In vivo inhibition of antiphospholipid antibody-induced pathogenicity utilizing the antigenic target peptide domain I of beta2-glycoprotein I: proof of concept

J Thromb Haemost. 2009 May;7(5):833-42. doi: 10.1111/j.1538-7836.2009.03316.x. Epub 2009 Feb 12.


Summary objectives: In the antiphospholipid syndrome (APS), the immunodominant epitope for the majority of circulating pathogenic antiphospholipid antibodies (aPLs) is the N-terminal domain I (DI) of beta(2)-glycoprotein I. We have previously shown that recombinant DI inhibits the binding of aPLs in fluid phase to immobilized native antigen, and that this inhibition is greater with the DI(D8S/D9G) mutant and absent with the DI(R39S) mutant. Hence, we hypothesized that DI and DI(D8S/D9G) would inhibit aPL-induced pathogenicity in vivo.

Methods: C57BL/6 mice (n = 5, each group) were injected with purified IgG derived from APS patients (IgG-APS, 500 microg) or IgG from normal healthy serum (IgG-NHS) and either recombinant DI, DI(R39S), DI(D8S/D9G), or an irrelevant control peptide (at 10-40 microg). Outcome variables measured were femoral vein thrombus dynamics in treated and control groups following standardized vessel injury, expression of vascular cell adhesion molecule-1 (VCAM-1) on the aortic endothelial surface, and tissue factor (TF) activity in murine macrophages.

Results: IgG-APS significantly increased thrombus size as compared with IgG-NHS. The IgG-APS thrombus enhancement effect was abolished in mice pretreated with recombinant DI (P <or= 0.0001) and DI(D8S/D9G) (P <or= 0.0001), but not in those treated with DI(R39S) or control peptide. This inhibitory effect by DI was dose-dependent, and at lower doses DI(D8S/D9G) was a more potent inhibitor of thrombosis than wild-type DI (P <or= 0.01). DI also inhibited IgG-APS induction of VCAM-1 on the aortic endothelial surface and TF production by murine macrophages.

Conclusion: Our findings in this proof-of-concept study support the development of recombinant DI or the novel variant DI(D8S/D9G) as a potential future therapeutic agent for APS.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Antiphospholipid / immunology*
  • Antibodies, Antiphospholipid / physiology
  • Enzyme-Linked Immunosorbent Assay
  • Macrophages, Peritoneal / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Thromboplastin / metabolism
  • beta 2-Glycoprotein I / chemistry
  • beta 2-Glycoprotein I / metabolism*


  • Antibodies, Antiphospholipid
  • beta 2-Glycoprotein I
  • Thromboplastin