Reverse engineering of recombinant vaccine-induced thrombotic thrombocytopenia (rVITT) antibodies (Abs) and potential interaction with the heparin-binding region of platelet factor 4 (PF4) that is facilitated by an amino acid exchange (K31E mutation) in the paratope region. COVID-19, coronavirus disease 2019; E, leucine; K, lysine; R, arginine; VH, immunoglobulin heavy chain variable region; VL, immunoglobulin light chain variable region. Figure created using bioRender software.