Bats shelter the world’s deadliest viruses, including ebola, Marburg, Nipa and SARS. Why do they spread these viruses around, but they don’t get sick of themselves? Now, we may have glimpsed the secret that they can withstand these viruses – because flying is so hard.
Zhou Peng of the Wuhan Virus Research Institute of the Chinese Academy of Sciences and his team studied the immune systems of bats and other flying mammals. They focused on cytoplasm DNA. Cytoplasmic DNA is free in the cytoplasm, and one of its forms is a viral infection, allowing cells to replicate their genetic material, and high-intensity physical activity can have the same effect, with free radicals that accumulate in cells, destroying DNA and producing free DNA fragments.
Most mammals rarely require ultra-high-intensity exercise, so it is rare for their own DNA fragments to be free. Therefore, when their immune system detects cytoplasmic DNA, it directly uses it as a signal of virus invasion and attacks. This reaction is triggered by STING proteins, which use interferon to attack areas of viral infection.
However, due to the huge demand for physical fitness in flight, cytoplasm DNA is often produced in bats, which can be mistaken for virus infection signals in the immune system of early bats and then attack their own tissues. To avoid this problem, the bat’s immune response to the virus weakens during evolution, allowing the virus to coexist with the bat.
Mutated immune system
The team simulated infection of white blood cells in mice and Chinese chrysanthemum bats, respectively. The SARS incident in 2003 infected about 8,000 people and killed nearly 600 people worldwide, and the culprit of the SARS virus was the Chinese chrysanthemum manta ray. Studies have shown that mice produced at least 10 times the concentration of interferon seroched in Chinese chrysanthemum bats.
Chinese chrysanthemum bats (Rhinolophus sinicus)
They compared the STING genes in 30 species of bats with 10 unflying mammals (including humans) and found that all bats had STING proteins that were missing a serine at a specific location, while other mammals retained serine. The serine at this location determines the cell’s response to pseudo-viral invasion, and bats that lack this serine can coexist with viruses that other mammals cannot tolerate.
“Wild bats may carry a lot of viruses, but they all stay at a low level. This phenomenon is more like symbiosis than control,” Zhou said. “
According to John Mackenzie of Curtin University in Australia, studying the viruses in bats has a more profound meaning: “Because these viruses may lead to new global epidemics in the future, it is important to study how bats can stay healthy in their infestation.” “