Derek Cheung, Memorial University of Newfoundland

D. Cheung, L. Curnew, J. Law Memorial University of Newfoundland

Discovering & Evolving

An effective vaccine against hepatitis C virus(HCV) remains an unmet medical need. The viral glycoproteins E1E2 mediate receptor-dependent entry and are the principal antigenic target of neutralizing antibodies. Clinical studies have shown that broadly neutralizing antibodies correlate with spontaneous HCV clearance, yet early vaccine studies failed to provide broad protection across diverse strains. HCV is classified into eight major genotypes by phylogenetic analysis, but neutralization sensitivity segregates into six clusters that do not mirror glycoprotein sequence similarity(Banwitz et al.,Gut,2021). The determinants of this neutralization sensitivity remain poorly defined. Hypervariable region 1(HVR1) at the amino-terminus of E2 can modulate genotype-specific neutralization, consistent with allosteric regulation of the E1E2. We hypothesize that E1E2 conformation governs both neutralization sensitivity and immunogenicity. To test this, we selected six E2 isolates representing all neutralization clusters(Con1[Group 1], 2r[Group 2], 2a3[Group 3], H77 and J4[Group 4], SA13[Group 5] and J6[Group 6]). Recombinant E2 proteins were expressed in mammalian cells and validated for proper folding by ELISA using conformation-specific monoclonal antibodies and E1E2 protein–induced goat antiserum, and the corresponding HCVcc were used to assess neutralization profiles. Preliminary data indicate these E2 glycoproteins are similarly recognized by ELISA, whereas recombinant viruses bearing the same E1E2 isolates exhibit markedly different neutralization sensitivities, suggesting masking of neutralizing epitopes on the virion. Ongoing studies are dissecting how epitope masking and conformational features of E1E2 regulate neutralization sensitivity across HCV isolates. Ultimately, this work aims to define the relationship between neutralization sensitivity and the immunogenicity of HCV glycoproteins to inform next-generation-vaccine design.