GSBS Dissertations and Theses

ORCID ID

0000-0001-9321-5921

Publication Date

2017-05-25

Document Type

Doctoral Dissertation

Academic Program

Molecular Genetics and Microbiology

Department

Infectious Diseases and Immunology

First Thesis Advisor

Sanjay Ram

Keywords

monoclonal antibody therapy, mAb, mAb 2C7, chimeric antibody, therapeutic antibody, complement, complement activation, classical complement pathway, phagocytosis, neutrophil opsonophagocytosis, vaccine, engineered antibody, antibody engineering, C1q, C3, gonorrhea, Neisseria gonorrhoeae, vaccines for gonorrhea, treatments for gonorrhea, hexamerizing antibody, hexamerizing IgG, antibody hexamers, IgG hexamers, complement activating antibody, complement activating IgG

Abstract

Neisseria gonorrhoeae (Ng) which causes gonorrhea has become multidrug-resistant, necessitating the development of novel therapeutics and vaccines. mAb 2C7 which targets an epitope within an important virulence factor, the lipooligosaccharide (LOS), is a candidate therapeutic mAb. Ninety-four percent of clinical isolates express the 2C7-epitope which is also a vaccine target.

Ng expresses multiple LOS(s) due to phase-variation (pv) of LOS glycosyltransferase (lgt) genes. mAb 2C7 reactivity requires a lactose extension from the LOS core Heptose (Hep) II (i.e. lgtG ‘ON’ [G+]). Pv results in HepI with: two (2-), three (3-), four (4-), or five (5-) hexoses (Hex). How HepI glycans impact Ng infectivity and mAb 2C7 function are unknown and form the bases of this dissertation.

Using isogenic mutants, I demonstrate that HepI LOS glycans modulate mAb 2C7 binding. mAb 2C7 causes complement (C’)-dependent bacteriolysis of three (2-Hex/G+, 4-Hex/G+, and 5-Hex/G+) of the HepI mutants in vitro. The 3-Hex/G+ mutant (resistant to C’-dependent bacteriolysis) is killed by neutrophils in the presence of mAb and C’. In mice, 2- and 3-Hex/G+ infections are significantly shorter than 4- and 5-Hex/G+ infections. A chimeric mAb 2C7 that hyperactivates C’, attenuates only 4- and 5-Hex/G+ infections.

This study enhances understanding of the role of HepI LOS pv in gonococcal infections and shows that longer HepI glycans are necessary for prolonged infections in vivo. This is the first study that predicts in vitro efficacy of mAb 2C7 against all four targetable HepI glycans thereby strengthening the rationale for development of 2C7-epitope based vaccines and therapeutics.

DOI

10.13028/M2CD5K

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