What are viruses for? Certainly, they have a “bad reputation”.
But we should not analyze nature from an anthropocentric point of view.
Moreover, on many occasions we do not have enough knowledge to assess the role played by certain elements (living or inanimate) in an ecosystem.
In general, when we think of microorganisms, the first thing that comes to mind are diseases.
Then, little by little we remember beneficial aspects.
For example, production of antibiotics (some molds and bacteria), foods like yogurt (bacteria) or drinks like beer (yeasts).
And viruses, what are they for? It seems that only to cause disease … Or not? Do we have viruses in our body even though we are not sick?
It is not possible to comment in a single article all that viruses contribute to our lives.
But let’s see some examples.
1.- Treatment cancer and other pathologies
Retinoblastoma is a type of eye cancer that mainly affects children.
It can cause blindness and, if it does not respond to treatment, the eyes must be removed so that it does not spread to the whole body.
A genetically modified adenovirus is It has been used successfully for the treatment of this disease.
It attacks and kills cancer cells without affecting healthy cells.
There are also trials to use modified viruses in the treatment of other types of tumors: melanomas, glioblastomas.
Even for treat cervical cancer , caused by another virus.
Among chronic diseases, the use of bacteriophages (viruses that attack bacteria) for the treatment of cystic fibrosis and ulcerative colitis .
Some studies show that healthy people have a phage composition in your gut differently than people with ulcerative colitis or Crohn’s disease, two serious intestinal disorders.
This could also be related to the efficacy of stool transplantation.
The presence of an enteric virus seems to offset the beneficial function of the gut microbiome in mice.
There is even a virus, called GBV-C, that contributes to improve the prognosis of diseases We are from AIDS.
People who have this virus, related to hepatitis, but not produces any disease, they are not free of AIDS.
However, they have fewer symptoms and mortality in this group is lower.
2.- Alternative to antibiotics to treat serious infections
Phage therapy is the use of bacteriophages to treat serious infections.
It is an alternative to the use of antibiotics, especially in those infections in which the bacteria are resistant to most of the available antibiotics.
These viruses are very specific.
They can attack pathogenic bacteria, without causing any effect on our “good” microbiome.
In 1919, D’Herelle has already used phages to treat infections.
Currently, it is a very controlled type of treatment, and is only used in infections very serious and when there are no other options.
On the other hand, they could be an alternative to the use of antibiotics , thus reducing the selective pressure and the appearance of resistance.
3. – Contribute to food security
Several companies are working on the development of “phage cocktails” to administer to farm animals.
As they are effective against the most common pathogenic bacteria in each species, improve the health of animals.
They also contribute to reduce the use of antibiotics.
Food industries are especially interested in using phages against the main pathogenic bacteria transmitted by food.
They could even be used to disinfect facilities from production.
Its use is also proposed to fight against microorganisms that alter food.
4.– Viruses as bioinsecticides
Chemical insecticides have several disadvantages.
On the one hand, they generate resistance .
On the other hand, they can affect beneficial insect species and be toxic to humans and other vertebrates.
An interesting alternative is microbial insecticides . Among them, those that use viruses.
Baculoviruses have the great advantage of being highly specific for specific species of insects.
They are not pathogenic for plants or for vertebrates.
In addition, do not affect other species of insects.
They form a protein capsule that protects them from the environment.
They infect the cells of the midgut of the parasitic organism, and pass directly to the hemolymph, causing the death of the insect causing the plague.
5. – Manufacture of vaccines
In addition to being bioinsecticides, Baculoviruses are also used to make vaccines.
For this, the gene of interest is introduced into the virus, and then the insect is infected, turning it into a small “biofactory What produ The proteins of interest.
Some of the most promising vaccines against SARS-CoV-2 use adenovirus .
They have also been used to make vaccines against Ebola or Zika.
A multipurpose vaccine has been created, against avian plague and Newcastle disease, using a recombinant virus.
6. – Marine viruses and their role in nature
It is estimated that in the oceans there are between 10 ²⁸ and 10 ³⁰ virus.
They are composed Key elements of marine ecosystems.
May infect marine animals, algae and plants or other microorganisms.
The vast majority of these viruses are bacteriophages.
Some authors have calculated that viruses release 145 gigatons of carbon per year in the tropical and subtropical oceans. Therefore, they are a fundamental part of the carbon cycle in ecosystems .
In addition, they are responsible for horizontal gene transfer in ecosystems. oceans.
7. – Other benefits of viruses
In 2017 an adenovirus-based gene therapy was approved in the US to treat a rare inherited disease that causes blindness.
Patients have a mutation in the two copies of a gene.
This prevents them from synthesizing an enzyme essential for the normal development of the eye.
By means of a modified adenovirus, a normal copy of the gene directly in the retina.
With a single injection, they regain vision.
Viruses in Generally, not only the marine ones, they are great genera generators of genetic diversity.
They tend to have a high mutation rate, tend to mix with each other and can be integrated (and disinserted) from the genome of their host.
They give bacteria the ability to resist certain antibiotics, or to produce toxins, which is good for them, but not for us.
There are also viruses inserted into the genome of vertebrates, including humans.
They seem to be involved in gene regulation, and may contribute to the appearance of new functions.
Perhaps the most surprising thing about viruses is their role in the development of human life.
In the human genome there is an 8 % of viral DNA.
They are remnants of retroviruses that have been inserted into our DNA throughout the histor ia of humanity.
Until recently it was considered “junk DNA”.
However, several studies have shown its importance.
That viral DNA encodes a protein, syncytin, which is essential for the formation of the placenta, the organ that allows the exchange of substances between the mother’s blood and that of the fetus.
There are many more aspects in which viruses contribute to improve our existence.
Let’s remember that only a small percentage of them can make it worse. Of course, drastically.
María Teresa Tejedor Junco is a teacher Head of Microbiology, University of Las Palmas de Gran Canaria.
This article was originally published on The Conversation.
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