Toll-like receptor-activated primary human hepatocytes produce inflammatory cytokines and different types of interferon, resulting in HCV suppression in vitro

Aims: The function of the hepatic innate immune system and its role in the defence against Hepatitis C Virus infection is not well understood. Recent publications suggested that type-III interferons (IFN; Interleukin 28A, –28B and –29) play a crucial role in the host response against HCV. Aim of this study was to investigate the Toll-like receptor (TLR) signaling in primary human hepatocytes and the capacity of these cells to produce type-III IFNs and their ability to control HCV replication. Methods: Human liver samples were obtained after tumor resection (n=16) or liver transplantation (n=14). Human hepatocytes (n=30) were isolated after perfusion and digestion of the liver. Cells were stimulated with TLR1–9 ligands for 6–24h, expression of Tumor necrosis factor α (TNF-α), Interleukin 6 (IL–6), IL–10, IFN-α, -β, -γ and –λ were determined by qRT-PCR and ELISA. Gene expression of interferon sensitive genes (ISGs) was determined by qRT-PCR. Results: In human hepatocytes stimulation with TLR1–9 ligands, except TLR9, led to cell-type specific induction of pro-inflammatory (TNF-α, IL–6) and anti-inflammatory cytokines (IL–10). In contrast, expression of type-I, -II and –III interferons (IFN-α, -β, -γ, IL–28A, IL–28B, IL–29) could only be induced after TLR3 stimulation, resulting in enhanced expression of ISGs (ISG15, IFI-T1, RSAD2, MXA). Therefore, HCV replication was only suppressed after co-culture of supernatants from TLR3-activated hepatocytes with a subgenomic HCV replicon. The different underlying diseases, the type of surgery, fibrosis stage as well as liver function tests (ALT, AST, GGT, AP) did not correlate with TLR signaling and antiviral activity in these cells. Conclusion: Primary isolated human hepatocytes respond to TLR ligands by production of pro-inflammatory (TNF-α and IL6) anti-inflammartory (IL–10) cytokines as well as type-I, -II and –III IFN. This results in induction of antiviral ISGs and subsequent suppression of HCV replication i n vitro.

Interferon - Toll-like receptor - human hepatocytes