Effective Adoptive Immunotherapy by T-LAK Cells Retargeted with Bacterial Superantigen-conjugated Antibody to MUC1 in Xenografted Severe Combined Immunodeficient Mice

Abstract

To reinforce cytotoxic activity and the targeting ability of lymphokineactivated killer cells with a T-cell phenotype (T-LAK) for adoptive immunotherapy against human bile duct carcinoma (BDC), staphylococcal enterotoxin A (SEA) was conjugated chemically with MUSE11 monoclonal antibody (MUSE11 mAb), directed to the MUC1 antigen, using N-succinimidyl 3-(2-pyridyldithio) propionate and 2-iminothiolane HCl. Both SEA-conjugated MUSE11 mAb (SEA-MUSE11) and the F(ab')₂ of MUSE11 mAb (SEA-F(ab')₂) showed significant enhancement of T-LAK cell tumor neutralization for MUC1 positive-target tumor cells, even with a concentration of 0.01 µg/ml at an E:T ratio of 5:1 in vitro. In this in vitro test, MUC1-positive BDC cells were observed to attach to surrounding T-LAK cells in the presence of SEA-MUSE11 or SEA-F(ab')₂. Remarkable tumor growth inhibition was observed in BDC-grafted severe combined immunodeficient mice to which 2 × 10⁷ T-LAK cells preincubated with 2 µg of SEA-MUSE11 or SEA-F(ab')₂, together with recombinant interleukin 2 (500 IU), were administered i.v. for 4 consecutive days, when tumor size was 5 mm in diameter. These results point to a promising adoptive immunotherapy for patients with BDC.