Combined HSV-1 recombinant and amplicon piggyback vectors: replication-competent and defective forms, and therapeutic efficacy for experimental gliomas
✍ Scribed by Peter A. Pechan; Ulrich Herrlinger; Manish Aghi; Andreas Jacobs; Xandra O. Breakefield
- Book ID
- 101300212
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 253 KB
- Volume
- 1
- Category
- Article
- ISSN
- 1099-498X
No coin nor oath required. For personal study only.
✦ Synopsis
Background The versatility of HSV-1 vectors includes large transgene capacity, selective replication of mutants in dividing cells, and availability of recombinant virus (RV) and plasmid-derived (amplicon) vectors, which can be propagated in a co-dependent, `piggyback', manner.
Methods A replication-defective piggyback vector system was generated in which the amplicon carries either of two genes essential for virus replication, IE2 (ICP27) or IE3 (ICP4), as well as lacZ; the RV is deleted in both these genes, and vector stocks are propagated in cells transfected with one of the complementary genes. In the replication-competent system, the amplicon carries the IE2 and lacZ; the RV had a large deletion in the IE2; and stocks are propagated in untransfected cells. Titers over successive passages, recombination between amplicon and RV, and the structural integrity of vector genomes were evaluated. The replication-competent system was tested for therapeutic ef®cacy in subcutaneous 9L gliosarcoma tumors in nude mice with activation of ganciclovir via the viral HSV-thymidine kinase gene.
Results Both systems generated high titer amplicon vectors (about 10 7 tu/ml) and amplicon:RV ratios (0.6±3.0). No replication-competent RV was generated in either system. The replication-defective system showed low toxicity and increased packaging ef®ciency of amplicon vectors, as compared to single mutant RV helper virus. The replication-competent system allowed co-propagation of amplicon and RV; injection into tumors followed by ganciclovir treatment inhibited tumor growth without systemic toxicity.
Conclusion New replication-defective and replication-competent piggyback HSV, vector systems allow gene delivery via amplicon vectors with reduced toxicity and co-propagation of both RV and amplicon vectors in target cells, with effective tumor therapy via focal virus replication and pro-drug activation.