The project seeks to exploit molecular biology to construct designer viruses that are structurally adapted for simple affinity purification and hence easier manufacture. The Gene Medicine web site shows that viruses are currently used in two-thirds of all gene therapy trials, with retro- and lentiviruses constituting ~40% of these. Chromatography is preferred for vector purification and ion-exchange has been used in the multi-step purification of a lentiviral vector for a Phase 1 clinical trial. Precedence in protein manufacturing shows that such low specificity processes are now almost entirely superseded by affinity processes and this preference will likely emerge in virus manufacturing in order to exploit the resolution and simplicity of affinity chromatography. Recognising this we engineered a novel packaging cell line, Bio-293T, that metabolically produces an affinity-tagged lentivirus and we have demonstrated the enormous efficiency savings and flexibility offered by affinity capture for virus concentration. This first generation Bio-Lentivir packaging cell line has highlighted the inadequacy of conventional matrices for virus affinity purification, the critical need to optimise affinity-tag density on the viral envelope for efficient recovery and the potential of novel macroporous adsorbents to provide simple, single-step processing. It has also shown that biotin-tagged lentivirus can be complexed with streptavidin paramagnetic particles, resulting in the most efficient isolation and concentration method yet described for lentiviral vectors. However, most clinical applications require free virus, for which use the paramagnetic nanoparticle capture approach is unsuitable without virus elution, which, for this high affinity system leads to low process yields. Following our proof-of-concept there is consequently a need for a second generation Bio-Lentivir packaging cell line designed to ovecome these limitations and fully exploit the potential for the efficient production of high titre, highly purified, clinical grade retroviral and lentiviral gene transfer vectors.The project outputs will be novel His-tag/Bio-Lentivir packaging cell lines, new adsorbent materials for virus purification and an integrated virus production scheme. These objectives stem from the joint experience of the Kings and Cambridge teams on the successful development of the Bio-293T packaging cell line and will be addressed by bringing together expertise in molecular biology, vector design and packaging cell line construction (at Kings) with bio-materials, virus and affinity processing expertise (at Cambridge).
