Identification and assembly of V genes as idiotype-specific DNA fusion vaccines in multiple myeloma.

Tumor-specific markers are important in identifying and tracking malignant cells. In this regard, functionally rearranged immunoglobulin variable (V) region genes in B-cell tumors fulfill and extend these criteria. V genes provide signature motifs in tumor cells and can delineate critical features of the clonal history of the cell of origin. They also define a tumor-specific antigen, which can be targeted for immunotherapy. Our focus has been on using novel DNA fusion vaccines to induce antitumor immunity. Here, we describe in detail the methods for identifying tumor-derived V genes at the nucleotide level in the malignant plasma cells of multiple myeloma. We further present the methodology for assembly of tumor V genes as single-chain variable region fragments (scFv), fused in frame with an immunopotentiating nontoxic bacterial sequence, Fragment C (FrC) of tetanus toxin. These scFv.FrC DNA vaccines provide protection in myeloma models and are currently in clinical trials. The vaccines are patient specific and can be rapidly assembled for clinical use.