Projects
Urinary tract infections (UTI), including cystitis and pyelonephritis, are most commonly caused by uropathogenic strains of Escherichia coli (UPEC). Recent work has unveiled new paradigms regarding the pathogenesis of UTI. Long thought to be a strictly extracellular pathogen, UPEC has been shown to invade the epithelial cells lining the bladder and to establish large collections, termed intracellular bacterial communities (IBCs), within the superficial epithelial cells. From there, UPEC proceeds to form a reservoir within bladder tissue that is quiescent and invisible to host immune defenses. This reservoir can then serve as a seed for recurrent infection, a finding that challenges current dogma that recurrent UTI represents re-inoculation of the urinary tract from a gastrointestinal E. coli population. Our studies have identified an anti-inflammatory phenotype unique to uropathogenic strains of E. coli that may facilitate the initial steps of the IBC pathway and support the ability of UPEC to persist in the bladder tissue undetected by host immune mechanisms. Our current goals are to delineate the steps of host cell inflammatory signaling that are interrupted by UPEC, and to identify the genetic determinants of this virulence attribute in our prototypic cystitis strain, UTI89.
Integral outer membrane proteins that underlie virulence of E. coli
UPEC and other Gram-negative pathogens have evolved a number of 
systems to sense and deal with stress in the periplasm, which may result from environmental conditions (temperature, pH, osmolarity, etc.) or from internal conditions (e.g., misfolded protein in the periplasmic space). Included among periplasmic folding factors, or chaperones, are the peptidyl-prolyl isomerases (PPIases), three related families of proteins in eukaryotes and prokaryotes that catalyze the cis-trans conversion of peptidyl proline bonds. We are currently studying the mechanisms by which an important periplasmic chaperone, called SurA, interacts with nascent polypeptides destined for outer membrane insertion. We have also demonstrated that multiple SurA-dependent UPEC integral outer membrane proteins, such as FimD and OmpA, are required for the initiation of bacterial cystitis. We are currently investigating how OmpA contributes to the formation of intracellular bacterial communities and mediates UPEC resistance to host immune responses. Our hope is to discover new molecular targets for therapy and prevention of these very prevalent infections.
Interaction of E. coli with human polymorphonuclear leukocytes
Neutrophils arriving in the bladder in response to chemokines interact directly with E. coli bacteria and with IBC-containing superficial bladder epithelial cells to control initial infection in the murine cystitis model. Despite the arrival of neutrophils, UPEC can multiply to high titers in the mouse bladder by 48 hours after infection. We hypothesize that UPEC, relative to E. coli K-12, employs strategies to resist phagocytosis, survive within phagocytes, and/or affect the generation of reactive oxygen species within neutrophils. Current projects aim to determine the ability of neutrophils to ingest and kill UPEC relative to E. coli K-12 and to quantify the generation of reactive oxygen species within neutrophils exposed to these strains. In addition, we have detailed host-pathogen crosstalk by profiling bacterial and eukaryotic gene expression during phagocytosis of UPEC by human neutrophils. These transcriptional profiles offer new leads for investigation of bacterial effector proteins and the host pathways that they modulate.
Adhesin-conjugated nanotherapeutics for urinary tract infection
We aim to leverage recent discoveries about the pathogenic cascade of cystitis in developing novel therapeutic interventions for UTI. Specifically, oral antibiotic therapy fails to eradicate the intraepithelial reservoir which can serve as a seed for recurrences of UTI. In a collaboration with Dr. Karen Wooley, polymer chemist at Texas A&M University, we are developing antimicrobial-bearing nanoparticles (NPs) conjugated with the UPEC type 1 pilus adhesin, FimH. Adhesin interaction with the bladder epithelial surface will direct internalization of the NPs, where their antimicrobial "cargo" can be deployed against reservoir bacteria. The technology also has potential utility in prevention of UTI in special populations (e.g., ICU patients with indwelling urinary catheters).