Viruses: There are trillions of viruses in our bodies, but we are still alive leisurely

Millions of viruses are circulating in your body. We try our best to avoid viral infections, but what if certain viruses are vital to our body functions?

You may have heard of the human microbiome, which is a collection of microorganisms such as bacteria and fungi that share our bodies, including the skin and gut microbiome. But what do you know about the “virus group”? It is the sum of all viruses in our body. It exists in every tissue from the blood to the brain, even interwoven into the genetic code within the cell.

Viruses are the most numerous creatures on earth. It is believed that the number of bacterial cells in our body is roughly the same as that of human cells (about 37 trillion), but the number of virus particles may be at least 10 times that of it. Many of these viruses are related to the basic processes of the human body and form part of our internal ecosystem. It is safe to say that if they all disappear, we will not survive for a long time.

However, we still have a long way to go, we get close to knowing most of these viruses to do completely, or in fact what even most people do. It is estimated that so far, the field of virology has only explored about 1% of the viral diversity that exists.

Most viruses are still undiscovered and are called “viral dark matter” by some scientists. Nevertheless, they still appear in all parts of our body. A study published in June 2020 by Dr. Kei Sato of the University of Tokyo found viruses in human tissues including the brain, blood, kidneys and liver.

Sato’s research team hopes to conduct quantitative research on these viruses to create a virus “map” of human tissues. They do this by cross-referencing RNA sequence data with existing viral genome libraries, but this means that they can only explain the few well-known viruses that already exist in those libraries.

Sato said that this means that there is currently a bias to find most harmful known viruses, that is, “pathogenic” viruses. He explained: “In addition to the biases in our genetic reference library, it is difficult to collect samples from healthy tissues other than the intestine, which means that we may lose many harmless or even potentially beneficial viruses.”

It is easy to think of viruses as malicious foreign invaders. After contacting the surface of human cells, the virus injects its DNA or RNA code, hijacking the cell’s machinery, effectively turning it into a factory for the production of new viruses.

If you now picture a virus, you might imagine their spaceship-like protein shells, called “capsids,” which are used to transport themselves between cells. You may see SARS-CoV-2, the coronavirus that causes the COVID-19 pandemic, with its “corona” spikes covering the surface of the capsid.

However, the virus is not as strange as it seems.

The term “virus” actually describes entities with different properties. As Professor Frederick Bushman, a world expert on the human microbiome at the University of Pennsylvania, put it: “Sometimes, what we say about world things actually doesn’t match what is said there.

For example, viruses can spread through a very wide range of mechanisms. For some so-called endogenous retroviruses, the viral DNA is directly integrated between human cells because they are integrated into the chromosomes. In fact, 8% of our human genome is composed of these endogenous retroviruses.

COVID-19 virus

Only a small part (less than 2%) of our DNA encodes the process of directly producing protein molecules (in a process called transcription). Biologists once thought the rest was non-functional, and some even called it “junk DNA”‘. Now, much of this DNA is thought to have been obtained from previous viral insertions, and we have found that it is very important for regulating the transcription of other genes.

Certain viral genes do occur in regions of human DNA that produce essential proteins. In the history of evolution, these genes have been selected as essential functions of the human body, so it is not clear whether we should call them human or viral genes.

The gene used in the development of the human placenta is borrowed from an endogenous retrovirus, in which it first evolved to make a protein that fuse host cells together. In our evolutionary history, the process of gene collection from the tree of life seems to have happened many times. It has been proposed that, of our 20,000 genes, approximately 145 come from this horizontal gene transfer.

By transferring genetic molecules between different species in this way, the virus effectively binds the evolutionary tree together to form a tangled network.

However, viruses are usually adversely affected because the widely publicized viruses have harmful effects and can cause diseases such as AIDS, Ebola, chickenpox, and of course COVID-19. In fact, we know very little about how most viruses affect humans.

There may be more than 320,000 different viruses infecting the mammals there, many of which are harmless, and some can actually benefit us.

For example, certain viruses called bacteriophages attack the bacteria in our body and therefore play a vital role in regulating our microbiome. Just as invasive wild animal species enter a new area without predators or pathogens (cane toads in Australia or mice on tropical islands), their reproduction will get out of control. Similarly, without these regulatory mechanisms, bacteria will surpass ours. body.

Viruses also seem to be important in regulating our immune system. In humans, hepatitis G virus can prevent HIV, while in mice, herpes virus can reduce autoimmune diseases. These diseases are the main factors in many modern human diseases (from asthma to irritable bowel syndrome).

Therefore, many researchers suspect that even with the identity and role of a particular virus, the virus also plays an important role in maintaining human “immune modulation” (that is, a healthy immune system can respond to insufficient or insufficient pathogens). Little known.

These are not to deny the harmful effects of certain viruses and the destructive personal effects they may have on people’s lives. Obviously, many viruses are very harmful to us, and humans have developed mechanisms to resist their attacks. Bushman’s research team showed in April 2020 that breastfeeding can reduce the incidence of potentially pathogenic viruses growing on human cells in the baby’s intestines.

On the whole, the human virus is neither “good” nor “bad”. It is only an ancient part of us. Viruses have a profound evolutionary relationship with animals and plants. Every cell in your body is part of an uninterrupted life chain, which has been extended for more than 3.8 billion years. From the beginning, viruses have been an important part of evolutionary waltz.

The more we know about viruses, the more we understand that some aspects are essential to healthy living. Therefore, we can foresee how we will conceive of the virus revolution.

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