Biology Reference
In-Depth Information
lines for genetically engineered cells. Development begins with the creation of
genetically engineered cells that produce the desired product, and ends with a
cell bank,a homogeneous population of genetically engineered cells frozen at
the same population doubling level.
Cell bank
Once a cell line has been identified as the manufacturing line, a cell bank must
be generated. The cell bank provides the starting material for all lots of prod-
uct manufactured. For this reason, it is carefully scrutinized from both a busi-
ness and regulatory perspective.
Once a homogenous population of cells (“cell bank”) is created, a master
cell bank is made. The master cell bank is the base starting material for the life-
cycle of the product. Cell banks are created in a two-tier system (Fig. 1). Each
vial of master cell bank material can be used to create a working cell bank.
Likewise, a single vial provides the starting material for a commercial cell cul-
ture lot.
Single-cell cloning
The industry standard for generating a homogenous population is single-cell
cloning. Single-cell cloning is accomplished by placing one cell in a micro-
culture environment, and then expanding that cell through increasingly larger
cultures to generate a greater number of cells (e.g., 1
10
9
cells) (Fig.2).
Doubling of a single cell should produce two identical cells. Doubling again
results in four cells that are assumed to be identical. Within a limited number
of generations, expansion of the cells in this manner results in a homogenous
culture of cells with identical genomes. When sufficient cells are amassed, a
premaster cell bank of approximately 25 vials is frozen.
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Two-tier system: creation of master and working cell banks
A two-tiered approach is commonly used in industry to generate a supply of
cell bank vials for the lifetime of a product. The master cell bank is generated
first and typically consists of 200 to 400 vials. The master cell bank is not used
by the manufacturing facility directly. Instead,the second-tier cell bank,the
working cell bank, is used by the manufacturing facility. The working cell
bank is generated by expanding one vial of material from the master cell bank.
The working cell bank typically contains 500 to 1,000 vials.
