Genetic manipulation using hepatocyte-targeting adeno-associated viral vectors has minimal off-target effects.

Mice are a widely used pre-clinical model system in large part due to their potential for genetic manipulation. The ability to manipulate gene expression in specific cells under temporal control is a powerful experimental tool. The liver is central to metabolic homeostasis and a site of many diseases, making the targeting of hepatocytes attractive. Adeno-Associated Virus 8 (AAV8) vectors are valuable instruments for the manipulation of hepatocellular gene expression. However, their off-target effects in mice have not been thoroughly explored. Here, we sought to identify the short-term off-target effects of AAV8 administration in mice. To do this, we injected C57BL/6J Wild-Type mice with either recombinant AAV8 vectors expressing Cre recombinase or empty AAV8 vectors and characterised the changes in general health and in liver physiology, histology and transcriptomics compared to uninjected controls over 1 week. We observed an acute and transient reduction in homeostatic liver proliferation together with induction of the DNA damage marker {gamma}H2AX following AAV8 administration. The latter was enhanced upon Cre recombinase expression by the vector. Furthermore, we observed transcriptional changes in genes involved in circadian rhythm and response to infection. Notably, there were no additional transcriptomic changes upon expression of Cre recombinase by the AAV8 vector. Overall, there was no evidence of liver injury, dysfunction or leukocyte infiltration following AAV8 infection. These data support the use of AAV8-based Cre recombinase delivery as a specific tool for hepatocellular gene manipulation with minimal effects on murine physiology but highlight the off target effects of these systems. Summary statementThis paper provides a comprehensive characterisation of the short-term effects of administration of Adeno-Associated Virus 8 on murine physiology, liver histology and liver transcriptome.