In vitro adaptation and characterization of attenuated hypervariable region 1 swap chimeras of hepatitis C virus

Two-component vaccine consisting of virus-like particles displaying hepatitis C virus envelope protein 2 oligomers

Development of B-cell-based hepatitis C virus (HCV) vaccines that induce broadly neutralizing antibodies (bNAbs) is hindered by extensive sequence diversity and low immunogenicity of envelope glycoprotein vaccine candidates, most notably soluble E2 (sE2). To overcome this, we employed two-component approaches using self-assembling virus-like particles (cVLPs; component 1), displaying monomeric or oligomeric forms of HCV sE2 (sE2mono or sE2oligo; component 2). Immunization studies were performed in BALB/c mice and the neutralizing capacity of vaccine-induced antibodies was tested in cultured-virus-neutralizations, using HCV of genotypes 1–6. sE2-cVLP vaccines induced significantly higher levels of NAbs (p = 0.0065) compared to corresponding sE2 vaccines. Additionally, sE2oligo-cVLP was superior to sE2mono-cVLP in inducing bNAbs. Interestingly, human monoclonal antibody AR2A had reduced binding in ELISA to sE2oligo-cVLP compared with sE2mono-cVLP and competition ELISA using mouse sera from vaccinated animals indicated that sE2oligo-cVLP induced significantly less non-bNAbs AR2A (p = 0.0043) and AR1B (p = 0.017). Thus, cVLP-displayed oligomeric sE2 shows promise as an HCV vaccine candidate.

Hepatitis C virus envelope protein dynamics and the link to hypervariable region 1

Conformational dynamics of viral envelope proteins seem to be involved in mediating evasion from neutralizing antibodies (NAbs) by mechanisms that limit exposure of conserved protein motifs. For hepatitis C virus (HCV), molecular studies have only recently begun to unveil how such dynamics of the envelope protein heterodimer, E1/E2, are linked to viral entry and NAb evasion. Here, we review data suggesting that E1/E2 exists in an equilibrium between theoretical 'open' (NAb-sensitive) and 'closed' (NAb-resistant) conformational states. We describe how this equilibrium is influenced by viral sequence polymorphisms and that it is critically dependent on the N-terminal region of E2, termed hypervariable region 1 (HVR1). Finally, we discuss how it appears that the virus binding site for the HCV entry co-receptor CD81 is less available in 'closed' E1/E2 states and that NAb-resistant viruses require a more intricate entry pathway involving also the entry co-receptor, SR-BI.