In the case of virus production, process performance has to be improved at each

stage of production,starting with upstream processing (USP) with increasing virus

particle yields, CSVY and space-time yield (STY), continuing with purification

strategies with a minimum number of unit operations and high recovery, debot-

tlenecking and optimizing modular solutions for manufacturing [8]. For example,

one general goal of process intensification in USP is to achieve high cell con-

centrations right from the start of thawing the cell bank, thereby reducing the time

to reach the required cell concentrations at the final process scale with a minimum

of scale-up steps (Figure 6.1). Based on high cell concentrations being reached in

the final production vessel, overall virus titers and virus yields can be higher in

case the CSVY can be kept at least constant. In this chapter, we will focus on USP

and the related challenges with the aim to increase viral yields.

6.3

PARAMETERS FOR PROCESS COMPARISON AND EVALUATION

Before addressing advanced concepts for process optimization and intensification,

tools or parameters for an unbiased comparison of virus production platforms are

needed. Therefore, in Table 6.1, the most commonly used measured or calculated

parameters are introduced using IAV as an example.

Standard cell bank

1 mL

10-25 E06 cells/mL

Inoculum train

N

N-1

N-2

N-3

Classical cell expansion for batch process, 3-4 weeks

HCD cell bank

50-500 mL

50-100 E06 cells/mL

CRD

CRD

Seed train

Seed train

N-1

N-2

CRD

N

Production vessel

Production vessel

Intensified production process, <3 weeks

FIGURE 6.1 Comparison of a conventional seed train process with an intensified process

using high-cell density cell banking and perfusion. HCD: high cell density; CRD: cell re-

tention device. Production run (N: cell growth and virus production) and all scale-up runs (N-

1, N-2, etc.) that involve cell growth only. Standard cell banks typically use 1–2 mL cryo

flasks, whereas HCD cell banks use dedicated freezing bags with volumes up to 500 mL.

Created with BioRender.com

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Bioprocessing of Viral Vaccines