- Maria Teresa Tejedor Junco
- The Conversation*
What are viruses for? They certainly have a “bad name.”
But we must not analyze nature from an anthropocentric point of view.
Furthermore, 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 are remembering beneficial aspects.
For example, production of antibiotics (some molds and bacteria), foods such as yoghurt (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 on everything that viruses bring to our lives in a single article.
But let’s look at some examples.
1.- Treatment of 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 has been used successfully to treat this disease.
It attacks and kills cancer cells without affecting healthy ones.
There are also trials to use modified viruses in the treatment of other types of tumors: melanomas, glioblastomas.
Even to treat the cervical cancer, caused by another virus.
Among chronic diseases, the use of bacteriophages (viruses that attack bacteria) is being investigated for the treatment of cystic fibrosis and ulcerative colitis.
Some studies show that healthy people have a different phage composition in their gut than people with ulcerative colitis or Crohn’s disease, two serious intestinal disorders.
This could also be related to efficacy of stool transplantation.
The presence of an enteric virus appears 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 AIDS patients.
People who have that virus, related to hepatitis, but it does not produce any disease, they are not free from 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 available antibiotics.
These viruses are very specific.
They can attack pathogenic bacteria, without causing any effect on our “good” microbiome.
In 1919, D’Herelle already used phages to treat infections.
Currently, it is a very controlled type of treatment, and is only used in very serious infections 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.
Being effective against the most common pathogenic bacteria in each species, improve the health of animals.
They also contribute to decrease the use of antibiotics.
Food industries are especially interested in using phage against the main foodborne pathogenic bacteria.
They could even be used to disinfect production facilities.
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, they can affect beneficial insect species and be toxic to humans and other vertebrates.
An interesting alternative are 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 vertebrates.
What’s more, they 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.
To do this, the gene of interest is introduced into the virus, and then the insect is infected, turning it into a small “biofactory” that produces the proteins of interest.
Some 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 there are between 10²⁸ and 10³⁰ viruses in the oceans.
They are key components of marine ecosystems.
They can infect animals, algae, and marine plants or to other microorganisms.
The vast majority of these viruses are bacteriophages.
Some authors have calculated that viruses release 145 gigatons of carbon per year in tropical and subtropical oceans. Therefore, they are a fundamental part of the carbon cycle in ecosystems.
Furthermore, they are responsible for horizontal gene transfer in the 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 both copies of a gene.
This prevents them from synthesizing an enzyme essential for normal eye development.
By means of a modified adenovirus, a normal copy of the gene directly in the retina.
With a single injection, they regain their vision.
Viruses in general, not just marine viruses, are great generators of genetic diversity.
They tend to have a high mutation rate, tend to mix with each other, and can integrate (and disinsert) from their host genome.
They give bacteria the ability to resist certain antibiotics, or to produce toxins, which is good for them, but not for us.
Too there are viruses inserted into the genome of vertebrates, including humans.
They appear to be involved in gene regulation, and may contribute to the emergence of new functions.
Perhaps the most surprising thing about viruses is their role in the development of human life.
In it human genome there is 8% of viral DNA.
They are remnants of retroviruses that have been inserted into our DNA throughout human history.
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 ways in which viruses contribute to improve our existence.
Remember that only a small percentage of them can make it worse. Yes, drastically.
* María Teresa Tejedor Junco is Professor of Microbiology, University of Las Palmas de Gran Canaria.
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Eddie is an Australian news reporter with over 9 years in the industry and has published on Forbes and tech crunch.