Hepatitis C virus (HCV) is characterized by a high number of chronic cases owing to an impairment of innate and adaptive immune responses. CD81 on the cell surface facilitates HCV entry by interacting with the E2 envelope glycoprotein. On the other hand, CD81/E2 binding on immune related cells may also influence host response outcome to HCV infection. Here, we performed site-specific amino acid substitution in the front layer of E2 sequence to reduce CD81 binding and evaluate HCV candidate

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... ne potential. The altered sE2 protein (F442NYT), unlike sE2, displayed a significant reduction in CD81 binding, induced pro-inflammatory cytokines, and repressed anti-inflammatory response in primary monocyte-derived macrophages as antigen presenting cells. Further, sE2F442NYT stimulated CD4+T cell proliferation. Immunization of Balb/c mice with an E1/sE2F442NYT RNA-lipid nanoparticle (LNP) displayed improved IgG1 to IgG2a isotype switching, an increase in HCV pseudotype virus neutralizing antibodies, and resistance to challenge infection with a surrogate recombinant vaccinia virus expressing HCV E1-E2-NS2(aa134-966), unlike parental E1/sE2 immunization. Further investigation on modified E2 antigen for selection as antigen may provide helpful information for HCV vaccine development.