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Those who follow me know that alarmism isn't my style. But the new UK variant does have me a bit concerned. I'm not qualified to critically assess changes in transmissibility, but deletions of H69/V70 do seem to partially evade Abs. So it's worth a primer on how the immune system
handles such changes, and how memory T and B cells become really important. First, some evidence that these variants may matter. In an immunocompromised COVID patient treated with convalescent plasma, the delta 69-70 variant (+ D796H) was selected for. https://www.medrxiv.org/content/10.1101/2020.12.05.20241927v1
It also partially evaded other convalescent plasma samples. The evasion wasn't complete, but one can imagine how this could take hold in someone who didn't mount a great Ab response. Thankfully, immune memory is multilayered. If a pathogen gets past the first line of defense...
which are pre-existing antibodies made by plasma cells, then memory B and T cells can kick in. Memory T cells recognize a bunch of different parts (peptides) of viral proteins, and the virus can't escape them all. There have been many nice studies on T cell memory after infection
e.g. by @profshanecrotty, @PepperMarion, @marcus_buggert, many others. Looks pretty good--much better than the cross-reactive T cells that exist prior to COVID in some people. For vaccines it is less comprehensive, but when examined, it also looks decent https://www.nature.com/articles/s41586-020-2798-3
These memory T cells can rapidly respond and clear infected cells before things get out of hand. There are also memory B cells, which produce a lot more antibodies if the pathogen slips past those that are already there. Work by our group in collaboration with Mike Diamond's
showed that these cells are well-positioned to deal with viral escape mutants. These memory B cells are in fact selected to be diverse, presumably for exactly these circumstances. https://www.cell.com/immunity/fulltext/S1074-7613(20)30395-2?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS1074761320303952%3Fshowall%3Dtrue https://pubmed.ncbi.nlm.nih.gov/22162833/
The upshot is that for at least common coronaviruses, even if the virus slips past the antibodies and productively infects, there is a short duration of viral shedding and few symptoms. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2271881/
All this to say that I don't think we should be in panic mode. But I do think we need to be thinking about how/when to update the vaccines, and really thinking about the regulatory framework to do so.
