Oral Presentation ASSCR, AGCTS, ISCT ANZ and Friends Joint Scientific Conference 2019

Nature trumps nurture: Use of naturally liver-tropic adeno-associated viruses as vector platforms for liver-directed human gene therapy (#23)

Claus V Hallwirth 1 , Marti Cabanes-Creus 2 , Erhua Zhu 1 , Grant J Logan 1 , Sophia H Y Liao 2 , Natsuki Sasaki 1 , Erwan Sallard 2 , Adrian Westhaus 2 3 , Samantha L Ginn 1 , Leszek Lisowski 2 4 5 , Ian E Alexander 1 6
  1. Gene Therapy Research Unit, Children's Medical Research Institute, Westmead, NSW, Australia
  2. Translational Vectorology Group, Children's Medical Research Institute, Westmead, NSW, Australia
  3. Molecular and Cellular Immunology, University College London, Great Ormond Street Institute of Child Health, London, United Kingdom
  4. Biological Threats Identification and Countermeasure Centre, Military Institute of Hygiene and Epidemiology, Puławy, Lublin, Poland
  5. Vector and Genome Engineering Facility, Children's Medical Research Institute, Westmead, NSW, Australia
  6. Discipline of Child and Adolescent Health, Sydney Medical School, The University of Sydney, Westmead, NSW, Australia

Despite unequivocal recent successes in AAV-mediated liver-directed gene therapy trials, many liver diseases theoretically amenable to treatment with gene therapy are still beyond the reach of contemporary AAV technology, which is constrained by suboptimal hepatocyte targeting. The aim of this study is therefore to develop AAV vectors with superior hepatotropism. Our previous discovery and functional characterisation of conserved master hepatic transcription factor binding sites in the 3’-untranslated region of the prototypical human AAV isolate, AAV2, signify its intimate association with the human liver. However, vectors utilising the AAV2 capsid in a liver-directed gene therapy trial resulted in unexpectedly low therapeutic efficacy. This was consistent with our subsequent observations of inefficient human hepatocyte transduction in the xenograft FRG mouse model, despite robust targeting of human hepatocyte-derived cell lines. Upon discovering that most primate AAVs evolved to infect the liver, we resolved the paradox of AAV2 human hepatotropism by amplifying AAV capsid sequences directly from human liver samples. Comparison with the prototypical AAV2 capsid revealed functionally validated differences in the heparan sulfate proteoglycan binding domains, thereby attributing inefficient transduction of primary human hepatocytes by the originally culture-isolated AAV2 (henceforth “ciAAV2”) to culture adaptation. The development of AAV vectors using capsids isolated directly from liver samples, and naturally evolved to traffic to the liver and target human hepatocytes, harnesses the power of viral evolution and circumvents cell culture attenuation of hepatotropism. In humanised FRG mice, several of the novel and sero-diverse wildtype liver-isolated capsids vectorised to date already functionally outperform the most human liver-tropic bioengineered AAV capsids – LK03 and AAVS3 – currently in gene therapy clinical trials targeting the human liver, but still fall short of the most human hepatotropic capsids our groups have developed. We are further optimising their performance and manufacturability to develop a set of superior, clinically translatable capsids.

  • Have you presented your abstract at another international meeting?: No