Date of Award

2019

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Biological Sciences (PhD)

Administrative Home Department

Department of Biological Sciences

Advisor 1

Ebenezer Tumban

Committee Member 1

Stephen M. Techtmann

Committee Member 2

Xiaoqing Tang

Committee Member 3

Hairong Wei

Abstract

Current human papillomavirus (HPV) vaccines (Cervarix and Gardasil-9) are highly immunogenic and derived from the major capsid proteins (L1) of different HPV types. L1 is not conserved among different HPV types. Thus, these L1-based vaccines protect mostly against the HPV types included in the vaccines with minimal cross-protection against non-vaccine HPV types. In addition to this, the vaccines require refrigeration during transportation and storage. To broaden protection against diverse HPV infection, we targeted epitopes (17-31, 69-86, and 108-122) on the major capsid protein (L2) of HPV, which are conserved among different HPV types for vaccine design. We explored the display of these L2 epitopes, individually or as concatemers, on the surface of a highly immunogenic bacteriophage MS2 virus-like particle (VLP) platform. VLPs are empty viral shells without a viral genome. They are derived from viral structural proteins such as envelope proteins or capsid proteins. VLPs cannot replicate, they are non-infectious, and are highly immunogenic; thus, they are safe and effective platforms for vaccine designs. Mice immunized with the MS2-L2 candidate HPV vaccine (a mixture of MS2 VLPs: one displaying a concatemer of peptides from HPV16L2 & HPV31L2 and the other displaying a consensus peptide, epitope 69-86, from the alignment of 23 HPV types) elicited high-titer antibodies that protected mice from genital infection with nine diverse HPV types; the VLPs also protected mice from oral infection with five diverse HPV types. To improve the thermostability of the MS2-L2 VLPs, the candidate vaccine was formulated into powder by spray-freeze drying technique. Spray-freeze dried VLPs stored at room temperature for two months were still immunogenic and offered protection against HPV infection. Mixed MS2-L2 VLPs is a candidate next-generation HPV vaccine. We also explored, in this dissertation, the potential of developing a novel thermostable VLP platform based on a thermophilic bacteriophage, FIN93. Our results seem to suggest that co-expression of two truncated versions of coat proteins from FIN93 have potential to form structures that resemble VLPs.

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