Normothermically perfused livers as a model for profiling lentiviral pharmacokinetics and transduction

Lentiviral-based vectors (LV) have been of special interest due to their ability to transduce non-dividing cells and to deliver large genetic payloads for long-term stable expression in target cells. For certain inherited diseases affecting the liver, LV gene therapy may offer a curative approach. However, the utility of LV for production of physiologically relevant levels of encoded protein is dependent on its stability in blood, evasion of Kupffer cell clearance, transduction of hepatocytes and integration into the host genome. At present preclinical models of appropriate scale and physiology to allow assessment of all these factors are lacking, contributing towards difficulty in translation into humans.

Normothermic machine perfusion can maintain physiological function of whole human-sized livers ex vivo for prolonged durations. It has already enabled prediction of human pharmacokinetics of oncology agents. Here we report the use of perfused porcine livers as a model for profiling LV pharmacokinetics and transduction. Livers were perfused for >36 hours with evidence of biochemical homeostasis. An HIV-based LV encoding GFP driven by a liver specific promoter was delivered via the portal vein and distributed into liver tissue within 4 hours. By 36 hours there was a 2-3x increase in vector copy number (VCN) which was sustained at 39 hours. Spatial distribution of vector integration was homogenous across liver tissue with mean 0.024 VCN/cell. 

Furthermore, the enhancement of liver transduction offered by the application of externally focussed ultrasound was also assessed. These proof-of-concept studies are now being developed to test outputs using perfused human livers.