Helper-dependent adenovirus vectors (HDVs) are safe and efficient tools for gene transfer with high cloning capacity. However, the\nmultiple amplification steps needed to produce HDVs hamper a robust production process and in turn the availability of high-quality\nvectors. To understand the factors behind the low productivity, we analyzed the progression of HDV life cycle. Canine adenovirus\n(Ad) type 2 vectors, holding attractive features to overcome immunogenic concerns and treat neuro biological disorders, were the\nfocus of this work. When compared with E1-deleted (?E1) vectors, we found a faster helper genome replication during HDV\nproduction. This was consistent with an up regulation of the Ad polymerase and pre-terminal protein and led to higher and earlier\nexpression of structural proteins. Although genome packaging occurred similarly to ?E1 vectors, more immature capsids were\nobtained during HDV production, which led to a ~ 4-fold increase in physical-to-infectious particles ratio. The higher viral protein\ncontent in HDV-producing cells was also consistent with an increased activation of autophagy and cell death, in which earlier cell\ndeath compromised volumetric productivity. The increased empty capsids and earlier cell death found in HDV production may\npartially contribute to the lower vector in fectivity. However, an HDV-specific factor responsible for a defective maturation process\nshould be also involved to fully explain the low infectious titers. This study showed how a deregulated Ad cycle progression affected\ncell line homeostasis and HDV propagation, highlighting the impact of vector genome design on virusââ?¬â??cell interaction.
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