Different SARS-CoV-2 strains haven’t yet had a major impact on the course of the pandemic, but they might in future.
When COVID-19 spread around the globe this year, David Montefiori wondered how the deadly virus behind the pandemic might be changing as it passed from person to person. Montefiori is a virologist who has spent much of his career studying how chance mutations in HIV help it to evade the immune system. The same thing might happen with SARS-CoV-2, he thought.
In March, Montefiori, who directs an AIDS-vaccine research laboratory at Duke University in Durham, North Carolina, contacted Bette Korber, an expert in HIV evolution and a long-time collaborator. Korber, a computational biologist at the Los Alamos National Laboratory (LANL) in New Mexico, had already started scouring thousands of coronavirus genetic sequences for mutations that might have changed the virus’s properties as it made its way around the world.
Compared with HIV, SARS-CoV-2 is changing much more slowly as it spreads. But one mutation stood out to Korber. It was in the gene encoding the spike protein, which helps virus particles to penetrate cells. Korber saw the mutation appearing again and again in samples from people with COVID-19. At the 614th amino-acid position of the spike protein, the amino acid aspartate (D, in biochemical shorthand) was regularly being replaced by glycine (G) because of a copying fault that altered a single nucleotide in the virus’s 29,903-letter RNA code. Virologists were calling it the D614G mutation.