Hepatitis C Virus Resistance to Carbohydrate-Binding Agents

Izquierdo, Laure; Oliveira, Catarina; Fournier, Carole; Descamps, Véronique; Morel, Virginie; Dubuisson, Jean; Brochot, Etienne; Francois, Catherine; Castelain, Sandrine; Duverlie, Gilles; Helle, Francois

In case of Human Immunodeficiency Virus (HIV), it has been proposed that a CBA-based therapeutic strategy could not only directly inhibit viruses, but also induce partial loss of the glycan shield and make viruses more vulnerable to attack by the immune system [40, 41] . Interestingly, we observed that even if no resistance mutation could be evidenced in the E1E2 HCV envelope glycoproteins, the positive selection which occurred led to a modification of the HCV glycan shield. Indeed, among the identified mutations, the S449P amino acid change prevents the N-glycosylation of the asparagine 448 residue corresponding to the E2N4 glycosylation site which is important for HCV particle assembly and infectivity as well as protection against neutralization. Using the 3/11 neutralizing MAb, we confirmed that this mutation renders the viral particle more sensitive to neutralization. We also identified the mutation N417S which has previously been thoroughly characterized. This mutation (or the related mutation N417T) has been described as an adaptive mutation enhancing the entry process in vitro [42] [43] [44] [45] [46] . In our study, this mutation was responsible for a 1.7-fold increase of the infectivity but this was not significant. This mutation is also known to lead to a shift of the E2N1 N-glycan from N417 to N415, which prevents the recognition of N415 residue by several neutralizing antibodies, as observed here with the 3/11 neutralizing MAb [26, 37, 38, 47, 48] . Interestingly, dose response curves using single, double and triple mutants suggest that this mutation was also responsible for an increased sensitivity to GNA (Fig 5A and data not shown) . Since GNA binds to mannose termini and lactosamine structures that are present in high-mannose-, hybrid-and complextype N-glycans, the increased sensitivity may not be caused by a difference of N-glycan maturation. Instead, a better accessibility of the E2N1 N-glycan to the GNA could explain this feature. Interestingly, our results reveal that the mutation L612M, which may be critical for the overall E2 architecture [49] , also increases the sensitivity to GNA (Fig 5A and data not shown) . However, caution must be taken because such mutations which do not confer lectin resistance but increase the sensitivity to neutralizing antibodies may not be fixed in vivo, in the presence of the humoral immunity. Thus, in contrast to HIV [40, 41] , it seems unlikely that development of HCV resistance against CBAs would result in an enhancement of neutralization by the immune system.