A fantastic diagram by Daniele Focosi showing the convergent evolution that has led to the lineages we have been discussing recently, including BQ.1.1, CA.1, BR.2 and the new XBB variant.
The speed with which SARS-CoV-2 is now evolving is quite breathtaking – ever-fitter variants are now being uncovered on an almost daily basis.
Just over one week since we revealed that BA.2.75.2 and BQ.1.1 were approaching SARS-1 levels of escape, those two variants have already been superseded in antibody evasion by no less than FOUR new strains with even more efficient escape mechanisms. Worse still, these four new strains could adopt other mutations to make themselves even fitter yet.
Yunlong Cao, one of the authors of the preprint “Imprinted SARS-CoV-2 humoral immunity induces convergent Omicron RBD evolution“, has continued to test new strains of SARS-CoV-2, and has found four more VOIDs* waiting in the wings.
Yunlong Cao: “Updating results regarding convergent variants BU.1, BR.2, BM.1.1.1, CA.1, and XBB. XBB is currently the most antibody-evasive strain tested, and BR.2, BM.1.1.1, CA.1 are more immune evasive than BA.2.75.2 and BQ.1.1.”
“Similar to BQ.1.1, XBB also escapes Evusheld and Bebtelovimab. BU.1, BR.2, BM.1.1.1, CA.1, and XBB all displayed sufficient hACE2 binding capability.”
“XBB is significantly more immune evasive than BA.2.75.2 and BQ.1.1 against plasma from all breakthrough infections, comparable to or even exceeding SARS-CoV-1 level escaping capability. BR.2, BM.1.1.1 and CA.1 also exhibit very strong immune evasion, but less compared to XBB.”
“XBB’s superior antibody escaping capability not only comes from the convergent RBD mutations, it’s NTD mutations, V83A and 144-deletion, are also extremely good at escaping NTD-targeting neutralizing antibodies.”
I believe there is still room for XBB to gain more mutations, such as L452R or K356T or both. BQ.1.1 may also evolve mutations on the NTD, such as the 144-del carried by BU.1, to catch up on immune evasion capability. We will keep on updating results on these emerging convergent variants, if there is more. All data will be merged into the BioRxiv preprint we previously posted.