More accurate than a rapid antigen test and almost as fast, India’s ‘Feluda’ Covid-19 CRISPR test that changes color upon detection of the SARS-CoV-2 virus could be a cheaper, faster and easier alternative to a diagnosis by RT-PCR. scientists say.
Named after the famous detective Satyajit Ray, the Feluda test, which is priced at Rs 500 and can give a result in 45 minutes, can differentiate SARS-CoV-2 from other coronaviruses even if the genetic variations between them are minimal. .
The Feluda Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) test, developed by the New Delhi-based CSIR-Institute of Genomics and Integrative Biology (IGIB) and the TATA Group, received regulatory approvals last week from the Drug Controller General of India ( DCGI). ) for commercial launch.
It meets high-quality benchmarks with 96% sensitivity and 98% specificity for detecting the novel coronavirus, Debojyoti Chakraborty, CSIR-IGIB lead scientist and part of the team that developed the test, told PTI.
Sensitivity is defined as the ability of a test to correctly identify individuals with the disease, while specificity is the ability of the assay to accurately identify those without the disease.
Similar to a pregnancy strip test, Feluda changes color if the virus is detected and does not need expensive machines for detection. “CRISPR technology uses a highly specific CAS9 protein to find and bind to the target Covid signature. This is then combined with the chemistry of the paper strips to get a visual reading on a paper strip, ”Chakraborty explained.
The test can help the country, with the second-highest number of Covid-19 cases in the world at 61.45 lakh of cases, scale up testing for the disease quickly and inexpensively, the researchers behind the test said in a release.
Virologist Upasana Ray noted that the CRISPR-based Covid-19 detection system is a cheaper option than RT-PCR tests, which cost more than Rs 1,600. RAT and Feluda are in the same price range. FELUDA, an acronym for FNCAS9 Editor-Limited Uniform Detection Assay, uses state-of-the-art CRISPR technology developed in the country for the detection of the genomic sequence of the SARS-CoV-2 virus, the scientists said.
CRISPR is a gene editing technology and is used to correct genetic defects and treat and prevent the spread of disease.
The technology can detect specific sequences of DNA within a gene and uses an enzyme that works like molecular scissors to cut it.
According to Ray, Feluda is capable of detecting even small amounts of the genetic material of the new coronavirus, based on very minute differences in its RNA, the genetic material of a virus. “Feluda is an alternative to quantitative RT-PCR tests and it is very specific. It is capable of detecting low copy number nucleic acids (less amount of viral RNA) as well as single nucleotide variations, ”Ray, senior scientist at CSIR-IICB, Kolkata, told PTI.
He explained that the tests are so specific that they can distinguish SARS-CoV-2 infections from other coronaviruses such as the one that caused the 2002-03 SARS pandemic.
“It can distinguish between SARS-CoV-2 and SARS-CoV sequences that differ by a single nucleotide. Unlike RT-PCR, which requires expensive machines, Feluda is simple and can be used both in laboratories and outdoors with a faster response time, “he added. In May, the US granted emergency use approval for the world’s first CRISPR-based test for Covid-19, developed by the Massachusetts Institute of Technology (MIT) and Harvard University.
The CRISPR Feluda test is the world’s first diagnostic test to implement a specially adapted Cas9 protein, derived from the bacterium Francisella novicida, to successfully detect the virus that causes COVID-19, the researchers said. Other CRISPR tests, such as the one developed in the US, use CAS12 and CAS13 proteins to detect SARS-CoV-2. Compared to a rapid antigen test, which interprets results in 30 minutes, Ray said the Feluda test would take a little longer, up to 45 minutes, but is more accurate and specific.
Rapid antigen tests detect viral proteins or parts of them, while CRISPR detects nucleic acids or RNA in the case of Covid-19, Ray said.
Chakaraborty noted that RT-PCR takes about 1.5 hours, skilled labor, and a dedicated and expensive RT-PCR machine that is not widely available.
“Feluda offers similar sensitivity and specificity to RT-PCR, but it is inexpensive, requires a widely available basic PCR machine, and does not require a lot of skilled manpower. Chemistry and biology are, of course, different, ”added Chakraborty.
“This marks a significant achievement for the Indian scientific community, going from R&D to high precision, scalable and reliable testing in less than 100 days. The Tata CRISPR test achieves the levels of precision of traditional RT-PCR tests, with faster response time, less expensive equipment and greater ease of use, ”the researchers said in their statement.
They described CRISPR as a futuristic technology that can also be configured to detect other pathogens.
“Current R&D aims to make Feluda more of a point of care, simpler and more implementable to meet the country’s testing needs and allow return to workplaces, schools, etc.,” added Chakraborty .
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