In Situ Recovery of hCTLA4Ig Using a Modified Flask in Transgenic Rice Suspension Cell Cultures

초록

Transgenic rice, Oryza sativa L., cells were cultured to produce human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig), a fusion protein used for the treatment of rheumatoid arthritis. This plant cell culture system with the signal peptide for the secretion of target protein into extracellular medium and the inducible RAmy3D promoter was used for the production of the recombinant therapeutic protein in order to overcome the constraint of low production level1). However, the RAmy3D promoter system has a drawback in decreasing cell viability because the promoter is induced only by sugar starvation. The cell death stimulated the release of protease, which degraded target protein2). In order to solve this instability problems of the product after the secretion, in situ product recovery was performed by using a modified flask3). The modified flask was specially designed with glass filter to make medium exchange easy and successful. The medium exchange provided an improved culture condition for the cells because proteases could be removed from the culture environment by dilution with new medium after exchange. Contrary to the expectation, it was found that the production level of hCTLA4Ig was not increased despite of the increase of fresh and dry cell weight. These results show that in situ product recovery using a modified flask could not enhance the production of hCTLA4Ig in transgenic rice cell culture system.