membrane suppliers or some change for the carriers used. Finally, even chemically

defined medium can have quite some variations.

Small changes in cell maintenance or preculture handling can equally have an

impact on the performance of the cells in a bioreactor, for example. Cultivation in

different vessels can lead to changes in aeration, mixing and shear conditions which

will certainly influence metabolism and cell growth performance. After infection,

either a very fast onset of cell lysis or almost no cell lysis can be observed or

increased foaming, increased oxygen demand or significant changes in metabolism.

Transfer of cells through tubings also might need thorough analysis: The inner

diameter of tubes, changes in the inner diameter of connectors, squeezing of tubes,

tube materials that are air permeable or not, choice of pumps, length of tubing, etc.

Sometimes the CO2 incubator might be the reason for troubles. For instance,

someone placed additional equipment or flasks into the incubator that otherwise is

not present. This results in temperature gradients or an additional heating from the

equipment, and the cells do not grow at the optimal temperature anymore.

Recalibrating the pH sensor during a bioreactor run, because of an off-set between

online and off-line measurement can also cause trouble. For some products a shift

of pH as low as 0.1−0.2 can result in changes in growth properties, antigen gly-

cosylation, or reduce virus production.

Nevertheless, while all this seems to give the impression that animal cell culture

and virus production is coping only with troubles, this is not the case. Strict rules

regarding the quality control performed by the companies, detailed documentation

and regulations, and the implementation of backup solutions have strongly im-

proved vaccine quality and consistency.

5.9

CMC AND GMP CONSIDERATIONS RIGHT FROM THE START

Any development of a new vaccine starts at the research and discovery stage.

Initially, scientists developing new vaccine candidates focus on mechanisms of the

infectious organism causing disease. Laboratory research is conducted in vitro and

in vivo until a feasible vaccine candidate for further development is found, often

lasting 2−4 years. Additional research seeking options for establishment of

laboratory-scale processes that allow to produce enough material for testing in

animals to obtain first safety and mechanism of action data is performed. Finally, a

process is established that enables large-scale manufacturing of the vaccine. Before

a new vaccine can be administered to humans, the sponsor has to file an IND

(investigational new drug application) in the United States of America or a CTA

(clinical trial application) in the European Union (Figure 5.7). Latest at this point,

academic research groups will discover that their production process proposed has

to be GMP certified (good manufacturing practice or minimum “GMP ready”) and

provide all required “chemistry, manufacturing, and controls” information (CMC).

In contrast to chemical pharmaceuticals, biological products including vac-

cines are inherently more difficult to manufacture due to their derivation from

cellular sources. Because manufacturing requires the propagation of the im-

munizing agents (e.g., viruses, VLPs, recombinant proteins, etc.) in cellular

sources, the complexity to establish optimal conditions for growth, and

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Bioprocessing of Viral Vaccines