Platelet factor 4 – adenoviral DNA complex (PF4-AdV DNA)

Platelet factor 4 (PF4) is a positively charged CXC chemokine (CXCL4) stored in the alpha-granules of platelets and released upon activation (UniProt P02776). In the context of certain adenovirus-vectored vaccines, PF4 can bind to negatively charged components, including the adenoviral hexon protein or potentially the double-stranded DNA (dsDNA) payload, forming a stable complex (Baker et al., 2021, Science Advances). This complex acts as a neoantigen that triggers the production of high-affinity IgG autoantibodies in susceptible individuals (Greinacher et al., 2021, NEJM). These antibodies bind to PF4, and the resulting immune complexes cross-link FcγRIIa receptors on platelets, causing massive activation, prothrombotic microparticle release, and platelet consumption (Schultz et al., 2021, NEJM). This process leads to Vaccine-induced Immune Thrombotic Thrombocytopenia (VITT), characterized by severe thrombosis, often in unusual sites like the cerebral venous sinuses, alongside low platelet counts (Cines & Bussel, 2021, NEJM). While the complex itself is not a therapeutic target, understanding its formation is vital for vaccine safety and for directing treatments such as intravenous immunoglobulin (IVIG) and non-heparin anticoagulants (Thaler et al., 2021, Blood).

Other names

PF4-adenovirus complexVITT neoantigenPF4-dsDNA complexCXCL4-adenovirus complexPF4-hexon complex

Formation of a pathogenic neoantigen complex that triggers the production of high-affinity IgG autoantibodies, which subsequently cross-link FcγRIIa receptors on platelets to cause massive activation and consumption.