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.
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. 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)