However, combining the 4-1BBL knockout and 4-1BBL-blocking studiessentially essentially replicated the defective accumulation of both M38 and m139-reactive CD8+ T cells that were seen in the absence of 4-1BB.
Since the adenovirus used in the calibration experiments are replicate-defective and include a GFP expression plasmid, we assume an exponential decay model for LV.
These data suggest that conditionally replicating IN-defective lentiviral-hybrid episomal vectors could prove useful as vehicles for suicide gene therapy, in particular in cells transformed by SV40.
A prototypical example is the adenovirus ONYX-015 and its closely related derivative ONYX-017 (E3 region wild-type), both expected to replicate in p53-defective cells [ 24, 25].
These replicating adenoviruses can be combined with replication-defective Adeno-P450 viruses to facilitate therapeutic delivery of P450, or other therapeutic genes, in tumor cells in vivo [ 20, 24].
The present approach, involving the expression of CYP2B6, its redox partner P450 reductase, and p35 from a single replication-defective viral vector, may also be extended to cancer cell-replicating viral vectors.
This combination of conditionally replicating and non-replicating adenoviruses could be ideal for GDEPT, due to the synergistic effect of combining replicating virus-induced tumor cytolysis with intratumoral activation of chemotherapeutic prodrugs conferred by the replication-defective virus.
However, it remains unclear if a replication-defective HSV-2 virus may recapitulate the magnitude and duration to the immune response that is elicited against a live, replicating virus such as wild-type HSV-2.
In this study, we used a modified 3' RACE protocol to determine whether sub-populations of DENV in patients contained genomes with large internal deletions similar to those found in DI particles in other viral populations [20], [21] and whether viruses with these defective genomes could replicate in the presence of fully functional DENV.
In replicating mammalian cells expressing TVA, the viral vector can stably integrate into the DNA and express the inserted experimental gene at high levels, but the virus is replication-defective since viral RNA and proteins are inefficiently produced [79].
These defective particles can only replicate if they are complemented by a full-length TEV or possibly other defective genomes, and their spread may therefore be limited.
