PREPARATION OF CEA MONOCLONAL ANTIBODY-TRICHOSANTHIN CONJUGATE AND STUDY OFITS BIOLOGICAL ACTIVITY
Ge Hailiang Zhang Huizheng Zhou Guangyan Lu Deyuan Shanghai Second Medical University, Shanghai Institute of Immunology
Trichosanthin(TCS) was conjugated via a disulf ide bond with CEA MAb (B3IgG) which had been first crosslinked with N-succinimidyl-3 (2pyridyl)-dithiopropionate (SPDP)to form the immunotoxin(IT).B3IgG-TCS. On SDS-PAGE,neither free TCS nor B3IgG was dete ted to be present in the IT that had been purified through Sephadex G-150 gel filtration and Blue Sepharose-4B ion gradient exchange chromatography. The IT was verified to be well constructed (TCS/B3IgG mole ratio: 1-2/1).Our results showed that the B3IgG moiety of IT molecules retained the ability of specific binding to the CEA possitively or CEA expressed human colonic cacinoma cells (LoVo)as determined by indirect immunoflurescence technique and ELISA method.The IT showed selective killing activity to target cell lines (LoVo) in vitro. The concentration of fifty percent cytotoxicity(I. C.50)was about 10-9M for LoVo cells, thus the IT was approximately 150 times stronger than free TCS or 2000-times strongerthan the conjugate of TCS with normal mouse IgG (TCS-N-MIgG). Moreover, IT showed no enhanced killing capability for the CEA-negative carcinoma cells (HeLa) in control study.