Hepatitis C virus (HCV) infection is an increasingly larger threat to global health and currently infects approximately 71 million people and causes almost 400,000 deaths each year. The diversity of HCV surpasses that of HIV-1 and this provides a major roadblock for the development of an effective vaccine. Consequently, an HCV vaccine should probably induce broadly neutralizing antibodies (bNAbs) that are capable of targeting and neutralizing most circulating HCV strains.
The E1E2 glycoprotein complex, which is located on the outside of HCV, is the only target for bNAbs. However, soluble E1E2 molecules are difficult to produce and most recombinant HCV glycoproteins vaccines only include the E2 subunit. Furthermore, most HCV glycoprotein vaccines lack any form of multivalent display that could increase B cell activation for improved immunogenicity.
Here, we have developed a recombinant soluble E1E2 (sE1E2) immunogen that could be presented on a computationally designed two-component nanoparticle to enhance its immunogenicity. Conformational anti-E2 bNAbs engaged sE1E2 as efficiently as soluble E2, while sE1E2 also interacted with anti-E1 bNAbs. Furthermore, site-specific glycan analysis revealed that virtually all potential N-glycosylation sites (PNGS) on sE1E2 were occupied by glycans, while E2 monomers contained PNGS that were under-occupied. Nanoparticles were generated by mixing sE1E2 with a second component in vitro and this mix efficiently self-assembled as homogeneous ~40 nm sE1E2-presenting nanoparticles. The sE1E2-nanoparticles exhibited improved binding to several HCV bNAbs. To assess their ability to induce neutralizing antibodies, we immunized rabbits with E2, sE1E2 and sE1E2-nanoparticles and the first results of this immunogenicity study will be presented at the meeting.
This novel sE1E2 immunogen and the two-component nanoparticle platform provide new research avenues for exploring immunization strategies aimed at inducing HCV bNAbs.