SELECTION OF VACCINE ANTIGENS FOR PROTECTION FROM HEPATITIS C VIRUS INFECTION

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Abstract Chronic hepatitis C virus (HCV) infection often causes end stage liver disease. Although current anti-HCV drugs are successful in eliminating viral RNA load, they do not prevent reinfection. In addition, eliminating HCV RNA load does not reduce the risk for progression to end stage liver disease. Therefore, the urgent need for the development of a comprehensive strategy to control HCV infection must include a vaccine. HCV envelope glycoproteins are the key components for the initiation of viral infection. Our phase I safety and immunogenicity trial of a recombinant HCV envelope glycoprotein candidate vaccine did not induce a strong immune response in most vaccinated volunteers. Subsequent studies indicated that purified HCV E2 has an immunoregulatory role and biases primary macrophage activation toward the M2 phenotype (via E2-CD81 interactions), impairs DC/CD4+T cell functions, and leads to an environment for a muted response to antigen. Nevertheless, HCV E2 still contains strong cross-genotype specific B- and T-cell epitopes vital to an active immunity. We hypothesize that modifying E2 by discrete point mutations to inhibit interaction with CD81 will improve immune functions and induce robust protective responses in combination with other HCV regions as candidate vaccine, and will generate stronger protective efficacy. Outstanding abilities of nucleoside modified mRNA-lipid nanoparticle (LNP) to elicit potent immune responses against pathogens makes it a viable new cost-effective platform for vaccine development. The incorporation of modified nucleosides in the mRNA will offer advantages for generation of modified antigens to induce a broad effective immune response. The premise and rigor of the study stems from our own work, and information in the literature. Thus, the use of nanoparticle encapsulated mRNA of modified E2 for stronger immunogenicity together with other viral antigens (E1 and non-structural (NS) genomic regions) for prime and boost with proteins/peptides as a candidate vaccine for HCV cross protective efficacy will generate robust B- and T- cell responses for protection against HCV. The results from our study will advance vaccine development against persistent HCV infection.