Complete response to donor lymphocyte infusion in multiple myeloma is associated with antibody responses to highly expressed antigens.

The ability of donor lymphocyte infusions (DLIs) to induce complete responses (CRs) in patients with relapsed myeloma after allogeneic bone marrow transplantation (BMT) provides clear evidence of an effective graft-versus-myeloma (GVM) response. To identify target antigens of the GVM response, we screened a myeloma cDNA expression library with post-DLI serum from 4 patients with myeloma who achieved CR after DLI and 1 patient who was in CR before DLI. We identified a panel of 13 gene products reactive with post-DLI serum but negative with pre-DLI and pre-BMT serum. Antibodies to these proteins were not detected in the sera of 10 patients who underwent allogeneic BMT without DLI and 5 patients with acute graft-versus-host disease (GVHD). Minimal reactivity with these proteins was detected in the sera of 20 healthy donors and 20 patients with chronic GVHD. In contrast, 5 of these proteins were recognized by more than 1 myeloma DLI responder. Testing of serial serum samples showed an association between antibody response and time of best response after DLI. The expression of these genes was evaluated in primary myeloma cells and in normal plasma cells. This study demonstrates that the GVM response is associated with antibody responses to highly expressed myeloma-associated antigens.