Scientists develop CRISPR-based test for SARS-CoV-2

By Angela Betsaida B. Laguipo, BSNMay 4 2020

The novel coronavirus is a potent pathogen that has ravaged the globe over the past five months. Most of the world is at a standstill, with many nations in lockdown to curb the spread of the virus. With the vast number of people being infected, the pandemic has created a massive demand for widespread and valuable tools to detect the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes the coronavirus disease (COVID-19).

Throughout the pandemic, one of the major problems faced by countries worldwide is the lack of tests. COVID-19 can spread at a rapid rate through person-to-person contact, as well as through contaminated surfaces. A majority of the infected people are asymptomatic, which means it is harder to track and isolate them. With the scarcity of testing kits, it is harder to conduct mass testing.

Now, a team of scientists at the University of California Santa Barbara has developed a low-cost, rapid, and high-tech test that can detect SARS-CoV-2 effectively. They have developed a CRISPR-based test that is sensitive and effective as traditional tests. But, the new test is faster and easily deployed in the field, qualities not seen in the tests used today.  The research is published on the preprint server bioRxiv*.

Image Credit: UC Santa Barbara

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

The new test, called CREST (Cas13-based, Rugged, Equitable, Scalable Testing) assay, was based on a procedure that is different from the PCR or the polymerase chain reaction test, which faces a problem about the shortage of reagents. The scientists made sure that the new test can be produced at scale to cope with the demand across the globe.

The team scaled up massively by purifying enough of the protein to be used in the CRISPR-based assay to perform 500,000 tests in one go.

Detecting the coronavirus

Generally, the most common test used to detect the novel coronavirus today is a real-time PCR test, which was recommended by the U.S. Centers for Disease Control and Prevention (CDC). In this type of test, the single-strand RNA is extracted from sample tissue and converted into double-helix DNA by exposing it to an enzyme known as reverse transcriptase.

Detection involves locating particular points on the strands; however, the process needs a reagent that is produced just in small batches. This limitation makes it hard for countries with high infection rates to test residents.

With the new CREST test, testing can be done in the field using a DIY-inspired heating machine. The researchers created a protein, which was edited using CRISPR technology to recognize the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). As SARS-CoV-2 invades, Cas13 starts to chew on it to cause RNA destruction. The by-product of this destruction are fluorescent indicators that glow in the assay immediately, indicating the presence of the novel coronavirus in the body.

“Fluorescence in the sample indicates that the genetic material has been recognized as being from the SARS-CoV-2 virus, and duplicated, amplifying the signal. Though sensitive, the real-time PCR test can take up to several days to return results,” the researchers explained.

The assay directly and rapidly detects the presence of SARS-CoV-2 in patients, which can help health officials in tracking and isolating patients. The Cas proteins seek, find, and interact with genetic material.

Though the new test is promising, it has not been approved by the Food and Drug Administration (FDA) as yet. The test method is not recognized by the U.S. Centers for Disease Control and Prevention (CDC) and, therefore, cannot be deployed to help the current situation today. However, the team is evaluating the common hurdles they are experiencing, planning a surveillance study to sample asymptomatic people for infection.

Mass testing and isolation of cases

Mass testing is a vital way to curb the novel coronavirus spread, seeing as most SARS-CoV-2 carriers are asymptomatic. Therefore, they do not know that they are infected, and as a result, unwittingly transmit the virus to others.

Mass testing for possible infected patients in countries and communities will help stop the further spread of the virus. Positive cases can immediately be isolated to reduce SARS-CoV-2 transmission further.

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources