Seronegative Autoimmune Encephalopathies: Biomarker Discovery, Validation & Deep Phenotyping

PROJECT SUMMARY Incidence of autoimmune encephalitis exceeds that of infectious cause, but 50% percent (half of approximate 4000/year in the US) are IgG biomarker negative. Seronegativity hinders diagnosis and pathophysiologic understanding in autoimmune encephalopathies (encephalitis, cerebellar ataxias and other movement disorders). Novel IgG characterization, which attempts to address this gap, is linear and slow occurring at a rate of 1-2 year (using standard tissue-based immunofluorescence assay [IFA] followed by western blots, immunoprecipitation, and mass spectrometry). The long-term goal is to molecularly, clinically and mechanistically characterize autoimmune encephalopathies, and develop targeted autoimmune therapies. The overall objectives in this application, are to: 1) identify disease-specific biomarkers for seronegative autoimmune encephalopathies; 2) molecularly validate novel biomarkers, and 3) clinically, radiologically and immunologically deep-phenotype autoimmune encephalopathies. The central hypothesis is that seronegative autoimmune encephalopathies are characterizable though biomarker discovery. The rationale for this project is that biomarker discovery and translation could occur expeditiously, by leveraging complementary techniques in parallel, that novel biomarkers could be molecularly validated, and that disorders associated with new biomarkers could be neurologically and immunologically deep-phenotyped. To test the central hypothesis the following three specific aims will be pursued: 1) Identify novel biomarkers, initially in 3 partly characterized seronegative autoimmune encephalopathies; 2) determine validity of novel biomarkers; and 3) assess for differentiated clinical phenotypes, and cytokine profile accompaniments. Under the first aim, serum and CSF from seronegative autoimmune encephalopathy patients will be interrogated for neural antibodies using native full-length protein microarrays, as principle technique, complemented by tissue and cell-based IFA for initial IgG screening, and, as needed, phage immunoprecipitation sequencing, and mass spectrometry techniques for verification. For the second aim, newly characterized IgGs will be validated in autoimmune encephalopathy patients and controls by multiple antigen-specific methods (confocal indirect immunofluorescence, and recombinant protein assays [western blot, cDNA-transfected cell-based]). For the third aim, patients with autoimmune encephalopathies with characterized and validated neural IgGs will be deep-phenotyped clinically, radiologically and immunologically, by evaluating for IgG effects in live neuron assays, and cytokine-chemokine profiles. Remaining seronegative cohorts will be immunologically profiled by cytokine-chemokine assays. The research proposed is innovative in the applicant’s opinion, as it focuses on multiplexed biomarker identification, validation, and deep phenotyping. The proposed research is significant because disease-specific biomarkers, with in-depth characterization, allow earlier diagnosis and treatment, and support disease mechanism studies.