CRISPR has another trick up its sleeve. The system that sparked a revolution in gene editing can also be used in fast and cheap tests for pathogens.
A tool based on CRISPR has been shown to detect the Zika virus in blood, urine and saliva. It was developed by researchers at the Broad Institute in Cambridge, Massachusetts, who call it SHERLOCK – for Specific High Sensitivity Enzymatic Reporter Unlocking.
CRISPR was discovered in E. coli, which uses it to recognise the genetic material of viruses and destroy it.
So far, researchers have mostly exploited CRISPR as a gene-editing tool, but it may also prove useful for medical testing. “Once we realised how the enzyme works, we saw that it could have unlimited applications in diagnostics,” says team member Omar Abudayyeh.
The SHERLOCK tool works by making RNA copies of DNA. It then uses CRISPR to search for specific genetic sequences. Once found, an enzyme causes fluorescence, signalling the detection of the desired target.
As well as Zika virus, the team has also used SHERLOCK to detect antibiotic resistance genes in Klebsiella pneumoniae bacteria, and health-related gene variants in human saliva. The researchers were able to use the system to identify cancer-causing mutations in samples of genetic material they created to mimic what is found in the blood – suggesting that it could be used as a tool for understanding cancer too.
The team says the system has advantages over some other tests: it’s able to detect single molecules of genetic material among mixed samples, and can distinguish between genetic sequences that differ by only one letter. It’s also fast, working in about an hour, and can be adapted as a paper test costing only 61 cents – cheap enough to be used in a wide variety of settings.
“As the next epidemic or viral threat comes up – for example, the next Zika or Ebola – we think there’s a lot of utility in using this for better surveillance for those outbreaks,” says Jonathan Gootenberg, another team member.
Janet Daly at the University of Nottingham, UK, says the sensitivity of the new test is particularly important for viruses like Zika and dengue, which are easily missed.
“The approach ticks many of the boxes for diagnosis of emerging viruses, including the ability to rapidly redesign the test to recognise a novel virus,” she says. “However, it is yet to be determined how robust it is when used with real patient samples in the field.”
Journal reference: Science, DOI: 10.1126/science.aam9321
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