It was reported in September 2020 that an accurate and low-cost strip test that can detect the coronavirus disease (Covid-19) within one hour is expected to be available for the first phase of testing and has obtained permission for commercial use. Called Feluda, the test is named after a fictional detective created by late Satyajit Ray, although it is also an acronym for FNCAS9 Editor-Linked Uniform Detection Assay.
The Tata group has developed the new COVID-19 test kit with the Clustered Regularly Interrupted Short Palindromic Repeats Corona Virus Test (CRISPR Corona Test), in association with the CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi. The Drug Controller General of India has also approved the use of this kit. With this, COVID-19 can be detected in less than one hour.
With 96 per cent sensitivity and 98 per cent specificity, the test is quite promising. CRISPR is a gene-editing technology and, in this latest diagnostic application, an indigenously developed CRISPR technology is used to detect the genomic sequence of the SARS-CoV-2 virus that causes Covid-19. This CRISPR test is being heralded as one its kind in the world, as it uses the Cas9 protein for detection applications compared to therapeutic use.
Feluda follow naturally from Sherlock, also a CRISPR-based test that received ‘emergency use authorisation from the US Food and Drug Administration in May 2020.
The test follows the same way as a normal real-time reverse transcription-polymerase chain reaction (RT-PCR), which is the extraction of ribonucleic acid (RNA) and its conversion to deoxyribonucleic acid (DNA) but differs by using a specifically designed PCR reaction to amplify a part of the viral nucleic acid sequence. Then a highly specific CRISPR, FnCAS9, developed at IGIB, binds to that sequence.
Using the innovative chemistry on a paper strip, the CRISPR complex, bound to that specific sequence, can be visualised as a positive band-like one sees in simple pregnancy tests.
In the RT-PCR tests, the RNA is converted to DNA by using specific primers and probes, with fluorescent reporters, to amplify and detect viral nucleic acid presence. It requires expensive Real-Time PCR machines which are available at specialised sites.
If successfully commercialised, which depends upon all its components being available at scale and the commercial product being successfully validated by regulatory agencies, it would allow the test to be done in local path-labs that do not have expensive real-time PCR machines, but simple cheap thermo-blocks used for conventional PCR.
The test is named after Feluda because the researchers at MIT and University of California, Berkeley also use CRISPR, but different technologies. They have named the tests as ‘’Detector” and ‘’Sherlock”, so Feluda was an Indian version.
Courtesy: The Hindu Business Line