A novel ELISA for the measurement of cerebrospinal fluid SNAP-25 in patients with Alzheimer's disease.

Synaptic degeneration is central in Alzheimer's disease (AD) pathogenesis and biomarkers to monitor this pathophysiology in living patients are warranted. We developed a novel sandwich enzyme-linked immunosorbent assay (ELISA) for the measurement of the pre-synaptic protein SNAP-25 in cerebrospinal fluid (CSF) and evaluated it as a biomarker for AD. CSF samples included a pilot study consisting of AD (N=26) and controls (N=26), and two independent clinical cohorts of AD patients and controls. Cohort I included CSF samples from patients with dementia due to AD (N=17), patients with mild cognitive impairment (MCI) due to AD (N=5) and controls (N=17), and cohort II CSF samples from patients with dementia due to AD (N=24), patients with MCI due to AD (N=18) and controls (N=36). CSF levels of SNAP-25 were significantly increased in patients with AD compared with controls (P≤0.00001). In both clinical cohorts, CSF levels of SNAP-25 were significantly increased in patients with MCI due to AD (P<0.0001). SNAP-25 could differentiate dementia due to AD (N=41) from controls (N=52) and MCI due to AD (N=23) from controls (N=52) with areas under the curve of 0.967 (P<0.0001) and 0.948 (P<0.0001), respectively. CSF SNAP-25 is a promising AD biomarker that differentiates AD patients in different clinical stages of the disease from controls with excellent diagnostic accuracy. Future studies should address the specificity of the CSF SNAP-25 against common differential diagnoses to AD, as well as how the biomarker changes in response to treatment with disease-modifying drug candidates.