title: High Frequency of Homologous Recombination in the Genome of Modified Vaccinia Virus Ankara Strain (MVA).
abstract: MVA is a genetically modified vaccinia virus strain, which is replication defective and extremely safe for research and clinical use. To further improve the safety of MVA and achieve more efficient selection of recombinant constructs, a transient selection marker system has been developed, which contains vaccinia virus k1l gene flanked by two identical fragments. In this report, four recombinant MVAs were constructed with this system, and homologous recombination of recombinant MVAs was studied during the construction procedure. The results showed that the recombination frequency of these rMVAs was significantly high, though lower than that observed in other vaccinia virus strains. The k1l free rMVAs could be conveniently obtained after 3 or 4 blind passages. Our data indicated that recombinant MVA with a transient selection marker system was safe for use as live vaccine and gene therapy vector for human. In addition, blind passages could enhance the efficiency in isolation of k1l free recombinants
authors.affiliation: Institute of Biochemistry and Cell Biology, Shanghai Institutes for BiologicalSciences, the Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Li-Xin
authors.initials: LX
authors.lastname: Zhu
authors.forename: You-Hua
authors.initials: YH
authors.lastname: Xie
authors.forename: Guang-Di
authors.initials: GD
authors.lastname: Li
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang