Hepatitis C virus modified E2-mRNA-LNP candidate vaccine promotes helper CXCR5T cells.

T cells play an important role in initiating antibody responses by instructive signals of cell-cell contacts and secretion of soluble cytokines as mediators. We investigated the role of the modified soluble E2 (sE2) antigen from hepatitis C virus (HCV) on healthy human peripheral blood mononuclear cell (PBMC)-derived immune cells or immunized mouse cells to understand the mechanisms of immune regulation by the candidate vaccine antigen. HCV E2 and E2 displayed a role in inducing type 17 T-helper cell (Th17) phenotype, as indicated by interleukin-17 (IL-17) expression and signal transducer and activator of transcription 3 (Stat3) phosphorylation. The spleen cells from sE2-mRNA-lipid nanoparticles (LNPs) or sE2-mRNA-LNP-immunized mice exhibited similar IL-17A mRNA levels, and Th17 (CXCR3CCR6) cells in CD4CD44 spleen cells, supporting both sE2 and modified sE2induced Th17 polarization. Immunohistochemical and multiplex immunofluorescence imaging studies revealed abundant CD4CXCR5T cells co-localized with BCL6 in sE2-mRNA-LNP immunized mouse spleen cells than unmodified sE2-mRNA-LNP immunized animals, suggesting sE2 induces stronger follicular helper T cell generation. We previously demonstrated increased total IgG production and isotype switching from IgG1 to IgG2a and IgG2b in sE2 immunized mice. The stronger B and T cell responses observed from modified sE2 support the overall outcome of the study toward a higher B helper T cell generation from sE2-mRNA-LNP immunization as compared to unmodified sE2-mRNA-LNP.IMPORTANCEThe study will help rationalize HCV vaccine antigen selection for an effective immune response. Extension by additional strategies may be useful to direct stronger B helper T cell generation for prolonged vaccine-associated protection.