In a new study, an international team of scientists show that the G614 variant of SARS-CoV-2 has come to dominate COVID-19 cases around the world. They report that this mutation does not make the virus more deadly, but it does help the virus copy itself, resulting in a higher viral load, or “titer,” in patients.
The new study, led by scientists at Duke University, Los Alamos National Laboratory and La Jolla Institute (LJI), was published July 2, 2020 in Cell.
Back in March, two variants of SARS-CoV-2 were circulating. In addition to the G614, the other variant was the D614. The variants had just a small difference in their “spike” protein – the viral machinery that coronaviruses use to enter host cells, explained La Jolla Institute Professor Erica Ollmann Saphire, PhD., who leads the Bill & Melinda Gates Foundation-supported CoVIC at the institute.
Saphire said that viruses regularly acquire mutations to help them “escape” antibodies made by the human immune system. When a virus acquires many of these individual changes, it “drifts” away from the original virus. Researchers call this phenomenon “antigenic drift.”
In the new study, researchers’ tracking showed that while the G and D viruses both spread widely around the world, the G virus was “fixed” as the dominant variant by mid-March. They also determined that viruses carrying spike with the G mutation grew two to three times more efficiently, leading to a higher titer.
Saphire and her colleagues then used samples from six San Diego residents to test how human antibodies neutralized the D and G viruses. Would the fast-growing G virus be harder to fight?
Their experiments showed that the human immune response could neutralize the new G virus as well or better than the original D virus. This meant the immune system did not need to produce more antibodies or better antibodies against the G virus, even though this variant was more successful at spreading. This finding was in line with what doctors saw in COVID-19 patients.
