Basic virus biology to drive more reliable testing of COVID-19

In a world-first finding that has major implications for future research into COVID-19, Geelong scientists have discovered that SARS-CoV-2 remains detectable in the cells far longer than previously thought, helping explain why some patients continue to test positive for the virus well into the recovery period.

In a world-first finding that has major implications for future research into COVID-19, Geelong scientists have discovered that SARS-CoV-2 remains detectable in the cells far longer than previously thought, helping explain why some patients continue to test positive for the virus well into the recovery period.

The research team at the Geelong Centre for Emerging Infectious Diseases (GCEID), a partnership which includes Deakin University and Barwon Health, said the finding, published today in Nature Communications, opens new opportunities to study the progression of the virus infection.

GCEID Director, Professor Soren Alexandersen, said it was originally thought that virus building blocks produced during active infection did not persist once the body’s immune system had shut down virus replication, but his team had identified molecules in swabs from patients well into the recovery period.

“This finding improves our understanding of how the virus hijacks people’s cells and provides clues about the role of different virus proteins when someone becomes infected and apparently stays test-positive for an extended time,” Professor Alexandersen said.

“In contrast to humans and other animals that have DNA genomes, the SARS-CoV-2 virus builds its genome out of a molecule called RNA which is normally used inside our cells to send instructions and signals.

“Once the virus enters a cell, it uses its genome to ‘trick’ the cell into making proteins for the virus, which help the virus take control of the cell and produce new virus particles.

“Because these instruction molecules are much less stable than DNA, it was thought that once infection had passed, the molecules produced by the virus would rapidly disappear.

“We now know that the virus cleverly hides these instructions to make its proteins inside the cell and, with this discovery, we can detect these RNA molecules for a much longer period of time – two weeks or more after initial detection.”

The Geelong group used whole genome sequencing technologies and molecular techniques to look at the RNA present in diagnostic swab samples from infected people.

They searched for molecules where the virus had stitched the different sections of its genome together and found these molecules were protected by membrane structures made by infected cells.

“This finding offers an explanation as to why some patients test positive for the virus well after the infection is thought to have passed,” Professor Alexandersen said.

“It could potentially lead to a test to see if a patient is actually infected or simply carrying left-over RNA molecules.

“It also enables future research to look in more detail at what the virus is doing at different times during infection, which could lead to a deeper understanding of the function of the different virus proteins.

“In other viruses, once the functions of virus proteins are understood, it allows researchers to start asking the question: is there a drug which can target that protein and can be used to prevent infection or help sick patients?”

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