TLR3 gene polymorphisms and liver disease manifestations in chronic hepatitis C

TLR3 polymorphisms in HIV infected individuals naïve to ART

BACKGROUND

TLR3 polymorphisms affect the risk of HIV infection and modify the disease course. Consequently, we analyzed the association of TLR3 polymorphism (rs5743312, rs3775296, and rs3775291) with susceptilbity to HIV-1 acquisition and disease progression.

METHOD

This is a cross-sectional study. Genotyping of TLR3 polymorphisms were completed by the utilization of the PCR-RFLP technique in 153 HIV naive subjects and 158 healthy controls.

RESULT

A haplotype is a physical grouping of genomic variants that tend to be inherited together. The TCC haplotype was increased in HIV infected individuals compared with healthy controls (0.05% versus 0.03%). TLR3 rs3775291CT genotype was associated to the early stage of HIV infection (OR=2.19, P=0.04), with a higher occurrence in advance stage of HIV infection when contrasted with healthy controls (41.2% versus 32.3%). TLR3 rs3775296 CA genotype was likely to be associated with intermediate stage of HIV infection (19.5% versus 31.6%, OR=0.42, P=0.06). TLR3 rs5743312TT genotype was used to be greater prevalence in advanced stage of HIV infection compared with healthy controls (2.9% versus 1.9%). TLR3 rs3775296CA genotype was less prevalent in HIV subjects devouring tobacco when contrasted with non-users (9.1% versus 34.9%, OR=0.25, P=0.09). TLR3 rs3775296AA and rs3775291CT and TT genotypes have been overrepresented in HIV subjects using alcohol when contrasted with non-users (5.6% versus 1.1%, OR=1.83, P=0.67; 50.0% versus 42.2%, OR=1.84, P=0.31; 5.6% versus 3.3%, OR=2.70, P=0.50). In multivariate examination, rs5743312TT genotype showed a greater risk for HIV infection (OR=1.86, P=0.50).

CONCLUSION

TLR3 rs3775291 C/T polymorphism may assist the risk of disease progression in alcohol consumers. TLR3 rs3775291 CT genotype may enhance the disease progression whereas the TLR3 rs3775296 CA genotype may protect for disease progression.

Genetic Polymorphism in Toll-Like Receptor 3 and Interferon Regulatory Factor 3 in Hepatitis C Virus-Infected Patients: Correlation with Liver Cirrhosis

Host genetic factors could play a primary role in determining the risk for cirrhosis development in chronic hepatitis C virus (HCV)-infected patients. We designed this work to study the effect of single-nucleotide polymorphism (SNP) in Toll-like receptor 3 (TLR3) and interferon regulatory factor (IRF) on the risk of HCV-related cirrhosis. This study enrolled 139 Egyptian HCV-infected patients. They were divided into patients with cirrhotic (56) and noncirrhotic (83) liver. Genotyping of rs3775291 F459F (+1234C/T) and rs3775290 L412F (+1377C/T) in TLR3 and IRF3 rs2304204 (-925A/G) was performed by restriction fragment length polymorphism-polymerase chain reaction. Although there is no significant difference in genotype and allele distribution of +1377C/T of TLR3 gene between cirrhotic and noncirrhotic subjects, CC (odds ratio [OR] = 1.572, 95% confidence interval [CI]: 0.781-3.164); TT (OR = 1.463, 95% CI: 0.351-6.104) genotypes might be considered as risk factors for liver cirrhosis. On the contrary, the analysis revealed that only one genotype (CC) and one allele (C) were detected in +1234C/T SNP, with the total disappearance of CT/TT genotypes and T allele in all subjects. On the contrary, lower frequency has been found for the AG genotype of the IRF3 (-925A/G) gene in cirrhotic patients compared with noncirrhotic ones, indicating that AG is a protective genotype (OR = 0.509, 95% CI: 0.256-1.012). Our data stressed the association of AG genotype SNP in IRF3 (-925A/G) in protection against the worth outcome of HCV infection.

The association of single nucleotide polymorphisms of Toll-like receptor 3, Toll-like receptor 7 and Toll-like receptor 8 genes with the susceptibility to HCV infection

BACKGROUND

Single nucleotide polymorphisms (SNPs) of Toll-like receptors (TLRs) are linked with functional modification of cytokine responses. In chronic hepatitis C virus (HCV) infection, studies of TLR polymorphisms have primarily targeted receptor pathways implicated in viral immune responses. We hypothesized that one or more variant(s) of TLR3, TLR7 and TLR8 are associated with different outcomes of HCV infection.

MATERIALS & METHODS

A total of 3368 subjects from 850 families were recruited and divided into three main groups categorized as chronic HCV CHC spontaneous viral clearance (SVC), and controls. All individuals were genotyped for three SNPs for TLR3, two SNPs for TLR7, and two SNPs for TLR8 using allelic discrimination real-time PCR.

RESULTS

Carriage of the C allele in three SNPs of TLR3 (rs3775290, rs3775291, and rs5743312), the C allele in TLR7 (rs3853839) in females only, and the C allele in TLR8 (rs3764879) in males only were significantly higher in SVC group than CHC group (P < 0.001), while carriage of the T allele in TLR7 (rs179008) in females only and the A allele in TLR8 (rs3764880) in both males and females were significantly higher in CHC infection more than SVC group (P < 0.001).

CONCLUSION

The C allele is protective of HCV in TLR3, TLR7 (rs3853839) in females only, and TLR8 (rs3764879) in males only, while risk of infection is linked to the T allele in TLR7 (rs179008) in females only and the A allele in TLR8 (rs3764880) in both sexes.

Polymorphisms in the Toll-like receptor 3 (TLR3) gene are associated with the natural course of hepatitis B virus infection in Caucasian population

Innate immunity can induce spontaneous hepatitis B surface antigen (HBsAg) seroclearance (SC) of hepatitis B virus (HBV) infection or transition towards an inactive carrier state. Toll-like receptor (TLR) 3 signalling has been linked to these processes. Alterations in the TLR3 gene might impair immune responses against HBV. In our study, we analysed the impact of the TLR3 polymorphisms rs3775291 and rs5743305 on the natural course of HBV infection. In this retrospective study, a Caucasian cohort of 621 patients with chronic HBV infection (CHB), 239 individuals with spontaneous HBsAg SC, and 254 healthy controls were enrolled. In the CHB group, 49% of patients were inactive carriers, and 17% were HBeAg-positive. The TLR3 rs3775291 A allele was associated with a reduced likelihood of spontaneous HBsAg SC and HBeAg SC, and an increased risk of developing chronic hepatitis B. In haplotype analysis, the haplotype including both risk variants rs3775291A and rs5743305A had the lowest likelihood of HBsAg SC. Further research in larger cohorts and functional analyses are needed to shed light on the impact of TLR3 signalling.

Association of Toll-Like Receptor 3 and Toll-Like Receptor 9 Single Nucleotide Polymorphisms with Hepatitis C Virus Infection and Hepatic Fibrosis in Egyptian Patients

Toll-like receptors (TLRs) are recognized as fundamental contributors to the immune system function against infections. Hepatitis C virus (HCV) infection represents a global health problem especially in Egypt having the highest HCV prevalence worldwide where HCV infection is a continuing epidemic. The aim of the present study was to investigate the possible association between genetic variation in TLR-3 and TLR-9 and HCV infection and hepatic fibrosis in chronic HCV-positive Egyptian patients. The present study included 100 naïve chronic HCV-positive patients and 100 age- and sex-matched healthy controls. Genotyping of TLR-3 (_7 C/A [rs3775296]), TLR-3 (c.1377C/T [rs3775290]) and TLR-9 (1237T/C [rs5743836]) were done by polymerase chain reaction restriction fragment length polymorphism technique. Frequency of polymorphic genotypes in TLR-3 (_7 C/A), TLR-3 (c.1377C/T) and TLR-9 (1237T/C) were not significantly different between studied HCV-positive patients and controls with P values 0.121, 0.112, and 0.683, respectively. TLR-3 c.1377 T-allele was associated with advanced stage of hepatic fibrosis (P = 0.003).

Association of Toll-Like Receptor 3 Single-Nucleotide Polymorphisms and Hepatitis C Virus Infection

Toll-like receptor 3 (TLR3) plays a key role in innate immunity by recognizing pathogenic, double-stranded RNAs. Thus, activation of TLR3 is a major factor in antiviral defense and tumor eradication. Although downregulation of TLR3 gene expression has been mainly reported in patients infected with hepatitis C virus (HCV), the influence of TLR3 genotype on the risk of HCV infection, HCV-related cirrhosis, and/or hepatocellular carcinoma (HCC) remains to be determined. Single-nucleotide polymorphisms (SNPs) within the TLR3 gene and their associations with HCV-related disease risk were investigated in a Saudi Arabian population in this study. Eight TLR3 SNPs were analyzed in 563 patients with HCV, which consisted of 437 patients with chronic HCV infections, 88 with HCV-induced liver cirrhosis, and 38 with HCC. A total of 599 healthy control subjects were recruited to the study. Among the eight TLR3 SNPs studied, the rs78726532 SNP was strongly associated with HCV infection when compared to that in healthy control subjects. The rs5743314 was also strongly associated with HCV-related liver disease progression (cirrhosis and HCC). In summary, these results indicate that distinct genetic variants of TLR3 SNPs are associated with HCV infection and HCV-mediated liver disease progression in the Saudi Arabian population.

Investigation of 1377C/T polymorphism of the Toll-like receptor 3 among patients with chronic hepatitis B

The immunopathogenesis of chronic hepatitis B (CHB) has not been clarified yet. Toll-like receptors (TLR) are a receptor family that initiates immunity with exogenous-endogenous ligands and plays a role in the pathogenesis of infections. In this study, we aimed to investigate the frequency of TLR 3 1377C/T (rs3775290) polymorphism and its role in patients with CHB. We included 50 healthy individuals as control group and 73 active and 43 inactive hepatitis B patients. All DNA samples were isolated from blood samples. For the detection of TLR 3 1377C/T single-nucleotide polymorphism, restriction fragment length polymorphism was used. A statistically significant difference was determined in Hepatitis B virus (HBV) DNA levels of CHB patients with the CC, CT, and TT genotypes (p = 0.013). The highest levels of HBV DNA were detected in individuals with TT genotypes. Additionally, the frequency of CC genotype was higher in the active CHB patients compared with that of the inactive CHB patients (p = 0.044). No statistically significant difference in TLR 3 1377C/T polymorphism was detected between healthy controls and the hepatitis B patients (p = 0.342). In conclusion, HBV DNA level was higher in the individuals with TT genotype, and CC genotype was more frequent in the active CHB patients. These results suggest a possible association between CHB and TLR 3 gene (1377C/T) polymorphism.

Toll-like receptor signaling in primary immune deficiencies

Toll-like receptors (TLRs) recognize common microbial or host-derived macromolecules and have important roles in early activation of the immune system. Patients with primary immune deficiencies (PIDs) affecting TLR signaling can elucidate the importance of these proteins to the human immune system. Defects in interleukin-1 receptor-associated kinase-4 and myeloid differentiation factor 88 (MyD88) lead to susceptibility to infections with bacteria, while mutations in nuclear factor-κB essential modulator (NEMO) and other downstream mediators generally induce broader susceptibility to bacteria, viruses, and fungi. In contrast, TLR3 signaling defects are specific for susceptibility to herpes simplex virus type 1 encephalitis. Other PIDs induce functional alterations of TLR signaling pathways, such as common variable immunodeficiency in which plasmacytoid dendritic cell defects enhance defective responses of B cells to shared TLR agonists. Dampening of TLR responses is seen for TLRs 2 and 4 in chronic granulomatous disease (CGD) and X-linked agammaglobulinemia (XLA). Enhanced TLR responses, meanwhile, are seen for TLRs 5 and 9 in CGD, TLRs 4, 7/8, and 9 in XLA, TLRs 2 and 4 in hyper IgE syndrome, and for most TLRs in adenosine deaminase deficiency.

TLR3 polymorphisms are associated with virologic response to hepatitis C virus (HCV) treatment in HIV/HCV coinfected patients

BACKGROUND

Toll-like receptor-3 (TLR3) is a cellular receptor that may recognize double-stranded RNA (dsRNA) from viruses, resulting in production of proinflammatory cytokines and interferons, which are important for the adaptive immune response.

OBJECTIVES

To analyze the association between Toll-like receptor-3 (TLR3) polymorphisms (rs3775291 and rs13126816) and virologic response to pegylated interferon-alpha plus ribavirin (pegIFNα/RBV) therapy in HIV/HCV coinfected patients.

STUDY DESIGN

We performed a retrospective study in 321 naïve patients treated with pegIFNα/RBV. Genotyping was performed by using the GoldenGate(®) assay with VeraCode(®). The outcome variables were early virologic response (EVR) and sustained virologic response (SVR).

RESULTS

In a multivariate analysis, rs3775291 A allele decreased the likelihood of achieving EVR (aOR = 0.20; p = 0.018) and SVR (aOR = 0.38; p = 0.024). Regarding rs13126816, the percentage of EVR decreased with each minor A allele (p = 0.034) in HCV-GT2/3 patients, although no significant association was obtained in the multivariate analysis (p = 0.076). Regarding TLR3 haplotypes (comprised of rs3775291 and rs13126816), GT2/3 patients with AA haplotype had decreased odds of achieving EVR (p = 0.030), whereas GG haplotype increased the likelihood (p = 0.018). Regarding SVR, GG haplotype carriers had increased odds of achieving SVR (p = 0.019, p = 0.043 and p = 0.070 for all, GT2/3 and GT1/4 patients, respectively). Besides, GT1/4 patients with GA haplotype had lower odds of achieving SVR (p = 0.039).

CONCLUSIONS

Our study shows the first evidence that two TLR3 polymorphisms (rs3775291 and rs13126816) seem to be related to the HCV therapy response in HCV/HIV coinfected patients.

Mutations in toll-like receptor 3 are associated with elevated levels of rotavirus-specific IgG antibodies in IgA-deficient but not IgA-sufficient individuals

Double-stranded RNA (dsRNA) triggers immune-mediated responses through toll-like receptor 3 (TLR3), which is involved in innate antiviral defense. Low expression of TLR3 was recently suggested to contribute to susceptibility to rotavirus infection. Thus, we investigated the role of two TLR3 polymorphisms (rs3775291 and rs5743305), both of which resulted in reduced protein function or expression, in healthy blood donors and IgA-deficient (IgAD) individuals. These polymorphisms were associated with elevated rotavirus-specific IgG titers in IgAD individuals but not in healthy individuals. Thus, we propose that TLR3 signaling does not contribute to the rotavirus-specific antibody response in IgA-sufficient individuals, whereas it is associated with elevated antibody titers in IgAD individuals.

The genetics of innate immunity sensors and human disease

Since their discovery, innate immunity microbial sensors have been increasingly studied and shown to play a critical role in innate responses to microbes in several experimental in vitro, ex vivo, and animal models. However, their role in the human response to infection in natural conditions has just started to be deciphered, by means of clinical studies of primary immunodeficiencies and epidemiological genetic studies. Here, we summarize the major findings concerning the genetic diversity of the various families of microbial sensors in humans, and of other molecules involved in the signaling pathways they trigger. Specifically, we review the genetic associations, revealed by both clinical and epidemiological genetics studies, of microbial sensors from five different families: Toll-like receptors, C-type lectin receptors, NOD-like receptors, RIG-I-like receptors, and cytosolic DNA sensors. In particular, we consider the relationships between variation at the genes encoding these molecules and susceptibility to and the severity of infectious diseases and other clinical conditions associated with immune dysfunction, including autoimmunity, inflammation, allergy, and cancer. Despite the fact that the genetic links between innate immunity sensors and human disorders remain still limited, human genetics studies are increasingly improving our understanding of the genuine functions of microbial sensors and downstream signaling molecules in the natural setting.

Toll-like receptor polymorphisms, inflammatory and infectious diseases, allergies, and cancer

Toll-like receptors (TLRs) are germ-line-encoded innate immune sensors that recognize conserved microbial structures and host alarmins and signal expression of MHC proteins, costimulatory molecules, and inflammatory mediators by macrophages, neutrophils, dendritic cells, and other cell types. These processes activate immediate and early mechanisms of innate host defense, as well as initiate and orchestrate adaptive immune responses. Several single-nucleotide polymorphisms (SNPs) within the TLR genes have been associated with altered susceptibility to infectious, inflammatory, and allergic diseases, and have been found to play a role in tumorigenesis. Critical advances in our understanding of innate immune functions and genome-wide association studies (GWAS) have uncovered complex interactions of genetic polymorphisms within TLRs and environmental factors. However, conclusions obtained in the course of such analyses are restricted by limited power of many studies that is likely to explain controversial findings. Further, linkages to certain ethnic backgrounds, gender, and the presence of multigenic effects further complicate the interpretations of how the TLR SNPs affect immune responses. For many TLRs, the molecular mechanisms by which SNPs impact receptor functions remain unknown. In this review, I have summarized current knowledge about the TLR polymorphisms, their impact on TLR signaling, and associations with various inflammatory, infectious, allergic diseases and cancers, and discussed the directions of future scientific research.

Dendritic Cells in HIV-1 and HCV Infection: Can They Help Win the Battle?

Persistent infections with human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) are a major cause of morbidity and mortality worldwide. As sentinels of our immune system, dendritic cells (DCs) play a central role in initiating and regulating a potent antiviral immune response. Recent advances in our understanding of the role of DCs during HIV-1 and HCV infection have provided crucial insights into the mechanisms employed by these viruses to impair DC functions in order to evade an effective immune response against them. Modulation of the immunological synapse between DC and T-cell, as well as dysregulation of the crosstalk between DCs and natural killer (NK) cells, are emerging as two crucial mechanisms. This review focuses on understanding the interaction of HIV-1 and HCV with DCs not only to understand the immunopathogenesis of chronic HIV-1 and HCV infection, but also to explore the possibilities of DC-based immunotherapeutic approaches against them. Host genetic makeup is known to play major roles in infection outcome and rate of disease progression, as well as response to anti-viral therapy in both HIV-1 and HCV-infected individuals. Therefore, we highlight the genetic variations that can potentially affect DC functions, especially in the setting of chronic viral infection. Altogether, we address if DCs’ potential as critical effectors of antiviral immune response could indeed be utilized to combat chronic infection with HIV-1 and HCV.

Association between a functional polymorphism in Toll-like receptor 3 and chronic hepatitis C in liver transplant recipients

BACKGROUND

Toll-like receptor 3 (TLR3) is implicated in the pathogenesis of viral diseases owing to its ability to recognize viral double-stranded RNA. We hypothesized that single nucleotide polymorphism (SNP) in TLR3 gene that impairs the function of the protein-receptor influences the outcome of hepatitis C virus (HCV) infection after liver transplantation.

METHODS

The clinical characteristics of 611 liver recipients (HCV-infected: n = 153, non-HCV-infected: n = 458) were assessed to investigate the impact of TLR3 L412F SNP on transplant outcomes.

RESULTS

TLR3 L412F is common, and it was significantly more prevalent among the HCV-infected cohort (57.5% vs. 45.2%, P = 0.008). In a multivariate analysis, TLR3 L412F was significantly associated with chronic hepatitis C (odds ratio: 1.73, 95% confidence interval [CI]: 1.13-2.65, P = 0.01). In an analysis that compared HCV-infected patients with wild-type versus TLR3 L412F, a marginally higher rate of allograft failure and mortality was observed in the TLR3 L412F group (44.3% vs. 30.8%, P = 0.09). However, in a multivariate analysis, only donor age was significantly associated with allograft failure and mortality (relative risk: 1.04, 95% CI: 1.007-1.06, P = 0.02).

CONCLUSION

TLR3 L412F is significantly common in HCV-infected liver recipients, and may be associated with worse outcomes. However, larger studies are needed to determine its significant association with allograft failure and mortality after liver transplantation for chronic hepatitis C.

Toll-like receptor 3 polymorphism and its association with hepatitis B virus infection in Saudi Arabian patients

Hepatitis B virus (HBV) is the major causative agent of chronic liver complications including cirrhosis and hepatocellular carcinoma (HCC). Individuals infected with HBV show a wide spectrum of disease manifestations ranging from asymptomatic carriers to HCC. TLR3 is part of the innate immune system that recognizes double-stranded RNA (dsRNA) and provides early immune response to exogenous antigens. The genetic polymorphisms such as single nucleotide polymorphisms (SNPs) in the TLR3 could be considered as factors for the susceptibility to viral pathogens including HBV. Due to lack of knowledge on the role of TLR3 polymorphisms in HBV infection, this study investigated the distribution of nine SNPs in the TLR3 gene and its association with Saudi Arabian patients infected with HBV. A total of 707 patients and 600 uninfected controls were examined for different parameters including the nine SNPs (rs5743311, rs5743312, rs1879026, rs5743313, rs5743314, rs5743315, rs111611328, rs78726532 and a newly identified SNP located at position 184322913 of chr4). The association analysis confirmed that only one SNP, rs1879026 (G/T), showed a significant difference (P = 0.0480; OR = 0.809, 95% CI = 0.655-0.999) in the distribution between HBV carriers and uninfected controls. While, the rest of the SNPs showed no significant association with regards to HBV infection or in the progression to cirrhosis of the liver and HCC. Furthermore, haplotype analysis revealed that one haplotype GCGA (rs1879026, rs5743313, rs5743314, and rs5743315, respectively), was associated significantly with HBV infection in this population. These findings indicate that genetic variations in the TLR3 gene could affect the outcome of HBV infection among Saudis.

Polymorphisms of toll-like receptors and their pathways in viral hepatitis

Toll-like receptors (TLRs) are an important part of the innate immune response to a variety of pathogens including hepatic viral infections. Activation of TLRs stimulates a complex intracellular signalling cascade that results in production of proinflammatory cytokines and interferons important for antiviral responses as well as induction of the adaptive arm of the immune system. There is substantial evidence for an important role for TLRs and TLR-mediated signalling in the pathogenesis and outcomes of hepatitis B and C in particular, but it might also influence responses to other viral hepatitis infections. Several single nucleotide polymorphisms (SNPs) of TLRs, relevant adaptor molecules and cytokines mediated by TLR signalling have been described that alter innate immune responses and have been implicated in a variety of human diseases including viral and other infections. There is now significant evidence that a number of TLR SNPs can affect various clinical outcomes in Caucasian patients with chronic HCV. However, the role of these polymorphisms in acute and other chronic hepatitis infections, including HBV as well as in non-Caucasian populations, has not been elucidated. In addition, results for SNPs downstream of TLR activation, such as in relevant cytokines, are inconsistent and their influence requires further investigation to determine the clinical significance of genetic variations in these mediators.

Toll-like receptor 3 L412F polymorphism may protect against acute graft rejection in adult patients undergoing liver transplantation for hepatitis C-related cirrhosis

Liver transplantation activates the innate immune system by toll-like receptors (TLRs), potentially leading to allograft rejection and graft failure. The aim of this study was to evaluate the possible association of different single nucleotide polymorphisms (SNPs) in several TLR genes with the incidence of acute graft rejection in liver transplant recipients for hepatitis C virus (HCV)-related cirrhosis. This is a single-center study of 100 adult patients who received a first whole only liver graft from deceased donors at our institution between 1988 and 2009 for cirrhosis due to HCV infection. We examined 10 SNPs in the TLR1 (S6021), TLR2 (R753Q), TLR3 (L412F), TLR4 (D299G and T399I), TLR5 (R392X), TLR6 (S249P), TLR7 (Q11L), and TLR9 (-1237T/C and -1486C/T) genes. Genotyping was carried out with the LightSNiP typing assay (TIB-MolBiol, Berlin, Germany) by analyzing the melting curves with the LightCycler 480 system (Roche Applied Science, Mannheim, Germany). Recipient allelic and genotypic distributions for each SNP were compared among patients with and without acute rejection within the first 3 months after transplantation. We found the homozygous mutant TT genotype for TLR3 L412F was associated with a lower rate of acute rejection when compared with the homozygous wild-type genotype [odds ratio (OR) = 0.1, 95% confidence interval (95% CI) = 0.01-0.86; P = .017], and showed a trend toward a lower graft rejection rate when compared with patients carrying one or two C alleles (OR = 0.15, 95% CI = 0.02-1.2, P = .05). No other associations with acute rejection rates were found for any other SNP evaluated. This preliminary study suggests an important role for SNP TLR3 L412F in acute rejection in liver transplant patients for HCV-related cirrhosis. Nevertheless, these findings must be prospectively validated in other cohorts of patients as well as in patients after liver transplantation for other etiologies than HCV.

A functional Toll-like receptor 3 gene (TLR3) may be a risk factor for tick-borne encephalitis virus (TBEV) infection

BACKGROUND

Tick-borne encephalitis virus (TBEV) infections may be asymptomatic or cause severe symptoms in the central nervous system. A mutation in the chemokine receptor 5 gene has been associated with increased risk of TBE but explains only a limited number of cases. Investigations of further risk factors are needed.

METHOD

To investigate the importance of the innate immune response, we analyzed 128 TBE patients, 77 patients with aseptic meningoencephalitis (AME) and 135 healthy controls, for 3 mutations: 2 in the Toll-like receptor 3 (TLR3) gene and 1 in the 2'-5'-oligoadenylate synthetase (OAS1) gene.

RESULTS

Although no association was found between the mutation in the OAS1 gene and TBE, the genotype distribution ofrs3775291, a mutation in TLR3, differed significantly between TBE patients and controls; 61%, 32%, and 7% of the TBE patients were carriers of the wild-type, heterozygous, and mutant genotype of rs3775291, respectively. The corresponding percentages among healthy controls (n = 126) were 52%, 29%, and 19% (P = .02), and among AME patients (n = 75) were 47%, 32%, and 21% (P = .009). Additionally, the wild-type rs3775291 allele was more common among TBE patients than among healthy controls (allele frequency, .768 vs .663; P = .01).

CONCLUSION

A functional TLR3 is a risk factor for TBEV infection.

A comprehensive genotype-phenotype interaction of different Toll-like receptor variations in a renal transplant cohort

To date, the impact of the TLR (Toll-like receptor) system on early and late kidney transplantation outcome, such as ARE (acute rejection episodes) or cardiovascular morbidity and mortality, has still not been elucidated conclusively. Genetically determined alterations in TLR expression exhibit a possibility to evaluate their role in transplantation. In the present study, we sought to determine a comprehensive genotype-phenotype association with early and late allograft outcomes. We studied 11 SNPs (single nucleotide polymorphisms) in TLR2, TLR3, TLR4, TLR5, TLR9 and within a co-molecule CD14 in 265 patients receiving their first kidney transplant and the association of these with the occurrence of DGF (delayed graft function), ARE or MACE (major adverse cardiovascular events). ARE were significantly more frequent in patients carrying the TLR3 TT/CT allele (43.8 compared with 25.8%; P=0.001) as were rates of DGF (21.4 compared with 12.0%; P=0.030). Furthermore, TLR9 was significantly involved in the occurrence of MACE (TLR9 -1237; P=0.030). Interestingly, there was no significant effect of any TLR polymorphism on graft survival or renal function and the incidence of any infection, including CMV (cytomegalovirus) infection. In conclusion, our present study in renal transplant recipients suggests that the TLR system may be involved in both acute rejection and MACE. Modulation of the TLR system may be a promising target in future therapeutic strategies.

Toll-like receptors in innate immunity and infectious diseases

The protective ability of host defense system is largely dependent on germ-line encoded pattern-recognition receptors (PRRs). These PRRs respond to a variety of exogenous pathogens or endogenous danger signals, by recognizing some highly conserved structures such as pathogen-associated molecular patterns (PAMPs) and danger/damage associated molecular patterns (DAMPs). The most studied PRRs are Toll-like receptors (TLRs). Activation of TLRs triggers production of inflammatory cytokines and type I interferons (IFNs) via myeloid differentiation primary response gene 88 (MyD88)-dependent or -independent signaling respectively, thereby modulating innate and adaptive immunity, as well as inflammatory responses. This review introduces the classification, structure, and specific ligands of TLRs, and focuses on their signal pathways and biological activities, as well as clinical relevance. These studies of TLRs in the innate immune system have implications for the prevention and treatment of a variety of infectious diseases, including tuberculosis (TB), microbial keratitis, and hepatitis B and C.

Toll-like receptor 3 in liver diseases

Toll-like receptor 3 (TLR3) is a member of the TLR family that can recognize double-stranded RNA (dsRNA), playing an important role in antiviral immunity. Recent studies have shown that TLR3 is also expressed on parenchymal and nonparenchymal cells in the liver as well as on several types of immune cells. In this review, we summarize the role of TLR3 in liver injury, inflammation, regeneration, and liver fibrosis, and discuss the implication of TLR3 in the pathogenesis of human liver diseases including viral hepatitis and autoimmune liver disease.

Secretion of the human Toll-like receptor 3 ectodomain is affected by single nucleotide polymorphisms and regulated by Unc93b1

The innate immune receptor Toll-like receptor 3 (TLR3) can be present on the surface of the plasma membranes of cells and in endolysosomes. The Unc93b1 protein has been reported to facilitate localization of TLR7 and 9 and is required for TLR3, -7, and -9 signaling. We demonstrate that siRNA knockdown of Unc93b1 reduced the abundance of TLR3 on the cell surface without altering total TLR3 accumulation. In addition, siRNA to Unc93b1 reduced the secretion of the TLR3 ectodomain (T3ECD) into the cell medium. Furthermore, two human single nucleotide polymorphisms that affected herpesvirus and influenza virus encephalopathy as well as a natural isoform generated by alternative splicing were found to be impaired for T3ECD secretion and decreased the abundance of TLR3 on the cell surface. The locations of the SNP P554S and the deletion in the isoform led to the identification of a loop in the TLR3 ectodomain that is required for secretion and a second whose presence decreased secretion. Finally, a truncated protein containing the N-terminal 10 leucine-rich repeats of T3ECD was sufficient for secretion in an Unc93b1-dependent manner.

Endotoxin receptor CD14 gene variants and histological features in chronic HCV infection

AIM: To analyze the correlation between CD14 rs2569190/C-159T single nucleotide polymorphism (SNP) and disease progression in chronic hepatitis C.

METHODS: Liver biopsy specimens from a total of 137 and 349 patients with chronic hepatitis C were separately evaluated with respect to necroinflammatory activity (grading) and architectural changes (staging). In one group, further histological lesions characteristic for hepatitis C, hepatitis C virus subtypes, and biochemical parameters of liver disease were also investigated. Samples of genomic DNA were genotyped for the respective SNP by 5’-nuclease assays using fluorescent dye-labeled allele-specific probes.

RESULTS: Genotype distribution did not deviate from the Hardy-Weinberg equilibrium. In the first group, patients homozygous for the variant allele T were found to be younger than C allele carriers (39.6 ± 12.5 vs 45.7 ± 11.5, P = 0.008). Among the histological lesions studied, portal lymphoid aggregates were more frequently observed among TT homozygotes than among C carriers (21/37 vs 32/100, P = 0.008). The presence of portal lymphoid aggregates was closely correlated with hepatic inflammation (P = 0.003) and with bile duct damage (P < 0.001). The degree of fibrosis, in contrast, was not found to be related to the CD14 gene C-159T polymorphism.

CONCLUSION: The data suggest a possible relationship between CD14 C-159T polymorphism and the formation of portal lymphoid aggregates, but not liver fibrosis progression in chronic hepatitis C.