Effects of the Mammalian Target of Rapamycin Inhibitor Everolimus on Hepatitis C Virus Replication In Vitro and In Vivo

Background: The influence of immunosuppressants on hepatitis C virus (HCV) re-infection after liver transplantation, particularly mammalian target of rapamycin inhibitors, remains unclear. The aim of our study was to analyze the influence of everolimus (EVR) on HCV replication activity in the context of underlying molecular mechanisms, with focus on the pro-myelocytic leukemia protein (PML).

Methods: HCV viral load was recorded in 40 patients with post-transplant HCV re-infection before and 8 weeks after introduction of EVR. An HCV cell culture replicon system for genotype (GT) 1b, GT2b, and GT3a was used to compare the influence of EVR on HCV replication for the respective genotypes in vitro. Fluorescence-activated cell-sorting analysis was used to test for effects on cell proliferation. PML expression was silenced with the use of small hairpin RNA constructs, and PML expression was quantified by means of quantitative real-time polymerase chain reaction.

Results: In patients with HCV, the viral load of GT1a and GT1b was hardly affected by EVR, whereas the viral load was reduced in patients with GT2a (P ≤ .0001) or GT3 infection (P ≤ .05). In vitro EVR impairs HCV replication activity of GT2a and GT3a up to 60% (P ≤ .0005), whereas in GT1b cells, HCV replication activity is increased by 50% (P ≤ .005). Replicon cell viability was not impaired. HCV replication activity is impaired in the absence of PML, which can be reversed by overexpression of PML isoforms. Furthermore, in the absence of PML, the effect of EVR on HCV replication activity is nearly abrogated.

Conclusions: The mammalian target of rapamycin inhibitor EVR influences HCV replication via PML. The herein presented results suggest a genotype-dependent benefit for an EVR-based immunosuppressive regimen in patients with GT2a or GT3 re-infection after liver transplantation.