Researchers at Sangamo BioSciences and the Abramson Family Cancer Research Institute have built a custom-designed enzyme that can make T cells (a type of immune cell) resistant to HIV by disabling (cutting the gene to make it nonfunctional) the T cell gene CCR5.

The technique could allow scientists to design enzymes that bind to the genome at any chosen spot and cut or correct sequences involved in other diseases.

HIV normally latches onto the protein made by CCR5 to infect T cells. (People with a natural CCR5 mutation that keeps T cells from having CCR5 protein receptors on the cells’ surface appear to be immune to the disease.)

The researchers combined a DNA-severing enzyme with “zinc-finger proteins”–segments of protein that recognize and bind to specific sequences of three chemical letters within DNA. To ensure the enzyme would bind to only one spot on CCR5, they added multiple zinc-finger proteins to the enzyme. (If the designer enzyme were to bind and cut DNA in other sites in the genome, it could introduce catastrophic mutations.)

Unlike other methods to block the binding of HIV to CCR5, the zinc-finger approach makes a permanent change to the CCR5 gene, creating a pool of HIV-resistant cells.

See Also Zinc finger proteins put personalized HIV therapy within reach and Gene targeting raises cure hopes