manufacturing process prohibitively expensive. One alternative to using nucleases

with lytic viruses, such as adenoviruses being used to produce SARS-CoV-2 vac-

cines candidate is to use flocculants and centrifugation. Centrifuges that operate by

balancing out centrifugal force and medium flow to keep cells contained in an

expanded bed are recommended, as these exert lower shear forces on the viral

product to minimize loss of infectivity. If classic filter trains do not work or a huge

surface area is required, centrifugation is advised as the first step in cell harvest for

high cell density as it reduces the filter area, eliminating pre-rinse steps to efficiently

separate cells, enabling the use of smaller footprint facilities where less buffer

volume and buffer storage are required. A suitable centrifuge for this application is

the kSep® single-use (Sartorius Stedim), sterile centrifuge, or similar system such as

Unifuge® (Pneumatic Scale Angelus).

For example, in the DSP purification different approaches can be taken to in-

tensify the process [79]. With high binding capacity in mind, membrane adsorbers

can be used in place of conventional resin-based affinity chromatography for the

purification of VBVs [80]. Membrane adsorbers with beads that have large pore

sizes (3–5 μm) are recommended as these provide maximum ligand accessibility for

viruses and eliminate the need for diffusion through resin pores. Membrane ad-

sorbers with large pore sizes such as Sartobind® Q or Mustang® Q can operate at

volumetric flow rates that are typically 20-fold higher than classical resins. Studies

with adenovirus have shown that compared to resins, they can achieve a 10-fold

higher viral binding capacity using 58% less buffer, without compromising virus

purity [79,81]. Additionally, a purification process using a NatriFlo® HD-Q mem-

brane enabled the reduction of process time from 9 hours to 30 minutes, still im-

proving the virus’s recovery from 65–70% to 90% [82]. Besides the small features

of the different membrane adsorbers available, the huge and remarkable benefit is

the high productivity with the smallest footprint.

In addition to continuous centrifuges and membrane absorbers or other convective

media (Monolith, fiber technologies, etc.), a key role is played by the TFF step.

Usually, tangential flow filtration is a unit operation that can add a significant portion

to the cost of goods. With this respect, the use of SPTFF can greatly reduce the buffer

consumption as well as the operation time for concentration and/diafiltration. Overall

intensified processes are the results of smooth and straightforward unit operation

connection, reducing the overall footprint and increasing the process productivity.

FIGURE 7.7 The three pillars of process intensification with viral-based vaccines (VBVs)

(adapted from “Integrated Technologies to Accelerate Process Intensification for Viral

Vaccine Manufacturing,” Sartorius Stedim).

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Bioprocessing of Viral Vaccines