Prefiltration enhances performance of sterile filtration for glycoconjugate vaccines

Filtration of a multi-serotype glycoconjugate vaccine drug product through sterilizing grade 0.2/0.22 µm pore size filters

Glycoconjugate vaccines containing multiple serotypes of a bacterial capsular polysaccharide can provide strong immune protection against pathogenic infections. Sterile filtration is an important component of the fill and finish operations in the preparation of these vaccines, with the capacity of the sterile filter limited by membrane fouling. The objective of this study was to examine the performance of a range of commercial 0.2/0.22 µm nominal pore size sterilizing grade filters with both single-layer and dual-layer structures during filtration of a glycoconjugate vaccine drug product consisting of four polysaccharide serotypes. The highly asymmetric Millipore Express showed much higher capacity than the more homogeneous filters, with the support structure of the Express acting as a prefilter that was able to remove foulants thereby protecting the small pores in the size-selective skin layer. This behavior was confirmed by performing experiments with different batch prefilters and by examining the location of foulant deposition within the sterile filters using confocal microscopy. These results provide important insights into the factors controlling fouling by these multiserotype vaccines as well as a framework for increasing the capacity of the sterile filter.

Scale-Up Issues During Sterile Filtration of Glycoconjugate Vaccines

Several recent studies have provided important insights into the factors controlling the sterile filtration of glycoconjugate vaccines; however, this work has been limited to small-scale disk filters with very uniform flow distribution. The objective of this study was to examine the scale-up of the sterile filtration step using a glycoconjugate drug substance made from a single polysaccharide serotype. Experimental data were obtained during constant flux filtration through 0.22 μm Durapore® polyvinylidene difluoride (PVDF) membranes, both with small discs and with the Opticap® XL2 pleated cartridge. The transmembrane pressure increased rapidly during the glycoconjugate filtration due to membrane fouling, with the rate of pressure increase being more pronounced in the pleated cartridge. Additional insights into the fouling behavior were obtained using confocal microscopy by in situ labeling of the glycoconjugate captured within the filter media using an Alexa Fluor fluorescent dye. Glycoconjugate deposition occurred only within the first 5-15 μm of the 0.22 μm Durapore® membrane at both scales, with more variability in the deposition pattern observed for the pleated filter due to the non-uniform flow distribution in the Opticap® XL2 cartridge. These results provide important insights into the underlying fouling behavior during sterile filtration of glycoconjugate vaccines as well as a framework for the scale-up of the sterile filter step in glycoconjugate biomanufacturing. This article is protected by copyright. All rights reserved.