The neutralizing activity of anti-HCV antibodies is modulated by specific 2 glycans on the E 2 envelope protein 3 4

1 2 Hepatitis C virus (HCV) envelope glycoproteins are highly glycosylated, with up to five and 3 eleven N-linked glycans on E1 and E2, respectively. Most of the glycosylation sites on HCV 4 envelope glycoproteins are conserved, and some of the glycans associated with these proteins 5 have been shown to play an essential role in protein folding and HCV entry. Such a high level of 6 glycosylation suggests that these glycans can limit the immunogenicity of HCV envelope 7 proteins and restrict the binding of some antibodies to their epitopes. Here, we investigated 8 whether these glycans can modulate the neutralizing activity of anti-HCV antibodies. HCV 9 pseudoparticles (HCVpp) bearing wild-type glycoproteins or mutants at individual glycosylation 10 sites were evaluated for their sensitivity to neutralization by antibodies from the sera of infected 11 patients and anti-E2 monoclonal antibodies. While we did not find any evidence that N-linked 12 glycans of E1 contribute to the masking of neutralizing epitopes, our data demonstrate that at 13 least three glycans on E2 (denoted E2N1, E2N6 and E2N11) reduce the sensitivity of HCVpp to 14 antibody neutralization. Importantly, these three glycans also reduced the access of CD81 to its 15 E2 binding site, as shown by using a soluble form of the extracellular loop of CD81 in inhibition 16 of entry. These data suggest that glycans E2N1, E2N6 and E2N11 are close to the binding site of 17 CD81 and modulate both CD81 and neutralizing antibody binding to E2. In conclusion, this work 18 indicate that HCV glycans contribute to the evasion of HCV from the humoral immune response. 19 AC CE PT ED at P nn S ate U iv on F ebuary 2, 2008 jv.asm .rg D ow nladed fom