Objectives: Administration of intravenous Ig (IVIG) is a recognized, safe and efficient mode of immunomodulatory therapy for many autoimmune diseases. Anti-idiotypic antibody binding to pathogenic autoantibodies and hence inhibition of binding to the corresponding antigen is one postulated mechanism of the beneficial effect of IVIG. The aim of this study was to fractionate the anti-beta-2-glycoprotein-I (beta(2)GPI) anti-idiotypic antibodies from a commercial IVIG preparation and use it as a treatment in an experimental antiphospholipid syndrome (APS) mouse model.
Methods: Anti-beta(2)GPI polyclonal antibodies were purified on a beta(2)GPI column. The purified antibodies were bound to CN-Br-activated sepharose and employed for purification of IVIG-anti-anti-beta(2)GPI (anti-idiotypic antibodies), defined as specific intravenous Ig (sIVIG). The idiotype specificities were confirmed by competition assays. The effect of sIVIG in vitro was tested in a trophoblast and choriocarcinoma matrigel/invasion assay (i.e. proliferation and metalloproteinase (MMP)2/MMP9 expression) and in vivo in a fetal loss model of APS.
Results: Anti-beta(2)GPI antibodies inhibited human trophoblast cell invasion in vitro. The function was attributed to the Fab portion of the anti-beta(2)GPI Igs, since beta(2)GPI-related synthetic peptides specific for the Fab part of the anti-beta(2)GPI antibodies neutralized its activity. APS sIVIG fraction reduce human trophoblast invasion in vitro by 560 times more than the whole IVIG compound and improved the MMP2 and MMP9 production by trophoblast cells. sIVIG improved significantly (200 times more) the pregnancy outcome in BALB/c mice passively infused with anti-beta(2)GPI antibodies, in comparison to treatment with IVIG (P < 0.02).
Conclusions: Based on the current results, we propose that APS sIVIG may be considered as potential specific therapeutic safe compound for developing a treatment for APS patient's early fetal loss.