Development of Two Multiplexed Immunoassays for Study of Blood-Based Biomarkers of Alzheimer's Disease (P04.224)

OBJECTIVE: To develop multiplexed immunoassays that measure candidate biomarkers for Alzheimer9s disease (AD) in blood. BACKGROUND: Blood-based biomarkers provide a cost-effective means to screen for AD at the population level. Circulating alpha-2-macroglobulin (A2M), beta-2-microglobulin (B2M), factor VII (FVII), tenascin C (TNC), pancreatic polypeptide Y (PPY), interleukin-18 (IL-18), fatty acid binding protein 3 (FABP3), thrombopoietin (TPO), and I-309 are candidate blood-based AD biomarkers. We describe two multiplexed immunoassays that measure these proteins in human plasma and serum. DESIGN/METHODS: MSD® developed two multiplexed panels according to fit-for-purpose assay development and validation principles. The panels were tested for precision, sensitivity, specificity, and matrix tolerance. To evaluate matrix compatibility, protein levels were measured in ten matched sets of EDTA and heparinized plasma and serum. Protein levels were also measured in samples from patients with and without AD. RESULTS: The panels were assembled based on biomarker abundance in human plasma and serum. The high abundance panel (4,000-fold dilution) included A2M, B2M, FVII, and TNC. The low abundance panel (2-fold dilution) included PPY, IL-18, FABP3, TPO, and I-309. Calibrator signal variability was less than 30% over a multi-day, multi-lot precision study. All biomarkers were detectable in plasma and serum at their respective dilutions with minimal levels of non-specific binding. Concentrations were quantified similarly across EDTA plasma, heparinized plasma, and serum for all analytes. For both panels, dilutional linearity and spike and recovery were within 80-120% of the expected values with the exception of PPY. Differences in analyte levels between AD cases and controls were protein-dependent. CONCLUSIONS: The two multiplex panels developed by MSD provide reproducible results and are compatible across multiple matrices. These panels support efforts to study blood-based biomarkers of AD and may accommodate inclusion of additional novel AD biomarkers. Disclosure: Dr. Oberoi has received personal compensation for activities with Meso Scale Discovery as an employee. Dr. Ellington has received personal compensation for activities with Meso Scale Discovery. Dr. Liu has received personal compensation for activities with Meso Scale Discovery. Dr. Roy has received personal compensation for activities with Meso Scale Discovery. Dr. Umek has received personal compensation for activities with Meso Scale Discovery as an employee. Dr. Barber has nothing to disclose. Dr. O9Bryant has nothing to disclose. Dr. Wohlstadter has received personal compensation for activities with Meso Scale Discovery as an employee. Dr. Wohlstadter holds stock and/or stock options in Meso Scale Discovery.