Immunotherapeutic Targeting of Corticotropin-Releasing Hormone in Alzheimer's Disease

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Project Summary/Abstract Recent clinical reports indicate that chronic psychological stress may significantly increase the risk of developing Alzheimer’s Disease (AD). A major coordinator of the stress response is corticotropin-releasing hormone (CRH), a neuropeptide that is released in response to perception of stressful stimuli. CRH signaling has been shown to be able to induce increases in amyloid beta (Aβ) peptide levels and tau phosphorylation in mouse models of Aβ pathology. The largest effort towards targeting the CRH signaling pathway has focused on CRH receptor antagonists, Unfortunately, clinical trials implementing these CRH receptor antagonists have been unable to show clinical efficacy. Therefore, while dysregulation of CRH signaling is implicated in a plethora of highly prevalent stress related disorders in addition to AD, receptor- based interventions have not shown to be able to effectively target the pathway in humans. We propose the creation and testing of novel immunotherapeutic approaches to decrease CRH signaling in the brain. Aim 1: Develop anti-CRH immunotherapies and evaluate their ability to engage CRH and block engagement with its high affinity receptor the CRHR1. As our lab has shown that CRH has direct effects on Aβ production12 that are independent of its action on the CRHR1 receptor, we aim to target CRH directly by developing both active vaccines and monoclonal antibodies against CRH. Then evaluate several candidate Anti- CRH monoclonal antibodies and characterize their CRH-neutralizing properties in vitro. We will then take the most promising monoclonal antibodies and convert them to single chain variable fragment (scFv) DNA constructs that we can than transduce in the brains of mice using recombinant Adeno Associated Virus (rAAV). Specific Aim 2: Evaluate ability of immunotherapies to block acute CRH responses in vivo. I will test the ability of the anti-CRH vaccine, monoclonal antibody, and scFv to block acute stress-induced increases in corticosterone in mice following acute or subacute stress. This experiment will test whether these immunotherapies are able to neutralize CRH within the hypophyseal portal system, thereby blocking activation of the Hypothalamic-Pituitary-Axis. This will be followed by testing the ability of our immunotherapies to block acute stress-induced increases in Aβ peptide and tau phosphorylation, evaluating CRH neutralization more broadly throughout the mouse brain. Aim 3: Evaluate the efficacy of active and passive immunotherapeutic approaches in mouse models of Aβ and tau deposition. We intend to test the efficacy of an active vaccine, a monoclonal antibody, and one rAAV scFv construct as therapies in in vivo models relevant to AD. These studies will evaluate the ability of our immunotherapies to block stress-induced exacerbations of Aβ and tau pathologies in CRND8 APP overexpressing and rTg4510 mutant tau overexpressing mouse models.