Targeted Mass Spectrometric Immunoassay for Detection of Cystatin C Isoforms in Cerebrospinal Fluid

Abstract

Targeted cerebrospinal fluid (CSF) Mass Spectrometric Immunoassay for cystatin C was developed and applied to a small number of CSF and serum samples obtained from healthy and individuals diagnosed with multiple sclerosis. Cystatin C and its variants were retrieved from the CSF samples via affinity micro columns derivatized with cystatin C antibodies, and were eluted onto MALDI mass spectrometer targets. The resulting mass spectra revealed various levels of cystatin C isoforms in the samples. Truncated Cystatin C isoforms missing 3, 4, 7, 8, 9, 10, 11, 14, 15, and 17 N-terminal amino acid residues were detected. Correlation in the level of truncation between the matched CSF and serum samples was also observed. The mass spectrometric immunoassay provided rapid, high-throughput assessment of cystatin C and its isoforms present in biological fluids.