Biochemical assay for AD7C-NTP in urine as an Alzheimer's disease marker.

A reliable and specific immunoassay has been developed to detect and measure AD7C-NTP, a biochemical marker for Alzheimer's disease, in urine. The urine samples are first processed by centrifugation and ultrafiltration to fractionate and concentrate AD7C-NTP. The urinaryAD7C-NTP has the same molecular weight asAD7C-NTP in brain and cerebrospinal fluid by size exclusion chromatography. It has also retained the binding properties to the monoclonal and polyclonal antibodies developed against recombinantly produced AD7C-NTP. This assay is an enzyme linked sandwich immunoassay (ELSIA) using 96 well microtiter plates. The plate surface is coated with a monoclonal antibody (N314) which has a high affinity and specificity for AD7C-NTP, capturing it effectively from the samples. The detection was achieved using a polyclonal antibody (ADRI). The utility of the assay has been demonstrated using urine specimens from Alzheimer's disease (AD) patients and non-Alzheimer's controls. UrinaryAD7C-NTP in the AD group (2.5 ng/mL, n=66) was significantly higher than the non-AD group (0.8 ng/mL, n=134). Using 1.5 ng/mL as cut off, in this patient population, specificity and sensitivity of urinary AD7C-NTP were comparable to CSFAD7C-NTP.