Contributions
Abstract: EP1506
Type: ePoster
Abstract Category: Pathology and pathogenesis of MS - 18 Neurobiology
Background: Multiple sclerosis (MS) involves immune cells including B and T cells but the actual targets of the immune response are still undefined. The ATP-sensitive inward rectifying potassium channel KIR4.1 expressed by glial cells is suspected as an autoantigen since high seric levels of IgG against its extracellular peptide sequence (e1) were reported in half of MS patients. Yet, high discrepancies in frequencies (0-28 %) exist among laboratories raising concerns about KIR4.1 as a valid marker and autoantigen candidate for MS. They may result from technical pitfalls or different protein conformations differentially recognised by the antibody.
Methods and results: Using ELISA with the synthetic e1 sequence as coating peptide, we obtained very high seric levels of anti-e1 IgG from e1-immunised mice with no signal from control mice. Concomitantly, we screened human sera for the presence of anti-e1 hIgG from 71 patients diagnosed for a Clinically Isolated Syndrome (CIS), 193 untreated MS patients and 130 Healthy Volonteers (HV). We found that 5.3 % of CIS/MS patients exhibit high levels of KIR4.1 antibodies (defined as high responders - HR - using a threshold of 2.5 SD above HV mean) vs. 0.7% in HVs (p< 0.02). Moreover, the anti-e1 mouse serum labeled scarce astroglial cells and slightly white matter glial fibers in the normal rodent and human brain, with increased labeling in MS brain. Specific immunolabeling using anti-e1 mouse serum or a HR serum was obtained on cultured human astrocytoma, particularly when glycosylation was inhibited in vitro. Western Blot of astrocytoma extracts showed that the anti-e1 serum recognised the unglycosylated form of KIR4.1 but not higher molecular weight forms. Immunisation with e1 peptide results in the late development of experimental autoimmune encephalomyelitis in 1/3 of the mice.
Conclusions: These data demonstrate in a subset of MS patients the presence of anti-Kir4.1 auto-antibodies directed against the unglycosylated protein, which is increased in MS lesions. The development of demyelinating neuroinflammation in e1-immunised mice supports KIR4.1 as an autoantigen. Our results favor the heterogeneity in the autoimmune aspect of the disease, in which subgroups with discrete IgG autoreactivites for CNS antigens may be further delineated in the MS spectrum.
Disclosure: Supported by Inserm and Association Antares.
DL received honoraria for lectures from Biogen, Novartis, Sanofi-Genzyme and Merck.
Vincent Van Pesch received travel grants from Biogen, Bayer Schering,Genzyme, Merck, Teva, Sanofi and Roche. His institution receives honoraria for consultancy and lectures from Biogen, Bayer Schering, Sanofi, Merck, Roche, Teva and Novartis Pharma, and research grants from NovartisPharma, Bayer Schering, Sanofi and Roche.
Other authors: no conflict of interest.
Abstract: EP1506
Type: ePoster
Abstract Category: Pathology and pathogenesis of MS - 18 Neurobiology
Background: Multiple sclerosis (MS) involves immune cells including B and T cells but the actual targets of the immune response are still undefined. The ATP-sensitive inward rectifying potassium channel KIR4.1 expressed by glial cells is suspected as an autoantigen since high seric levels of IgG against its extracellular peptide sequence (e1) were reported in half of MS patients. Yet, high discrepancies in frequencies (0-28 %) exist among laboratories raising concerns about KIR4.1 as a valid marker and autoantigen candidate for MS. They may result from technical pitfalls or different protein conformations differentially recognised by the antibody.
Methods and results: Using ELISA with the synthetic e1 sequence as coating peptide, we obtained very high seric levels of anti-e1 IgG from e1-immunised mice with no signal from control mice. Concomitantly, we screened human sera for the presence of anti-e1 hIgG from 71 patients diagnosed for a Clinically Isolated Syndrome (CIS), 193 untreated MS patients and 130 Healthy Volonteers (HV). We found that 5.3 % of CIS/MS patients exhibit high levels of KIR4.1 antibodies (defined as high responders - HR - using a threshold of 2.5 SD above HV mean) vs. 0.7% in HVs (p< 0.02). Moreover, the anti-e1 mouse serum labeled scarce astroglial cells and slightly white matter glial fibers in the normal rodent and human brain, with increased labeling in MS brain. Specific immunolabeling using anti-e1 mouse serum or a HR serum was obtained on cultured human astrocytoma, particularly when glycosylation was inhibited in vitro. Western Blot of astrocytoma extracts showed that the anti-e1 serum recognised the unglycosylated form of KIR4.1 but not higher molecular weight forms. Immunisation with e1 peptide results in the late development of experimental autoimmune encephalomyelitis in 1/3 of the mice.
Conclusions: These data demonstrate in a subset of MS patients the presence of anti-Kir4.1 auto-antibodies directed against the unglycosylated protein, which is increased in MS lesions. The development of demyelinating neuroinflammation in e1-immunised mice supports KIR4.1 as an autoantigen. Our results favor the heterogeneity in the autoimmune aspect of the disease, in which subgroups with discrete IgG autoreactivites for CNS antigens may be further delineated in the MS spectrum.
Disclosure: Supported by Inserm and Association Antares.
DL received honoraria for lectures from Biogen, Novartis, Sanofi-Genzyme and Merck.
Vincent Van Pesch received travel grants from Biogen, Bayer Schering,Genzyme, Merck, Teva, Sanofi and Roche. His institution receives honoraria for consultancy and lectures from Biogen, Bayer Schering, Sanofi, Merck, Roche, Teva and Novartis Pharma, and research grants from NovartisPharma, Bayer Schering, Sanofi and Roche.
Other authors: no conflict of interest.