Process integration in manufacture of viral products

Live viral vaccines and therapeutics are growing in popularity due to their high specific potency yet their manufacture remains hampered by poor recoveries of viral infectivity following concentration and purification. In particular, practitioners highlight two such difficulties; the poor recovery of infectious virus following sterile filtration and the search for high yielding purification techniques. These related problems derive primarily from viral inactivation by fluid shear and interfacial phenomenon in the membrane modules and chromatography equipment commonly used by industry. We seek to understand the mechanisms of viral inactivation in order to design new processing systems that provide higher recoveries and are simple to use. Experiments will be conducted to characterise the key morphological and functional characteristics of representative enveloped and non-enveloped viruses (using Ad5 and MoMULV) following exposure to well characterised fluid shear typical of of that encountered during sterile filtration and chromatography. Measurement of viral infectivity will be made (TCID50) and electron microscopy, immunogold labelling and real time PCR will be used to assess the influence of shear on the external viral proteins that mediate infectivity. All these analytical techniques are available in the academic partner's laboratory where the general approach has been previously shown valuable for the study of viral inactivation during lyophilisation. The effect of stabilising excipients and rheology modifying agents will be examined . CFD data on shear distributions in commercial filter housings will be obtained to guide these studies. Sterile filtration yields will be assessed for prototype membranes with a range of porosities, morphologies and surface properties in order to assess the influenec of membrane characteristics upon viral inactivation. The distribution of representative nanoparticles on membranes will be studied using fluorescent labelled HSA particles and confocal imaging. As a result, housing designs will be modified to reduce any maldistribution of viruses. Prototype filter assemblies will be similarly probed with fluorescent immuno-labelled viruses and confocal microscopy. From these studies improved sterile filtration equipment and procedures will result. Complete prototype disposable virus manufacturing systems will be fabricated using collections of commercially available units. Typically, cell culture in disposable bioreactors, including Wave, will be linked by adsorptive and size based membrane processing cartridges and the manufacturing performances of these systems will be characterised for the test viruses. The academic partner is familiar with such approaches, having previously adopted similar approaches for the manufacture of antibody based snake antivenoms in a BBSRC sponsored project. The industrial partner is a market leader in filtration and separations and has relevant process separation technologies for exploitation in this area. Limitations in processing capability will be identified using existing systems and new systems designed to provide improved performance. We anticipate that radical improvements will emerge from the re-designed cartridge housings that result from data obtained on the influence of fluid shear on infectivity. We expect too that the understanding of interfacial phenomena together with new materials that are emerging from the laboratories of the industrial partner will enable significantly higher viral recoveries to be achieved.