Abstract

Our laboratory is focused on the translation of gene therapies to treat metabolic liver disease in the paediatric setting using recombinant adeno-associated virus (AAV), which is emerging as an effective in vivo vector platform for new modalities of disease treatments. The laboratory research program encompasses a bench-to-bedside approach and includes “viral palaeontology” in Australian marsupials to discover new vector capsids as well as the design and testing of vectors in preclinical models. Recombinant AAV is based on a human parvovirus from the Dependoviridae family which has long been an appealing virus for vectorisation due to (i) its relatively simple structure with only two known genes encoded on the sense strand of the genome, (ii) requirement for helper virus to complete virus cycle and (iii) non-pathogenic status. However, this latter feature has been recently called into question by a study implicating AAV insertional mutagenesis in hepatocellular carcinoma (Nault et al. Nature Genetics 2015). Conclusions drawn from the report have caused contention with one point of concern the relatively small size of the integrated AAV genome fragment (201-1975 bp) and how this might be responsible for driving oncogenesis. In the course of our studies, we have discovered a novel promoter/enhancer element in the anti-sense genome of the virus, which is common to 10/11 AAV genome fragments implicated in the HCC study. The element is compact, operates in a cell restricted manner largely in cells of hepatic origin and appears to be conserved across phylogenetically-related AAV . Our findings provide an underlying mechanism to account for the dysregulation of gene expression at the site of AAV integration in human HCC and indicate potential biological function for the anti-sense genome.