Background/Purpose: Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by high titers of multiple autoantibodies. Of those, anti-DNA antibodies play a key role in the pathogenesis of lupus nephritis by cross reacting with renal antigens. Previously, we generated a panel of anti-DNA antibodies from the murine PL9-11 anti-DNA mAb (IgG3), which share identical variable regions of both heavy and light chains but differ in their heavy chain constant region. We demonstrated that the binding affinity of the PL9-11 mAbs to self-antigens (including renal antigens) is isotype-dependent. The present study was designed to further investigate the cross reaction between anti-DNA antibodies and renal antigens, by identifying a peptide mimic that can bind to multiple anti-DNA isotypes.

Methods: A phage display library was used for peptide selection, and identified a 12-mer peptide, ALWPPNLHAWVP or “ALW”. The specificity and kinetics of binding affinity of ALW to anti-DNA isotypes were determined by ELISA and surface plasmon resonance. Inhibition and cell surface ELISAs, flow cytometry, and glomerular binding assays were performed to evaluate how well ALW inhibits murine and human anti-DNA antibodies in binding to glomerular antigens in vitro and ex vivo.

Results: The ALW peptide exhibits differential binding affinity to the PL9-11 anti-DNA antibodies in the order of IgG2b>IgG2a>IgG3=IgG1. Pre-incubation with the ALW peptide significantly reduced the binding of anti-DNA IgGs to dsDNA, laminin, matrigel, mesangial cells, and isolated glomeruli. Moreover, the inhibition by ALW of anti-DNA binding was isotype-dependent. Alanine replacement studies and phage binding assays confirmed the specificity of the amino acid sequence in the binding of ALW to the PL9-11 panel. Finally, ALW significantly inhibited the binding of sera from MRL/lpr and B6.Sle1/3 mice and patients with active SLE to nuclear and glomerular antigens.

Conclusion: The ALW peptide significantly inhibits the binding of nephritogenic anti-DNA antibodies and human/mouse lupus sera to multiple self-antigens, presumably by mimicking their antigenic properties. The ALW peptide or its derivatives may potentially be a useful approach in the treatment of lupus nephritis and other autoantibody-mediated disease manifestations, by inhibiting the binding of polyclonal anti-DNA antibodies to their in vivo targets.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-peptide-mimic-inhibits-the-cross-reaction-of-anti-dna-antibodies-with-glomerular-antigens/