CRISPR-Based Diagnostic SHERLOCK Optimized for Rapid Use During Viral Outbreaks

Source: Broad Institute of MIT and Harvard

Summary: Researchers report a new tool that engineers the CRISPR-based diagnostic SHERLOCK for rapid outbreak response.

Rapid and sensitive tools are critical for diagnosing, surveilling, and characterizing an infection. Researchers from the Broad Institute of MIT and Harvard reported a new tool that engineers the CRISPR-based diagnostic SHERLOCK for rapid outbreak response. The updates to SHERLOCK, which was first unveiled in 2017, enable clinicians to quickly and cheaply diagnose patient samples and track epidemics such as Ebola and Zika with limited equipment lifting a barrier to rapid deployment in outbreak zones. The platform can now be used to detect viruses directly in clinical samples such as blood or saliva, eliminating a processing step that previously required a lab environment and professionally trained personnel. The development primes SHERLOCK for use in areas where special training and clinical laboratories can be challenging to access. The study findings were published in the journal Science.

shorthand for Specific High-sensitivity Enzymatic Reporter unLOCKing

A collection of SHERLOCK paper test strips. (Left) Unused paper strips. (Middle) Paper tests displaying a negative SHERLOCK readout. (Right) Paper tests displaying a positive SHERLOCK readout. Credit: Broad Institute of MIT and Harvard

The SHERLOCK diagnostic platform (shorthand for Specific High-sensitivity Enzymatic Reporter unLOCKing) uses a programmed Cas13 enzyme paired with reporter molecules to indicate the presence of a genetic target, such as a virus. Until now, a crucial preliminary step for SHERLOCK involved extracting and isolating nucleic acids from patient samples which typically requires a lab and trained personnel, making it difficult to accomplish in the field. Here, the research team developed a simpler method that allows Cas13 to detect its target directly in bodily fluid samples such as saliva or blood.

The process is called HUDSON, or Heating Unextracted Diagnostic Samples to Obliterate Nucleases. It consists of a rapid chemical and heat treatment used on the samples in order to inactivate certain enzymes that would otherwise degrade the genetic targets. The processed clinical samples can then be run through the SHERLOCK procedure, and the final detection results, positive or negative, can be easily viewed on the paper strips that Broad Institute researchers introduced with a series of SHERLOCK upgrades published in February. The whole pipeline can be completed in under 2 hours.

Graduate student, Catherine Freije said, “With every enhancement to the SHERLOCK pipeline, the diagnostic process accelerates and requires less equipment, we’re trying to make these tools better and easier to use so that the diagnosis can move closer to the patient, where it really needs to be.”

More Information: Cameron Myhrvold et al, “Field-deployable viral diagnostics using CRISPR-Cas13”, Science (2018). DOI: 10.1126/science.aas8836 

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