Double Monoclonal Immunoassay for Quantifying Human Visinin-Like Protein-1 in CSF

To the Editor: Alzheimer disease (AD)1 is thought to account for up to 70% of all dementia cases and is estimated to be the third leading cause of death in the US (1). To date, clinical trials of potential drug therapies have had little success when cognitive defects are present before the start of the clinical trial. Tau protein, phosphorylated tau protein, and Aβ 42/Aβ40 amyloid peptide are implicated in the neuropathology of AD but could be altered by potential drug candidates. Thus, there is an expanding search for additional biomarkers to identify subjects at a high risk of developing symptomatic AD in the future. Visinin-like protein-1 (VILIP-1) in the cerebrospinal fluid (CSF) has shown promise to predict cognitive symptoms of AD years before they occur (2, 3). Our initial VILIP-1 assay used a murine monoclonal capture antibody and an affinity-purified rabbit (4), and then later an affinity-purified sheep antibody for detection (2, 3). Here, we describe a new 2–monoclonal antibody (mAb) VILIP-1 assay and evaluation of different recombinant forms of VILIP-1 as standards with the various assays. We also assessed antibody cross-reactivity to other neuronal calcium sensor proteins. mAbs 3A8.1 (IgG1k) and 2B9.3 (IgG2ak) were obtained from fusions 4399 …