Anàlisi d'alternatives per un bioprocés de producció d'una vacuna animal

Abstract

In the present work, the development of a production process for a recombinant vaccine against IBD (Infectal Bursal Disease), a disease that affects industrial hens and chickens, has been studied. Based on different biological systems we investigated alternative systems in order to compare them in terms of economical valuation and technical viability, two important criteria that have to be considered when establishing a bioprocess in industrial scale. The first approach undertaken was the propagation of the IBD virus by infection of Vero cells, a conventional method for vaccine production that usually requires a subsequent attenuation of the virus obtained. Since this kind of system is a relatively standardised one and already applied to the production of many different types of viruses in industrial scale, it was chosen as a reference system. The following chapters deal with the analysis of three alternative processes of recombinant vaccine production compared to the reference system. In these alternative systems the viral agent is not the virus itself, but one of its capsid proteins, VP2, that has been identified to evoke an adequate immunological response in animals. For this reason obtaining a recombinant VP2 protein would permit the development of vaccines with enhanced safety regarding process manipulation, the protein itself and its application. Chapter 5 describes the production of VP2 in the baculovirus and insect cell (Sf9) expression system. In Chapter 6, the expression of VP2 in both bacteria (E. coli) and yeast (P. pastoris) was studied. In spite of efforts to produce VP2 in both systems, it was only shown to be produced in E.coli with the help of a fusion protein. However, this was without obtaining stable clones. In order to analyse the production potential of using these expression systems, a new strategy was developed utilising ?-galactosidase as a model protein instead. The cultivation systems for the expression of ?-galactosidase are described in Chapter 7 (P. pastoris) and Chapter 8 (E.coli). Although expression of the primary desired protein was not possible, , the data obtained gave relevant information regarding this kind of production bioprocesses and may facilitate in establishing a comparative analysis of these alternative expression systems. Finally, Chapter 9 gives an overview of the study by comparing the four production strategies previously described. The comparative study was based on a large scale industrial bioprocess design. To define the industrial facility dimension, 10% of the annual demand of this vaccine in Europe was assumed in the implemention of our experimental data. The economical analysis of the feasibility ought to permit to describe the hotspots and the advantages of each alternative production system, and to overcome bottlenecks in further studies.