However, even when patients are treated with either immunotherapy, 20% remain severely disabled and 5% die8

However, even when patients are treated with either immunotherapy, 20% remain severely disabled and 5% die8. and disruption of axo-glial junction3,4. These result in motor nerve conduction failure and muscle weakness. Although pathogenic antibodies have yet to be determined in AIDP, autopsy studies showed that complement activation at the outer surface of Schwann cells is probably subsequent to IgG antibodies binding to targets on Schwann cells5. Plasma exchange and intravenous immunoglobulin (IVIG) are effective for treating GBS most likely due to the fact that plasma exchange removes IgG and complement, and IVIG can neutralize pathogenic IgG autoantibodies and inhibit complement activation6,7. However, even when patients are treated with either immunotherapy, 20% remain severely disabled and 5% die8. More effective treatments are required based on the understanding of the immunopathogenesis. Immunoglobulin G-degradingenzyme ofStreptococcus pyogenes(IdeS), which cleaves IgG antibodies into F(ab)2and Fc fragments, is secreted byS. pyogenes9. IdeS is one of the virulence factors for the bacterium, which helps it to escape from the hosts immunological defenses, such as phagocytosis and complement activation, by removing the Fc region from IgG targeting, e.g. bacterial surface antigens. By taking advantage of this action, IdeS has been shown to have therapeutic effects in several autoimmune disease models mediated by pathogenic autoantibodies10. IdeS seems to be a promising treatment because the cleavage of IgG antibodies inhibits complement activation subsequent to the formation of the immune-complex. Here we demonstrate that IdeS blocked complement activation mediated by anti-ganglioside IgG antibodiesin vitro. == Results == == IdeS efficiently cleaved IgG and blocked complement activation mediated SR1001 by anti-GM1, anti-GD1a and anti-GQ1b IgG antibodies == The established assays demonstrated the binding of autoantibodies to each ganglioside and the deposition of active complement component. The detection of Fc domain was obscured due to cleavage by IdeS and subsequent rinsing out. Nevertheless F(ab)2remained to bind stably to the ganglioside coating on the microtiter plates (Fig. 1A and2A). The clearance of Fc depended on the concentration of IdeS (Fig. 1B) as well as the time after the addition of IdeS to the serum (Fig. 1C). The cleaving effect emerged in a few minutes and reached the SR1001 maximum in one hour. IdeS cleaved all the anti-GM1, anti-GD1a and anti-GQ1b IgG antibodies (Fig. 1D). Fc deposition was degraded by IdeS (10 g/ml), whereas F(ab)2deposition remained unaltered. Thus, the subsequent complement deposition mediated by anti-ganglioside IgG autoantibodies was inhibited by IdeS, resulting in the blocking of the C3 deposition (Fig. 2B). The blocking effect depended on the concentration of IdeS as well as the clearance of Fc (Fig. 2C). In contrast, IdeS did not affect the binding of CD40 anti-GM1 IgM antibodies (Fig. 1E). == Figure 1. == (A) Schema of IdeS treatment for binding of autoantibodies. Anti-ganglioside antibodies in the diluted patients sera bind to the ganglioside coating on the microtiter plates. IdeS cleaves IgG antibodies SR1001 into F(ab)2and Fc fragments. Peroxidase-conjugated anti-human IgG (Fc) does not bind to the F(ab)2residue and does not work as the luminescent substrate in IdeS treated plates. (B) Concentration dependence of IdeS treatment. The representative change of GM1-IgG binding depends on its concentration. The clearance of IgG (Fc) accumulated to the highest levels at a concentration of 10 g/ml or more of IdeS. (C) Time to react after adding IdeS. The binding of GM1-IgG halved after around 10 minutes and was almost eliminated after one hour. (D).