RESUMO
There is growing interest in the use of oncolytic virus as a tool in cancer gene therapy. However, construction of oncolytic adenovirus (Ad) is not an easy task due to lack of convenient, robust methods. A three-plasmid system was introduced for construction of armed oncolytic Ad. Besides the pShuttle-CMV and pAdEasy-1, a third plasmid (pTE-ME1), harboring the E1 region of Ad5, was generated and included in this system. In pTE-ME1, the promoter of E1A was deleted and replaced with a multiple-cloning site (MCS). A therapeutic gene and tissue-specific promoter (TSP) could be inserted routinely into the MCS of pShuttle-CMV and pTE-ME1, respectively. The modified E1 region could then be excised from pTE-ME1 and integrated into the therapeutic gene-containing pShuttle-CMV to form the final shuttle plasmid. This shuttle plasmid was recombined with pAdEasy-1 in Escherichia coli strain BJ5183 to generate Ad plasmid. Finally, the oncolytic Ad could be rescued in Ad plasmid-transfected packaging cells. The GFP gene and the promoter of telomerase reverse transcriptase (TERTp) were chosen as the transgene and TSP, respectively, to test this system. Two oncolytic Ads, Ad-GFP-TPE and Ad-GFP-D19K, were generated successfully. Their oncolytic and replicating abilities were investigated in TERT-positive tumor cells. The results suggest that the three-plasmid system was practicable and could be used to construct other transcriptionally regulated oncolytic Ads carrying a therapeutic gene.
Assuntos
Adenovírus Humanos , Vetores Genéticos , Vírus Oncolíticos , Plasmídeos , Replicação Viral , Proteínas E1B de Adenovirus/genética , Adenovírus Humanos/genética , Adenovírus Humanos/fisiologia , Linhagem Celular , Linhagem Celular Tumoral , Fibroblastos/virologia , Proteínas de Fluorescência Verde/genética , Células HeLa , Humanos , Rim/citologia , Rim/virologia , Vírus Oncolíticos/genética , Vírus Oncolíticos/fisiologia , Especificidade de Órgãos , Plasmídeos/genética , Regiões Promotoras Genéticas , Telomerase/genética , Transfecção , TransgenesRESUMO
Adenovirus type 40 and 41 (Ad40, Ad41), which belong to human adenovirus subgroup F, are called fastidious adenoviruses due to their property of poor growth in cultured cell lines in vitro The effect of expression of exogenous E1B55K in Hep2 on Ad41 replication in this cell line was investigated. E1B55K gene was amplified by PCR with DNA extracted from Ad41-positive feces supernatant as template. Eukaryotic expression plasmid (pcDNA3) carrying E1B55K was constructed, purified, and transferred into Hep2 cell. Expression of E1B55K in G418-resistant clones was assayed by RT-PCR, and one clone named as Hep2-E1B4#4 could produce more Ad41 progenies when compared with other clones by the method of inducing complete cytopathic effect (CPE) in 293 cells. Infection of equivalent Ad41 caused more significant cytopathic effect (CPE) in Hep2-E1B#4 than that in the control cells of Hep2 or Hep2-DNA3, also suggesting enhanced viral replication in Hep2-E1B#4. The titer of Ad41 was further determined by method of immunocytochemical staining, and semi-quantity PCR was employed to compare the copy number of Ad41 genome DNA. The results showed that the yield of Ad41 in Hep2-E1B#4 was more than 9 times of that in control cells when equal amount of seed viruses were incubated, and the copy number of Ad41 genome increased 4 times in the raw extract from the infected Hep2-E1B#4 when compared with that from control cells. In conclusion, E1B55K gene transfer improved the ability of Hep2 in packaging Ad41, and the Hep2-E1B#4 cell line, which expressed E1B55K constitutively, would be helpful in isolation, cultivation and amplification of Ad41.
