It uses CRISPR-Cas technology for the detection of genes specific to SARS-CoV-2 virus.This has been developed by the CSIR-IGIB and the TATA Group,and approved by the Drug Controller General of India for a commercial launch.

FELUDA:

1. FELUDA, an acronym for the FNCAS9 Editor-Limited Uniform Detection Assay, uses an indigenously developed, cutting-edge CRISPR technology for detection of the genomic sequence of SARS-CoV-2 virus
2. FELUDA low-cost paper-based test strip to detect Covid-19
3. The test showed 96% sensitivity and 98% specificity.This compares favourably to the ICMR’s current acceptation criteria of RT-PCR kit of at least 95% sensitivity and at least 99% specificity.
4. Named after Satyajit Ray’s famed detective, the Feluda test, which is priced at Rs 500 and can deliver a result in 45 minutes.
5. It  is able to differentiate SARS-CoV-2 from other coronaviruses even if genetic variations between them are minute. 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.
6. It can distinguish between SARS-CoV-2 and SARS-CoV sequences which differ by a single nucleotide.
7. Feluda changes colour if the virus is detected and doesn’t need expensive machines for detection.
8. The CRISPR Feluda test is the world’s first diagnostic test to deploy a specially adapted Cas9 protein, derived from Francisella novicida bacteria, to successfully detect the virus that causes Covid-19
9. 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.

10. The ̳Feluda‘ test strip has been invented by a team led by two Bengali-origin scientists — Dr Souvik Maiti and Dr Debojyoti Chakraborty.

    The strip uses cutting-edge gene-editing CRISPR-CAS-9 technology to target and identify genomic sequence of the novel coronavirus in suspected individuals. No other laboratory in India is developing test kit using CRISPR technology.Unlike Stanford and MIT, which use CAS-12 and CAS-13 proteins to detect the presence of the novel coronavirus, our kit uses CAS-9 protein technology

Advantages of Feluda compared to qPCR:

• Affordability
• Can be used in settings with limited resources
• Less time to result (around 45 minutes)
• No qPCR equipment (no need for expensive devices)
• High ease of use
  Lateral Flow based readout for easy interpretation of results
  With 96% sensitivity and 98% specificity, Feluda’s analytical performance is comparable to the qPCR results.

How It works?

• The nasopharyngeal swab is collected
• RNA is extracted
• A single step RT-PCR is done
• The FELUDA mix is prepared by incubating the dead FnCas9 protein, guide RNA and the amplified viral DNA
• The dip stick is immersed in the FELUDA mix
• Gold nanoparticle on the strip bind to the FELUDA complex
• A protein called Streptavidin on the test line captures this gold nanoparticle bound-FELUDA complex
• Unbound gold particles are captured on the control line
• Colour develops on the test line and/or control line. One line indicates negative and two lines mean positive.
• The test takes about one to two minutes

 

What is CRISPr/Cas9 technology?

CRISPR is a technology that can be used to edit genes .

The essence of CRISPR is simple: it’s a way of finding a specific bit of DNA inside a cell. After that, the next step in CRISPR gene editing is usually to alter that piece of DNA.CRISPR/Cas9 – a specific, efficient and versatile gene-editing technology we can harness to modify, delete or correct precise regions of our DNA.CRISPR/Cas9 edits genes by precisely cutting DNA and then letting natural DNA repair processes to take over.

The system consists of two parts: the Cas9 enzyme and a guide RNA.

Cas9 stands for CRISPR-associated protein 9 and is an enzyme.

CRISPR-Cas9, which is short for clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9, is a genome editing technology.

Genome editing (also called gene editing) is a group of technologies that give scientists the ability to change an organism’s DNA. These technologies allow genetic material to be added, removed, or altered at particular locations in the genome

• CRISPR-Cas9 was adapted from a naturally occurring genome editing system in bacteria.
• The bacteria capture snippets of DNA from invading viruses and use them to create DNA segments known as CRISPR arrays.
• The CRISPR arrays allow the bacteria to “remember” the viruses (or closely related ones). If the viruses attack again, the bacteria produce RNA segments from the CRISPR arrays to target the viruses’ DNA.
• The bacteria then use Cas9 or a similar enzyme to cut the DNA apart, which disables the virus.

Source:CSIR and The Hindu