A bispecific dsDNA x monoclonal antibody construct for clearance of anti-dsDNA IgG in systemic lupus erythematosus

High avidity anti-dsDNA IgG antibodies are believed to play an important ro le in the pathogenesis of the autoimmune disease systemic lupus erythematos us (SLE) and therefore attempts have been made to reduce the concentration of these antibodies in the bloodstream of SLE patients. previously we repor ted the development of an antigen based heteropolymer (AHP), a bispecific c omplex prepared by using the avidin-biotin system to crosslink dsDNA to a m Ab specific for the human erythrocyte (E) complement receptor. Our studies indicated that this AHP could bind anti-dsDNA antibodies to E and facilitat e clearance of these autoantibodies from the circulation of a monkey withou t E destruction. Here we report an improved covalent crosslinking procedure and purification scheme in which the AHP construct is isolated by precipit ation in 50% saturated ammonium sulfate. We used a dsDNA binding dye, PicoG reen, to demonstrate specificity of binding of dsDNA to E via the AHP. The efficacy of the AHP in binding IgG anti-dsDNA antibodies to E was demonstra ted in a sensitive and quantitative assay, based on the time resolved fluor escence properties of europium-labeled anti-human IgG mAbs used to probe th e E. We also used this assay to screen SLE patient and normal plasmas for l evels of anti-dsDNA IgG. The results of this assay correlate very well with the Farr assay, and therefore this approach may be useful in the developme nt of informative and specific assays for a variety of autoantibodies. Trea tment of SLE plasmas with E-AHP under conditions close to physiological led to substantial reductions (greater than or equal to 90%) in anti-dsDNA tit ers. It should be possible to test these new AHP far their ability to targe t and safely remove IgG anti-dsDNA antibodies from the circulation in anima l models. (C) 2001 Elsevier Science B.V: Ail rights reserved.