Evaluation of a sterile filtration process for viral vaccines using a model nanoparticle suspension

There is growing interest in the development of new vaccines based on live-attenuated viruses (LAVs) and virus-like particles. The large size of these vaccines, typically 100–400 nm, significantly complicates the use of sterile filtration. The objectives of this study are to examine the performance of several commercial sterile filters for filtration of a cytomegalovirus vaccine candidate (referred to as the LAV) and to develop and evaluate the use of a model nanoparticle suspension to perform a more quantitative assessment. Data obtained with a mixture of 200- and 300-nm fluorescent particles provided yield and pressure profiles that captured the behavior of the viral vaccine. This included the excellent performance of the Sartorius Sartobran P filter, which provided greater than 80% yield of both the vaccine and model particles even though the average particle size was more than 250 nm. The particle yield for the Sartobran P was independent of filtrate flux above 200 L/m²/h, but increased with increasing particle concentration, varying from less than 10% at concentrations around 10⁷ particles/ml to more than 80% at concentrations above 10¹⁰ particles/ml due to saturation of particle capture/binding sites within the filter. These results provide important insights into the factors controlling transmission and fouling during sterile filtration of large vaccine products.