Toward Shorter, More Accurate Testing Times
Improving analytical methods during development and production will aid in optimizing process parameters, improve safety and
efficacy, and reduce batch release times. Label-free interaction analysis based on surface plasmon resonance (SPR) provides
rapid product characterization and unique data to support critical decisions at every step of the vaccine development and
manufacturing process. For example, much emphasis is now being placed on developing effective vaccines against many influenza
types and this requires analysis of the product and control of the breadth of immune responses elicited by such vaccines.
SPR-based interaction systems deliver kinetic data (on and off rates) by monitoring binding events in real-time, providing
greater insights into protein function than from end point assays such as enzyme linked immunosorbent assay (ELISA). Label-free
interaction analysis also can be used to provide accurate concentration measurements. The interaction occurs close to a sensor
surface on which changes in mass concentration are detected, eliminating the need for labels, which may interfere with the
interaction properties.
These systems have also been applied to immunogenicity studies using untreated serum where the build-up of a strong antibody
response mechanism is desired. In one study, an immunization regime designed to elicit an anti-IgE response was optimized
during the development of an immunotherapeutic against allergy and asthma.3 Data from SPR-based analysis have been shown to be more reproducible than techniques such as ELISA and more information
(kinetic quality assessment) can be derived from a single interaction. The ability to detect low–medium affinity antibodies
means that immune responses can be detected earlier.
SPR-based systems are widely applicable throughout the vaccine development and production process (see, for example, the work
from NVI),6 potentially replacing more tedious methods such as bioassays and in vivo tests.
Rapidly Acquired High Data Quality
The benefits of SPR-based systems have led many pharmaceutical and vaccine producers to consider these systems for product
characterization tests to reduce testing times. The replacement of a traditional mouse IgG ELISA assay with an SPR-based test
system can reduce the time per assay run from 7 to 2 hours and ultimately shorten the production workflow by one day.4 More importantly, studies comparing the accuracy of IgG ELISA assays with an SPR-based system in the analysis of monoclonal
antibody (MAb) response in serum revealed a 10-fold improvement in terms of the coefficients of variance.5 These numbers emphasize the potential and relevance of SPR-based systems in batch-release testing of vaccines where a higher
accuracy in testing the final vaccine efficacy would significantly contribute to improved process economics and dose-saving
strategies—both of which are a particular concern in influenza batch-release.
Upstream Process Development That Reduces Capital Expense
The motivation to shift from egg-based to cell-based production capacity results primarily from the fact that egg-based capacity
cannot be scaled up further in times of emergency, largely because of its reliance on specially prepared and treated eggs.
In contrast, cells can be frozen in advance and large numbers may be grown quickly. Capacity can also be increased by adding
fermenting equipment. The footprint for cell culture-based vaccine production is considerably smaller, and processing takes
place in closed systems. Cell-based influenza vaccines also provide an option for people who are allergic to eggs and are
therefore unable to receive currently-licensed vaccines.7,8,9
The productivity of large-scale cell culture can be increased either by scaling up to larger volumes with cell densities of
2–3 x 106 /mL, or by intensifying the process in smaller volumes but with higher cell densities (up to 2 x 108 cells/mL). When intensifying cell densities, more frequent media changes are needed and perfusion is eventually applied.10
Many alternative technologies are available. Cross-linked dextran beads (microcarriers) provide an extended surface and a
stable environment for optimal cell growth. Microcarrier culture of anchorage-dependent or entrapped cells reduces volume
and thus belongs to the latter of the options cited above.1 The technique in general has many advantages for the commercial manufacturer. It can be operated in batch or perfusion modes
during cell culture and is well-suited to efficient process development and smooth scale-up. Washing and changing culture
media just before viral infection is easier. The reactors can also be modified to grow other organisms.
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