Downstream processing of recombinant retroviral vectors

Authors: Mercèdes Segura, Maria de las
Advisor: Garnier, Alain; Kamen, Amine A.
Abstract: Retroviral vectors derived from the Moloney murine leukemia virus (MoMLV) have been used as gene delivery vehicles for more than two decades and continue to be the best available tool for stable and efficient transfer of therapeutic genes into various cell types. Although most gene therapy preclinical studies use crude or concentrated retroviral vector supernatants, purification to eliminate serum and host-derived impurities contained in these stocks is a must for clinical applications. This thesis describes the development of downstream processing strategies for retroviral vectors. During the course of this project, two complete multi-step purification schemes (from crude retrovirus supernatant to clinical-grade virus) were designed, tested and their performance analyzed in detail. Membrane filtration contributed to the clarification, concentration, buffer exchange and partial purification of retroviral particles from crude supernatants with essentially no loss in vector infectivity. Two novel purification methods specifically tailored to the biochemical and physical features of retroviral particles were developed. The first method consists of the chromatographic purification of retroviral particles by heparin affinity chromatography followed by size exclusion chromatography. The main advantage of employing chromatography technology for virus purification is that it offers the possibility to selectively and efficiently purify retroviruses on a large-scale. Moreover, heparin affinity chromatography resulted in exceptional recoveries of infective particles and proved to be useful for the purification of retroviral vectors produced by different packaging cell lines independently of the Env-protein used for pseudotyping. The second purification method is based on a rate zonal centrifugation technique using iodixanol as gradient medium. The power of this technique was revealed by the high levels of purity achieved in a single purification step and its potential to separate viral particles from closely-related species such as defective vector forms and/or cell membrane vesicles, all of which pose a serious challenge in downstream processing. The overall yield of infective particles (~38%) and level of purity achieved (over 95%) using either purification strategy was comparable. The methods described in this thesis represent a significant improvement over the conventional sucrose density gradient methodology used for retrovirus purification and will hopefully contribute to the technological progress in the field of gene therapy.
Document Type: Thèse de doctorat
Issue Date: 2006
Open Access Date: 12 April 2018
Grantor: Université Laval
Collection:Thèses et mémoires

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