Mutations help Epsilon coronavirus variant evade vaccine immunity, says study
What's the story
Three mutations in the spike protein of the Epsilon variant of SARS-CoV-2 help the virus to evade the protection offered by current vaccines or past COVID-19 infection, a study said.
The mutations provide the variant of concern—named CAL.20C—a means to totally evade specific monoclonal or lab-made antibodies used in clinics, and reduce the effectiveness of antibodies from plasma of vaccinated people, researchers said.
Variant
Epsilon variant relies on an indirect and unusual neutralization-escape strategy
The team, led by researchers at the University of Washington in the US, visualized the variant's infection machinery to see what is different from the original configuration of the coronavirus, and what the implications of these changes are.
The findings, published in the journal Science on July 1, show that the Epsilon variant "relies on an indirect and unusual neutralization-escape strategy."
Analysis
Precursor to Epsilon variant emerged in May 2020 in California
Neutralizing antibodies are an important specific defense against viral invaders.
A molecular clock analysis shows that the precursor to the Epsilon variant emerged in May last year in California.
By the summer of 2020, it had diverged into its B.1.427/B.1.429 lineages and spread across the US.
The variant has been reported in at least 34 other countries since then.
Information
Plasma's neutralizing potential against Epsilon was reduced about 2-3.5 fold
The researchers tested the resilience against the Epsilon variant of plasma from people who were exposed to the virus, as well as vaccinated people. The neutralizing potential of the plasma against the Epsilon variant of concern was reduced about 2 to 3.5 fold, they said.
Infection
The variant infects cells through its spike glycoprotein
Like the original SARS-CoV-2 virus identified in Wuhan, China in December 2019, the Epsilon variant infects cells through its spike glycoprotein - the structure that crowns the surface of the virus and helps it to infect the human cells.
The researchers found that the Epsilon mutations were responsible for rearrangements in critical areas of the spike glycoprotein.
Information
One mutation affected the receptor-binding domain on spike glycoprotein
Visualizing these mutations helps explain why antibodies had difficulty binding to the spike protein, according to the researchers. One of the three mutations in the Epsilon variant affected the receptor-binding domain on the spike glycoprotein, they said.
Mutations
Other two mutations affected the N-terminal domain
This mutation reduced neutralizing activity of 14 of 34 neutralizing antibodies specific to the receptor-binding domain, including clinical stage antibodies.
The other two mutations affected the N-terminal domain, which is the start of the spike protein.
The mutations also resulted in a total loss of neutralization by 10 out of 10 antibodies tested specific to the N-terminal domain in the spike protein, researchers said.