There has been intense discussion about CRISPR Cas9, the gene editing technique so precise, easy, and versatile that it has opened the possibility of chopping and moving DNA around. The implications are huge for humans and our genome. We could alter the genes of embryos, or treat genetic maladies in those already born. Now in 2018, clinical trials on humans are scheduled to start for the first time. However, our immune system may cause a major issue for this research.
To understand why our immune system is preventing us from using gene editing to treat disorders like sickle-cell anemia, it helps to step back and learn exactly what CRISPR Cas9 is. It is an immune response bacteria use to protect themselves from viruses. Cas9 is a protein the bacteria make that act as molecular scissors, cutting virus DNA to ribbons, and two of the most commonly used types of Cas9 come from bacteria that can cause staph infections or strep throat.
These are bacteria we want our immune systems to have a defense against. And to defend against them, our immune system has to be able to recognize the bacteria and the various proteins they make, so they can track them down and kill them. To see if these two versions of Cas9 would be destroyed by our immune system, researchers tested the blood of 34 donors for antibodies.
They found 65 percent had a defense against the strep version while 79 percent fought the staph variety. In another experiment with 13 blood donors, 6 of them had t-cells that attacked staph’s Cas9. If our immune systems respond to CRISPR, it could mean more than just rendering the therapy ineffective — it could mean our immune systems may actually kill us.