Author ORCID Identifier
https://orcid.org/0009-0006-5868-4152
Date of Award
Summer 6-24-2024
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Biomedical Sciences
First Advisor
Cynthia Nau Cornelissen
Second Advisor
Andrew Ted Gewirtz
Third Advisor
Zehava Eichenbaum
Abstract
Gonorrhea poses a significant public health issue due to the lack of immunity post-infection, increasing antibiotic resistance, and the absence of an effective vaccine. This study focuses on the gonococcal TonB-dependent transporter (TdT), TdfH, and its interaction with human calprotectin (hCP), which sequesters essential metals like zinc to inhibit bacterial growth. Findings highlight the critical regions of TdfH involved in zinc acquisition, making them potential targets for therapeutic interventions. TdfH is highly conserved among pathogenic gonococcal strains and surface-exposed, making it a promising vaccine target.
This study found that specific mutations in TdfH affect its ability to bind hCP and facilitate zinc uptake. Mutations in loop 2 inhibited hCP binding and growth significantly when hCP was provided as the only zinc source This suggests that drugs targeting critical hCP binding residues of TdfH could limit bacterial growth and serve as an effective therapeutic strategy. Additionally, investigating the structure and role of the hCP C-terminal tail in interacting with TdfH could reveal new targets for vaccines and therapies. Mutating the hCP tail resulted in the notable outcome that N. gonorrhoeae (Ngo) expressing TdfH failed to grow with or bind to the tailless hCP provided as the zinc source. This underscores the crucial role of the HCP tail in facilitating zinc uptake. In the third phase of the study, evaluations using hybrid antigens fused to a lipoprotein scaffold generated TdfH specific antigens with diverse functional capabilities. Some antibodies against TdfH loops inhibited HCP utilization, indicating a potential therapeutic or preventative mechanism against Ngo infection.
Ultimately, research suggests that interfering with TdTs binding function can effectively starve pathogens. This concept, known as "Starve and Kill," can be demonstrated by applying monoclonal antibodies (mAbs). Developing mAbs to disrupt the ability of TdfH to bind to hCP presents a promising prophylactic approach for gonorrhea treatment and a proof-of-concept for using TdfH as part of a vaccine cocktail. Subsequent studies will test this hypothesis in various mouse models of gonorrhea infection, using human transgenes to produce hCP and other TdTs ligands. These pre-clinical studies will inform the next steps in developing new therapies and vaccines against this challenging human pathogen.
Recommended Citation
Tavakoley Gheinani, Pooneh, "Understand the Binding Interface Between Human Calprotectin and TdfH as a Guide to Effective Preventatives and Therapeutics." Dissertation, Georgia State University, 2024.
https://scholarworks.gsu.edu/biomedical_diss/18