Hepatitis C Virus (HCV) Infection May Elicit Neutralizing Antibodies Targeting Epitopes Conserved in All Viral Genotypes

PLOS ONE, Dec 2009

Anti-hepatitis C virus (HCV) cross-neutralizing human monoclonal antibodies, directed against conserved epitopes on surface E2 glycoprotein, are central tools for understanding virus-host interplay, and for planning strategies for prevention and treatment of this infection. Recently, we developed a research aimed at identifying these antibody specificities. The characteristics of one of these antibodies (Fab e20) were addressed in this study. Firstly, using immunofluorescence and FACS analysis of cells expressing envelope HCV glycoproteins, Fab e20 was able to recognize all HCV genotypes. Secondly, competition assays with a panel of mouse and rat monoclonals, and alanine scanning mutagenesis analyses located the e20 epitope within the CD81 binding site, documenting that three highly conserved HCV/E2 residues (W529, G530 and D535) are critical for e20 binding. Finally, a strong neutralizing activity against HCV pseudoparticles (HCVpp) incorporating envelope glycoproteins of genotypes 1a, 1b, 2a, 2b and 4, and against the cell culture-grown (HCVcc) JFH1 strain, was observed. The data highlight that neutralizing antibodies against HCV epitopes present in all HCV genotypes are elicited during natural infection. Their availability may open new avenues to the understanding of HCV persistence and to the development of strategies for the immune control of this infection.

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Hepatitis C Virus (HCV) Infection May Elicit Neutralizing Antibodies Targeting Epitopes Conserved in All Viral Genotypes

et al. (2009) Hepatitis C Virus (HCV) Infection May Elicit Neutralizing Antibodies Targeting Epitopes Conserved in All Viral Genotypes. PLoS ONE 4(12): e8254. doi:10.1371/journal.pone.0008254 Hepatitis C Virus (HCV) Infection May Elicit Neutralizing Antibodies Targeting Epitopes Conserved in All Viral Genotypes Nicasio Mancini 0 Roberta A. Diotti 0 Mario Perotti 0 Giuseppe Sautto 0 Nicola Clementi 0 Giovanni 0 Nitti 0 Arvind H. Patel 0 Jonathan K. Ball 0 Massimo Clementi 0 Roberto Burioni 0 Sung Key Jang, Pohang University of Science and Technology, Republic of Korea 0 1 Laboratorio di Microbiologia e Virologia, Universita` ''Vita-Salute'' San Raffaele, Milano, Italia, 2 MRC Virology Unit, Institute of Virology, University of Glasgow , Church Street, Glasgow , United Kingdom , 3 Institute of Infection , Immunity and Inflammation , School of Molecular Medical Sciences, University of Nottingham, Queen's Medical Centre , Nottingham , United Kingdom Anti-hepatitis C virus (HCV) cross-neutralizing human monoclonal antibodies, directed against conserved epitopes on surface E2 glycoprotein, are central tools for understanding virus-host interplay, and for planning strategies for prevention and treatment of this infection. Recently, we developed a research aimed at identifying these antibody specificities. The characteristics of one of these antibodies (Fab e20) were addressed in this study. Firstly, using immunofluorescence and FACS analysis of cells expressing envelope HCV glycoproteins, Fab e20 was able to recognize all HCV genotypes. Secondly, competition assays with a panel of mouse and rat monoclonals, and alanine scanning mutagenesis analyses located the e20 epitope within the CD81 binding site, documenting that three highly conserved HCV/E2 residues (W529, G530 and D535) are critical for e20 binding. Finally, a strong neutralizing activity against HCV pseudoparticles (HCVpp) incorporating envelope glycoproteins of genotypes 1a, 1b, 2a, 2b and 4, and against the cell culture-grown (HCVcc) JFH1 strain, was observed. The data highlight that neutralizing antibodies against HCV epitopes present in all HCV genotypes are elicited during natural infection. Their availability may open new avenues to the understanding of HCV persistence and to the development of strategies for the immune control of this infection. - . These authors contributed equally to this work. The hepatitis C virus (HCV) infection is presently a major public health problem, and nearly 3% of the world population is persistently infected with this virus [1,2]. At least six major HCV genotypes and more than 50 subtypes have been described based on nucleotide diversity of the core, E1\E2, and NS5 regions [3,4,5]. Moreover, HCV infection is characterized by high intrahost variability, due to high mutation rate and replication activity in vivo. As a direct consequence of this variability, each HCVinfected patient harbours a population of related, but genetically distinct viral variants. It is presently believed that HCV variability strongly determines virus persistence in the infected hosts, allowing its escape from the immune system [6,7,8] . Despite almost two decades of studies, no vaccine is presently available to prevent infection with this virus. Efforts aimed at developing an anti-HCV vaccine have been hampered by the high virus variability, the substantial lack of readily available animal models, and the absence of clearly established in vitro correlates of protective immunity. It is currently believed that CD4+ and CD8+ T-cell responses are central in the control of acute HCV infection. Otherwise, the role of anti-HCV humoral response is still controversial [9,10,11]. However, recent data have suggested that neutralizing anti-HCV antibody responses may strongly influence the natural course of HCV infection. In this context, an effective immunization against HCV calls for induction of both robust Tand B-cell responses. As far as the latter point is concerned, this result is possible if new immunogens are designed, capable of eliciting broadly reacting and neutralizing antibodies. Recently, the availability of viral pseudotypes bearing surface HCV glycoproteins (E1 and E2) has offered a reliable model system to evaluate in vitro the anti-HCV neutralizing activity of polyclonal sera and monoclonal antibodies. Using this approach, it has been shown that neutralizing activity is detectable in sera from a significant proportion of infected patients during primary and persistent HCV infection [12,13], and that the presence of high titres of neutralizing antibodies directed against conserved epitopes may influence the virus-host interplay during all stages of the infection [14,15,16,17,18]. In the last few years, we have used phage-display to dissect the antibody response of HCV-infected patients, searching for potentially cross-reactive Fabs directed against HCV/E2. Using this approach, we have obtained several cross-reactive anti-HCV/E2 hum (...truncated)


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Nicasio Mancini, Roberta A. Diotti, Mario Perotti, Giuseppe Sautto, Nicola Clementi, Giovanni Nitti, Arvind H. Patel, Jonathan K. Ball, Massimo Clementi, Roberto Burioni. Hepatitis C Virus (HCV) Infection May Elicit Neutralizing Antibodies Targeting Epitopes Conserved in All Viral Genotypes, PLOS ONE, 2009, 12, DOI: 10.1371/journal.pone.0008254