Identification of a Broadly Cross-Reacting and Neutralizing Human Monoclonal Antibody Directed against the Hepatitis C Virus E2 Protein

Abstract

Identification of anti-hepatitis C virus (anti-HCV) human antibody clones with broad neutralizing activity is important for a better understanding of the interplay between the virus and host and for the design of an effective passive immunotherapy and an effective vaccine. We report the identification of a human monoclonal Fab (e137) able to bind the HCV E2 glycoprotein of all HCV genotypes but genotype 5. The results of antibody competition assays and testing the reactivity to alanine mutant E2 proteins confirmed that the e137 epitope includes residues (T416, W420, W529, G530, and D535) highly conserved across all HCV genotypes. Fab e137 neutralized HCV pseudoparticles bearing genotype 1a, 1b, and 4 E1-E2 proteins and to a lesser extent, genotype 2b. Fab e137 was also able to inhibit cell culture-grown HCV (genotype 2a). These data indicate that broadly cross-reacting and cross-neutralizing antibodies are generated during HCV infection.

Naturally selected hepatitis C virus polymorphisms confer broad neutralizing antibody resistance

“…However, isolation of human mAbs capable of neutralizing multiple diverse HCV isolates has shown that nAbs may also target more conserved regions of the E1 and E2 proteins (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). Discovery of these broadly neutralizing mAbs has raised hope that a vaccine inducing similar nAbs could prevent HCV infection.…”

Hepatitis C Patient-Derived Glycoproteins Exhibit Marked Differences in Susceptibility to Serum Neutralizing Antibodies: Genetic Subtype Defines Antigenic but Not Neutralization Serotype

“…The E1 and E2 (E1E2) glycoproteins mediate the entry of the virus into host cells (3,14,45) and are important targets for the host neutralizing antibody response (23,24,30,44,46). Several lines of evidence suggest that neutralizing antibodies have a protective role in vivo.…”

“…Broadly conserved, linear neutralization epitopes, for example, those recognized by MAb AP33 and MAb 3/11, have been described (43,58), but antibodies targeting these epitopes are rare in natural infection (56). The majority of neutralizing antibodies targeting the CD81 binding site recognize conformation-sensitive epitopes located on discontinuous regions of E2 (23,27,44,46). It remains to be demonstrated if the broadly neutralizing antibodies described here recognize epitopes similar to those previously described for CD81 binding site-targeted MAbs; it is unlikely that they recognize the same epitope as MAb AP33, as none reacted to a peptide recognized by MAb AP33 (58 and data not shown).…”

“…We have demonstrated previously that antibodies directed to the E1E2 glycoproteins preferen-tially recognize homologous proteins in genotype 1 and 3 infections (22). Here, we have used our panel of well-characterized E1E2 glycoprotein clones (26,27,43,44,46) to test the cross-reactivity and neutralization potency of a panel of homologous and heterologous human serum IgG from genotype 1, 2, and 3 infections. Using immobilized native and denatured E1E2, we demonstrate that cross-reactive antibodies generally target conformational epitopes.…”

“…The majority of neutralizing antibodies described to date are directed against linear or conformation-sensitive epitopes located within or proximal to the CD81 binding regions (23,27,35,43,44,46) or to epitopes located in the first hypervariable region of E2. Antibodies targeting the latter region presumably mediate their neutralizing effect by blocking the interaction between E2 and scavenger receptor class B type I (SR-BI) (5,49).…”