Ai. Michou et al., Mutational analysis of the avian adenovirus CELO, which provides a basis for gene delivery vectors, J VIROLOGY, 73(2), 1999, pp. 1399-1410
The avian adenovirus CELO is being developed as a gene transfer tool. Using
homologous recombination in Escherichia coli, the CELO genome was screened
for regions that could be deleted and would tolerate the insertion of a ma
rker gene (luciferase or enhanced green fluorescent protein). For each muta
nt genome, the production of viable virus able to deliver the transgene to
target cells was monitored. A series of mutants in the genome identified a
set of open reading frames that could! be deleted hut which must be supplie
d in trans for virus replication. A region of the genome which is dispensab
le for viral replication and allows the insertion of an expression cassette
was identified and a vector based on this mutation was evaluated as a gene
delivery reagent. Transduction of avian cells occurs at 10- to 100-fold gr
eater efficiency (per virus particle) than with an adenovirus type 5 (Ad5)-
based vector carrying the same expression cassette. Most important for gene
transfer applications, the CELO vector transduced mammalian cells as effic
iently as an Ad5 vector. The CELO vector is exceptionally stable, can be gr
own inexpensively in chicken embryos, and provides a useful alternative to
Ad5-based vectors.