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Sneaks Past the System at First

A new study suggests that the Alpha variant of SARS-CoV-2 has become so dominant by disabling the host's first line of immune defense, the New York Times says.

Officials in the UK announced in late 2020 that they had identified a new SARS-CoV-2 variant, now dubbed Alpha, that appeared to be more transmissible. By April, it became the dominant strain in the US, the Times adds.

In a new preprint at BioRxiv, researchers from the UK and US compared different coronavirus strains grown in lung cells and found the Alpha variant has increased expression of the innate immune antagonist Orf9b as well as of Orf6 and the nucleocapsid protein. At the same time, the lung cells produced lower levels of interferon.

The researchers suspect that the Alpha variant has a more effective innate immune antagonism as Orf9b affects TOM70, which is needed for interferon response, to reduce and delay the host response. This gives the virus time to reproduce to higher levels. Co-author Gregory Towers from University College London tells the Times that when the host immune response does catch up, it is likely more robust and leads to more coughing and viral shedding, which boosts transmission.

 "Any successful virus has to get beyond that first defense system. The more successful it is at doing that, the better off the virus is," Yale's Maudry Laurent-Rolle, who was not involved in the new study, tells the Times.