Immunogenicity of Leishmania-derived hepatitis B small surface antigen particles exposing highly conserved E2 epitope of hepatitis C virus

Abstract

BackgroundHepatitis C virus (HCV) infection is a major health problem worldwide, affecting an estimated 2–3 % of human population. An HCV vaccine, however, remains unavailable. High viral diversity poses a challenge in developing a vaccine capable of eliciting a broad neutralizing antibody response against all HCV genotypes. The small surface antigen (sHBsAg) of hepatitis B virus (HBV) has the ability to form highly immunogenic subviral particles which are currently used as an efficient anti-HBV vaccine. It also represents an attractive antigen carrier for the delivery of foreign sequences. In the present study, we propose a bivalent vaccine candidate based on novel chimeric particles in which highly conserved epitope of HCV E2 glycoprotein (residues 412–425) was inserted into the hydrophilic loop of sHBsAg.ResultsThe expression of chimeric protein was performed in an unconventional, Leishmania tarentolae expression system resulting in an assembly of particles which retained immunogenicity of both HCV epitope and sHBsAg protein. Direct transmission electron microscopy observation and immunogold staining confirmed the formation of spherical particles approximately 22 nm in diameter, and proper foreign epitope exposition. Furthermore, the sera of mice immunized with chimeric particles proved reactive not only to purified yeast-derived sHBsAg proteins but also HCV E2 412–425 synthetic peptide. Most importantly, they were also able to cross-react with E1E2 complexes from different HCV genotypes.ConclusionsFor the first time, we confirmed successful assembly of chimeric sHBsAg virus-like particles (VLPs) in the L. tarentolae expression system which has the potential to produce high-yields of properly N-glycosylated mammalian proteins. We also proved that chimeric Leishmania-derived VLPs are highly immunogenic and able to elicit cross-reactive antibody response against HCV. This approach may prove useful in the development of a bivalent prophylactic vaccine against HBV and HCV and opens up a new and low-cost opportunity for the production of chimeric sHBsAg VLPs requiring N-glycosylation process for their proper functionality and immunogenicity.

Recombinant Flag-tagged E1E2 glycoproteins from three hepatitis C virus genotypes are biologically functional and elicit cross-reactive neutralizing antibodies in mice

“…In fact, meta-analysis study of HCV experimental vaccinations in chimpanzees demonstrated that vaccine formulations containing structural proteins, were associated with more significant protective immune responses than vaccines based solely on non-structural proteins ( Dahari et al, 2010 ). To date, HCV structural E1 and E2 proteins have been tested as immunogens in variety of modalities including virus-like particles ( Czarnota et al, 2016 , Garrone et al, 2011 ), recombinant proteins ( Freedman et al, 2017 , Grzyb et al, 2016 , Logan et al, 2017 ) and prime-boost regimens with the use of viral vectors ( Chmielewska et al, 2014 , Reyes-del Valle et al, 2012 ). These different strategies were able to raise high-titer cross-neutralizing antibody responses in animals.…”

Specific Antibodies Induced by Immunization with Hepatitis B Virus-Like Particles Carrying Hepatitis C Virus Envelope Glycoprotein 2 Epitopes Show Differential Neutralization Efficiency

“…The particles were produced in a non-conventional, cost-efficient Leishmania tarentolae expression system, purified by ultracentrifugation, and then used to immunize mice. This study is a follow-up of our previously published work in which we described the expression of chimeric sHBsAg particles carrying the highly conserved HCV 412-425 epitope and characterized binding of vaccine-induced antibodies to denatured HCV genotype 1-6 E2 glycoproteins [39]. In this study, we widened the panel of tested HCV E2 epitopes and evaluated the ability of vaccine-induced antibodies to bind native HCV genotype 1-6 E1E2 complexes and their potential to cross-neutralize cell culture infectious HCV (HCVcc) of genotype 1-6.…”

“…Because of its immunogenic potential, sHBsAg has been applied as an antigen carrier to deliver foreign sequences to induce humoral and cellular immune responses [33][34][35][36][37][38]. At the outset of this study, proof-of-concept was obtained that sHBsAg particles could be used as carriers of small HCV epitopes inserted into the antigenic external hydrophilic loop to induce strong and specific antibody responses [38][39][40].…”

“…Additionally, constructs carrying epitope 502-520 had the cysteine residues at positions 503 and 508 substituted with alanine (C503A and C508A). Construction of the chimeric gene coding for construct sHBsAg_412-425 has been described earlier [39].…”

Peer Review #3 of "Application of built-in adjuvants for epitope-based vaccines (v0.1)"

“…The tertiary structure of HBsAg can form a highly conserved hydrophilic loop. Additionally, it has been reported that the existing immunity to HBsAg does not impede the immune response to foreign epitopes carried by HBsAg particles, which is often used as a carrier to insert exogenous antigens into the external hydrophilic loop or the end of the HBsAg N-or C-terminal (Bellier & Klatzmann, 2013 Manuscript to be reviewed system and independently assembled into VLPs, which demonstrated high immunogenicity and induced cross-reactive antibodies against HCV (Czarnota et al, 2016). Wei et al also used HBsAg to display neutralizing HCV epitopes to obtain chimeric HCV-HBV VLPs as a novel strategy for developing a bivalent prophylactic HCV-HBV epitope vaccine (Wei et al, 2018).…”