Modest, but the result
Chinese scientists have tried to cure a patient of HIV using CRISPR technology
Evgenia Efimova, Vesti
Researchers from Peking University have used CRISPR genome editing technology for the first time to treat an adult patient with human immunodeficiency virus (HIV). This method did not help to rid the subject's body of a dangerous virus; nevertheless, scientists call the results successful.
As the head of the study, Professor Hongkui Deng, explains, the cure of two HIV-infected patients from Berlin and London inspired his team to conduct their own experiment.
Recall that Timothy Ray Brown became known in 2008 as the "Berlin patient", the first person cured of HIV. In 2007, he underwent a bone marrow transplant as part of the treatment of another dangerous condition - leukemia. At the same time, the bone marrow donor had a mutation in a gene called CCR5, which gives the carrier a kind of immunity to HIV.
This gene determines the work of a receptor on the surface of white blood cells, which the dangerous virus uses as a "port" for introduction into cells. But in people with a mutation in both copies of the CCR5 gene, this receptor is deformed, as a result of which certain HIV strains cannot penetrate the cells.
After the bone marrow transplant, Brown showed no signs of HIV in his blood.
Some time later, another patient, from London, was also able to recover from HIV in a similar way (and there is a third, from Dusseldorf – VM).
But both of these stories of salvation are accompanied by one "but": it is difficult to find a bone marrow donor with such a rare mutation (only a small percentage of people in the world have such a gift of nature).
Chinese scientists have suggested that edited donor cells will help achieve the same effect.
An HIV-infected man from China took part in the experiment. At the age of 27, he was also diagnosed with leukemia, as a result of which, as in previous similar cases, he needed a bone marrow transplant.
Using CRISPR technology, the researchers removed the CCR5 gene from the donor's bone marrow stem cells and then transplanted them into the patient's body. However, the breakthrough technique does not yet give a 100% result, and in the end, the researchers were able to use it to edit only 17.8% of the donor's stem cells.
Then they monitored the patient's condition for 19 months.
By the end of the observation period, CRISPR-edited table cells were still present in the male body, but they accounted for 5-8% of the total number of recipient stem cells. In other words, slightly more than half of the edited cells died after the procedure. However, the patient began a complete remission of leukemia a month after transplantation.
When the patient briefly stopped taking HIV medications, the viral load (the number of virus particles per unit volume of blood) in his body increased. He had to go back to medication again. In other words, the experiment did not help cure the man of infection, although it saved him from cancer.
"I'm not surprised that 5% [of the edited cells] turned out to be insufficient to reduce the viral load. But now we know that CRISPR-edited cells can be preserved and that we need to get a result of more than 5%," said Fyodor Urnov, a biologist at the University of California at Berkeley. He was not involved in this work.
Equally important is the fact that the researchers did not notice any side (non-target) mutations as a result of using CRISPR technology. And they sometimes arise.
According to the head of the current work, the effectiveness of such therapy can be improved by working with induced pluripotent stem cells – an indispensable tool for physicians and biologists.
Recall that pluripotency is the ability of a stem cell to develop into a cell of any organ and tissue. The word "induced" means that stem cells were forced to become such: they were obtained by "reprogramming" ordinary somatic cells.
CRISPR can inactivate the CCR5 gene in these cells, then specialists will be able to convert them into blood stem cells that are used for bone marrow transplantation. Such a strategy will help to create a larger number of necessary donor cells, Professor Dan believes.
In general, the researchers consider this work an important step towards the use of genome editing technology for human treatment.
The results of the work are presented in The New England Journal of Medicine (Xu et al., CRISPR-Edited Stem Cells in a Patient with HIV and Acute Lymphocytic Leukemia).
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