Summary auto-generated
This study examined whether wild-type adenoviruses of different serotypes can mobilize replication-deficient adenovirus type 5 (Ad5) vectors, which are used in gene therapy. Researchers used HepG2 cells infected with Ad5CMVluc, a E1-deleted Ad5 vector carrying a luciferase reporter gene, and then exposed them to wild-type adenoviruses from subgroups A, B, C, and E. Using a marker-mobilization assay measuring luciferase expression, the authors found that wild-type viruses from all tested serotypes (Ad12, Ad7, Ad11, Ad16, Ad1, Ad2, Ad5, and Ad4) efficiently mobilized the Ad5 vector. DNA replication was confirmed by Southern blot analysis and was sensitive to cytosine arabinoside, indicating active viral replication. Additional experiments using human embryonic retinoblasts transformed with Ad12 E1 genes demonstrated that E1 region expression alone is sufficient for vector mobilization. These findings suggest that any wild-type adenovirus infection during gene therapy poses a mobilization risk, regardless of serotype, and highlight the need for improved vector designs restricting essential viral functions.
Key findings
- Wild-type adenoviruses from multiple serotypes (subgroups A, B, C, and E) efficiently mobilize E1-deleted Ad5 vectors in cultured cells
- E1 region expression from heterologous adenovirus serotypes is sufficient for mobilizing replication-deficient Ad5 vectors, as demonstrated using Ad12 E1-transformed cell lines
- Vector mobilization requires active viral DNA replication, as shown by sensitivity to cytosine arabinoside inhibition
- Any active adenovirus infection during therapeutic applications poses a mobilization risk regardless of the viral serotype involved
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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 ΔE1ΔE3-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 ΔE1-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.