Specificity and Potential Pathogenicity of Antibodies to a Central Nervous System (CNS) Autoantigen in Multiple Sclerosis Patients (P07.087)

Abstract

Objective: To test whether antibodies to heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) in multiple sclerosis (MS) patients might contribute to alterations in neuronal function using in vitro and in vivo models of pathogenesis. Background MS patients develop antibodies to hnRNP A1, an mRNA binding protein critical to neuronal survival (J Neuroimmunol 235, 2011). Antibodies were specific for 9M99, its nuclear translocation sequence and caused neurodegeneration. hnRNP A1 has been shown to contribute to the pathogenesis of demyelination through molecular control of myelin associated glycoprotein (PNAS 107, 2010). We tested hnRNP A1 antibody specificity for the CNS and its contribution to changes in neuronal function. Design/Methods: Western blots of human tissues and hnRNP A1 fragments were probed for immunoreactivity with MS and control IgG. Multiple mouse monoclonal antibodies (mMabs) were tested for cross-reactivity with the hnRNP A1 epitope recognized by MS IgG. mMabs that cross-reacted with the hnRNP A1 epitope were added to SKNSH neurons and tested for cytotoxicity, apoptosis and cell viability. mMabs were labeled with near-infrared fluorophores, infused into SJL mice and localized with an 9In Vivo Imaging System (IVIS). Results: In contrast to systemic organs and control IgG, MS IgG immunoreacted with human brain, neurons and neuronal cell lines. mMabs were found to cross-react with the same epitope recognized by MS IgG. In contrast to control IgG, mMabs (that recognized the MS hnRNP A1 epitope) caused apoptosis and loss of cellular viability. There was no effect on cytotoxicity. Antibodies co-localized with endosomes within neurons, indicative of their endocytosis. mMabs specific for the MS IgG hnRNP A1 epitope localized exclusively to mouse brain and spinal cord by IVIS, suggesting the immune reaction is specific for the CNS. Control IgG showed no such localization. Conclusions: Antibodies to the hnRNP A1 epitope recognized by MS patients are specific for the CNS and pathogenic to neurons. Supported by: Office of Research and Development, Medical Research Service, Department of Veterans Affairs and University of Tennessee Health Science Center Multiple Sclerosis Research Fund. Disclosure: Dr. Levin has received personal compensation for activities with Serono, TEVA, Biogen-Idec, and Gerson Lehman Group. Dr. Lee has nothing to disclose. Dr. Gardner has nothing to disclose. Dr. Shin has nothing to disclose. Dr. Groover has nothing to disclose. Dr. Douglas has nothing to disclose. Dr. Raine has nothing to disclose.