Identification of a novel epitope in the C terminus of hepatitis C virus-E2 protein that induces potent and cross-reactive neutralizing antibodies

Development of an effective single-chain variable fragment recognizing a novel epitope in the hepatitis C virus E2 protein that restricts virus entry into hepatocytes

Previously, we reported a neutralizing monoclonal antibody, A8A11, raised against a novel conserved epitope within the hepatitis C virus (HCV) E2 protein, that could significantly reduce HCV replication. Here, we report the nucleotide sequence of A8A11 and demonstrate the efficacy of a single-chain variable fragment (scFv) protein that mimics the antibody, inhibits the binding of an HCV virus-like particle to hepatocytes, and reduces viral RNA replication in a cell culture system. More importantly, scFv A8A11 was found to effectively restrict the increase of viral RNA levels in the serum of HCV-infected chimeric mice harbouring human hepatocytes. These results suggest a promising approach to neutralizing-antibody-based therapeutic interventions against HCV infection.

Characterization of linear epitope specificity of antibodies potentially contributing to spontaneous clearance of hepatitis C virus

Background

Around 30% of the HCV infected patients can spontaneously clear the virus. Cumulative evidence suggests the role of neutralizing antibodies in such spontaneous resolution. Understanding the epitope specificity of such antibodies will inform the rational vaccine design as such information is limited to date. In addition to conformational epitope targeted antibodies, linear epitope specific antibodies have been identified that are broadly cross reactive against diverse HCV strains. In this study, we have characterized the potential role of three conserved linear epitopes in the spontaneous clearance of HCV.

Methods

We tested the reactivity of sera from chronic patients (CP) and spontaneous resolvers (SR) with linear peptides corresponding to three conserved regions of HCV envelope protein E2 spanning amino acids 412–423, 523–532 and 432–443 using ELISA. Subsequently, we characterized the dependency of HCV neutralization by the reactive serum samples on the antibodies specific for these epitopes using pseudoparticle-based neutralization assay.

In ELISA most of the CP sera showed reactivity to multiple peptides while most of the SR samples were reactive to a single peptide suggesting presence of more specific antibodies in the SR sera. In most of the HCVpp neutralizing sera of particular peptide reactivity the neutralization was significantly affected by the presence of respective peptide. HCV neutralization by CP sera was affected by multiple peptides while 75% of the HCVpp neutralizing SR sera were competed by the 432 epitope.

Conclusions

These findings suggest that individuals who spontaneously resolve HCV infection at the acute phase, can produce antibodies specific for conserved linear epitopes, and those antibodies can potentially play a role in the spontaneous viral clearance. The epitope present in the 432–443 region of E2 was identified as the primary neutralizing epitope with potential role in spontaneous viral clearance and this epitope potentiates for the design of immunogen for prophylactic vaccine.

A trivalent HCV vaccine elicits broad and synergistic polyclonal antibody response in mice and rhesus monkey

OBJECTIVE

Despite the development of highly effective direct-acting antivirals, a prophylactic vaccine is needed for eradicating HCV. A major hurdle of HCV vaccine development is to induce immunity against HCV with high genome diversity. We previously demonstrated that a soluble E2 (sE2) expressed from insect cells induces broadly neutralising antibodies (NAbs) and prevents HCV infection. The objective of this study is to develop a multivalent HCV vaccine to increase the antigenic coverage.

DESIGN

We designed a trivalent vaccine containing sE2 from genotype 1a, 1b and 3a. Mice and rhesus macaques were immunised with monovalent or trivalent sE2 vaccine, and sera or purified immunoglobulin were assessed for neutralisation against a panel of cell culture-derived virion (HCVcc) of genotype 1-7 in cell culture. Splenocytes from the vaccinated macaques were assessed for HCV-specific T cell response.

RESULTS

We showed that the trivalent vaccine elicited pangenotypic NAbs in mice, which neutralised HCVcc of all the seven genotypes more potently than the monovalent vaccine. Further analyses demonstrated that each sE2 component of this trivalent vaccine elicited unique spectrum of NAbs which acted synergistically to inhibit HCV infection. Finally, the trivalent vaccine triggered stronger and more uniform multigenotypic neutralising antibody response than the monovalent vaccine in rhesus macaques.

CONCLUSIONS

In summary, we developed a trivalent HCV vaccine that induces broad and synergistic-acting neutralising antibodies in mice and non-human primates.

Novel adeno‑associated virus‑based genetic vaccines encoding hepatitis C virus E2 glycoprotein elicit humoral immune responses in mice

Hepatitis C virus (HCV) infection remains a major public health issue despite the introduction of several direct-acting antiviral agents (DAAs), with some 185 million individuals infected with HCV worldwide. There is an urgent need for an effective prophylactic HCV vaccine. In the present study, we constructed genetic vaccines based on novel recombinant adeno-associated viral (rAAV) vectors (AAV2/8 or AAV2/rh32.33) that express the envelope glycoprotein E2 from the HCV genotype 1b. Expression of HCV E2 protein in 293 cells was confirmed by western blot analysis. rAAV2/8.HCV E2 vaccine or rAAV2/rh32.33.HCV E2 vaccine was intramuscularly injected into C57BL/6 mice. HCV E2-specific antigen was produced, and long-lasting specific antibody responses remained detectable XVI weeks following immunization. In addition, the rAAV2/rh32.33 vaccine induced higher antigen-specific antibody levels than the rAAV2/8 vaccine or AAV plasmid. Moreover, both AAV vaccines induced neutralizing antibodies against HCV genotypes 1a and 1b. Finally, it is worth mentioning that neutralizing antibody levels directed against AAV2/rh32.33 were lower than those against AAV2/8 in both mouse and human serum. These results demonstrate that AAV vectors, especially the AAVrh32.33, have particularly favorable immunogenicity for development into an effective HCV vaccine.