A simple error in a gene triggers deadly diseases, but correcting it is possible thanks to viruses. A virus? It’s like that. Science has achieved the unimaginable: turning a pathogen into a medicine
There are more viruses than stars in the universe. To get an idea of their huge numbers, anyone reading this article will be sitting on over 800 million viruses.
These tiny infectious agents were with us long before we emerged as a species. And the debate on their appearance on Earth is not yet closed: do they predate bacteria, or are they halfway between them and eukaryotic cells?
We don’t know yet, but what we do know is that for the past two years they have been on everyone’s lips. It is virtually impossible to turn on the television, read the newspaper or walk into a bar without hearing the word “virus”.
Viruses converted into therapy
Viruses are very different from each other and can infect both human cells and bacteria and even plants, generating endless diseases. Who hasn’t caught a cold or the flu and had to spend a few days without leaving their bed?
The history of viruses parallels the history of the development of modern medicine. So much so that nothing has sparked global and unitary efforts as massive as that of obtaining protection against them: vaccines.
Also, in our recent history, we have reached a new milestone regarding viruses. Thanks to science, we were able to turn the tide and transform what was a priori an evil agent into its sworn enemy: a drug.
genetical therapy
There are diseases caused by errors in the genome, including certain cancers. These errors or mutations cause a gene to cease to be functional within cells, prevent it from performing its job and generate various problems that lead to pathology.
Gene therapy is responsible for the treatment of this type of disease. The idea behind this therapeutic strategy is quite simple: if the function of a gene has been abolished, why not transport a copy of the good working gene into the cells? This way they could recover and continue to fulfill their mission.
The question is how to do it. The first obstacle we encounter on our journey to the cell nucleus, where genetic information is stored, is the plasma membrane, an envelope that holds and protects all cellular components.
To cross it without our gene being damaged, we can use lipid vesicles which, by their nature, integrate into the membrane, releasing their contents inwards. Another possibility is to use electrical discharges which generate transient pores on the surface of the cell.
However, wouldn’t it be much cheaper to take advantage of a mechanism that already exists in nature? One that does just that: introduce genetic material into human cells? We refer, of course, to viruses.
Viruses as a vehicle
Viruses are able to infect human cells and introduce their genome into them. They use the host cell’s own machinery to replicate and thus be able to infect neighboring cells, growing until the body’s immune system is able to eliminate this new viral strain.
Thanks to advances in genetic engineering, scientists have been able to modify the genome of viruses and clip their wings. In other words, transform them so that they can infect but not replicate.
And not only that, but it has also been possible for these agents to carry within them the gene that one wants, without waking up the immune system and generating adverse reactions. This is how it was realized that they perform the functions of a taxi, train or bus transporting passengers (pharmaceuticals) to the destination of your choice.
Retinal dystrophy and butterfly children
Thanks to these advances, previously incurable diseases can be treated, such as hereditary retinal dystrophy, which causes vision loss in children and adults due to mutations in the RPE65 gene. Through an injection, the modified virus that contains a functional copy of this gene will travel to the cells of the retina, infect them and deposit the effective copy there.
Another very recent example is ongoing clinical trials to treat a series of open sores appearing all over the bodies of so-called butterfly children. These patients lack the collagen VII gene, and with the modified herpes simplex virus type I, the functional gene can be transported to skin cells, causing wounds that have been open for years to close.
Currently, the diseases that can be treated by gene therapy can be counted on the fingers of one hand. However, we need many fingers to count the number of clinical trials that are being conducted in hopes that one day these therapies might reach hospital wards.
The immune response to the treatment itself, the specificity of the drug and its delivery are the main challenges that hinder the progress of these trials and the approach of gene therapy to patients.
The ingenious idea of turning one pathogen into another that cures them has managed to restore function to organs that had forgotten how to function. She gave hope to patients whose therapeutic options were rare and succeeded in improving their living conditions.
With time, effort and financial investment, this picaresque inherent in science will help solve various diseases.
This article was published in ‘The conversation‘.