IMPROVED METHOD FOR PRODUCING NON-PATHOGENIC HELPER VIRUS-FREE PREPARATIONS OF HERPES VIRUS AMPLICON VECTORS, THE HELPER VIRUS amp; THE CELLS USED IN THIS METHOD, THE CORRESPONDING GENETIC TOOLS, AS WELL AS THE APPLICATIONS OF THESE NON-PATHOGENIC AMPLICONS VECTORS

摘要

A defective Cre-loxP based helper virus (HSV-1 LaLDeltaJ), which genome is of reduced size and is free of the genes encoding ICP4 and ICP34.5 proteins from the helper genome, in addition to the native "a" signals. HSV-1 LaLDeltaJ carries a single floxed "a" signal in gC locus. To produce HSV-1 LaLDeltaJ and to prepare the amplicon vectors, two novel cell lines expressing the essential ICP4 protein, either alone or in combination to Cre recombinase, are also disclosed. These cell lines complement ICP4 while minimizing the probability of generating replication-competent particles. The novel helper system enables production of large amounts of high-titer amplicon vectors. Residual helper particles generated do not exceed 0.5% of the viral population and can grow only in cells expressing ICP4. Amplicon vectors produced with this method showed no cytotoxicity for infected cells.