Characterisation of the conformational changes in platelet factor 4 induced by polyanions: towards in vitro prediction of antigenicity
| Autor: | Andreas Greinacher, Thomas Renné, Stephan Block, Kay E. Gottschalk, Krystin Krauel, Christiane A. Helm, Sven Brandt |
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| Rok vydání: | 2014 |
| Předmět: |
0301 basic medicine
Circular dichroism Antigenicity Polymers Antigen-Antibody Complex Sulfuric Acid Esters 030204 cardiovascular system & hematology Platelet Factor 4 Antibodies Protein Structure Secondary 03 medical and health sciences 0302 clinical medicine Sulfation Tetramer Antigen Polyphosphates Polysaccharides Humans Antigens Heparin Chemistry Circular Dichroism Immunogenicity Hematology Polyelectrolytes Thrombocytopenia In vitro 030104 developmental biology Fondaparinux Biochemistry Protein Multimerization Platelet factor 4 Protein Binding |
| Zdroj: | Thrombosis and Haemostasis. 112:53-64 |
| ISSN: | 2567-689X 0340-6245 |
| Popis: | SummaryHeparin-induced thrombocytopenia (HIT) is the most frequent drug-induced immune reaction affecting blood cells. Its antigen is formed when the chemokine platelet factor 4 (PF4) complexes with polyanions. By assessing polyanions of varying length and degree of sulfation using immunoassay and circular dichroism (CD)-spectroscopy, we show that PF4 structural changes resulting in antiparallel β-sheet content >30% make PF4/polyanion complexes antigenic. Further, we found that polyphosphates (polyP-55) induce antigenic changes on PF4, whereas fondaparinux does not. We provide a model suggesting that conformational changes exposing antigens on PF4/polyanion complexes occur in the hairpin involving AA 32–38, which form together with C-terminal AA (66–70) of the adjacent PF4 monomer a continuous patch on the PF4 tetramer surface, explaining why only tetrameric PF4 molecules express “HIT antigens”. The correlation of antibody binding in immunoassays with PF4 structural changes provides the intriguing possibility that CD-spectroscopy could become the first antibody-independent, in vitro method to predict potential immunogenicity of drugs. CD-spectroscopy could identify compounds during preclinical drug development that induce PF4 structural changes correlated with antigenicity. The clinical relevance can then be specifically addressed during clinical trials. Whether these findings can be transferred to other endogenous proteins requires further studies. |
| Databáze: | OpenAIRE |
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