An animal model for evaluation of antigen-specific dialyzable leukocyte extracts therapy of osteosarcoma

The effects of human osteosarcoma (OS)-specific dialyzable leukocyte extracts (DLE) in hamsters bearing human OS were investigated. The DLE used in this investigation was prepared from rabbits immunized with human osteosarcoma-associated antigens (DLE-OSAA). Tuberculin (DLE-PPD) and control DLE were prepared from rabbits injected with tuberculin or 0.85% NaCl (DLE-NaCl). DLE was administered subcutaneously into inbred hamsters (each injection contained DLE derived from 10(7) rabbit leukocytes). Four groups of animals were studied: group 1, amputation alone; group 2, amputation plus DLE-OSAA; group 3, amputation plus DLE-PPD; group 4, amputation plus DLE-NaCl. Of the DLE-OSAA-treated animals (group 2), 60% were still alive at 300 days postamputation; whereas in animals in groups 1, 3, and 4, all died within 90 days postamputation. In separate experiments, we found that 100% of the animals in groups 1, 3, and 4 developed pulmonary metastases within 30-60 days postamputation, whereas only 20% of the animals in group 2 developed metastases at the same time; indeed 40% of the DLE-OSAA-treated animals were free of metastases in 240-300 days postamputation. Both the leukocyte adherence inhibition assay (LAI) and lymphocyte DNA synthesis assay (LDS) were used to monitor the transfer of antigen-specific cell-mediated immunity in each group of tumor-bearing hamsters. All surviving hamsters in group 2 had high LAI and LDS activity. Our results suggest that DLE-OSAA is effective in preventing pulmonary metastases and death of OS-bearing hamsters (after amputation) as compared with amputation alone, amputation plus DLE-NaCl, and amputation plus DLE-PPD, and that its effect is via an antigen-specific mechanism.