Diagnostic Test Image
After the strip is dipped in a test sample, if the virus or its variant is present, two bands will appear. (Credit: Nanyang Technological University)

A diagnostic test can detect the virus that causes COVID-19 even after it has gone through mutations. Called the VaNGuard (Variant Nucleotide Guard) test, it makes use of a gene-editing tool known as CRISPR, which is used widely in scientific research to alter DNA sequences and modify gene function in human cells in diagnostic applications.

Since viruses have the ability to evolve over time, a diagnostic test robust against potential mutations is a crucial tool for tracking and fighting the pandemic. Over its course so far, thousands of variants of SARS-CoV-2, the virus that causes COVID-19, have arisen, including some that have spread widely in the United Kingdom, South Africa, and Brazil.

The VaNGuard test relies on a reaction mix containing enAsCas12a, a variant of the enzyme Cas12a that acts like a pair of "molecular scissors".

The enzyme enAsCas12a is 'programmed' to target specific segments of the SARS-CoV-2 genetic material and to snip them off from the rest of its viral genome. Successfully snipping off segments is how the enzyme 'detects' the presence of the virus. The programming is done by two different molecules known as guide RNAs, which are designed to recognise specific sites on the SARS-CoV-2 genome.

In addition to its ability to detect SARS-CoV-2 even when it mutates, the VaNGuard test can be used on crude patient samples in a clinical setting without the need for RNA purification, and yields results in 30 minutes. This is a third of the time required for the gold standard polymerase chain reaction (PCR) test, which requires purification of RNA in a lab facility.

The team of scientists led by NTU hopes that the VaNGuard test can be deployed in settings where quickly confirming COVID-19 status of individuals is paramount.