Improving the efficiency of CHO cell line generation using glutamine synthetase gene knockout cells.

Although Chinese hamster ovary (CHO) cells, with their unique characteristics, have become a major workhorse for the manufacture of therapeutic recombinant proteins, one of the major challenges in CHO cell line generation (CLG) is how to efficiently identify those rare, high-producing clones among a large population of low- and non-productive clones. It is not unusual that several hundred individual clones need to be screened for the identification of a commercial clonal cell line with acceptable productivity and growth profile making the cell line appropriate for commercial application. This inefficiency makes the process of CLG both time consuming and laborious.

Root Cause Investigation of Unusual Results Experienced during Master Cell Bank (MCB) Testing and Characterization.

We experienced two cases of unexpected results during master cell bank (MCB) testing and characterization at two individual testing companies over the last 5 years. Investigation was launched immediately upon receiving notice from the testing companies involved in an attempt to determine the root cause. In the first case, potential viral contamination of the MCB was suspected based on results from the cell-based in vitro viral screening.