Structure-based design of an epitope-focused Hepatitis C virus vaccine

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An estimated 170 million people worldwide are infected with the hepatitis C virus (HCV), and chronic HCV infection is a major cause of liver cirrhosis and liver cancer. The direct-acting antivirals against HCV reach impressive cure rates; however, their high-costs and the emergence of drug-resistant viruses reinforce the urgent need to develop a safe and efficient HCV vaccine. Recent evidence has highlighted the role of neutralizing antibodies (nAbs) in protection from persistent HCV infection. Structural studies of nAb fragments in complex with epitope peptides or HCV glycoprotein E2 have provided the foundation to enable rational vaccine design strategies. The majority of nAbs target the receptor-binding site (CD81) within E2, but the virus has developed a number of mechanisms to evade the neutralizing antibody response that preclude E2 from being an efficient immunogen, such as an extensive glycan shield, immunodominant "decoy" epitopes and a pronounced conformational flexibility. Novel computational design methodologies used for immunogen optimization have paved the way for structure-based vaccine design. These novel approaches allow for the transplantation of specific epitopes to scaffold proteins to focus the antibody response on important neutralization epitopes.The goal of this project is to leverage these novel computational methods to design epitope-focused immunogens that enhance the elicitation of HCV neutralizing antibodies. We will transplant neutralization epitopes from the HCV glycoproteins E1 and E2 (one and four epitopes, respectively), including linear and conformational epitopes as two distinct strategic opportunities. For each of these epitopes, epitope-focused immunogens will be computationally designed and experimentally tested. The most promising candidates will be biophysically, biochemically and structurally characterized; we will subsequently select immunogens with the desired biochemical profile and test their ability to induce a specific antibody response in mice. We will determine the capacity of post-immunization sera to bind E2 and more importantly, assess neutralizing and cross-neutralizing activity. We will investigate the induced antibody responses at the monoclonal level by isolating antigen-specific memory B cells, to characterize the elicited antibodies both structurally and functionally.The proposed project will provide a novel approach for structure-based design of an efficient HCV vaccine. In addition, as structural data on neutralization epitopes within HCV glycoproteins are scarce, co-crystallization of novel immunogens with well-characterized antibody fragments targeting the displayed epitopes will greatly increase our understanding of the interactions between the humoral immune system and the HCV glycoproteins. The strategies developed with this project may also be useful to design optimized immunogens for other infectious diseases that lack efficacious vaccines, such as HIV, Influenza, or malaria.