Characterization of SARS-CoV-2 Omicron BQ.1.1 biorxivpreprint UTokyo_News_en SARSCoV2 COVID19 Omicron Variant BQ11
By Tarun Sai LomteDec 9 2022Reviewed by Aimee Molineux In a recent study posted to the bioRxiv* preprint server, researchers characterized the severe acute respiratory syndrome coronavirus 2 Omicron BQ.1.1 sub-variant.
Instead, the emergent sub-variants appear to be under convergent evolution, acquiring amino acid substitutions at the same site. The BQ.1.1 sub-variant, a descendant of BA.5, harbors five convergent substitutions and has been classified as a variant under monitoring by the World Health Organization .
Moreover, the spike haplotype corresponding to the BQ.1.1 sub-variant had the highest Re. Further investigations indicated that viral fitness increased independently in multiple Omicron lineages during BA.5 diversification. The analysis also suggested that BQ.1.1 increased its fitness by serially acquiring K444T, N460K, and R346T substitutions.
The N460K and R346T substitutions in BQ.1.1 spike were implicated in the significantly enhanced binding affinity. Further, BQ.1.1 pseudovirus showed higher infectivity than BA.2 or BA.5 pseudovirus. The R346T and N460K substitutions of the BQ.1.1 spike were responsible for the increased infectivity. Syrian hamsters were infected with clinical isolates of Delta, BA.5, or BQ.1.1.
Finally, the authors examined the intrinsic pathogenicity of SARS-CoV-2 Omicron BQ.1.1 by analyzing the right lung of infected hamsters and scoring five histopathological features/parameters – 1) bronchitis/bronchiolitis, 2) hemorrhage with congestive edema, 3) alveolar damage, 4) hyperplasia of type II pneumocytes, and 5) the area of hyperplasia.
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