Bacterial polysaccharides, when coupled to an immunogenic protein, have been shown to increase the immunogenicity of meningitis and pneumonia vaccines. Ultrafiltration with semipermeable membranes is often employed to remove any unreacted polysaccharide from the desired conjugated vaccine. Therefore, understanding the ultrafiltration behavior of these biotherapeutics is essential to the development of vaccines against infectious disease. The overall objective of this thesis was to examine the ultrafiltration behavior of a series of pneumococcus polysaccharide serotypes Pn7F, Pn19A, Pn3, and Pn14, provided by Pfizer, with different physical characteristics. The effective sizes of these polysaccharides were determined by size exclusion chromatography (SEC). Ultrafiltration data were obtained in a stirred cell with BiomaxTM polyethersulfone membranes, with samples analyzed using high performance liquid chromatography (HPLC). Data were obtained for a range of membrane pore size, polysaccharide concentrations, and solution ionic strength. The ultrafiltration behavior of Pn7F and Pn19A was largely independent of solution concentration, with the transmission slightly decreasing with increasing polysaccharide concentration. Only Pn19A, the smallest polysaccharide, was able to permeate the 100 kDa pore-size membrane at a high rate, while the other serotypes showed significant fouling at all filtrate flux values. The transmission increased with increasing ionic strength for filtration of the charged serotypes (Pn19A and Pn3) through the 300 kDa membrane. These results provided new insights into the effects of the polysaccharide size and electrical charge on the ultrafiltration characteristics of these important biotherapeutics.
