There are more viruses than stars in the universe. To get an idea of how many there are, whoever is reading this article is sitting on over 800 million viruses.
These tiny infectious agents have been with us long before we emerged as a species. And the debate over their appearance on Earth is ongoing: are they older than bacteria, or are they halfway between them and eukaryotic cells?
We don’t know yet, but what we do know is that they’ve been on everyone’s lips for the past two years. It’s virtually impossible to turn on the TV, read the newspaper, or walk into a bar without hearing the word “virus.”
Virus converted into therapy
Viruses are very diverse and can infect human cells, bacteria, and even plants, creating endless diseases. Who hasn’t caught a cold or the flu and had to spend a few days stuck in bed?
The history of viruses ran parallel to the history of the development of modern medicine. So much so that nothing has sparked such a massive global and unified effort as protecting against them: vaccines.
We have also reached another viral milestone in our recent history. Thanks to science, we have been able to turn the tables and turn what is a priori an evil agent into its nemesis: a drug.
There are diseases that are caused by errors in the genome, including certain types of cancer. These errors or mutations render a gene inoperable in cells, preventing it from doing its job and creating various problems culminating in pathology.
Gene therapy is responsible for treating this type of disease. The idea behind this therapeutic strategy is quite simple: if a gene’s function is disabled, why not bring a copy of the good, functional gene into the cells? This allowed them to recover and continue to fulfill their mission.
The question is how to do it. The first obstacle we encounter on our journey to the nucleus, where genetic information is stored, is the plasma membrane, a covering that contains and protects all cell components.
In order to cross them without damaging our gene, lipid vesicles can be used, which are naturally integrated into the membrane and release their contents inwards. Another possibility is to use electrical discharges that create transient pores on the cell surface.
But wouldn’t it be much cheaper to use a mechanism that already exists in nature? One that does just that: introduce genetic material into human cells? We are of course referring to viruses.
Viruses as vehicles
Viruses are able to infect human cells and insert their genome into them. They use the host cell’s own machinery to replicate in order to be able to infect neighboring cells and expand until the body’s immune system can eliminate this new strain of virus.
Thanks to advances in genetic engineering, scientists have been able to alter the genome of viruses and clip their wings. That is, transform them so that they can infect but not replicate.
And not only that, it was also possible for these drugs to carry the desired gene without waking up the immune system and causing side effects. In this way it was achieved that they perform the functions of a taxi, train or bus transporting passengers (medicines) to the destination of your choice.
Retinal dystrophy and butterfly children
These advances make it possible to treat previously incurable diseases, such as hereditary retinal dystrophy, which causes vision loss in children and adults due to mutations in the RPE65 gene. By injection, the modified virus, which contains a functional copy of this gene, goes to the cells of the retina, infects them and deposits the effective copy inside them.
Another recent example is clinical trials to treat a number of open sores that appear all over the body of so-called butterfly children. These patients lack the gene for collagen VII, and thanks to the modified herpes simplex virus type I, the functional gene can be transported into skin cells, closing open wounds for years.
The diseases that can be treated with gene therapy can currently be counted on the fingers of one hand. However, it takes many fingers to count the number of clinical trials that are being conducted in hopes that one day these therapies may reach hospital wards.
The immune response to the treatment itself, the specificity of the drug, and its administration are the major challenges hampering the progress of these studies and the gene therapy approach to patients.
The ingenious idea of converting one pathogen into another that cures it has managed to make organs that had forgotten how to work functional again. It has given hope and improved the lives of patients with limited therapeutic options.
With time, effort and financial investment, this picaresque inherent in science will help solve various diseases.
This article was a finalist in the II edition of the Youth Disclosure Contest organized by the Lilly Foundation and The Conversation Spain.