Narcolepsy with Cataplexy (N/C) is a common sleep disorder, but very little is understood about the underlying mechanism that causes N/C and why symptoms are severe in some patients but not in others. N/C is caused by selective loss of the hypothalamic neurons that produce the orexin neuropeptides and is strongly associated with the Major Histocompatibility Complex (MHC) class II allele DQB1 *0602. We hypothesize that N/C is caused by CD4+ or CD8+ T cells response directed against the hypothalamic neurons producing the orexin neuropeptides, and that a more aggressive immune response results in increased severity of N/C. This hypothesis is supported by a number of publications suggesting a causal role of the cellular immune response in N/C as well as our own preliminary data. Our long term goal is to understand the cause of N/C and the determinants of disease severity. In doing so, we will also devise a much needed blood test for the early diagnosis of NC and prediction of disease severity. Our objectives are to determine whether N/C patients mount a cellular immune response to orexin peptides and whether this response is associated with more severe symptoms. The rationale is that these proposed studies will enable us to develop a blood test for early diagnosis of N/C and predictor of disease severity. To test these hypotheses, we will pursue the following set of Specific Aims:
Aim 1) Correlate disease severity with the cellular immune response to orexin neuropeptides in DQB1 *0602+ Narcolepsy with Cataplexy patients. We will measure narcolepsy symptoms severity using well- validated scales and correlate symptom severity with the reactivity of CD4+ or CD8+ T cells to orexin peptides using three different assays: 1) Intracellular Cytokine Staining (ICS) assay 2) Luminex xMAP bead array on cell culture supernatant and 3) RT-qPCR for cytokine mRNA on cellular RNA .
Aim 2) Identify immunodominant orexin epitopes recognized by CD4+ or CD8+ T cells in DQB1 *0602+ Narcolepsy with Cataplexy patients. We will map orexin epitopes in N/C patients using ICS and devise a diagnostic blood test and predictor of disease severity for N/C. The approach is innovative, because it departs significantly from the status quo by focusing on the cellular mechanisms leading to N/C. The proposed research is significant because it will allow us to identify the immunopathogenic mechanisms leading to N/C, develop a blood test for early diagnosis of N/C and predict disease severity. The knowledge gained from these studies will also have far reaching implications in advancing the fields of Sleep Disorders and Neuro-Immunology.
The proposed research is relevant to public health because it will have an important positive impact on the clinical management of Narcolepsy with Cataplexy patients, and provide a novel diagnostic test and targets for therapeutic interventions. Thus, the proposed research is relevant to the part of NINDS' mission that pertains to developing fundamental knowledge to alleviate the burdens of neurological diseases.
