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Spillover Squirrel and AI Art

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Brief overview

A single somatic mutation turns an anti-adenovirus antibody into the platelet attack that causes VITT.

  1. One amino acid change flips the antibody to selfK31E in the light chain makes the paratope negative, so it binds PF4 tightly and P7 less.
  2. Two hits explain a one-in-a-million reactionYou need the common IGLV3-21 light chain allele and the uncommon somatic hypermutation on top of it.
  3. A wasp turned a virus into a delivery systemBrachovirus particles carry wasp genes, including the PTP that sterilizes the caterpillar host.
Executive Summary AI
  • This is TWIV episode 1299, recorded on February 20th, 2026, with Vincent Racaniello hosting Rich Condit in Austin, Alan Dove in Western Massachusetts and Brianne Barker in Madison, New Jersey.0:11
  • The news block covers a Nature piece by Alexandra Witts on the U.S. repealing the endangerment finding that climate change is a public threat, with EPA head Lee Zeldin arguing it saves money and health groups suing, NIAID dropping pandemic preparedness and biodefense, and the FDA reversing course on Moderna's roughly billion-dollar mRNA flu shot after Vinay Prasad refused to review it.9:02
  • The first paper, a New England Journal of Medicine report from Jingjing Wang, Linda Schonborn, Tom Gordon and Andreas Greinacher, asks why about one person in a million develops vaccine-induced immune thrombocytopenia and thrombosis after the ChAdOx or Ad26 adenovirus-vectored vaccines, where the anti-platelet-factor-4 antibodies are unusually monoclonal or oligoclonal.16:28
  • In 21 VITT patients the antibodies shared an ED motif in the heavy chain and an IGLV3-21*02/03 light chain carrying one somatic hypermutation, lysine 31 to glutamic acid, which makes the paratope negative so it binds positively charged PF4 hard while losing affinity for a conserved 15-mer epitope on the adenoviral core protein P7; the recombinant antibodies dropped platelets 79% and caused thrombo42:18
  • The second paper, a PNAS study from Hongshuai Gao and Mujuan Guo, shows parasitic castration: the wasp Cotesia vestalis delivers a brachovirus-borne pseudophosphatase, CVBV22-9, that binds the cell cycle checkpoint protein Rad9A and drives testicular apoptosis in diamondback moth larvae from 7% in unparasitized animals to 80-95% in parasitized ones, with knockdown of 89% restoring testis size.52:49
Key Quote
“So monoclonal means that one B cell made those antibodies.”
— Brianne Barker18:12
Key Quote
“Low platelets, low circulating platelets, and yet clots.”
— Rich Condit19:00
Key Quote
“Scientists know how to say, oops, I was wrong.”
— Vincent Racaniello52:20