Abstract
Introduction: The presence of autoantibodies targeting cell adhesion molecules at paranodes (CNTN1, Nfasc155, Caspr1) has recently been associated with subgroups of patients with chronic inflammatory demyelinating polyneuropathy (CIDP). These novel biomarkers had important clinical benefits and helped both the diagnosis and the treatment orientation of the patients. We recently demonstrated that anti-Nfasc155 IgG4 induces paranodal disorganization and leads to conduction alterations and gait abnormalities in animal models. These data critically helped demonstrating the pathogenicity of these antibodies. Because IgG4 are known to undergo exchange of their variable, we here investigated whether valency modulates the pathogenicity of anti-Nfasc155 IgG4.Methods: IgG4 were purified using selective purification beads (CaptureSelect) from the plasma of two CIDP patients. Papain and IdeS digestion were performed using Pierce's Fab preparation kit (Thermofisher) and FragIT kit (Genovis) according to manufacturer's protocols. For intraneural injections, Lewis rats were anesthetized and sciatic nerve were injected with 10 μg of antibody. Passive transfer models were performed as previously described (1).Results: To demonstrate this, we have digested anti-Nfasc155 IgG4 with papain or IdeS to generate monovalent Fab or bivalent F(ab')2,respectively. We first assured that the enzymatic cleavage did not affect the affinity of Fab and F(ab')2 for Nfasc155, then we injected the antibodies in neonatal animals to test their impact on paranode formation. Both native IgG4 and F(ab')2 antibodies potently abrogated paranode formation. By contrast, monovalent Fab antibodies did not have pathologic consequences. Also, only native IgG4 and F(ab')2 antibodies were able to induce Nfasc155 aggregation at adherens junctions.Conclusions: Our results demonstrate that the bivalency of anti-Nfasc155 IgG4 dictates their pathogenicity. This also highlighted that strategies aiming at rendering IgG4 monovalent may be of benefits.References1. Manso C, Querol L, Lleixa C, et al. Anti-Neurofascin-155 IgG4 antibodies prevent paranodal complex formation in vivo. Journal of Clinical Investigation 2019; 129(6): 2222-36.