Bloom Lab Profile picture
Jun 24, 2021 5 tweets 2 min read Read on X
I am getting lots of questions if my pre-print about some #SARSCoV2 sequences that were removed from Sequence Read Archive tell us anything about lab accident versus natural zoonosis.

I posted summary of pre-print below, but did not directly address this point explicitly (1/n)
The answer is NO. The people using it to strongly support either argument are those that have become so emotionally invested in their opinion that they have lost the ability to analyze anything objectively outside of the framework of that argument. (2/n)
What the pre-print does imply is as follows:

First, there may be additional relevant data in obscure locations that aren't the places where we are accustomed to looking (e.g., on the Google Cloud, in table 1 of a paper on diagnostics, etc): (3/n)
Second, in my opinion, anybody doing phylogenetics on early #SARSCoV2 sequences from China should spend as much time on metadata as algorithms. Sequences in databases may be non-representative. Sequences collected in Guangdong might be from infections from Wuhan. Etc. (4/n)
Third, preprint provides modestly more evidence for progenitor being in clade A (not market clade), & substantially more evidence it might have T at site 29095. However, current inferences are likely based on incomplete data. @sergeilkp says it best: (5/n)

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More from @jbloom_lab

Aug 20
In new study led by Bernadeta Dadonaite, we measure how spike mutations affect function & antigenicity of spike of KP.3.1.1 strain of SARS-CoV-2.

Sheds light on how key neutralizing epitopes are changing & importance of RBD up/down motion.

biorxiv.org/content/10.110…
We examined spike of KP.3.1.1, a strain from late 2024 / early 2025 similar to current variants

KP.3.1.1 & other recent variants have >60 spike amino-acid mutations relative to early pandemic strains, as spike has evolved at extraordinary rate of >10 mutations/year on avg Image
We previously developed pseudovirus deep mutational scanning (), which uses non-replicative viral particles to safely study spike mutations.

Here we used approach to measure how mutations to KP.3.1.1 spike affect five phenotypes, as shown below. pubmed.ncbi.nlm.nih.gov/36868218/Image
Read 12 tweets
May 27
In new study led by @timcyuu, we measure how mutations to H3 flu HA affect cell entry, stability & antibody escape

We find pleiotropic effects of mutations on these phenotypes shape evolution: epistasis alleviates cell-entry but not stability constraints

biorxiv.org/content/10.110…
We used pseudovirus deep mutational scanning to characterize all mutations to a recent H3N2 HA. This approach uses virions that can only undergo one round of cell entry & so are not pathogens capable of causing disease.

All measurements available here: dms-vep.org/Flu_H3_Massach…
As can be seen below, constraint due to mutational impacts on cell entry are widely distributed across HA including receptor-binding pocket and fusion peptide. But mutational constraint due to HA stability is concentrated at trimer and HA1-HA2 interface. Image
Read 8 tweets
Mar 12
In study led by Cassie Simonich & T McMahon, we quantify antigenic evolution of RSV F. Important because:

1⃣ RSV top cause of infant hospitalization in USA

2⃣ New antibodies & vax can prevent hospitalizations

3⃣ But will virus evolution erode efficacy?

biorxiv.org/content/10.110…
RSV has high burden in infants: top cause of infant hospitalization in USA, 2nd-leading cause of infant mortality globally

A monoclonal antibody (nirsevimab) recently recommended for infants born in USA in RSV season. It prevents hospitalizations

pubmed.ncbi.nlm.nih.gov/38457312/
RSV vaccines also now approved to protect infants (via maternal vaccination) & elderly

But some viruses evolve to erode antibodies and vaccines

Will RSV do same? Worryingly, a Regeneron antibody failed phase 3 trials due to resistance in some RSV strains
pubmed.ncbi.nlm.nih.gov/32897368/
Read 11 tweets
Jan 21
In new study, we find dramatic differences in specificities of serum neutralizing antibodies in infants w single infection by a recent SARS-CoV-2 strain versus adults/children imprinted by an early viral strain.

biorxiv.org/content/10.110…
As background, immune response to a virus is “imprinted” by first exposure, since later exposures to new viral strains often activate pre-existing B-cells.

For SARS-CoV-2, most people globally imprinted by an early viral strain from either vaccination or infection in 2020-2021.
However, small but growing fraction of population has instead been imprinted by more recent viral strain.

Specifically, we compared adults/children imprinted by original vaccine then infected w XBB* strain in 2023 vs infants only infected w XBB* in 2023. Image
Read 9 tweets
Nov 21, 2024
I’ve updated SARSCoV2 antibody-escape calculator w new deep mutational scanning data of @yunlong_cao @jianfcpku

My interpretation: antigenic evolution currently constrained by pleiotropic effects of mutations on RBD-ACE2 affinity, RBD up-down position & antibody neutralization
First, the updated escape calculator is at

As shown below, it is remarkable how much antigenicity of RBD has changed over last 4 yrs. jbloomlab.github.io/SARS2-RBD-esca…Image
Updated data for calculator from this paper by @yunlong_cao’s group (nature.com/articles/s4158…), described in this thread by first author @jianfcpku:
x.com/jianfcpku/stat…

Calculator show how much mutations at each RBD site escape binding by set of neutralizing antibodies
Read 13 tweets
Nov 16, 2024
@Nucleocapsoid @HNimanFC @mrmickme2 @0bFuSc8 @PeacockFlu @CVRHutchinson Good observations. See also this thread posted by @SCOTTeHENSLEY:

I have added a few notes to the bottom of that thread.

To recap here:bsky.app/profile/scotte…
@Nucleocapsoid @HNimanFC @mrmickme2 @0bFuSc8 @PeacockFlu @CVRHutchinson @SCOTTeHENSLEY To add to thread linked above, human British Columbia H5 case has a HA sequence (GISAID EPI_ISL_19548836) that is ambiguous at *both* site Q226 and site E190 (H3 numbering)

Both these sites play an important role in sialic acid binding specificity
@Nucleocapsoid @HNimanFC @mrmickme2 @0bFuSc8 @PeacockFlu @CVRHutchinson @SCOTTeHENSLEY If you are searching literature, these sites are E190 and Q226 in H3 numbering, E186 and Q222 in mature H5 numbering, and E202 and Q238 in sequential H5 numbering (see: )dms-vep.org/Flu_H5_America…
Read 6 tweets

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