Faster, better, cheaper
CRISPR tests will help diagnose dangerous diseases
Yulia Vorobyova, "Vesti" based on the materials of Nature
Diagnosis of most viral infections today requires the use of specialized tests, sophisticated equipment and sufficient electricity. All these resources are limited in developing countries, and outbreaks of the most dangerous diseases most often occur in them.
Researchers around the world are actively exploring the potential of CRISPR technology, including diagnostic. According to recent research, tests based on this technique can be simple, fast and effective. And most importantly, they do not require resources in which the health care of third world countries is limited.
So, scientists from Nigeria are testing a new diagnostic tool for detecting Lassa fever. In 2019 alone, the disease claimed dozens of lives in this country, and forecasts regarding the spread of infection are disappointing.
Meanwhile, experts from the United States and Honduras are checking how well the CRISPR tool detects other viruses – pathogens of dengue fever, Zika fever, as well as human papillomaviruses associated with the development of cancer. And their colleagues from the Democratic Republic of the Congo hope to use a new diagnostic strategy to detect the Ebola virus.
Let's explain that the innovative technique in question is based on CRISPR's ability to track down specific genetic fragments of a particular virus or strain. For example, in the case of Lassa fever, this is the RNA of the corresponding virus, Lassa mammarenavirus.
It is important to note that in this case, the Cas9 enzyme, which has been glorified by many works, is not used, but its "brother" – Cas13. The latter works at the level of RNA, not DNA (and in many viruses, it is the RNA molecule that is the carrier of genetic information).
Having discovered the genetic sequence that is the target, the Cas13 enzyme cuts it, and then begins to "chop" all the RNA molecules around indiscriminately. Such "behavior" is harmful when editing genes, but it is perfectly suitable for diagnosis, because the corresponding changes will be a good signal for doctors.
The principle of operation of Cas13 served as the basis for a new diagnostic tool called SHERLOCK, about which the authors of the project "Vesti.Science" (nauka.vesti.ru ) they told me in detail. Back in 2017, the test proved its effectiveness when working with samples of urine, saliva and blood of patients.
It is worth noting that initially, scientists added a special RNA to the detection system, which, when destroyed by an enzyme, begins to glow. Now they have improved the technique by adding RNA molecules that signal that they have been cut by the Cas13 nuclease in a slightly different way. They trigger the formation of a dark stripe on a piece of paper, and this serves as a signal to doctors that CRISPR has found its target. Such an analysis resembles a regular pregnancy test conducted at home.
Currently, researchers from Nigeria are testing the effectiveness of a new test. They use it on samples obtained from patients who have already been diagnosed with Lassa fever using a widely used laboratory method – polymerase chain reaction (PCR).
We should immediately note that this technique loses to the SHERLOCK test in many ways. The latter is cheaper and takes half as much time (two hours versus four in the case of PCR). Both methods require electricity costs at the processing stage of the obtained samples, but SHERLOCK is not as sensitive to power outages as PCR.
Other CRISPR tests developed by scientists use other Cas enzymes with different properties. For example, to detect the human papillomavirus, the Cas12a protein is used, which, like Cas13, "splits" its target, but works with DNA, not RNA.
In addition, two more candidates look promising – Cas14 and CasX proteins. The latter, by the way, also claims to be the new "editor-in-chief" of genes.
If the new approaches demonstrate their effectiveness, they can help in the early detection of a wide range of viral infections. This will help to avoid outbreaks of dangerous diseases and save the lives of many people.
However, doctors in developing countries are afraid of economic obstacles. But the developers of innovative technologies promise to license their tools as quickly as possible and make them available to the health systems of even the poorest countries.CRISPR tests will help diagnose dangerous diseases.
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