About 85% of people with new coronavirus infection show mild or moderate symptoms, but about 15% can progress to severe disease, and 5% of them will eventually develop acute respiratory distress syndrome, septic shock or multiple organ failure. Why does the same pathogen infection make different results? "The hosts infected with the virus have different immune responses, which is a very important reason."

The biological structure of the virus is very simple, there is no condition that can support its own life to replicate or reproduce, and it must be parasitic in other host cells. To survive under the immune pressure of the host, the virus must continuously evolve. Similarly, the immune system will continue to evolve and improve in order to sustain the life of the host.

There are three main functions of the human immune system. One is immune defense, which mainly helps the body clear pathogenic microorganisms and other antigens. However, this function needs to be finely regulated. If the immune response or immune defense is too strong or insufficient, it may cause harmful pathological reactions, such as hypersensitivity or immune deficiency. Excessive antiviral immune response can not only clear the cells infected by the virus, but also may cause excessive cell damage, inflammation and even organ dysfunction, so the antiviral immune response process also has disadvantages. Immune deficiencies can cause insufficient immune defenses or inadequate immune responses, resulting in more susceptibility to pathogenic organisms, leading to infection of more pathogenic organisms.

The second is immune self-stabilization. Human cells are constantly growing, damaging, aging and dying. How to deal with damaged or aging cells? This depends on the immune system to identify and clear in time. But if the immune response that distinguishes damage and aging recognizes the wrong object and removes normal cells as damaged cells, this will lead to a pathological response, which is a change in immune self-stability, which we call autoimmune diseases, such as rheumatism Diseases, rheumatoid arthritis, etc. are all autoimmune diseases.

The third is the immune surveillance function. The immune system is like a patrol team. It patrols the human body at any time, which is conducive to the maintenance of normal life of our body. However, when the immune surveillance function is impaired, it may not be possible to effectively identify and remove cells that have undergone mutation or transformation into malignancy, and over time may lead to tumors.

"The novel coronavirus infection (COVID-19) can activate innate and adaptive immune responses, and an effective immune response helps to clear the virus, which is why about 85% of patients will show mild disease and heal more easily." Yang Dongliang said, but out of control inflammation reactions and impaired immune responses may cause local or systemic tissue damage, which can result in the virus not being effectively cleared, thereby making the disease severe.

Then why bats don’t get infected by the novel coronavirus (2019-nCoV)?

Based on current research, many scientists believe that the natural host of the new coronavirus comes from bats, but why do bats not get sick? What is the difference between its immune system and human immune system? "There is not yet a very affirmative answer to this question, but there are some clues that its immune system is an important factor for controlling the virus and avoiding the damage caused by the virus." A researcher said.

Bats are the only mammals that can fly. Virological studies have found that there are hundreds of pathogenic viruses in bats, but they are not pathogenic to bats or cause large numbers of deaths. First of all, the normal body temperature of a bat reaches 40 degrees Celsius, which means that its metabolic rate is very high, which is equivalent to our human beings having a high fever every day. High fever is an inflammatory reaction in the body. It can mobilize the immune system to defend or eliminate pathogens, but it also accelerates cell damage and aging, resulting in DNA damage. The bat does not develop tumors under such a high metabolic condition because it has a strong DNA repair mechanism.

Bats undergo high oxidative stress under high metabolic conditions. The NF-κB pathway associated with the inflammatory signaling pathway is particularly strong. This pathway plays an important role in the activation of the natural immune response in the human body. The bat is in a highly activated state in daily situations, so it is always in an activated state of natural immune response. At the same time, the activity of the inflammatory body of the bat is relatively low. This makes the bat with high metabolic, high DNA repair capacity, high natural immune response activation, and at the same time a low inflammation activity physiological state, so it not only inhibits virus reproduction, but also allows the body to survive, that is, coexist with the virus.

"This is the difference between the bat's immune system and the human immune system, and the basic mechanism that may cause bats to become a natural virus bank. Of course, this is just the understanding of current scientific research, and further research is needed."

The severity and emergency of SARS-CoV-2 infection spurs an urgent need for antiviral drug and vaccine discovery. Creative Biolabs has spent considerable efforts to provide scientific support and comprehensive services to promote the success of this combat. Equipped with cutting-edge techniques and vast experience, we are keeping up with current research hotspots and integrating all resources to guarantee high-quality services (including but not limiting to): Antiviral Drug Discovery, Vaccine Discovery, Preclinical Research, In Vitro Diagnostic (IVD) Immunoassays.

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