CRISPR boosts cheap Zika test

Researchers have developed a quick and cheap 'paper-based' test that uses CRISPR to detect the Zika virus.

The test has successfully detected the virus in an infected macaque monkey, and the researchers say they expect a commercially available test for humans to be available 'within a matter of months'.

'The diagnostic platform … has provided a high-performing, low-cost tool that can work in remote locations,' said Dr Keith Pardee of the University of Toronto in Ontario, Canada, who is lead author of the study. He says that the test 'can be read out on a piece of paper no larger than a postage stamp'.

The Zika virus has been spreading rapidly throughout the Americas, leading to birth defects in the children of infected mothers. But current diagnostic tests are slow, expensive and require expertise to perform. They are also not effective in distinguishing the Zika virus from other similar viruses that may be present.

The research team adapted a technique first developed in 2014 as part of an Ebola diagnostic test. Biologically engineered, cell-free gene networks are embedded into paper that changes colour in the presence of a target RNA sequence. Their study, published in Cell, shows that the test not only detects the Zika virus, but can also differentiate between Zika and related viruses common in the geographical area, such as Dengue fever.

The inclusion of a genome-editing tool CRISPR also means that the test can distinguish different strains of the virus itself. Variations in the nature of the virus can lead to variation in symptoms. The strain from Brazil, for example, is closely linked to higher incidences of fetal microcephaly and Guillain-Barré syndrome, a rare immunological disorder. Although it has not yet been tested on human patients, the test successfully detected low levels of the virus in the plasma of an infected macaque.

The researchers say that the paper-based test costs less than a dollar, is simple to use and produces quick results. 'We [now] have a system that could be widely distributed and used in the field with low cost and very few resources,' said Professor James Collins of the Massachusetts Institute of Technology in Boston, who led the study.

Professor Collins now hopes to develop this new low-cost technology for testing in humans. 'Here we've done a nice proof-of-principle demonstration, but more work and additional testing would be needed to ensure safety and efficacy. We're not far off.'

It is also anticipated that the technique could be adapted for widespread use in other large outbreaks of illness.