Antitumor effects of antibody-diphtheria toxin conjugates. II. Immunotherapy with conjugates directed against tumor antigens induced by simian virus 40

Abstract

Hamster and rabbit antibodies against antigens on the surface of simian virus 40 (SV40)-transformed hamster sarcoma or lymphoma cells were purified by immunoadsorption on SV40-transformed cells and conjugated to diphtheria toxin with glutaraldehyde. Treatment with a single dose of antibody-toxin conjugate partially protected hamsters concurrently challenged with 10(3) SV40-transformed sarcoma cells, as evidenced by a reduction in tumor incidence, an increase in tumor latency, and a prolongation of the life-spans of hamsters that developed tumors. Treatment of established sarcomas was ineffective, but repeated treatment with the conjugates induced complete regressions in 20-56% of hamsters bearing established transplants in the SV40-induced lymphoma.