Parker Ernest T, Healey John F, Barrow Rachel T, Craddock Heather N, Lollar Pete
Winship Cancer Institute, Emory University, Atlanta, GA 30322, USA.
Blood. 2004 Aug 1;104(3):704-10. doi: 10.1182/blood-2003-11-3891. Epub 2004 Apr 8.
Approximately 25% of patients with hemophilia A develop inhibitory antibodies after treatment with factor VIII. Most of the inhibitory activity is directed against epitopes in the A2 and C2 domains. Anti-A2 inhibitory antibodies recognize a 25-residue segment bounded by R484-I508. Several antigenic residues in this segment have been identified, including R484, R489, and P492. The immunogenicity of purified recombinant B domain-deleted (BDD) human factor VIII molecules containing mutations at R484A/R489A or R484A/R489A/P492A was studied in hemophilia A mice. Inhibitory antibody titers in mice receiving the R484A/R489A/P492A mutant, but not the R484A/R489A mutant, were significantly lower than in mice receiving control human BDD factor VIII. The specific coagulant activity and the in vivo clearance and hemostatic efficacy in hemophilia A mice of the R484A/R489A/P492A mutant were indistinguishable from human BDD factor VIII. Thus, the inhibitory antibody response to human factor VIII can be reduced by mutagenesis of a B-cell epitope without apparent loss of function, suggesting that this approach may be useful for developing a safer form of factor VIII in patients with hemophilia A.
约25%的甲型血友病患者在接受凝血因子VIII治疗后会产生抑制性抗体。大多数抑制活性针对A2和C2结构域中的表位。抗A2抑制性抗体识别由R484 - I508界定的一个25个残基的片段。已鉴定出该片段中的几个抗原性残基，包括R484、R489和P492。在甲型血友病小鼠中研究了含有R484A/R489A或R484A/R489A/P492A突变的纯化重组B结构域缺失（BDD）人凝血因子VIII分子的免疫原性。接受R484A/R489A/P492A突变体而非R484A/R489A突变体的小鼠中的抑制性抗体滴度显著低于接受对照人BDD凝血因子VIII的小鼠。R484A/R489A/P492A突变体在甲型血友病小鼠中的比凝血活性、体内清除率和止血效果与对照人BDD凝血因子VIII无差异。因此，通过对B细胞表位进行诱变可降低对人凝血因子VIII的抑制性抗体反应，且功能无明显丧失，这表明该方法可能有助于开发一种更安全的甲型血友病患者用凝血因子VIII形式。
