HSV Recombinant Vectors

The HSV-1 amphcon is a uniquely designed eukaryotic expression plasmid that harbors two non-protein encoding viras-derived elements an HSV origin of DNA rephcation (OriS) 

Amplicon Vector Titer = 10 - lO TU/ml Wild-type Reversion Frequency 1 in 10  

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The development of vectors based on HSV-1 has produced two different viral vector systems recombinant HSV-1 vectors and HSV-1 amplicons. 

The major problem of recombinant HSV-1 vectors is their cytopathic effect and the induction of an immune response by viral gene expression. The development of amplicon vectors and a helper vims-free packaging system has overcome this problem to a great extent (123-125). However, additional deletion of nonessential genes from the bac packaging system may be necessary to further prevent the cytotoxicity of this vector system. 

Viral genome can be inserted with a large DNA sequence by homologous recombination, and the recombinant virus, which is defective in replication, can be plaque purified by using transcomplementing cells. However, this viral vector has several disadvantages it is difficult to obtain preparations that are completely defective in replication, the modified vector generates immune response and antibodies specific for HSV-1 are present. 

Epstein AL, Marconi P, Argnani R, Manservigi R. 2005. HSV-1 derived recombinant and amplicon vectors for gene transfer and gene therapy. Curr Gene Ther. 5 445-448. 

Booth MJ, Mistry A, Li X, Thrasher A, Coffin RS. Transfection-free and scalable recombinant AAV vector production using HSV/AAV hybrids. Gene Ther 2004 11 829-837. 

Fig. I. Schematic representation of homologous recombination with a replacement-type vector employing positive-negative selection. Exons are shaded and intronic regions are represented by open boxes. Vector sequences are denoted by a wavy line. HSV-tt, herpes simplex virus thymidine kinase expression vector P-Neo. promoter-neomyocin expression vector.

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