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Journal of Virology, December 2000, p. 11456-11463, Vol. 74, No. 24
CNS Gene Therapy Center, Department of
Neurosurgery, Thomas Jefferson University, Philadelphia,
Pennsylvania 19107
Received 27 June 2000/Accepted 14 September 2000
Recombinant adeno-associated virus (rAAV) is capable of directing
long-term, high-level transgene expression without destructive cell-mediated immune responses. However, traditional packaging methods
for rAAV vectors are generally inefficient and contaminated with
replication-competent AAV (rcAAV) particles. Although wild-type AAV is
not associated with any known human diseases, contaminating rcAAV
particles may affect rAAV gene expression and are an uncontrolled variable in many AAV gene transfer studies. In the current study, a
novel strategy was designed to both optimize AAV rep gene
expression and increase vector yield, as well as simultaneously to
diminish the potential of generating rcAAV particles from the helper
plasmid. The strategy is based on the insertion of an additional intron in the AAV genome. In the AAV infectious clone, the intron insertion had no effects on the properties of Rep proteins expressed. Normal levels of both Rep and Cap proteins were expressed, and the replication of the AAV genome was not impaired. However, the generation of infectious rcAAV particles using intronized AAV helper was greatly diminished, which was due to the oversized AAV genome caused by the
insertion of the artificial introns. Moreover, the rAAV packaging was
significantly improved with the appropriate choice of intron and
insertion position. The intron is another element that can regulate the
rep and cap gene expression from the helper
plasmid. This study provides for a novel AAV packaging system which is highly versatile and efficient. It can not only be combined with other
AAV packaging systems, including rep-containing cell lines and herpes
simplex virus hybrid packaging methods, but also be used in other
vector systems as well.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
High-Titer, Wild-Type Free Recombinant
Adeno-Associated Virus Vector Production Using Intron-Containing
Helper Plasmids
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Corresponding author. Mailing address: CNS Gene Therapy
Center, Department of Neurosurgery, Thomas Jefferson University, 1025 Walnut St., Ste. 511G, Philadelphia, PA 19107. Phone: (215) 955-1345. Fax: (215) 955-9629. E-mail: xiwst{at}med.unc.edu.
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