Thread by @vipintukur

We know that the two Ad-vector based vaccines, #AstraZeneca & #JNJ lead to clot-related complications like cerebral venous sinus thrombosis. We also know these events are referred to as ‘Vaccine induced Thrombotic Thrombocytopenia’ (VITT). But what lead to these complications? 1/

Now a new explanation for VITT seen with vector vaccines. “Vaccine-Induced #Covid19 Mimicry” Syndrome: Splice reactions within the #SARSCoV2 Spike ORF result in ‘Spike protein variants’ that may cause thromboembolic events in patients immunized with vector-based vaccines 2/

These soluble Spike #variants may initiate severe side effects when binding to #ACE2-expressing #endothelial cells in blood vessels 3/

In analogy to the thromboembolic events caused by Spike protein encoded by the SARS-CoV-2 virus, hence the name: 'Vaccine-Induced #Covid19 Mimicry Syndrome' #VIC19M Great work by @rolf_marschalek The preprint 👇 4/
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What is gene splicing? ....a form of RNA processing in which a newly made precursor messenger RNA (pre-mRNA) transcript is transformed into a mature messenger RNA (mRNA). During splicing, #introns (non-coding regions) are removed, & #exons (coding regions) are joined together 5/

All genes encoded by our genome have evolved in the presence of intronic sequences which may have played an important role during evolution to safe-guard coding information, but also to shuffle genetic information in order to create new cellular functions 6/

With very few exceptions, nuclear encoded genes exhibit intronic sequences & primary transcripts are subject to splice reactions to eliminate intronic sequences. For this purpose, consensus splice donor and acceptor sites have evolved 7/

For this purpose, consensus splice donor & acceptor sites have evolved to drive this process that occurs co-transcriptionally in our cell nuclei. The RNA consensus sequences are recognized by RNA/protein complexes (spliceosome). 8/

For nuclear-encoded genes, splicing takes place within the nucleus either during or immediately after transcription. For those eukaryotic genes that contain introns, splicing is usually required in order to create an mRNA molecule that can be translated into protein 9/

Splicing is carried out in a series of reactions which are catalyzed by the spliceosome, a complex of small nuclear ribonucleoproteins (snRNPs). Self-splicing introns, or ribozymes capable of catalyzing their own excision from their parent RNA molecule, also exist 10/

Let’s now see how viral #vector vaccines work? The delivery mechanism means the vaccines send the DNA gene sequences of the spike protein into the cell nucleus rather than the cytosol fluid found inside the cell where the virus normally produces proteins 11/

What happens to the same Spike gene when delivered via an adenoviral system? The adenovirus life cycle includes the infection of cells, uncoating of the virus in the cytosol, entry of the adenoviral DNA into the nucleus, & subsequently gene transcription by the host 12/

All adenoviral systems follow exactly these steps (Ad5/ Ad26/chimp Ad). Thus, the Spike gene will be transcribed inside of the nucleus & subsequently exported as mRNA out of the nucleus. Arriving in the cytosol, the mRNA will again be translated into the Spike protein 13/

And exactly here lies the problem: the viral piece of DNA - deriving from an RNA virus - is not optimized to be transcribed inside of the nucleus. Solely this 3,822 nucleotide long ORF, coding for a primary product of 1274 amino acid long Spike protein 14/

Spike protein contains 6 predicted splice donor and 5 predicted acceptor sites. This problem becomes even more severe when using codon-optimized Spike reading frames (depending on the company: up to 13 splice donor and 11 acceptor sites 15/

Thus, it could well be that the Spike ORF is potentially disrupted by arbitrary splice events when transcribed inside the nucleus 16/

Most of these undesirable splice events would produce shorter protein variants, disrupting the Spike protein upstream of the C-terminally located membrane anchor, and thus, leading to soluble Spike protein variants 17/

In this study, researchers experimentally validated their assumption that potential splice events cause the production of Spike protein variants that have lost the important membrane anchor, resulting in secreted, soluble Spike protein variants 18/

All these results indicate that splice reactions occur and create soluble Spike protein. Soluble Spike protein has been described to cause adverse effects, e.g. a strong infammatory response on endothelial cells 19/

Moreover, nearly all severe cases of #COVID19 suffer from life-threatening thromboembolic events due to the many viruses with Spike surface protein in the blood stream 20/

Soluble Spike variants together with newly built Abs against Spike protein as well as the highly specific blood flow conditions in the central venous sinus of the brain may result in the rare but severe events after vaccination observed with #AstraZeneca vaccine 21/

Noteworthy, the vaccine from #JNJ appears to carry fewer splice donor sequences. This may explain the ~ 10-fold lower incidence of severe side effects with the JNJ vaccine when compared to the #AZ vaccine 22/

So acc to new hypothesis: membrane-anchored & soluble Spike protein variants are produced after the vaccination. When the immune system now starts the production of anti-Spike Abs (days 4–16), these Abs will recognize the membrane-anchored as well as soluble Spike proteins....23/

….however, the soluble fraction of Spike protein variants is disseminated throughout the body and concentrates at various sites of those endothelial cells expressing the ACE2 surface protein 24/

These ACE bound Spike protein variants will become targets of the newly produced antibodies and will cause an ADCC (antibody dependent cell-mediated cytotoxicity) or CDC (complement dependent cytotoxicity) -mediated infammatory reaction involving several immune cells 25/

What are the recommendations? The researchers strongly suggest that the Spike ORF – wild-type or codon optimized - in vector-based vaccines has to be re-optimized to avoid unintended splice reactions & to increase the safety of these pharmaceutical products 26/

Why there is no such risk with the mRNA vaccines? mRNA-based vaccines, such as the jabs developed by #BioNTech/Pfizer and Moderna, deliver the spike’s genetic material to the cell fluid and it never enters the nucleus 27/
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