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Combined HSV‐1 recombinant and amplicon piggyback vectors: replication‐competent and defective forms, and therapeutic efficacy for experimental gliomas
Author(s) -
Pechan Peter A.,
Herrlinger Ulrich,
Aghi Manish,
Jacobs Andreas,
Breakefield Xandra O.
Publication year - 1999
Publication title -
the journal of gene medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.689
H-Index - 91
eISSN - 1521-2254
pISSN - 1099-498X
DOI - 10.1002/(sici)1521-2254(199905/06)1:3<176::aid-jgm35>3.0.co;2-t
Subject(s) - amplicon , biology , virology , suicide gene , vector (molecular biology) , viral replication , viral vector , helper virus , gene , microbiology and biotechnology , genetic enhancement , recombinant dna , virus , polymerase chain reaction , genetics
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 efficacy 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 efficiency 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. Copyright © 1999 John Wiley & Sons, Ltd.