Neutralizing antibodies and pathogenesis of hepatitis C virus infection.

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease worldwide. The interplay between the virus and host innate and adaptive immune responses determines the outcome of infection. There is increasing evidence that host neutralizing responses play a relevant role in the resulting pathogenesis. Furthermore, viral evasion from host neutralizing antibodies has been revealed to be an important contributor in leading both to viral persistence in acute liver graft infection following liver transplantation, and to chronic viral infection. The development of novel model systems to study HCV entry and neutralization has allowed a detailed understanding of the molecular mechanisms of virus-host interactions during antibody-mediated neutralization. The understanding of these mechanisms will ultimately contribute to the development of novel antiviral preventive strategies for liver graft infection and an urgently needed vaccine. This review summarizes recent concepts of the role of neutralizing antibodies in viral clearance and protection, and highlights consequences of viral escape from neutralizing antibodies in the pathogenesis of HCV infection

Scavenger receptor class B type I is a key host factor for hepatitis C virus infection required for an entry step closely linked to CD81.

International audienceHepatitis C virus (HCV) is a major cause of chronic hepatitis worldwide. Scavenger receptor class B type I (SR-BI) has been shown to bind HCV envelope glycoprotein E2, participate in entry of HCV pseudotype particles, and modulate HCV infection. However, the functional role of SR-BI for productive HCV infection remains unclear. In this study, we investigated the role of SR-BI as an entry factor for infection of human hepatoma cells using cell culture-derived HCV (HCVcc). Anti-SR-BI antibodies directed against epitopes of the human SR-BI extracellular loop specifically inhibited HCVcc infection in a dose-dependent manner. Down-regulation of SR-BI expression by SR-BI-specific short interfering RNAs (siRNAs) markedly reduced the susceptibility of human hepatoma cells to HCVcc infection. Kinetic studies demonstrated that SR-BI acts predominately after binding of HCV at an entry step occurring at a similar time point as CD81-HCV interaction. Although the addition of high-density lipoprotein (HDL) enhanced the efficiency of HCVcc infection, anti-SR-BI antibodies and SR-BI-specific siRNA efficiently inhibited HCV infection independent of lipoprotein. Conclusion: Our data suggest that SR-BI (i) represents a key host factor for HCV entry, (ii) is implicated in the same HCV entry pathway as CD81, and (iii) targets an entry step closely linked to HCV-CD81 interaction

Viral entry and escape from antibody-mediated neutralization influence hepatitis C virus reinfection in liver transplantation

End-stage liver disease caused by chronic hepatitis C virus (HCV) infection is a leading cause for liver transplantation (LT). Due to viral evasion from host immune responses and the absence of preventive antiviral strategies, reinfection of the graft is universal. The mechanisms by which the virus evades host immunity to reinfect the liver graft are unknown. In a longitudinal analysis of six HCV-infected patients undergoing LT, we demonstrate that HCV variants reinfecting the liver graft were characterized by efficient entry and poor neutralization by antibodies present in pretransplant serum compared with variants not detected after transplantation. Monoclonal antibodies directed against HCV envelope glycoproteins or a cellular entry factor efficiently cross-neutralized infection of human hepatocytes by patient-derived viral isolates that were resistant to autologous host-neutralizing responses. These findings provide significant insights into the molecular mechanisms of viral evasion during HCV reinfection and suggest that viral entry is a viable target for prevention of HCV reinfection of the liver graft

Caractéristiques épidémiologiques et cliniques des infections respiratoires aiguës virales du nourrisson au centre hospitalier universitaire de Strasbourg par une approche diagnostique moléculaire par pcr multiplex

STRASBOURG ILLKIRCH-Pharmacie (672182101) / SudocSudocFranceF

Prévention de la réinfection par le virus de l'hépatite C lors de la transplantation hépatique par l'utilisation d'anticorps monoclonaux anti-récepteur

Le virus de l hépatite C (VHC) représente un problème de santé publique majeur. Environ 170 millions de personnes sont infectées dans le monde, et plus de 70% développeront une infection chronique. Le traitement actuel qui associe l interféron- pégylé et la ribavirine ne permet de guérir que 50% des patients tous génotypes confondus. Les complications de l hépatite C chronique, la cirrhose et le carcinome hépatocellulaire, représentent des indications majeures de transplantation hépatique (TH). Malheureusement la récurrence de l infection par le VHC sur le greffon est systématique et évolue vers une cirrhose en moins de 5 ans chez une proportion importante de patients. A l heure actuelle, il n y a pas de moyen de prévention de la réinfection du greffon par le VHC. Une meilleure connaissance des phases précoces de la réinfection permettrait le développement de stratégies préventives de l infection par le VHC. Durant ma thèse nous nous sommes intéressés aux mécanismes de la réinfection par le VHC au cours de la TH en nous focalisant sur l étape de l entrée virale dans l hépatocyte. Nous avons montré pour la première fois qu au cours de la TH, et contrairement aux variants non sélectionnés après la greffe, les variants du VHC sélectionnés après la greffe (qui réinfectent le greffon) entrent plus efficacement dans la cellule hôte et échappent à la neutralisation induite par les anticorps des sérums autologues collectés avant la greffe. Nous avons, par la suite, identifié les mutations impliquées dans l entrée et l échappement viral aux anticorps neutralisants. Ces mutations favorisent l entrée virale en modulant la dépendance du VHC à un des facteurs d entrée virale, le CD81. La protéine de jonction Claudine 1 (CLDN1) est un autre facteur d entrée essentiel à l infection par le VHC. Nous avons produit des anticorps monoclonaux anti-CLDN1 et montré que ces anticorps inhibent de manière spécifique tous les génotypes du VHC ainsi que les variants viraux résistants à la neutralisation par le sérum autologue lors de la TH. L ensemble de ces résultats suggère que l étape d entrée du virus pourrait constituer une cible prometteuse pour le développement de stratégies préventives de la réinfection du greffon par le VHC.Hepatitis C virus (HCV) is a major problem of public health. Approximatively 170 million individuals are infected worldwide, and more than 70% of infected individuals will develop chronic hepatitis. The current treatment based on pegylated interferon- and ribavirin can only cure 50 % of patients. HCV-related cirrhosis and hepatocellular carcinoma are a leading indication for liver transplantation (LT). The major limitation of LT is the universal re-infection of the liver graft. To date, there is no prophylactic strategy to prevent re-infection. A better understanding of the early phases of re-infection would allow developing of preventive strategies. During my PhD thesis, we focussed on the viral entry step to study the molecular mechanisms of re-infection of the liver graft. For the first time, we have demonstrated that during LT, selected variants re-infecting the liver graft show enhanced entry and escape from antibody-mediated neutralization. We identified two adaptive mutations in envelope glycoprotein E2 mediating enhanced entry and evasion of an highly infectious escape variant. These mutations markedly modulated CD81 receptor dependency resulting in enhanced viral entry. Among the host entry factors involved in viral entry, claudin 1 (CLDN1) is essential for HCV infection. We have produced monoclonal anti-CLDN1 antibodies and have shown that these antibodies specifically inhibit HCV entry from all major genotypes, as well as cell entry of the highly infectious escape variants of HCV that were resistant to autologous neutralizing antibodies. Taken together, these results suggest that targeting HCV entry into hepatocytes with specific monoclonal antibodies, as anti-CLDN1 antibodies, may constitute a novel antiviral approach to prevent primary HCV infection, such as after LT.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

ETUDE DE LA PERMISSIVITE DES CELLULES DENDRITIQUES A L'INFECTION PAR LE VIRUS DE L'HEPATITE C (MODIFICATION DE LEURS FONCTIONS)

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Lack of expression of hepatitis C virus core protein in human monocyte-erived dendritic cells using recombinant semliki forest virus

Hepatitis C Virus belongs to the Flaviviridae family.  One proposed mechanism of HCV persistence in the ability to infect hematopoietic cells, including Dendritic cells (DCs). HCV infection of DCs could impair their functions that represent one of the mechanisms, thus hampering viral clearance by the host immune system. Among HCV-encoded proteins, the highly conserved Core protein has been suggested to be responsible for the immunomodulatory properties of this Hepacivirus. Recombinant viral vectors expressing the HCV Core protein and allowing its transduction and therefore the expression of the protein into DCs could be useful tools for the analysis of the properties of the Core protein. Vaccinia Virus and retrovirus have been used to transduce human DCs. Likewise, gene transfer into DCs using Semliki Forest Virus has been reported. This study aimed to express the HCV Core protein in human monocyte-derived DCs using an SFV vector, in which the subgenomic RNA encoding the structural proteins was replaced by the HCV Core sequence and then analyze the effects of its expression on DCs functions

Development of hepatitis C virus vaccines: challenges and progress.

International audienceDevelopment of an effective vaccine against the hepatitis C virus (HCV) has long been defined as a difficult challenge due to the considerable variability of this RNA virus and the observation that convalescent humans and chimpanzees could be re-infected after re-exposure. On the other hand, progress in the understanding of antiviral immune responses in patients with viral clearance has elucidated key mechanisms playing a role in the control of viral infection. Studies investigating prophylactic vaccine approaches in chimpanzees have confirmed that the induction and maintenance of strong helper and cytotoxic T-cell immune responses against multiple viral epitopes is necessary for protection against viral clearance and chronic infection. A multispecific B-cell response, resulting in rapid induction of cross-neutralizing antibodies may assist cellular responses. Therapeutic vaccine formulations currently being evaluated in clinical trials are facing the fact that the immune system of chronic carriers is impaired and needs the restoration of T-cell functions to enhance their efficacy

Influenza prevention in nursing homes: Great significance of seasonal variability and spatio-temporal pattern.

International audienceThis work evaluated seasonal variations and spatio-temporal pattern of respiratory tract infections (RTI) in geriatric nursing homes in order to improve effective surveillance, prevention, control and management of RTI. Prospective surveillance of RTI (Low Respiratory Tract infections and Influenza Like Illnesses) was conducted in 11 sites in Alsace over a 10-year period with clinical case definitions and rapid tests (Immunoassay) to identify influenza virus. Influenza national epidemic was a period at high risk of RTI in nursing homes with variable impacts depending on the seasonal period. 2004-2005, 2008-2009, 2011-2012 and 2012-2013 were the periods with the highest impacts. The higher risk was not well understood during these four influenza epidemics and outbreaks occurred in numerous nursing homes despite the alerts and surveillance. Information about seasonal variability and spatio-temporal patterns of the RTI during the national epidemic periods is essential for the nursing homes in order to help the health care workers and the visitors to understand the risk for the residents and then to improve the implementation of the control and prevention measures