Eric Robinet

Clearance of persistent hepatitis C virus infection in humanized mice using a claudin-1-targeting monoclonal antibody

Hepatitis C virus (HCV) infection is a leading cause of liver cirrhosis and cancer. Cell entry of HCV and other pathogens is mediated by tight junction (TJ) proteins, but successful therapeutic targeting of TJ proteins has not been reported yet. Using a human liver–chimeric mouse model, we show that a monoclonal antibody specific for the TJ protein claudin-1 (ref. 7) eliminates chronic HCV infection without detectable toxicity. This antibody inhibits HCV entry, cell-cell transmission and virus-induced signaling events. Antibody treatment reduces the number of HCV-infected hepatocytes in vivo, highlighting the need for de novo infection by means of host entry factors to maintain chronic infection. In summary, we demonstrate that an antibody targeting a virus receptor can cure chronic viral infection and uncover TJ proteins as targets for antiviral therapy.

Synergy of entry inhibitors with direct-acting antivirals uncovers novel combinations for prevention and treatment of hepatitis C.

Objective Although direct-acting antiviral agents (DAAs) have markedly improved the outcome of treatment in chronic HCV infection, there continues to be an unmet medical need for improved therapies in difficult-to-treat patients as well as liver graft infection. Viral entry is a promising target for antiviral therapy. Design Aiming to explore the role of entry inhibitors for future clinical development, we investigated the antiviral efficacy and toxicity of entry inhibitors in combination with DAAs or other host-targeting agents (HTAs). Screening a large series of combinations of entry inhibitors with DAAs or other HTAs, we uncovered novel combinations of antivirals for prevention and treatment of HCV infection. Results Combinations of DAAs or HTAs and entry inhibitors including CD81-, scavenger receptor class B type I (SR-BI)- or claudin-1 (CLDN1)-specific antibodies or small-molecule inhibitors erlotinib and dasatinib were characterised by a marked and synergistic inhibition of HCV infection over a broad range of concentrations with undetectable toxicity in experimental designs for prevention and treatment both in cell culture models and in human liver-chimeric uPA/SCID mice. Conclusions Our results provide a rationale for the development of antiviral strategies combining entry inhibitors with DAAs or HTAs by taking advantage of synergy. The uncovered combinations provide perspectives for efficient strategies to prevent liver graft infection and novel interferon-free regimens.

Identification of an alternative CD20 transcript variant in B-cell malignancies coding for a novel protein associated to rituximab resistance

Human CD20 is a B-cell lineage-specific marker expressed by normal and leukemic B cells from the pre-B to the plasma-cell stages and is a target for rituximab (RTX) immunotherapy. A CD20 reverse transcriptase-polymerase chain reaction (PCR) on B-cell lines cDNA yielded a short PCR product (DeltaCD20) corresponding to a spliced mRNA transcript linking the exon 3 and exon 7 ends. We established here that this novel, alternatively spliced CD20 transcript is expressed and detectable at various levels in leukemic B cells, lymphoma B cells, in vivo tonsil- or in vitro CD40L-activated B cells, and Epstein-Barr virus (EBV)-transformed B cells, but not in resting CD19(+)- or CD20(+)-sorted B cells from peripheral blood or bone marrow of healthy donors. The truncated CD20 sequence is within the reading frame, codes a protein of 130 amino acids ( approximately 15-17 kDa) lacking large parts of the 4 transmembrane segments, suggesting that DeltaCD20 is a nonanchored membrane protein. We demonstrated the translation into a DeltaCD20 protein which is associated with the membrane CD20 protein and showed its involvement in RTX resistance. Study of patient samples before and after RTX resistance or escape confirms our in vitro findings.

Hepatitis C virus infection and related liver disease: the quest for the best animal model

Hepatitis C virus (HCV) is a major cause of cirrhosis and hepatocellular carcinoma (HCC) making the virus the most common cause of liver failure and transplantation. HCV is estimated to chronically affect 130 million individuals and to lead to more than 350,000 deaths per year worldwide. A vaccine is currently not available. The recently developed direct acting antivirals (DAAs) have markedly increased the efficacy of the standard of care but are not efficient enough to completely cure all chronically infected patients and their toxicity limits their use in patients with advanced liver disease, co-morbidity or transplant recipients. Because of the host restriction, which is limited to humans and non-human primates, in vivo study of HCV infection has been hampered since its discovery more than 20 years ago. The chimpanzee remains the most physiological model to study the innate and adaptive immune responses, but its use is ethically difficult and is now very restricted and regulated. The development of a small animal model that allows robust HCV infection has been achieved using chimeric liver immunodeficient mice, which are therefore not suitable for studying the adaptive immune responses. Nevertheless, these models allowed to go deeply in the comprehension of virus-host interactions and to assess different therapeutic approaches. The immunocompetent mouse models that were recently established by genetic humanization have shown an interesting improvement concerning the study of the immune responses but are still limited by the absence of the complete robust life cycle of the virus. In this review, we will focus on the relevant available animal models of HCV infection and their usefulness for deciphering the HCV life cycle and virus-induced liver disease, as well as for the development and evaluation of new therapeutics. We will also discuss the perspectives on future immunocompetent mouse models and the hurdles to their development.

A first step towards a mouse model for hepatitis C virus infection containing a human immune system

BACKGROUND & AIMSnStudies of hepatitis C virus (HCV) infection, immunopathogenesis, and resulting liver diseases have been hampered by the lack of a small animal model. We developed humanized mice with human immune system and liver tissues to improve the studies of hepatitis C pathogenesis and treatment.nnnMETHODSnTo promote engraftment of human hepatocytes, we expressed a fusion protein of the FK506 binding protein (FKBP) and caspase 8 under the control of the albumin promoter (AFC8), which induces liver cell death, in Balb/C Rag2(-/-) γC-null mice. Co-transplantation of human CD34(+) human hematopoietic stem cells (HSC) and hepatocyte progenitors into the transgenic mice led to efficient engraftment of human leucocytes and hepatocytes. We then infected these humanized mice (AFC8-hu HSC/Hep) with primary HCV isolates and studied HCV-induced immune responses and liver diseases.nnnRESULTSnAFC8-hu HSC/Hep mice supported HCV infection in the liver and generated a human immune T-cell response against HCV. HCV infection induced liver inflammation, hepatitis, and fibrosis, which correlated with activation of stellate cells and expression of human fibrogenic genes.nnnCONCLUSIONSnAFC8-hu HSC/Hep mice are a useful model of HCV infection, the immune response, and liver disease, because they contain human immune system and liver cells. These mice become infected with HCV, generate a specific immune response against the virus, and develop liver diseases that include hepatitis and fibrosis. This model might also be used to develop therapeutics for HCV infection.

In Vivo Proof of Concept of Adoptive Immunotherapy for Hepatocellular Carcinoma Using Allogeneic Suicide Gene-modified Killer Cells

Cell therapy based on alloreactivity has completed clinical proof of concept against hematological malignancies. However, the efficacy of alloreactivity as a therapeutic approach to treat solid tumors is unknown. Using cell culture and animal models, we aimed to investigate the efficacy and safety of allogeneic suicide gene-modified killer cells as a cell-based therapy for hepatocellular carcinoma (HCC), for which treatment options are limited. Allogeneic killer cells from healthy donors were isolated, expanded, and phenotypically characterized. Antitumor cytotoxic activity and safety were studied using a panel of human or murine HCC cell lines engrafted in immunodeficient or immunocompetent mouse models. Human allogeneic suicide gene-modified killer cells (aSGMKCs) exhibit a high, rapid, interleukin-2-dependent, and non-major histocompatibility complex class I-restricted in vitro cytotoxicity toward human hepatoma cells, mainly mediated by natural killer (NK) and NK-like T cells. In vivo evaluation of this cell therapy product demonstrates a marked, rapid, and sustained regression of HCC. Preferential liver homing of effector cells contributed to its marked efficacy. Calcineurin inhibitors allowed preventing rejection of allogeneic lymphocytes by the host immune system without impairing their antitumor activity. Our results demonstrate proof of concept for aSGMKCs as immunotherapy for HCC and open perspectives for the clinical development of this approach.

Potent calcium phosphate nanoparticle surface coating for in vitro and in vivo siRNA delivery: a step toward multifunctional nanovectors

The present study describes hybrid nanoparticles, built by alternate deposition of siRNA and modified polyethyleneimine (tyrosine-grafted PEI or tyrosine/galactose-grafted PEI) on calcium phosphate nanoparticles. These easy to produce nanoparticles (NPs) present an efficient gene silencing effect demonstrated in vitro in a luciferase expressing cell culture model and in vivo in a tumour xenograft mouse model. The luciferase gene silencing percentage reached up to 95% in vitro with biocompatible doses of siRNA. Interestingly, we show by SPECT imaging of radiolabeled particles that without modifying the size, stability and in vitro efficiency, the grafting of a sugar moiety on PEI can modify the in vivo biodistribution of the particles. The proof of concept that galactose-grafting on PEI could change biodistribution without changing the gene silencing efficiency makes them versatile tools for specific delivery of small interfering RNA. As they have been designed so far, biodistribution is mainly located in the liver and thus these innovative nanoparticles open a realistic and feasible strategy for siRNA delivery into the liver in vivo.

Host and viral determinants for engraftment of virus permissive human hepatocytes into chimeric immunodeficient mice

Editorial on Vanwolleghem et al. ‘‘Factors determining successful engraftment of hepatocytes and susceptibility to hepatitis B and C virus infection in uPA-SCID mice.” J. Hepatol. 2010, September issue. Hepatitis C virus (HCV) infection is a major cause of chronic liver disease including liver cirrhosis and hepatocellular carcinoma [1]. The current antiviral therapy is characterized by limited efficacy, high costs, and substantial side effects. A vaccine for the prevention of HCV infection is not available. Thus, novel strategies for the prevention and treatment of HCV infection are urgently needed (for a review see [1,2]). The development of efficient antiviral treatments and vaccines has been hampered by the lack of a convenient small animal model for HCV infection. Although HCV has been shown to enter into mouse cell lines expressing human HCV receptors [3], mouse hepatocytes are unable to produce infectious HCV infection [4]. Over the past two decades the chimpanzee has been commonly used to study mechanisms of acute and chronic HCV infection (for review see [21]). These studies have enormously contributed to our current understanding of HCV infection [5] as well as the preclinical evaluation of antivirals [6]. However, the chimpanzee model is characterized by limited availability, high costs, and important ethical restrictions. Furthermore, hepatocytes of the tree shrew Tupaia belangeri are susceptible to HCV infection [8]. However, viral load in infected animals is low [9]. The discovery of a hepatocyte-lethal phenotype in mice carrying a urokinase-type plasminogen activator transgene controlled by an albumin promotor (Alb-uPA) with the reconstitution of livers of those mice with xenografted rat hepatocytes [10] has laid the foundation for the development of small animal models of infection with hepatitis B and C viruses using xenografted primary human hepatocytes (PHH) (for review see [7]). The uPA-xenograft model had been first established for the development of a hepatitis B mouse model by transplanting woodchuck or PHH into Alb-uPA mice on an immunodeficient recombination activating gene 2 knock-out (Rag-2 / ) background. Repopulating woodchuck hepatocytes in Alb-uPA/rag-2

Humanisation of a claudin-1-specific monoclonal antibody for clinical prevention and cure of HCV infection without escape

Objective HCV infection is a leading cause of chronic liver disease and a major indication for liver transplantation. Although direct-acting antivirals (DAAs) have much improved the treatment of chronic HCV infection, alternative strategies are needed for patients with treatment failure. As an essential HCV entry factor, the tight junction protein claudin-1 (CLDN1) is a promising antiviral target. However, genotype-dependent escape via CLDN6 and CLDN9 has been described in some cell lines as a possible limitation facing CLDN1-targeted therapies. Here, we evaluated the clinical potential of therapeutic strategies targeting CLDN1. Design We generated a humanised anti-CLDN1 monoclonal antibody (mAb) (H3L3) suitable for clinical development and characterised its anti-HCV activity using cell culture models, a large panel of primary human hepatocytes (PHH) from 12 different donors, and human liver chimeric mice. Results H3L3 pan-genotypically inhibited HCV pseudoparticle entry into PHH, irrespective of donor. Escape was likely precluded by low surface expression of CLDN6 and CLDN9 on PHH. Co-treatment of a panel of PHH with a CLDN6-specific mAb did not enhance the antiviral effect of H3L3, confirming that CLDN6 does not function as an entry factor in PHH from multiple donors. H3L3 also inhibited DAA-resistant strains of HCV and synergised with current DAAs. Finally, H3L3 cured persistent HCV infection in human-liver chimeric uPA-SCID mice in monotherapy. Conclusions Overall, these findings underscore the clinical potential of CLDN1-targeted therapies and describe the functional characterisation of a humanised anti-CLDN1 antibody suitable for further clinical development to complement existing therapeutic strategies for HCV.

Adaptive Immunity to Hepatitis C Virus

The precise role of adaptive immune responses in the clinical outcome of HCV infection is still only partially defined. Recent studies suggest that viral-host cell interactions during the acute phase of infection are essential for viral clearance or progression into chronic HCV infection. This review focuses on different aspects of the adaptive immune responses as determinants of the different outcomes of HCV infection, clearance or persistent infection, and outlines current concepts of HCV evasion strategies. Unravelling these important mechanisms of virus-host interaction will contribute to the development of novel strategies to prevent and control HCV infection.