TLR4 and LPS hyporesponsiveness in humans

Association of TLR4 gene rs4986790 and rs4986791 polymorphisms with asthma susceptibility: meta-analysis and trial sequential analysis

BACKGROUND

The current understanding of the correlation between TLR4 gene (toll-like receptor 4) rs4986790 and rs4986791 polymorphisms and asthma susceptibility is inconclusive, with studies and populations yielding conflicting results.

OBJECTIVES

Evaluate this relationship using meta-analysis and trial sequential analysis (TSA).

PATIENTS AND METHODS

Databases were systematically queried for relevant articles from the establishment of the database to 19 June 2023 adhering to predefined inclusion and exclusion criteria. Two authors independently conducted screening, data extraction, and quality evaluation. Meta-analysis and TSA were carried out using RevMan 5.4, StataMP 17.0, and TSA 0.9.5.10 Beta, with α=0.05. Subgroup analyses were conducted based on racial demographics. A sensitivity analysis was conducted employing a one-by-one exclusion method. Publication bias was assessed using the Begg and Egger tests.

MAIN OUTCOME MEASURES

Association of asthma susceptibility with TLR4 gene rs4986790 and rs4986791 polymorphisms.

SAMPLE SIZE

23 articles included 22 studies on the rs4986790 polymorphism and 11 studies on the rs4986791 polymorphism on the TLR4 gene.

RESULTS

Out of 692 studies screened, 23 met the inclusion criteria. While the overall meta-analysis showed no significant association between the TLR4 rs4986790 polymorphism and asthma susceptibility, subgroup analysis revealed a significant link in the Caucasian population. A significant association was noted in the meta-analysis, particularly among Asian populations, on the rs4986791 polymorphism. The sensitivity analysis indicated that the meta-analysis results were relatively stable. Publication bias analysis revealed minimal influence from publication bias. However, TSA was underscored by the necessity for additional original studies to further validate specific outcomes.

CONCLUSIONS

Our study underscores the ethnicity-specific impact on the relationship between TLR4 polymorphisms and asthma susceptibility. While the overall findings for rs4986790 were not significant, the association with the Caucasian population merits further investigation. Furthermore, rs4986791 demonstrated a significant correlation with asthma susceptibility, specifically among Asian populations.

LIMITATIONS

Our study predominantly examined the rs4986790 and rs4986791 polymorphisms, overlooking the potential influence of other genetic variants within TLR4.

Lessons from Dairy Farmers for Occupational Allergy and Respiratory Disease

PURPOSE OF REVIEW

Exposure to bioaerosols at dairies has long been associated with allergy, respiratory disease, and decreases in lung function. Recent advancements in exposure assessments have aided our understanding on the size distribution and composition of these bioaerosols, but investigations focusing solely on exposures may overlook important intrinsic factors impacting worker's susceptibility to disease.

RECENT FINDINGS

In our review, we discuss the most recent studies examining the exposures and genetic factors that contribute to occupational disease in dairy work. We also review more recent concerns in livestock work associated with zoonotic pathogens, antimicrobial resistant genes, and the role of the human microbiome. The studies highlighted in this review demonstrate the need for further research to better understand bioaerosol exposure-response relationships in the context of extrinsic and intrinsic factors, antibiotic-resistant genes, viral pathogens, and the human microbiome to help inform effective interventions that improve respiratory health among dairy farmers.

First-in-human phase I clinical trial of a TLR4-binding DNA aptamer, ApTOLL: Safety and pharmacokinetics in healthy volunteers

ApTOLL is an aptamer that antagonizes Toll-like receptor 4 and improves functional outcomes in models of ischemic stroke and myocardial infarction. The aim of this study was to characterize the safety and pharmacokinetics of ApTOLL in healthy volunteers. A first-in-human dose-ascending, randomized, placebo-controlled phase I clinical trial to assess safety and pharmacokinetics of ApTOLL (30-min infusion intravenously) was performed in 46 healthy adult male volunteers. The study was divided into two parts: part A included seven single ascending dose levels, and part B had one multiple dose cohort. Safety and pharmacokinetic parameters were evaluated. No serious adverse events or biochemistry alterations were detected at any dose nor at any administration pattern studied. Maximum concentration was detected at the end of the infusion and mean half-life was 9.3 h. Interestingly, exposure increased in the first four levels receiving doses from 0.7 mg to 14 mg (AUC of 2,441.26 h∗ng/mL to 23,371.11 h∗ng/mL) but remained stable thereafter (mean of 23,184.61 h∗ng/mL after 70 mg). Consequently, the multiple dose study did not show any accumulation of ApTOLL. These results show an excellent safety and adequate pharmacokinetic profile that, together with the efficacy demonstrated in nonclinical studies, provide the basis to start clinical trials in patients.

In vivo lung perfusion rehabilitates sepsis-induced lung injury

BACKGROUND

Sepsis is the leading cause of lung injury in adults and can lead to acute respiratory distress syndrome (ARDS). Using a novel technique of isolated in vivo lung perfusion (IVLP), we hypothesized that normothermic IVLP will improve oxygenation and compliance in a porcine model of sepsis-induced lung injury.

METHODS

Mature adult swine (n = 8) were administered lipopolysaccharide (LPS; 50 μg/kg over 2 hours) via the external jugular vein, followed by sternotomy and central extracorporeal membrane oxygenation (ECMO) cannulation (right atrium to ascending aorta). The left pulmonary artery (inflow) and left superior and inferior pulmonary veins (outflow) were dissected out and cannulated to deliver isolated perfusion to the left lung. After 4 hours of normothermic IVLP with Steen solution, the left lung then underwent 4 hours of reperfusion after IVLP decannulation. Airway pressures and lung-specific pulmonary vein blood gases from the right lung (LPS control) and left lung (LPS + IVLP) of the same animal were compared.

RESULTS

All animals demonstrated a significant reduction in the ratio of partial pressure of oxygen in arterial blood (PaO₂)/fraction of inspired oxygen (FiO₂) (P/F ratio) and total lung compliance at 2 hours after the start of LPS infusion (mean, 469 ± 19.7 mm Hg vs 222.2 ± 21.4 mm Hg; P < .0001). After reperfusion, 6 animals (75%) exhibited improved lung function, allowing for ECMO decannulation. Lung-specific oxygenation was superior in the left lung after 4 hours of reperfusion (mean, 310.5 ± 54.7 mm Hg vs 201.1 ± 21.7 mm Hg; P = .01). Similarly, total lung compliance improved after IVLP of the left lung. The lung wet weight to dry weight ratio demonstrated reduced edema in rehabilitated left lungs (mean, 6.5 ± 0.3 vs 7.5 ± 0.4; P = .04).

CONCLUSIONS

IVLP successfully rehabilitated LPS-injured lungs compared to ECMO support alone in this preclinical porcine model.

Genetic polymorphism in CD14 gene, a co-receptor of TLR4 associated with non-alcoholic fatty liver disease

AIM

To evaluate the pathogenic role of toll-like receptor (TLR) gene polymorphisms in patients with non-alcoholic fatty liver disease (NAFLD).

METHODS

Two hundred and fifty subjects (NAFLD = 200, healthy volunteers = 50) underwent polymerase chain reaction and restriction fragment length polymorphism to assess one polymorphism in the toll-like receptor 2 (TLR2) gene (A753G), two polymorphisms in the TLR4 gene (TLR4 Asp299Gly and Thr399Ile allele), and two polymorphisms in the cluster of differentiation 14 (CD14) (C-159T and C-550T) gene, a co-receptor of TLR4. Association of TLR gene polymorphisms with NAFLD and its severity was evaluated by genetic models of association.

RESULTS

On both multiplicative and recessive models of gene polymorphism association, there was significant association of CD14 C (-159) T polymorphism with NAFLD; patients with TT genotype had a 2.6 fold increased risk of developing NAFLD in comparison to CC genotype. There was no association of TLR2 Arg753Gln, TLR4 Asp299Gly, Thr399Ile, and CD14 C (-550) T polymorphisms with NAFLD. None of the TLR gene polymorphisms had an association with histological severity of NAFLD.

CONCLUSION

Patients with CD14 C (-159) T gene polymorphism, a co-receptor of TLR4, have an increased risk of NAFLD development.

Predictive Genomics of Adverse Events After Cardiac Surgery

Significant, yet highly individual, thrombotic and inflammatory responses to surgery provide an excellent opportunity for insight into the genomic impact upon a patient's postoperative course. Cardiac surgery elicits the most profound perioperative disturbance and is associated with the highest incidence of adverse outcomes of any elective surgical procedure. Thus, cardiac surgical patients are an ideal population in which to evaluate the influence of complex traits on perioperative morbidity and mortality. This review describes the application of fundamental genetics upon the occurrence of adverse outcomes after cardiac surgery and cardiac transplantation. Specific emphases include a brief primer of the principles of genetics concentrating on the effects of variation within the human genome upon clinical outcomes and the differences between so-called Mendelian traits and complex traits. Four important clinical diseases dealt with in this review as examples of the impact of genetic factors on clinical outcomes are the genetics of heparin-induced thrombocytopenia, heart transplantation rejection and vasculopathy, atrial fibrillation, and infection.

TLR4 preconditioning is associated with low success of OK-432 treatment for lymphatic malformations in children

PURPOSE

We have recently shown that the relative TLR4 expression on monocytes of low responding pediatric patients after OK-432 treatment is significantly reduced after stimulation with lipopolysaccharide (LPS) compared with high responding children. The aim of this study was to perform further analysis to explain this observation.

METHODS

Monocytes from children with high (HR, n = 5) and low response (LR, n = 6) after previous OK-432 treatment were stimulated with LPS for 20 h and analyzed with fluorescence-activated cell sorting (mean fluorescence intensity, MFI; level of significance P ≤ 0.05).

RESULTS

Mean MFI after LPS stimulation was comparable in both groups (HR 1142 ± 652 units, LR 839 ± 427 units, P = 0.85). Significant changes after LPS stimulation are explained by higher pre-stimulation values in the LR group compared with the HR group (950 ± 718 vs. 477 ± 341, P = 0.25) with considerable differences of the mean expression changes after LPS stimulation (HR 665 ± 683 vs. LR -111 ± 605, P = 0.08).

CONCLUSION

The previously shown reduced TLR4 upregulation on monocytes after LPS stimulation in the LR group compared with the HR group can be primarily explained by TLR preconditioning. This observation implies the use of absolute values with definite thresholds.

Systematic review of respiratory health among dairy workers

The dairy industry is changing on a global scale with larger, more efficient operations. The impact of this change on worker health and safety, specifically, associations between occupational lung disease and inhalation exposures, has yet to be reported in a comprehensive review of the scientific literature. Therefore, a three-tier process was used to identify information using a keyword search of online databases of scientific literature. Of the 147 citations reviewed, 52 met initial screening criteria, and 30 were included in this review. Dairy workers experience lung conditions such as asthma, chronic obstructive pulmonary disease, hypersensitivity pneumonitis, chronic bronchitis, and cancer. Recent pulmonary function studies have identified obstructive lung changes among dairy farm workers. The increased scale of dairy production with significant changes in technology and work practices has altered inhalation exposure patterns among dairy workers. The inhalation exposure in the dairy work environment may elicit differing inflammatory responses in relation to timing of initial exposure as well as to repeated exposures. Few studies have measured inhalation exposure while simultaneously assessing the impact of the exposure on lung function of dairy farm workers. Even fewer studies have been implemented to assess the impact of aerosol control technology to reduce inhalation exposure. Future research should evaluate worker exposure to aerosols through a task-based approach while utilizing novel methods to assess inhalation exposure and associated inflammatory responses. Finally, potential solutions should be developed and tested to reduce inhalation exposure to inflammatory agents and respiratory diseases in the dairy farm work environment.

Dynamic Toll-like receptor expression predicts outcome of sclerotherapy for lymphatic malformations with OK-432 in children

BACKGROUND

Sclerotherapy with OK-432 is recommended as a first-line treatment for lymphatic malformations. However, 40% of patients show poor response, defined by involution to <50% of the original size. It has been suggested that the OK-432 effect is highly dependent on the Toll-like receptor (TLR) 4-dependent expression of TLR7 in antigen-presenting cells. We hypothesized that the ability for TLR expression in monocytes after treatment with the TLR4-ligand lipopolysaccharide (LPS) can be used to predict successful OK-432 treatment.

METHODS

Blood was taken from children with low responder (LR, n = 6) and high responder (HR, n = 5) of previous OK-432 treatment. Monocytes were stimulated with LPS for 20 h. TLR expression was analyzed with fluorescence-activated cell sorting (mean fluorescence intensity). The level of significance was P ≤ 0.05.

RESULTS

The mean age of patients in the HR group was 1.4 ± 0.9 y and in the LR group 2.8 ± 2.9 y (P = 0.31). The mean TLR4 upregulation after LPS stimulation in the HR group was significantly higher than in the LR group (factor 3.6 versus factor 1 compared with nonstimulated controls; P = 0.037). The mean TLR7 expression did not show significant differences between the groups.

CONCLUSIONS

Dynamic TLR4 expression represents most probably a predictive parameter for the treatment of lymphatic malformations with OK-432 and should be further investigated.

Association of Toll-like receptor 2 gene polymorphisms with lung function in workers in swine operations

BACKGROUND

Workers in swine operations are exposed to indoor dusts and gases and are at increased risk of respiratory problems. Toll-like receptor (TLR) 2 recognizes ligands from gram-positive bacteria, whereas TLR4 responds to endotoxin from gram-negative bacteria.

OBJECTIVE

To investigate the effects of TLR2 and TLR4 polymorphisms on lung function in workers from swine operations and nonfarming rural dwellers.

METHODS

A total of 374 full-time workers from large swine operations and 411 nonfarming rural dwellers from Saskatchewan were included. Information on demography, lifestyle, and occupation, lung function measurements, and blood samples for genotyping were obtained from the participants. Multiple regression analysis and Bonferroni correction were used in the statistical analysis.

RESULTS

Workers with TLR2-16933T/A polymorphism (AA) had significantly greater mean values of lung function than workers with wild-type genotypes (AT+TT) after controlling for potential confounders (forced expiratory volume in 1 second, 3.7 vs 3.5 L; P=.009; forced expiratory flow between 25% and 75%, 3.7 vs 3.3 L; P=.003; predicted forced expiratory volume in 1 second; 100.3% vs 95.6%; P=.005; forced expiratory flow between 25% and 75%, 92.4% vs 83.4%; P=.009). These results were also observed for TLR2Arg677Trp polymorphism among the workers. No such significant differences were observed among nonfarming rural dwellers. For Asp299Gly and Thr399Ile polymorphisms in the TLR4 gene, no significant differences were observed in the mean lung function values between the polymorphic and wild-type groups in both workers and rural dwellers.

CONCLUSION

Our study is the first, to our knowledge, to report protective effects of TLR2 polymorphisms on lung function among workers in swine operations and raises the possibility that TLR2 polymorphisms are protective of airway disease in individuals exposed to gram-positive organisms in the inhaled airborne dust.

Pulmonary function reductions among potentially susceptible subgroups of agricultural workers in Colorado and Nebraska

OBJECTIVE

Organic dust inhalation has been associated with adverse respiratory responses among agricultural workers. We evaluated factors that may confer increased susceptibility to these health effects.

METHODS

We quantified personal work shift exposures to inhalable dust, endotoxin, and its 3-hydroxy fatty acid constituents, and evaluated changes in pulmonary function among 137 grain elevator, cattle feedlot, dairy, and corn farm workers.

RESULTS

Increased dust exposure was associated with work shift reductions in lung function. Although interpretation is limited because of small samples, a suggestion of stronger exposure-response relationships was observed among smokers, as well as workers reporting pesticide/herbicide application, asthma, or allergies, and those with genetic polymorphisms (TLR4) (Pinteraction ≤ 0.05).

CONCLUSIONS

A better understanding of factors leading to increased susceptibility of adverse respiratory outcomes is needed to optimize exposure reduction strategies and develop more comprehensive wellness programs.

New insight into immunity and immunopathology of Rickettsial diseases

Human rickettsial diseases comprise a variety of clinical entities caused by microorganisms belonging to the genera Rickettsia, Orientia, Ehrlichia, and Anaplasma. These microorganisms are characterized by a strictly intracellular location which has, for long, impaired their detailed study. In this paper, the critical steps taken by these microorganisms to play their pathogenic roles are discussed in detail on the basis of recent advances in our understanding of molecular Rickettsia-host interactions, preferential target cells, virulence mechanisms, three-dimensional structures of bacteria effector proteins, upstream signalling pathways and signal transduction systems, and modulation of gene expression. The roles of innate and adaptive immune responses are discussed, and potential new targets for therapies to block host-pathogen interactions and pathogen virulence mechanisms are considered.

Association of polymorphisms in the TLR4 gene with the risk of developing neutropenia in children with leukemia

Infections are a major cause of morbidity and mortality in children with acute lymphoblastic leukemia (ALL). Susceptibility to infections increases as the neutrophil count decreases. Despite identical treatment patients vary considerably in the number of neutropenic episodes. Toll-like receptor 4 (TLR4) has been shown to have a role in inhibiting apoptosis of neutrophils. Therefore, we hypothesized that polymorphisms in the TLR4 gene may influence the number of chemotherapy-induced neutropenic episodes. Eight single-nucleotide polymorphisms (SNPs) of the TLR4 gene were determined in 194 children aged 0-17 years, who were diagnosed with ALL. We compared the genotype distributions of the SNPs with the frequency of neutropenic episodes during treatment with chemotherapeutic regimens. The number of neutropenic episodes varied from 0 to 17, with a median of four neutropenic episodes. Four SNPs in the TLR4 gene (rs10759931, rs11536889, rs1927911 and rs6478317) were associated with an increased risk of developing chemotherapy-induced neutropenia, each sustaining correction for multiple testing. Further studies are required to elucidate whether pediatric patients with ALL with the particular SNPs in the TLR4 gene also experience more infections and would benefit from prophylactic antibiotic treatment, by a reduction of morbidity and mortality due to infections.

Endotoxin exposure and inflammation markers among agricultural workers in Colorado and Nebraska

The adverse respiratory effects of agricultural dust inhalation are mediated in part by endotoxin, a constituent of gram-negative bacterial cell walls. This study quantified personal work-shift exposures to inhalable dust, endotoxin, and its reactive 3-hydroxy fatty acid (3-OHFA) constituents among workers in grain elevators, cattle feedlots, dairies, and on corn farms. Exposures were compared with post-work-shift nasal lavage fluid inflammation markers and respiratory symptoms. Breathing-zone personal air monitoring was performed over one work shift to quantify inhalable dust (Institute of Medicine samplers), endotoxin (recombinant factor C [rFC] assay), and 3-OHFA (gas chromatography/mass spectrometry). Post-shift nasal lavage fluids were assayed for polymorphonuclear neutrophils (PMN), myeloperoxidase (MPO), interleukin 8 (IL-8), albumin, and eosinophilic cation protein (ECP) concentrations. The geometric mean (GSD) of endotoxin exposure (rFC assay) among the 125 male participants was 888 +/- (6.5) EU/m(3), and 93% exceeded the proposed exposure limit (50 EU/m(3)). Mean PMN, MPO, albumin, and ECP levels were two- to threefold higher among workers in the upper quartile of 3-OHFA exposure compared to the lowest exposure quartile. Even numbered 3-OHFA were most strongly associated with nasal inflammation. Symptom prevalence was not elevated among exposed workers, possibly due to endotoxin tolerance or a healthy worker effect in this population. This is the first study to evaluate the relationship between endotoxin's 3-OHFA constituents in agricultural dust and nasal airway inflammation. More research is needed to characterize the extent to which these agents contribute to respiratory disease among agricultural workers.

Association of the TLR4 Asp299Gly polymorphism with lung function in relation to body mass index

Background

Previous studies have shown conflicting results for the association between TLR4 polymorphism (Asp299Gly) and lung function. We investigated the influence of TLR4 Asp299Gly, a polymorphism, on lung function in a community population.

Methods

In 2003, a cross-sectional survey was conducted to assess the respiratory health of residents living in and around the town of Humboldt, Saskatchewan, Canada. There were 2090 adults age 18-79 years who completed a questionnaire that included a medical and smoking history, as well as socio-economic and lifestyle variables. Genetic information and lung function test measurements were available on 1725 subjects (754 males and 971 females) of the 2090 respondents. These subjects were selected for further analysis to investigate the association between TLR4 Asp299Gly genotype and forced expiratory volume in the first second in liters (FEV₁), forced vital capacity in liters (FVC), FEV₁/FVC ratio, and forced expiratory flow rate in liters/second (FEF_25-75). Multivariable linear regression analysis was used to investigate associations.

Results

Adjusted mean values of FEV₁ and FVC were significantly different between TLR4 wild type and TLR4 variant groups [Mean ± S.E.: (TLR4 wild type - FEV₁: 3.18 ± 0.02, FVC: 3.95 ± 0.03; TLR4 variant - FEV₁: 3.31 ± 0.06, FVC: 4.14 ± 0.07)]. Based on multivariable regression analysis, we observed that body mass index (BMI) was associated with decreased FEV₁/FVC ratio and FEF_25-75 in TLR4 variant group but not in wild type group.

Conclusion

BMI may modify the associations of TLR4 Asp299Gly polymorphism with FEV₁/FVC ratio and FEF_25-75.

Innate immune receptors on neutrophils and their role in chronic lung disease

Neutrophils, the prototypic cells of the innate immune system, are recruited to infected sites to protect the human body from invading pathogens. To accomplish this function, neutrophils sense pathogens and endogenous damage-associated molecules via innate immune receptors, such as Toll-like receptors (TLRs) and other pattern recognition receptors. This defence function is essential for the pulmonary microenvironment where the host is faced with millions of particles and pathogens inhaled daily. Chronic lung diseases, such as cystic fibrosis or chronic obstructive pulmonary disease are characterized by a neutrophil accumulation and chronic bacterial colonization of the airways. Consequently, insights into the role of TLRs on neutrophils in chronic lung diseases are of high relevance for further diagnostic and therapeutic approaches. Here we summarize and discuss recent advances in the expression, regulation and functional role of TLRs on neutrophils in chronic lung diseases.

[Polymorphisms of the Toll-like receptor 4 gene and their potential role in infectious diseases and chronic inflammatory disorders]

The Toll-like receptor 4 is a key mediator of the innate immune response. Besides its main ligand, the Gram-negative bacterial lipopolysaccharides, other molecules such as heat-shock protein 60, oxidized low density lipoprotein and fibronectin can also bind to the receptor. Activation of the Toll-like receptor induces the production of proinflammatory cytokines. There is increasing evidence showing that the Toll-like receptor 4 plays a role not only in the immune reaction against infectious agents but also in chronic non-infectious inflammatory diseases, such as atherosclerosis, diabetes mellitus and inflammatory bowel disease. This review briefly summarizes recent knowledge on the Toll-like receptor 4, its common co-segregation polymorphisms and the impact of these polymorphisms on various human diseases.

Association of polymorphisms of toll-like receptor 4 with a reduced prevalence of hay fever and atopy

BACKGROUND

The response to innate immune stimuli seems to be critical to conditioning adaptive immunity. Early exposure to endotoxin initiates immune responses that have been shown to alter the risk of asthma and allergic diseases. The toll-like receptor 4 (TLR4) gene encodes the principal innate immunity receptor in humans for bacterial endotoxin. Polymorphisms in the TLR4 gene may regulate the effects of endotoxin exposure and could play a role in the development of asthma and atopy-related phenotypes.

OBJECTIVE

To investigate the association between TLR4 polymorphisms and allergic phenotypes in nonsmokers.

METHODS

The data from 915 nonsmoking students were available for the study. The TLR4 299 and 399 polymorphisms were genotyped using mouthwash samples. The TLR4 299 and 399 polymorphisms were grouped together to define the TLR4 polymorphic group. Skin prick tests were conducted in a subgroup of healthy participants. A brief questionnaire was administered to determine demographic characteristics and chronic health conditions.

RESULTS

The prevalence of hay fever was 0% in the TLR4 polymorphic group and 7.5% in the wild-type group (P = .01). After controlling for age group and sex using logistic regression, the odds of having hay fever were reduced by 88% (P = .009) in the TLR4 polymorphic group compared with the wild-type group. In a subgroup analysis, the association between TLR4 polymorphisms and atopy was only observed among females.

CONCLUSIONS

To our knowledge, this study is the first to report an association between TLR4 polymorphisms and atopy-related phenotypes in a nonsmoking population. Further investigation of the role of TLR4 polymorphisms in asthma and atopy-related phenotypes is warranted.

Epistatic interactions are critical to gene-association studies: PAI-1 and risk for mortality after burn injury

Replication of statistically significant associations between single nucleotide polymorphisms (SNPs) and disease phenotypes has been problematic. One reason for conflicting observations may be failure to consider confounding factors, including gene-gene (epistatic) interactions. Our experience with the insertion/deletion polymorphism at -688 in the promoter region of plasminogen activator inhibitor (PAI-1) seems to support this contention and may foreshadow problems for genome-wide association scans, which tend to use unadjusted analytical methodologies. One hundred forty-nine patients with > or =15% total body surface area (TBSA) burns, without significant nonburn-related trauma (injury severity score < or =16), traumatic or anoxic brain injury or spinal cord injury who survived >48 hours postadmission were enrolled under a protocol approved by the UT Southwestern and Parkland Hospital IRBs. Clinical data were collected prospectively and candidate polymorphisms in PAI-1 (-688), toll-like receptor 4 (+896), CD14 (-159), tumor necrosis factor-alpha (-308), and interleukin-6 (-174) were genotyped. The PAI-1 SNP was significantly associated (P-value for trend = 0.036) with risk for death when evaluated in isolation by unadjusted analysis. However, after adjustment for potential confounders using multiple logistic regression, only age, full-thickness burn size, and CD14 genotype (as previously reported) were associated with increased mortality. Genetic association analyses should be adjusted for interactions between multiple SNPs, injury or disease characteristics, and demographic variables. Increasingly sophisticated analytical methods will be required as gene-mapping studies transition from a candidate-gene based approach to genome-wide association scans.

Methods used in clinical development of novel anti-asthma therapies

In recent years, it has become increasingly important to get as much as possible information on clinical efficacy already in the early phases of drug development. For proof of concept (POC) studies testing novel anti-inflammatory drugs in asthma, there are several validated exacerbation models, inducing various aspects of the airway inflammation and airway responsiveness. The choice of the appropriate asthma model depends on the drug's targets within the inflammatory process. For adequate assessment of the drug's anti-inflammatory potential, it is crucial to choose adequate (surrogate) biomarkers. Ideally, these should include measures of airway response, central and peripheral airway inflammation and airway hyperresponsiveness. Overall, there are validated non-invasive sampling techniques for the measurement of inflammatory markers in asthma that can be applied as outcome parameters in early clinical trials. If adequately implemented, these measurements can provide early indication of proof of pharmacological and potential therapeutic efficacy-even in first administration to humans.

CD14-159 C allele is associated with increased risk of mortality after burn injury

Although comprehension of postburn pathophysiology has grown in recent years, we are still unable to accurately identify burn patients who are at an increased risk of infectious complications and death. This unexplained variation is likely influenced by heritable factors; the genetic predisposition for death from infection has been estimated as greater than that for cardiovascular disease or cancer. Identify genetic variants associated with increased mortality after burn injury. A total of 233 patients with burns of 15% of total body surface area or greater or smoke inhalation injury who survived more than 48 h after admission and were without significant nonburn-related trauma (injury severity score > or = 16), traumatic or anoxic brain injury, or spinal cord injury. We examined the influence of genotype at five candidate loci (interleukin [IL]-1beta, IL-6, tumor necrosis factor-alpha, toll-like receptor 4, CD14) on mortality risk after burn injury. DNA was isolated from residual blood from laboratory draws and candidate genotypes were determined by real-time polymerase chain reaction using TaqMan probes. Clinical data were prospectively collected into a local, curated database. Allelic associations were analyzed by multivariate logistic regression. After adjustment for age, full-thickness burn size, inhalation injury, ethnicity, and sex, carriage of the CD14-159 C allele imparted at least a 1.3-fold increased risk for death after burn injury, relative to TT homozygotes (adjusted odds ratio, 2.9; 95% confidence interval, 1.3-6.8; P = 0.01). This association was stronger (adjusted odds ratio, 3.3; 95% confidence interval, 1.3-8.4; P = 0.01) when the analysis was conducted only on deaths accompanied by severe sepsis. In addition, a gene dosage effect for increased mortality was apparent for carriage of the CD14-159 C allele (P = 0.006). The gene dosage effect remained when white, Hispanic, or African American patients were analyzed independently, although statistical significance was not achieved in the subgroup analysis. None of the other single nucleotide polymorphisms examined were significantly associated with mortality. These data provide strong evidence that a CD14 promoter allele that is known to impart lower baseline and induced CD14 transcription also affects mortality risk after burn injury. A potential (although untested) mechanism for our observation is that reduced signaling through CD14/toll-like receptor 4 in response to challenge by gram-negative bacteria after burns results in a blunted innate immune response and subsequent increased likelihood for systemic infection and death.

Innate immunity SNPs are associated with risk for severe sepsis after burn injury

OBJECTIVE

To analyze allelic association with clinical outcome in a cohort of burn patients.

PATIENTS

Two hundred twenty-eight individuals with burns > or =15% total body surface area without significant non-burn related trauma who survived >48 hours post-admission were enrolled. One hundred fifty-nine of these patients were analyzed previously.

METHODS

Candidate polymorphisms within interleukin-1 beta (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), cellular differentiation marker 14 (CD14) and toll-like receptor 4 (TLR4) were evaluated by logistic regression analysis for association with increased risk for severe sepsis (sepsis plus organ dysfunction or shock).

RESULTS

After adjustment for age, burn size, ethnicity, gender and inhalation injury, alleles at TNF-alpha (308G, p=0.013), TLR4 (+896G, p=0.027), IL-6 (174C, p=0.040) and CD14 (159C, p=0.047) were significantly associated with an increased risk for severe sepsis.

CONCLUSIONS

Carriage of variant alleles at immune response genes were associated with increased risk for severe sepsis after burn injury.

Role of TLR4 receptor polymorphisms in Boutonneuse fever

The genetics of the interaction between host and microbes plays an essential role in the survival of the individual and attainment of longevity. The activation of toll-like receptor (TLR)4 plays a key role in natural and clonotypic immune responses. We evaluated whether TLR4 genotype is a component of genetic background protective versus rickettsiosis and whether this background influences longevity. We genotyped for +896A/G TLR4 polymorphism 78 patients affected with Boutonneuse fever, 78 age-matched controls and 78 advanced age individuals from Sicily. The +869G allele, that attenuates receptor signalling, was significantly overrepresented in patients in comparison with age-matched controls. By analyzing data according to gender, this allele was significantly higher in female patients when compared to advanced age women. Pro-inflammatory responses are programmed to resist fatal infections. So, it is not surprising that the genetic background of people that survive to an advanced age may be protective against infections. However, this seems to occur in women but not in men. In a previous study, the +896G TLR4 allele was overrepresented in advanced age men and underrepresented in men affected by myocardial infarction. Thus, previous and present results tend to agree with the suggestion that men and women may follow different trajectories to reach longevity. For men it might be more important to control atherogenesis, whereas for women it might be more important to control infectious diseases.

Organic dust induced inflammation--role of atopy and TLR-4 and CD14 gene polymorphisms

BACKGROUND

Polymorphisms in the genes controlling for CD14 and TLR-4 may influence the outcome of endotoxin-induced effects.

MATERIALS AND METHODS

A study was performed on 146 workers in industries with exposure to organic dust containing endotoxin and 53 controls. Endotoxin exposure was measured at representative work sites. Inflammagenic markers, cytokines, and CD14 and TLR-4 polymorphisms were determined in blood.

RESULTS

Among workers, serum levels of esinophilic cationic protein (ECP) were lower compared to controls and the proportion of atopics was lower. Atopic persons had lower levels of IL-6 and IL-8, both among controls and exposed. IL-6 and ECP values were lower among those with TLR-4 /+896 AG and GG polymorphisms as compared to AA. Among atopic workers with CD-14(-550) polymorphism CC, IL-8 was lower.

COMMENTS

The results suggest that CD14 and TLR-4 polymorphisms influence regulators of the inflammation induced by endotoxin in organic dusts. Atopic persons have a lower secretion of certain inflammatory cytokines.

Respiratory allergy in agricultural workers: recent developments

PURPOSE OF REVIEW

To review recent evidence on the relationship between occupational exposure to allergens and asthmagens, and risk for developing allergy and asthma and the role of modifying factors in farmers and farm workers.

RECENT FINDINGS

Recent studies identified agents that have not been associated with allergy or asthma in farming populations before. The most intriguing findings, however, are those that suggest that the development of atopy and asthma might be influenced by exposure to pathogen associated molecular patterns (PAMPs), including endotoxin.

SUMMARY

The adverse and potentially protective effects of microbial exposures in the farm environment are discussed. Recent findings indicate that it is very likely that the protective effect of exposure to PAMPs such as endotoxin is not limited to childhood age. The protective effects that probably developed during childhood can still be observed at adult age. Furthermore, it even seems likely that exposures at adult age (in occupational environments), which stimulate the innate immune system, have an effect on allergy, independently of childhood exposure. It is hypothesized that reversal of atopy might occur as a result of high exposure to endotoxins and other PAMPs.

A new method to measure air-borne pyrogens based on human whole blood cytokine response

Air-borne microorganisms, as well as their fragments and components, are increasingly recognized to be associated with pulmonary diseases, e.g. organic dust toxic syndrome, humidifier lung, building-related illness, "Monday sickness." We have previously described and validated a new method for the detection of pyrogenic (fever-inducing) microbial contaminations in injectable drugs, based on the inflammatory reaction of human blood to pyrogens. We have now adapted this test to evaluate the total inflammatory capacity of air samples. Air was drawn onto PTFE membrane filters, which were incubated with human whole blood from healthy volunteers inside the collection device. Cytokine release was measured by ELISA. The test detects endotoxins and non-endotoxins, such as fungal spores, Gram-positive bacteria and their lipoteichoic acid moiety and pyrogenic dust particles with high sensitivity, thus reflecting the total inflammatory capacity of a sample. When air from different surroundings such as working environments and animal housing was assayed, the method yielded reproducible data which correlated with other parameters of microbial burden tested. We further developed a standard material for quantification and showed that this assay can be performed with cryopreserved as well as fresh blood. The method offers a test to measure the integral inflammatory capacity of air-borne microbial contaminations relevant to humans. It could thus be employed to assess air quality in different living and work environments.

TLR4 and TNF-alpha polymorphisms are associated with an increased risk for severe sepsis following burn injury

CONTEXT

Sepsis, organ failure, and shock remain common among patients with moderate to severe burn injuries. The inability of clinical factors to identify at-risk patients suggests that genetic variation may influence the risk for serious infection and the outcome from severe injury.

OBJECTIVE

Resolution of genetic variants associated with severe sepsis following burn injury.

PATIENTS

A total of 159 patients with burns > or =20% of their total body surface area or any smoke inhalation injury without significant non-burn related trauma (injury severity score (ISS)> or =16), traumatic or anoxic brain injury, or spinal cord injury and who survived more than 48 h post-admission.

METHODS

Candidate single nucleotide polymorphisms (SNPs) within bacterial recognition (TLR4 +896, CD14 -159) and inflammatory response (TNF-alpha -308, IL-1beta -31, IL-6 -174) loci were evaluated for association with increased risk for severe sepsis (sepsis plus organ dysfunction or septic shock) and mortality.

RESULTS

After adjustment for age, full-thickness burn size, ethnicity, and gender, carriage of the TLR4 +896 G-allele imparted at least a 1.8-fold increased risk of developing severe sepsis following a burn injury, relative to AA homozygotes (adjusted odds ratio (aOR) 6.4; 95% confidence interval (CI) 1.8 to 23.2). Carriage of the TNF-alpha -308 A-allele imparted a similarly increased risk, relative to GG homozygotes (aOR = 4.5; 95% CI 1.7 to 12.0). None of the SNPs examined were significantly associated with mortality.

CONCLUSIONS

The TLR4 +896 and TNF-alpha -308 polymorphisms were significantly associated with an increased risk for severe sepsis following burn trauma.

Asthmatic disease among urban preschoolers: an observational study

Asthma is of increasing concern especially in industrialized countries. This cross-sectional study was to assess the influence of spatial and temporal variations in the urban air pollution profile on asthmatic disease. The prevalences presented are based on physician-diagnosed asthmatic and allergic disease data, collected between 1993 and 1995. Seven hundred and thirty-six preschool children (age 2 to 7, mean 5.7 years) of 37 daycare centres in the City of Leipzig participated in the study. Variations were observed in the lifetime prevalences of asthma and allergy with differences in a residential area's ambient pollution profile. Depending on the level of traffic (high or low), children residing in areas with a dominant coal-heating emission profile had more frequently a diagnosis of asthma, 17.5% and 8.8% (95% confidence intervals [CI]: 10.8...23.5 and 5.8...11.6, respectively), as compared to those, living in centrally heated areas 13.4% and 5.8% (CI: 6.6...19.3 and 1.2...9.6, respectively). Allergic disorders occurred more often in areas with a predominantly traffic-associated pollution profile, 14.3% and 9.6% vs. 5.8% and 3.7% (CI: 7.4...20.3 and 6.4...12.5; 1.2...9.6 and 0.2...6.5, respectively). Interestingly, asthmatic disease was not necessarily associated with a clinical history of allergies. Of the children with physician-diagnosed asthma, 83.7% were not reported to have a concurrent diagnosis of allergies nor to show clinical symptoms. This suggests that environmental exposures (i.e., complex pollution mixtures associated with residential coal-heating and/or traffic) may have differentially influenced the phenotypic expression of asthma. A qualitative discussion is presented on the occurrence of "asthma without reported allergies" in Leipzig.

Primary immunodeficiency to pneumococcal infection due to a defect in Toll-like receptor signaling

OBJECTIVE

The role of human Toll-like receptors (TLRs) in initiating protective immune responses in vivo is not well understood. We investigated the role of TLR signaling in defense against infection in a 3-year-old boy with a severe defect resulting in recurrent Streptococcus pneumoniae bacteremia.

METHODS

After classic immunodeficiencies were ruled out, the patient's mononuclear cells, macrophages, and dendritic cells (DCs) were studied. TLR signaling responses to a range of TLR- and interleukin-1 receptor (IL-1R)-specific agonists were investigated pre- and posttranscriptionally by measuring NF-kappaB translocation and cytokine mRNA and protein expression.

RESULTS

The patient's monocytic cells were profoundly deficient in cytokine production in response to a range of microbial-derived TLR agonists and to recombinant IL-1beta or IL-18. Lipopolysaccharide (LPS)-induced translocation of NF-kappaB p50 and p65 and the kinetics of LPS-induced cytokine mRNA transcription were normal except for IL-6 and IL-12p40, which were poorly transcribed. Despite deficient responses to TLR agonists by the patient's DCs and B cells, CD40L responses were normal.

CONCLUSIONS

We describe a patient with deficient TLR-mediated cytokine production with intact interleukin receptor-associated kinase (IRAK)-4 expression, NF-kappaB translocation, and enhanced susceptibility to infection. This patient demonstrates that TLR signaling, in the presence of intact antibody responses, may be a nonredundant requirement for defense against pyogenic infections.

Increased Toll-like receptor 4 expression in infants with respiratory syncytial virus bronchiolitis

The fusion protein of the respiratory syncytial virus (RSV) binds to the pattern recognition receptors, TLR4 and CD14, and initiates innate immunity response to the virus. The aim of the study was to investigate the expression of TLR4 on peripheral blood lymphocytes and monocytes in peripheral blood of infants in both acute and convalescent phase of RSV bronchiolitis (n = 26). In addition, TNF-alpha expression in lipopolysaccharide-stimulated monocytes was also assessed. The results showed TLR4 to be expressed predominantly by monocytes in both sick infants and controls. During the acute phase of infection monocytes up-regulated TLR4 in eight infants, which returned to the levels recorded in controls 4-6 weeks from infection. There was no difference in the percentage of TNF-alpha secreting monocytes. Of the clinical parameters tested, minimal oxygen saturation was found to correlate negatively with this expression in the group of infants with increased TLR4. Additional studies are under way to correlate this finding with the outcome of the immune response to RSV.

Asp299Gly and Thr399Ile genotypes of the TLR4 gene are associated with a reduced prevalence of diabetic neuropathy in patients with type 2 diabetes

OBJECTIVE

To establish whether single nucleotide polymorphisms (Asp299Gly and Thr399Ile) of the toll-like receptor 4 have an association with late diabetic complications.

RESEARCH DESIGN AND METHODS

The study was conducted in 246 type 1 and 530 type 2 diabetic patients. The alleles of both polymorphisms were detected using PCR and subsequent cleavage by NcoI and HinfI restriction endonucleases.

RESULTS

No difference was found between type 1 and type 2 diabetic patients in the prevalence of alleles of the Asp299Gly and Thr399Ile polymorphisms. In most cases, the alleles Gly299 and Ile399 occurred in a co-segregatory manner. The prevalence of the Gly299/Ile399 haplotype was 10.6 and 12.1% in type 1 and type 2 diabetic patients, respectively (P = 0.63). No association with diabetic nephropathy or diabetic neuropathy was found in type 1 diabetic patients. In type 2 diabetic patients, however, heterozygote carriers of the Asp299Gly and Thr399Ile genotypes had a significantly reduced prevalence of diabetic neuropathy (odds ratio 0.35 [95% CI 0.19-0.61]; P = 0.0002); no association with diabetic nephropathy was found.

CONCLUSIONS

Our data indicate that Asp299Gly and Thr399Ile genotypes of the TLR4 gene are associated with reduced prevalence of diabetic neuropathy in type 2, but not in type 1, diabetes. Thus different mechanisms may be involved in the pathophysiology of diabetic neuropathy in type 1 and type 2 diabetes.