Uropathogenic Escherichia coli Induces Serum Amyloid A in Mice following Urinary Tract and Systemic Inoculation

Serum amyloid A (SAA) is an acute phase protein involved in the homeostasis of inflammatory responses and appears to be a vital host defense component with protective anti-infective properties. SAA expression remains poorly defined in many tissues, including the urinary tract which often faces bacterial challenge. Urinary tract infections (UTIs) are usually caused by strains of uropathogenic Escherichia coli (UPEC) and frequently occur among otherwise healthy individuals, many of whom experience bouts of recurrent and relapsing infections despite the use of antibiotics. To date, whether SAA is present in the infected urothelium and whether or not the induction of SAA can protect the host against UPEC is unclear. Here we show, using mouse models coupled with immunofluorescence microscopy and quantitative RT-PCR, that delivery of UPEC either directly into the urinary tract via catheterization or systemically via intraperitoneal injection triggers the expression of SAA. As measured by ELISA, serum levels of SAA1/2 were also transiently elevated in response to UTI, but circulating SAA3 levels were only up-regulated substantially following intraperitoneal inoculation of UPEC. In in vitro assays, physiological relevant levels of SAA1/2 did not affect the growth or viability of UPEC, but were able to block biofilm formation by the uropathogens. We suggest that SAA functions as a critical host defense against UTIs, preventing the formation of biofilms both upon and within the urothelium and possibly providing clinicians with a sensitive serological marker for UTI

Identification of the long, edited dsRNAome of LPS-stimulated immune cells

Endogenous double-stranded RNA (dsRNA) must be intricately regulated in mammals to prevent aberrant activation of host inflammatory pathways by cytosolic dsRNA binding proteins. Here, we define the long, endogenous dsRNA repertoire in mammalian macrophages and monocytes during the inflammatory response to bacterial lipopolysaccharide. Hyperediting by adenosine deaminases that act on RNA (ADAR) enzymes was quantified over time using RNA-seq data from activated mouse macrophages to identify 342 Editing Enriched Regions (EERs), indicative of highly structured dsRNA. Analysis of publicly available data sets for samples of human peripheral blood monocytes resulted in discovery of 3438 EERs in the human transcriptome. Human EERs had predicted secondary structures that were significantly more stable than those of mouse EERs and were located primarily in introns, whereas nearly all mouse EERs were in 3′ UTRs. Seventy-four mouse EER-associated genes contained an EER in the orthologous human gene, although nucleotide sequence and position were only rarely conserved. Among these conserved EER-associated genes were several TNF alpha-signaling genes, including Sppl2a and Tnfrsf1b, important for processing and recognition of TNF alpha, respectively. Using publicly available data and experimental validation, we found that a significant proportion of EERs accumulated in the nucleus, a strategy that may prevent aberrant activation of proinflammatory cascades in the cytoplasm. The observation of many ADAR-edited dsRNAs in mammalian immune cells, a subset of which are in orthologous genes of mouse and human, suggests a conserved role for these structured regions.</jats:p

Forced resurgence and targeting of intracellular uropathogenic Escherichia coli reservoirs.

Intracellular quiescent reservoirs of uropathogenic Escherichia coli (UPEC), which can seed the bladder mucosa during the acute phase of a urinary tract infection (UTI), are protected from antibiotic treatments and are extremely difficult to eliminate. These reservoirs are a potential source for recurrent UTIs that affect millions annually. Here, using murine infection models and the bladder cell exfoliant chitosan, we demonstrate that intracellular UPEC populations shift within the stratified layers of the urothelium during the course of a UTI. Following invasion of the terminally differentiated superficial layer of epithelial cells that line the bladder lumen, UPEC can multiply and disseminate, eventually establishing reservoirs within underlying immature host cells. If given access, UPEC can invade the superficial and immature bladder cells equally well. As infected immature host cells differentiate and migrate towards the apical surface of the bladder, UPEC can reinitiate growth and discharge into the bladder lumen. By inducing the exfoliation of the superficial layers of the urothelium, chitosan stimulates rapid regenerative processes and the reactivation and efflux of quiescent intracellular UPEC reservoirs. When combined with antibiotics, chitosan treatment significantly reduces bacterial loads within the bladder and may therefore be of therapeutic value to individuals with chronic, recurrent UTIs

Conidial surface proteins have many roles.

Proteins on the surface of conidia are involved in a variety of important functions. In particular, these proteins contribute to germination, stress resistance, adhesion to substrates, and virulence.</p

Host-derived extracellular vesicles for antimicrobial defense

ABSTRACT Extracellular vesicles are of increasing importance in the clinic, as diagnostics for complex diseases and as potential delivery systems for therapeutics. Over the past several decades, extracellular vesicles have emerged as a widespread, conserved mechanism of intercellular and interkingdom communication. The ubiquitous distribution of extracellular vesicles across life offers at least two compelling opportunities: first a path forward in the design of targeted antimicrobial delivery systems; and second, a new way to view host pathogenesis during infection. Both avenues of research are well underway. In particular, preliminary studies showing that plant and human host-derived extracellular vesicles can deliver natural antimicrobial cargos to invading fungal and bacterial pathogens are captivating. Further, modification of host extracellular vesicle populations may ultimately lead to enhanced killing and serve as a starting point for the development of more advanced therapeutic options, especially against difficult to treat pathogens. Despite the rapid pace of growth surrounding extracellular vesicle biology, many questions remain unanswered. For example, the heterogeneity of vesicle populations continues to be a confounding factor in ascribing clear functions to a vesicular subset, and the molecular cargos responsible for specific antimicrobial actions of extracellular vesicles during infection remain especially poorly described. In this short review, we will summarize the current state of affairs surrounding the antimicrobial function, and potential, of host-derived extracellular vesicles.</jats:p