Scientists in China successfully cured 24 mice of their eye condition, which was produced by a single, mutant copy of one gene. That demonstration, reported in the scientific literature two years ago, was billed as the first to show that it’s possible to correct a genetic disease using a genome editing tool, which scientists call CRISPR-Cas9. Although in mice, the findings offered the first proof of principle that scientists and doctors might one day have sufficient skill and precision to edit single-gene disorders out of human genomes in much the same way.
Jinsong Li, one of the leaders of the study from the Chinese Academy of Sciences, said then that he believes it is “absolutely possible to use CRISPR to cure genetic disease in the near future.” As further evidence in support of Li’s conclusion, his paper came out alongside another by researchers in the Netherlands. They had used CRISPR to correct a gene that causes cystic fibrosis in adult stem cells derived from patients with the single-gene disorder.
Early last year, scientists welcomed the first monkeys, a pair of twins, carrying mutations that had been specifically edited into their genomes using CRISPR. A few months later, scientists announced that they’d used CRISPR to correct a genetic condition by editing the liver cells of mice — the first time the procedure was shown to work in an adult animal.
In a perspective piece published in the New England Journal of Medicine this year, Eric Lander, director of the Broad Institute, envisioned other therapeutic futures for CRISPR. The molecular tool set could be used to treat a progressive and genetically encoded form of blindness by inactivating a mutant gene in light-sensitive cells of the retina; it could prevent heart attacks in patients with a condition that leads to extremely high cholesterol by editing a gene in the liver; or it could edit sickle cell disease or hemophilia right out of the bloodstream. The immune cells of patients with HIV might be edited to resist the infection by eliminating the “door” that allows the virus to enter their cells.
There are important caveats and concerns when it comes to therapeutic uses of CRISPR, so read on, but the possibilities are seemingly endless. In March, researchers at the Salk Institute revealed another way that CRISPR might beat HIV infections. When HIV finds its way into human cells, the virus stages a takeover, inserting itself into the genome to convert human cells into HIV factories that produce more and more of the virus. That, after all, is what viruses do. In many cases, our immune systems do a good job of recognizing infections and mounting attacks against them. Unfortunately, our immune cells aren’t well equipped to recognize and fight off HIV.
Hsin-Kai Liao and Juan Carlos Izpisua Belmonte wondered if they could program CRISPR to seek out and chop up those viruses even in the places where they can hide, safely embedded in the human genome. The Salk researchers presented evidence in Nature Communications that they could indeed use CRISPR against HIV in human cells. In healthy cells carrying their version of CRISPR, HIV couldn’t set up shop in the first place.