Integrating adenovirus-adeno-associated virus hybrid vectors devoid of all viral genes

Recently, we demonstrated that inverted repeat sequences inserted into first-generation adenovirus (Ad) vector genomes mediate precise genomic rearrangements resulting in vector genomes devoid of all viral genes that are efficiently packaged into functional Ad capsids. As a specific application of this finding, we generated adenovirus-adeno-associated virus (AAV) hybrid vectors, first-generation Ad vectors containing AAV inverted terminal repeat sequences (ITRs) banking a reporter gene cassette inserted into the El region, We hypothesized that the AAV ITRs present within the hybrid vector genome could mediate the formation of rearranged vector genomes (Delta Ad.AAV) and stimulate transgene integration. We demonstrate here that Delta Ad.AAV vectors are efficiently generated as by-products of first-generation adenovirus-AAV vector amplification. Delta Ad.AAV genomes contain only the transgene flanked by AAV ITRs, Ad packaging signals, and Ad ITRs. Delta Ad.AAV vectors can be produced at a high titer and purity, In vitro transduction properties of these deleted hybrid vectors were evaluated in direct comparison with first-generation Ad and recombinant AAV vectors (rAAVs), The Delta Ad.AAV hybrid vector stably transduced cultured cells with efficiencies comparable to rAAV. Since cells transduced with Delta Ad.AAV did not express cytotoxic viral proteins, hybrid viruses could be applied at very high multiplicities of infection to increase transduction rates. Southern analysis and pulsed-field gel electrophoresis suggested that Delta Ad.AAV integrated randomly as head-to-tail tandems into the host cell genome, The presence of two intact AAV ITRs was crucial for the production of hybrid vectors and for transgene integration. Delta Ad.AAV vectors, which are straightforward in their production, represent a promising tool For stable gene transfer in vitro and in vivo.