High Frequency of
Homologous Recombination in the Genome of Modified Vaccinia Virus Ankara Strain
(MVA)
ZHU Li-Xin, XIE You-Hua, LI Guang-Di*, WANG Yuan*
( Institute of Biochemistry and Cell Biology, Shanghai Institutes for
BiologicalSciences, the Chinese Academy of Sciences, Shanghai 200031, China
)
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
Key words recombination frequency； homologous recombination； vaccinia virus； MVA
*Corresponding authors： Tel, 86-21-64374430； Fax, 86-21-64338357； e-mail,
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