Vaccine-Induced Immune Thrombocytopenia and Thrombosis (VITT)—Insights from Clinical Cases, In Vitro Studies and Murine Models

An effective worldwide vaccination campaign started and is still being carried out in the face of coronavirus disease 2019 (COVID-19) pandemic. While vaccines are great tools to confront pandemic, predominantly adenoviral vector-based can cause a rare severe adverse effect, termed vaccine-induced immune thrombocytopenia thrombosis (VITT), about 1 100,000 vaccinated individuals. VITT diagnosed 5–30 days post-vaccination clinically characterized by thrombocytopenia, strongly elevated D-dimer levels, platelet-activating anti-platelet factor 4 (PF4) antibodies thrombosis, especially at atypical sites such as cerebral venous sinus and/or splanchnic veins. There striking similarities between heparin-induced (HIT) VITT. Both caused anti-PF4 antibodies, causing platelet leukocyte activation which results massive thrombo-inflammation. However, it be determined why PF4 becomes immunogenic constituent vaccine triggers response. As VITT-like syndromes increasingly reported patients shortly after viral infections, direct virus-PF4 interactions might most relevant. Here we summarize current information hypotheses on pathogenesis address vivo models, murine models for further studies