Hypoxic gene expression in chronic hepatitis B virus infected patients is not observed in state-of-the-art in vitro and mouse infection models

Abstract

Hepatitis B virus (HBV) is the leading cause of hepatocellular carcinoma (HCC) worldwide. The prolyl hydroxylase domain (PHD)-hypoxia inducible factor (HIF) pathway is a key mammalian oxygen sensing pathway and is frequently perturbed by pathological states including infection and inflammation. We discovered a significant upregulation of hypoxia regulated gene transcripts in patients with chronic hepatitis B (CHB) in the absence of liver cirrhosis. We used state-of-the-art in vitro and in vivo HBV infection models to evaluate a role for HBV infection and the viral regulatory protein HBx to drive HIF-signalling. HBx had no significant impact on HIF expression or associated transcriptional activity under normoxic or hypoxic conditions. Furthermore, we found no evidence of hypoxia gene expression in HBV de novo infection, HBV infected human liver chimeric mice or transgenic mice with integrated HBV genome. Collectively, our data show clear evidence of hypoxia gene induction in CHB that is not recapitulated in existing models for acute HBV infection, suggesting a role for inflammatory mediators in promoting hypoxia gene expression.

Hypoxia inducible factors regulate hepatitis B virus replication by activating the basal core promoter

“…To understand whether HIF-2α transcriptional activity dominates in the HBV-infected liver we investigated the relative contribution of HIF-1α or HIF-2α activity in CHB biopsy samples. 21 38 of the hypoxia genes showing increased expression in CHB were defined as HIF-1α (n = 26), HIF-2α (n = 11) or co-regulated (n = 1) genes, 33 showing clear evidence for both HIF-1α and HIF-2α transcriptional activity in vivo . These data show the complexities of studying viral and host transcriptional responses to low oxygen in PHHs ex vivo.…”

“…HBV integrants are thought to be the major source of HBsAg expression in chronic disease that have been associated with exhausted antiviral T cell responses. 1 , 50 Our observation that integrant encoded preS1/S transcripts are oxygen-insensitive is relevant if one considers the hypoxic nature of the HCC environment 21 , 51 and how this could influence HBsAg expression, a biomarker for monitoring patients’ response to new therapies. 52 …”

“…HBV integrants are thought to be the major source of HBsAg expression in chronic disease that have been associated with exhausted anti-viral T cell responses[1,50]. Our observation that integrant encoded preS1/S transcripts and HBsAg expression are oxygen-insensitive is relevant if one considers the hypoxic nature of HCC environment[21,51] and how this could influence HBsAg expression that is considered a biomarker for monitoring patients' response to new therapies[52].In summary, we demonstrate a new role for HIFs to positively regulate HBV transcription. A hypoxic environment was also reported to potentiate hepatitis C virus replication via HIF-dependent[53,54] and independent[55] pathways.…”

“…Fig.2 2 22a a a a). We recently reported increased expression of hypoxia regulated gene transcripts in chronic hepatitis B (CHB)[21], enabling us to identify hepatic HIF-target genes for inclusion in a customized nCounter (Nanostring) array together with a probe to measure HBV RNA. The HBV probe detected a 400-fold range in viral RNA counts amongst the CHB samples (Fig.…”

Quantitative analysis of the splice variants expressed by the major hepatitis B virus genotypes

“…The PacBio circular consensus sequencing reads analysed in this study have been previously published and can be found in the European Nucleotide Archive (PRJEB12450) [1]. The RNA-seq libraries of hepatitis B virus (HBV)-positive biopsy samples of human liver tumours and tissues, and portal vein tumour thrombosis (129, 182 and 92 libraries, respectively), and HBV-infected primary human hepatocytes (83 libraries) and human cultured cells HepaRG (4 libraries) and HepG2-NTCP (11 libraries) were downloaded from the Sequence Read Archive [2–18] (see the metadata in Table S1, available with the online version of this article).…”