Replication-competent adenovirus

Heise CC, Williams A, Olesch J, et al. Efficacy of a replication-competent adenovirus (ONYX-015) following intratumoral injection intratumoral spread and distribution effects. Cancer Gene Ther 1999 6 499-504. 

D. Nafziger, J. Pegg, D. Paielli, S. Brown, K. Barton, M. Lu, E. Aguilar-Cordova, J.H. Kim, Phase I study of replication-competent adenovirus-mediated double suicide gene therapy for the treatment of locally recurrent prostate cancer. Cancer Res. 62 (2002) 4968-4976. 

Yu DC, Sakamoto GT, Henderson DR. Identification of the transcriptional regulatory sequences of human kallikrein 2 and their use in the construction of calydon virus 764, an attenuated replication competent adenovirus for prostate cancer therapy. Cancer Res 1999 59 1498-1504. 

R. Rodriguez, E. R. Schuur, H. Y. Lim, G. A. Henderson, J. W. Simons, and D. R. Henderson, Prostate attenuated replication competent adenovirus (ARCA) CN706 a selective cytotoxic for prostate-specific antigen-positive prostate cancer cells, Cancer Res. 57 2559 (1997). 

Fallaux FJ, Bout A, van der Wollenberg DJ, Hehir KM, Keegan J, Auger C, Cramer SJ, van Ormondt H, van der Eb AJ, Valerio D, Hoeben RC (1998), New helper cells and matched early region 1-deleted adenovirus vectors prevent generation of replication-competent adenoviruses, Hum. Gene Ther. 9 1909-1917. 

Subramanian, T. and G. Chinnadurai. 2006. Temperature-sensitive replication-competent adenovirus shRNA vectors to study cellular genes in virus-induced apoptosis. Meth. Mol. Med. 130, 125-34. 

Numerous transcriptionally targeted replication-competent adenoviruses and herpes viruses have been shown to be highly specific (up to 10,000-fold relative to nontarget cells) in cell culture experiments. In addition, animal models have demonstrated their safety and efficacy. It thus appears that the transcriptional targeting of viral replication holds some promise as a strategy for cancer gene therapy. 

A purified Ad5EGF-4 virus seed was propagated through three consecutive rounds of plaque purification. A final plaque was then expanded and purified by anion-exchange chromatography, sterilized by filtration and stored at -70°C 10°C. This virus stock was checked for sterility and absence of measurable replication competent adenovirus (RCA). A MVB was then created by one additional cycle of propagation in serum-free suspension culture of HEK 293 cells, and this virus was purified, aliquoted, and frozen. The MVB was tested and confirmed to be free of RCA as well as adventitious agents. The MVB was stored at-70°C 10°C. 

Assessment of the immimogenic consequences of gene delivery should also be possible in the chosen species this is particularly important for the evaluation of viral vectors. There has been much discussion on the value of using a permissive host to assess potential human risk from these vectors. The natural route of exposure - i.e. respiratory for adenoviruses - traditionally used to assess permissivity, seems unnecessary to assess the safety of gene therapy products, particularly with the core study approach discussed above. Systemically-administered replication-competent adenovirus will infect (i.e. gain entry into the cell) and be pathogenic in numerous tissues (Duncan et al., 1978). Gene expression and viral replication depend on the species, route of exposure, and individual tissue susceptibility (Torres et al., 1996 Bett et al., 1962). Thus i.v. administration of viral vectors to mammalian test species should permit the evaluation of potential toxicity of widely-distributed vectors. 

The presence of replication- competent virus in the vector preparation is problematic, since it could be associated with increased toxicity and may lacilitate the spread of the recombinant in vivo (18-20). Replication-competent adenovirus occurs by either cross contamination of the initial plaque with replication-competent vims from an adj acent plaque or reversion of the E1 deletion during the propagation of the recombinant by homologous recombination between sequences in the vector flanking the El deletion and the transfected El sequences in 293 cells. 

Lochmuller H, Jani A, Huard J, et al. Emergence of early region 1-containing replication-competent adenovirus in stocks of replication-defective adenovirus recombinants (delta El+delta E3) during multiple passages in 293 cells. Hum Gene Ther 1994 5 1485-1491. 

KuriharaT, Brough DE, Kovesdi I, Kufe DW. Selectivity ofa replication-competent adenovirus for human breast carcinoma cells expressing the MUCl antigen. J Clin Invest 2000 106(6) 763-771. 

Doronin K, Kuppuswamy M, Toth K, Tollefson AE, Krajcsi P, Krougliak V, Wold WS. Tissue-specific, tumor-selective, replication-competent adenovirus vector for cancer gene therapy. J Virol 2001 75(7) 3314-3324. 

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