For the first time a person infected with HIV, the virus that causes aids, has been try to with the technology of editing of genes CRISPR to treat of treating a person infected with HIV. And, although it has not achieved the healing of the person, it is an important step toward the use of the edition of genes to treat human diseases, says Fyodor Urnov, a biologist at the University of California-Berkeley (U.S.) in a report published by the group " Nature ". "Thanks to this study, since we know that cells edited genetically can survive in a patient, and will remain there".
Scientists from the University of Beijing in Beijing (China) engineered human stem cells to mimic a rare form of natural immunity to the virus and transplanted into a person with HIV and cancer of the blood. Cells edited genetically survived in the body of the man for more than a year without causing side effects detectable, but the amount of cells was not high enough to significantly reduce the amount of HIV in your blood. The study was published this week in "The New England Journal of Medicine".
The research was inspired by a bone marrow transplant that cured in 2007, Timothy Ray Brown, more than a decade ago. Brown, initially known as "the Berlin patient", underwent a bone marrow transplant to treat his leukemia. However, the bone marrow donor was special because I had a version of the gene CCR5 that confers immunity to HIV.
Normally, the gene encodes a receptor on the surface of white blood cells that the HIV virus uses to infiltrate the cell.
But in people with two copies of the CCR5 mutation, this receiver is deformed and it blocks certain strains of HIV that do not enter into the cells . The version of the gene resistant to HIV is exceptionally rare: found in only 1% of people of european descent and is virtually absent in other ethnic groups.
The doctors hoped the bone marrow transplant will replace the blood cells susceptible to HIV infection of Brown with the immune, and so it was. After almost 13 years, there are no signs of HIV in his blood, and his leukemia is in remission. In march, researchers reported that a second person was subjected to a similar procedure in Britain and he was cured.
The group of Deng wanted to use gene-editing CRISPR to engineer blood stem cell HIV-resistant donors to normal, making this potential cure is more accessibleThe group of Deng wanted to use gene-editing CRISPR to engineer blood stem cell HIV-resistant donors to normal, making this potential cure is more accessible. The researchers tested this approach in a man of 27 years old in China who had been diagnosed with HIV and leukemia, and needed a bone marrow transplant. The scientists extracted stem cells from the bone marrow of a donor and used CRISPR-Cas9 to turn them into mutant CCR5.
at The beginning, the researchers were not able to get CRISPR to eliminate CCR5 in stem cells. " I Thought that these cells were truly resistant , " says Deng. Finally, they were able to edit the 17.8% of the donor stem cells.
This was the first test, so that the most important thing was to test the seguridadLa edition of genes, CRISPR in people remains controversial, in part because many researchers are concerned about its side effectsTo maximize the possibility that the transplantation were in the first place the cancer patient, the researchers mixed the stem cells edited with non-edited. The team monitored the man after the transplant to see if the cells are edited would survive and replicarían, if used to treat HIV infection and, most importantly, if the treatment was safe. "This was the first test, so that the most important thing was to test the security," says Deng.
Timothy Ray Brown, the first people cured of HIV - a Filegene-editing CRISPR in people remains controversial, in part because many researchers are concerned about its side effects. Studies have shown that CRISPR sometimes creates mutations are not desired in the laboratory, and the consequences of that happening in one person could be disastrous.
After 19 months, the stem cells edited with CRISPR persisted, although they only represented between 5 and 8% of the total number of stem cells of the receiver.
This means that a little over half of the cells edited died after being transplanted . And though the leukemia of the man is in remission, is still infected with HIV.
"I'm Not surprised that the 5% was not enough to reduce the viral load -says Urnov, but now we know that cells edited with CRISPR can persist and that we need to do better than the 5%".
For Deng, what's more important is that the patient does not suffer any secondary effect caused by the cells produced by genes. And when the researchers sequenced the genomes of those cells, they found evidence of genetic changes involuntary.
we Now know that cells are edited with CRISPR can persist and that we need to do better than the 5%"this is good news for the field," says Carl June, an immunologist at the University of Pennsylvania in Philadelphia. "We now know that, in principle, we can use CRISPR to edit human stem cells, which can persist in a patient and can be safe."
June said that this proof of concept opens the door to the research to test this technology for the treatment of other diseases of the blood, such as sickle cell anemia. He also points out that this study complied with the protocols ethical standard, including obtaining the informed consent of the participant.
Each time that CRISPR performs cuts in the genome, there is the possibility that something will go maimprovements in the technology of editing of genes means that researchers can now edit the stem cells with an efficiency greater than the success rate of 17.8% from the last study. But that carries risks. Each time that CRISPR performs cuts in the genome, there is the possibility that something will go wrong. Edit cells more efficiently means doing more cuts and it creates more opportunities for errors.
"This document is a success incomplete, and represents a motivation to continue moving forward," concludes Urnov.
Date Of Update: 13 September 2019, 21:00
