In its thousands faces, evolution has granted some creatures the ability to perform deadly actions while defying death in ingenious ways. There are such interesting cases that people even decided to base their career studying them. This was the case of Veronica Saraiva Failho also known as “the girl of the dead pigs”, soon you will understand why. During her youth she frequently went for walks in the Brazilian forests with her grandfather and the sight of dead animals was common. However, despite the horrible smell and the macabre sight, Veronica always found a reason for excitement in these encounters. She was fascinated by how much life was originating from a single death. There were often dung beetles feasting on these carcasses (yes, they don’t all feed on feces, some of them find dead carcasses tastier). Right away Veronica noticed how different species of beetle had a predictably different behavior and today she is studying the reasons behind it.

_{Image CCO Creative Commons Source}

Originally, the most popular explanations were that bats can resist infection because they can produce large amounts of naïve antibodies. Another possibility is the increase in temperature that occurs in bats during flight. In fact, most bats can reach 40°C while they fly, this temperature is not suitable for the survival of many pathogens. However, we recently discovered another feature of bats that is likely responsible for their tolerance to viruses. It all started with a genomic study that highlighted highly conserved mutations in the DNA of different species of bats. These mutations were concentrated in genes responsible for DNA damage checkpoints and also in genes regulators of innate immunity. Eventually scientists pinned down the likely protein responsible for the high tolerance of infections, the name of the protein is STING (stimulator of interferon genes). In every other mammal, STING is a protein that detects abnormal presence of DNA in the cytoplasm of cells (which is generally due to the presence of viruses) and as a response it alerts the immune system against the infection by triggering the production of interferon. In bats, however, there is a mutation in the gene that encodes for STING, as a consequence, the protein has a slightly different activity. The bat’s STING protein in fact activates only a milder interferon response, thus preventing the bat’s immune system to go in “overdrive” mode during viral infections. One of the reasons viruses are so deadly to us is because of the storm of interferon production that they cause, overwhelming our immune system. Being tuned to generate only a mild response, the STING protein in bats prevents this from happening.

Still, why bats are so likely to carry viruses? Probably it’s because they live in communities of hundreds of other bats, thus facilitating the spreading of viruses. Also, the fact that bats do not get sick from carrying a virus means that they are likely to contributing to its spreading for longer periods of time. Unfortunately for us, the high temperature of bats is not sufficient to kill all the viruses, it actually could select “super-viruses” capable of surviving to high temperatures, much higher than what a feverish person could reach. This could make the viruses carried by bats even deadlier.

References