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Wolfgang Miesbach: From Heparin to Vaccines – The Expanding Biology of Anti-PF4 Immunothrombosis
Wolfgang Miesbach/LinkedIn, Linda Schönborn/Healthcare in Europe, Andreas Greinacher/insuedthueringen
Mar 12, 2026, 20:02

Wolfgang Miesbach: From Heparin to Vaccines – The Expanding Biology of Anti-PF4 Immunothrombosis

Wolfgang Miesbach, Professor of Medicine at Frankfurt University Hospital, shared a post on LinkedIn:

”Anti-PF4 Immunothrombosis: From HIT to VITT and Beyond – Andreas Greinacher and Linda Schönborn (Greifswald University Hospital) delivered one of the standout sessions of the 70th GTH Annual Meeting, tracing the full spectrum of anti-PF4 immunothrombosis:

How PF4 becomes immunogenic:

PF4 (CXCL-4), a positively charged tetrameric protein stored in platelet α-granules, forms immunogenic complexes with polyanions.

This drives FcγRIIA-mediated platelet activation to thrombin generation – thrombosis with thrombocytopenia.

The same mechanism links three clinical entities:

  • Classic HIT — triggered by heparin/PF4 complexes
  • VITT — triggered by adenoviral vector-based COVID-19 vaccines, 5–30 days post-injection, causing thrombosis at unusual sites
  • Spontaneous HIT — autoantibodies activate platelets even without heparin or any polyanion
  • HIT antibodies are not VITT antibodies — they bind distinct epitopes on PF4, a critical distinction for diagnosis and management.

New insights: molecular mimicry plus somatic mutation.

Molecular mimicry between PF4 and adenoviral core protein pVII is the trigger.

In individuals carrying the IGLV3-21*02/03 light chain haplotype (~60% of Caucasians), primary exposure to pVII generates an antibody with an ED motif.

Upon re-exposure, a somatic K31E hypermutation creates an antibody that cross-reacts with PF4 — triggering VITT via a clonal secondary immune response.

These findings just published in N Engl J Med 2026.

Broader implications

This model also illuminates acquired haemophilia post-vaccination, postinfectious APS, ITP in children, posttransfusion purpura, and more.

For future adenoviral vaccine platforms — Ebola, HIV, Zika, Rabies — modifying pVII in the vector could prevent VITT entirely.”

Wolfgang Miesbach: From Heparin to Vaccines - The Expanding Biology of Anti-PF4 Immunothrombosis

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Andreas Greinacher APS bleeding disorders Covid-19 Ebola GTH2026 haemophilia Health Hematology Hemostasis Hemostasis News Hemostasis Today Heparin HIT HIV ITP Linda Schönborn Medicine PF4 Rabies Universitätsmedizin Greifswald Vaccination VITT Zika
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