Association of O-Antigen Serotype with the Magnitude of Initial Systemic Cytokine Responses and Persistence in the Urinary Tract

Abstract

Urinary tract infection (UTI) is one of the most common ailments requiring both short-term and prophylactic antibiotic therapies. Progression of infection from the bladder to the kidney is associated with more severe clinical symptoms (e.g., fever and vomiting) as well as with dangerous disease sequelae (e.g., renal scaring and sepsis). Host-pathogen interactions that promote bacterial ascent to the kidney are not completely understood. Prior studies indicate that the magnitude of proinflammatory cytokine elicitation in vitro by clinical isolates of uropathogenic Escherichia coli (UPEC) inversely correlates with the severity of clinical disease. Therefore, we hypothesize that the magnitude of initial proinflammatory responses during infection defines the course and severity of disease. Clinical UPEC isolates obtained from patients with a nonfebrile UTI elicited high systemic proinflammatory responses early during experimental UTI in a murine model and were attenuated in bladder and kidney persistence. Conversely, UPEC isolates obtained from patients with febrile UTI elicited low systemic proinflammatory responses early during experimental UTI and exhibited prolonged persistence in the bladder and kidney. Soluble factors in the supernatant from saturated cultures as well as the lipopolysaccharide (LPS) serotype correlated with the magnitude of proinflammatory responses in vitro. Our data suggest that the structure of the O-antigen sugar moiety of the LPS may determine the strength of cytokine induction by epithelial cells. Moreover, the course and severity of disease appear to be the consequence of the magnitude of initial cytokines produced by the bladder epithelium during infection. IMPORTANCEThe specific host-pathogen interactions that determine the extent and course of disease are not completely understood. Our studies demonstrate that modest changes in the magnitude of cytokine production observed using in vitro models of infection translate into significant ramifications for bacterial persistence and disease severity. While many studies have demonstrated that modifications of the LPS lipid A moiety modulate the extent of Toll-like receptor 4 (TLR4) activation, our studies implicate the O-antigen sugar moiety as another potential rheostat for the modulation of proinflammatory cytokine production. The plasticity of the Escherichia coli genome has led to the evolution of strains that can serve as keystone commensal organisms in the microbiota as well as to the development of multiple virulent pathotypes that cause both intestinal and extraintestinal infections. Comparison of the genetic content of over 180 strains has revealed that the core E. coli genome is composed of about 1,700 genes, with an additional pangenome of over 16,000 genes (1). It has become increasingly apparent that the plasticity of the E. coli genome allows acquisition of virulence traits from diverse genetic origins and, as such, the potential to attain the same phenotypic trait using different mechanisms (2). Given this vast variat...

Urine Cytokine and Chemokine Levels Predict Urinary Tract Infection Severity Independent of Uropathogen, Urine Bacterial Burden, Host Genetics, and Host Age

“…S3 in the supplemental material and C57BL/6 mice from the experiment shown in Fig. S4 were (Continued on next page) (44). Additional factors produced during UTI that recruit and activate neutrophils and regulate antibacterial defenses include CCL2 (MCP-1), CCL5 (RANTES), TNF-␣, and IFN-␥ (22,(25)(26)(27)(28).…”

“…Thus, our predictive model for disease severity predominately relates to cytokines and chemokines involved in neutrophil and monocyte recruitment to the site of infection. Prior studies in young mice have shown that inoculation with E. coli induces TNF-␣, IL-1␤, IL-6, IL-10, IL-17, KC (CXCL1), RANTES (CCL5), LIX (CXCL5), and IFN-␥ during the course of infection (28,(44)(45)(46), and inoculation with P. mirabilis induces CCL2 (MCP-1), RANTES, KC, IL-6, IL-10, IL-17A, IL-1␤, TNF-␣, and IFN-␥ (33). Our cytokine and chemokine data are in agreement with these studies and uncovered differences in urine levels of IL-1␤, IFN-␤, CCL5 (RANTES), CXCL5 (LIX), and CCL2 (MCP-1) upon direct comparison of E. coli UTI to P. mirabilis UTI across the entire cohort of mice.…”

“…Most importantly, several of the cytokines and chemokines produced in response to experimental UTI in mice have also been reported as induced during both human UTI and in vitro stimulation of human bladder urothelial cells, including IL-1␤, IL-6, IL-8 (or the murine functional homologs CXCL1 [KC] and CXCL5 [LIX]), IL-10, and CCL5 (RANTES) (34,39,44,(50)(51)(52)(53)(54). The timing and magnitude of production of the immunomodulatory protein IL-10 in response to E. coli infection appear to contribute to colonization of the urinary tract in a murine infection model and during human UTI (28), indicating that age-related changes in IL-10 production during urine colonization could have a dramatic impact on colonization susceptibility and disease severity.…”

Granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) is released by female mouse bladder urothelial cells and expressed by the urothelium as an early response to lipopolysaccharides (LPS)

“…LPS from E. coli O111:B4 has been used in numerous studies for surrogate of infectious pathogenesis in the murine host (e.g., systemic inflammatory response syndrome or sepsis). It is recognized that LPS O‐antigen loci from different uropathogenic E. coli strains impact the immune response of the host . Whether a different type of LPS might induce a different GM‐CSF response (e.g., a persistent response, no response, higher intensity response, etc.)…”

“…It is recognized that LPS O-antigen loci from different uropathogenic E. coli strains impact the immune response of the host. 26 Whether a different type of LPS might induce a different GM-CSF response (e.g., a persistent response, no response, higher intensity response, etc.) in urothelial cells is unknown.…”