Defense Date

2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Microbiology & Immunology

First Advisor

Cynthia N. Cornelissen, Ph.D.

Abstract

Neisseria gonorrhoeae, the causative agent of the STI gonorrhea, is not preventable by vaccination and is rapidly developing resistance to antibiotics. One important strategy for gonococcal survival in the host is iron acquisition in the face of nutritional immunity. To overcome iron limitation, the gonococcus expresses TonB dependent transporters (TdTs), outer membrane proteins that facilitate nutrient acquisition. Of the TdTs, the transferrin (Tf), lactoferrin (Lf), and hemoglobin (Hb) receptors hijack iron directly from host proteins, and studies have already shown that the Tf receptor is essential for the initiation of human infection. Given that the TdTs are virulence factors, they are widely conserved across strains, and are not subject to antigenic variation, they are ideal targets for novel therapeutics and vaccine development. As such, studies exploring these proteins and their potential as vaccine candidates and antimicrobial targets are needed. In this study we report that loops of the Tf receptor protein TbpA are not strongly immunogenic, and the antibodies raised against them are incapable of inhibiting TbpA-Tf interactions on the gonococcal cell surface. We also report that the loop 3 helix motif of TbpA is a critical functional domain for Tf-binding and iron uptake; however, no single residue was identified that was essential for these functions. In addition, we report the development of a platform for the structure-function analysis of HpuA, a member of the poorly studied Hb receptor. We also present evidence that novel small molecules may be able to inhibit TbpA-Tf interaction, presenting the Tf receptor as a novel, species-specific antimicrobial target. Finally, we demonstrated that a novel drug, OSU-03012, has antimicrobial activity against the gonococcus through down-regulation of DnaK, a protein chaperone. These findings suggest that DnaK, a widely conserved protein, may be a universal target for antimicrobial development. These studies provide insight into the structure function relationship of TbpA, the drug potential of DnaK, and lay the framework for future investigations of the TdTs for use in a multi-antigen vaccine.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

3-22-2016

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