Development of a novel therapy for Lipo-oligosaccharide-induced experimental neuritis: use of peptide glycomimics

Guillain-Barre syndrome (GBS) is an immune-mediated disorder of the peripheral nervous system, and is the most frequent cause of acute flaccid paralysis in humans occurring with an annual incidence of 1–2 cases/100 000 (Hughes and Rees 1997). It is classified as an acute inflammatory demyelinating polyneuropathy with a variant form designated as acute motor axonal neuropathy (Hughes and Cornblath 2005). Anti-ganglioside antibodies have frequently been proposed as contributors to GBS pathogenesis (Kaida et al. 2009; Ariga and Yu 2005). Gangliosides are abundantly expressed in human nerves (Yu et al. 2004) and generally believed to have important roles as mediators of cell adhesion and modulators of signal transduction (Regina Todeschini and Hakomori 2008). Recently, molecular mimicry between microbial lipo-oligosaccharide (LOS) antigens and endogenous ganglioside GM1 has been proposed as an etiological mechanism for GBS because of the findings that the autoantibodies for GM1 [Galβ1-3GalNAcβ1-4(Neu-Acα2–3)Galβ1–4Glcβ1-1′Cer] can often be elicited by preceding infections by Campylobacter jejuni (Aspinall et al. 1992, 1994; Yuki et al. 1993). In addition to GM1-like LOS (LOSGM1), antibodies to GD1a, GT1a, and GD1c are also elicited by LOS antigens of C. jejuni neuritis-causing strains (Aspinall et al. 1994; Goodyear et al. 1999; Koga et al. 2005). Salloway et al. (1996) reported GD3-like LOS (LOSGD3) in a C. jejuni strain from a patient with Miller Fisher syndrome. In our previous study, we demonstrated that elevated titers of circulating antibodies to GD3 ganglioside [NeuAcα2-8NeuAcα2-3Galβ1-4Glcβ1-1′Cer] occurred in some patients with inflammatory demyelinating polyneuropathies. We have identified in strain HS19 of C. jejuni the presence of an LOSGD3 with a tetrasaccharide epitope [NeuAc-NeuAc-Gal-Hep] (Usuki et al. 2006) that has a terminal trisaccharide structure identical to GD3. This carbohydrate antigen causes LOSGD3-initiated nerve dysfunction in Lewis rats including interfering with ion channels essential for nerve conduction, and this is associated with increased anti-GD3 antibody (Usuki et al. 2006). Recently, we have initiated development of gangliosidemimic therapy targeting specific pathogenic antibodies with the goal of ameliorating the disease. This approach could prove superior to current GBS treatments, such as plasma-pheresis, intravenous administration of Ig, and immunosuppressive chemotherapy; all of which target both pathogenic and non-pathogenic antibodies. In our first experiment, the efficacy of neutralizing anti-GD3 antibody by intraperitoneal administration of anti-idiotype monoclonal antibody BEC2 specifically directed to the anti-GD3 antibody (Usuki et al. 2010) was examined. Our successful use of BEC2 to inhibit and neutralize circulating anti-GD3 and anti-LOSGD3 antibodies in the treated animals prompted us to seek additional and simpler epitope-neutralization therapies. Designing a 3D conformational epitope structural mimic common to these carbohydrates and peptides, we decided to test using peptide mimics that can be synthesized easily for eventual clinical application. GD3-like peptides were selected by panning of a phage peptide library using an anti-GD3 monoclonal antibody (mAb) (Willers et al. 1999; Popa et al. 2006). In this study, we tested several phage-displayed GD3-like peptides for treatment of our established rat model of LOSGD3-induced neuropathy. The peptide treatment thus designed improved peripheral nerve function, and in this model was most likely a consequence of neutralizing and blocking the pathogenic activity of the elevated anti-LOSGD3/anti-GD3 antibodies.