Scientists genetically 'edit' human blood stem cells

Harvard researchers have used a new gene-editing technique to create what could prove to be an effective method for blocking HIV from invading and destroying patients' immune systems.
This is the first published report of a group using CRISPR/Cas technology to efficiently and precisely edit clinically relevant genes out of cells collected directly from people, in this case human blood-forming stem cells and T-cells, researchers said.
The work was led by Chad Cowan and Derrick Rossi, associate professors in Harvard's Department of Stem Cell and Regenerative Biology (HSCRB).
HIV specifically targets T cells, a principal portion of the blood-based immune system, and enters via a gene receptor called CCR5 that serves as a doorway into the cells.

Once inside the T cells, HIV replicates and kills off the host cells, leaving patients at the mercy of a variety of opportunistic infections.
Using the CRISPR/Cas gene-editing technology, the researchers knocked the CCR5 receptor out of blood stem cells that they showed could give rise to differentiated blood cells that did not have CCR5.

In theory, such gene-edited stem cells could be introduced into HIV patients via bone marrow transplantation, the procedure used to transplant blood stem cells into leukemia patients, to give rise to HIV-resistant immune systems.
"We showed that you can knock out CCR5 very efficaciously, we showed that the cells are still functional, and we did very, very deep sequencing analysis to show that there were no unwanted mutations, so it appears to be safe," Cowan said.

Though the researchers believe that this new approach to HIV therapy might be ready for human safety trials in less than five years, they urge caution.
The work could run into unexpected complications and the history of the HIV/AIDS epidemic is littered with "cures" that turned out not to be, researchers said.
Even if this new approach works perfectly, it will require additional developments to be applicable in the areas of the world that have been the hardest hit by the epidemic, they said.