Structural Changes In Early Covid Variants Spark Alarm
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Even as India grapples with the newly discovered covid-19 strain Delta Plus, a new study has revealed that two older variants—Alpha, first found in the UK, and Beta (South Africa)—are circulating in India with changes to their structures. The study suggested current vaccines may be less effective against the Beta variant—though a booster may work. The study comes as confirmation of fears that existing covid vaccines may not protect against rapidly spreading new variants.

The latest in a series of structural studies of the variants’ spike protein led by Bing Chen at Boston Children’s Hospital, US, revealed new properties of the Alpha and Beta mutants. The new study, used cryo-electron microscopy to compare the spike protein of the original virus with those of Alpha and Beta.

The findings indicate that mutations in the Beta variant change the shape of the spike surface at certain locations in the body. As a result, neutralizing 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. 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 said. However, the study 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 Alpha.

As for the Alpha variant, 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 built up by existing vaccines can still neutralize this variant. To be a heightened threat, the researchers said, a 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.

Fortunately, the Alpha and Beta variants do not meet all these criteria, the authors said. “Our data suggest that the most problematic combination of such mutations is not yet present in the existing variants examined here," the researchers said.

Source:
https://science.sciencemag.org/content/early/2021/06/23/science.abi9745?rss=1
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