Author ORCID Identifier

https://orcid.org/0000-0002-1847-5712

Defense Date

2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Microbiology & Immunology

First Advisor

Richard T Marconi

Abstract

Leptospirosis is the most widespread zoonosis, affecting over 1 million humans each year, resulting in more than 60,000 deaths. Furthermore, leptospirosis impacts canines, cattle, and other domesticated animals, resulting in significant financial and health burdens. Disease may be self-limiting or progress to a life-threatening multi-system disorder affecting the kidneys, liver, and lungs. The incidence of canine and human leptospirosis has been steadily increasing worldwide. Currently, bacterin formulations consisting of a mixture of laboratory cultivated strains of locally-relevant Leptospira serotypes represent the only preventative tool for veterinary and limited human applications. The antibody response to Leptospira bacterin vaccines is serovar-specific and directed primarily at the lipopolysaccharide; however, over twenty pathogenic species of Leptospira have been identified, further classified into over 300 serovars, limiting their efficacy. To date, no subunit vaccines have been licensed to prevent leptospirosis. Developing a broadly protective subunit vaccine for veterinary or human application would represent a significant step forward in combating this emerging disease.

Herein we investigated a panel of Leptospira outer membrane proteins as vaccine targets. Immunization of rats with select r-proteins elicited bactericidal antibodies against heterologous Leptospira, the most potent being anti-Loa22, anti-LigANI, anti-LigBn, and anti-GspD antisera. Immunogenic regions of these four r-proteins were identified by ELISA and confirmed by bactericidal antibody r-protein blocking assay. Epitope mapping localized the bactericidal epitopes of rLigANI and rLigBn to the central regions, and rLoa22 and rGspD to the N-termini. Nucleotide sequences of the epitope-containing regions were subsequently synthesized as one gene, in varying iterations, to generate chimeric epitope-based constructs. Hyperimmune sera against each of the four recombinant chimeritope constructs were bactericidal in vitro against diverse Leptospira. Furthermore, vaccination with the rLCV_BLAG chimeritope, in particular, conferred protective immunity against lethal challenge with the homologous isolate in a hamster model of acute leptospirosis. These data are among the first to establish the correlation of in vitro bactericidal activity with in vivo protective efficacy for Leptospira. This study demonstrated the utility of antigenic rLigANI, rLigBn, rLoa22, and rGspD subfragments as components of a chimeritope subunit vaccine for the prevention of leptospirosis.

Rights

© Edward JA Schuler

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

11-10-2022

Available for download on Monday, September 23, 2222

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