Trees are easier to cut than genes. But with both, in theory, a pandemic can be unleashed. Deforesting and destroying ecosystems We make it easier for animal pathogens to jump on humans. But it is also true that we can know in great detail the source code in which the entrails of new viruses are written. Your genes. And manipulate them.
In Lluis Montolius laboratory, at the CNB-CSIC, they have been tracking the revolutionary CRISPR genetic editing technique for years. A system that allows cut and paste pieces of the genome of a living being with enormous precision, and whose discovery we owe to the Spanish Francis Mojica.
They are now developing this tool to see if it can be useful in destroying the RNA strands of coronaviruses and, therefore, prevent SARS-CoV-2 from replicating in the body. It would be the first time that such a drug is developed. Basically using the smallest scissors in the universe.
Lets start with one of the most common applications of CRISPR: making custom animals and plants. It has been done for about four years relatively regularly in research laboratories.
Mouse | Pests Mice Rats (CC-BY)
Despite the fact that the technique became world famous for the daring of Dr. He Jiankui, in 2018, to manufacture three children edited using this technique something completely illegal CRISPR is useful to make animal models.
The mouse is the classic animal model with which to experiment from antiviral drugs to vaccines. In the case of SARS-CoV-2, Mice are not infectious because they lack the ACE2 receptor that allows the virus to enter cells.
CRISPR is the technique by which, illegally, three Chinese babies were genetically edited to avoid developing AIDS. But it is common in other everyday laboratory uses.
So there are already several laboratories that are developing humanized mice with CRISPR. Human genes or parts thereof are cut and pasted into the genome of a future rodent, almost before it is an embryo.
The mouse that is born will already be able to have those receptors typical of humans (and some other animals) so that, at that level, they look a bit more similar. The next step is to no longer infect the mice. But cure them.
The coronavirus genome is RNA, explains Montoliu. If we have a CAS protein that we can program to cut RNA, why dont we target it to cut the coronavirus genome? And we are directly attacking the heart, the genetic material of that coronavirus, explains the researcher.
The CNB-CSIC researcher Lluis Montoliu | M. Vicious
When he talks about CAS protein, he means those tiny molecular scissors. There are different types. There are real motorized clippers, called CAS9, that can cut the double strand of DNA. So they are as promising as they are disputed: they work on humans.
For an RNA virus (the chain is simple) a manual scissor pruner is enough, to continue with the metaphor. This is where CAS13a or CAS13d enter. They work (thanks to some guides) no matter what strain, variant, or mutant. Interesting, in case the coronavirus begins to change more than it seems, as it happens with the influenza virus.
The small drawback of these scissors (the CAS13a we have hardly known since 2016) is that once they cut the virus, they can be bundled to cut the rest of the cell. When Dr. Feng Zhang (BROAD / MIT), its inventor tested CAS13a for the first time, he saw that it was doing its job well but immediately freaked out and started cutting, unspecifically, the rest of the RNA in that test tube.
Fortunately, the protein has become more sophisticated so that, already with variant 13d, we have a very specific tool, because the cell has its own RNA and we do not have to touch those, they are useful for it to function.
It also wont enter the nucleus of the human cell (DNA) because CAS13d doesnt need it. That would be as risky as driving the chainsaw into the heart of a hedge. There is a risk of cutting it down.
CAS9, used to edit girls from a tomato, is like that chainsaw, hence the delicacy and prematureness of this technique for editing people. The mess of the cellular patchwork that can be mounted is important, until the gluing technique is fine-tuned, although it shows promise. That is, we are controlling the grafting technique, to continue with the garden comparison.
Regarding the coronavirus, this does not mean that we already have a ready-to-use medicine from these CRISPR scissors. First you will have to check if they work In zebrafish embryos, that we will try Seville, where we will deliver together with CAS13 a guide that tells you where you have to cut .
Then it will be tested in laboratory cells infected with other cousin viruses to avoid risks and we will get their cutting patterns. Hence, yes, in the SARS-CoV-2.
Sure we could start doing the experiment on mice, but its very important that lets go step by step Montoliu warns. At least, with the certainty that the method works in cells outside a living being
The project has received 75,000 euros of financing from donations from companies and individuals. When we have verified that it works in cells, we will test it in mice (also edited), after this year. If we see (this year) that we can degrade SARS-CoV-2 in crops it would already be a success.
In April, after theoretical proposals in this regard, researchers from Stanford and Duke universities developed a curative scissors of this type, experimentally viable in human lung cells. They named it PACMAN (Comecocos). Will it work outside the lab loft?
CAS scissors can cut viruses. And if they do, it is because they detect them, so it is possible to use them to do tests, in theory.
Although, to date, the most reliable method to detect the active virus in a person is RT-PCR, exist other genetic screening approaches which have not yet been shown to work, but which are promising. This is the case of this possible pocket PCR, in which Margarita Salas Luis Blancos patent partner works.
The CRISPR genetic cutter can also aid in the detection of coronaviruses. In classic PCR methods and that of Blancos team, the virus is evident because it literally shines in the laboratory. With CRISPR it is possible to shine each cut that scissors, CAS12 in this case, they hit the gene molecule.
There are several methods to experiment with, under the acronyms SHERLOCK and CARMEN. The interesting thing about these technologies is that, combined, they can perform hundreds of tests simultaneously. And not only for detecting SARS-CoV-2, but for 120 different viruses.
CARMEN Test Plate | Michel James, MIT
These are some of the applications of genetic engineering to destroy viruses or to immunize ourselves against them, since there are several biotechnological approaches in the race for the COVID-19 vaccine that involve the manipulation of genes (of the virus, in this case).
Cut. Paste. And create new viruses. Again, and in the sense of some conspiracy theories, We do have the methodology to (rather than destroy) make viruses, but we dont have the intellectual capacity , responds the head of the virology laboratory at Cambridge University Nerea Irigoyen.
There is methodology, not capacity, to create a laboratory virus, but SARS-CoV-2 is far from being the perfect pandemic virus.
He remembers comments on social networks in which he was told that viruses mutate in laboratories. Indeed, Ive been doing it for many years. But it is one thing to do it and quite another to make a perfect pandemic virus. This is not it. We could still do much better so that it could infect more cell types.
70% of human infectious diseases come from viruses, bacteria, or animal parasites. It has always happened. Flu, Ebola, SARS-1, MERS Why dont we accept the normal?, Concludes the scientist.
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Cut and paste: the true genetic engineering of the coronavirus - Explica