Augmentation of Urinary Lactoferrin Enhances Host Innate Immune Clearance of Uropathogenic Escherichia coli

Progress toward a vaccine for extraintestinal pathogenic E. coli (ExPEC) II: efficacy of a toxin-autotransporter dual antigen approach

Extraintestinal pathogenic Escherichia coli (ExPEC) is a leading cause of worldwide morbidity and mortality, the top cause of antimicrobial-resistant (AMR) infections, and the most frequent cause of life-threatening sepsis and urinary tract infections (UTI) in adults. The development of an effective and universal vaccine is complicated by this pathogen's pan-genome, its ability to mix and match virulence factors and AMR genes via horizontal gene transfer, an inability to decipher commensal from pathogens, and its intimate association and co-evolution with mammals. Using a pan virulome analysis of >20,000 sequenced E. coli strains, we identified the secreted cytolysin α-hemolysin (HlyA) as a high priority target for vaccine exploration studies. We demonstrate that a catalytically inactive pure form of HlyA, expressed in an autologous host using its own secretion system, is highly immunogenic in a murine host, protects against several forms of ExPEC infection (including lethal bacteremia), and significantly lowers bacterial burdens in multiple organ systems. Interestingly, the combination of a previously reported autotransporter (SinH) with HlyA was notably effective, inducing near complete protection against lethal challenge, including commonly used infection strains ST73 (CFT073) and ST95 (UTI89), as well as a mixture of 10 of the most highly virulent sequence types and strains from our clinical collection. Both HlyA and HlyA-SinH combinations also afforded some protection against UTI89 colonization in a murine UTI model. These findings suggest recombinant, inactive hemolysin and/or its combination with SinH warrant investigation in the development of an E. coli vaccine against invasive disease.

Exosomes Derived from Meningitic Escherichia coli-Infected Brain Microvascular Endothelial Cells Facilitate Astrocyte Activation

Numerous studies have shown that exosomes play a regulatory role in a variety of biological processes as well as in disease development and progression. However, exosome-mediated intercellular communication between brain microvascular endothelial cells (BMECs) and astrocytes during meningitic Escherichia coli (E. coli)-induced neuroinflammation remains largely unknown. Here, by using in vivo and in vitro models, we demonstrate that exosomes derived from meningitic E. coli-infected BMECs can activate the inflammatory response of astrocytes. A label-free quantitation approach coupled with LC-MS/MS was used to compare the exosome proteomic profiles of human BMECs (hBMECs) in response to meningitic E. coli infection. A total of 57 proteins exhibited significant differences in BMEC-derived exosomes during the infection. Among these proteins, growth differentiation factor 15 (GDF15) was significantly increased in BMEC-derived exosomes during the infection, which triggered the Erk1/2 signaling pathway and promoted the activation of astrocytes. The identification and characterization of exosome protein profiles in BMECs during meningitic E. coli infection will contribute to the understanding of the underlying pathogenic mechanisms from the perspective of intercellular communication between BMECs and astrocytes, and provide new insights for future prevention and treatment of E. coli meningitis.

Tamm-Horsfall protein augments neutrophil NETosis during urinary tract infection

Urinary neutrophils are a hallmark of urinary tract infection (UTI), yet the mechanisms governing their activation, function, and efficacy in controlling infection remain incompletely understood. Tamm-Horsfall glycoprotein (THP), the most abundant protein in urine, uses terminal sialic acids to bind an inhibitory receptor and dampen neutrophil inflammatory responses. We hypothesized that neutrophil modulation is an integral part of THP-mediated host protection. In a UTI model, THP-deficient mice showed elevated urinary tract bacterial burdens, increased neutrophil recruitment, and more severe tissue histopathological changes compared to WT mice. Furthermore, THP-deficient mice displayed impaired urinary NETosis during UTI. To investigate the impact of THP on NETosis, we coupled in vitro fluorescence-based NET assays, proteomic analyses, and standard and imaging flow cytometry with peripheral human neutrophils. We found that THP increases proteins involved in respiratory chain, neutrophil granules, and chromatin remodeling pathways, enhances NETosis in an ROS-dependent manner, and drives NET-associated morphologic features including nuclear decondensation. These effects were observed only in the presence of a NETosis stimulus and could not be solely replicated with equivalent levels of sialic acid alone. We conclude that THP is a critical regulator of NETosis in the urinary tract, playing a key role in host defense against UTI.

Therapeutic effects of orally administration of viable and inactivated probiotic strains against murine urinary tract infection

Urinary tract infections (UTIs) are highly prevalent bacterial infections that pose significant health risks. Specific probiotic strains have been recommended for UTI control and management of antibiotic resistance. Otherwise, para-probiotics, defined as inactivated probiotic cells, offer potential advantages by minimizing risks associated with live microorganisms. However, the effectiveness of heat-killed probiotic strains against UTIs remains uncertain. Additionally, lactoferrin (LF), an iron-binding glycoprotein, exhibits immunomodulatory, antimicrobial, and anti-inflammatory properties. Recently, we had developed recombinant LF-expression probiotics, which can display considerate antibacterial activities against select food-borne pathogens in vitro. Thus, the present study aimed to evaluate the antibacterial activities of heat-killed natural and recombinant LF-expressing probiotics against UTIs in vitro and in vivo. Firstly, using in vitro assays, we assessed the antibacterial activity of heat-killed natural and recombinant LF-expressing probiotics against uropathogenic Escherichia coli and Klebsiella pneumoniae. Among the tested probiotics, 10 heat-killed LF-expressing strains displayed superior antibacterial efficacy compared to 12 natural probiotics. Based on their potent in vitro activity, selected probiotics were formulated into three probiotic mixtures: viable probiotic mixture (LAB), heat-killed probiotic mixture (HK-LAB), and heat-killed LF-expressing probiotic mixture (HK-LAB/LF). To further evaluate the therapeutic potential of these probiotic mixtures in vivo, we established a murine model of UTIs by intraurethral administration of E. coli to 40 female C57BL/6JNarl mice on day 0. Subsequently, mice received oral gavage of placebo, LAB, HK-LAB, or HK-LAB/LF for 21 consecutive days (n = 8 per group). An additional control group (n = 8) received ampicillin treatment for 7 days. To assess protective effects against re-infection or UTI relapse, all mice were challenged with E. coli on day 22 and E. coli plus K. pneumoniae on day 25. Results from the murine UTI model demonstrated that placebo administration did not reduce bacteriuria throughout the experiment. Conversely, supplementation with ampicillin, HK-LAB/LF, HK-LAB, or LAB significantly (p < 0.05) reduced daily bacteriuria by 103 to 104-fold on days 1, 3, 5, and 14, respectively. Furthermore, all four therapeutic treatments improved the bacteriological cure rate (BCR) with varying levels of efficacy. For the 7-day treatment course, the BCR was 25% (placebo), 62.5% (ampicillin), 37.5% (LAB), 37.5% (HK-LAB), and 62.5% (HK-LAB/LF). For the 21-day treatment course, the BCR was 25% (placebo), 75% (ampicillin), 37.5% (LAB), 37.5% (HK-LAB), and 75% (HK-LAB/LF). Notably, HK-LAB and HK-LAB/LF demonstrated superior therapeutic efficacy compared to viable LAB in treating UTIs. Overall, regarding BCR, the three probiotic mixtures can provide benefits against UTI in mice, but ampicillin therapy remains the most efficient among the four treatments. Furthermore, there was no significant difference between pre- and post-challenge courses for the two instances of re-challenging uropathogens in all mice groups, as bacteriuria levels remained below 103 CFU/mL, implying that adaptive responses of mice may help reduce the risk of recurrent UTIs. In conclusion, our results provide new evidence that oral administration of heat-killed probiotic mixtures can confer significant therapeutic efficacy against UTIs in a murine model.

Exploring the role of urinary extracellular vesicles in kidney physiology, aging, and disease progression

Extracellular vesicles (EVs), membranous vesicles present in all body fluids, are considered important messengers, carrying their information over long distance and modulating the gene expression profile of recipient cells. EVs collected in urine (uEVs) are mainly originated from the apical part of urogenital tract, following the urine flow. Moreover, bacterial-derived EVs are present within urine and may reflect the composition of microbiota. Consolidated evidence has established the involvement of uEVs in renal physiology, being responsible for glomerular and tubular cross talk and among different tubular segments. uEVs may also be involved in other physiological functions such as modulation of innate immunity, coagulation, or metabolic activities. Furthermore, it has been recently remonstrated that age, sex, endurance excise, and lifestyle may influence uEV composition and release, modifying their cargo. On the other hand, uEVs appear modulators of different urogenital pathological conditions, triggering disease progression. uEVs sustain fibrosis and inflammation processes, both involved in acute and chronic kidney diseases, aging, and stone formation. The molecular signature of uEVs collected from diseased patients can be of interest for understanding kidney physiopathology and for identifying diagnostic and prognostic biomarkers.

Cycle Biodynamics of Women's Microbiome in the Urinary and Reproductive Systems

The genitourinary microbiome plays a crucial role in the establishment and maintenance of urinary and reproductive health in women throughout their lives. Particularly during the reproductive stage, resident microorganisms contribute to implantation and protect against perinatal complications, including preterm birth, stillbirth, and low birth weight, while also serving as the first line of defense against pathogens that can cause infections, such as urinary tract infections and bacterial vaginosis. This review aimed to elucidate the relationship between a healthy microbiome environment and women's overall health. We examine the variability and dynamics of the microbiome during different developmental stages, ranging from the prepubertal to the postmenopausal stage. Furthermore, we explore the significance of a healthy microbiota in successful implantation and pregnancy development and investigate potential differences between women experiencing infertility. In addition, we analyze the local and systemic inflammatory responses associated with the establishment of a dysbiotic state and compare it to a condition where a healthy microbiome was established. Lastly, we present the most recent evidence regarding preventive measures, such as dietary interventions and the use of probiotics to promote and maintain a healthy microbiome, thereby ensuring comprehensive women's health. By highlighting the importance of the genitourinary microbiome in reproductive health, this review aimed to enhance this microbiome's visibility and significance in the field.

Urinary Exosomes: A Promising Biomarker for Disease Diagnosis

Exosomes are nanoscale vesicles derived from endocytosis, formed by fusion of multivesicular bodies with membranes and secreted into the extracellular matrix or body fluids. Many studies have shown that exosomes can be present in a variety of biological fluids, such as plasma, urine, saliva, amniotic fluid, ascites, and sweat, and most types of cells can secrete exosomes. Exosomes play an important role in many aspects of human development, including immunity, cardiovascular diseases, neurodegenerative diseases, and neoplasia. Urine can be an alternative to blood or tissue samples as a potential source of disease biomarkers because of its simple, noninvasive, sufficient, and stable characteristics. Therefore, urinary exosomes have valuable potential for early screening, monitoring disease progression, prognosis, and treatment. The method for isolating urinary exosomes has been perfected, and exosome proteomics is widely used. Therefore, we review the potential use of urinary exosomes for disease diagnosis and summarize the related literature.

Broad protective vaccination against systemic Escherichia coli with autotransporter antigens

Extraintestinal pathogenic Escherichia coli (ExPEC) is the leading cause of adult life-threatening sepsis and urinary tract infections (UTI). The emergence and spread of multidrug-resistant (MDR) ExPEC strains result in a considerable amount of treatment failure and hospitalization costs, and contribute to the spread of drug resistance amongst the human microbiome. Thus, an effective vaccine against ExPEC would reduce morbidity and mortality and possibly decrease carriage in healthy or diseased populations. A comparative genomic analysis demonstrated a gene encoding an invasin-like protein, termed sinH, annotated as an autotransporter protein, shows high prevalence in various invasive ExPEC phylogroups, especially those associated with systemic bacteremia and UTI. Here, we evaluated the protective efficacy and immunogenicity of a recombinant SinH-based vaccine consisting of either domain-3 or domains-1,2, and 3 of the putative extracellular region of surface-localized SinH. Immunization of a murine host with SinH-based antigens elicited significant protection against various strains of the pandemic ExPEC sequence type 131 (ST131) as well as multiple sequence types in two distinct models of infection (colonization and bacteremia). SinH immunization also provided significant protection against ExPEC colonization in the bladder in an acute UTI model. Immunized cohorts produced significantly higher levels of vaccine-specific serum IgG and urinary IgG and IgA, findings consistent with mucosal protection. Collectively, these results demonstrate that autotransporter antigens such as SinH may constitute promising ExPEC phylogroup-specific and sequence-type effective vaccine targets that reduce E. coli colonization and virulence.

Lactoferrin regulates sebogenesis and inflammation in SZ95 human sebocytes and mouse model of acne

BACKGROUND

The aim of this study was to explore the anti-inflammatory and anti-lipid effects of lactoferrin on SZ95 human sebaceous gland cells and mouse model of acne.

METHODS

SZ95 cells were co-cultured with different concentrations of lactoferrin, and cell viability was determined using the 2,5-diphenyl-2H-tetrazolium bromide method. Oil red O and Nile red staining were performed to determine the lipid content. The mRNA expression of genes related to lipid metabolism (sterol regulatory element-binding protein-1 [SREBP-1], fatty acid synthase [FAS], stearoyl-CoA desaturase-1 [SCD-1], fatty acid desaturase 2 [FADS2]) and inflammation (interleukin-8 [IL-8]) was determined by reverse transcription-polymerase chain reaction. An acne mouse model was established using injection of P. acnes on the backs of mice. The proliferation and apoptosis of sebaceous gland cells were examined by immunohistochemistry against proliferating cell nuclear antigen (PCNA) and TUNEL staining, respectively. Western blotting was used to detect FADS2 and CXCL15 protein expression.

RESULTS

Lactoferrin treatment at 10-500 μg/ml significantly decreased the lipid content, as revealed by the oil red O and Nile red staining. It also attenuated the increase of mRNA expression of SREBP-1, FAS, SCD-1, FADS2, and IL-8 in insulin-treated SZ95 cells. Moreover, lactoferrin treatment at the doses of 1-50 mg/mouse significantly reduced the inflammation and lipid production in the mouse model of acne. Also, the number of sebaceous gland cells was significantly reduced, and apoptosis was significantly increased by lactoferrin treatment in the mice. Mechanically, the levels of FADS2 and CXCL15 proteins in tissues were significantly decreased after lactoferrin treatment in the model mice.

CONCLUSION

Our results demonstrate the potential of lactoferrin against sebogenesis, sebaceous gland inflammation in acne.

Iron in infectious diseases friend or foe?: The role of gut microbiota

Iron is a trace element involved in metabolic functions for all organisms, from microorganisms to mammalians. Iron deficiency is a prevalent health problem that affects billions of people worldwide, and iron overload could have some hazardous effect. The complex microbial community in the human body, also called microbiota, influences the host immune defence against infections. An imbalance in gut microbiota, dysbiosis, changes the host's susceptibility to infections by regulating the immune system. In recent years, the number of studies on the relationship between infectious diseases and microbiota has increased. Gut microbiota is affected by different parameters, including mode of delivery, hygiene habits, diet, drugs, and plasma iron levels during the lifetime. Gut microbiota may influence iron levels in the body, and iron overload and deficiency can also affect gut microbiota composition. Novel researches on microbiota shed light on the fact that the bidirectional interactions between gut microbiota and iron play a role in the pathogenesis of many diseases, especially infections. A better understanding of these interactions may help us to comprehend the pathogenesis of many infectious and metabolic diseases affecting people worldwide and following the development of more effective preventive and/or therapeutic strategies. In this review, we aimed to present the iron-mediated host-gut microbiota interactions, susceptibility to bacterial infections, and iron-targeted therapy approaches for infections.

Strengthening of enterococcal biofilms by Esp

Multidrug-resistant (MDR) Enterococcus faecalis are major causes of hospital-acquired infections. Numerous clinical strains of E. faecalis harbor a large pathogenicity island that encodes enterococcal surface protein (Esp), which is suggested to promote biofilm production and virulence, but this remains controversial. To resolve this issue, we characterized the Esp N-terminal region, the portion implicated in biofilm production. Small angle X-ray scattering indicated that the N-terminal region had a globular head, which consisted of two DEv-Ig domains as visualized by X-ray crystallography, followed by an extended tail. The N-terminal region was not required for biofilm production but instead significantly strengthened biofilms against mechanical or degradative disruption, greatly increasing retention of Enterococcus within biofilms. Biofilm strengthening required low pH, which resulted in Esp unfolding, aggregating, and forming amyloid-like structures. The pH threshold for biofilm strengthening depended on protein stability. A truncated fragment of the first DEv-Ig domain, plausibly generated by a host protease, was the least stable and sufficient to strengthen biofilms at pH ≤ 5.0, while the entire N-terminal region and intact Esp on the enterococcal surface was more stable and required a pH ≤ 4.3. These results suggested a virulence role of Esp in strengthening enterococcal biofilms in acidic abiotic or host environments.

The bacterium Enterococcus faecalis is part of the normal microbiome but can also cause serious hospital-acquired infections. Enterococcus strains isolated from hospitals tend to have certain proteins not found in microbiome strains. Such proteins are therefore likely to be important in infection. We sought to understand the function of one such protein, Esp, through biochemical, biophysical, and microbiological techniques. We found that Esp, which is on the bacterial surface, formed amyloid-like fibrils that prevented removal of biofilms. Biofilms are bacterial communities enmeshed within a matrix, and form within the body or on inert objects like catheters. They promote infection by increasing resistance to antibiotics and interfering with clearance by the immune system. We observed that biofilms that lacked Esp could be disrupted much more easily than those that had Esp. We also found that Esp acted only at low pH (i.e., acidic conditions). Exactly how low a pH depended on whether Esp remained on the bacterial surface or was liberated from the surface by a protease, with a human intestinal protease being a likely cause of liberation. In summary, we found that Esp acts at acidic conditions and likely contributes to virulence by preventing the dispersal of biofilms.

The immune responses to different Uropathogens call individual interventions for bladder infection

Urinary tract infection (UTI) caused by uropathogens is the most common infectious disease and significantly affects all aspects of the quality of life of the patients. However, uropathogens are increasingly becoming antibiotic-resistant, which threatens the only effective treatment option available-antibiotic, resulting in higher medical costs, prolonged hospital stays, and increased mortality. Currently, people are turning their attention to the immune responses, hoping to find effective immunotherapeutic interventions which can be alternatives to the overuse of antibiotic drugs. Bladder infections are caused by the main nine uropathogens and the bladder executes different immune responses depending on the type of uropathogens. It is essential to understand the immune responses to diverse uropathogens in bladder infection for guiding the design and development of immunotherapeutic interventions. This review firstly sorts out and comparatively analyzes the immune responses to the main nine uropathogens in bladder infection, and summarizes their similarities and differences. Based on these immune responses, we innovatively propose that different microbial bladder infections should adopt corresponding immunomodulatory interventions, and the same immunomodulatory intervention can also be applied to diverse microbial infections if they share the same effective therapeutic targets.

Phage Resistance Accompanies Reduced Fitness of Uropathogenic Escherichia coli in the Urinary Environment

Urinary tract infection (UTI) is among the most common infections treated worldwide each year and is caused primarily by uropathogenic Escherichia coli (UPEC). Rising rates of antibiotic resistance among uropathogens have spurred a consideration of alternative treatment strategies, such as bacteriophage (phage) therapy; however, phage-bacterial interactions within the urinary environment are poorly defined. Here, we assess the activity of two phages, namely, HP3 and ES17, against clinical UPEC isolates using in vitro and in vivo models of UTI. In both bacteriologic medium and pooled human urine, we identified phage resistance arising within the first 6 to 8 h of coincubation. Whole-genome sequencing revealed that UPEC strains resistant to HP3 and ES17 harbored mutations in genes involved in lipopolysaccharide (LPS) biosynthesis. Phage-resistant strains displayed several in vitro phenotypes, including alterations to adherence to and invasion of human bladder epithelial HTB-9 cells and increased biofilm formation in some isolates. Interestingly, these phage-resistant UPEC isolates demonstrated reduced growth in pooled human urine, which could be partially rescued by nutrient supplementation and were more sensitive to several outer membrane-targeting antibiotics than parental strains. Additionally, phage-resistant UPEC isolates were attenuated in bladder colonization in a murine UTI model. In total, our findings suggest that while resistance to phages, such as HP3 and ES17, may arise readily in the urinary environment, phage resistance is accompanied by fitness costs which may render UPEC more susceptible to host immunity or antibiotics.

IMPORTANCE UTI is one of the most common causes of outpatient antibiotic use, and rising antibiotic resistance threatens the ability to control UTI unless alternative treatments are developed. Bacteriophage (phage) therapy is gaining renewed interest; however, much like with antibiotics, bacteria can readily become resistant to phages. For successful UTI treatment, we must predict how bacteria will evade killing by phage and identify the downstream consequences of phage resistance during bacterial infection. In our current study, we found that while phage-resistant bacteria quickly emerged in vitro, these bacteria were less capable of growing in human urine and colonizing the murine bladder. These results suggest that phage therapy poses a viable UTI treatment if phage resistance confers fitness costs for the uropathogen. These results have implications for developing cocktails of phage with multiple different bacterial targets, of which each is evaded only at the cost of bacterial fitness.

Effect of bovine lactoferrin on recurrent urinary tract infections: in vitro and in vivo evidences

Uropathogenic Escherichia coli (UPEC) strains are the primary cause of urinary tract infections (UTIs). UPEC strains are able to invade, multiply and persisting in host cells. Therefore, UPEC strains are associated to recurrent UTIs requiring long-term antibiotic therapy. However, this therapy is suboptimal due to the increase of multidrug-resistant UPEC. The use of non-antibiotic treatments for managing UTIs is required. Among these, bovine lactoferrin (bLf), a multifunctional cationic glycoprotein, could be a promising tool because inhibits the entry into the host cells of several intracellular bacteria. Here, we demonstrate that 100 μg/ml bLf hinders the invasion of 2.0 ± 0.5 × 10⁴ CFU/ml E. coli CFT073, prototype of UPEC, infecting 2.0 ± 0.5 × 10⁵ cells/ml urinary bladder T24 epithelial cells. The highest protection (100%) is due to the bLf binding with host surface components even if an additional binding to bacterial surface components cannot be excluded. Of note, in the absence of bLf, UPEC survives and multiplies, while bLf significantly decreases bacterial intracellular survival. After these encouraging results, an observational survey on thirty-three patients affected by recurrent cystitis was performed. The treatment consisted in the oral administration of bLf alone or in combination with antibiotics and/or probiotics. After the observation period, a marked reduction of cystitis episodes was observed (p < 0.001) in all patients compared to the episodes occurred during the 6 months preceding the bLf-treatment. Twenty-nine patients did not report cystitis episodes (87.9%) whereas the remaining four (12.1%) experienced only one episode, indicating that bLf could be a worthwhile and safe treatment in counteracting recurrent cystitis.

Extracellular Vesicles: Recent Insights Into the Interaction Between Host and Pathogenic Bacteria

Extracellular vesicles (EVs) are nanosized lipid particles released by virtually every living cell. EVs carry bioactive molecules, shuttle from cells to cells and transduce signals, regulating cell growth and metabolism. Pathogenic bacteria can cause serious infections via a wide range of strategies, and host immune systems also develop extremely complex adaptations to counteract bacterial infections. As notable carriers, EVs take part in the interaction between the host and bacteria in several approaches. For host cells, several strategies have been developed to resist bacteria via EVs, including expelling damaged membranes and bacteria, neutralizing toxins, triggering innate immune responses and provoking adaptive immune responses in nearly the whole body. For bacteria, EVs function as vehicles to deliver toxins and contribute to immune escape. Due to their crucial functions, EVs have great application potential in vaccines, diagnosis and treatments. In the present review, we highlight the most recent advances, application potential and remaining challenges in understanding EVs in the interaction between the host and bacteria.

Tissue Immunity in the Bladder

The bladder is a major component of the urinary tract, an organ system that expels metabolic waste and excess water, which necessitates proximity to the external environment and its pathogens. It also houses a commensal microbiome. Therefore, its tissue immunity must resist pathogen invasion while maintaining tolerance to commensals. Bacterial infection of the bladder is common, with half of women globally experiencing one or more episodes of cystitis in their lifetime. Despite this, our knowledge of bladder immunity, particularly in humans, is incomplete. Here we consider the current view of tissue immunity in the bladder, with a focus on defense against infection. The urothelium has robust immune functionality, and its defensive capabilities are supported by resident immune cells, including macrophages, dendritic cells, natural killer cells, and γδ T cells. We discuss each in turn and consider why adaptive immune responses are often ineffective in preventing recurrent infection, as well as areas of priority for future research.

The Functional Role of Lactoferrin in Intestine Mucosal Immune System and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing ulcerative colitis (UC) and Crohn's disease (CD), is one of the main types of intestinal inflammatory diseases with intestine mucosal immune disorder. Intestine mucosal immune system plays a remarkable and important role in the etiology and pathogenesis of IBD. Therefore, understanding the intestine mucosal immune mechanism is a key step to develop therapeutic interventions for IBD. Intestine mucosal immune system and IBD are influenced by various factors, such as inflammation, gut permeability, gut microbiota, and nutrients. Among these factors, emerging evidence show that nutrients play a key role in inflammation activation, integrity of intestinal barrier, and immune cell modulation. Lactoferrin (LF), an iron-binding glycoprotein belonging to transferrin family, is a dietary bioactive component abundantly found in mammalian milk. Notably, LF has been reported to perform diverse biological functions including antibacterial activity, anti-inflammatory activity, intestinal barrier protection, and immune cell modulation, and is involved in maintaining intestine mucosal immune homeostasis. The improved understanding of the properties of LF in intestine mucosal immune system and IBD will facilitate its application in nutrition, clinical medicine, and health. Herein, this review outlines the recent advancements on LF as a potential therapeutic intervention for IBD associated with intestine mucosal immune system dysfunction. We hope this review will provide a reference for future studies and lay a theoretical foundation for LF-based therapeutic interventions for IBD by understanding the particular effects of LF on intestine mucosal immune system.

Copper Resistance Promotes Fitness of Methicillin-Resistant Staphylococcus aureus during Urinary Tract Infection

Urinary tract infection (UTI) is one of the most common infectious conditions affecting people in the United States and around the world. Our knowledge of the host-pathogen interaction during UTI caused by Gram-positive bacterial uropathogens is limited compared to that for Gram-negative pathogens. Here, we investigated whether copper and the primary copper-containing protein, ceruloplasmin, are mobilized to urine during naturally occurring UTI caused by Gram-positive uropathogens in patients. Next, we probed the role of copper resistance in the fitness of methicillin-resistant Staphylococcus aureus (MRSA) during experimental UTI in a murine model. Our findings demonstrate that urinary copper and ceruloplasmin content are elevated during UTI caused by Enterococcus faecalis, S. aureus, S. epidermidis, and S. saprophyticus. MRSA strains successfully colonize the urinary tract of female CBA mice with selective induction of inflammation in the kidneys but not the bladder. MRSA mutants lacking CopL, a copper-binding cell surface lipoprotein, and the ACME genomic region containing copL, exhibit decreased fitness in the mouse urinary tract compared to parental strains. Copper sensitivity assays, cell-associated copper and iron content, and bioavailability of iron during copper stress demonstrate that homeostasis of copper and iron is interlinked in S. aureus. Importantly, relative fitness of the MRSA mutant lacking the ACME region is further decreased in mice that receive supplemental copper compared to the parental strain. In summary, copper is mobilized to the urinary tract during UTI caused by Gram-positive pathogens, and copper resistance is a fitness factor for MRSA during UTI. IMPORTANCE Urinary tract infection (UTI) is an extremely common infectious condition affecting people throughout the world. Increasing antibiotic resistance in pathogens causing UTI threatens our ability to continue to treat patients in the clinics. Better understanding of the host-pathogen interface is critical for development of novel interventional strategies. Here, we sought to elucidate the role of copper in host-Staphylococcus aureus interaction during UTI. Our results reveal that copper is mobilized to the urine as a host response in patients with UTI. Our findings from the murine model of UTI demonstrate that copper resistance is involved in the fitness of methicillin-resistant S. aureus (MRSA) during interaction with the host. We also establish a critical link between adaptation to copper stress and iron homeostasis in S. aureus.

The microbiome and host mucosal interactions in urinary tract diseases

The urinary tract consists of the bladder, ureters, and kidneys, and is an essential organ system for filtration and excretion of waste products and maintaining systemic homeostasis. In this capacity, the urinary tract is impacted by its interactions with other mucosal sites, including the genitourinary and gastrointestinal systems. Each of these sites harbors diverse ecosystems of microbes termed the microbiota, that regulates complex interactions with the local and systemic immune system. It remains unclear whether changes in the microbiota and associated metabolites may be a consequence or a driver of urinary tract diseases. Here, we review the current literature, investigating the impact of the microbiota on the urinary tract in homeostasis and disease including urinary stones, acute kidney injury, chronic kidney disease, and urinary tract infection. We propose new avenues for exploration of the urinary microbiome using emerging technology and discuss the potential of microbiome-based medicine for urinary tract conditions.

Hypoxia-Inducible Factor 1 Alpha Is Dispensable for Host Defense of Group B Streptococcus Colonization and Infection

Group B Streptococcus (GBS) is a leading cause of neonatal morbidity and mortality, and the primary source of exposure is the maternal vagina. Intrapartum antibiotic prophylaxis for GBS-positive mothers has reduced the incidence of GBS early-onset disease, however, potential long-lasting influence of an antibiotic-altered neonatal microbiota, and the frequent clinical sequelae in survivors of invasive GBS infection, compels alternative treatment options for GBS. Here, we examined the role of transcription factor hypoxia-inducible factor 1 alpha (HIF-1α), widely recognized as a regulator of immune activation during infection, in the host response to GBS. Given the importance of endogenous HIF-1α for innate immune defense, and the potential utility of HIF-1α stabilization in promoting bacterial clearance, we hypothesized that HIF-1α could play an important role in coordinating host responses to GBS in colonization and systemic disease. Counter to our hypothesis, we found that GBS infection did not induce HIF-1α expression in vaginal epithelial cells or murine macrophages, nor did HIF-1α deficiency alter GBS colonization or pathogenesis in vivo. Furthermore, pharmacological enhancement of HIF-1α did not improve control of GBS in pathogenesis and colonization models, while displaying inhibitory effects in vaginal epithelial cytokines and immune cell killing in vitro. Taken together, we conclude that HIF-1α is not a prominent aspect of the host response to GBS colonization or invasive disease, and its pharmacological modulation is unlikely to provide significant benefit against this important neonatal pathogen.

Natural resources to control COVID-19: could lactoferrin amend SARS-CoV-2 infectivity?

The world population is still facing the second wave of the COVID-19 pandemic. Such a challenge requires complicated tools to control, namely vaccines, effective cures, and complementary agents. Here we present one candidate for the role of an effective cure and/or complementary agent: lactoferrin. It is the cross-talking mediator between many organs/cellular systems in the body. It serves as a physiological, immunological, and anti-microbial barrier, and acts as a regulator molecule. Furthermore, lactoferrin has receptors on most tissues cells, and is a rich source for bioactive peptides, particularly in the digestive system. In the past months, in vitro and in vivo evidence has accumulated regarding lactoferrin's ability to control SARS-CoV-2 infectivity in different indicated scenarios. Also, lactoferrin or whey milk (of human or other mammal's origin) is a cheap, easily available, and safe agent, the use of which can produce promising results. Pharmaceutical and/or food supplementary formulas of lactoferrin could be particularly effective in controlling the gastrointestinal COVID-19-associated symptoms and could limit the fecal-oral viral infection transmission, through mechanisms that mimic that of norovirus infection control by lactoferrin via induction of intestinal innate immunity. This natural avenue may be effective not only in symptomatic patients, but could also be more helpful in asymptomatic patients as a main or adjuvant treatment.

Antibacterial and Anti-biofilm Activity of the Human Breast Milk Glycoprotein Lactoferrin against Group B Streptococcus

Group B Streptococcus (GBS) is an encapsulated Gram-positive human pathogen that causes invasive infections in pregnant hosts and neonates, as well as immunocompromised individuals. Colonization of the human host requires the ability to adhere to mucosal surfaces and circumnavigate the nutritional challenges and antimicrobial defenses associated with the innate immune response. Biofilm formation is a critical process to facilitate GBS survival and establishment of a replicative niche in the vertebrate host. Previous work has shown that the host responds to GBS infection by producing the innate antimicrobial glycoprotein lactoferrin, which has been implicated in repressing bacterial growth and biofilm formation. Additionally, lactoferrin is highly abundant in human breast milk and could serve a protective role against invasive microbial pathogens. This study demonstrates that human breast milk lactoferrin has antimicrobial and anti-biofilm activity against GBS and inhibits its adherence to human gestational membranes. Together, these results indicate that human milk lactoferrin could be used as a prebiotic chemotherapeutic strategy to limit the impact of bacterial adherence and biofilm formation on GBS-associated disease outcomes.

Novel Models of Streptococcus canis Colonization and Disease Reveal Modest Contributions of M-Like (SCM) Protein

Streptococcus canis is a common colonizing bacterium of the urogenital tract of cats and dogs that can also cause invasive disease in these animal populations and in humans. Although the virulence mechanisms of S. canis are not well-characterized, an M-like protein, SCM, has recently identified been as a potential virulence factor. SCM is a surface-associated protein that binds to host plasminogen and IgGs suggesting its possible importance in host-pathogen interactions. In this study, we developed in vitro and ex vivo blood component models and murine models of S. canis vaginal colonization, systemic infection, and dermal infection to compare the virulence potential of the zoonotic S. canis vaginal isolate G361 and its isogenic SCM-deficient mutant (G361∆scm). We found that while S. canis establishes vaginal colonization and causes invasive disease in vivo, the contribution of the SCM protein to virulence phenotypes in these models is modest. We conclude that SCM is dispensable for invasive disease in murine models and for resistance to human blood components ex vivo, but may contribute to mucosal persistence, highlighting a potential contribution to the recently appreciated genetic diversity of SCM across strains and hosts.

The immune response to infection in the bladder

The bladder is continuously protected by passive defences such as a mucus layer, antimicrobial peptides and secretory immunoglobulins; however, these defences are occasionally overcome by invading bacteria that can induce a strong host inflammatory response in the bladder. The urothelium and resident immune cells produce additional defence molecules, cytokines and chemokines, which recruit inflammatory cells to the infected tissue. Resident and recruited immune cells act together to eradicate bacteria from the bladder and to develop lasting immune memory against infection. However, urinary tract infection (UTI) is commonly recurrent, suggesting that the induction of a memory response in the bladder is inadequate to prevent reinfection. Additionally, infection seems to induce long-lasting changes in the urothelium, which can render the tissue more susceptible to future infection. The innate immune response is well-studied in the field of UTI, but considerably less is known about how adaptive immunity develops and how repair mechanisms restore bladder homeostasis following infection. Furthermore, data demonstrate that sex-based differences in immunity affect resolution and infection can lead to tissue remodelling in the bladder following resolution of UTI. To combat the rise in antimicrobial resistance, innovative therapeutic approaches to bladder infection are currently in development. Improving our understanding of how the bladder responds to infection will support the development of improved treatments for UTI, particularly for those at risk of recurrent infection.

Formulation of host-targeted therapeutics against bacterial infections

The global burden of bacterial infections is rising due to increasing resistance to the majority of first-line antibiotics, rendering these drugs ineffective against several clinically important pathogens. Limited transport of antibiotics into cells compounds this problem for gram-negative bacteria that exhibit prominent intracellular lifecycles. Furthermore, poor bioavailability of antibiotics in infected tissues necessitates higher doses and longer treatment regimens to treat resistant infections. Although emerging antibiotics can combat these problems, resistance still may develop over time. Expanding knowledge of host-pathogen interactions has inspired research and development of host-directed therapies (HDTs). HDTs target host-cell machinery critical for bacterial pathogenesis to treat bacterial infections alone or as adjunctive treatment with traditional antibiotics. Unlike traditional antibiotics that directly affect bacteria, a majority of HDTs function by boosting the endogenous antimicrobial activity of cells and are consequently less prone to bacterial tolerance induced by selection pressure. Therefore, HDTs can be quite effective against intracellular cytosolic or vacuolar bacteria, which a majority of traditional antibiotics are unable to eradicate. However, in vivo therapeutic efficacy of HDTs is reliant on adequate bioavailability. Particle-based formulations demonstrate the potential to enable targeted drug delivery, enhance cellular uptake, and increase drug concentration in the host cell of HDTs. This review selected HDTs for clinically important pathogens, identifies formulation strategies that can improve their therapeutic efficacy and offers insights toward further development of HDTs for bacterial infections.

The Biology of Lactoferrin, an Iron-Binding Protein That Can Help Defend Against Viruses and Bacteria

Lactoferrin is a nutrient classically found in mammalian milk. It binds iron and is transferred via a variety of receptors into and between cells, serum, bile, and cerebrospinal fluid. It has important immunological properties, and is both antibacterial and antiviral. In particular, there is evidence that it can bind to at least some of the receptors used by coronaviruses and thereby block their entry. Of importance are Heparan Sulfate Proteoglycans (HSPGs) and the host receptor angiotensin-converting enzyme 2 (ACE2), as based on other activities lactoferrin might prevent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from attaching to the host cells. Lactoferrin (and more specifically enteric-coated LF because of increased bioavailability) may consequently be of preventive and therapeutic value during the present COVID-19 pandemic.

Host Cathelicidin Exacerbates Group B Streptococcus Urinary Tract Infection

Group B Streptococcus (GBS) causes frequent urinary tract infection (UTI) in susceptible populations, including individuals with type 2 diabetes and pregnant women; however, specific host factors responsible for increased GBS susceptibility in these populations are not well characterized. Here, we investigate cathelicidin, a cationic antimicrobial peptide, known to be critical for defense during UTI with uropathogenic Escherichia coli (UPEC). We observed a loss of antimicrobial activity of human and mouse cathelicidins against GBS and UPEC in synthetic urine and no evidence for increased cathelicidin resistance in GBS urinary isolates. Furthermore, we found that GBS degrades cathelicidin in a protease-dependent manner. Surprisingly, in a UTI model, cathelicidin-deficient (Camp-/-) mice showed decreased GBS burdens and mast cell recruitment in the bladder compared to levels in wild-type (WT) mice. Pharmacologic inhibition of mast cells reduced GBS burdens and histamine release in WT but not Camp-/- mice. Streptozotocin-induced diabetic mice had increased bladder cathelicidin production and mast cell recruitment at 24 h postinfection with GBS compared to levels in nondiabetic controls. We propose that cathelicidin is an important immune regulator but ineffective antimicrobial peptide against GBS in urine. Combined, our findings may in part explain the increased frequency of GBS UTI in diabetic and pregnant individuals.IMPORTANCE Certain populations such as diabetic individuals are at increased risk for developing urinary tract infections (UTI), although the underlying reasons for this susceptibility are not fully known. Additionally, diabetics are more likely to become infected with certain types of bacteria, such as group B Streptococcus (GBS). In this study, we find that an antimicrobial peptide called cathelicidin, which is thought to protect the bladder from infection, is ineffective in controlling GBS and alters the type of immune cells that migrate to the bladder during infection. Using a mouse model of diabetes, we observe that diabetic mice are more susceptible to GBS infection even though they also have more infiltrating immune cells and increased production of cathelicidin. Taken together, our findings identify this antimicrobial peptide as a potential contributor to increased susceptibility of diabetic individuals to GBS UTI.

Urinary tract infections: microbial pathogenesis, host-pathogen interactions and new treatment strategies

Urinary tract infections (UTIs) are common, recurrent infections that can be mild to life-threatening. The continued emergence of antibiotic resistance, together with our increasing understanding of the detrimental effects conferred by broad-spectrum antibiotic use on the health of the beneficial microbiota of the host, has underscored the weaknesses in our current treatment paradigm for UTIs. In this Review, we discuss how recent microbiological, structural, genetic and immunological studies have expanded our understanding of host-pathogen interactions during UTI pathogenesis. These basic scientific findings have the potential to shift the strategy for UTI treatment away from broad-spectrum antibiotics targeting conserved aspects of bacterial replication towards pathogen-specific antibiotic-sparing therapeutics that target core determinants of bacterial virulence at the host-pathogen interface.