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 in four weeks.
Called Feluda, the test is named after a fictional detective created by the late Satyajit Ray, although it is also an acronym for FNCAS9 Editor-Linked Uniform Detection Assay. The test uses CRISPR gene-editing technology to identify and target the genetic material of Sars-CoV2, the virus that causes Covid-19. It has been developed by senior scientists Dr Debojyoti Chakraborty and Dr Souvik Maiti at the Council of Scientific & Industrial Research-Institute of Genomics and Integrative Biology (CSIR-IGIB) in New Delhi.
“The CRISPR-based Feluda testing works by combining CRISPR biology and paper strip chemistry. Briefly, Cas9 protein, a component of the CRISPR system, is barcoded to interact specifically with the Sars-CoV2 sequence in the patient’s genetic material. The complex of Cas9 with Sars-CoV2 is then applied to a paper strip, where using two lines (one control, one test) make it possible to determine if the test sample was infected with Covid-19,” said Dr Chakraborty, senior scientist, CSIR-IGIB.
The entire diagnostic process takes about one hour, starting from RNA to giving a visual readout on the strip, he said.
“Most labs are working with PCR(polymerase chain reaction)-based technology, which is costly and needs a lab set-up. Our paper strip does not require (biosafety) Level-2 or Level-3 lab for testing and can be done in any path lab,” said Anurag Agrawal, director, CSIR-IGIB, Delhi.
The US Food and Drug Administration (FDA) on Friday granted emergency-use approval for the world’s first CRISPR-based test for Covid-19. Unlike the test developed by CSIR-IGIB, the one developed in the US can only be done in hi-tech laboratories. Its developers at the Massachusetts Institute of Technology, Harvard University, the Ragon Institute and the Howard Hughes Medical Institute in the US are working on a simplified version which they hope will get approved for point-of-care use.
Unlike other CRISPR tests that use CAS12 and CAS13 proteins to detect Sars-CoV2, the CSIR-IGIB kit technology uses CAS9 protein (CRISPR-associated protein 9) to identify and bind to the target sequence.
“It’s a very accurate and accepted testing method and the advantage is that it can be used in any lab that has the technology. Lab technicians, however, may not be trained to use the technology, but it is easy to train them. With training, there can be widespread deployment across India,” said Dr Nirmal K Ganguly, former director general, Indian Council of Medical Research.
The acronym Feluda, wasn’t a coincidence. “Yes, I am a Satyajt Ray fan but the name was given by my wife, who is not a Bengali but is well aware of my sentiments,” said Dr Chakraborty.
CRISPR, which is short for Clustered Regularly Interspaced Short Palindromic Repeats, is a gene-editing technology that can be used to detect a specific snippet of DNA from a sequence. It can also be used turn genes on or off without altering their sequence.
“Feluda is not limited to Covid-19. We were working on Feluda for the past two years to develop an assay that can work on detecting any DNA-RNA or their mutations. At the end of January, we started working on adapting it for Covid-19,” said Dr Chakraborty.
This is the only Covid-19 testing kit that has been developed using CRISPR-based technology in India. Feluda has been licenced to Tata Sons, which will commercialise the technology for Covid-19 detection.
“It uses a test protocol that is simple to administer and easy to interpret enabling results to be made available to the medical fraternity in relatively lesser time, as compared to other test protocols. We believe that CRISPR is futuristic technology that can also be configured for detection of multiple other pathogens in the future,” said Banmali Agrawala, president, infrastructure and defence & aerospace, Tata Sons, in a statement.
Each Feluda test costs Rs 500 in the lab, and is expected to bring the cost of testing down from the Rs 4,500 per test for the real-time polymerase chain reaction test (RT-PCR), which is the only available test for detecting current Covid-19 infection.
