Self-antigen tetramers discriminate between myelin autoantibodies to native or denatured protein

Abstract

The role of autoantibodies in the pathogenesis of multiple sclerosis (MS) and other demyelinating diseases is controversial, in part because widely used western blotting and ELISA methods either do not permit the detection of conformation-sensitive antibodies or do not distinguish them from conformation-independent antibodies. We developed a sensitive assay based on self-assembling radiolabeled tetramers that allows discrimination of antibodies against folded or denatured myelin oligodendrocyte glycoprotein (MOG) by selective unfolding of the antigen domain. The tetramer radioimmunoassay (RIA) was more sensitive for MOG autoantibody detection than other methodologies, including monomer-based RIA, ELISA or fluorescent-activated cell sorting (FACS). Autoantibodies from individuals with acute disseminated encephalomyelitis (ADEM) selectively bound the folded MOG tetramer, whereas sera from mice with experimental autoimmune encephalomyelitis induced with MOG peptide immunoprecipitated only the unfolded tetramer. MOG-specific autoantibodies were identified in a subset of ADEM but only rarely in adult-onset MS cases, indicating that MOG is a more prominent target antigen in ADEM than MS.The role of autoantibodies in the pathogenesis of human demyelinating diseases of the central nervous system (CNS) is an important, unresolved issue. In animal models, autoantibodies that recognize epitopes on the surface of myelin or myelin-producing oligodendrocytes can enhance demyelination 1,2 . A monoclonal antibody (8-18C5) against myelin oligodendrocyte glycoprotein (MOG) induces severe demyelination in mice and rats with mild experimental autoimmune encephalomyelitis (EAE) but does not induce disease in healthy animals because the antibody cannot gain access to the CNS parenchyma 1,2 . MOG is a minor component of myelin but is localized on the outer surface of the multilamellar myelin structure and is thus accessible to antibodies, whereas more abundant antigens such as myelin basic protein are inaccessible in intact myelin 1 . In the marmoset primate model of EAE, immunization with MOG induces a chronic demyelinating disease with pathological features reminiscent of MS (ref. 3). In mouse models, however, severe demyelination is observed in the absence of antibodies and B cells 4 , indicating that autoantibodies are not required for demyelination in all species.These elegant studies in animal models have shown the demyelinating potential of autoantibodies to myelin surface proteins, but their role in the pathogenesis of human inflammatory demyelinating diseases such as MS and acute disseminated encephalomyelitis (ADEM) is far less certain. MOG has been extensively studied as a potential target antigen for autoantibodies in MS (refs. 5-8) Unlike MS, ADEM typically has a rapidly progressive clinical presentation that includes encephalopathy 11 . The disease course is usually self limiting, although in a minority of cases relapses may occur. The pathogenic relationship between MS and ADEM is unclear, and it remains to be d...

Antigen microarrays identify unique serum autoantibody signatures in clinical and pathologic subtypes of multiple sclerosis

“…In the CSF, antigen microarrays in MS have detected antibodies to lipid (6) and ␣B-crystallin (23) and of note, the ␣B-crystallin reactive antibodies were of low affinity, detectable at 1:20 dilution (23). High-affinity autoreactive antibodies in the serum have not been consistently found in MS (24)(25)(26)(27)(28). We found that unique autoantibody signatures characterize RRMS, SPMS and PPMS based on reactivity to CNS antigens and HSP.…”

Chapter 4 B Cells and Autoantibodies in the Pathogenesis of Multiple Sclerosis and Related Inflammatory Demyelinating Diseases

“…Increased frequencies of antibodies to MOG have been reported in the serum and CSF of MS patients relative to controls (Kennel De March et al, 2003), but other studies have found similar levels of anti-MOG in MS and other neurological diseases or controls (Brokstad et al, 1994;Lampasona et al, 2004;Mantegazza et al, 2004;Markovic et al, 2003;O'Connor et al, 2007;Reindl et al, 1999). Although detectable in some cases, the reported frequency of anti-MOG in serum and CSF from MS patients varies considerably between studies.…”

“…New methods have therefore been developed that enable specific detection of antibodies to properly folded and glycosylated MOG protein. The first method involves labeling of MOG transfectants with serum or CSF antibodies Lalive et al, 2006;O'Connor et al, 2007;Zhou et al, 2006), but the frequency of anti-MOG in MS still varies considerably between these studies, suggesting heterogeneity in the studied patient populations. The second method is a sensitive radioimmunoassay with a tetrameric version of folded and glycosylated MOG protein.…”

Acute disseminated encephalomyelitis: where does it start and where does it stop?

“…2 Also the recognition of specific and sensitive immune abnormalities in clearly defined clinical phenotypes (such as anti-Aquaporin-4 antibodies in neuromyelitis optica 3 ) suggests that discrete clinical and immunological diseases may exist within the spectrum of CNS inflammatory demyelination. Further examples of specific immune markers in discrete ADEM variants include the presence of antimyelin oligodendrocyte antibodies in a subgroup of ADEM, 4 and antibodies against basal ganglia components in post-streptococcal ADEM with dominant basal ganglia MRI lesions. 5 Further examination for these and other immune parameters may help 'split' the various ADEM variants, rather than 'lump' them all together, as occurs now.…”

“…directed against cytokines, B-cells, T-cells, etc.). 3,4 Over the past decade, it has become increasingly clear that patients with multiple sclerosis have a spectrum of immune perturbations. It is likely that future therapies will become tailored and individualized according to the dominant pathogenic immune mechanism in each patient.…”