Naturally occurring dipeptide from elite controllers with dual anti-HIV-1 mechanism

We have reported enhanced levels of a dipeptide, WG-am, among elite controllers, patients who spontaneously control their HIV-1 infection. The aim of the present work was to evaluate its anti-HIV-1 activity and mechanism of action. Our data suggest that WG-am binds to the CD4 binding pocket of HIV-1 gp120 and blocks its binding to the host cell receptors. Additionally, our time course assay showed that WG-am inhibited HIV-1 also at 4-6h post-infection, suggesting a second antiviral mechanism. Drug sensitivity assays under acidic wash conditions confirmed the ability of WG-am to internalize into the host cell in an HIV independent manner. Proteomic studies showed a clustering of all samples treated with WG-am independent on the number of doses or presence or absence of HIV-1. Differentially expressed proteins due to the WG-am treatment indicated an effect on HIV-1 reverse transcription, which was confirmed by RT-PCR. Naturally occurring in HIV-1 elite controllers, WG-am stands out as a new kind of antiviral compound with two independent inhibitory mechanisms of action on HIV-1 replication. WG-am halts HIV-1 entry to the host cell by binding to HIV-1 gp120, thereby blocking the binding of HIV-1 to the host cell. It has also a post-entry, but pre-integration antiviral effect related to inhibition of RT-activity.

Hepatitis B virus envelope proteins can serve as therapeutic targets embedded in the host cell plasma membrane

Hepatitis B virus (HBV) infection is a major health threat causing 880,000 deaths each year. Available therapies control viral replication but do not cure HBV, leaving patients at risk to develop hepatocellular carcinoma. Here, we show that HBV envelope proteins (HBs)-besides their integration into endosomal membranes-become embedded in the plasma membrane where they can be targeted by redirected T-cells. HBs was detected on the surface of HBV-infected cells, in livers of mice replicating HBV and in HBV-induced hepatocellular carcinoma. Staining with HBs-specific recombinant antibody MoMab recognising a conformational epitope indicated that membrane-associated HBs remains correctly folded in HBV-replicating cells in cell culture and in livers of HBV-transgenic mice in vivo. MoMab coated onto superparamagnetic iron oxide nanoparticles allowed to detect membrane-associated HBs after HBV infection by electron microscopy in distinct stretches of the hepatocyte plasma membrane. Last but not least, we demonstrate that HBs located on the cell surface allow therapeutic targeting of HBV-positive cells by T-cells either engrafted with a chimeric antigen receptor or redirected by bispecific, T-cell engager antibodies. TAKE AWAYS: HBs become translocated to the plasma membrane. Novel, recombinant antibody confirmed proper conformation of HBs on the membrane. HBs provide an interesting target by T-cell-based, potentially curative therapies.

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

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.

Hepatitis B virus promotes β-catenin-signalling and disassembly of adherens junctions in a Src kinase dependent fashion

Hepatitis B virus (HBV) infection is a prominent cause of hepatocellular carcinoma (HCC) but the underlying molecular mechanisms are complex and multiple pathways have been proposed such as the activation of the Wnt-/β-catenin-signalling and dysregulation of E-cadherin/β-catenin adherens junctions. This study aimed to identify mechanisms of how HBV infection and replication as well as HBV X protein (HBx) gene expression in the context of an HBV genome influence Wnt-/β-catenin-signalling and formation of adherens junctions and to which extent HBx contributes to this. Regulation of E-cadherin/β-catenin junctions and β-catenin-signalling as well as the role of HBx were investigated using constructs transiently or stably inducing replication of HBV+/-HBx in hepatoma cell lines. In addition, HCC and adjacent non-tumorous tissue samples from HBV-infected HCC patients and drug interference in HBV-infected cells were studied. Although HBV did not alter overall expression levels of E-cadherin or β-catenin, it diminished their cell surface localization resulting in nuclear translocation of β-catenin and activation of its target genes. In addition, HBV gene expression increased the amount of phosphorylated c-Src kinase. Treatment with Src kinase inhibitor Dasatinib reduced HBV replication, prevented adherens junction disassembly and reduced β-catenin-signalling, while Sorafenib only did so in cells with mutated β-catenin. Interestingly, none of the HBV induced alterations required HBx. Thus, HBV stimulated β-catenin-signalling and induced disassembly of adherens junctions independently of HBx through Src kinase activation. These pathways may contribute to hepatocellular carcinogenesis and seem to be more efficiently inhibited by Dasatinib than by Sorafenib.