Identification of critical infection parameters to control helper-dependent adenoviral vector production.

Helper-dependent adenoviral vectors (HDVs) are the most promising adenoviral vectors for gene therapy treatments as well as vaccination strategies. However, the lack of a robust and efficient strategy to produce the HDV at high titers constitutes a major obstacle hindering the use of this promising technology at the clinical level. The HDV production requires a double infection of a recombinase-expressing HEK293 cell line with the HDV and a helper virus (HV). To limit the contamination of viral HDV lots by HV, encapsidation of HV is prevented by the recombinase action. A real-time quantitative PCR assay was developed to accurately characterize the contamination of the final product by HV. Infection strategies to enhance the HDV yield and reduce the contamination by HV were investigated. The multiplicity of infection (MOI) was identified as a critical parameter to simultaneously improve the HDV yield and reduce the contamination by HV. HDV-to-HV MOI ratio dictated the HDV yield whereas the HV accumulation was controlled by the MOI of HV. Delaying infection with the HV did not improve the HDV yield.

From the first to the third generation adenoviral vector: what parameters are governing the production yield?

Human adenoviral viral vector serotype 5 (AdV) is presently the primary viral vector used in gene therapy trials. Advancements in AdV process development directly contribute to the clinical application and commercialization of the AdV gene delivery technology. Notably, the development of AdV production in suspension culture has driven the increase in AdV volumetric and specific productivity, therefore providing large quantities of AdV required for clinical studies. This review focuses on detailing the viral, cell and cell culture parameters governing the productivity of the three generations of AdV vectors.

An efficient and scalable process for helper-dependent adenoviral vector production using polyethylenimine-adenofection.

Safety requirements for adenoviral gene therapy protocols have led to the development of the third generation of vectors commonly called helper-dependent adenoviral vectors (HDVs). HDVs have demonstrated a high therapeutic potential; however, the poor efficiency and reliability of the actual production process hampers further large-scale clinical evaluation of this new vector. The current HDV production methods involve a preliminary rescue step through transfection of adherent cell cultures by an HDV plasmid followed by a helper adenovirus (HV) infection. Amplification by serial co-infection of complementary cells allows an increase in the HDV titer. Using a HEK293 FLP/frt cell system in suspension culture, an alternative protocol to the current transfection/infection procedure was evaluated. In this work, the adenofection uses the HDV plasmid linked to the HV with the help of polyethylenimine (PEI) and has shown to outperform standard protocols by producing higher HDV yield. The influence of complex composition on the HDV production was examined by a statistical design. The optimized adenofection and amplification conditions were successively performed to generate HDV at the 3 L bioreactor scale. Following only two serial co-infection passages, up to 1.44 x 10(8) HDV infectious units/mL of culture were generated, which corresponded to 26% of the total particles produced. This production strategy, realized in cell suspension culture, reduced process duration and therefore the probability of vector recombination by introducing a cost-effective transfection protocol, ensuring production of high-quality vector stock.