Polymorphisms in CD14, mannose-binding lectin, and Toll-like receptor-2 are associated with increased prevalence of infection in critically ill adults*

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.

Role of Toll-Like Receptors 2 and 4 Genes Polymorphisms in Neonatal Sepsis in a Developing Country: A Pilot Study

Objective Toll-like receptors (TLR) are one of the key molecules that alert the immune system to the presence of microbial infections. This study attempts to elucidate the role of TLR2 and TLR4 polymorphisms in neonatal sepsis.

Methods A case–control study including 30 neonates with confirmed sepsis compared with 20 neonates in a control group. TLR2 and TLR24 gene polymorphisms were confirmed by polymerase chain reaction.

Results The majority of infections were attributed to gram-negative organisms (72.5%) namely Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli. Results also revealed that incidence of TLR polymorphism was significantly different between the sepsis and control groups (p = 0.016). The most common polymorphism was TLR2; Arg 753 Gln (16.7%). Presence of TLR polymorphism was also associated with a longer duration of therapy (a median of 10 days for cases with positive polymorphism compared with 6.5 days for negative cases; p = 0.001).

Conclusion This pilot study suggests that any polymorphisms in TLR2 and TLR4 might have a role that interferes with the innate immune response of newborn.

Cannabis Sativa Revisited-Crosstalk between microRNA Expression, Inflammation, Oxidative Stress, and Endocannabinoid Response System in Critically Ill Patients with Sepsis

Critically ill patients with sepsis require a multidisciplinary approach, as this situation implies multiorgan distress, with most of the bodily biochemical and cellular systems being affected by the condition. Moreover, sepsis is characterized by a multitude of biochemical interactions and by dynamic changes of the immune system. At the moment, there is a gap in our understanding of the cellular, genetic, and molecular mechanisms involved in sepsis. One of the systems intensely studied in recent years is the endocannabinoid signaling pathway, as light was shed over a series of important interactions of cannabinoid receptors with biochemical pathways, specifically for sepsis. Furthermore, a series of important implications on inflammation and the immune system that are induced by the activity of cannabinoid receptors stimulated by the delta-9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD) have been noticed. One of the most important is their ability to reduce the biosynthesis of pro-inflammatory mediators and the modulation of immune mechanisms. Different studies have reported that cannabinoids can reduce oxidative stress at mitochondrial and cellular levels. The aim of this review paper was to present, in detail, the important mechanisms modulated by the endocannabinoid signaling pathway, as well as of the molecular and cellular links it has with sepsis. At the same time, we wish to present the possible implications of cannabinoids in the most important biological pathways involved in sepsis, such as inflammation, redox activity, immune system, and epigenetic expression.

Association of TLR4 and TLR9 gene polymorphisms and haplotypes with cervicitis susceptibility

BACKGROUND

Cervicitis is one of the major health problems amongst women caused by infection of various pathogens including Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), Trichomonas vaginalis (TV) as well as human papillomavirus (HPV), and persistent cervical inflammation is one of the etiologic agents of cervical cancer. Toll-like receptors (TLRs) play an important role in the recognition and subsequent elimination of these pathogens. Variations in the Toll-like receptor genes influence susceptibility to pathogens as well as disease progression independently.

METHODS

Ten single nucleotide polymorphisms, five each of TLR4 and TLR9 genes were analyzed among 130 cervicitis patients and 150 controls either using polymerase chain reaction-restriction fragment length polymorphism or allele specific-PCR.

RESULTS

T. vaginalis infection was found at the highest frequency (30.7%) as compared to C. trachomatis (1.5%), N. gonorrhoeae (2.3%) and HPV (4.6%) infections in cervicitis patients. TLR4 rs11536889 CC (age-adjusted OR, 2.469 [95% CI, 1.499 to 4.065]; p < 0.001) and TLR9 rs187084 TC (age-adjusted OR, 2.165 [95% CI, 1.267-3.699]; p = 0.005) genotypes showed the higher distribution in cervicitis patients compared to controls. In addition, TLR4 rs11536889 C allele was shown to increase the risk of cervicitis (age-adjusted OR, 1.632 [95% CI, 1.132 to 2.352]; p = 0.009) compared to controls. The TLR4 haplotype GCA (OR, 0.6 [95% CI, 0.38-0.95]; p = 0.0272) and TLR9 haplotype GTA (OR, 1.99 [95% CI, 1.14-3.48]; p = 0.014) were found to be associated with decreased and increased risk of cervicitis respectively.

CONCLUSIONS

TLR4 and TLR9 polymorphisms, as well as haplotypes were shown to modulate the cervicitis risk.

Sepsis Diagnostics in the Era of "Omics" Technologies

Sepsis is a multifactorial clinical syndrome with an extremely dynamic clinical course and with high diverse clinical phenotype. Early diagnosis is crucial for the final clinical outcome. Previous studies have not identified a biomarker for the diagnosis of sepsis which would have sufficient sensitivity and specificity. Identification of the infectious agents or the use of molecular biology, next gene sequencing, has not brought significant benefit for the patient in terms of early diagnosis. Therefore, we are currently searching for biomarkers, through "omics" technologies with sufficient diagnostic specificity and sensitivity, able to predict the clinical course of the disease and the patient response to therapy. Current progress in the use of systems biology technologies brings us hope that by using big data from clinical trials such biomarkers will be found.

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.

Melanocortin-1 Receptor Polymorphisms and the Risk of Complicated Sepsis After Trauma: A Candidate Gene Association Study

OBJECTIVE

The aim of the study was to determine if melanocortin-1 receptor (MC1R) single nucleotide polymorphisms (SNPs) are associated with complicated sepsis after trauma.

BACKGROUND

Nosocomial infections are an important cause of morbidity and mortality after trauma. Several SNPs in inflammation-related genes have been associated with sepsis. MC1R is an anti-inflammatory mediator that may be involved in the immune response after trauma.

PATIENTS AND METHODS

We genotyped eight common MC1R SNPs in genomic DNA from subjects enrolled in a previously reported prospective cohort study. Subjects were adult trauma patients admitted to the intensive care unit at a Level 1 trauma center (2003-2005).

RESULTS

A total of 1,246 subjects were included in the analysis. The majority were male (70%), severely injured (81%), and injured by a blunt mechanism (89%). Forty percent developed sepsis, and 23% developed complicated sepsis, which was defined as sepsis with organ dysfunction. In logistic regression analysis, with adjustments for age, sex, body mass index, injury severity score, red blood cell transfusion requirement, and mechanism of injury, the MC1RR163Q variant (rs885479) was associated with a lower risk of developing complicated sepsis (adjusted odds ratio [ORadj] = 0.48, 95% confidence interval [CI]: 0.28-0.81, P = 0.006). In a subgroup of 511 subjects with genome-wide SNP data, the association between the MC1RR163Q variant and complicated sepsis remained significant after adjusting for genetic substructure (by principal components) and the above clinical factors (ORadj = 0.30, 95% CI: 0.13-0.70, P = 0.005).

CONCLUSIONS

MC1RR163Q is associated with a lower risk of complicated sepsis after trauma. Therapeutic targeting of MC1R may be beneficial for trauma patients at risk for complicated sepsis.

Genome-wide association study of sepsis in extremely premature infants

OBJECTIVE

To identify genetic variants associated with sepsis (early-onset and late-onset) using a genome-wide association (GWA) analysis in a cohort of extremely premature infants.

STUDY DESIGN

Previously generated GWA data from the Neonatal Research Network's anonymised genomic database biorepository of extremely premature infants were used for this study. Sepsis was defined as culture-positive early-onset or late-onset sepsis or culture-proven meningitis. Genomic and whole-genome-amplified DNA was genotyped for 1.2 million single-nucleotide polymorphisms (SNPs); 91% of SNPs were successfully genotyped. We imputed 7.2 million additional SNPs. p Values and false discovery rates (FDRs) were calculated from multivariate logistic regression analysis adjusting for gender, gestational age and ancestry. Target statistical value was p<10-5. Secondary analyses assessed associations of SNPs with pathogen type. Pathway analyses were also run on primary and secondary end points.

RESULTS

Data from 757 extremely premature infants were included: 351 infants with sepsis and 406 infants without sepsis. No SNPs reached genome-wide significance levels (5×10-8); two SNPs in proximity to FOXC2 and FOXL1 genes achieved target levels of significance. In secondary analyses, SNPs for ELMO1, IRAK2 (Gram-positive sepsis), RALA, IMMP2L (Gram-negative sepsis) and PIEZO2 (fungal sepsis) met target significance levels. Pathways associated with sepsis and Gram-negative sepsis included gap junctions, fibroblast growth factor receptors, regulators of cell division and interleukin-1-associated receptor kinase 2 (p values<0.001 and FDR<20%).

CONCLUSIONS

No SNPs met genome-wide significance in this cohort of extremely low birthweight infants; however, areas of potential association and pathways meriting further study were identified.

The Burden of Genetic and Epigenetic Traits in Prematurity

Despite decades of investigations and accumulated scientific knowledge, preterm birth (PTB) remains a significant burden worldwide. Several mechanisms have been proposed to explain this condition, and a number of risk factors from infectious to behavioral and genetic/epigenetic factors influence this outcome. The heritability of PTB is estimated to be 17% to 36%, which demonstrates that genetic predisposition plays a key role in PTB. Structural DNA modifications without changes in the DNA sequence and post-transcriptional regulation also have an impact on gene expression and thus influence pregnancy outcomes. There is a complex interplay between environmental factors and the individual's genetics and epigenetics that may culminate in PTB, but the complete regulatory pathways and networks involved in this context are still unclear. Here, we outline what is known so far about the genetic and epigenetic factors involved in preterm delivery, including polymorphisms, DNA methylation, and microRNAs, and suggest fields for research.

Genetic risk factors for serious infections in inflammatory bowel diseases

INTRODUCTION

Immunosuppression, the cornerstone of management of Crohn's disease (CD) and ulcerative colitis (UC) (inflammatory bowel diseases; IBD) is associated with an increased risk of serious infections that is inadequately predicted by clinical risk factors. The role of genetics in determining susceptibility to infections is unknown.

METHODS

From a prospective-consented patient registry, we identified IBD patients with serious infections requiring hospitalization. Analysis was performed to identify IBD-related and non-IBD related immune response loci on the Immunochip that were associated with serious infections and a genetic risk score (GRS) representing the cumulative burden of the identified single nucleotide polymorphisms was calculated. Multivariable logistic regression used to identify effect of clinical and genetic factors.

RESULTS

The study included 1333 IBD patients (795 CD, 538 UC) with median disease duration of 13 years. A total of 133 patients (10%) had a serious infection requiring hospitalization. Patients with infections were more likely to have CD and had shorter disease duration. The most common infections were skin and soft-tissue, respiratory and urinary tract infections. Eight IBD risk loci and two other polymorphisms were significantly associations with serious infections. Each one point increase in the infection GRS was associated with a 50% increase in risk of infections (OR = 1.53, 95% CI = 1.37-1.70) (p = 1 × 10^-14), confirmed on multivariable analysis. Genetic risk factors improved performance of a model predicting infections over clinical covariates alone (p < 0.001).

CONCLUSIONS

Genetic risk factors may predict susceptibility to infections in patients with IBD.

Marcadores moleculares en el diagnóstico y pronóstico de sepsis, sepsis grave y choque séptico

Introducción. A pesar de los importantes avances en el entendimiento de la patofisiología de la sepsis, la mortalidad que genera sigue siendo alta.Objetivo. Describir el estado del arte de los biomarcadores moleculares propuestos hasta el momento como potenciales marcadores para el diagnóstico y pronóstico de sepsis, sepsis grave y choque séptico.Materiales y métodos. Se analizaron los registros de los últimos 14 años que se encontraban en PubMed, en The New England Journal of Medicine (NEJM) y en Illinois Automatic Computer (ILLIAC) con los términos sepsis, genetic polymorphisms, genetic variation y molecular marker. Se clasificaron los artículos por año de publicación y solo se tuvieron en cuenta los publicados durante los últimos 10 años.Resultados. La búsqueda arrojó 3 370 referencias que cubren más de 30 genes con polimorfismos genéticos que pueden ser empleados como potenciales marcadores de polimorfismos. Estos fueron evaluados para su uso en las diferentes manifestaciones de sepsis, su diagnóstico y progresión. Se describen 20 genes marcadores: cuatro asociados con bacteremia (TLR-1, TLR-2, Proteína C y Selectina-E), nueve con sepsis (IL-1B, IL-1A, IL-6, TNF-α, TLR-1, MBL-1, Hsp70, PAI-1 y MIF-1), siete con sepsis grave (IL-1RN, IL-10, TNF-α, CD14, TREM-1, Caspasa 12 y DEFB-1), cinco con choque séptico (TNF-B, TLR-4, Hsp70, MBL-1 y CD14 ) y tres con disfunción multiorgánica (TLR-1, PAI-1 y Proteína C).Conclusión. Los polimorfismos genéticos, en su mayoría, han sido probados clínicamente como marcadores de diagnóstico y pronóstico en la sepsis con resultados prometedores por la alta especificidad y sensibilidad en la práctica clínica.

Early Prediction of Sepsis Incidence in Critically Ill Patients Using Specific Genetic Polymorphisms

Several diagnostic methods for the evaluation and monitoring were used to find out the pro-inflammatory status, as well as incidence of sepsis in critically ill patients. One such recent method is based on investigating the genetic polymorphisms and determining the molecular and genetic links between them, as well as other sepsis-associated pathophysiologies. Identification of genetic polymorphisms in critical patients with sepsis can become a revolutionary method for evaluating and monitoring these patients. Similarly, the complications, as well as the high costs associated with the management of patients with sepsis, can be significantly reduced by early initiation of intensive care.

Ancestry informative markers and selected single nucleotide polymorphisms in immunoregulatory genes on preterm labor and preterm premature rupture of membranes: a case control study

Background

A genetic predisposition to Preterm Labor (PTL) and Preterm Premature Rupture of Membranes (PPROM) has been suggested; however the relevance of polymorphisms and ancestry to susceptibility to PTL and PPROM in different populations remains unclear. The aim of this study was to evaluate the contribution of maternal and fetal SNPs in the IL1B, IL6, IL6R, TNFA, TNFR, IL10, TLR2, TLR4, MMP9, TIMP1 and TIMP2 genes and the influence of ancestry background in the susceptibility to PTL or PPROM in Brazilian women.

Methods

Case–control study conducted at a tertiary hospital in São Paulo State, Brazil. We included women with PTL or PPROM and their babies (PTL: 136 women and 88 babies; PPROM: 65 women and 44 babies). Control group included 402 mother-babies pairs of term deliveries. Oral swabs were collected for identification of AIMs by fragment analysis and SNPs by Taqman® SNP Genotyping Assays and PCR. Linkage Disequilibrium and Hardy-Weinberg proportions were evaluated using Genepop 3.4. Haplotypes were inferred using the PHASE algorithm. Allele, genotype and haplotype frequencies were compared by Fisher’s exact test or χ² and Odds Ratio. Logistic regression was performed. Clinical and sociodemographic data were analyzed by Fisher’s exact test and Mann–Whitney.

Results

PTL was associated with European ancestry and smoking while African ancestry was protective. The fetal alleles IL10-592C (rs800872) and IL10-819C (rs1800871) were also associated with PTL and the maternal haplotype TNFA-308G-238A was protective. Maternal presence of IL10-1082G (rs1800896) and TLR2A (rs4696480) alleles increased the risk for PPROM while TNFA-238A (rs361525) was protective. Family history of PTL/PPROM was higher in cases, and time to delivery was influenced by IL1B-31T (rs1143627) and TLR4-299G (rs4986790).

Conclusion

There is an association between European ancestry and smoking and PTL in our Brazilian population sample. The presence of maternal or fetal alleles that modify the inflammatory response increase the susceptibility to PTL and PPROM. The family history of PTL/PPROM reinforces a role for genetic polymorphisms in susceptibility to these outcomes.

TLR2, TLR4 and TLR9 genotypes and haplotypes in the susceptibility to and clinical course of Chlamydia trachomatis infections in Dutch women

Chlamydia trachomatis infections demonstrate remarkable differences in clinical course that are approximately 40% based on host genetic variation. Here, we study the single nucleotide polymorphisms (SNPs) and their haplotypes in TLR2, TLR4 and TLR9 (TLR2 +2477G>A; TLR2 -16934T>A; TLR4+896A>G; TLR9 -1237T>C and TLR9 +2848G>A) in relation to the susceptibility to, and severity of C. trachomatis infections. We analysed the five SNPs in a cohort of 770 Dutch Caucasian women either attending a sexually transmitted diseases outpatient clinic (n = 731) or having complaints of subfertility (n = 39). Haplotype analyses showed a trend for TLR2 haplotype I (-16934T/+2477G) to protect against the development of symptoms and tubal pathology (Ptrend = 0.03) after Chlamydia infection. In the susceptibility cohort, TLR9 haplotype III (-1237C/+2848A) showed a significant decreasing trend in the development of symptoms after C. trachomatis infection (P = 0.02, OR: 0.55, 95%CI: 0.33-0.91). Logistic regression of the TLR2 haplotypes, TLR4+896A>G, and TLR9 haplotypes showed that the TLR2 haplotype combinations AG-TA and AG-TG confer risk (OR 3.4 (P = 0.01) and 1.6 (P = 0.03)), while the TLR9 haplotype combination TG-TA protects against C. trachomatis infections (OR: 0.4, P = 0.004). Our study shows that both TLR2 and TLR9 genes and SNP combinations do influence the clinical course of Chlamydia infections.

TNFAIP2 Inhibits Early TNFα-Induced NF-x03BA;B Signaling and Decreases Survival in Septic Shock Patients

During septic shock, tumor necrosis factor alpha (TNFα) is an early response gene and induces a plethora of genes and signaling pathways. To identify robust signals in genes reliably upregulated by TNFα, we first measured microarray gene expression in vitro and searched methodologically comparable, publicly available data sets to identify concordant signals. Using tag single-nucleotide polymorphisms in the genes common to all data sets, we identified a genetic variant of the TNFAIP2 gene, rs8126, associated with decreased 28-day survival and increased organ dysfunction in an adult cohort in the Vasopressin and Septic Shock Trial. Similar to this cohort, we found that an association with rs8126 and increased organ dysfunction is replicated in a second cohort of septic shock patients in the St. Paul's Hospital Intensive Care Unit. We found that TNFAIP2 inhibits NF-x03BA;B activity, impacting the downstream cytokine interleukin (IL)-8. The minor G allele of TNFAIP2 rs8126 resulted in greater TNFAIP2 expression, decreased IL-8 production and was associated with decreased survival in patients experiencing septic shock. These data suggest that TNFAIP2 is a novel inhibitor of NF-x03BA;B that acts as an autoinhibitor of the TNFα response during septic shock.

Genome-wide association study of survival from sepsis due to pneumonia: an observational cohort study

BACKGROUND

Sepsis continues to be a major cause of death, disability, and health-care expenditure worldwide. Despite evidence suggesting that host genetics can influence sepsis outcomes, no specific loci have yet been convincingly replicated. The aim of this study was to identify genetic variants that influence sepsis survival.

METHODS

We did a genome-wide association study in three independent cohorts of white adult patients admitted to intensive care units with sepsis, severe sepsis, or septic shock (as defined by the International Consensus Criteria) due to pneumonia or intra-abdominal infection (cohorts 1-3, n=2534 patients). The primary outcome was 28 day survival. Results for the cohort of patients with sepsis due to pneumonia were combined in a meta-analysis of 1553 patients from all three cohorts, of whom 359 died within 28 days of admission to the intensive-care unit. The most significantly associated single nucleotide polymorphisms (SNPs) were genotyped in a further 538 white patients with sepsis due to pneumonia (cohort 4), of whom 106 died.

FINDINGS

In the genome-wide meta-analysis of three independent pneumonia cohorts (cohorts 1-3), common variants in the FER gene were strongly associated with survival (p=9·7 × 10(-8)). Further genotyping of the top associated SNP (rs4957796) in the additional cohort (cohort 4) resulted in a combined p value of 5·6 × 10(-8) (odds ratio 0·56, 95% CI 0·45-0·69). In a time-to-event analysis, each allele reduced the mortality over 28 days by 44% (hazard ratio for death 0·56, 95% CI 0·45-0·69; likelihood ratio test p=3·4 × 10(-9), after adjustment for age and stratification by cohort). Mortality was 9·5% in patients carrying the CC genotype, 15·2% in those carrying the TC genotype, and 25·3% in those carrying the TT genotype. No significant genetic associations were identified when patients with sepsis due to pneumonia and intra-abdominal infection were combined.

INTERPRETATION

We have identified common variants in the FER gene that associate with a reduced risk of death from sepsis due to pneumonia. The FER gene and associated molecular pathways are potential novel targets for therapy or prevention and candidates for the development of biomarkers for risk stratification.

FUNDING

European Commission and the Wellcome Trust.

Polymorphisms of Toll-like receptors (TLR2 and TLR4) are associated with the risk of infectious complications in acute myeloid leukemia

Infectious complications continue to be one of the major causes of morbidity and mortality in patients with acute myeloid leukemia (AML). Several single-nucleotide polymorphisms (SNPs) of Toll-like receptors (TLRs) can affect the genetic susceptibility to infections or even sepsis. We sought to investigate the impact of different SNPs on the incidence of developing sepsis and pneumonia in patients with newly diagnosed AML following induction chemotherapy. We analyzed three SNPs in the TLR2 (Arg753Gln) and TLR4 (Asp299Gly and Thr399Ile) gene in a cohort of 155 patients with AML who received induction chemotherapy. The risk of developing sepsis and pneumonia was assessed by multiple logistic regression analyses. The presence of the TLR2 Arg753Gln polymorphism was significantly associated with pneumonia in AML patients (odds ratio (OR): 10.78; 95% confidence interval (CI): 2.0-58.23; P=0.006). Furthermore, the cosegregating TLR4 polymorphisms Asp299Gly and Thr399Ile were independent risk factors for the development of both sepsis and pneumonia (OR: 3.55; 95% CI: 1.21-10.4, P=0.021 and OR: 3.57, 95% CI: 1.3-9.86, P=0.014, respectively). To our best knowledge, this study represents the first analysis demonstrating that polymorphisms of TLR2 and TLR4 influence the risk of infectious complications in patients with AML undergoing induction chemotherapy.

Association between toll-like receptor 2 gene diversity and early-onset bipolar disorder

BACKGROUND

Toll-like receptor 2 (TLR2) molecules play a pivotal role in innate immune responses by their ability to recognize and sense a wide repertoire of infectious and endogenous cellular structural elements. Here we evaluated whether genetic variants in TLR2 influence the age of the disease onset in bipolar disorder (BD).

METHODS

DNAs from 571 BD patients 229 early-onset (EO-BD) and 342 late-onset (LO-BD) and 199 healthy controls (HC) were analyzed for the following TLR2 polymorphisms: the 5'-UTR -196 to -174 insertion/deletion (ins/del), the intron 1 rs4696480 A/T, and the exon 3 rs3804099 C/T and rs3804100 C/T. PHASE software was used for haplotype reconstruction. Genetic associations were examined using a chi-square test.

RESULTS

We found that the TLR2 rs3804099 TT was significantly more prevalent in EO-BD than in LO-BD patients (corrected p (pc)=0.024). After excluding family history of psychiatric disorders, we also found that the TLR2 rs4696480 TT genotype was significantly more prevalent in EO-BD as compared to LO-BD and controls (pc=0.002 and 0.002). Homozygous state for the insTTT haplotype, carrying the above mentioned risk genotypes, was significantly more frequent in EO-BD than in LO-BD patients (pc=0.007) and in EO-BD without family history of psychiatric disorders as compared to (i) those with positive history (pc=0.03), (ii) with LO-BD without family history (pc=0.001) and (iii) with HC (pc=0.009).

LIMITATIONS

Confirmation by replication in independent BD cohorts is warranted.

CONCLUSIONS

Our data suggest the potential role of TLR2 genetic variants in the pathogen-mediated susceptibility to BD.

Mannose-binding lectin gene variants and infections in patients receiving autologous stem cell transplantation

Background

Serious infections are common in patients undergoing autologous stem cell transplantation (ASCT) mainly because of the effects of immunosuppression. The innate immune system plays an important role in the defense against different infections. Mannose binding lectin (MBL) is a central molecule of the innate immune system. There are several promoter polymorphisms and structural variants of the MBL2 gene that encodes for this protein. These variants produce low levels of MBL and have been associated with an increased risk for infections.

Methods

Prospective cohort study. The incidence, severity of infections and mortality in 72 consecutive patients with hematologic diseases who underwent ASCT between February 2006 and June 2008 in a tertiary referral center were analyzed according to their MBL2 genotype. INNO-LiPA MBL2 was used for MBL2 gene amplification and genotyping. Relative risks (RR) (IC95%) as measure of association were calculated. Multivariate analysis was performed using logistic regression.

Results

A statistically significant higher number of fungal infections was found in patients with MBL2 variants causing low MBL levels (21.1%versus1.9%, p=0.016). In this MBL2 variant group infection was more frequently the cause of mortality than in the MBL2 wild-type group (p=0.05). Although not statistically significant, there was a higher incidence of major infections in the MBL2 variant group as well as a higher number of infections caused by gram-positive bacteria.

Conclusions

Low-producer MBL2 genotypes were associated with an increased number of fungal infections in ASCT patients, which would suggest that MBL has a protective role against such infections. ASCT patients with MBL2 variant genotypes are more likely to die as a result of an infection.

The meta-genome of sepsis: host genetics, pathogens and the acute immune response

Severe infection and the patient response constitute sepsis. Here, we review the meta-genome (patient genetics, pathogen communities and host response) and its impact upon the outcome of severe sepsis. Patient genetics, both predisposition for infection and the subsequent response to infection are reviewed. The pathogen is discussed with particular emphasis upon the modern era of microbiome analysis and nucleic acid diagnostics. Finally, we discuss the host clinical and immune responses and present new data to suggest that the immune response is the key to understanding sepsis and improving a death rate of nearly 30%.

Mannose-binding lectin polymorphisms and the risk of sepsis: evidence from a meta-analysis

Several studies have evaluated the association between mannose-binding lectin (MBL) polymorphisms and sepsis. However, the results are inconclusive and conflicting. To better understand the roles of MBL polymorphisms in sepsis, we conducted a comprehensive meta-analysis. All relevant studies were searched from PubMed, EMBASE and Web of Knowledge databases, with the last report up to 7 May 2013. Twenty-nine studies addressing four MBL polymorphisms (-550G/C, -221G/C, structure variant A/O, Gly54Asp) were analysed for susceptibility to sepsis and one study for sepsis-related mortality. Overall, significant associations between structure variant A/O and susceptibility to sepsis were observed for AO + OO vs. AA [odds ratio (OR) 1·27, 95% confidence interval (CI) 1·05-1·52, P = 0·01] and O vs. A (OR 1·19, 95% CI 1·02-1·40, P = 0·03). In subgroup analysis based on age group, increased risk was found in the paediatric group in the dominant model (OR 1·72, 95% CI 1·16-2·56, P = 0·007). Moreover, there was a slight association between the +54A/B polymorphism and susceptibility to sepsis in Caucasians (recessive model: OR 10·64, 95% CI 1·24-91·65, P = 0·03). However, no association was observed for -550G/C and -221G/C polymorphisms both overall and in subgroup analysis. For sepsis-related mortality, only one study suggested AO/OO was associated with in-hospital mortality in pneumococcal sepsis patients after controlling for confounding variables. Our meta-analysis indicated that MBL structure variants might be associated with susceptibility to sepsis but further studies with a large sample size should be conducted to confirm these findings.

Immunoinflammatory response in critically ill patients: severe sepsis and/or trauma

Immunoinflammatory response in critically ill patients is very complex. This review explores some of the new elements of immunoinflammatory response in severe sepsis, tumor necrosis factor-alpha in severe acute pancreatitis as a clinical example of immune response in sepsis, immune response in severe trauma with or without secondary sepsis, and genetic aspects of host immuno-inflammatory response to various insults in critically ill patients.

Community acquired pneumonia: genetic variants influencing systemic inflammation

The inflammatory response depends on several factors, including pathogenicity and duration of the stimulus, and also on the balance between inflammatory and antiinflammatory response. Several studies have presented evidence of the importance of genetic factors in severe infections. The innate immune response prevents the invasion and spread of pathogens during the first hours after infection. Each of the different processes involved in innate immunity may be affected by genetic polymorphisms, which can result in susceptibility or resistance to infection. The results obtained in the different studies do not irrefutably prove the role or function of a gene in the pathogenesis of respiratory infections. However, they can generate new hypotheses, suggest new candidate genes based on their role in the inflammatory response, and constitute a first step in understanding the underlying genetic factors.

The role of mannose-binding lectin in severe sepsis and septic shock

Severe sepsis and septic shock are a primary cause of death in patients in intensive care unit (ICU). Investigations upon genetic susceptibility profile to systemic complications during severe infections are a field of increasing scientific interest. Particularly when adaptive immune system is compromised or immature, innate immunity plays a key role in the immediate defense against invasive pathogens. Mannose-binding lectin (MBL) is a serum protein that recognizes a wide range of pathogenic microorganisms and activates complement cascade via the antibody-independent pathway. More than 30% of humans harbor mutations in MBL gene (MBL2) resulting in reduced plasmatic levels and activity. Increased risk of infection acquisition has been largely documented in MBL-deficient patients, but the real impact of this form of innate immunosuppression upon clinical outcome is not clear. In critically ill patients higher incidence and worse prognosis of severe sepsis/septic shock appear to be associated with low-producers haplotypes. However an excess of MBL activation might be also harmful due to the possibility of an unbalanced proinflammatory response and an additional host injury. Strategies of replacement therapies in critically ill patients with severe infections are under investigation but still far to be applied in clinical practice.

Significance of mannose-binding lectin deficiency and nucleotide-binding oligomerization domain 2 polymorphisms in Staphylococcus aureus bloodstream infections: a case-control study

BACKGROUND

Pathways coordinated by innate pattern recognition receptors like mannose-binding lectin (MBL) and nucleotide-binding oligomerization domain 2 (NOD2) are among the first immune responses to Staphylococcus aureus (S. aureus) bloodstream infections (BSI) in animal models, but human data are limited. Here, we investigated the role of MBL deficiency and NOD2 mutations in the predisposition to and severity of S. aureus BSI.

PATIENTS AND METHODS

A matched case-control study was undertaken involving 70 patients with S. aureus BSI and 70 age- and sex-matched hospitalized controls. MBL levels, MBL2 and NOD2 polymorphisms were analyzed.

RESULTS

After adjusting for potential confounders, MBL deficiency (<0.5 µg/ml) was found less frequently in cases than controls (26 vs. 41%, OR 0.4, 95% confidence interval (CI) 0.20-0.95, p=0.04) as were low producing MBL genotypes (11 vs. 23%, OR 0.2, 95% CI 0.08-0.75, p=0.01), whereas NOD2 polymorphisms were similarly distributed. Cases with NOD2 polymorphisms had less organ dysfunction as shown by a lower SOFA score (median 2.5 vs. 4.5, p=0.02), whereas only severe MBL deficiency (<0.1 µg/ml) was associated with life-threatening S. aureus BSI (OR 5.6, 95% CI 1.25-24.85, p=0.02).

CONCLUSIONS

Contrary to animal model data, our study suggests MBL deficiency may confer protection against acquiring S. aureus BSI. NOD2 mutations were less frequently associated with multi-organ dysfunction. Further human studies of the innate immune response in S. aureus BSI are needed to identify suitable host targets in sepsis treatment.

Association between CD14 promoter -159C/T polymorphism and the risk of sepsis and mortality: a systematic review and meta-analysis

Background

Recent studies on the association between CD14-159C/T polymorphism and sepsis showed inconclusive results. Accordingly, we conducted a comprehensive literature search and a meta-analysis to determine whether the CD14-159C/T polymorphism conferred susceptibility to sepsis or was associated with increased risk of death from sepsis.

Methodology

Data were collected from the following electronic databases: PubMed, Embase, Medline, Web of Knowledge, and HuGE Navigator, with the last report up to June 15, 2012. The odds ratio (OR) and 95% confidence interval (CI) were used to assess the strength of association. We summarized the data on the association between CD14-159C/T polymorphism and sepsis in the overall population and subgroup by ethnicity and sepsis subtype.

Principal Findings

A total of 16 studies on sepsis morbidity (1369 cases and 2382 controls) and 4 studies on sepsis mortality (731 sepsis patients) met the inclusion criteria for meta-analysis. Overall analysis showed no strong evidences of association with sepsis susceptibility under any genetic model. However, slight associations were found in Asian populations (dominant model: OR = 1.38, 95%CI = 0.96–1.98, P = 0.08) and septic shock patients (dominant model: OR = 1.72, 95%CI 1.05–2.83, P = 0.03; allelic model: OR = 1.52, 95%CI 1.09–2.12, P = 0.01) in the stratified analysis. Moreover, there was borderline association between CD14-159C/T and sepsis mortality under the dominant genetic model (OR = 1.44, 95%CI = 0.98–2.11, P = 0.06).

Conclusions/Significance

This meta-analysis suggests that the CD14-159C/T polymorphism may not be a significant susceptibility factor in the risk of sepsis and mortality. Only weak associations were observed in Asian populations and septic shock patients. More studies based on larger sample sizes and homogeneous sepsis patients are needed to confirm these findings.

Single-nucleotide polymorphisms in the Toll-like receptor pathway increase susceptibility to infections in severely injured trauma patients

BACKGROUND

Sepsis and subsequent multiple-organ failure are the predominant causes of late mortality in trauma patients. Susceptibility and response to infection is, in part, heritable. Single-nucleotide polymorphisms (SNPs) in Toll-like receptor (TLR) and cluster of differentiation 14 (CD14) genes of innate immunity may play a key role. The aim of this study was to assess if SNPs in TLR/CD14 predisposed trauma patients to infection.

METHODS

A prospective cohort of trauma patients (age 18-80 years; injury severity score [ISS] ≥ 16) admitted to a Level I trauma center between January 2008 and April 2011 was genotyped for SNPs in TLR2 (T-16934A and R753Q), TLR4 (D299G and T399I), TLR9 (T-1486C and T-1237C), and CD14 (C-159T) using high-resolution melting analysis. Association of genotype with prevalence of positive culture findings (gram positive, gram negative, fungi), systemic inflammatory response syndrome (SIRS), sepsis, septic shock, and mortality was tested with χ(2) and logistic regression analysis.

RESULTS

Genotyping was performed for 219 patients, of whom 51% developed positive culture findings in sputum, wounds, blood, or urine. SIRS developed in 64%, sepsis in 36%, and septic shock in 17%. The TLR2 T-16934A TA genotype increased the risk of a gram-positive infection (odds ratio, 2.816; 95% confidence interval, 1.249-6.348; p = 0.013) and SIRS (odds ratio, 2.386; 95% confidence interval, 1.011-5.632; p = 0.047). Trends were noted for TLR9 and CD14 SNPs but did not reach statistical significance. Sepsis and septic shock were unrelated to any of the SNPs studied.

CONCLUSION

Aberrant functioning of the TLR/CD14 pathway of innate immunity changes the risk of infectious complications in severely injured trauma patients. Of the seven SNPs studied, the TLR2 T-16934A increased the risk, the TLR9 T-1486C SNPs may decrease the risk, and TLR4 variation seemed unrelated to outcome. Early genotyping may prove to be helpful in the future in identifying polytraumatized patients at risk for infectious outcome.

LEVEL OF EVIDENCE

Prognostic and epidemiologic study, level II.

Propofol exerts anti-inflammatory effects in rats with lipopolysaccharide-induced acute lung injury by inhibition of CD14 and TLR4 expression

We investigated the effect of propofol (Prop) administration (10 mg kg-1 h-1, intravenously) on lipopolysaccharide (LPS)-induced acute lung injury and its effect on cluster of differentiation (CD) 14 and Toll-like receptor (TLR) 4 expression in lung tissue of anesthetized, ventilated rats. Twenty-four male Wistar rats were randomly divided into three groups of 8 rats each: control, LPS, and LPS+Prop. Lung injury was assayed via blood gas analysis and lung histology, and tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) levels were determined in bronchoalveolar lavage fluid using ELISA. Real-time polymerase chain reaction was used to detect CD14 and TLR4 mRNA levels, and CD14 and TLR4 protein expression was determined by Western blot. The pathological scores were 1.2 ± 0.9, 3.3 ± 1.1, and 1.9 ± 1.0 for the control, LPS, and LPS+Prop groups, respectively, with statistically significant differences between control and LPS groups (P < 0.05) and between LPS and LPS+Prop groups (P < 0.05). The administration of LPS resulted in a significant increase in TNF-α and IL-1β levels, 7- and 3.5-fold, respectively (P < 0.05), while treatment with propofol partially blunted the secretion of both cytokines (P < 0.05). CD14 and TLR4 mRNA levels were increased in the LPS group (1.48 ± 0.05 and 1.26 ± 0.03, respectively) compared to the control group (1.00 ± 0.20 and 1.00 ± 0.02, respectively; P < 0.05), while propofol treatment blunted this effect (1.16 ± 0.05 and 1.12 ± 0.05, respectively; P < 0.05). Both CD14 and TLR4 protein levels were elevated in the LPS group compared to the control group (P < 0.05), while propofol treatment partially decreased the expression of CD14 and TLR4 protein versus LPS alone (P < 0.05). Our study indicates that propofol prevents lung injury, most likely by inhibition of CD14 and TLR4 expression.

Genetic polymorphisms in innate immunity receptors do not predict the risk of bacterial and fungal infections and acute rejection after liver transplantation

INTRODUCTION

We studied the influence of a broad range of genetic variants in recipient and donor innate immunity receptors on bacterial and fungal infections and acute rejection after liver transplantation (LT).

METHODS

Seventy-six polymorphisms in TLR 1-10, NOD2, LBP, CD14, MD2, SIGIRR, Ficolins 1, -2, and -3, MASP 1, -2, and -3, and the complement receptor C1qR1 were determined in 188 LT recipients and 135 of their donors. Associations with clinically significant infections and acute rejection were analyzed for 50 polymorphisms. Significant associations were validated in an independent cohort of 181 recipients and 167 donors.

RESULTS

Three recipient polymorphisms and 3 donor polymorphisms were associated with infections in the identification cohort, but none of these associations were confirmed in the validation cohort. Three donor polymorphisms were associated with acute rejection in the identification cohort, but not in the validation cohort.

CONCLUSION

In contrast to their effect in the general population, 50 common genetic variations in innate immunity receptors do not influence susceptibility to bacterial/fungal infections after LT. In addition, no reproducible associations with acute rejection after LT were observed. Likely, transplant-related factors play a superior role as risk factors for bacterial/fungal infections and acute rejection after LT.

Toll-like receptors and opportunities for new sepsis therapeutics

Serious infection and the patient's response (sepsis) is a serious health problem that, even today, is associated with a mortality rate of 30 %-50 %. The phases of severe sepsis include an early hyperinflammatory response to pathogens and a late immunosuppressed phase. Toll-like receptors (TLRs) are a family of transmembrane innate immune receptors that play a major role in both phases of sepsis. Here, their physiology and the therapeutic strategies employed to date are reviewed. Currently, there are no approved therapies targeting TLRs, but it is anticipated that in the future, the less-studied TLRs, such as TLR3, TLR7, and TLR9, will evolve therapeutic targets, perhaps predominantly with agonists, versus the usual antagonist strategies. Furthermore, accurately characterizing the stage of sepsis will be essential to directing appropriate therapeutic choices.

The role of CD14 gene promoter polymorphism in tuberculosis susceptibility

BACKGROUND

CD14 is expressed principally by cells of monocyte/macrophage lineage and plays a pivotal role in the innate immunity to intracellular infections. Recent research findings have revealed an association between the CD14 gene promoter polymorphism and several major infectious diseases.

OBJECTIVE

The aim of the present study was to investigate the association between the CD14-159C/T polymorphism and tuberculosis in a Turkish population.

METHODS

For this purpose, 88 consecutive patients with tuberculosis (63 pulmonary, 25 extrapulmonary) and 116 control subjects were enrolled into a prospective study. We determined CD14-159 genotypes by polymerase chain reaction - restriction fragment length polymorphism analysis and also measured serum concentrations of soluble CD14 (sCD14) by using a quantitative sandwich enzyme immunoassay technique.

RESULTS

There was no significant difference in terms of genotype distribution between patients with tuberculosis (CC 18.2%, CT 48.9%, TT 33.0%) and controls (CC 12.9%, CT 50.9%, TT 36.2%) or between patients with pulmonary and extrapulmonary tuberculosis. Serum levels of sCD14 were significantly increased in patients with active tuberculosis compared to those with inactive tuberculosis and healthy controls (p<0.001). However, levels of sCD14 were not associated with any genotypes of CD14-159.

CONCLUSION

The genotyping findings of the present study do not support a role for the CD14-159C/T polymorphism in the development of tuberculosis, at least in the geographical region of central Anatolia. Significantly elevated serum sCD14 levels in patients with active disease reflect the importance of the mononuclear phagocytic system activation in tuberculosis.

Genetic variants of the MBL2 gene are associated with mortality in pneumococcal sepsis

Studies evaluating associations between polymorphisms of innate immunity genes and prognosis of infectious diseases have yielded conflicting results. Our aim was to assess the impact on mortality of different genotypic variants of the innate immunity in patients with pneumococcal sepsis. All adults admitted to the hospital with diagnosis of sepsis caused by Streptococcus pneumoniae were enrolled and single-nucleotide polymorphisms (SNP) in mannose-binding lectin 2 (MBL2), toll-like receptor (TLR) 2, TLR4, and Fcγ receptor IIa genes were genotyped. Underlying diseases, severity of illness, and antibiotic management were also recorded. We included 117 patients: 98 pneumonias (83.6%), 17 meningitis (14.5%), and 2 patients (1.9%) with primary pneumococcal bacteremia. Allelic variants of the MBL2 gene (individuals heterozygous or homozygous for one of the 3 allelic variants B, C, and D: AO/OO) were present in 37 patients (32%), T399I polymorphism in TLR4 in 19 (16.2%), TLR4 D299G/T399I in 11 (9.4%), TLR2 R753Q in 3 (2.5%), and FcγRIIa-R/R131 in 26 patients (23%). Factors associated independently with in-hospital mortality were SNP MBL2 AO/OO (adjusted hazard ratios [aHR] 3.2, 95% confidence interval [CI] 1.01-9.8) and septic shock (aHR 15.3, 95% CI 3.5-36.5), whereas first adequate antibiotic dose ≤ 4 h was a protective factor (aHR 0.2, 95% CI 0.06-0.8). SNP MBL2 AO/OO (aHR 2.2, 95% CI 1.1-8.1) remained as a variable independently associated with 90-day mortality. In conclusion, variant alleles in the MBL2 gene are independently associated with in-hospital and medium-term mortalities in patients admitted to the hospital with pneumococcal sepsis.

Innate immunity gene single nucleotide polymorphisms and otitis media

OBJECTIVE

Toll-like receptors (TLR) activate the innate immune system. Single nucleotide polymorphisms (SNPs) in TLR genes are linked to increased susceptibility to infections. TLR4-deficient mice have increased incidence and duration of otitis media. We hypothesize that SNPs in TLR genes are more common in otitis-prone children than in children without a history of otitis media.

METHODS

Cases (n=70) included children undergoing surgery for otitis media. Control subjects (n=70) included children undergoing surgery for non-otologic indication. Genomic DNA was extracted from blood samples. RT-PCR genotyping was performed for TLR2 (rs5743708), TLR4 (rs4986790 and rs4986791), TLR9 (rs5743836 & rs187084), and CD14 (rs2569190).

RESULTS

There were no significant differences between the groups in family history, day care, smoke exposure, allergies or prevalence of the SNPs. The most common pre-op diagnosis in control subjects was obstructive sleep apnea (OSA).

CONCLUSIONS

TLR2, TLR4, TLR9 and CD14 gene SNPs were not more prevalent in otitis-prone children.

Genetics and genomics in pediatric septic shock

OBJECTIVES

Pediatric septic shock continues to be an important public health problem. Several investigative groups have applied genetic and genomic approaches as a means of identifying novel pathways and therapeutic targets, discovery of sepsis-related biomarkers, and identification of septic shock subclasses. This review will highlight studies in pediatric sepsis with a focus on gene association studies and genome-wide expression profiling.

DATA SOURCES

A summary of published literature involving gene association and expression profiling studies specifically involving pediatric sepsis and septic shock.

SUMMARY

Several polymorphisms of genes broadly involved in inflammation, immunity, and coagulation have been linked with susceptibility to sepsis, or outcome of sepsis in children. Many of these studies involve meningococcemia, and the strongest association involves a functional polymorphism of the plasminogen activator inhibitor-1 promoter region and meningococcal sepsis. Expression profiling studies in pediatric septic shock have identified zinc supplementation and inhibition of matrix metalloproteinase-8 activity as potential, novel therapeutic approaches in sepsis. Studies focused on discovery of sepsis-related biomarkers have identified interleukin-8 as a robust outcome biomarker in pediatric septic shock. Additional studies have demonstrated the feasibility and clinical relevance of gene expression-based subclassification of pediatric septic shock.

CONCLUSIONS

Pediatric sepsis and septic shock are increasingly being studied by genetic and genomic approaches and the accumulating data hold the promise of enhancing our future approach to this ongoing clinical problem.

B cell TLRs and induction of immunoglobulin class-switch DNA recombination

Toll-like receptors (TLRs) are a family of conserved pattern recognition receptors (PRRs). Engagement of B cell TLRs by microbe-associated molecular patterns (MAMPs) induces T-independent (TI) antibody responses and plays an important role in the early stages of T-dependent (TD) antibody responses before specific T cell help becomes available. The role of B cell TLRs in the antibody response is magnified by the synergy of B cell receptor (BCR) crosslinking and TLR engagement in inducing immunoglobulin (Ig) class switch DNA recombination (CSR), which crucially diversifies the antibody biological effector functions. Dual BCR/TLR engagement induces CSR to all Ig isotypes, as directed by cytokines, while TLR engagement alone induces marginal CSR. Integration of BCR and TLR signaling results in activation of the canonical and non-canonical NF-κB pathways, induction of activation-induced cytidine deaminase (AID) and germline transcription of IgH switch (S) regions. A critical role of B cell TLRs in CSR and the antibody response is emphasized by the emergence of several TLR ligands as integral components of vaccines that greatly boost humoral immunity in a B cell-intrinsic fashion.

Polymorphisms in Toll-like receptors 2, 4, and 9 are highly associated with hearing loss in survivors of bacterial meningitis

Genetic variation in innate immune response genes contributes to inter-individual differences in disease manifestation and degree of complications upon infection. We recently described an association of single nucleotide polymorphisms (SNPs) in TLR9 with susceptibility to meningococcal meningitis (MM). In this study, we investigate the association of SNPs in multiple pathogen recognition and immune response genes with clinical features that determine severity and outcome (especially hearing loss) of childhood MM and pneumococcal meningitis (PM). Eleven SNPs in seven genes (TLR2, TLR4, TLR9, NOD1, NOD2, CASP1, and TRAIL) were genotyped in 393 survivors of childhood bacterial meningitis (BM) (327 MM patients and 66 PM patients). Genotype distributions of single SNPs and combination of SNPs were compared between thirteen clinical characteristics associated with severity of BM. After correction for multiple testing, TLR4+896 mutant alleles were highly associated with post-meningitis hearing loss, especially MM (p= 0.001, OR 4.0 for BM, p= 0.0004, OR 6.2 for MM). In a multigene analysis, combined carriership of the TLR2+2477 wild type (WT) with TLR4+896 mutant alleles increases the risk of hearing loss (p<0.0001, OR 5.7 in BM and p= 0.0001, OR 7.6 in MM). Carriage of one or both mutant alleles in TLR4+896 and TLR9 -1237 increases the risk for hearing loss (p = 0.0006, OR 4.1 in BM). SNPs in immune response genes contribute to differences in clinical severity and outcome of BM. The TLR system seems to play an important role in the immune response to BM and subsequent neuronal damage as well as in cochlear inflammation. Genetic markers may be used for identification of high-risk patients by creating prediction rules for post-meningitis hearing loss and other sequelae, and provide more insight in the complex immune response in the CNS possibly resulting in new therapeutic interventions.

The Role of TLR2 in Infection and Immunity

Toll-like receptors (TLRs) are recognition molecules for multiple pathogens, including bacteria, viruses, fungi, and parasites. TLR2 forms heterodimers with TLR1 and TLR6, which is the initial step in a cascade of events leading to significant innate immune responses, development of adaptive immunity to pathogens and protection from immune sequelae related to infection with these pathogens. This review will discuss the current status of TLR2 mediated immune responses by recognition of pathogen-associated molecular patterns (PAMPS) on these organisms. We will emphasize both canonical and non-canonical responses to TLR2 ligands with emphasis on whether the inflammation induced by these responses contributes to the disease state or to protection from diseases.

Genetic predisposition to respiratory infection and sepsis

Genetic variations, in part, determine individual susceptibility to sepsis and pneumonia. Advances in genetic sequence analysis as well as high throughput platform analysis of gene expression has allowed for a better understanding of immunopathogenesis during sepsis. Differences in genes can also modulate immune and inflammatory response during sepsis thereby translating to differences in clinical outcomes. An increasing number of candidate genes have been implicated to play a role in sepsis susceptibility, most of which are controversial with few exceptions. This does not refute the significance of genetic polymorphisms in sepsis, but rather highlights the difficulties and pitfalls related to genetic association studies. These difficulties include differences in study design such as heterogeneous patient cohorts and differences in pathogenic organisms, linkage disequilibrium, and lack of power for detailed haplotype analysis or examination of gene-gene interactions. There is extensive diversity in the pathways of inflammation and immune response during sepsis making it even harder to prove the functional and clinical significance of one single genetic polymorphism which could be easily masqueraded or compensated by other upstream or downstream events of the pathway involved. The majority of studies have analysed candidate genes in isolation from other possible polymorphisms. It is likely that susceptibility to sepsis is the result of polymorphisms from multiple genes rather than one single mutation. Future studies should aim for multi-centered collaborative approach looking at genome wide association or gene profiling to provide a more complete appraisal of the key genetic players in determining genetic susceptibility to sepsis. This review paper will summarise the prominent candidate gene polymorphisms with known functional changes or those with haplotype data. In addition, a summary of the expanding research in the field of epigenetics and post-sepsis immunosuppression will be discussed.

MBL Deficiency as Risk of Infection and Autoimmunity

In pathogen recognition by C-type lectins, several levels of complexity can be distinguished; these might modulate the immune response in different ways. Firstly, the pathogen-associated molecular pattern repertoire expressed at the microbial surface determines the interactions with specific receptors (Fig. 42.1). Secondly, each immune cell type possesses a specific set of pathogen-recognition receptors. Thirdly, changes in the cell-surface distribution of C-type lectins regulate carbohydrate binding by modulating receptor affinity for different ligands. Crosstalk between these receptors results in a network of multimolecular complexes, adding a further level of complexity in pathogen recognition (Cambi and Figdor 2005; Thiel et al. 2006) (see 10.1007/978-3-7091-1065-2_23). MBL deficiency is genetically determined and predisposes to recurrent infections and chronic inflammatory diseases. MBL deficiency has been implicated in susceptibility and course of viral, bacterial, fungal, and protozoan infection. More than 10% of the general population may, depending on definition, be classified as MBL deficient, underlining the redundancy of the immune system. MBL-disease association studies have been a fruitful area of research, which implicates a role for MBL in infective, inflammatory and autoimmune disease processes. MBL deficiency predisposes both to infection by extra-cellular pathogens and to autoimmune disease.

Beyond single-marker analyses: mining whole genome scans for insights into treatment responses in severe sepsis

Management of severe sepsis, an acute illness with high morbidity and mortality, suffers from the lack of effective biomarkers and largely empirical predictions of disease progression and therapeutic responses. We conducted a genome-wide association study using a large randomized clinical trial cohort to discover genetic biomarkers of response to therapy and prognosis utilizing novel approaches, including combination markers, to overcome limitations of single-marker analyses. Sepsis prognostic models were dominated by clinical variables with genetic markers less informative. In contrast, evidence for gene-gene interactions were identified for sepsis treatment responses with genetic biomarkers dominating models for predicting therapeutic responses, yielding candidates for replication in other cohorts.

Toll-like receptor 1 polymorphisms increase susceptibility to candidemia

BACKGROUND

Candidemia is a severe invasive fungal infection with high mortality. Recognition of Candida species is mediated through pattern recognition receptors such as Toll-like receptors (TLRs). This study assessed whether genetic variation in TLR signaling influences susceptibility to candidemia.

METHODS

Thirteen mostly nonsynonymous single nucleotide polymorphisms (SNPs) in genes encoding TLRs and signaling adaptors MyD88 and Mal/TIRAP were genotyped in 338 patients (237 white, 93 African American, 8 other race) with candidemia and 351 noninfected controls (263 white, 88 African American). The SNPs significant in univariate analysis were further analyzed with multivariable logistic regression to determine association with clinical outcomes. Functional consequences of these polymorphisms were assessed via in vitro stimulation assays.

RESULTS

Analyses of TLR SNPs revealed that 3 TLR1 SNPs (R80T, S248N, I602S) were significantly associated with candidemia susceptibility in whites. This association was not found in African Americans, likely due to lower power in this smaller study population. Furthermore, these TLR1 polymorphisms displayed impaired cytokine release by primary monocytes. No associations with susceptibility to candidemia were observed for SNPs in TLR2, TLR4, TLR6, TLR9, MyD88, or TIRAP.

CONCLUSIONS

Nonsynonymous SNPs in TLR1 are associated with impaired TLR1 function, decreased cytokine responses, and predisposition to candidemia in whites.