Efficient mobilization of E1-deleted adenovirus type 5 vectors by wild-type adenoviruses of other serotypes

Abstract

Mobilization of replication-deficient adenovirus vectors can lead to spread and shedding of the vector. Here we show that in cultured HepG2 cells wild-type (wt) adenoviruses of subgroup A (Ad12), B (Ad7, 11 and 16), C (Ad1, 2 and 5) and E (Ad4) can efficiently mobilize Ad5CMVluc, a ∆E1∆E3-Ad5 vector carrying the firefly luciferase gene as reporter. In addition, we show that Ad5CMVluc can be propagated on Ad12E1-transformed human embryonic retinoblasts. This provides evidence that expression of the E1 region of Ad12 is sufficient for mobilizing ∆E1-Ad5-derived vectors. Thus, in therapeutic applications of replication-defective Ad vectors any active Ad infection is of potential concern, independent of the serotype involved. To prevent vector mobilization by wt Ads, new vectors should be developed in which essential functions such as the initiation of DNA replication and genome packaging are restricted.Adenoviruses (Ad) are a diverse family of viruses. In humans at least 51 different serotypes have been described, which have been divided into six subgroups (formerly species) based on haemagglutination properties with red blood cells, oncogenic potential and GjC content of their DNA (Horwitz, 1995). Replication-defective derivatives of serotypes 5 (Ad5) and 2 (Ad2), generated by deletion of sequences of the viral E1, E2 and E4 regions, have been widely used as gene-transfer vehicles in experimental gene therapy (Benihoud et al., 1999). Therapeutic application of recombinant Ad vectors is complicated by the presence of replication-competent adenoviruses (RCA). The presence of RCA in the vector batches may lead to inflammation and tissue damage in the recipient (Fallaux et al., 1999 ;Hermens & Verhaagen, 1997). In addition, RCA can mobilize the Ad vector (Imler et al., 1995), and this could lead Author for correspondence : Rob Hoeben.Fax j31 71 527 6284. e-mail R.C.Hoeben!lumc.nl increased vector shedding. The development and implementation of improved helper cells (Fallaux et al., 1998) and vectors (Hehir et al., 1996), as well as stringent quality-control measures (Roitsch et al., 2001 ;Fallaux et al., 1999), can virtually eliminate the problem of RCA in the vector batches.However, this does not solve the mobilization problem completely. It is conceivable that after receiving gene therapy, patients develop a viraemia with a wild-type (wt) Ad. Indeed, administration of wt Ad5 into lungs of cotton rats previously exposed to replication-defective Ad5 vectors led to mobilization of the vector (Imler et al., 1995). The risk of a mobilization by wt Ad of the same serotype is limited, as most patients will develop immunity against the vector serotype ( Harvey et al., 1999). It is not known, however, whether the vectors can be mobilized by other serotypes, viz. serotypes different from the one from which the vector had been derived. To study this possibility, we determined whether wt Ads of subgroups A, B, C and E could mobilize the vector Ad5CMVluc, a ∆E1∆E3-Ad5 vector carrying the firefly luciferase gene as a reporter.Fi...

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Relaxed template specificity in fowl adenovirus 1 DNA replication initiation

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Transfer of the Full-Length Dystrophin-Coding Sequence into Muscle Cells by a Dual High-Capacity Hybrid Viral Vector with Site-Specific Integration Ability

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