# Hepatitis D virus infection triggers CXCL9-11 upregulation in hepatocytes and liver infiltration of CXCR3+ CD4 T cells

## TL;DR

Hepatitis D virus infection increases chemokine production in liver cells, leading to immune cell recruitment and inflammation.

## Contribution

This study identifies HDV-induced CXCL9-11 chemokine upregulation and CXCR3+ CD4 T cell infiltration in chronic hepatitis D.

## Key findings

- HDV-infected hepatocytes significantly upregulate CXCL9-11 chemokines in human and mouse models.
- CXCR3 is upregulated on peripheral CD4 T cells in CHD patients but not on virus-specific T cells.
- HBV/HDV coinfected livers show increased recruitment of CXCR3+ CD4 T cells, contributing to inflammation.

## Abstract

The role of hepatocytes in producing chemokines and triggering liver inflammation and damage in chronic hepatitis D (CHD) is not fully understood. Herein, we investigated the contribution of primary human hepatocytes (PHHs) infected with HDV in triggering inflammation by producing the chemokines CXCL9–11.

We performed quantitative PCR, RNA in situ hybridisation, activation-induced marker (AIM) assays, and FACS analysis to investigate the CXCR3/CXCL9–11 receptor/ligand axis of T cells in peripheral blood and livers from patients with chronic hepatitis B (n = 27 and 18, respectively) and CHD (n = 20 and 18, respectively). Chemokine expression was investigated in cultured HDV-infected PHHs and in livers of HBV- or HBV/HDV-infected humanised mice in the presence or absence of adoptively transferred human immune cells (n = 35 in total).

In patient and chimeric mouse livers, higher expression levels of CXCL9–11 were found in an HBV/HDV-coinfected vs. HBV-mono-infected setting. Similarly, high levels of CXCL9–11 were observed in HDV-infected PHHs in vitro. Analysis by RNA in situ hybridisation on patient livers revealed that HDV-infected hepatocytes were a significant contributor to the chemokine expression. The corresponding chemokine receptor CXCR3 was found upregulated specifically on peripheral bulk CD4 T cells of patients with CHD. CXCR3 upregulation was unspecific and was not detected on HDAg- or HBsAg-specific CD4 T cells by activation-induced marker assay. Lastly, adoptive transfer of human T cells in humanised mice led to recruitment of non-HBV/HDV-specific CD4+ T cells only in the setting of HBV/HDV coinfection, but not in HBV-mono-infected mice.

HDV infection upregulated the intrahepatic expression of the CXCL9–11/CXCR3 receptor/ligand axis. Higher amounts of HBV/HDV-unspecific CD4 T cells expressing CXCR3 may contribute to the aggravated liver inflammation frequently observed in patients with CHD.

Chronic hepatitis D (CHD) causes the most severe form of viral hepatitis, and treatment options are still limited; therefore, a more precise understanding of CHD immunopathology is needed. In this study, we demonstrated that HDV infection triggers CXCL9–11 expression in hepatocytes and liver infiltration of CXCR3-expressing CD4 T cells in preclinical models as well as patient biopsies. Because recruitment of Th1-polarised CD4 T cells to the liver has been also described for other severe liver diseases, such as autoimmune hepatitis, it may represent an important mechanism of aggravating liver diseases. The data of this study set hereby the basis for future studies analysing phenotype and function of intrahepatic T cells in CHD.

(1) Expression of CXCL9-11 is highly increased in HDV-infected hepatocytes and chemokines are secreted to the hepatic microenvironment. (2) The corresponding receptor CXCR3 is upregulated on peripheral bulk CD4 T cells of HDV-infected individuals (a), while this receptor is not upregulated on HBV/HDV-specific CD4 T cells (b). (3) Consequently, bulk CD4 T cells expressing CXCR3 are recruited and accumulate in HDV-infected livers.Image 1

(1) Expression of CXCL9-11 is highly increased in HDV-infected hepatocytes and chemokines are secreted to the hepatic microenvironment. (2) The corresponding receptor CXCR3 is upregulated on peripheral bulk CD4 T cells of HDV-infected individuals (a), while this receptor is not upregulated on HBV/HDV-specific CD4 T cells (b). (3) Consequently, bulk CD4 T cells expressing CXCR3 are recruited and accumulate in HDV-infected livers.

•CXCR3 ligands CXCL9-11 are the main chemokines induced upon HDV infection of human hepatocytes.•Patients with chronic hepatitis D show increased frequencies of circulating CXCR3-positive Th1-like cells.•HDV induced significant CXCR3 surface expression on total but not on HBsAg- or HDAg-specific CD4 T cells.•HDV-mediated increased recruitment of HBV/HDV-unspecific CXCR3-expressing T cells into the liver may contribute to inflammation.

CXCR3 ligands CXCL9-11 are the main chemokines induced upon HDV infection of human hepatocytes.

Patients with chronic hepatitis D show increased frequencies of circulating CXCR3-positive Th1-like cells.

HDV induced significant CXCR3 surface expression on total but not on HBsAg- or HDAg-specific CD4 T cells.

HDV-mediated increased recruitment of HBV/HDV-unspecific CXCR3-expressing T cells into the liver may contribute to inflammation.