Toll-like receptor polymorphisms and susceptibility to urinary tract infections in adult women

Urinary Microbiome Research Has Not Established a Conclusive Influence: Revisiting Koch's Postulates

In order to establish a causal relationship between urinary microbiota and a urological disease or condition, a series of rigorous scientific criteria must be met. Demonstration of an association between microbiota and a condition does not necessarily imply causality, importance, or clinical relevance.

Genetic polymorphisms associated with urinary tract infection in children and adults: a systematic review and meta-analysis

INTRODUCTION

The lifetime risk of urinary tract infection is known from first-degree relative studies to be highly heritable. Associations have also been observed across the life course from pediatric urinary tract infection to recurrent urinary tract infection in adulthood, suggesting lifelong susceptibility factors. Candidate gene studies and genome-wide association studies have tested for genetic associations of urinary tract infection; however, no contemporary systematic synthesis of studies is available.

OBJECTIVE

We conducted a systematic review to identify all genetic polymorphisms tested for an association with urinary tract infection in children and adults; and to assess their strength, consistency, and risk of bias among reported associations.

DATA SOURCES AND STUDY ELIGIBILITY CRITERIA

PubMed, HuGE Navigator and Embase were searched from January 1, 2005 to November 16, 2023, using a combination of genetic and phenotype key words.

STUDY APPRAISAL AND SYNTHESIS METHODS

Fixed and random effects meta-analyses were conducted using codominant models of inheritance in metan. The interim Venice criteria were used to assess their credibility of pooled associations.

RESULTS

After removing 451 duplicates, 1821 studies reports were screened, with 106 selected for full-text review, 22 were included in the meta-analysis (7 adult studies and 15 pediatric studies). Our meta-analyses demonstrated significant pooled associations for pediatric urinary tract infection with variation in CXCR1, IL8, TGF, TLR4 and VDR; all of which have plausible roles in the pathogenesis of urinary tract infection. Our meta-analyses also demonstrated a significant pooled association for adult urinary tract infection with variation in CXCR1. All significant pooled associations were graded according to their epidemiological credibility, sample sizes, heterogeneity between studies, and risk of bias.

CONCLUSION

This systematic review provides a current synthesis of the known genetic architecture of urinary tract infection in childhood and adulthood; and should provide important information for researchers analysing future genetic association studies. Although, overall, the credibility of pooled associations was weak, the consistency of findings for rs2234671 single nucleotide polymorphisms of CXCR1 in both populations suggest a key role in the urinary tract infection pathogenesis.

DEFA1A3 DNA gene-dosage regulates the kidney innate immune response during upper urinary tract infection

Antimicrobial peptides (AMPs) are host defense effectors with potent neutralizing and immunomodulatory functions against invasive pathogens. The AMPs α-Defensin 1-3/DEFA1A3 participate in innate immune responses and influence patient outcomes in various diseases. DNA copy-number variations in DEFA1A3 have been associated with severity and outcomes in infectious diseases including urinary tract infections (UTIs). Specifically, children with lower DNA copy numbers were more susceptible to UTIs. The mechanism of action by which α-Defensin 1-3/DEFA1A3 copy-number variations lead to UTI susceptibility remains to be explored. In this study, we use a previously characterized transgenic knock-in of the human DEFA1A3 gene mouse to dissect α-Defensin 1-3 gene dose-dependent antimicrobial and immunomodulatory roles during uropathogenic Escherichia coli (UPEC) UTI. We elucidate the relationship between kidney neutrophil- and collecting duct intercalated cell-derived α-Defensin 1-3/DEFA1A3 expression and UTI. We further describe cooperative effects between α-Defensin 1-3 and other AMPs that potentiate the neutralizing activity against UPEC. Cumulatively, we demonstrate that DEFA1A3 directly protects against UPEC meanwhile impacting pro-inflammatory innate immune responses in a gene dosage-dependent manner.

Uropathogen and host responses in pyelonephritis

Urinary tract infections (UTIs) are among the most common bacterial infections seen in clinical practice. The ascent of UTI-causing pathogens to the kidneys results in pyelonephritis, which can trigger kidney injury, scarring and ultimately impair kidney function. Despite sizable efforts to understand how infections develop or are cleared in the bladder, our appreciation of the mechanisms by which infections develop, progress or are eradicated in the kidney is limited. The identification of virulence factors that are produced by uropathogenic Escherichia coli to promote pyelonephritis have begun to fill this knowledge gap, as have insights into the mechanisms by which kidney tubular epithelial cells oppose uropathogenic E. coli infection to prevent or eradicate UTIs. Emerging data also illustrate how specific cellular immune responses eradicate infection whereas other immune cell populations promote kidney injury. Insights into the mechanisms by which uropathogenic E. coli circumvent host immune defences or antibiotic therapy to cause pyelonephritis is paramount to the development of new prevention and treatment strategies to mitigate pyelonephritis and its associated complications.

Chronic Kidney Disease, Urinary Tract Infections and Antibiotic Nephrotoxicity: Are There Any Relationships?

Chronic kidney disease (CKD) has been a constant burden worldwide, with a prevalence of more than 10% of the population and with mortality reaching 1.2 million deaths and 35.8 million disability-adjusted life years (DALYs) in 2017, as it is claimed by the Global Burden of Diseases. Moreover, an increase in its prevalence is expected in the next years due to a rise in the number of people suffering from obesity, diabetes mellitus and hypertension. On the other hand, with cardiovascular morbidity and mortality showing a downward trend, maybe it is time to focus on CKD, to minimize the preventable risk factors involved in its progression toward end-stage kidney disease (ESKD) and to offer a better quality of life. Another major health burden is represented by infectious diseases, particularly urinary tract infections (UTIs), as it is considered that approximately 40-50% of women and 5% of men will have at least one episode during their lifetime. Additionally, CKD consists of a constellation of immunological and metabolical disturbances that lead to a greater risk of UTIs: increased apoptosis of lymphocytes, elevated levels of tumor necrosis factor α and interleukin 6, which lower the function of neutrophils and increased levels of uremic toxins like p-cresyl sulfate and indoxyl sulfate, which alter the adherence and migration of leukocytes to the sites of injury. Moreover, UTIs can lead to a more rapid decline of kidney function, especially in stages G3-G5 of CKD, with all the complications involved. Last, but not least, antibiotherapy is often complicated in this category of patients, as antibiotics can also negatively affect the kidneys. This review will try to focus on the particularities of the urinary microbiome, asymptomatic bacteriuria and UTIs and the subtle balance between the risks of them and the risks of antibiotherapy in the evolution of CKD.

A Systematic Review of the (Un)known Host Immune Response Biomarkers for Predicting Recurrence of Urinary Tract Infection

Recurrent urinary tract infections (rUTI) represent a major healthcare and economic burden along with a significant impact on patient’s morbidity and quality of life, even in the absence of well-known risk factors, such as vesicoureteral reflux. Despite numerous attempts to find a suitable therapeutic option, there is no clear benefit of any currently available intervention for prevention of UTI recurrence and its long-term consequences such as hypertension, renal scarring and/or insufficiency. The common treatment practice in many centers around the globe involves the use of continuous low-dose antibiotic prophylaxis, irrespective of various studies indicating increased microbial resistance against the prophylactic drug, leading to prolonged duration and escalating the cost of UTI treatment. Moreover, the rapid appearance of multi-drug resistant uropathogens is threatening to transform UTI to untreatable disease, while impaired host-microbiota homeostasis induced by a long-term use of antibiotics predisposes patients for various autoimmune and infectious diseases. New biomarkers of the increased risk of UTI recurrence could therefore assist in avoiding such outcomes by revealing more specific patient population which could benefit from additional interventions. In this light, the recent findings suggesting a crucial role of urothelial innate immunity mechanisms in protection of urinary tract from invading uropathogens might offer new diagnostic, prognostic and even therapeutic opportunities. Uroepithelial cells detect uropathogens via pattern recognition receptors, resulting in activation of intracellular signaling cascade and transcription factors, which ultimately leads to an increased production and secretion of chemokines, cytokines and antimicrobial peptides into the urinary stream. Emerging evidence suggest that the disturbance of a single component of the urinary tract innate immunity system might increase susceptibility for rUTI. The aim of the current review is to update clinicians and researchers on potential biomarkers of host immune response alterations predisposing for rUTI and propose those well worth exploring further. For this purpose, over a hundred original papers were identified through an extensive PubMed and Scopus databases search. This comprehensive review might enrich the current clinical practice and fill the unmet clinical needs, but also encourage the development of therapeutic agents that would facilitate urinary bacterial clearance by enhancing the host immune response.

The correlation between non-O blood group type and recurrent catheter-associated urinary tract infections in critically ill patients: A retrospective study

Objective

To investigate the correlation between the ABO blood group and the risk of recurrent catheter-associated urinary tract infections (CA-UTI) and multi-drug resistant (MDR) organism reinfection in the critically ill.

Methods

This retrospective cohort study enrolled adult patients admitted to the intensive care unit (ICU) with confirmed CA-UTI to investigate the correlation between ABO type and the susceptibility to recurrent, reinfection and MDR reinfection. Patients were classified into two groups based on ABO type (O blood group versus non-O blood group).

Results

A total of 81 patients were included in the study: 37 in the O blood group and 44 in the non-O blood group. Patients in the O blood group were associated with significantly lower odds of recurrent CA-UTI (adjusted odds ratio 0.28; 95% confidence interval 0.08, 0.95), a shorter ICU length of stay (LOS) (estimate [SE] –0.24 [0.05]), hospital LOS (estimate [SE] –0.15 [0.03]) and mechanical ventilation duration (estimate [SE] –0.41 [0.07]) compared with the non-O blood group type.

Conclusion

Non-O blood group type might be a risk factor for recurrent CA-UTI and infection with MDR organism.

Immunomodulation therapy offers new molecular strategies to treat UTI

Innovative solutions are needed for the treatment of bacterial infections, and a range of antibacterial molecules have been explored as alternatives to antibiotics. A different approach is to investigate the immune system of the host for new ways of making the antibacterial defence more efficient. However, the immune system has a dual role as protector and cause of disease: in addition to being protective, increasing evidence shows that innate immune responses can become excessive and cause acute symptoms and tissue pathology during infection. This role of innate immunity in disease suggests that the immune system should be targeted therapeutically, to inhibit over-reactivity. The ultimate goal is to develop therapies that selectively attenuate destructive immune response cascades, while augmenting the protective antimicrobial defence but such treatment options have remained underexplored, owing to the molecular proximity of the protective and destructive effects of the immune response. The concept of innate immunomodulation therapy has been developed successfully in urinary tract infections, based on detailed studies of innate immune activation and disease pathogenesis. Effective, disease-specific, immunomodulatory strategies have been developed by targeting specific immune response regulators including key transcription factors. In acute pyelonephritis, targeting interferon regulatory factor 7 using small interfering RNA or treatment with antimicrobial peptide cathelicidin was protective and, in acute cystitis, targeting overactive effector molecules such as IL-1β, MMP7, COX2, cAMP and the pain-sensing receptor NK1R has been successful in vivo. Furthermore, other UTI treatment strategies, such as inhibiting bacterial adhesion and vaccination, have also shown promise.

Hyperactivation of innate immunity is a disease determinant in urinary tract infections (UTIs). Modulation of innate immunity has promise as a therapy for UTIs. In this Review, the authors discuss potential mechanisms and immunomodulatory therapeutic strategies in UTIs.

Excessive innate immune responses to infection cause symptoms and pathology in acute pyelonephritis and acute cystitis.

Innate immunomodulation therapy is, therefore, a realistic option for treating these conditions.

Targeting excessive innate immune responses at the level of transcription has been successful in animal models.

Innate immunomodulation therapy reduces excessive inflammation and tissue pathology and accelerates bacterial clearance from infected kidneys and bladders in mice.

Innate immunomodulation therapy also accelerates the clearance of antibiotic-resistant bacterial strains.

Multidrug-resistant Uro-associated Escherichia coli Populations and Recurrent Urinary Tract Infections in Patients Performing Clean Intermittent Self-catheterisation

BACKGROUND

The AnTIC trial linked continuous low-dose antibiotic prophylaxis treatments to a lower incidence of symptomatic urinary tract infections (UTIs) among individuals performing clean intermittent self-catheterisation (CISC).

OBJECTIVE

To explore potential mechanisms underlying the protective effects of low-dose antibiotic prophylaxis treatments, blood and urine samples and uro-associated Escherichia coli isolates from AnTIC participants were analysed.

DESIGN SETTING AND PARTICIPANTS

Blood samples (n = 204) were analysed for TLR gene polymorphisms associated with UTI susceptibility and multiple urine samples (n = 558) were analysed for host urogenital responses. E.coli sequence data for 45 temporal isolates recovered from the urine samples of 16 trial participants in the prophylaxis (n = 9) and no-prophylaxis (n = 7) study arms, and characterised by multidrug resistance (MDR), were used to classify individual strains.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

TLR polymorphism data were analysed using Poisson regression. Concentrations of urine host defence markers were analysed using linear mixed-effects models, which accounted for repeated urine samples.

RESULTS AND LIMITATIONS

Urine samples from CISC users, irrespective of antibiotic treatment regimens, were associated with robust urothelial innate responses. No links were identified between TLR genotype and CISC user susceptibility to recurrent UTIs. Microbiological study data were limited to the predominant MDR E. coli population; participants prescribed low-dose prophylactic antibiotics were predominantly colonised by a single uro-associated E. coli strain, while participants given acute antibiotic treatments were each colonised by more than one E. coli strain.

CONCLUSIONS

Antibiotic treatments did not impact urogenital responses to infection in CISC users. Host genetics in terms of TLR polymorphisms played no role in determining CISC user susceptibility to or protection from recurrent UTIs. Prophylactic antibiotic treatments associated with MDR E. coli were associated with colonisation by stable uro-associated E. coli genotypes.

PATIENT SUMMARY

Our findings show that the natural urogenital defences of clean intermittent self-catheterisation (CISC) users were not impacted by antibiotic treatments. For some CISC users, prophylaxis with low-dose antibiotics selected for a stable, predominantly, Esherichia coli rich uromicrobiota.

Recurring Cystitis: How Can We Do Our Best to Help Patients Help Themselves?

Recurrent cystitis (RC) has rarely been studied; its management varies and research on a holistic approach of these patients is scarce. We attempted to characterize patients suffering from RC and investigated their current care pathways, aiming to offer customized and autonomous management. In this paper, we present a descriptive, single-center, cross-sectional study of women presenting with RC at an infectious disease (ID) clinic. A questionnaire was developed and was completed by ID physicians during patient visits. From October 2016 to January 2019, 202 women were included (mean age 59 years). Sexual intercourse, stress and diarrhoea/digestive symptoms were reported as trigger factors by 35%, 34% and 19% of patients, respectively. A majority (54%) were at risk for complications and were those more exposed to inappropriate antibiotic prescriptions. In total, 56% of women suffered from more than 10 episodes/year and 48% suffered from relapses, mainly due to E. coli. Genitourinary syndrome of menopause (GSM) was a frequent complaint (74.5% of women). Fluoroquinolones and 3rd generation cephalosporins were prescribed in 38% and 30% of women, respectively. Most women wished for non-antimicrobial approaches and autonomy. Patients require comprehensive, tailored care in order to benefit from a broader range of treatment options in compliance with recommendations.

Toll-Like Receptors (TLRs) in Health and Disease: An Overview

Toll-like receptors were discovered as proteins playing a crucial role in the dorsoventral patterning during embryonic development in the Drosophila melanogaster (D. melanogaster) almost 40 years ago. Subsequently, further research also showed a role of the Toll protein or Toll receptor in the recognition of Gram-positive bacterial and fungal pathogens infecting D. melanogaster. In 1997, the human homolog was reported and the receptor was named the Toll-like receptor 4 (TLR4) that recognizes lipopolysaccharide (LPS) of the Gram-negative bacteria as a pathogen-associated molecular pattern (PAMP). Identification of TLR4 in humans filled the long existing gap in the field of infection and immunity, addressing the mystery surrounding the recognition of foreign pathogens/microbes by the immune system. It is now known that mammals (mice and humans) express 13 different TLRs that are expressed on the outer cell membrane or intracellularly, and which recognize different PAMPs or microbe-associated molecular patterns (MAMPs) and death/damage-associated molecular patterns (DAMPs) to initiate the protective immune response. However, their dysregulation generates profound and prolonged pro-inflammatory immune responses responsible for different inflammatory and immune-mediated diseases. This chapter provides an overview of TLRs in the control of the immune response, their association with different diseases, including TLR single nucleotide polymorphisms (SNPs), interactions with microRNAs (miRs), use in drug development and vaccine design, and expansion in neurosciences to include pain, addiction, metabolism, reproduction, and wound healing.

Risk Indicators for Urinary Tract Infections in Low Risk Pregnancy and the Subsequent Risk of Preterm Birth

Symptomatic urinary tract infections are associated with preterm birth. However, data on risk indicators for urinary tract infections are limited and outdated. The research is a secondary analysis. The study was a prospective multicenter cohort study of low-risk pregnant women. Logistic regression was used to identify risk indicators for urinary tract infections. The incidence of urinary tract infections was 9.4%. Multivariate logistic regression showed that a history of recurrent urinary tract infections and the presence of asymptomatic bacteriuria in the present pregnancy were associated with urinary tract infections (resp. OR 3.14, 95%CI 1.40-7.02 and OR 1.96 95%CI 1.27-3.03). Women with a urinary tract infection were at increased risk of preterm birth compared to women without a urinary tract infection (12 vs. 5.1%; adjusted HR 2.5 95%CI 1.8-3.5). This increased risk was not found in women with the identified risk indicators (resp. 5.3% vs. 5.1%, adjusted HR 0.35 95%CI 0.00-420 and adjusted HR 1.5 95CI% 0.59-3.9). In conclusion, in low-risk pregnant women, risk indicators for urinary tract infections are: a history of recurrent urinary tract infections and the presence of asymptomatic bacteriuria. The risk of preterm birth is increased in women with a urinary tract infection in this pregnancy. However, women with recurrent urinary tract infections and asymptomatic bacteriuria this pregnancy appear not to be at increased risk of preterm birth.

Discrimination of single-point mutations in unamplified genomic DNA via Cas9 immobilized on a graphene field-effect transistor

Simple and fast methods for the detection of target genes with single-nucleotide specificity could open up genetic research and diagnostics beyond laboratory settings. We recently reported a biosensor for the electronic detection of unamplified target genes using liquid-gated graphene field-effect transistors employing an RNA-guided catalytically deactivated CRISPR-associated protein 9 (Cas9) anchored to a graphene monolayer. Here, using unamplified genomic samples from patients and by measuring multiple types of electrical response, we show that the biosensors can discriminate within one hour between wild-type and homozygous mutant alleles differing by a single nucleotide. We also show that biosensors using a guide RNA-Cas9 orthologue complex targeting genes within the protospacer-adjacent motif discriminated between homozygous and heterozygous DNA samples from patients with sickle cell disease, and that the biosensors can also be used to rapidly screen for guide RNA-Cas9 complexes that maximize gene-targeting efficiency.

Convergent Losses of TLR5 Suggest Altered Extracellular Flagellin Detection in Four Mammalian Lineages

Toll-like receptors (TLRs) play an important role for the innate immune system by detecting pathogen-associated molecular patterns. TLR5 encodes the major extracellular receptor for bacterial flagellin and frequently evolves under positive selection, consistent with coevolutionary arms races between the host and pathogens. Furthermore, TLR5 is inactivated in several vertebrates and a TLR5 stop codon polymorphism is widespread in human populations. Here, we analyzed the genomes of 120 mammals and discovered that TLR5 is convergently lost in four independent lineages, comprising guinea pigs, Yangtze river dolphin, pinnipeds, and pangolins. Validated inactivating mutations, absence of protein-coding transcript expression, and relaxed selection on the TLR5 remnants confirm these losses. PCR analysis further confirmed the loss of TLR5 in the pinniped stem lineage. Finally, we show that TLR11, encoding a second extracellular flagellin receptor, is also absent in these four lineages. Independent losses of TLR5 and TLR11 suggest that a major pathway for detecting flagellated bacteria is not essential for different mammals and predicts an impaired capacity to sense extracellular flagellin.

Pharmacogenetics-Based Preliminary Algorithm to Predict the Incidence of Infection in Patients Receiving Cytotoxic Chemotherapy for Hematological Malignancies: A Discovery Cohort

Introduction: Infections in hematological cancer patients are common and usually life-threatening; avoiding them could decrease morbidity, mortality, and cost. Genes associated with antineoplastics’ pharmacokinetics or with the immune/inflammatory response could explain variability in infection occurrence.

Objective: To build a pharmacogenetic-based algorithm to predict the incidence of infections in patients undergoing cytotoxic chemotherapy.

Methods: Prospective cohort study in adult patients receiving cytotoxic chemotherapy to treat leukemia, lymphoma, or myeloma in two hospitals in Santiago, Chile. We constructed the predictive model using logistic regression. We assessed thirteen genetic polymorphisms (including nine pharmacokinetic—related genes and four inflammatory response-related genes) and sociodemographic/clinical variables to be incorporated into the model. The model’s calibration and discrimination were used to compare models; they were assessed by the Hosmer-Lemeshow goodness-of-fit test and area under the ROC curve, respectively, in association with Pseudo-R².

Results: We analyzed 203 chemotherapy cycles in 50 patients (47.8 ± 16.1 years; 56% women), including 13 (26%) with acute lymphoblastic and 12 (24%) with myeloblastic leukemia.

Pharmacokinetics-related polymorphisms incorporated into the model were CYP3A4 rs2242480C>T and OAT4 rs11231809T>A. Immune/inflammatory response-related polymorphisms were TLR2 rs4696480T>A and IL-6 rs1800796C>G. Clinical/demographic variables incorporated into the model were chemotherapy type and cycle, diagnosis, days in neutropenia, age, and sex. The Pseudo-R² was 0.56, the p-value of the Hosmer-Lemeshow test was 0.98, showing good goodness-of-fit, and the area under the ROC curve was 0.93, showing good diagnostic accuracy.

Conclusions: Genetics can help to predict infections in patients undergoing chemotherapy. This algorithm should be validated and could be used to save lives, decrease economic costs, and optimize limited health resources.

Germline Genetic Variants of Viral Entry and Innate Immunity May Influence Susceptibility to SARS-CoV-2 Infection: Toward a Polygenic Risk Score for Risk Stratification

The ongoing COVID-19 pandemic caused by the novel coronavirus, SARS-CoV-2 has affected all aspects of human society with a special focus on healthcare. Although older patients with preexisting chronic illnesses are more prone to develop severe complications, younger, healthy individuals might also exhibit serious manifestations. Previous studies directed to detect genetic susceptibility factors for earlier epidemics have provided evidence of certain protective variations. Following SARS-CoV-2 exposure, viral entry into cells followed by recognition and response by the innate immunity are key determinants of COVID-19 development. In the present review our aim was to conduct a thorough review of the literature on the role of single nucleotide polymorphisms (SNPs) as key agents affecting the viral entry of SARS-CoV-2 and innate immunity. Several SNPs within the scope of our approach were found to alter susceptibility to various bacterial and viral infections. Additionally, a multitude of studies confirmed genetic associations between the analyzed genes and autoimmune diseases, underlining the versatile immune consequences of these variants. Based on confirmed associations it is highly plausible that the SNPs affecting viral entry and innate immunity might confer altered susceptibility to SARS-CoV-2 infection and its complex clinical consequences. Anticipating several COVID-19 genomic susceptibility loci based on the ongoing genome wide association studies, our review also proposes that a well-established polygenic risk score would be able to clinically leverage the acquired knowledge.

Sex effects in pyelonephritis

Urinary tract infections (UTIs) are generally considered a disease of women. However, UTIs affect females throughout the lifespan, and certain male populations (including infants and elderly men) are also susceptible. Epidemiologically, pyelonephritis is more common in women but carries increased morbidity when it does occur in men. Among children, high-grade vesicoureteral reflux is a primary risk factor for upper-tract UTI in both sexes. However, among young infants with UTI, girls are outnumbered by boys; risk factors include posterior urethral valves and lack of circumcision. Recent advances in mouse models of UTI reveal sex differences in innate responses to UTI, which vary somewhat depending on the system used. Moreover, male mice and androgenized female mice suffer worse outcomes in experimental pyelonephritis; evidence suggests that androgen exposure may suppress innate control of infection in the urinary tract, but additional androgen effects, as well as non-hormonal sex effects, may yet be specified. Among other intriguing directions, recent experiments raise the hypothesis that the postnatal testosterone surge that occurs in male infants may represent an additional factor driving the higher incidence of UTI in males under 6 months of age. Ongoing work in contemporary models will further illuminate sex- and sex-hormone-specific effects on UTI pathogenesis and immune responses.

American Academy of Optometry Microbial Keratitis Think Tank

SIGNIFICANCE

Think Tank 2019 affirmed that the rate of infection associated with contact lenses has not changed in several decades. Also, there is a trend toward more serious infections associated with Acanthamoeba and fungi. The growing use of contact lenses in children demands our attention with surveillance and case-control studies.

PURPOSE

The American Academy of Optometry (AAO) gathered researchers and key opinion leaders from around the world to discuss contact lens-associated microbial keratitis at the 2019 AAO Annual Meeting.

METHODS

Experts presented within four sessions. Session 1 covered the epidemiology of microbial keratitis, pathogenesis of Pseudomonas aeruginosa, and the role of lens care systems and storage cases in corneal disease. Session 2 covered nonbacterial forms of keratitis in contact lens wearers. Session 3 covered future needs, challenges, and research questions in relation to microbial keratitis in youth and myopia control, microbiome, antimicrobial surfaces, and genetic susceptibility. Session 4 covered compliance and communication imperatives.

RESULTS

The absolute rate of microbial keratitis has remained very consistent for three decades despite new technologies, and extended wear significantly increases the risk. Improved oxygen delivery afforded by silicone hydrogel lenses has not impacted the rates, and although the introduction of daily disposable lenses has minimized the risk of severe disease, there is no consistent evidence that they have altered the overall rate of microbial keratitis. Overnight orthokeratology lenses may increase the risk of microbial keratitis, especially secondary to Acanthamoeba, in children. Compliance remains a concern and a significant risk factor for disease. New insights into host microbiome and genetic susceptibility may uncover new theories. More studies such as case-control designs suited for rare diseases and registries are needed.

CONCLUSIONS

The first annual AAO Think Tank acknowledged that the risk of microbial keratitis has not decreased over decades, despite innovation. Important questions and research directions remain.

Genetic Variation in Toll-Like Receptor 5 and Colonization with Flagellated Bacterial Vaginosis-Associated Bacteria

Bacterial vaginosis (BV) is a vaginal dysbiotic condition linked to negative gynecological and reproductive sequelae. Flagellated bacteria have been identified in women with BV, including Mobiluncus spp. and BV-associated bacterium-1 (BVAB1), an uncultivated, putatively flagellated species. The host response to flagellin mediated through Toll-like receptor 5 (TLR5) has not been explored in BV. Using independent discovery and validation cohorts, we examined the hypothesis that TLR5 deficiency-defined by a dominant negative stop codon polymorphism, rs5744168-is associated with an increased risk for BV and increased colonization with flagellated bacteria associated with BV (BVAB1, Mobiluncus curtisii, and Mobiluncus mulieris). TLR5 deficiency was not associated with BV status, and TLR5-deficient women had decreased colonization with BVAB1 in both cohorts. We stimulated HEK-hTLR5-overexpressing NF-κB reporter cells with whole, heat-killed M. mulieris or M. curtisii and with partially purified flagellin from these species; as BVAB1 is uncultivated, we used cervicovaginal lavage (CVL) fluid supernatant from women colonized with BVAB1 for stimulation. While heat-killed M. mulieris and CVL fluid from women colonized with BVAB1 stimulate a TLR5-mediated response, heat-killed M. curtisii did not. In contrast, partially purified flagellin from both Mobiluncus species stimulated a TLR5-mediated response in vitro We observed no correlation between vaginal interleukin 8 (IL-8) and flagellated BVAB concentrations among TLR5-sufficient women. Interspecies variation in accessibility of flagellin recognition domains may be responsible for these observations, as reflected in the potentially novel flagellin products encoded by Mobiluncus species versus those encoded by BVAB1.

Molecular determinants of disease severity in urinary tract infection

The most common and lethal bacterial pathogens have co-evolved with the host. Pathogens are the aggressors, and the host immune system is responsible for the defence. However, immune responses can also become destructive, and excessive innate immune activation is a major cause of infection-associated morbidity, exemplified by symptomatic urinary tract infections (UTIs), which are caused, in part, by excessive innate immune activation. Severe kidney infections (acute pyelonephritis) are a major cause of morbidity and mortality, and painful infections of the urinary bladder (acute cystitis) can become debilitating in susceptible patients. Disease severity is controlled at specific innate immune checkpoints, and a detailed understanding of their functions is crucial for strategies to counter microbial aggression with novel treatment and prevention measures. One approach is the use of bacterial molecules that reprogramme the innate immune system, accelerating or inhibiting disease processes. A very different outcome is asymptomatic bacteriuria, defined by low host immune responsiveness to bacteria with attenuated virulence. This observation provides the rationale for immunomodulation as a new therapeutic tool to deliberately modify host susceptibility, control the host response and avoid severe disease. The power of innate immunity as an arbitrator of health and disease is also highly relevant for emerging pathogens, including the current COVID-19 pandemic.

Comparative host transcriptome in response to pathogenic fungi identifies common and species-specific transcriptional antifungal host response pathways

Candidiasis, aspergillosis, and mucormycosis cause the majority of nosocomial fungal infections in immunocompromised patients. Using an unbiased transcriptional profiling in PBMCs exposed to the fungal species causing these infections, we found a core host response in healthy individuals that may govern effective fungal clearance: it consists of 156 transcripts, involving canonical and non-canonical immune pathways. Systematic investigation of key steps in antifungal host defense revealed fungal-specific signatures. As previously demonstrated, Candida albicans induced type I and Type II interferon-related pathways. In contrast, central pattern recognition receptor, reactive oxygen species production, and host glycolytic pathways were down-regulated in response to Rhizopus oryzae, which was associated with an ER-stress response. TLR5 was identified to be uniquely regulated by Aspergillus fumigatus and to control cytokine release in response to this fungus. In conclusion, our data reveals the transcriptional profiles induced by C. albicans, A. fumigatus, and R. oryzae, and describes both the common and specific antifungal host responses that could be exploited for novel therapeutic strategies.

Toll-like Receptors as Potential Therapeutic Targets in Kidney Diseases

Toll-like Receptors (TLRs) are members of pattern recognition receptors and serve a pivotal role in host immunity. TLRs response to pathogen-associated molecular patterns encoded by pathogens or damage-associated molecular patterns released by dying cells, initiating an inflammatory cascade, where both beneficial and detrimental effects can be exerted. Accumulated evidence has revealed that TLRs are closely associated with various kidney diseases but their roles are still not well understood. This review updated evidence on the roles of TLRs in the pathogenesis of kidney diseases including urinary tract infection, glomerulonephritis, acute kidney injury, transplant allograft dysfunction and chronic kidney diseases.

Recurrent urinary tract infection in women and overactive bladder - Is there a relationship?

Overactive bladder (OAB) in women has similar symptomatology with other common urologic diseases such as recurrent urinary tract infection (UTI). Recent evidence showed that chronic low-grade bacterial bladder colonization might exacerbate OAB symptoms and could be the etiology of recurrent UTI. The high prevalence of lower urinary tract dysfunction is associated with OAB. Women with urgency urinary incontinence refractory to antimuscarinic therapy had more bacteria and a more diverse urinary microbiome. The bacterial reside in the superficial urothelial cells to form intracellular bacterial community and outbreak when the host innate immunity is low. Women with recurrent UTI are found to have highly prevalent voiding dysfunction and detrusor overactivity. These functional abnormalities will further damage the urothelial barrier integrity and create vulnerable to uropathogen invasion. The defective urinary microbiota is less common in women with recurrent UTI, suggesting that the normal flora in the urine might inhibit uropathogen growth and invasion. The defective urothelial barrier function, deficient basal proliferation, and deficient maturation might be owing to chronic suburothelial inflammation, resulting in activation of sensory nerves (causing OAB) and failure elimination of intracellular bacterial communities (causing recurrent UTI). Precision diagnosis and multidisciplinary treatment of the underlying pathophysiology of OAB and recurrent UTI is necessary.

Association of variants in selected genes mediating host immune response with duration of Staphylococcus aureus bacteremia

Host genetic variation may be a contributing factor to variability in Staphylococcus aureus bacteremia duration. We assessed whether 28 single nucleotide polymorphisms (SNPs) in seven genes (TLR2, TLR4, TIRAP, IRAK4, TRAF6, NOD2, and CISH) that mediate host immune response were associated with S. aureus bacteremia duration. Subjects included 158 patients with short-term (≤4 days) and 44 with persistent (>4 days) S. aureus bacteremia from an academic medical center. In single SNP analyses, the minor allele frequencies of three TIRAP SNPs (rs655540, rs563011, and rs8177376) were higher in persistent bacteremia (P < 0.05). A haplotype with all three minor alleles was also associated with persistent bacteremia (P = 0.037). The minor allele frequencies of four other TIRAP SNPs (rs8177342, rs4937114, rs3802813, and rs4937115) were higher in short-term bacteremia (P < 0.05), and a haplotype containing the four minor alleles was associated with short-term bacteremia (P = 0.045). All seven SNPs are located in binding sites for proteins or noncoding RNAs that regulate transcription. None of the associations remained statistically significant after adjustment for multiple comparisons. Further investigation is needed to understand how genetic variation in TIRAP and other host immune genes may influence the duration of S. aureus bacteremia.

Rapid Bladder Interleukin-10 Synthesis in Response to Uropathogenic Escherichia coli Is Part of a Defense Strategy Triggered by the Major Bacterial Flagellar Filament FliC and Contingent on TLR5

Interleukin-10 is part of the immune response to urinary tract infection (UTI) due to E. coli, and it is important in the early control of infection in the bladder. Defining the mechanism of engagement of the immune system by the bacteria that enables the protective IL-10 response is critical to exploring how we might exploit this mechanism for new infection control strategies. In this study, we reveal part of the bacterial flagellar apparatus (FliC) is an important component that is sensed by and responsible for induction of IL-10 in the response to UPEC. We show this response occurs in a TLR5-dependent manner. Using infection prevention and control trials in mice infected with E. coli, this study also provides evidence that purified FliC might be of value in novel approaches for the treatment of UTI or in preventing infection by exploiting the FliC-triggered bladder transcriptome.

Urinary tract infection (UTI) caused by uropathogenic Escherichia coli (UPEC) engages interleukin-10 (IL-10) as an early innate immune response to regulate inflammation and promote the control of bladder infection. However, the mechanism of engagement of innate immunity by UPEC that leads to elicitation of IL-10 in the bladder is unknown. Here, we identify the major UPEC flagellar filament, FliC, as a key bacterial component sensed by the bladder innate immune system responsible for the induction of IL-10 synthesis. IL-10 responses of human as well as mouse bladder epithelial cell-monocyte cocultures were triggered by flagella of three major UPEC representative strains, CFT073, UTI89, and EC958. FliC purified to homogeneity induced IL-10 in vitro and in vivo as well as other functionally related cytokines, including IL-6. The genome-wide innate immunological context of FliC-induced IL-10 in the bladder was defined using RNA sequencing that revealed a network of transcriptional and antibacterial defenses comprising 1,400 genes that were induced by FliC. Of the FliC-responsive bladder transcriptome, altered expression of il10 and 808 additional genes were dependent on Toll-like receptor 5 (TLR5), according to analysis of TLR5-deficient mice. Examination of the potential of FliC and associated innate immune signature in the bladder to boost host defense, based on prophylactic or therapeutic administration to mice, revealed significant benefits for the control of UPEC. We conclude that detection of FliC through TLR5 triggers rapid IL-10 synthesis in the bladder, and FliC represents a potential immune modulator that might offer benefit for the treatment or prevention of UPEC UTI.

IMPORTANCE Interleukin-10 is part of the immune response to urinary tract infection (UTI) due to E. coli, and it is important in the early control of infection in the bladder. Defining the mechanism of engagement of the immune system by the bacteria that enables the protective IL-10 response is critical to exploring how we might exploit this mechanism for new infection control strategies. In this study, we reveal part of the bacterial flagellar apparatus (FliC) is an important component that is sensed by and responsible for induction of IL-10 in the response to UPEC. We show this response occurs in a TLR5-dependent manner. Using infection prevention and control trials in mice infected with E. coli, this study also provides evidence that purified FliC might be of value in novel approaches for the treatment of UTI or in preventing infection by exploiting the FliC-triggered bladder transcriptome.

Association of Toll-like 4 receptor gene polymorphism (rs4986790, rs4986791) with the risk of urinary tract infection: A systematic review and meta-analysis

Recently published studies had shown that there may be a potential link between the Single nucleotide polymorphism (SNP) of Toll-like receptor-4 (TLR4), and the risk of urinary tract infection (UTI); however, no consensus was reached. To further understand the relationship between TLR SNPs and urinary tract infections, we searched for related studies published in PubMed, EMBASE, and Web of Science before October 30, 2018, for further systematic review and meta-analysis. Our study accrued 10 case-control studies, which included 1476 urinary tract infection patients and 1449 healthy controls in TLR4(rs4986790, rs4986791). R3.4.2 and Stata 15.0 software were used for the analysis. In general, there was no statistically significant association between rs4986790 and urinary tract infection in the four genetic models. However, in the subgroup analysis, the Asian population showed significantly difference in the allelic model (G vs A: OR = 1.88 [95% CI:1.42-2.49], P = .03). In addition, there were also significant differences in the dominant model (GG + AG vs AA OR = 1.97 [95% CI:1.46-2.66], P = .01). Due to the small number of available literatures, no meaningful conclusion can be drawn regarding the relationship between TLR4 (rs4986791) and the risk of urinary tract infections in general. Nevertheless, our meta-analysis shows that in Asian populations, TLR4 (rs4986790) may be associated with risk of urinary tract infection.

Role of Toll-Like Receptor 5 (TLR5) in Experimental Melioidosis

The Gram-negative intracellular pathogen Burkholderia pseudomallei is the causative agent of melioidosis, an important cause of sepsis in Southeast Asia. Recognition of pathogen-associated molecular patterns by Toll-like receptors (TLRs) is essential for an appropriate immune response during pathogen invasion. In patients with melioidosis, TLR5 is the most abundantly expressed TLR, and a hypofunctional TLR5 variant has been associated with improved survival. Here, we studied the functional role of TLR5 and its ligand flagellin in experimental melioidosis. First, we observed differential TLR5 expression in the pulmonary and hepatic compartments upon infection with B. pseudomallei Next, we found that B. pseudomallei-challenged TLR5-deficient (Tlr5^-/- ) mice were more susceptible to infection than wild-type (WT) mice, as demonstrated by higher systemic bacterial loads, increased organ injury, and impaired survival. Lung bacterial loads were not different between the two groups. The phenotype was flagellin independent; no difference in in vivo virulence was observed for the flagellin-lacking mutant MM36 compared to the wild-type B. pseudomallei strain 1026b. Tlr5^-/- mice showed a similar impaired antibacterial defense when infected with MM36 or 1026b. Ex vivo experiments showed that TLR5-deficient macrophages display markedly impaired phagocytosis of B. pseudomallei In conclusion, these data suggest that TLR5 deficiency has a detrimental flagellin-independent effect on the host response against pulmonary B. pseudomallei infection.

Genital hygiene behaviors and practices: A cross-sectional descriptive study among antenatal care attendees

The female genital tracts harbor a wide variety of microorganisms’ knowns as microflora mostly constituted by lactobacilli, involved in the healthy state of the vagina without causing infection. Urinary tract infections (UTI) are frequent in pregnant women due to physiological and anatomical changes that occur during pregnancy. These infections can result to disabilities or serious health problems both for the mother and the new-born. Vaginal douching has been reported among risky practices associate with UTIs. However, this remains debatable and contradictory when other studies report the benefit effects of vaginal cleaning in infection prevention. The aim of this study was to assess pregnant women behaviors and practices regarding genital hygiene. This was a cross sectional descriptive study conducted on exhaustive sample of pregnant women coming for antenatal visits in Lafé Sub-divisional Hospital (SDH) and Baleng Catholic Health Center (BCHC) between 16 and 30 September 2013. Data were collected using a paper based standardized questionnaire directly self-administered after obtain a free consent. Overall, 80 pregnant women were enrolled. The majority of them had attended at least primary education (97.5%; n=78/80) and many were lived in couple (81.25%; n=65/80). Almost one on three participants identified antenatal consultation (ANC) as a key element to be taken into account by pregnant women. 70.1% (n=56/80) of women declared wearing undergarments in cotton. Regarding the daily vaginal douching behaviors, the majority (76.3%; n=61/80) of participants used the recommended gynecological measure, while the remaining use self-prescribed measures. Both genital parts (vulva area and vagina) were cleaned and use of water was mostly cited (63.8%; n=51/80). Almost one participant on four (n=29/80) use antiseptic solutions for genital cleaning. Antiseptic solutions were associated with water in 34.5% of cases (n=10/29), and in 65.5% (n=19/29) of cases it was used only for the vagina. Our findings suggest that knowledge and genital hygiene cleaning practices are acceptable among our study population. Risky practices such as use of antiseptic solutions and synthetic underwear’s were reported. Skills of health care providers on good hygiene practices for pregnant should be improved and community-based communication strategies need to be implemented to reach all women of child bearing age.

The Role of TLR4 Asp299Gly and TLR4 Thr399Ile Polymorphisms in the Pathogenesis of Urinary Tract Infections: First Evaluation in Infants and Children of Greek Origin

Urinary tract infections are one of the most common and serious bacterial infections in a pediatric population. So far, they have mainly been related to age, gender, ethnicity, socioeconomic level, and the presence of underlying anatomical or functional, congenital, or acquired abnormalities. Recently, both innate and adaptive immunities and their interaction in the pathogenesis and the development of UTIs have been studied. The aim of this study was to assess the role and the effect of the two most frequent polymorphisms of TLR4 Asp299Gly and Thr399Ile on the development of UTIs in infants and children of Greek origin. We studied 51 infants and children with at least one episode of acute urinary tract infection and 109 healthy infants and children. We found that 27.5% of patients and 8.26% of healthy children carried the heterozygote genotype for TLR4 Asp299Gly. TLR4 Thr399Ile polymorphism was found to be higher in healthy children and lower in the patient group. No homozygosity for both studied polymorphisms was detected in our patients. In the group of healthy children, a homozygote genotype for TLR4 Asp299Gly (G/G) as well as for TLR4 Thr399Ile (T/T) was showed (1.84% and 0.92 respectively). These results indicate the role of TLR4 polymorphism as a genetic risk for the development of UTIs in infants and children of Greek origin.

Toll-like receptor-4 299Gly allele is associated with Guillain-Barré syndrome in Bangladesh

Objective

TLR4 plays an important role in the pathogenesis of Guillain‐Barré syndrome (GBS). The relationships between TLR4 polymorphisms and susceptibility to GBS are poorly understood. We investigated the frequency and assessed the association of two single nucleotide polymorphisms (SNPs) in the extracellular domain of TLR4 (Asp299Gly and Thr399Ile) with disease susceptibility and the clinical features of GBS in a Bangladeshi cohort.

Methods

A total of 290 subjects were included in this study: 141 patients with GBS and 149 unrelated healthy controls. The TLR4 polymorphisms Asp299Gly and Thr399Ile were genotyped using polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) assay.

Results

The minor 299Gly allele was significantly associated with GBS susceptibility (P = 0.0137, OR = 1.97, 95% CI = 1.17–3.31), and was present at a significantly higher frequency in patients with the acute motor axonal neuropathy (AMAN) subtype of GBS (P = 0.0120, OR = 2.37, 95% CI = 1.26–4.47) than acute inflammatory demyelinating polyneuropathy (AIDP) subtype (P = 0.961, OR = 1.15, 95% CI = 0.38–3.48); when compared to healthy controls. The genotype frequency of the Asp299Gly polymorphism was not significantly different between patients with GBS and healthy controls. The Asp299‐Thr399 haplotype was associated with a significantly lower risk of developing GBS (P = 0.0451, OR = 0.63, 95% CI = 0.40–0.99). No association was observed between the Thr399Ile polymorphism and GBS disease susceptibility.

Interpretation

The TLR4 minor 299Gly allele was associated with increased susceptibility to GBS and the axonal GBS subtype in the Bangladeshi population. However, no associations were observed between the genotypes of the Asp299Gly and Thr399Ile SNPs and antecedent C. jejuni infection or disease severity in Bangladeshi patients with GBS.

Calcineurin inhibitor Tacrolimus impairs host immune response against urinary tract infection

Calcineurin inhibitor Tacrolimus, is a potent immunosuppressive drug widely used in order to prevent acute graft rejection. Urinary tract infection (UTI) is the most frequent infectious complication in renal transplant patients and long-term use of Tacrolimus might be involved in higher susceptibility to bacterial infections. It remains largely unknown how Tacrolimus affects the host innate immune response against lower and upper UTI. To address this issue, we used experimental UTI model by intravesical inoculation of uropathogenic E.coli in female wild-type mice pre-treated with Tacrolimus or solvent (CTR). We found that Tacrolimus pre-treated mice displayed higher bacterial loads (cystitis, pyelonephritis and bacteremia) than CTR mice. Granulocytes from Tacrolimus pre-treated mice phagocytized less E. coli, released less MPO and expressed decreased levels of CXCR2 receptor upon infection. Moreover, Tacrolimus reduced TLR5 expression in bladder macrophages during UTI. This immunosuppressive state can be explained by the upregulation of TLR-signaling negative regulators (A20, ATF3, IRAK-M and SOCS1) and parallel downregulation of TLR5 as observed in Tacrolimus treated granulocytes and macrophages. We conclude that Tacrolimus impairs host innate immune responses against UTI.

Are toll-like receptors potential drug targets for atherosclerosis? Evidence from genetic studies to date

Low-density lipoprotein cholesterol lowering, most notably via statin therapy, has successfully reduced the burden of coronary artery disease (CAD) in recent decades. However, the residual risk remaining even after aggressive lipid lowering has renewed interest in alternative targets. Anti-inflammatory drugs are thought to have much potential in this context, but side effects associated with long-term use of conventional anti-inflammatories, such as NSAIDs and glucocorticoids, preclude their use as preventive agents for CAD. Evidence from epidemiological studies and murine models of atherosclerosis suggests that toll-like receptors (TLRs) may have utility as targets for more focused anti-inflammatories, but it remains unclear if this pathway is causally related to CAD in man. Here, we review recent insight into this question gained from genetic studies of cardiovascular risk and innate immune function, focussing on the potential of Mendelian randomisation approaches based on intracellular-signalling pathways to identify and prioritise targets for drug development.

Association between TLR4 polymorphisms (896 A>G, 1196 C>T, - 2570 A>G, - 2081 G>A) and virulence factors in uropathogenic Escherichia coli

Escherichia coli is the main etiological agent of urinary tract infections. Its virulence factors are important during the initial interaction stage with the host as they enable colonization of urinary tract tissues. The genetic markers evidencing susceptibility to develop recurrent infections have been previously described. Toll-like receptors are critical sensors of microbial attacks, and they are also effectors of the individual's innate defense for elimination of pathogens. The aim of this study was to evaluate the association between functional polymorphisms (896 A>G, 1196 C>T, - 2570 A>G, - 2081 G>A) and susceptibility to develop urinary tract infections as well as E. coli virulence factors. This study includes 100 samples from patients diagnosed with UTI and 100 samples from uninfected subjects. A conventional urine culture was performed and the isolates were identified by using the Vitek automated system. TLR4 gene polymorphisms were identified by the PCR-RFLP technique. The hlyA, fimH, papC, iutA and cnf1 virulence factors as well as the E. coli phylogenetic group were assessed by PCR. In this study, it was observed that the presence of the - 2570 polymorphism represents a risk of UTI (p < 0.01), whereas - 2081 confers protection (p < 0.01). The 896A>G and 1196C>T polymorphisms were associated with the E. coli virulence factors fimH and hlyA, respectively (p < 0.05). The B2 group was the most frequent in clinical isolates (51%), and it displayed more virulence factors regarding other phylogenetic groups (p ≤ 0.05). An interesting finding was that strains considered as commensals, belonging to groups A and B1, can cause UTI and present virulence factors. Polymorphisms occurring in the TLR4 promoter region are correlated with susceptibility or risk of UTI, whereas structural polymorphisms are associated with the recognition of virulence factors displayed by E. coli.

Functional expression of TLR5 of different vertebrate species and diversification in intestinal pathogen recognition

Toll-like receptor 5 (TLR5) is activated by bacterial flagellins and plays a crucial role in the first-line defence against pathogenic bacteria and in immune homeostasis, and is highly conserved in vertebrate species. However, little comparative information is available on TLR5 functionality. In this study, we compared TLR5 activation using full-length and chimeric TLR5 of various vertebrate species (human, chicken, mouse, pig, cattle). Chimeric TLR5 receptors, consisting of human transmembrane and intracellular domains, linked to extracellular domains of animal origin, were generated and expressed. The comparison of chimeric TLR5s and their full-length counterparts revealed significant functional disparities. While porcine and chicken full-length TLR5s showed a strongly reduced functionality in human cells, all chimeric receptors were functional when challenged with TLR5 ligand Salmonella FliC. Using chimeric receptors as a tool allowed for the identification of ectodomain-dependent activation potential and partially host species-specific differences in response to various enteric bacterial strains and their purified flagellins. We conclude that both the extra- and intracellular determinants of TLR5 receptors are crucial for compatibility with the species expression background and hence for proper receptor functionality. TLR5 receptors with a common intracellular domain provide a useful system to investigate bacteria- and host-specific differences in receptor activation.

Infección del tracto urinario en niños, una de las enfermedades infecciosas más prevalentes

La infección del tracto urinario (ITU) es una patología frecuente en la infancia y una de las causas más comunes de consulta en el servicio de urgencias pediátricas. Las manifestaciones clínicas pueden ser inespecíficas en los lactantes y niños pequeños; sin embargo, en los niños mayores la sintomatología es más específica, con la aparición de fiebre, dolor en flanco, puño percusión renal positiva y signos de irritación vesical como disuria, polaquiuria, tenesmo e incontinencia. El diagnóstico definitivo confirmatorio se realiza mediante cultivo de orina. El conocimiento sobre los factores de riesgo, junto con ciertas consideraciones de valoración clínica y epidemiologia, son esenciales para encaminar las estrategias preventivas de las infecciones urinarias.

High molecular weight hyaluronic acid: a two-pronged protectant against infection of the urogenital tract?

OBJECTIVES

Recurrent urinary tract infections are associated with uropathogenic Escherichia coli (UPEC) ascending and infecting the urinary tract. Antibiotics provide only symptomatic relief, not prevent recurrence. Clinical evidence suggests that intravesical glycosaminoglycan therapy, such as hyaluronic acid (HA), helps reduce UTI recurrence. This has been investigated here using in vitro systems modelling the urogenital tract tissues.

METHODS

RT4 bladder cells were preconditioned with high molecular weight HA (> 1500 kDa) at 2 mg mL-1 and challenged with UPEC to analyse barrier protection and bacterial adherence. Untreated and HA-preconditioned VK2 E6/E7 vaginal cells were challenged with E. coli flagellin (50 ng mL-1) to mimic bacterial challenge, and media analysed for lipocalin-2, human β-defensin 2 and interleukin-8 by ELISA. Experiments were repeated after siRNA knockdown of Toll-like receptors 2, 4 and 5, and CD44 to investigate signalling.

RESULTS

Microscopic analyses showed reduced bacterial adherence and urothelial disruption with HA, suggesting that HA functions as a barrier protecting the epithelium from bacterial infection. Cells treated with HA and flagellin simultaneously produced more of the host antimicrobial peptide LCN2 and pro-inflammatory IL-8 (P < 0.05) compared to the no HA/flagellin challenges. Increased gene expression of DEFB4 (P < 0.05), but not the hBD2 peptide, was observed in the HA/flagellin-challenged cells.

CONCLUSION

These data suggest that exogenous HA has potential to protect the urogenital epithelia from UPEC infection via a two-pronged approach that involves the physical enhancement of the epithelial barrier and augmentation of its innate immune response.

TLR5 rs5744174 gene polymorphism is associated with the virus etiology of infant bronchiolitis but not with post-bronchiolitis asthma

BACKGROUND AND AIM

Bronchiolitis is a leading cause of hospitalization in infants and is associated with a risk of subsequent asthma. The innate immunity genes, such as those encoding toll-like receptors (TLRs), are likely to play a role in bronchiolitis and post-bronchiolitis outcome. Thus far, only one study has considered TLR5 genes in respiratory syncytial virus (RSV) bronchiolitis. The aim of this study was to investigate the association of TLR5 gene polymorphism with virus etiology and severity of bronchiolitis, and with post-bronchiolitis asthma.

METHODS

We recruited 164 infants (age < 6 months) hospitalized for bronchiolitis in this study and determined TLR5 rs5744174 (C > T) single nucleotide polymorphism, virus etiology and severity markers of bronchiolitis, and presence of post-bronchiolitis asthma until age 11 to 13 years.

RESULTS

RSV was detected in 113 (68.9%), rhinovirus in 19 (11.6%), and some other virus in 20 (12.2%) cases. Non-RSV etiology was more common among infants with the variant CT or TT genotype in the TLR5 rs5744174 gene than in those with the CC genotype (89.7% vs 71.7%, P = 0.03). TLR5 rs5744174 polymorphism was not associated with the need of supplementary oxygen or feeding support, with the length of hospital stay, or with post-bronchiolitis asthma at any age.

CONCLUSION

The TLR5 rs5744174 variant genotype may increase the susceptibility to bronchiolitis not caused by RSV.

Toll-like receptor 2, 4 and 9 polymorphisms and their association with ICU-acquired infections in Central Greece

PURPOSE

To test the potential of four common Toll-like receptor (TLR) polymorphisms to predispose to specific intensive care unit (ICU)-acquired infections and affect outcomes in a Greek ICU.

MATERIALS AND METHODS

The incidence of TLR2-Arg753Gln, TLR4-Asp299Gly, TLR4-Thr399Ile and TLR9-T1237C polymorphisms, and their association with ICU-acquired infections and patients' clinical outcomes were prospectively evaluated The examined genetic polymorphisms were assessed by real-time Polymerase-Chain-Reaction (PCR).

RESULTS

During a 15-month period, 224 patients were enrolled and genotyped. The prevalence of genetic polymorphisms for TLR4-Asp299Gly, TLR4-Thr399Ile, mixed TLR4-Asp299Gly/Thr399Ile, TLR9-T1237C and TLR2-Arg753Gln was 14.4%, 14.7%, 11.2%, 24.5% and 2.2%, respectively. TLR4 polymorphisms were associated with increased susceptibility towards specific ICU-acquired infections, i.e. Gram-negative central-nervous-system infections (CNSI), ventilator-associated pneumonia (VAP) and urinary-tract infections (UTI), principally due to multi-drug resistant (MDR) Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumonia, respectively (all P < 0.05). TLR9-T1237C polymorphism was associated with lower incidence and fewer relapses of CNSIs and UTIs when compared to mixed TLR4-Asp299Gly/Thr399Ile polymorphism group (P ≤ 0.039). ICU-stay was significantly prolonged in TLR4 polymorphisms (P ≤ 0.0416).

CONCLUSIONS

Common TLR-signaling polymorphisms might be implicated in the clinical phenotype of ICU-acquired infections in Central Greece. The possible impact of TLR4 polymorphisms on enhanced susceptibility towards Gram-negative MDR-infections in defined critical-disease states warrants further investigation. Trial Registration Clinical Trials.gov identifier: NCT00932243.

Toll-like receptors in immunity and inflammatory diseases: Past, present, and future

The immune system is a very diverse system of the host that evolved during evolution to cope with various pathogens present in the vicinity of environmental surroundings inhabited by multicellular organisms ranging from achordates to chordates (including humans). For example, cells of immune system express various pattern recognition receptors (PRRs) that detect danger via recognizing specific pathogen-associated molecular patterns (PAMPs) and mount a specific immune response. Toll-like receptors (TLRs) are one of these PRRs expressed by various immune cells. However, they were first discovered in the Drosophila melanogaster (common fruit fly) as genes/proteins important in embryonic development and dorso-ventral body patterning/polarity. Till date, 13 different types of TLRs (TLR1-TLR13) have been discovered and described in mammals since the first discovery of TLR4 in humans in late 1997. This discovery of TLR4 in humans revolutionized the field of innate immunity and thus the immunology and host-pathogen interaction. Since then TLRs are found to be expressed on various immune cells and have been targeted for therapeutic drug development for various infectious and inflammatory diseases including cancer. Even, Single nucleotide polymorphisms (SNPs) among various TLR genes have been identified among the different human population and their association with susceptibility/resistance to certain infections and other inflammatory diseases. Thus, in the present review the current and future importance of TLRs in immunity, their pattern of expression among various immune cells along with TLR based therapeutic approach is reviewed.

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TLRs are first described PRRs that revolutionized the biology of host-pathogen interaction and immune response

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The discovery of different TLRs in humans proved milestone in the field of innate immunity and inflammation

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The pattern of expression of all the TLRs expressed by human immune cells

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An association of various TLR SNPs with different inflammatory diseases

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Currently available drugs or vaccines based on TLRs and their future in drug targeting along with the role in reproduction, and regeneration

Compartmentalized Antimicrobial Defenses in Response to Flagellin

Motility is often a pathogenicity determinant of bacteria targeting mucosal tissues. Flagella constitute the machinery that propels bacteria into appropriate niches. Besides motility, the structural component, flagellin, which forms the flagella, targets Toll-like receptor 5 (TLR5) to activate innate immunity. The compartmentalization of flagellin-mediated immunity and the contribution of epithelial cells and dendritic cells in detecting flagellin within luminal and basal sides are highlighted here, respectively. While a direct stimulation of the epithelium mainly results in recruitment of immune cells and production of antimicrobial molecules, TLR5 engagement on parenchymal dendritic cells can contribute to the stimulation of innate lymphocytes such as type 3 innate lymphoid cells, as well as T helper cells. This review, therefore, illustrates how the innate and adaptive immunity to flagellin are differentially regulated by the epithelium and the dendritic cells in response to pathogens that either colonize or invade mucosa.

TLR1 polymorphism rs4833095 as a risk factor for IgA nephropathy in a Chinese Han population: A case-control study

Toll-like receptors (TLRs) are a family of transmembrane receptors, and play a vital role in recognizing invading pathogens and activating innate immunity. Previous studies indicated that TLR1 single nucleotide polymorphisms (SNPs) might be associated with the risk of IgA nephropathy (IgAN). This study aims to investigate the relationship between TLR1 SNPs (rs4833095 and rs5743557) and IgAN in a Chinese Han population. This case-control study included 351 patients with IgAN and 310 healthy controls. Two SNPs (rs4833095 and rs5743557) of TLR1 were genotyped by Sequenom MassARRAY. Odds ratios (OR) with 95% confidence intervals (CI) were used to assess the relationship with IgAN. We found that both allele and genotype frequencies of rs5743557 were not associated with IgAN risk. Rs4833095 increased IgAN risk compared with controls in the allele, dominant and log-additive models (P = 0.04, 0.04 and 0.03, respectively). Further haplotype analysis revealed that the T_rs4833095T_rs5743557 haplotype may be a risk factor for IgAN (OR = 1.28; 95% CI = 1.01–1.63; P = 0.046). Furthermore, rs4833095 was associated with Lee's grades (OR = 1.75; 95% CI = 1.03–2.96; P = 0.04). However, there was no significant association between the genotype distributions of rs5743557 and clinical parameters of IgAN such as gender, 24 hour urine protein, blood pressure, and Lee's grades. Taken together, these findings suggest that the TLR1 rs4833095 polymorphism may play a role in the development and progression of IgAN.

Bacterial virulence phenotypes of Escherichia coli and host susceptibility determine risk for urinary tract infections

Urinary tract infections (UTIs) are caused by uropathogenic Escherichia coli (UPEC) strains. In contrast to many enteric E. coli pathogroups, no genetic signature has been identified for UPEC strains. We conducted a high-resolution comparative genomic study using E. coli isolates collected from the urine of women suffering from frequent recurrent UTIs. These isolates were genetically diverse and varied in their urovirulence, that is, their ability to infect the bladder in a mouse model of cystitis. We found no set of genes, including previously defined putative urovirulence factors (PUFs), that were predictive of urovirulence. In addition, in some patients, the E. coli strain causing a recurrent UTI had fewer PUFs than the supplanted strain. In competitive experimental infections in mice, the supplanting strain was more efficient at colonizing the mouse bladder than the supplanted strain. Despite the lack of a clear genomic signature for urovirulence, comparative transcriptomic and phenotypic analyses revealed that the expression of key conserved functions during culture, such as motility and metabolism, could be used to predict subsequent colonization of the mouse bladder. Together, our findings suggest that UTI risk and outcome may be determined by complex interactions between host susceptibility and the urovirulence potential of diverse bacterial strains.

Bacterial lipoproteins and other factors released by Francisella tularensis modulate human neutrophil lifespan: Effects of a TLR1 SNP on apoptosis inhibition

Francisella tularensis infects several cell types including neutrophils, and aberrant neutrophil accumulation contributes to tissue destruction during tularaemia. We demonstrated previously that F. tularensis strains Schu S4 and live vaccine strain markedly delay human neutrophil apoptosis and thereby prolong cell lifespan, but the bacterial factors that mediate this aspect of virulence are undefined. Herein, we demonstrate that bacterial conditioned medium (CM) can delay apoptosis in the absence of direct infection. Biochemical analyses show that CM contained F. tularensis surface factors as well as outer membrane components. Our previous studies excluded roles for lipopolysaccharide and capsule in apoptosis inhibition, and current studies of [¹⁴C] acetate‐labelled bacteria argue against a role for other bacterial lipids in this process. At the same time, studies of isogenic mutants indicate that TolC and virulence factors whose expression requires FevR or MglA were also dispensable, demonstrating that apoptosis inhibition does not require Type I or Type VI secretion. Instead, we identified bacterial lipoproteins (BLPs) as active factors in CM. Additional studies of isolated BLPs demonstrated dose‐dependent neutrophil apoptosis inhibition via a TLR2‐dependent mechanism that is significantly influenced by a common polymorphism, rs5743618, in human TLR1. These data provide fundamental new insight into pathogen manipulation of neutrophil lifespan and BLP function.

Testing an association between TLR4 and CXCR1 gene polymorphisms with susceptibility to urinary tract infection in type 2 diabetes in north Indian population

BACKGROUND

Genetic variations of Toll like receptor 4 (TLR4) and CXC-chemokine receptor type1 (CXCR1), the key elements of innate immune system and their association with urinary tract infection (UTI) were studied in general population. In present study we investigate genetic variation of these genes in diabetic patients (3 to 4 times higher prevalence of UTI in comparison to general population).

METHODS

A total 1100 subjects (318 diabetic patients with UTI, 324 diabetic patients without UTI, 200 non-diabetic UTI patients and 260 age matched healthy control) were enrolled in the study. SNPs of TLR4 rs4986790, rs4986791 and CXCR1 rs2234671 was assessed by PCR-RFLP and PCR-SSP respectively.

RESULTS

Statistical analysis revealed that A/G genotype and G allele of TLR4 rs4986790 are significantly associated with UTI in both diabetics and nondiabetic patients in comparison to healthy control. Similarly CT genotype and T allele of TLR4 rs4986791 are also significantly associated with UTI in both groups. We also found that prevalence of A/G genotype of TLR4 rs4986790 and CT genotype of TLR4 rs4986791 are significantly higher in patients of diabetes with UTI in comparison to diabetic patients without UTI. We did not find any association of CXCR1 rs2234671 polymorphism with UTI by comparing with any group.

CONCLUSION

We found that TLR4 rs4986790 and rs4986791 gene polymorphism is a risk for UTI development in both diabetic and nondiabetic patients in north Indian population.