scAAV5-Cre

The recombinant adeno-associated virus (rAAV) genome controls transgene expression levels, cell type specificity, duration, and other important aspects of AAV therapeutics. As a result, considerable effort has been devoted to optimizing components of the genome, including inverted terminal repeats (ITRs), promoters, and other regulatory elements.

The AAV genome contains symmetrical ITRs at both ends that serve as origins for DNA replication and packaging signals. Single-stranded AAV (ssAAV) requires the host cell DNA polymerase machinery to generate complementary strands for transduction, a major limitation that slows transgene expression. However, the development of self-complementary AAV (scAAV) has circumvented this obstacle. scAAV has a 5- to 140-fold increase in transduction capacity over ssAAV. The increase in efficiency compensates for half of the loss in packaging capacity (2.4 kb for scAAV vs. 4.8 kb for ssAAV). Notably, scAAV enhanced the innate immune response by enhancing activation of TLR9/MyD88 signaling and induced IL-6, TNF-α, and other proinflammatory cytokines in a dose-dependent manner, indicating enhanced immunogenicity associated with scAAV. The TLR9 receptor is essential for recognizing unmethylated CpG motifs, which are highly present in the ITR region.