Narcolepsy with Cataplexy (N/C) is a common sleep disorder, but very little is understood about the underlyingmechanism that causes N/C and why symptoms are severe in some patients but not in others. N/C is causedby selective loss of the hypothalamic neurons that produce the orexin neuropeptides and is strongly associatedwith the Major Histocompatibility Complex (MHC) class II allele DQB1 *0602. We hypothesize that N/C iscaused by CD4+ or CD8+ T cells response directed against the hypothalamic neurons producing the orexinneuropeptides, and that a more aggressive immune response results in increased severity of N/C. Thishypothesis is supported by a number of publications suggesting a causal role of the cellular immune responsein N/C as well as our own preliminary data. Our long term goal is to understand the cause of N/C and thedeterminants of disease severity. In doing so, we will also devise a much needed blood test for the earlydiagnosis of NC and prediction of disease severity. Our objectives are to determine whether N/C patientsmount a cellular immune response to orexin peptides and whether this response is associated with moresevere symptoms. The rationale is that these proposed studies will enable us to develop a blood test for earlydiagnosis 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 peptidesusing three different assays: 1) Intracellular Cytokine Staining (ICS) assay 2) Luminex xMAP bead array on cellculture 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 adiagnostic 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 cellularmechanisms leading to N/C. The proposed research is significant because it will allow us to identify theimmunopathogenic mechanisms leading to N/C, develop a blood test for early diagnosis of N/C and predictdisease severity. The knowledge gained from these studies will also have far reaching implications inadvancing 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 theclinical management of Narcolepsy with Cataplexy patients; and provide a novel diagnostic test and targets fortherapeutic interventions. Thus; the proposed research is relevant to the part of NINDS' mission that pertainsto developing fundamental knowledge to alleviate the burdens of neurological diseases.
