Adsorptive Loss of Recombinant Proteins in Transgenic Rice Cell Suspension Cultures

초록

Two possibilities have been known for the loss of recombinant proteins in plant cell cultures; one is proteolysis and the other is a non-reactive process such as protein adsorption. In this experiment, the adsorptive loss of hCTLA4Ig in transgenic rice cell suspension cultures was investigated with glass flasks, plastic flasks, and stainless steel vessels. The rapid decrease of hCTLA4Ig concentrations, not dependent on pH, was observed when hCTLA4Ig was added externally into the medium. Within 1 hr, over 90% of hCTLA4Ig was lost from the media. However, protein degradation by protease was not observed in the fresh medium and in sterilized conditioned medium. More than 90% of initial hCTLA4Ig in glass flasks was lost from sterile AA medium within 1 hr. The hCTLA4Ig was confirmed to be adsorbed on the glass surface. The adsorption level of hCTLA4Ig was the lowest in plastic flasks and the highest in glass flasks. The use of plastic flask retarded the adsorptive loss of hCTLA4Ig at the early stage of production. In addition, the production of hCTLA4Ig was increased in flasks coated with bovine serum albumin. However, the spike test of purified hCTLA4Ig at a concentration of 100 mg/L was performed and it was found that the total amount of adsorbed protein was less than 5% of spiked protein. In conclusion, protein adsorption clearly reduces the protein yield in the medium.