重変異型SARS-CoV-2亜種BA.2.86は、当初懸念されたほど抗体に対して抵抗性を持たない(Heavily mutated SARS-CoV-2 variant BA.2.86 not as resistant to antibodies as first feared)

2023-09-30

2023-09-29 カロリンスカ研究所(KI)

◆新たなSARS-CoV-2変異体BA.2.86が登場し、スパイク遺伝子に多くの変異を持っています。この変異はオミクロンのように感染力が高まる可能性があり、抗体の効果を低下させ、ワクチンの更新が必要になるかもしれません。研究者はBA.2.86に対する抗体効果を調査し、XBB変異体に基づくワクチンがBA.2.86に対する保護を強化できる可能性を示唆しました。
◆しかし、BA.2.86はすべてのモノクロナル抗体治療に対して耐性があることも判明しました。この新変異体に対する免疫とワクチンの効果を評価し、新たな変異体に警戒しつつブースターワクチンを受けることを勧めています。

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中和抗体に対するSARS-CoV-2 BA.2.86変異体の感受性
Sensitivity of the SARS-CoV-2 BA.2.86 variant to prevailing neutralising antibody responses

Daniel J Sheward,Yiqiu Yang,Michelle Westerberg,Sofia Öling,Sandra Muschiol,Kenta Sato,Thomas P Peacock,Gunilla B Karlsson Hedestam,Jan Albert,Ben Murrell
The Lancet Infectious Diseases Published:September 27, 2023
DOI:https://doi.org/10.1016/S1473-3099(23)00588-1

After a prolonged period of near-complete global dominance of the recombinant XBB family of SARS-CoV-2 lineages, a substantially mutated sublineage of BA.2 has recently emerged. Designated BA.2.86,¹the geographic origin of this sublineage is currently unclear and, as of Sept 20, 2023, BA.2.86 sequences have been observed in at least 20 countries: Australia, Belgium, Canada, China, Denmark, France, Germany, Iceland, Israel, Japan, Luxembourg, Portugal, South Africa, South Korea, Spain, Sweden, Switzerland, Thailand, the UK, and the USA (appendix p 8).

With a long branch of unobserved evolution (figure A), including more than 30 mutations in the spike protein relative to BA.2, with many at key antigenic sites (figure B), the emergence of BA.2.86 is reminiscent of the initial emergence of omicron.²This raises immediate questions about whether it is sensitive to any previously approved clinical monoclonal antibodies with activity against BA.2, and the degree to which it is able to escape antibody responses in the current setting in which individual exposure histories are a complex combination of multiple immunisations and multiple previous SARS-CoV-2 infections.