Figure 5. Reverse-phase HPLC peak identification of proteins in the A/Brisbane H1N1 strain of a virus-like particle
An alternative method based on reverse-phase HPLC of VLP samples is being developed to identify the proteins in VLP lots.
The protein peaks are identified either by Western blot using specific antisera or by fraction collection and analysis by
mass spectrometry. A typical VLP profile with currently identified protein peaks is presented in Figure 5. Currently, this
method can identify the influenza HA, NA, and M1 proteins as well as the baculovirus gp64 protein.
During clinical development, a stability testing program is established to 1) demonstrate vaccine stability during the time
it is administered to volunteers and 2) begin to collect data to allow the assignment of vaccine shelf life upon approval
Table 6. Stability testing results of 60 µg HA/mL dose of trivalent 2008–2009 influenza VLP vaccine
Table 6 presents 12-month stability data generated for the 60 µg HA/mL VLP lot of 2008–2009 trivalent seasonal VLP vaccine
administered to healthy adults in a clinical trial (Table 2). The analytical testing parameters that were followed were 1)
particle size, 2) SRID HA value for each strain in the vaccine, 3) vaccine purity/identity by SDS–PAGE and Western blot and
4) total NA activity. These measurements allow us to track potency and physical characteristics of the vaccine over the course
of the study. The results demonstrated no change in the physical properties of the vaccine over 12 months and showed stability
of the HA potency for all three components and consistent NA activity over the 12-month study.