Scheiflinger F, Dockal M, Rosing J, Kerschbaumer R J
Baxter BioScience, Department of Discovery Research and Technical Assessment, Vienna, Austria.
J Thromb Haemost. 2008 Feb;6(2):315-22. doi: 10.1111/j.1538-7836.2007.02868.x. Epub 2007 Dec 10.
Factor VIIIa (FVIIIa) binds to activated FIX and enhances the activation of FX by several orders of magnitude. Deficiency of FVIII causes the bleeding disorder hemophilia A and is treated by i.v. infusion of FVIII concentrates.
To explore whether or not FVIII activity can be supplied by alternative molecules, e.g. molecules with FIXa-binding activity.
Conventional hybdridoma technology was used to discover antibodies exhibiting FVIII-like activity.
We identified a series of antibodies specific for human FIX that mimicked the stimulatory effect of FVIIIa on FIXa. Upon binding to human FIXa, these antibodies enhanced the protease activity of FIXa towards its natural substrate FX about tenfold. A similar enhancement was also achieved with 5 pm FVIIIa (i.e. 16 mU mL(-1) or 1.6% activated FVIII). Procoagulant activity of these anti-FIXa antibodies was observed in model systems containing purified proteins as well as in plasma.
Our findings show that FVIII can, at least partially, be replaced by an unrelated molecule. Procoagulant antibodies might potentially aid the development of an FVIII substitute for hemophilia A treatment.
凝血因子Ⅷa（FVIIIa）与活化的FIX结合，并将FX的活化增强几个数量级。FVIII缺乏会导致出血性疾病甲型血友病，通过静脉输注FVIII浓缩物进行治疗。
探讨FVIII活性是否可以由替代分子提供，例如具有FIXa结合活性的分子。
使用传统的杂交瘤技术来发现具有FVIII样活性的抗体。
我们鉴定出一系列对人FIX特异的抗体，它们模拟了FVIIIa对FIXa的刺激作用。这些抗体与人FIXa结合后，将FIXa对其天然底物FX的蛋白酶活性提高了约10倍。5皮摩尔的FVIIIa（即16 mU mL(-1)或1.6%活化FVIII）也实现了类似的增强效果。在含有纯化蛋白的模型系统以及血浆中均观察到了这些抗FIXa抗体的促凝活性。
我们的研究结果表明，FVIII至少可以部分地被一种不相关的分子替代。促凝抗体可能有助于开发用于治疗甲型血友病的FVIII替代物。
