Complex formation with nucleic acids and aptamers alters the antigenic properties of platelet factor 4

• Published in: Blood 2013-07, Vol.122 (2), p.272-281
• Main Authors: Jaax, Miriam E., Krauel, Krystin, Marschall, Thomas, Brandt, Sven, Gansler, Julia, Fürll, Birgitt, Appel, Bettina, Fischer, Silvia, Block, Stephan, Helm, Christiane A., Müller, Sabine, Preissner, Klaus T., Greinacher, Andreas
• Format: Article
• Language: English
• Subjects: Animals; Antibodies - immunology; Antibodies - metabolism; Aptamers, Nucleotide - chemistry; Aptamers, Nucleotide - metabolism; Base Pairing; Base Sequence; Blood Platelets - metabolism; DNA - chemistry; DNA - metabolism; Heparin - pharmacology; Humans; Macromolecular Substances - metabolism; Mice; Molecular Sequence Data; Nucleic Acid Conformation; Nucleic Acids - chemistry; Nucleic Acids - metabolism; Platelet Activation - immunology; Platelet Factor 4 - immunology; Platelet Factor 4 - metabolism; Polymers; Protein Binding - drug effects; RNA - chemistry; RNA - metabolism; Thrombosis and Hemostasis
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2013-01-478966

The tight electrostatic binding of the chemokine platelet factor 4 (PF4) to polyanions induces heparin-induced thrombocytopenia, a prothrombotic adverse drug reaction caused by immunoglobulin G directed against PF4/polyanion complexes. This study demonstrates that nucleic acids, including aptamers, also bind to PF4 and enhance PF4 binding to platelets. Systematic assessment of RNA and DNA constructs, as well as 4 aptamers of different lengths and secondary structures, revealed that increasing length and double-stranded segments of nucleic acids augment complex formation with PF4, while single nucleotides or single-stranded polyA or polyC constructs do not. Aptamers were shown by circular dichroism spectroscopy to induce structural changes in PF4 that resemble those induced by heparin. Moreover, heparin-induced anti-human–PF4/heparin antibodies cross-reacted with human PF4/nucleic acid and PF4/aptamer complexes, as shown by an enzyme immunoassay and a functional platelet activation assay. Finally, administration of PF4/44mer–DNA protein C aptamer complexes in mice induced anti–PF4/aptamer antibodies, which cross-reacted with murine PF4/heparin complexes. These data indicate that the formation of anti-PF4/heparin antibodies in postoperative patients may be augmented by PF4/nucleic acid complexes. Moreover, administration of therapeutic aptamers has the potential to induce anti-PF4/polyanion antibodies and a prothrombotic diathesis. •PF4 binds to nucleic acids and thereby exposes the epitope to which anti-PF4/heparin antibodies bind.•PF4/aptamer complexes can induce an immune response resembling heparin-induced thrombocytopenia.