Rapid vaccine development using a micro-scale platform

Vaccine research and development is becoming increasingly important because of the potential to create a blockbuster drug, such as Prevnar. However, the development pipeline continues to be a limiting factor in commercialising a vaccine. In this thesis a micro-scale platform is created to mimic the key features of a unit operation so that it is possible to calculate the impact of a commercial manufacturing process using this scaled down platform. Two model vaccines were applied to the micro-scale platform, a new Meningitis serogroup B vaccine based on the outer membrane vesicle proteins of Neisseria lactamica and the licensed UK Anthrax vaccine. To create the platform, cultures of Neisseria lactamica in microwells have been combined with statistical techniques such as Design of Experiments to increase biomass production by four fold and antigen yields by 165%. Microwell experiments were coupled with SELDI-TOF mass spectroscopy to enable a detailed insight into the changing vaccine composition with culture conditions. Microwell results here were scaled up to 2, 8 and 50 litre fermentations using dimensionless analysis based on the oxygen mass transfer co-efficient, kLa. The effects of pilot scale downstream processing were investigated using ultra scale down tools and models. It was possible to characterise product losses and the robustness of the process stream by conducting shear experiments. Furthermore, final product filter sterilisation was investigated using a microwell platform coupled with statistical analysis, particle sizing and DLVO theory. Through these studies it was possible to minimise aggregation and increase antigen transmission through the membrane from 35% to 78%. The platform was applied to cultures of Bacillus anthracis Sterne 34F2, the Anthrax vaccine strain. Microwells were used to mimic Thompson bottle cultures and ascertain the main factors which effect B. anthracis growth and antigen production. The cell density dependent signalling mechanism, known as quorum sensing was found to control growth and antigen production in B. anthracis and that a protein below 5kDa may be involved in the quorum sensing mechanism along with the auto inducer molecule, AI-2. Finally, transfer of B. anthracis vaccine production from static culture to a homogenous stirrer tank culture environment was investigated using a miniature bioreactor. It found that transfer was possible and that doing so reduced the culture time from 28 hours to just 14 hours, increasing production of PA and LF vaccine antigens by 25% and 78% respectively. Aeration of the culture showed that biomass production could be improved upon, but it had a detrimental effect on antigen expression