Functional assessment of Toll-like receptor 2 and its relevance in patients with Staphylococcus aureus infection of joint prosthesis. Hum Immunol. 2011;72:47-53. [PMID: 20937339 DOI: 10.1016/j.humimm.2010.10.001]

Integrating Genome-Wide Polygenic Risk Scores With Nongenetic Models to Predict Surgical Site Infection After Total Knee Arthroplasty Using United Kingdom Biobank Data

BACKGROUND

Prediction of the risk of developing surgical site infection (SSI) in patients following total knee arthroplasty (TKA) is of clinical importance. Genetic susceptibility is involved in developing TKA-related SSI. Previously reported models for predicting SSI were constructed using nongenetic risk factors without incorporating genetic risk factors. To address this issue, we performed a genome-wide association study (GWAS) using the UK Biobank database.

METHODS

Adult patients who underwent primary TKA (n = 19,767) were analyzed and divided into SSI (n = 269) and non-SSI (n = 19,498) cohorts. Nongenetic covariates, including demographic data and preoperative comorbidities, were recorded. Genetic variants associated with SSI were identified by GWAS and included to obtain standardized polygenic risk scores (zPRS, an estimate of genetic risk). Prediction models were established through analyses of multivariable logistic regression and the receiver operating characteristic curve.

RESULTS

There were 4 variants (rs117896641, rs111686424, rs8101598, and rs74648298) achieving genome-wide significance that were identified. The logistic regression analysis revealed 7 significant risk factors: increasing zPRS, decreasing age, men, chronic obstructive pulmonary disease, diabetes mellitus, rheumatoid arthritis, and peripheral vascular disease. The areas under the receiver operating characteristic curve were 0.628 and 0.708 when zPRS (model 1) and nongenetic covariates (model 2) were used as predictors, respectively. The areas under the receiver operating characteristic curve increased to 0.76 when both zPRS and nongenetic covariates (model 3) were used as predictors. A risk-prediction nomogram was constructed based on model 3 to visualize the relative effect of statistically significant covariates on the risk of SSI and predict the probability of developing SSI. Age and zPRS were the top 2 covariates that contributed to the risk, with younger age and higher zPRS associated with higher risks.

CONCLUSIONS

Our GWAS identified 4 novel variants that were significantly associated with susceptibility to SSI following TKA. Integrating genome-wide zPRS with nongenetic risk factors improved the performance of the model in predicting SSI.

Interrelationship between Toll-like receptors and infection after orthotopic liver transplantation

Early microbial recognition by the innate immune system is accomplished by Toll-like receptors (TLRs), with resultant initiation of a pro-inflammatory response against infecting organisms. In spite of presence of an abundance of Toll-like receptors on the surface of the liver, gut bacteria does not elicit an inflammatory reaction in healthy individuals due to tolerance to these TLRs, suggesting that the inflammatory responses seen in the liver are the result of breakdown of this tolerance. While orthotopic liver transplantation is often life saving in many instances, death following this procedure is most commonly due to infection that occurs in up to 80% of transplant recipients, most commonly due to microbial causes in up to 70% of cases and viral infections in 20%, while fungal infections affect only 8% of cases. The probability of acquiring infection following hepatic transplantation is heightened due to affection of the innate immune defense mechanisms of the host following this procedure. Single nucleotide polymorphisms of TLRs have been associated with increased likelihood of either development of post-transplant infection or eradication of infecting organism. However, conflicting reports from other studies reveal that prevalence of this single nucleotide polymorphism is not increased in infected patients.

Toll-like receptor 9 (TLR-9) promotor polymorphisms and gene expression are associated with persistent Staphylococcus aureus nasal carriage

OBJECTIVES

Toll-like receptor (TLR) 9 could have importance in human Staphylococcus aureus immunity, but population-level evidence for this hypothesis is missing.

METHODS

We phenotyped S. aureus nasal carriage of 603 volunteers using four consecutive swabs, genotyped TLR9 promotor variants in 106 persistent carriers and 219 noncarriers, measured TLR9-mRNA expression in whole blood after stimulation with viable S. aureus and studied mutual associations of carriage, transcriptional activity and single nucleotide polymorphisms while accounting for sex and hormone contraceptive use (HCU).

RESULTS

The -1486 (rs187084) and -1237 (rs5743836) CT haplotype was more common in noncarriers (185/438, 42%) than in carriers (63/212, 30%), with the TT haplotype showing a reverse association (noncarriers, 180/438, 41%; carriers 117/212, 55%) (χ² p 0.001). Mean TLR9 mRNA expression in whole blood was higher in noncarriers (ratio_{carriers/noncarriers} 0.63; 95% confidence interval, 0.43-0.92; p 0.017). A duplication of TLR9 transcriptional activity lowered the odds of persistent S. aureus carriage by 37% in the overall group (odds ratio = 0.63; 95% confidence interval, 0.42-0.94; p 0.022) and by 54% in women (odds ratio = 0.46; 95% confidence interval, 0.23-0.90; p 0.023). Promotor haplotype and HCU had a combined effect on TLR9 transcription (interaction model): women in the TT (risk) haplotype/HCU^- stratum (baseline) had lower mRNA levels than women in the CT (protective) haplotype/HCU^- (ratio 1.92; p 0.055), the CT haplotype/HCU⁺ (ratio 2.02; p 0.032) and the TT haplotype/HCU⁺ (ratio 2.59; p < 0.004) strata. No such associations were observed in men.

CONCLUSIONS

We provide evidence that TLR9 affects human S. aureus immunity and present potential explanations for differences according to sex in S. aureus colonization and infection.

Excellent Diagnostic Characteristics for Ultrafast Gene Profiling of DEFA1-IL1B-LTF in Detection of Prosthetic Joint Infections

The timely and exact diagnosis of prosthetic joint infection (PJI) is crucial for surgical decision-making. Intraoperatively, delivery of the result within an hour is required. Alpha-defensin lateral immunoassay of joint fluid (JF) is precise for the intraoperative exclusion of PJI; however, for patients with a limited amount of JF and/or in cases where the JF is bloody, this test is unhelpful. Important information is hidden in periprosthetic tissues that may much better reflect the current status of implant pathology. We therefore investigated the utility of the gene expression patterns of 12 candidate genes (TLR1, -2, -4, -6, and 10, DEFA1, LTF, IL1B, BPI, CRP, IFNG, and DEFB4A) previously associated with infection for detection of PJI in periprosthetic tissues of patients with total joint arthroplasty (TJA) (n = 76) reoperated for PJI (n = 38) or aseptic failure (n = 38), using the ultrafast quantitative reverse transcription-PCR (RT-PCR) Xxpress system (BJS Biotechnologies Ltd.). Advanced data-mining algorithms were applied for data analysis. For PJI, we detected elevated mRNA expression levels of DEFA1 (P < 0.0001), IL1B (P < 0.0001), LTF (P < 0.0001), TLR1 (P = 0.02), and BPI (P = 0.01) in comparison to those in tissues from aseptic cases. A feature selection algorithm revealed that the DEFA1-IL1B-LTF pattern was the most appropriate for detection/exclusion of PJI, achieving 94.5% sensitivity and 95.7% specificity, with likelihood ratios (LRs) for positive and negative results of 16.3 and 0.06, respectively. Taken together, the results show that DEFA1-IL1B-LTF gene expression detection by use of ultrafast qRT-PCR linked to an electronic calculator allows detection of patients with a high probability of PJI within 45 min after sampling. Further testing on a larger cohort of patients is needed.

Genetic susceptibility to prosthetic joint infection following total joint arthroplasty: A systematic review

BACKGROUND

Prosthetic joint infection (PJI) is the most common cause of total joint arthroplasty failure and revision surgery. Genetic polymorphisms could be determinant factors for PJI.

METHODS

We performed a systematic research of Medline, Pubmed, Embase, Cochrane Library, and Google Scholar, and identified 11 studies with 34 kinds of gene polymorphisms, were included in the synthesis.

RESULTS

Our data suggest that the C allele and genotype C/C for MBL-550 SNP, genotype A/A for MBL-54 SNP and G allele for MBL-221 SNP increase the risk of PJI, while G allele and genotype G/G for MBL-550 SNP decrease the risk of PJI in Caucasian populations. Several other genes reported by single-center studies also contribute to the genetic susceptibility to septic PJI. No definitive conclusions could be achieved due to the small amount of data in the included studies.

CONCLUSION

Several genes contribute to the genetic susceptibility to PJI following total joint arthroplasty. Further studies will enhance the understanding of PJI, and may inform and direct early interventions.

Toll-like receptor 2 in serum: a potential diagnostic marker of prosthetic joint infection?

Prosthetic joint infection (PJI) is a severe complication of arthroplasty and is still lacking diagnostic gold standards. PJI patients display high Toll-like receptor 2 (TLR2) serum levels, correlating with canonical inflammatory markers (C-reactive protein [CRP], interleukin 6 [IL-6], tumor necrosis factor alpha [TNF-α], and IL-1). Therefore, TLR2 serum levels could be considered a new potential diagnostic tool in the early detection of PJI.

Variation in the IL1B, TNF and IL6 genes and individual susceptibility to prosthetic joint infection

Background

Prosthetic joint infection (PJI) is an important failure mechanism of total joint arthroplasty (TJA). Here we examine whether the particular genetic variants can lead to increased susceptibility to PJI development.

Results

We conducted a genetic-association study to determine whether PJI could be associated with functional cytokine gene polymorphisms (CGP) influencing on innate immunity response. A case–control design was utilized and previously published criteria for PJI were included to distinguish between cases and control subjects with/without TJA. Six single nucleotide polymorphisms (SNPs) located in the genes for interleukin-1beta (SNP: IL1B-511, +3962), tumour necrosis factor alpha (TNF-308, -238) and interleukin-6 (IL6-174, nt565) were genotyped in 303 Caucasian (Czech) patients with TJA (89 with PJI / 214 without PJI), and 168 unrelated healthy Czech individuals without TJA. The results showed that carriers of the less common IL1B−511*T allele were overrepresented in the group of TJA patients with PJI (69%) in comparison with those that did not develop PJI (51%, p = 0.006, p_corr = 0.037) and with healthy controls (55%, p = 0.04, p_corr = N.S.). There was no significant difference in the distribution of the remaining five investigated CGPs and their haplotypes between groups.

Conclusion

A functional variant of the gene encoding for IL-1beta was preliminarily nominated as a genetic factor contributing to the susceptibility to PJI. Our results should be independently replicated; studies on the functional relevance of IL1B gene variants in PJI are also needed.

Deciphering mechanisms of staphylococcal biofilm evasion of host immunity

Biofilms are adherent communities of bacteria contained within a complex matrix. Although host immune responses to planktonic staphylococcal species have been relatively well-characterized, less is known regarding immunity to staphylococcal biofilms and how they modulate anti-bacterial effector mechanisms when organized in this protective milieu. Previously, staphylococcal biofilms were thought to escape immune recognition on the basis of their chronic and indolent nature. Instead, we have proposed that staphylococcal biofilms skew the host immune response away from a proinflammatory bactericidal phenotype toward an anti-inflammatory, pro-fibrotic response that favors bacterial persistence. This possibility is supported by recent studies from our laboratory using a mouse model of catheter-associated biofilm infection, where S. aureus biofilms led to the accumulation of alternatively activated M2 macrophages that exhibit anti-inflammatory and pro-fibrotic properties. In addition, relatively few neutrophils were recruited into S. aureus biofilms, representing another mechanism that deviates from planktonic infections. However, it is important to recognize the diversity of biofilm infections, in that studies by others have demonstrated the induction of distinct immune responses during staphylococcal biofilm growth in other models, suggesting influences from the local tissue microenvironment. This review will discuss the immune defenses that staphylococcal biofilms evade as well as conceptual issues that remain to be resolved. An improved understanding of why the host immune response is unable to clear biofilm infections could lead to targeted therapies to reverse these defects and expedite biofilm clearance.

Homozygosity for the toll-like receptor 2 R753Q single-nucleotide polymorphism is a risk factor for cytomegalovirus disease after liver transplantation

Immunity against cytomegalovirus (CMV) is initiated after its recognition by Toll-like receptor 2 (TLR2). We assessed the association between a single-nucleotide polymorphism (SNP) that impairs TLR2 function and CMV disease in a cohort of 737 liver recipients. Ninety-two of 737 patients (7.1%, 10.9%, 12.3%, and 12.5% by 3, 6, 12, and 24 months, respectively) developed CMV disease. Kaplan-Meier estimation demonstrated an association between TLR2 R753Q SNP homozygosity and CMV disease (P = .044), especially tissue-invasive CMV disease (P = .001). A multivariate Cox proportional hazard model that accounted for other significant predictors demonstrated a significant association between TLR2 R753Q SNP homozygosity and tissue-invasive CMV disease (hazard ratio, 3.407; 95% confidence interval, 1.518-7.644; P = .0029). In conclusion, homozygosity for TLR2 R753Q SNP is a marker for CMV disease risk, especially for tissue-invasive disease, after liver transplantation. This observation supports the critical role of TLR2 in the pathogenesis of CMV disease in humans.

Nasopharyngeal bacterial colonization and gene polymorphisms of mannose-binding lectin and toll-like receptors 2 and 4 in infants

BACKGROUND

Human nasopharynx is often colonized by potentially pathogenic bacteria. Gene polymorphisms in mannose-binding lectin (MBL), toll-like receptor (TLR) 2 and TLR4 have been reported. The present study aimed to investigate possible association between nasopharyngeal bacterial colonization and gene polymorphisms of MBL, TLR2 and TLR4 in healthy infants.

METHODOLOGY/PRINCIPAL FINDINGS

From August 2008 to June 2010, 489 nasopharyngeal swabs and 412 blood samples were taken from 3-month-old healthy Finnish infants. Semi-quantitative culture was performed and pyrosequencing was used for detection of polymorphisms in MBL structural gene at codons 52, 54, and 57, TLR2 Arg753Gln and TLR4 Asp299Gly. Fifty-nine percent of subjects were culture positive for at least one of the four species: 11% for Streptococcus pneumoniae, 23% for Moraxella catarrhalis, 1% for Haemophilus influenzae and 25% for Staphylococcus aureus. Thirty-two percent of subjects had variant types in MBL, 5% had polymorphism of TLR2, and 18% had polymorphism of TLR4. Colonization rates of S. pneumoniae and S. aureus were significantly higher in infants with variant types of MBL than those with wild type (p = .011 and p = .024). Colonization rates of S. aureus and M. catarrhalis were significantly higher in infants with polymorphisms of TLR2 and of TLR4 than those without (p = .027 and p = .002).

CONCLUSIONS

Our study suggests that there is an association between nasopharyngeal bacterial colonization and genetic variation of MBL, TLR2 and TLR4 in young infants. This finding supports a role for these genetic variations in susceptibility of children to respiratory infections.

Protective role of IL-1β against post-arthroplasty Staphylococcus aureus infection

MyD88 is an adapter molecule that is used by both IL-1R and TLR family members to initiate downstream signaling and promote immune responses. Given that IL-1β is induced after Staphylococcus aureus infections and TLR2 is activated by S. aureus lipopeptides, we hypothesized that IL-1β and TLR2 contribute to MyD88-dependent protective immune responses against post-arthroplasty S. aureus infections. To test this hypothesis, we used a mouse model of a post-arthroplasty S. aureus infection to compare the bacterial burden, biofilm formation and neutrophil recruitment in IL-1β-deficient, TLR2-deficient and wild-type (wt) mice. By using in vivo bioluminescence imaging, we found that the bacterial burden in IL-1β-deficient mice was 26-fold higher at 1 day after infection and remained 3- to 10-fold greater than wt mice through day 42. In contrast, the bacterial burden in TLR2-deficient mice did not differ from wt mice. In addition, implants harvested from IL-1β-deficient mice had more biofilm formation and 14-fold higher adherent bacteria compared with those from wt mice. Finally, IL-1β-deficient mice had ∼50% decreased neutrophil recruitment to the infected postoperative joints than wt mice. Taken together, these findings suggest a mechanism by which IL-1β induces neutrophil recruitment to help control the bacterial burden and the ensuing biofilm formation in a post-surgical joint.

Toll-like receptors are potential therapeutic targets in rheumatoid arthritis

Toll-like receptors (TLRs) are found on the membranes of pattern recognition receptors and not only play important roles in activating immune responses but are also involved in the pathogenesis of inflammatory disease, injury and cancer. Furthermore, TLRs are also able to recognize endogenous alarmins released by damaged tissue and necrosis and/or apoptotic cells and are present in numerous autoimmune diseases. Therefore, the release of endogenous TLR ligands plays an important role in initiating and driving inflammatory diseases. Increasing data suggest a role for TLR signaling in rheumatoid arthritis, which is an autoimmune disease. Although their involvement is not comprehensively understood, the TLRs signaling transducers may provide potential therapeutic targets.