Lyme disease (LD) is the most prevalent vector borne disease is North America with 300,000-600,000 human cases each year. Preventative strategies for LD in humans are poorly developed and largely inadequate. While preventive vaccines for LD are widely used in veterinary medicine, there are no vaccines available for use in humans. The goal of this study was to develop a human vaccine that can elicit antibody responses that kill spirochetes in both the tick and mammalian environments. The approach applied in this study centered on the development of chimeric epitope proteins, referred to as chimeritopes. Chimeritopes consist of a series of epitopes derived from one or more proteins or protein variants. Three chimeritope proteins designated as Chv1, Chv2 and Chv3 were designed. These proteins harbor the same set of 18 linear epitopes derived from 9 different OspC type proteins. They differ in epitope arrangement or by the presence or absence of linkers between specific protein segments. The immunogenicity of each protein was assessed in multiple animal models including mice, rats, and purpose bred beagles. Immunoblot, ELISA, and IFA analyses using sera from immunized animals demonstrated that the Chv proteins elicit IgG responses that recognize a diverse array of OspC type proteins. Anti-Chv and anti-OspA antisera displayed complement dependent bactericidal activity. To assess protective efficacy, purpose bred beagles were immunized with each vaccine formulation and then challenged by infestation with infected ticks. Efficacy was assessed by monitoring seroconversion, cultivation of tissue biopsies, clinical presentation and histopathological analysis of joints and tissues. All dogs vaccinated with the Chv2-OspA combination were fully protected. All dogs in this group were seronegative for LD, biopsy culture negative and did not develop LD associated symptoms including lameness or lesions in tissues or joints. In light of market concerns centered on the use of full length OspA in a human vaccine, epitope mapping was performed to identify a linear epitope that could be employed in development of a possible OspC-OspA chimeritope. A linear epitope, designated as OspA221-240was identified. Antisera to KLH-OspA221-240displayed potent and broad bactericidal activity. Interestingly, the OspA221-240epitope has homology to residues 244 to 263 of OspB suggesting that OspB may also be a potential candidate for inclusion in a human vaccine. This study establishes proof of principle for the use of OspC chimeritopes in LD subunit vaccines and highlights the need to employ a multi-valent, multi-antigen vaccine approach in development of a human LD vaccine.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-7048 |
| Date | 01 January 2019 |
| Creators | Izac, Jerilyn R |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © Jerilyn R. Izac |
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