Thrombogenic properties of antiphospholipid antibodies do not depend on their binding to β2 glycoprotein 1 (β2GP1) alone

Abstract

Immunization of mice with beta2glycoprotein 1 (beta2GP1) induces production of antiphospholipid (aPL) antibodies, which were shown to have thrombus enhancing properties in an experimental mouse model, indicating that these antibodies are thrombogenic in vivo. To determine whether the thrombogenic effect of murine antiphospholipid antibodies is due to their aPL or their anti-beta2GP1 activity, we injected mice with murine monoclonal anticardiolipin (aCL) and anti-beta2GP1 antibodies. Effects of these antibodies on thrombus formation, was evaluated utilizing a mouse model which enables kinetics of thrombus formation to be studied. The results of this study showed that the size of the thrombus in animals injected with murine aCL antibodies was larger than that in control groups. There was no difference in thrombus kinetics between anti-beta2GP1 injected mice and controls, suggesting that the thrombogenic effect of aPL antibodies is not related to their anti-beta2GP1 activity alone. Mice receiving monoclonal antibodies with both aCL and anti-beta2GP1 activity, also increase thrombus size when compared with controls. These data indicate that murine aCL, but not anti-beta2GP1, antibodies are thrombogenic in vivo.

Antiphospholipid antibodies induced in mice by immunization with a cytomegalovirus‐derived peptide cause thrombosis and activation of endothelial cells in vivo

“…These antibodies had characteristics similar to those of the autoimmune human aPL, and their binding to PL was enhanced by addition of ␤ 2 GPI (13). These findings were reproduced by other investigators (14,15), and ␤ 2 GPI-induced aPL were shown to be pathogenic in certain strains of mice (16)(17)(18)(19).…”

“…␤ 2 GPI-induced aPL have been shown to be pathogenic in certain strains of mice, causing intrauterine fetal death, thrombocytopenia, and thrombosis (15)(16)(17)(18)(19). Induction of aPL is not dependent on immunization with the whole ␤ 2 GPI molecule.…”

Annexin A2 is involved in antiphospholipid antibody-mediated pathogenic effects in vitro and in vivo

“…This monoclonal Ab was shown to be thrombogenic and to activate ECs in previous studies. 40 Thrombus size was significantly larger in A2 ϩ/ϩ mice injected with 4C5 compared with same type of mice injected with MuMoAbC (P ϭ .002) or with anti-A2 MoAb (P ϭ .017; Figure 4B). The thrombogenic effects of 4C5 were significantly diminished in A2 Ϫ/Ϫ mice (P ϭ .005).…”

“…40 The 4C5 was shown to bind to cardiolipin in a ␤ 2 GPI-dependent fashion, to have lupus anticoagulant and thrombogenic activity, and to activate ECs in previous studies. 40 The purified IgG was dialyzed against Tris-buffered saline, and the concentration of the protein was determined by the Bradford method. 39 A murine anti-A2 monoclonal Ab (anti-A2 MoAb) was used in some experiments (clone 5; BD Biosciences).…”

Antiphospholipid Syndrome - An Evolving Story of a Multisystemic Disease

“…Gharavi et al in 1999 synthesized a 15 amino acid peptide, GDKV, which spanned an area of the fifth domain of  2 GPI known to be a major PL-binding site of the molecule, and demonstrated the peptide's ability to induce pathogenic aPL and anti- 2 GPI antibody production in mice [48]. A monoclonal antibody with aPL and anti- 2 GPI activity generated from these GDKVimmunized mice was shown to be pathogenic using in vivo models for thrombus enhancement and microcirculation [49]. The resulting search for candidate peptides in microorganisms that exhibited functional and sequence similarity to the PL-binding domain of  2 GPI produced the peptides TIFI and VITT from cytomegalovirus (CMV), TADL from adenovirus (AdV) and SGDF from Bacillus subtilis.…”