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The Lancet Infectious Diseases: SARS-CoV-2 XBB.1.5 is highly infectious

Japanese scientists have found that the omicron variant of the SARS-CoV-2 XBB.1.5 coronavirus, common in the Western Hemisphere, is highly transmissible and infectious. This is reported in the article published in The Lancet Infectious Diseases.

SARS-CoV-2 XBB.1.5 was first detected in October 2022. Scientists have shown that this variant has a new mutation in the S protein that allows the virus to attach to a cell receptor called an enzyme converting angiotensin 2 (ACE2), allowing it to invade human cells. The mutation favors substitution of the amino acid serine for proline at position 486 and poses a virological threat for a number of reasons.

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Researchers conducted a series of experiments, establishing that SARS-CoV-2 XBB.1.5 is characterized by an increased reproductive index (Re), which shows how many individuals a typical sick person infects. The new Re strain was 1.2 times higher than that of the original XBB.1. Additionally, as of December 2022, XBB.1.5 is rapidly replacing BQ.1.1, which until now was the predominant line in UNITED STATES.

The dissociation constant (KD) corresponding to the physical interaction between the XBB.1.5 receptor binding domain (RBD) of protein S and the human ACE2 receptor is significantly (4.3 times) lower than that of XBB.1 S RBD. KD characterizes the tendency of an object to dissociate, that is to say to separate into particles. In other words, the XBB.1.5 variant binds to the human ACE2 receptor with very high affinity.

The XBB.1.5 S protein is highly resistant to neutralizing antibodies caused by breakthrough infections of the BA.2/BA.5 subvariants. Thus, patients previously infected with BA.2/BA.5 may not show strong immunity against XBB.1.5, increasing their risk of infection and disease.

Members of the Genotype to Phenotype Japan (G2P-Japan) Consortium concluded that SARS-CoV-2 XBB.1.5 could become a serious threat to public health, including in the Eastern Hemisphere, and that preventive measures should be taken. taken.

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