Intrahepatic CD206+ macrophages contribute to inflammation in advanced viral-related liver disease

Abstract

Background & aims: Liver inflammation is key in the progression of chronic viral hepatitis to cirrhosis and hepatocellular carcinoma. The magnitude of viral replication and the specific anti-viral immune responses should govern the degree of inflammation, but a direct correlation is not consistently found in chronic viral hepatitis patients. We aim to better define the mechanisms that contribute to chronic liver inflammation.

Methods: Intrahepatic CD14⁺ myeloid cells from healthy donors (n=19) and patients with viral-related liver cirrhosis (HBV, HBV/HDV or HCV; n=15) were subjected to detailed phenotypic, molecular and functional characterisation.

Results: Unsupervised analysis of multi-parametric data showed that liver disease was associated with the intrahepatic expansion of activated myeloid cells mainly composed of pro-inflammatory CD14⁺HLA-DR^hiCD206⁺ cells, which spontaneously produced TNFα and GM-CSF. These cells only showed heightened pro-inflammatory responses to bacterial TLR agonists and were more refractory to endotoxin-induced tolerance. A liver-specific enrichment of CD14⁺HLA-DR^hiCD206⁺ cells was also detected in a humanised mouse model of liver inflammation. This accumulation was abrogated following oral antibiotic treatment, suggesting a direct involvement of translocated gut-derived microbial products in liver injury.

Conclusions: Viral-related chronic liver inflammation is driven by the interplay between non-endotoxin-tolerant pro-inflammatory CD14⁺HLA-DR^hiCD206⁺ myeloid cells and translocated bacterial products. Deciphering this mechanism paves the way for the development of therapeutic strategies specifically targeting CD206⁺ myeloid cells in viral-related liver disease patients. Lay summary: Viral-related chronic liver disease is driven by intrahepatic pro-inflammatory myeloid cells accumulating in a gut-derived bacterial product-dependent manner. Our findings support the use of oral antibiotics to ameliorate liver inflammation in these patients.

Keywords: Bacterial translocation; Endotoxin tolerance; Liver inflammation; Monocyte/macrophage; Viral hepatitis.