As the world waits for the coronavirus pandemic curve to be permanently flattened, public health experts mandate that millions of people have to coronavirus testing to determine if states are safe to reopen. While some companies have invented self-contained devices that test for the coronavirus and deliver a result in minutes, they can be costly and with limited chemical supplies.
According to Dr. Joshua Sharfstein, a professor of health policy at Johns Hopkins University Bloomberg School of Health, it is important that scientists search for new kinds of coronavirus tests that can compare to the polymerase chain reaction (PCR) standard tests now in use.
Accurate but Time-Consuming
PCR was invented about 35 years ago by the biochemist Kary Mullis. The venerable technology allowed scientists to find pieces of DNA containing a particular sequence, even if that sequence was extremely rare. Dr. Mullis won the Nobel Prize in 1993 for inventing PCR.
When researchers discovered the coronavirus that causes Covid-19 in January 2020, they used its genetic sequence to create PCR tests for it. However, PCR involves time-consuming steps that have to be carried out by trained technicians. This is a huge drawback in a pandemic.
Amidst all these, a team of scientists has been working with CRISPR, a pioneer of gene-editing technology. Crispr became well-known several years ago as a way to precisely edit DNA. Dr. Feng Zhang, a researcher at the Broad Institute in Cambridge, Massachusetts, and his team have been retooling its tags and enzymes as a way to detect viruses. Like PCR, the CRISPR procedure begins with the creation of a molecular tag that can lock onto a particular spot in a gene. The enzyme will then give off a signal once it has reached the target, instead of cutting the gene.
As Quick as a Pregnancy Test Kit
According to Zhang, the coronavirus testing hardware they are developing could be as simple as a pregnancy test kit and would cost only about $6. They hope that this will be a good alternative to the sophisticated and expensive laboratory procedures that take time to show results as well as require thousands of trained people to perform. However, their method has not yet been tested by other scientists, nor have their findings been published by a scientific journal.
The scientist starts the process by putting samples in a chemical-filled tube that can tear open viruses. Then, using an eye-dropper-like device, they move some of the liquid into a second tube containing the CRISPR molecules. After letting it immerse in the water at 140 degrees Fahrenheit for an hour to allow the reaction to finish, they then stuck a piece of paper in the tube to see if the coronavirus is present. Just like a procedure similar to a pregnancy test, two lines appearing on the paper meant the coronavirus was present.
Saliva and Nasal Swabs for Coronavirus Testing
Out of the 12 Covid-19 patients used for the study, they were able to detect the virus on 11 of them at 3 out of 3 tries and 2 out of 3 tries for the 12th patient. On the other hand, five healthy people used for the test all consistently showed negative results. The researchers also found that both nasal swabs and saliva work on the test.
The team is under discussions with manufacturers to create a single cartridge in which the two steps could take place. With mass production, they expect that the cost would further decrease. They have also set up a website with the instructions for STOPCovid hoping that other researchers will try out their procedure and find ways to improve it.
A New Novel Coronavirus Testing Procedure
Charles Chiu, an infectious disease physician at the University of California, San Francisco, and his colleagues at U.C.S.F. collaborated with researchers at Mammoth Biosciences, published a study in Nature Biotechnology describing a new assay for the novel coronavirus that causes COVID-19 that uses the technique to deliver results in about 40 minutes. The test uses different reagents than the PCR-based SARS-CoV-2 ones that are currently in use, offering a potential alternative where there are shortages of the chemicals needed to conduct the latter assays. One drawback, however, is that the new approach’s sensitivity, or ability to correctly provide positive results, is slightly lower than that of existing tests.
The team is targeting the E (envelope) and N (nucleoprotein) genes of SARS-CoV-2 using a protein called CRISPR-Cas12. The N gene is the gene that is most highly expressed in viral infections making it easy to detect and is also the same target of the Centers for Disease Control and Prevention’s PCR tests. The E gene on the other hand is one of the targets used by the World Health Organization.
According to the researchers, their assay uses inexpensive enzymes and reagents that are different from PCR tests and could readily be available which could help ramp up testing. They also see the importance of testing in point-of-care settings that don’t require bulky equipment to be carried out.