A variation in the viral genome of Covid-19 has helped the virus to infect human cells and become the dominant strain circulating around the world, according to a study published in the journal Cell.
The researchers showed the variation named D614G is more infectious in cell cultures under laboratory conditions. The variant makes a small but effective change in the 'spike' glycoprotein that protrudes from the surface of the virus, which it uses to enter and infect human cells.
“We could see at the time of our initial preprint submission that the G614 variant was becoming the predominant form globally, but we could not differentiate between three broad possibilities that might explain a fitness advantage,” says lead author Bette Korber, a laboratory fellow at Los Alamos National Laboratory.
“The added experiments in the published study point to enhanced infectivity due to the spike protein change as the favored hypothesis. But infectiousness and transmissibility are not always synonymous, and we hope others will study these viruses in greater detail with wild-type virus in natural infection settings and varied target cells.”
While coronaviruses generally have low rates of mutation, Korber and her colleagues were concerned that even small mutations to SARS-CoV-2 could hinder efforts to understand and fight the virus.
“We knew from our direct experience in the HIV field that in some cases, a single amino acid change can have a major phenotypic impact,” she said.
To that end, the team worked to develop a publicly available data-analysis pipeline that could mine SARS-CoV-2 sequences made available on the Global Initiative for Sharing All Influenza Data (GISAID) database to help scientists explore potentially interesting mutations.
They quickly identified the D614G variant as something to pay attention to: its key amino acid change from aspartic acid (D) to glycine (G) occurred on a protein that's crucial to how the virus infects human cells-and it was rapidly becoming the dominant version of the virus around the world.
“Although coronaviruses have some proofreading capacity, mutations can emerge, and vigilance, surveillance, and continued study of the virus will be key to ensuring that the drugs, antibodies, and other interventions under development remain effective, said Erica Ollmann Saphire at La Jolla Institute for Immunology at Duke University.
