At our facility, the main objective of this testing is to confirm the identity, purity, and suitability of the cell substrate for manufacturing use. The testing program chosen for a given cell bank will vary according to the biological properties of the cells (for example, growth requirements), its cultivation history (including use of human-derived and animal-derived biological reagents) and available testing procedures.

The characterization and testing of the cell banks are critical components of the control of biotechnological and biological products. Characterization of the MCB will allow us to assess this source with regard to presence of cells from other lines, adventitious agents, endogenous agents and molecular contaminants (e.g., toxins or antibiotics from the host organism).

Production of the recombinant protein would be based on well-defined Master and Working Cell Banks. A cell bank is a collection of ampoules of uniform composition stored under defined conditions each containing an aliquot of a single pool of cells. The Master Cell Bank (MCB) is generally derived from the selected cell clone containing the expression construct.

The Working Cell Bank (WCB) is derived by expansion of one or more ampoules of the MCB. The cell line history and production of the cell banks would be described in detail, including methods and reagents used during culture, in-vitro cell age, and storage conditions. All cell banks would be characterized for relevant phenotypic and genotypic markers which could include the expression of the recombinant protein or presence of the expression construct.

The extent of characterization of a cell bank may influence the type or level of routine testing needed at later stages of manufacturing. Manufacturers should perform tests for identity and purity once for each MCB, and tests of stability during cell cultivation.

Technology innovation and advancement

Our facility will employ “state-of-the-art” methods and technological improvements in cell bank characterization and testing as they become available, as long as the specificity, sensitivity, and precision of the newer methods are at least equivalent to those of the existing method.

Characterization of expression vectors and encoded proteins

Restriction endonuclease mapping or other suitable techniques would be used to analyze the expression construct for copy number, for insertions or deletions, and for the number of integration sites. For extrachromosomal expression systems, the percent of host cells retaining the expression construct should be determined.

The protein coding sequence for the recombinant protein product of the expression construct would be verified. For extrachromosomal expression systems, the expression construct would be isolated and the nucleotide sequence encoding the product would be verified without further cloning. For cells with chromosomal copies of the expression construct, the nucleotide sequence encoding the product would be verified by recloning and sequencing of the chromosomal copies.