Investigation of the Molecular Mechanisms That Determine Isolate-Specific, Antibody-Mediated Neutralization of HCV infectivity

  • Author / Creator
    Johnson, Janelle L
  • It is estimated that there are about 1.75 million new Hepatitis C Virus (HCV) infections per year worldwide and around 20% will develop liver cirrhosis or liver cancer if left untreated. Direct acting antiviral drugs are available for the treatment of HCV with success rates of over 90%. But these treatments are expensive and cured patients can still be reinfected. To eliminate HCV, a prophylactic vaccine is needed. One of the major challenges in the development of a vaccine is the genetic diversity of the virus. Currently, there are 7 major genotypes and hundreds of subtypes. A global vaccine needs to be effective against all HCV genotypes. Our laboratory is developing an adjuvanted vaccine comprising recombinant E1/E2 viral envelope glycoprotein and non-structural protein components designed to elicit cross-neutralizing antibodies along with broad cross-reactive T cell responses against HCV. Previous data shows that the 1a E1/E2 glycoprotein component can elicit broad cross-neutralizing antibodies in humans and animals. However, variation is seen in the effectiveness of these antibodies to neutralize different HCV genotypes. The 1a E1/E2 vaccine-induced antisera showed strong homologous neutralization activity against genotype 1a H77c virus, while exhibiting significant differences in neutralizing activity against two closely related isolates of HCV genotype 2a, the J6 and JFH-1 strains. E1 and E2 glycoprotein domains were swapped between the resistant J6 and sensitive JFH strains to determine the location of this differential neutralization sensitivity. Exchanges of variant amino acids in the E2 glycoprotein of these two HCV genotype 2a viruses were then conducted systematically to determine if specific amino acids were important for conferring this differential neutralization sensitivity. In addition, the role of the N-terminal hypervariable region 1 (HVR1) of the E2 protein was investigated as a determinant of this isolate-specific neutralization. Recombinant J6 viruses with the HVR1 deleted or replaced with HVR1 from JFH-1, 1a H77 or 3a S52 were created. These recombinant viruses were then tested for their neutralization sensitivity to 1a E1/E2 antisera and to broadly neutralizing monoclonal antibodies. The role of the HVR1 in interaction with the entry receptors cluster of differentiation 81 (CD81) and scavenger receptor class B type 1 (SR-B1) was also investigated. While HVR1 was shown to be mediating this isolate-specific neutralization, interestingly, our vaccine antisera does not appear to target the HVR1 of either of the genotype 2a viruses implying that HVR1 has an indirect effect. Other data indicates that HVR1 is mediating exposure of antibody binding sites of broadly neutralizing monoclonal antibodies. Additionally, HVR1 is not directly impacting the CD81 binding domain, but mediates isolate specific interactions with the SRB1 receptor. Together, my data provides new information on the mechanisms of differential neutralization and contributes towards the design of a better vaccine antigen or antigen cocktail capable of expanding and optimizing the breadth of cross-genotype protection.

  • Subjects / Keywords
  • Graduation date
    Fall 2018
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
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