Large-scale production of recombinant viruses by use of a large culture vessel with active gassing.

Adenovirus and adeno-associated virus (AAV) vectors are increasingly used for gene transduction experiments. However, to produce a sufficient amount of these vectors for in vivo experiments requires large-capacity tissue culture facilities, which may not be practical in limited laboratory space. We describe here a large-scale method to produce adenovirus and AAV vectors with an active gassing system that uses large culture vessels to process labor- and cost-effective infection or transfection in a closed system. Development of this system was based on the infection or transfection of 293 cells on a large scale, using a large culture vessel with a surface area of 6320 cm2. A minipump was connected to the gas inlet of the large vessel, which was placed inside the incubator, so that the incubator atmosphere was circulated through the vessel. When active gassing was employed, the productivity of the adenovirus and AAV vectors significantly increased. This vector production system was achieved by improved CO2 and air exchange and maintenance of pH in the culture medium. Viral production with active gassing is particularly promising, as it can be used with existing incubators and the large culture vessel can readily be converted for use with the active gassing system.

A histone deacetylase inhibitor enhances recombinant adeno-associated virus-mediated gene expression in tumor cells.

The transduction of cancer cells using recombinant adeno-associated virus (rAAV) occurs with low efficiency, which limits its utility in cancer gene therapy. We have previously sought to enhance rAAV-mediated transduction of cancer cells by applying DNA-damaging stresses. In this study, we examined the effects of the histone deacetylase inhibitor FR901228 on tumor transduction mediated by rAAV types 2 and 5. FR901228 treatment significantly improved the expression of the transgene in four cancer cell lines. The cell surface levels of alpha v integrin, FGF-R1, and PDGF-R were modestly enhanced by the presence of FR901228. These results suggest that the superior transduction induced by the HDAC inhibitor was due to an enhancement of transgene expression rather than increased viral entry. Furthermore, we characterized the association of the acetylated histone H3 in the episomal AAV vector genome by using the chromatin immunoprecipitation assay. The results suggest that the superior transduction may be related to the proposed histone-associated chromatin form of the rAAV concatemer in transduced cells. In the analysis with subcutaneous tumor models, strong enhancement of the transgene expression as well as therapeutic effect was confirmed in vivo. The use of this HDAC inhibitor may enhance the utility of rAAV-mediated transduction strategies for cancer gene therapy.