Hepatitis C virus modified sE2_F442NYT as an antigen in candidate vaccine facilitates human immune cell activation

The rational selection of hepatitis C virus (HCV) vaccine antigen will aid in the prevention of future chronic liver disease burden and associated healthcare costs. We have previously shown that HCV E2 glycoprotein is not highly immunogenic, and the modification of E2 reduced CD81 binding and displayed altered cytokine and protective immune responses in vitro and in a surrogate mouse model. Here, we compared the influence of a parental and a modified sE2_F442NYT glycoprotein region from HCV genotype 1a for the activation of peripheral blood mononuclear cell (PBMC)-derived dendritic cells (DCs), CD4⁺T cells, and B cells. Modified sE2_F442NYT, when incubated with DCs, induced a higher number of CD86-positive cells. The sE2_F442NYT or parental sE2 encapsulated as mRNA-lipid nanoparticle (sE2_F442NYT mRNA-LNP) primed DCs co-cultured with autologous CD4⁺T cells did not induce CD25 or forkhead box P3 expression. PBMC-derived CD4⁺T cells treated with sE2_F442NYT exhibited enhanced signal transducer and activator of transcription (Stat)1/Stat4 phosphorylation in response to anti-CD3/CD28 stimulation in comparison to parental sE2 treatment and facilitated isotype switching in B cells, leading to the generation of a broader subclass of antibodies. Cells treated with modified sE2_F442NYT displayed an increase in activated Stat3 and extracellular signal-regulated kinase (ERK). Likewise, PBMC-derived naïve B cells upon in vitro stimulation with sE2_F442NYT induced an increased proliferation, Stat3 and ERK activation, and protein kinase B (Akt) suppression. Thus, the modified sE2_F442NYT antigen from HCV facilitates improved DC, CD4⁺T, and B cell activation compared to parental sE2 to better induce a robust protective immune response, supporting its selection as an HCV candidate vaccine antigen for preclinical and clinical HCV vaccine trials.IMPORTANCEThe nature of an enhanced immune response induced by sE2_F442NYT will help in the selection of a broad cross-protective antigen from hepatitis C virus genotypes, and the inclusion of relatively conserved sE1 with sE2_F442NYT may further strengthen the efficacy of the candidate vaccine in evaluating it for human use.