CHARACTERIZATION OF A RECOMBINANT ANTIBODY PRODUCED IN THE COURSE OF A HIGH-YIELD FED-BATCH PROCESS

Many mammalian cell fed-batch processes rely on maintaining the cells in a viable and productive state for extended periods of time in order to reach high final concentrations of secreted protein. In the work d escribed herein, a nonamplified NSO cell line was transfected with a v ector expressing a recombinant human anti-HIV gp120 monoclonal antibod y (MAb) and a selectable marker, glutamine synthetase. A fed-batch pro cess was developed which improved product yields tenfold over the yiel ds reached in batch culture. In this case, the clone was cultured for a period of 22 days and produced 0.85 g MAb/L. To gauge the effect of extended culture lifetime on product quality, biochemical characterist ics of MAb isolated from different time points in the fed-batch cultur e were determined. The apparent molecular weight of the MAb was consta nt throughout the course of the culture. Isoelectric focusing revealed four major charged species, with a fifth more acidic species appearin g later in the culture. The antigen binding kinetics were constant for MAb isolated throughout the culture period. Glycosylation analysis, o n the other hand, revealed that MAb produced later in the culture cont ained greater percentages of truncated N-acetylglucosamine and high-ma nnose N-glycans. Possible contributions to this underglycosylated mate rial from either cell lysis or synthesis from nonviable cells were fou nd to be negligible. Instead, the viable cells appeared to be secretin g more truncated and high mannose MAb glycoforms as the culture progre ssed. (C) 1994 John Wiley & Sons, Inc.