When CRISPR was coupled with the enzyme Cas12a, researchers at the University of California, Berkeley, found that the system could detect the human papillomavirus (HPV) subtypes with high accuracy in human samples. The team named this mechanism DETECTR (DNA Endonuclease Targeted CRISPR Trans Reporter) mechanism. Early detection of viral infections such as HPV is crucial to prevent or treat conditions linked to the virus, including cervical cancer in women.
'We found something absolutely surprising,' said study author and CRISPR pioneer Professor Jennifer Doudna of the University of California, Berkeley, speaking to STAT news. In the study, published in Science, she and her team programmed CRISPR-Cas12a with a reporter molecule and specific RNA guide to detect and snip the double-stranded DNA sequence of HPV. The reporter molecule gave off a fluorescent signal when cut by CRISPR, revealing that Cas12a induced cuts in double-stranded as well as single strands of DNA.
DETECTR could also be used to identify tumour cells and fetal cells in pregnant women, the authors suggest. The technology could be useful in a diagnostic setting in under-resourced areas and countries to provide faster results. Current virus diagnostic-kits and DNA sequencing technology require more time to analyse data and offer a diagnosis.
'[DETECTR] remains active and able to cut any single-stranded DNA that comes by,' said Professor Doudna. While the mechanism offers new opportunities for medical use, at the same time it may be problematic if it induces unintended mutations and 'triggers undesired gene edits', she acknowledged.
In a second paper published in Science, Professor Doudna's team and researchers at the McGovern Institute in Boston, Massachusetts, showed that the diagnostic tool SHERLOCK (Specific High Sensitivity Reporter unLOCKing) could be adapted to accurately detect viruses such as Zika and dengue in human samples. Like DETECTR, SHERLOCK detects specific DNA and RNA sequences of viruses, including Zika or dengue, with high accuracy rates using CRISPR enzymes.