Pulmonary metastases neutralization and tumor rejection by in vivo administration of beta glucan and bispecific antibody.

Bispecific antibody (BsAb) with specificity for tumor cell surface antigen and the CD3 molecule on T cells can redirect activated T cells to lyse tumor cells. Since the ex vivo expansion and activation of T cells is impractical and ineffective for treating established tumors, we tested whether the immune stimulant beta glucan could in situ-activate T cells, which could secondarily be retargeted with BsAbs to lyse tumor cells. To test for tumor neutralization, C3H/HeN mice were injected i.v. with Cl-62 melanoma cells and immediately treated with i.p. beta glucan and/or anti-CD3 (500A2) x anti-p97 (96.5) F(ab')2 BsAb i.v. Pulmonary metastases were counted 14 days later. To test for tumor rejection and survival in a solid tumor model, mice were injected s.c. and i.p. with Cl-62 cells and 7 days later administered beta glucan i.p. and/or F(ab')2 BsAb i.v. In the neutralization model, there was a significant reduction in the number of metastases in the beta glucan + BsAb group, as compared with controls, and with beta glucan alone. In the established tumor model, beta glucan + BsAb reduced the incidence of s.c. tumors as compared with control, with BsAb alone and with beta glucan alone. It also prolonged survival of tumor-bearing mice compared with control, BsAb alone and beta glucan alone. We conclude that T cells can be activated in vivo by beta glucan and retargeted with F(ab')2 BsAb.