What should be focused in the study of cell culture technology for production of bioactive proteins

Effects of polyamines on proliferation and IgM productivity of human-human hybridoma, HB4C5 cells

Immunoglobulin production stimulating activity of polyamines was investigated. Spermidine, thermine and triethylenetetraamine (TETA) stimulated IgM production of human-human hybridoma, HB4C5 cells under serum-free condition. IgM production of HB4C5 cells was accelerated 5.9-, 5.3-, and 3.7-fold by spermidine at 4.5 mM, thermine at 2 mM and TETA at 2.5 mM, respectively. However, putrescine did not enhance IgM production. Spermidine enhanced IgM productivity of the hybridoma cells in spite of its growth suppression activity. TETA also inhibited cell proliferation and the effect on the acceleration of IgM productivity disappeared during 5 days because of its cytotoxicity. On the other hand, thermine facilitated IgM productivity of the hybridoma cells without growth suppression. The laser confocal microscopic analysis revealed that IgM content inside HB4C5 cells was increased by thermine. This result suggests that thermine facilitates IgM synthesis in hybridoma cells.

Production of monoclonal antibodies against human chorionic gonadotropin by hybridoma cultures in calcium alginate capsules

A new method of making microcapsules with calcium alginate gel was developed and the cultivation of the encapsulated hybridoma cells producing monoclonal antibodies against human chorionic gonadotropin was investigated. A high cell density of 2.0 x 10(8) cells/cm3 in the capsules led to a high dilution rate of 0.67 per hour and resulted in the high volumetric monoclonal antibody productivity of 652.8 mg/l/day, which was 20-30 times higher than those of traditional continuous suspension cultures. However, long-term continuous culture was not achieved with this capsule system probably because of the limitation in nutrient supply and the accumulation of waste products. Also the analysis of oxygen transfer in this system showed that oxygen supply was not enough to support such a high cell density.

Factors influencing expression and post-translational modification of recombinant protein C

Factors affecting the production of recombinant human protein C were investigated. When recombinant cells producing human protein C were cultured with microcarrier in two different scales, we found that (1) as cells grew to confluence, specific productivity of the protein was decreased and that (2) the efficiency of gamma-carboxylation of the generated protein C was lower in a larger culture than in a smaller culture. Higher cell density was shown to influence the specific productivity unfavorably. On the other hand, the amount of oxygen supply as demonstrated by oxygen consumption rate in the Opticell culture system correlated well with the efficiency of gamma-carboxylation, suggesting that oxygen metabolism is somehow implicated in the post-translational modification of recombinant protein C.

Purification of immunoglobulin production stimulation factor II alpha derived from Namalwa cells

An immunoglobulin production stimulating factor (IPSF) in human lymphoblastoid Namalwa cells was purified by the serial use of ammonium sulfate fractionation, hydrophobic interaction chromatography and gel filtration, and named IPSF-II alpha. IPSF-II alpha was estimated as a 112 KD protein composed of a 40 KD polypeptide and two 36 KD polypeptides. The 36 KD protein extracted from SDS-polyacrylamide gel showed IPSF activity, but not the 40 KD protein. The IPSF activity was reasonably stable in alkaline but unstable in acidic solution and heat-unstable. In a serum-free medium, IPSF-II alpha stimulated IgM production of human-human and mouse-mouse hybridomas 4-15 and 2-fold, respectively, although its growth stimulatory effect on hybridomas was negligible. The factor did not stimulate IgG production in either human or mouse hybridomas in the same serum-free medium. These results suggested that IPSF-II alpha was a new cellular factor for stimulating IgM productivity of hybridomas.

Increased antigen binding strengths of hybrid antibodies produced by human hybrid hybridomas

Two cell lines of human hybridomas were fused to generate hybrid antibodies. One human hybridoma cell line was HT2 producing IgM monoclonal antibody (MAb) reactive to carboxy peptidase A (Cpase) and double stranded DNA (ds DNA) and another was SU-1-D2 secreting IgM MAb reactive to ds DNA but not to Cpase. Most hybrid hybridomas obtained by fusion of the two hybridomas secreted hybrid antibodies exhibiting increased antigen binding strengths. All of the hybrid antibodies with increased binding strengths against Cpase and ds DNA contained only the light chains derived from SU-1-D2. These results suggested that increase in the binding strength of the hybrid antibodies resulted from heterogeneous association of H and L chains derived from HT2 and SU-1-D2 cells.