Thread by @Ayjchan

It makes less and less sense that the WIV didn’t even mention the unique furin cleavage site insertion when they described SARS2 for the first time in their @Nature paper. They had a pipeline for looking for these cleavage sites in rare novel SARSrCoVs. H/t @canardbruno @ydeigin

https://twitter.com/canardbruno/status/1270083289236332546

More recent discussion here:

https://twitter.com/ayjchan/status/1391765871706746881

Before we knew WIV and collaborators had plans to insert novel cleavage sites into novel SARSrCoVs, we were comparing the WIV paper to other first papers on SARS2.

Now that we know WIV was aware and on the lookout for these functional cleavage sites, that comparison is moot.

https://twitter.com/ayjchan/status/1403068490681139209

If I were a legendary SARSrCoV expert looking for rare SARSrCoVs with rare cleavage sites in the spike, and one of these unicorns showed up in my city (naturally), I would’ve written up a section on this novel feature and pointed it out in a figure in my keystone paper in Nature.

It makes no sense that they would implement a cutoff right before this feature and not even mention it once in the entire paper or its supplementary material.

https://twitter.com/ayjchan/status/1274459475492196353

It literally would’ve fit in that figure above if they just filled in the 10 letters in the last row. No need to make the figure bigger or reformat it.

Gratuitous unicorn gif because.

https://twitter.com/Ayjchan/status/1391942103761145860

My best guess is there was a decision not to mention the FCS.
“Major differences in the sequence of the S gene of 2019-nCoV are the 3 short insertions in the NTD as well as changes in 4 out of 5 of the key residues in the receptor-binding motif compared with the sequence of SARS”

They had also directly compared the spike of SARS2 to that of RaTG13 so the FCS insertion would have stood out even more prominently.