Charakterisierung von Faktor-VIII-Antikörperepitopen mit Faktor-VIII-Peptid-Bibliotheken

 

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Zusammenfassung

Etwa 30% der Patienten die an schwerer Hämophilie A leiden, entwickeln als Komplikation einer Substitutionstherapie gegen Faktor VIII gerichtete Antikörper, die die prokoagulatorische Aktivität von intravenös injizierten FVIII-Proteinen neutralisieren. In der Regel werden verschiedene Epitope auf dem FVIII-Molekül durch diese Antikörper gebunden. Die detaillierte Struktur dieser Epitope ist unbekannt. In dieser Studie werden Epitope auf dem Faktor-VIII-Molekül mit Hilfe festphasengebundener Peptid-Arrays identifiziert, auf denen die Aminosäuresequenz des FVIII in Oligopeptiden dargestellt wird. Die Bindung von FVIII-Antikörpern an bestimmte Peptidsequenzen zeigt potenzielle Epitopstrukturen. FVIII-Antikörper von Inhibitorpatienten und gesunden Blutspendern werden zurzeit mit dieser Methode charakterisiert. Identifizierte Epitope können zur Entwicklung neuer Therapiekonzepte führen, die dazu dienen, eine Hemmkörperentwicklung zu vermeiden bzw. bereits entstandene Hemmkörper besser zu eliminieren. Als Teilprojekt des Konsortiums »Hämophilie A« wird im Rahmen des Gesamtvorhabens »Genotyp-Phänotyp-Korrelation bei der Hämophilie A« untersucht, ob die Epitopcharakteristik mit dem Typ und der Position der FVIII-Genmutationen korreliert sowie Zusammenhänge zwischen Epitop und klinischem Verlauf der Krankheit bestehen. Zusätzlich wird der Einfluss der Epitope auf den therapeutischem Effekt und Erfolg der Immuntoleranzinduktion untersucht.

Summary

Approximately 30% of patients suffering from severe haemophilia A develop antibodies against factor VIII (FVIII) neutralizing the effect of the pro-coagulant activity of intravenously injected FVIII as a complication of replacement therapy. Generally, various epitopes on the FVIII molecule are bound by these antibodies. The detailed structure of such epitopes is unknown. In this study epitopes on the FVIII molecule are identified using solid phase bound peptide arrays carrying the whole aminoacid sequence of FVIII as small oligopeptides. The binding of FVIII antibodies by specific peptide sequences on the array indicates potential epitopes. FVIII antibodies of inhibitor patients and healthy blood donors are currently investigated by this method. Identified epitopes may lead to new concepts in therapy aiming at avoidance of inhibitor formation or improvement of inhibitor eradication. As participant of the ‘haemophilia A’ consortium dealing with genotype/phenotype correlation in haemophilia A we investigate, if the site or type of the mutation correlates with the epitopes, and if there is any relation between epitopes and clinical course. Furthermore, the influence of epitopes on therapeutical effects and the outcome of immune tolerance induction is under scrutinity.

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