Gene delivery from the E3 region of replicating human adenovirus: evaluation of the E3B region

Comparison of the E3 and L3 regions for arming oncolytic adenoviruses to achieve a high level of tumor-specific transgene expression

“…The cells were infected in the absence or presence of the DNA replication inhibitor AraC, which is used to demonstrate that transgene expression is dependent on DNA replication of the virus. 18 When cells were infected with the control Ad-GMCSF virus, the amount of GM-CSF in the supernatant increased steadily with time, reaching a maximum of 188 ng ml À1 at 72 h.p.i. As expected, the kinetics of GM-CSF expression from Ad-GMCSF were identical with or without AraC because the expression from the constitutive CMV promoter is not dependent on Transgene expression from E3 and L3 regions of Ad5 M Robinson et al DNA replication.…”

“…The E3 region was chosen as an insertion site in two vectors on the basis of previous studies demonstrating that E3 genes are not essential for viral replication and that transgenes can be successfully inserted into this region, without major impairment of viral function. 18,20,22,32 In the Ad-GM-gp19K vector, the hGM-CSF cDNA was inserted into the E3 gp19K region as previously described for the vector Dgp19B. 22 The hGM-CSF cDNA was inserted in place of the E3 14.7K gene in the second E3-based vector, Ad-GM-14.7.…”

“…17 Several strategies for arming the vectors and for controlling transgene expression have been used, with the most recent attempts utilizing adenoviral promoters and transcriptional control elements to regulate the expression of inserted transgenes. 15,[18][19][20][21] These studies showed that linking transgene expression to adenoviral genes that are expressed late in infection, that is, after DNA replication, restricted transgene expression to tumor cells. 15,18 This tumor-specific transgene expression improves the safety of the vector.…”

“…15,[18][19][20][21] These studies showed that linking transgene expression to adenoviral genes that are expressed late in infection, that is, after DNA replication, restricted transgene expression to tumor cells. 15,18 This tumor-specific transgene expression improves the safety of the vector. Several insertion sites, such as the E3A region 11,18,22 and E3B region, 15,18 were identified on the basis of detailed knowledge of transcription in adenoviruses.…”

“…15,18 This tumor-specific transgene expression improves the safety of the vector. Several insertion sites, such as the E3A region 11,18,22 and E3B region, 15,18 were identified on the basis of detailed knowledge of transcription in adenoviruses. More recently, a novel transposonbased mechanism has been described that identified other potential insertion sites, even though the exact transcriptional regions had not been previously identified.…”