A number of people may have a natural immunity to the Cas9 proteins of the CRISPR-Cas9 genome editing machinery, Stat News reports. This, Fierce Biotech adds, could complicate efforts to develop the tool as a therapeutic approach.
Researchers from Stanford University note in a preprint appearing at BioRxiv that most Cas9 proteins used are derived from either Staphylococcus aureus or Streptococcus pyogenes, which both cause a high number of infections among people. This led Stanford's Matthew Porteus and his colleagues to explore whether people harbor immunity to the S. aureus homolog of Cas9 or the S. pyogenes homolog of Cas9. When they analyzed 22 blood samples they obtained from newborns and 12 blood samples from adults, the researchers found that 79 percent had immunity to the S. aureus Cas9 homolog and 65 percent did to the S. pyogenes Cas9 homolog.
Porteus tells Stat News that his team's findings don't mean that work developing CRISPR as a treatment should stop, but just that researchers should be aware of the issue. Porteus is one of the scientific founders of CRISPR Therapeutics.
The University of Florida's Roland Herzog also tells Stat News that the findings are "not a show stopper, but the field needs to know about this, that it's a potential problem that they need to work around or fix."
Indeed, alternatives to the Cas9 enzyme have been under exploration.