Clinical translation of adeno-associated virus (AAV) and recombinant AAV (rAAV)-mediated gene therapy has been held back by a vector production bottleneck. AAVs are non-enveloped viruses with a 4.7Kb wild type genome flanked by inverted terminal repeats (ITRs). AAV production into icosahedral virions relies on two genes, rep and cap, which provide the proteins necessary for replication and encapsidation of the viral genome, in addition to adeno-helper proteins usually provided by an external source.
At present, laboratory scale production of rAAV uses DNA transfection to introduce the required genetic elements in to human embryonic kidney HEK293 cells. However, transfection methods are not appropriate for large-scale production.
The present invention provides a hybrid vector system comprising a phagemid/AAV (PAAV) particle. The novel genome construct is a phagemid, in this case a hybrid of a phage-derived genome and rAAV transgenes. Two origins of replication are present, one phage and one bacterial. This hybrid differentiates from conventional phagemids in that viral transgenes, rather than generic non-viral components, are incorporated into the phagemid under the influence of the bacterial promotor.
This novel hybrid contains no structural bacteriophage genes, which comprise over 50% of a conventional phage genome. Thus, this phagemid particle is dramatically smaller in size than previously developed hybrid constructs. This smaller genome allows for increased efficiency of vector production, flexibility of the vector system and increased efficacy in gene transduction.