A study of the spike protein of SARS-CoV-2, the virus which cause COVID-19, suggests that current vaccines may be less effective against the Beta variant first identified in South Africa. Present on the surface of SARS-COV-2, spike proteins enable the virus to attach to and enter our cells, and all current vaccines are directed against them.
The study, published in the journal Science on June 24, used cryo-electron microscopy (cryo-EM) to compare the spike protein from the original virus found in China in 2019, with that of the Beta variant, and the Alpha variant first identified in the UK. Cryo-Em is an imaging technique used to determine the bio-molecular structures at near-atomic resolution.
The findings led by researchers at Boston Children’s Hospital in the US indicate that mutations in the Beta variant, also known as B.1.351, change the shape of the spike surface at certain locations. As a result, neutralising antibodies induced by current vaccines are less able to bind to the Beta virus, which may allow it to evade the immune system even when people are vaccinated.
“The mutations make antibodies stimulated by the current vaccine less effective,” said Bing Chen, from the division of Molecular Medicine at Boston Children’s. The Beta variant is somewhat resistant to the current vaccines, and we think a booster with the new genetic sequence can be beneficial for protecting against this variant,” Chen added.
The researchers also found that mutations in the Beta variant make the spike less effective in binding to ACE2 — suggesting that this variant is less transmissible than the Alpha variant. As for the Alpha variant (B.1.1.7), the study confirms that a genetic change in the spike helps the virus bind better to ACE2 receptors, making it more infectious.
However, testing indicates that antibodies elicited by existing vaccines can still neutralise this variant, according to the researchers. They said to be a heightened threat, a SARS-CoV-2 variant would need to do three things: spread more easily, evade the immune system in vaccinated people or those previously exposed to COVID-19, and cause more severe disease.
However, the researchers said the Alpha and Beta variants do not meet all these criteria. “Our data suggest that the most problematic combination of such mutations is not yet present in the existing variants examined here,” they added.
The research team is now analysing the structures of other variants of concern, including the Delta variant (B.1.617.2), first identified in India.