Therapy of a murine sarcoma using syngeneic monoclonal antibody

Syngeneic monoclonal antibodies (MoAb) to Moloney sarcoma cells (MSC) were produced by fusion of spleen cells from MSC regressor mice to myeloma SP2/0. MoAb 244-19A, an immunoglobulin G2b, bound to MSC cells and did not bind to two other sarcomas (K-BALB and Ha2), a carcinoma (Line 1), a fibroblast (A31) or a fibroblast infected with C-type virus (A31-Moloney leukemia virus). In contrast, MoAb 271-1A bound to the MSC and Ha2 sarcoma and line 1 carcinoma as well as to the normal and infected fibroblast cultures. Antibodies were tested for therapeutic effect using three schedules of antibody injection. Injection i.p. of ascites fluid containing 244-19A MoAb given on Days-1, 0, and +1 relative to tumor cell injection increased life span significantly over that of control animals given injections (P3, immunoglobulin G, or MoAb 271-1A) and produced some seven of 19, one of five, and one of five long-term survivors in three separate experiments. Antibody given to animals with established tumors (4 days after implantation) also prolonged life span significantly and produced three of nine long-term survivors. Antibody given to animals with very large tumor burdens (10 days after implantation) did not prolong life span significantly. Optimal dose, schedule, and mechanism studies concerning this therapy are in progress.