STABILITY OF ANTIBODY PRODUCTIVITY IS IMPROVED WHEN HYBRIDOMA CELLS ARE ENTRAPPED IN CALCIUM ALGINATE BEADS

Loss of monoclonal antibody (MAb) productivity in long-term, free-susp ended cell culture is often attributed to the appearance of a nonprodu cing population of hybridoma cell (NP) in the culture which has a grow th advantage over the producing population (P). However, when an NP ap pears in long-term culture of entrapped cells, it may not be able to t ake over the whole culture in a short period of time due to the limite d growth of the entrapped cells. In order to examine the hypothesis th at entrapped cells can have improved stability of MAb productivity due to limited cell growth, free-suspended cell culture and calcium algin ate-entrapped cell culture with inocula consisting of a P and an NP we re compared with regard to stability of MAb productivity in a repeated fed-batch culture. In free-suspended cell culture, the NP appeared to take over the whole culture within three batches, and thereby MAb pro duction completely disappeared. In entrapped cell culture, an NP appea red to outgrow the P rapidly only during an exponential growth phase, resulting in a significant decrease in specific MAb productivity, q(MA b), from 11.58 mug/10(6) cell/day to 2.76 mug/10(6) cell/day. However, when the cell growth was limited in entrapped cell culture, the NP no longer outgrew the P rapidly, as indicated by the stable value of q(M Ab). In addition, when the cells recovered from the alginate beads by citrate buffer treatment were subcultured in free-suspended cell cultu re, MAb production rapidly deteriorated and completely disappeared wit hin two batches. Thus, the P present at a small fraction of viable cel l concentration in the beginning of the free-suspended cell culture, w hich were previously entrapped in alginate beads, seemed to be outgrow n rapidly by the NP. Taken together, the results obtained from these e xperiments support the hypothesis that the limited cell growth in entr apped cell culture, which keeps an NP from taking over the whole cultu re, is responsible, in part, for the improved stability of MAb product ivity. (C) 1993 John Wiley & Sons, Inc.