Characterization of the Humoral Immune Response Elicited Against a Prophylactic Vaccine Composed of Recombinant Envelope Glycoproteins from Hepatitis C Virus

• Author / Creator

  Wong, Jason A.J.

• A global prophylactic vaccine for Hepatitis C Virus (HCV) remains elusive. The diversity of the virus is a major hurdle; a successful vaccine will need to protect against all 7 HCV genotypes (gt). Our lab is developing a vaccine comprising the two envelope glycoproteins of HCV (E1E2). An effective E1E2 vaccine would likely work through generating broadly neutralizing antibodies (nAbs) binding conserved regions on E1E2 critical for entry. An E1E2 vaccine derived from a single gt1a strain (HCV-1) has been shown to elicit broadly nAbs in guinea pigs, chimpanzees, goats, and healthy human volunteers. Epitope mapping of anti-E1E2 antibodies present within antisera from goats/humans immunized with HCV-1 recombinant E1E2 (rE1E2) was conducted through competition studies with monoclonal broadly nAbs targeting various epitopes within E1E2. Antisera were shown to compete with the binding of all broadly nAbs tested and competed especially well with broadly nAbs blocking the interaction between E2 and the major cell entry receptor CD81. Goats immunized with soluble E2 (sE2) derived from either a gt1a (HCV-1) or a gt2a strain (J6) were found to have strong strain-specific nAbs (E2 antisera were not tested for cross-neutralization). HCV-1 rE1E2, HCV-1 sE2, and J6 sE2 antisera were investigated to determine the mechanisms of neutralization. Synchronized time-of-addition experiments revealed that these vaccines elicited nAbs possessing kinetics of neutralization indicating a role early in entry – prior to/at the CD81 post-binding step. Further experiments showed HCV-1 E1E2 and HCV-1 E2 but not J6 E2 goat antisera directly blocked the E2-CD81 interaction. As well, HCV-1 E1E2 and HCV-1 E2 antisera directly blocked the E2-SRB1 interaction (J6 sE2 antisera were not tested). These results suggest that immunizing with HCV envelope glycoproteins elicits nAbs that act at pre-binding and/or early post-binding steps by inhibiting HCV interaction with HSPG, SRB1, and/or CD81. These results support the use of an E1E2 vaccine to induce cross-genotype neutralization. Modified rE1E2 antigens were created to improve vaccine production efficiency, immunoreactivity, and immunogenicity. While improving vaccine production was successful, modifying the antigen was not successful for improving the vaccine in the context of immune responses. However, valuable assays for rational vaccine design were gained and there are other possibilities for generating an optimized vaccine.

• Subjects / Keywords

  • Hepatitis C virus
  • humoral immunity
  • Vaccine

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R39S1M196

• License

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