title: Retroviral vector performance in defined chromosomal Loci of modular packaging cell lines.
abstract: The improvement of safety and titer of retroviral vectors produced in standard retroviral packaging cell lines is hampered because production relies on uncontrollable vector integration events. The influences of chromosomal surroundings make it difficult to dissect the performance of a specific vector from the chromosomal surroundings of the respective integration site. Taking advantage of a technology that relies on the use of packaging cell lines with predefined integration sites, we have systematically evaluated the performance of several retroviral vectors. In two previously established modular packaging cell lines (Flp293A and 293 FLEX) with single, defined chromosomal integration sites, retroviral vectors were integrated by means of Flp-mediated site-specific recombination. Vectors that are distinguished by different long terminal repeat promoters were introduced in either the sense or reverse orientation. The results show that the promoter, viral vector orientation, and integration site are the main determinants of the titer. Furthermore, we exploited the viral production systems to evaluate read-through activity. Read-through is thought to be caused by inefficient termination of vector transcription and is inherent to the nature of retroviral vectors. We assessed the frequency of transduction of sequences flanking the retroviral vectors from both integration sites. The approach presented here provides a platform for systematic design and evaluation of the efficiency and safety of retroviral vectors optimized for a given producer cell line.
authors.affiliation: Helmholtz Center for Infection Research (HZI), 38124 Braunschweig, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Gama-Norton
authors.forename: S
authors.initials: S
authors.lastname: Herrmann
authors.forename: R
authors.initials: R
authors.lastname: Schucht
authors.forename: A S
authors.initials: AS
authors.lastname: Coroadinha
authors.forename: R
authors.initials: R
authors.lastname: Löw
authors.forename: P M
authors.initials: PM
authors.lastname: Alves
authors.forename: C C
authors.initials: CC
authors.lastname: Bartholomae
authors.forename: M
authors.initials: M
authors.lastname: Schmidt
authors.forename: C
authors.initials: C
authors.lastname: Baum
authors.forename: A
authors.initials: A
authors.lastname: Schambach
authors.forename: H
authors.initials: H
authors.lastname: Hauser
authors.forename: D
authors.initials: D
authors.lastname: Wirth
mesh_terms: D002460:Cell Line / Q000378:metabolism*; D002875:Chromosomes; D018390:Gene Targeting; D056426:Genetic Loci; D015316:Genetic Therapy / Q000379:methods; D005822:Genetic Vectors / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012190:Retroviridae / Q000235:genetics* / Q000502:physiology; D014161:Transduction, Genetic; D019065:Virus Assembly; D016662:Virus Integration