Using Top-Down Mass Spectrometry to Detect, Quantify and Isotype Monoclonal Immunoglobulins in Serum

The Mayo Clinic team of Barnidge, Murray and Dasari has focused on using mass spectrometry to monitor residual disease in multiple myeloma through the detection of antibody light chains in serum. The isotype of the light chain is determined by the identification of isotype-specific fragment ions generated by top-down MS. However, in order to translate the technology into their clinic, the method must be able to automatically detect, quantify and isotype both the light and heavy chain portions of an “M-protein” antibody. A more sensitive and specific marker of a monoclonal immunoglobulin based on molecular mass has the potential to reduce the number of bone marrow biopsies, which will translate into lower healthcare costs and a reduction of the number of invasive procedures for the patient.

While our collaborators have made progress using intact mass MS [19] to isotype light chains, they do not utilize tandem MS to characterize the heavy and light chains isolated from multiple myeloma patients. Here, expertise in the NRTDP will generate and interpret expected and unexpected fragment ions from the constant region, with extensive sequence coverage afforded by UVPD and ETD in targeted top-down modes described in TR&D 2. In later years, we envisage being able to gain extensive amino acid sequence information to be compared with a patient’s genome/exome. Without this collaboration, these investigators would only slowly adopt top-down MS/MS into their clinical labs. This is where alignment with the national resource on this translational project achieves synergy; notably, the Mayo Clinic is widely known for disseminating high value, validated clinical testing to its patients. The success of this DBP will be fueled by the multiple innovations proposed in TR&D 2 and TR&D 3. Full characterization of immunoglobulin heavy chains will be performed using the complete characterization instrument described within TR&D 2. However, since this assay is being developed for the Mayo Clinic’s clinical proteomics lab, we will also validate new methods on commercially available instruments to increase its ability to be adopted widely. Data will be collected and analyzed using the AUTOPILOT software described in TR&D 3, with AUTOPILOT ANALYZE generating custom reports programmed to best integrate with the Mayo Clinic’s existing workflows.

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