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Ribosomal DNA integrating rAAV-rDNA vectors allow for stable transgene expression.

ABSTRACT: Although recombinant adeno-associated virus (rAAV) vectors are proving to be efficacious in clinical trials, the episomal character of the delivered transgene restricts their effectiveness to use in quiescent tissues, and may not provide lifelong expression. In contrast, integrating vectors enhance the risk of insertional mutagenesis. In an attempt to overcome both of these limitations, we created new rAAV-rDNA vectors, with an expression cassette flanked by ribosomal DNA (rDNA) sequences capable of homologous recombination into genomic rDNA. We show that after in vivo delivery the rAAV-rDNA vectors integrated into the genomic rDNA locus 8-13 times more frequently than control vectors, providing an estimate that 23-39% of the integrations were specific to the rDNA locus. Moreover, a rAAV-rDNA vector containing a human factor IX (hFIX) expression cassette resulted in sustained therapeutic levels of serum hFIX even after repeated manipulations to induce liver regeneration. Because of the relative safety of integration in the rDNA locus, these vectors expand the usage of rAAV for therapeutics requiring long-term gene transfer into dividing cells.

SUBMITTER: Lisowski L

PROVIDER: S-EPMC3464642 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

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Ribosomal DNA integrating rAAV-rDNA vectors allow for stable transgene expression.

Lisowski Leszek L Lau Ashley A Wang Zhongya Z Zhang Yue Y Zhang Feijie F Grompe Markus M Kay Mark A MA

Molecular therapy : the journal of the American Society of Gene Therapy 20120918 10

Although recombinant adeno-associated virus (rAAV) vectors are proving to be efficacious in clinical trials, the episomal character of the delivered transgene restricts their effectiveness to use in quiescent tissues, and may not provide lifelong expression. In contrast, integrating vectors enhance the risk of insertional mutagenesis. In an attempt to overcome both of these limitations, we created new rAAV-rDNA vectors, with an expression cassette flanked by ribosomal DNA (rDNA) sequences capabl ...[more]

PMID: 22990671

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Project description:BACKGROUND:The efficacy and biosafety of lentiviral gene transfer is influenced by the design of the vector. To this end, properties of lentiviral vectors can be modified by using cis-acting elements such as the modification of the U3 region of the LTR, the incorporation of the central flap (cPPT-CTS) element, or post-transcriptional regulatory elements such as the woodchuck post-transcriptional regulatory element (WPRE). Recently, several studies evaluated the influence of the incorporation of insulators into the integrating lentiviral vector genome on transgene expression level and position effects. METHODS:In the present study, the influence of the matrix attachment region (MAR) of the mouse immunoglobulin-? (Ig-?) or the chicken lysozyme (ChL) gene was studied on three types of HIV-1-derived lentiviral vectors: self-inactivating (SIN) lentiviral vectors (LV), double-copy lentiviral vectors (DC) and non-integrating lentiviral vectors (NILVs) in different cell types: HeLa, HEK293T, NIH-3T3, Raji, and T Jurkat cell lines and primary neural progenitors. RESULTS AND DISCUSSION:Our results demonstrate that the Ig-? MAR in the context of LV slightly increases transduction efficiency only in Hela, NIH-3T3 and Jurkat cells. In the context of double-copy lentiviral vectors, the Ig-? MAR has no effect or even negatively influences transduction efficiency. In the same way, in the context of non-integrating lentiviral vectors, the Ig-? MAR has no effect or even negatively influences transduction efficiency, except in differentiated primary neural progenitor cells.The ChL MAR in the context of integrating and non-integrating lentiviral vectors shows no effect or a decrease of transgene expression in all tested conditions. CONCLUSIONS:This study demonstrates that MAR sequences not necessarily increase transgene expression and that the effect of these sequences is probably context dependent and/or vector dependent. Thus, this study highlights the importance to consider a MAR sequence in a given context. Moreover, other recent reports pointed out the potential effects of random integration of insulators on the expression level of endogenous genes. Taken together, these results show that the use of an insulator in a vector for gene therapy must be well assessed in the particular therapeutic context that it will be used for, and must be balanced with its potential genotoxic effects.

Dataset Information

Ribosomal DNA integrating rAAV-rDNA vectors allow for stable transgene expression.

Publications

Ribosomal DNA integrating rAAV-rDNA vectors allow for stable transgene expression.

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