Innovative Manufacturing Techniques for Polysaccharide-Protein Conjugate Vaccines

There is need for a commercial vaccine against shigellosis because all groups of pathogenic Shigella have acquired resistance to antibiotics. Shigella conjugate vaccines have proven safe and protective in previous clinical trials, but obstacles associated with large-scale manufacturing of these subunit vaccines have apparently hindered commercial development. The present project uses a new and simpler technology for manufacturing shigella conjugate vaccine. The goals of the project are to develop cGMP-manufacturing conditions for the new technology and to use these conditions to produce a clinical lot of refined, conjugate vaccine against Shigella flexneri 2a. The vaccine will contain completely deacylated polysaccharide (PS) from S. flexneri 2a lipopolysaccharide (LPS) and a carrier protein called Proteinase 1. To produce the vaccine, whole cells of S. flexneri 2a are fed to a culture of Dictyostelium cells. During growth on the bacteria, Dictyostelium cells synthesize Proteinase 1 and excrete PS molecules. After bacteria have been depleted in the culture, PS is harvested and purified from the culture media, and Proteinase 1 is extracted and purified from the Dictyostelium cells. The conjugate vaccine is constructed by covalent linkage of purified PS molecules to sugar-phosphate linker groups that occur as natural post-translational groups in Proteinase 1.