Therapeutic effects of idiotype vaccination can be enhanced by the combination of granulocyte–macrophage colony-stimulating factor and interleukin 2 in a myeloma model.

Summary. Idiotype (Id) vaccination provides an interesting immunotherapeutic strategy against B-cell lymphomas. In multiple myeloma (MM), however, the therapeutic efficacy of Id vaccination has been disappointing. In an attempt to improve the antitumoral potential, we added granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin 2 (IL-2) to the protocol. Balb/c mice were inoculated i.p. (d 2) with different doses (1–5 × 10⁵ ) of HOPC myeloma cells secreting the Ig^HOPC Id protein. Two days later, animals were injected with 10 000 U GM-CSF i.p. for 6 d consecutively (d 0–5). On d 5 and 11, myeloma-specific immunoglobulin (Ig^HOPC ) was administered i.p. together with incomplete Freund adjuvans followed by IL-2 (2 × 10 000 U/d; i.p) for 10 d (d 5–14). In animals inoculated with 10⁵ myeloma cells, treatment with IL-2 given as a single agent prolonged the median survival time (MST, 67 d) when compared with the tumour control group (MST 48 d), whereas GM-CSF did not elicit any survival benefit (MST 49 d). Complete tumour rejection could be achieved in 27% (4/15) by the combination of Id vaccination and GM-CSF. Additional treatment with IL-2 further increased antimyeloma activity. In this case, 59% of the animals showed no signs of tumour recurrence. In mice with high tumour burden (5 × 10⁵ ), no treatment modality achieved long-term survivors. Both natural killer (NK) cells and CD8⁺ T cells may be involved in the antitumoural immune response. These data provide evidence for the combined use of GM-CSF and IL-2 to enhance the therapeutic effectiveness of clinical cancer vaccination protocols. [ABSTRACT FROM AUTHOR]