Recognition and Degradation of Myelin Basic Protein Peptides by Serum Autoantibodies: Novel Biomarker for Multiple Sclerosis

Abstract

The pathologic role of autoantibodies in autoimmune disease is widely accepted. Recently, we reported that anti-myelin basic protein (MBP) serum Abs from multiple sclerosis (MS) patients exhibit proteolytic activity toward the autoantigen. The aim of this study is to determine MBP epitopes specific for the autoantibodies in MS and compare these data with those from other neuronal disorders (OND), leading to the generation of new diagnostic and prognostic criteria. We constructed a MBP-derived recombinant “epitope library” covering the entire molecule. We used ELISA and PAGE/surface-enhanced laser desorption/ionization mass spectroscopy assays to define the epitope binding/cleaving activities of autoantibodies isolated from the sera of 26 MS patients, 22 OND patients, and 11 healthy individuals. The levels of autoantibodies to MBP fragments 48–70 and 85–170 as well as to whole MBP and myelin oligodendrocyte glycoprotein molecules were significantly higher in the sera of MS patients than in those of healthy donors. In contrast, selective reactivity to the two MBP fragments 43–68 and 146–170 distinguished the OND and MS patients. Patients with MS (77% of progressive and 85% of relapsing-remitting) but only 9% of patients with OND and no healthy donors were positive for catalysis, showing pronounced epitope specificity to the encephalitogenic MBP peptide 81–103. This peptide retained its substrate properties when flanked with two fluorescent proteins, providing a novel fluorescent resonance energy transfer approach for MS studies. Thus, anti-MBP autoantibody-mediated, epitope-specific binding and cleavage may be regarded as a specific characteristic of MS compared with OND and healthy donors and may serve as an additional biomarker of disease progression.

High-Density Peptide Microarray Analysis of IgG Autoantibody Reactivities in Serum and Cerebrospinal Fluid of Multiple Sclerosis Patients

“…In their study, all three peptides showed significantly higher antibody levels in the PPMS/SPMS group compared with the healthy group. Moreover, we filtered "DTGILDSIG-RFFGGD" (MBP 168 -182) as frequently bound by sera of PPMS patients (supplemental File S6), which is also in accordance with the findings by Belogurov et al (46). The region MBP 257-276 forms a flexible loop at the protein surface (Fig.…”

“…Belogurov et al tested 12 peptides covering the MBP sequence (isoform 5) for serum IgG reactivities (46). Three of their peptides overlapped with the peptide MBP 257-276 ("PGFGYGGRASDYKSAHKGFK"), which was filtered as PPMS-specific in our CSF IgG data set (Table III).…”

The Pathogenesis of the Demyelinating Form of Guillain-Barre Syndrome (GBS): Proteo-peptidomic and Immunological Profiling of Physiological Fluids

“…Surface plasmon res- onance studies confirmed that the serum antibodies from the AIDP patients did not bind MBP. Similarly, we failed to detect any catalytic activity of the antibodies against MOG and MBP (data not shown), the latter of which was previously shown to be hydrolyzed by autoantibodies in MS (52,53).…”

“…Besides, antibodies to several proteins in the nodal area of the peripheral nerves -in particular, gliomedin, neurofascin, contactin (63,64), and moesin (65) -were found in the blood stream of some AIDP patients. We also tested blood samples against the CAM proteins whose fragments we observed.A slightly enhanced titer of autoantibodies was found only against NrCAM and the difference was not as evident as in other classic autoimmune diseases with their autoantigens (53,66). Thus, the degradation of the abovementioned proteins seems to have been associated with factors other than the autoreactive antibodies to those proteins.…”

Catalytic Antibodies in Norm and Systemic Lupus Erythematosus

“…In MS and SLE, anti-MBP abzymes with proteolytic activity can attack MBP of the myelin-proteolipid sheath of axons. The established MS drug Copaxone was shown to be a specific inhibitor of abzymes with MBP-hydrolyzing activity [128]. One cannot exclude that the same drugs can be used for the treatment of SLE and other autoimmune diseases, which characterized by high level of abzymes with nuclease and MBP-hydrolyzing activities.…”