Improvements in HSV-1- derived amplicon vectors for gene transfer

MATIAS ELISEO MELENDEZ; ALEJANDRA INES AGUIRRE; MARIA VERONICA BAEZ; CARLOS BUENO; ANNA SALVETTI; DIANA ALICIA JERUSALINSKY; ALBERTO LUIS EPSTEIN

Advances in Viral Genomes Research

Nova Science Publisher

Año: 2013; p. 1 - 50

Viral vectors engineered to carry transgenic sequences can be delivered into discrete tissues oranatomical structures to express specific transgenes into the transduced cells. Therefore, they are useful tools to produce specific, transient and localized knockout, knockdown, ectopic expression or overexpression of a gene, leading to the possibility of analyzing both in vitro and in vivo molecular basis of relevant functions. Replication-incompetent helper-dependent amplicon vectors, derived from herpes simplex virus type-1 (HSV-1) are devoid of viral genes. Thus, these vectors have great advantages as tools for in vitro and in vivo gene transfer and, in particular (i) minimal toxicity or induction of adaptive immune responses, and (ii) large transgene capacity, being able to carry up to 150 kbp of foreign DNA. In addition, these vectors have (iii) widespread cellular tropism: amplicons can experimentally infect several cell types, either quiescent or not, though naturally HSV-1 infects mainly neurons and epithelial cells, and (iv) absence of insertional mutagenesis, since the viral genome does not integrate into the host cell genome. These vectors have been used both on basic and applied research, and they have revealed as most suitable tools to study complex functions involving the nervous system, such as anxiety, sexual behavior, learning and memory. In addition, amplicon vectors are being used for the development of new experimental gene therapy approaches, both for inherited and acquired diseases affecting the nervous system, including neurodegenerative diseases. Although several technological improvements have been achieved in the last decade, some difficulties regarding these appealing vectors remain still unresolved, such as the inability to generate large amounts of high-titer fully helper-free vectors and the fact that expression from the transgenic sequence delivered by the vectors is generally unstable, often leading to a complete silencing of expression after a few weeks. To overcome these obstacles and to improve these vectors, we have recently modified (a) the amplicon genome, in order to fully delete bacterial sequences and (b) developed novel complementing cell lines, in order to improve helper-free vector production and to render amplicon stocks compatible with clinical trials. In this review article we briefly review data supporting the potential of HSV-1-based amplicon vector model for gene delivery in primary cultures of neural cells and into the brain of living animals.