Sialylation of HCV E2 Glycoprotein-Specific and Natural Anti-Glycan (TF, αGal) Antibodies as Signatures of Liver Damage

The E2 glycoprotein is the target of broadly neutralizing antibodies against Hepatitis C Virus (HCV). There is evidence that the HCV E2-specific antibody glycosylation profile is associated with hepatic fibrosis progression. The main aim of this study was to compare the sialylation of E2-specific and naturally occurring antiglycan Abs to determine whether their combination could be beneficial for the non-invasive evaluation of hepatic damage. Fifty-eight patients with various stages of hepatic fibrosis or without were tested. The sialylation of HCV E2 glycoprotein-specific antibodies (E2-Abs), the Thomsen-Friedenreich antigen- and αGal glycotope-specific antibodies (TF-Abs, αGal-Abs) was analysed using the ELISA platform. The level of IgG Abs and their reactivity to Sialospecific Sambucus Nigra Lectin (SNA) were determined and changes in Abs sialylation were analysed based on the stage of liver fibrosis, HCV genotype and antiviral therapy efficacy. The late stage of liver Fibrosis (F4) was characterized by dramatically decreased E2-Ab SNA reactivity unlike stages with no fibrosis (P=0.003) and stages F1–F3 (P=0.0007). In contrast, antiglycan Abs showed an increased sialylation. In multiple regression analysis, the combination of E2 and TF-Abs sialylation patterns gave a significant advantage in assessing liver damage. A high rate of discrimination between F0 and F4 stages of fibrosis as well as between F1–F3 and F4 was obtained (ACC=0.948 and ACC=0.90, respectively). Thus, the combined analysis of disease-specific and natural Abs sialylation can remarkably enhance the clinical value of the approach in the non-invasive evaluation of hepatic damage.

Design and Synthesis of HCV-E2 Glycoprotein Epitope Mimics in Molecular Construction of Potential Synthetic Vaccines

Hepatitis C virus remains a global threat, despite the availability of highly effective direct-acting antiviral (DAA) drugs. With thousands of new infections annually, the need for a prophylactic vaccine is evident. However, traditional vaccine design has been unable to provide effective vaccines so far. Therefore, alternative strategies need to be investigated. In this work, a chemistry-based approach is explored towards fully synthetic peptide-based vaccines using epitope mimicry, by focusing on highly effective and conserved amino acid sequences in HCV, which, upon antibody binding, inhibit its bio-activity. Continuous and discontinuous epitope mimics were both chemically synthesized based on the HCV-E2 glycoprotein while using designed fully synthetic cyclic peptides. These cyclic epitope mimics were assembled on an orthogonally protected scaffold. The scaffolded epitope mimics have been assessed in immunization experiments to investigate the elicitation of anti-HCV-E2 glycoprotein antibodies. The neutralizing potential of the elicited antibodies was investigated, representing a first step in employing chemically synthesized epitope mimics as a novel strategy towards vaccine design.