An Alternative Approach: Baculovirus Production in Disposable Equipment
Novavax, Inc. (Rockville, MD), is developing a novel, recombinant vaccine using cell culture to rapidly produce three proteins
specific to an emerging influenza strain that self-assemble into an enveloped, non-infectious particle (virus-like particle
or VLP) resembling the influenza virus. The approach provides vaccine within 10 to 12 weeks of identification of the new strain
and provides an exact match to the wild-type influenza strain. Yields are significantly higher than egg and mammalian cell
culture production. The high yields and use of a nonpathogenic baculovirus allows production in disposable manufacturing equipment.
The use of disposables radically lowers facility costs, making the solution affordable to many governments. These advantages
are explained below.
The time required to manufacture this insect-cell based vaccine is 10–12 weeks, as shown in Figure 1. This time includes four
weeks to make recombinant baculovirus production seed stock from the native influenza virus DNA or from the DNA sequence identified
by the relevant health agencies, such as the Centers for Disease Control or the World Health Organization. These seed stocks
are used to make manufacturing lots starting in week 5. In parallel, recombinant hemagglutinin (HA), neuraminidase (NA), and
matrix (M1) protein are made for the generation of reagents needed for lot-release testing. During weeks 8 to 10, vaccine
lots, which have been in production since week 5, are formulated, filled, and packaged for distribution, with release expected
in weeks 10 to 12. This is approximately the same time that the first pandemic wave of disease will peak, so having vaccine
available this quickly offers the potential to halt the pandemic in its tracks. Traditional manufacturing processes, in contrast,
require preparation of a nonpathogenic virus (because an avian virus would kill the fertile egg used in production), and then
production of materials used to make reagents. Only when these reagents are available can vaccine be released. The traditional
process in this case takes at least 20 to 24 weeks, which means that vaccine is not available until the second wave of pandemic
disease, after much of the damage has been done.
Figure 1. The insect-cell based vaccine can be ready in 10–12 weeks, compared to 24 for a traditional method. Part of the
time savings is achieved by preparing the reagants for lot-release testing while the vaccine is in production.
The insect-cell production system also has a very high productivity compared to traditional approaches (Figure 2). Yields
in the production of HA are 7–10 times higher (in grams of protein per volume of production lot) than with traditional methods.
These high yields make it possible to use small disposable reactors (1,000–2,000 L) instead of 20,000-L reactors needed for
mammalian cell culture production. The system developed for making Phase 1 and Phase 2 clinical lots uses 200-L Wave reactors
(GE Healthcare, Uppsala, Sweden) for the production of VLPs, followed by a series of purification steps that are also executed
in disposable equipment. The current high yields are expected to increase as high-performance disposable stirred reactors
(Xcellerex Inc., Waltham, MA) are used to scale up the process to 1,000 L for commercial production. Higher gas transfer rates
are expected to support higher insect cell culture densities, thus providing higher volumetric productivity. Further, clinical
testing to date has shown that much smaller doses of the VLP vaccine are needed to match the effectiveness of licensed pandemic
vaccines (without the use of adjuvants). This means that the yield advantage is further magnified to >40-fold higher productivity
in terms of doses of vaccine per liter of cell culture.
Figure 2. Relative yield from traditional vaccine production compared to baculovirus production of a virus-like particle (VLP)
based vaccine. Because the VLP vaccine is effective at a much lower dose, the effective yield of the baculovirus production
system is 42 times higher.