foreign threat, causing a massive and destructive inflammation effect often ending up destroying internal organs, leading to death.
Assorted water birds carry various strains of influenza A -- and pigs host hepatitis E, as examples, without discernible harm to themselves. Similarly when bats become virus-infected they don't become ill. "They can remain in good health and display no discernible signs of disease", Raina Plowright, infectious-disease ecologist and wildlife veterinarian at Montana State University in Bozeman, notes.
Animals appear to have developed disease tolerance in their immune system, limiting damage to the host, accommodating itself to the low-level presence of a pathogen. Studies focus on one or a few species of bats out of the total 1,300 bat species, and studies recently undertaken suggest that immune system tolerance reflects how bats interact with many of the viruses they carry. Mounting a speedy but nuanced offensive that halts the virus from viral multiplication.
At the same time, and crucially, the immune system diminishes the activity of immune foot soldiers to prevent a massive inflammatory response capable of producing far more harm to the host than would the virus itself. Some bat species appear to be possessed of a number of genes to produce interferons. The Egyptian fruit bat naturally hosts Marburg virus and has 46 interferon-producing genes -- as compared to the 20 that humans possess.
Since interferons interfere with viral replications, this is a critical advantage for the bats -- as it would be for humans possessing a greater number of such genes. The critical issue is that out-of-control inflammation reflects a common threat in severe illnesses from viruses. People infected with deadly filoviruses such as Ebola see a wholesale bombardment of inflammation-causing molecules which in turn spur failure of multiple organs resulting in septic shocklike syndrome.
Called a cytokine storm, the dire condition was found in people who reacted badly with SARS, a condition that sees many of the most ill patients with COVID-19 suffer, and die. Bats "really seem to throttle inflammation", evolutionary biologist Emma Teeling of University College Dublin states, herself co-funder of a major effort to explore bat genomes.
Labels: Biology, Bioscience, Medical Nightmare, Research, SARS-CoV-2
posted by Pieface @ Tuesday, July 28, 2020
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