HSV-1-derived amplicon vectors: recent technological improvements and remaining difficulties - a review

Abstract

Amplicons are defective and non-integrative vectors derived from herpes simplex virus type 1. As the vector genome carries no virus genes, amplicons are both non-toxic for the infected cells and non-pathogenic for the inoculated organisms. In addition, the large transgenic capacity of amplicons, which allow delivery of up to 150 Kbp of foreign DNA, makes these vectors one of the most powerful, interesting and versatile gene delivery platforms. We present here recent technological developments that have significantly improved and extended the use of amplicons, both in cultured cells and in living organisms. In addition, this review also discusses the many difficulties still pending to be solved, in order to achieve stable and physiologically regulated transgene expression.

Transfection Techniques for Neuronal Cells: Table 1.

“…In addition, some viruses [adeno-associated viruses (AAVs), modified herpes simplex viruses (HSVs)] require the coinfection of packaging cells with a wild-type helper virus to produce infectious virions. This results in a contamination of the supernatant (from which the infectious virions are purified) with helper viruses, which often cannot be fully eliminated during the preparation of the viral stock (Epstein, 2009) and can have cytotoxic effects (White et al, 2002).…”

“…Recombinant HSV-1 and amplicon (plasmid)-based vectors have been developed (Epstein, 2009). Amplicon vectors carry almost no genes of the HSV-1 genome (and are thus nontoxic), but have a transgene capacity of up to 150 kb.…”

“…Amplicon vectors carry almost no genes of the HSV-1 genome (and are thus nontoxic), but have a transgene capacity of up to 150 kb. This allows for the insertion of multiple copies of a transgene or of large genomic regions, including regulatory elements (Epstein, 2009). However, they require a wild-type helper virus (HSV-1) for replication and packaging.…”

“…However, they require a wild-type helper virus (HSV-1) for replication and packaging. A major drawback is the difficulty of producing high-titer stocks of vector particles free of helper virus (Epstein, 2009), which can lead to cytotoxic effects and/or immune responses. The recent development of helper virus-free systems is therefore promising (Fraefel, 2002).…”

HSV Recombinant Vectors for Gene Therapy

“…When amplicons are transfected into mammalian cells with HSV helper functions, they are replicated, form head-to-tail linked concatamers and are then packaged into viral particles. There are two major methods currently used for producing amplicon particles, one based on infection with defective helper HSVs and the other based on transfection of HSV-1 genes, such as a set of pac -deleted overlapping cosmids or a pac-deleted and ICP27-deleted BAC-HSV-1 [17]. The main advantages of these vectors are that they can accommodate large fragments of foreign DNA (theoretically up to 152 kb), including multiple copies of the transgene (up to 15), and are non-toxic.…”