Association between toll-like receptor polymorphisms and the outcome of liver transplantation for chronic hepatitis C virus

Impact of Toll-Like Receptor 2 and 9 Gene Polymorphisms on COVID-19: Susceptibility, Severity, and Thrombosis

Background

Toll-like receptors (TLRs) play an important role in activation of innate and adaptive immune responses.

Aim

We aimed to detect the association between TLR2 rs5743708 G>A and TLR9 rs5743836 C>T variants and COVID-19 disease susceptibility, severity, and thrombosis by using neutrophil extracellular traps (NETs).

Subjects and Methods

We included 100 adult COVID-19 patients as well as 100 age- and gender-matched normal controls. Participants were genotyped for TLR2 rs5743708 and TLR9 rs5743836. Citrullinated Histone (H3) was detected as an indicator of NETs.

Results

The mutant (G/A and C/C) genotypes and (A and C) alleles of TLR2 rs5743708 and TLR9 rs5743836, respectively, have been significantly related to a higher risk of COVID-19 infection, representing a significant risk factor for the severity of COVID-19. There was no significant association between the two variants and citrullinated histone (H3).

Conclusion

TLR2 rs5743708 and TLR9 rs5743836 variants have been significantly related to a higher risk and severity of COVID-19 infection but had no effect on thrombus formation.

Arg753Gln Polymorphisms in the Toll-Like Receptor 2 Gene are Associated with Cytomegalovirus Infection in Egyptian Bone Marrow Recipients

BACKGROUND

Previous studies have shown that cytomegalovirus (CMV) induced innate immune response via activation of Toll-like receptor 2 (TLR2). The association between CMV among specific single-nucleotide polymorphisms (SNPs) in the TLR2 gene was also investigated.

OBJECTIVE

This study investigated the relationship between specific SNPs in the TLR2 gene (G>A), TLR2-Arg753Gln (rs5743708), and CMV replication after bone marrow transplantation.

METHODS

The TLR2-Arg753Gln SNP was genotyped in 181 patients after bone marrow transplantation: 83 and 98 patients with and without CMV infection, respectively. CMV load was determined in serially collected blood samples using real-time PCR. Genotyping was performed using specific sequence primer PCR (SSP-PCR), and the results were confirmed by restriction fragment length polymorphism (RFLP) analysis of the PCR-amplified fragments for GG (wild type), GA and AA identification.

RESULTS

Roughly, 85% of the patients screened for the presence of the TLR2-Arg753Gln were GG homozygous, and 15% were GA heterozygous; no patients were homozygous for the mutant allele (A). The GA heterozygous allele was more frequent in the CMV-infected group after bone marrow transplantation.

CONCLUSION

To our knowledge, this is a novel observation that supports the notion that the functional missense mutation (TLR2-Arg753Gln polymorphism) is possibly associated with CMV replication after bone marrow transplantation. This suggests a role for TLR2 in the innate immune response of human CMV infection in Egyptian bone marrow recipients.

Role of Innate Immunity in Pediatric Post-transplant Idiopathic Liver Fibrosis

Pediatric post-transplant idiopathic liver fibrosis is an unexplained graft fibrosis that occurs in symptom-free children without acute rejection and surgical complications. Despite a lack of consensus on the subject, the development of pediatric post-transplant idiopathic liver fibrosis is believed to be the result of multiple potential factors, including ischemia-reperfusion injury, allogeneic acute and chronic rejection, viral hepatitis recurrence, opportunistic infection, and drug-induced liver damage. Among them, there is growing evidence that innate immunity may also have a unique role in this progression. This study reviews the features of pediatric post-transplant idiopathic liver fibrosis and discusses current studies illustrating the potential mechanisms of liver allograft tolerance induced by intrahepatic innate immunity, the role of components including Toll-like receptors (TLRs), interferons (IFN), dendritic cells (DC), natural killer cells (NK cells), NKT cells, neutrophils, and Kupffer cells, as well as their possibly relevant role in the development of pediatric post-transplant idiopathic liver fibrosis.

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.

Association of Toll-like receptor 4 polymorphism with hepatitis E virus-infected Indian patients

Hepatitis E infection caused by hepatitis E virus (HEV), a major public health concern in developing countries, is responsible for sporadic and epidemic acute viral hepatitis in adults. Pathogenesis of hepatitis E infection is poorly understood. Toll-like receptors (TLRs) are the key players of innate immunity recognize pathogen-associated molecular patterns (PAMPs). Previously, we found higher TLR4 expression (at protein and gene level) with impaired cytokine response upon stimulus of PBMCs with LPS in HEV-infected patients. In view of the earlier observations of the association of polymorphisms in TLR4 genes (A299G, C399T) with liver diseases, we investigated TLR4 polymorphisms in HEV-infected patients. We observed the significant association of TLR4-399CC and CT alleles with hepatitis E (both subclinical and acute patients). Carrier frequency of TLR4-399 CT was lower in patients' categories in comparison with the controls. Higher frequency of allele TLR4-399C significantly correlated with disease progression. Acute hepatitis E patients showed the higher frequency of CG and TA haplotypes, while the rare haplotype (TG) was more frequent in controls. The other single nucleotide polymorphism (SNP) at TLR4-299 (A>G) did not show any difference. We report here for the first time the association of TLR4 polymorphism with hepatitis E and suggest that TLR 4 hyporesponsiveness during HEV infection might be related to its polymorphism.

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

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

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

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

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

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An association of various TLR SNPs with different inflammatory diseases

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

Rapidity of fibrosis progression in liver transplant recipients with recurrent hepatitis C is influenced by toll-like receptor 3 polymorphism

Liver transplantation activates the innate immune system through toll-like receptors (TLRs), potentially leading to allograft rejection and graft failure. We evaluated the association of single-nucleotide polymorphisms in TLR genes with the severity of hepatitis C virus recurrence after liver transplantation (LT). This is a two-center study of 176 adult patients who received a first LT from deceased donors for hepatitis C virus (HCV) cirrhosis. Eleven polymorphisms were evaluated by real-time polymerase chain reaction and melting curves analyses: TLR1 (Asp248Ser and Ser602Ile), TLR2 (Arg753Gln), TLR3 (Leu412Phe), TLR4 (Asp299Gly), TLR5 (Arg392Stop), TLR6 (Ser249Pro), TLR7 (Gln11Leu), TLR8 (Met1Val), and TLR9 (-1237T/C and -1486C/T). The CC genotype of TLR3 Leu412Phe in liver recipients was associated with severe recurrence (odds ratio (OR) = 2.01, 95% confidence interval (95% CI) = 1.02-3.93, p = 0.04). We also analyzed this polymorphism in 72 of their donors but no association was found with severity of HCV recurrence (p = 0.89). Multivariate analysis showed donor age older than 40 yr (OR=2.93; 95% CI = 1.49-5.8, p = 0.002) and the TLR3 Leu412Phe CC genotype (OR=2.02, 95%CI=1.01-4.05, p = 0.046) were independently associated with severe HCV recurrence. Our results show that the TLR3 Leu412Phe CC genotype is independently associated with severity of hepatitis C recurrence after LT.

Serum aspartate aminotransferase levels and previous histopathological findings enable reduction of protocol liver biopsies after liver transplantation for hepatitis C

BACKGROUND

Hepatitis C virus (HCV) infection remains the leading indication for liver transplantation (LT) worldwide. Recurrent hepatitis C following LT is universal, and significant fibrosis (SF, Metavir fibrosis stage ≥2) apparent on protocol biopsy typically prompts antiviral therapy.

OBJECTIVE

To determine the optimal timing of protocol liver biopsies in this setting.

METHODS

A total of 151 patients who underwent LT related to HCV infection between July 2004 and December 2009 were analyzed retrospectively. Data regarding protocol liver biopsies at six, 12 and 24 months post-LT, conventional laboratory parameters and demographic information were obtained.

RESULTS

The 151 patients included in the present study had significantly lower serum aspartate aminotransferase (AST) levels than the four patients who progressed to receive antiviral treatment for SF before six months post-LT (P<0.001). AST level, but not alanine aminotransferase level, histological activity or fibrosis stage at the six-month biopsy was independently associated with the progression to SF at 12 months (P<0.05). However, AST level, histological activity and fibrosis stage at the 12-month biopsy emerged as independent parameters associated with progression to SF at 24 months (P<0.05).

CONCLUSION

The protocol liver biopsy at six months could be eliminated, especially in patients who consistently exhibit low AST levels. Histological activity, the presence or absence of fibrosis, and AST values at the 12-month biopsy may lead to the decision to defer the protocol biopsy at 24 months or result in earlier introduction of antiviral therapy.

Infections after orthotopic liver transplantation

Opportunistic infections are a leading cause of morbidity and mortality after orthotopic liver transplantation. Systemic immunosuppression renders the liver recipient susceptible to de novo infection with bacteria, viruses and fungi post-transplantation as well to reactivation of pre-existing, latent disease. Pathogens are also transmissible via the donor organ. The time from transplantation and degree of immunosuppression may guide the differential diagnosis of potential infectious agents. However, typical systemic signs and symptoms of infection are often absent or blunted after transplant and a high index of suspicion is needed. Invasive procedures are often required to procure tissue for culture and guide antimicrobial therapy. Antimicrobial prophylaxis reduces the incidence of opportunistic infections and is routinely employed in the care of patients after liver transplant. In this review, we survey common bacterial, fungal, and viral infections after orthotopic liver transplantation and highlight recent developments in their diagnosis and management.

Polymorphisms of Toll-like receptors 2 and 4 in chronically infected hepatitis C patients from north-east Croatia

Chronic infection with hepatitis C virus (HCV) is caused by an inadequate immune response. Experimental data suggest that the impaired activation of Toll-like receptors (TLRs) 2 and 4 contributes to chronic infection. We assessed the distribution of three single-nucleotide polymorphisms (SNPs) in the TLR2 (Arg753Gln) and TLR4 (Asp299Gly/Thr399Ile) genes in individuals from north-east Croatia and their effect on the outcome of antiviral therapy. The study consisted of 60 chronically infected patients and 40 healthy subjects. TLR polymorphisms were determined by the PCR-based melting curve analysis. HCV genotyping was performed using the Linear Array Hepatitis C Virus Genotyping Test. Thirty-three patients were treated with standard interferon and ribavirin therapy, and their viral load was evaluated at weeks 28 and 53 after the beginning of therapy. The majority of chronic infections were caused by genotype 1 (77%), followed by genotypes 3 (15%) and 4 (7%). Patients with genotype 1 had higher viral loads than patients infected with other genotypes (P = 0.0428). Healthy individuals and patients with chronic infection had similar frequencies of TLR2-Arg753Gln and TLR4-Asp299Gly/Thr399Ile SNPs. Heterozygous and homozygous TLR4-Asp299Gly/Thr399Ile polymorphisms correlated with higher viral loads and delayed responses to antiviral therapy. We have provided the first evidence that TLR4 polymorphisms influence the success of antiviral therapy in our region. This suggests that therapeutic strategies should be adjusted not only according to HCV genotype but also to individual TLR polymorphism(s).

Relationship between toll-like receptor 2 Arg677Trp and Arg753Gln and toll-like receptor 4 Asp299Gly polymorphisms and cytomegalovirus infection

OBJECTIVES

The association among specific single-nucleotide polymorphisms (SNPs) in TLR2 (Arg677Trp, Arg753Gln) and TLR4 (Asp299Gln) and human cytomegalovirus (CMV) infection was studied in infants and adults.

METHODS

The TLR2 and TLR4 polymorphisms were genotyped in 151 patients with CMV infections and in 78 unrelated healthy individuals. Genotyping was performed by restriction fragment length polymorphism (RFLP) analysis of PCR-amplified fragments. The viral load was measured by quantitative real-time PCR.

RESULTS

Almost all of the patients with CMV infections were wild-type homozygotes without TLR2 and TLR4 polymorphisms. No significant differences in TLR2 and TLR4 polymorphisms were observed between infants with or without CMV infection. Compared with adults with CMV infections, heterozygosity for the TLR2 Arg677Trp and TLR4 Asp299Gly SNPs was detected more frequently in healthy individuals (p<0.05). Logistic regression analysis showed that the wild-type TLR2 genotype was associated with an increased risk of CMV infection and that heterozygosity for TLR2 and TLR4 SNPs diminished the risk of CMV infection in adult patients. An association between CMV load and the TLR4 SNP was found.

CONCLUSION

Our results suggest that the wild-type TLR2 genotype may be a risk factor for CMV replication in adult patients.

Functional polymorphisms of TLR8 are associated with hepatitis C virus infection

Chronic hepatitis C virus (HCV) infection is a worldwide threat to public health. Toll-like receptor 8 (TLR8) is critical for eliminating RNA viruses, and variation within the TLR8 gene may alter the function of TLR8 in response to HCV infection. Our previous study demonstrated that the TLR8-129G>C (rs3764879) and TLR8+1G>A (rs3764880) variants were in complete linkage disequilibrium, and that the frequency of TLR8-129C/+1A was significantly higher in male patients with HCV infection compared with the healthy controls. In the present study, we found that the promoter activity of TLR8-129G was higher than that of TLR8-129C in THP-1 cells. Moreover, TLR8-129G mRNA stability and competitive DNA-binding ability were significantly lower than that of TLR8-129C. To investigate the functional effects of TLR8 polymorphisms, we compared the nuclear factor-κB (NF-κB)-driven luciferase activity in HEK293 cells transfected with the TLR8 variants. TLR8+1A plasmids induced less NF-κB signalling than did those transfected with TLR8+1G after 20 μm CL075 (P = 0.011) stimulation. We also analysed the mRNA expression and cytokine production in whole blood and monocytes from people of various genotypes stimulated ex vivo by the interferon-γ and TLR7/8 agonist CL075, R848. TLR8 expression in CD14⁺ cells derived from volunteers with TLR8-129G/+1G was significantly higher than that derived from TLR8-129C/+1A, and interleukin-12p40 production was higher in volunteers with TLR8-129G/+1G after stimulation. The data indicate that variations in TLR8 genes may modulate immune responses during HCV infection.

Role of toll-like receptors in liver transplantation

Toll-like receptors (TLRs) are pathogen recognition receptors that orchestrate the innate immune response and the subsequent adaptive immune response. TLRs can be triggered by exogenous ligands expressed by invading pathogens or by the release of endogenous ligands, such as that occurring through cellular injury during the transplantation process. They are now recognized to play an important role in many facets of transplantation biology, including rejection and tolerance, ischemia/reperfusion injury (IRI), and infections after transplantation. The role of TLRs in liver transplantation is unique with respect to other organ transplants because the portal circulation is a continuous source of TLR2 and TLR4 ligands, and this influences TLR signaling pathways, which have a central role in transplantation immunity. This review provides a critical update on recent data outlining the important role of TLRs in liver transplantation, and there is a particular focus on emerging advances in our understanding of rejection and tolerance, IRI, and infections after transplantation and on the ways in which these events may influence the recurrence of diseases such as hepatitis C infection after liver transplantation.

A non-interventional study of the genetic polymorphisms of NOD2 associated with increased mortality in non-alcoholic liver transplant patients

Background

Infections after liver transplantation are the main cause of death in the first year. Recent reports indicate that NOD2 gene mutations increase the risk for inflammatory bowl disease and the severity of graft-versus-host disease in bone marrow transplant patients. Data on polymorphisms in liver transplant patients are sparse. We analyzed 13 single-nucleotide polymorphisms (SNPs) of 13 different gene variants including the SNPs of NOD2 genes from liver recipients. The aim of the study was to evaluate the impact of the SNPs on dialysis-dependent kidney failure, the incidence of infections and patient survival.

Methods

During a period of 20-months, 231 patients were recruited in this non-interventional, prospective study. Thirteen different SNPs and their impact on the patients’ survival, infection rate, and use of dialysis were assessed.

Results

NOD 2 wildtype genes were protective with respect to the survival of non-alcoholic, cirrhotic transplant patients (3 year survival: 66.8% wildtype vs. 42.6% gene mutation, p = 0.026). This effect was not observed in alcoholic transplant recipients.

The incidence of dialysis-dependent kidney failure and infection in the liver transplant patients was not influenced by NOD 2 gene polymorphisms. No effect was noted in the remaining 12 SNPs.

Patients with early allograft dysfunction experienced significantly more infections, required dialysis and had significantly worse survival.

In contrast, the donor-risk-index had no impact on the infection rate, use of dialysis or survival.

Conclusion

NOD2 gene variants seem to play a key role in non-alcoholic, liver transplant recipients. However these data should be validated in a larger cohort.

Digital image analysis of collagen assessment of progression of fibrosis in recurrent HCV after liver transplantation

BACKGROUND & AIMS

Histological assessment of fibrosis progression is currently performed by staging systems which are not continuous quantitative measurements. We aimed at assessing a quantitative measurement of fibrosis collagen proportionate area (CPA), to evaluate fibrosis progression and compare it to Ishak stage progression.

METHODS

We studied a consecutive cohort of 155 patients with recurrent HCV hepatitis after liver transplantation (LT), who had liver biopsies at one year and were subsequently evaluated for progression of fibrosis using CPA and Ishak staging, and correlated with clinical decompensation. The upper quartile of distribution of fibrosis rates (difference in CPA or Ishak stage between paired biopsies) defined fast fibrosers.

RESULTS

Patients had 610 biopsies and a median follow-up of 116 (18-252) months. Decompensation occurred in 29 (18%) patients. Median Ishak stage progression rate was 0.42 units/year: (24 (15%) fast fibrosers). Median CPA fibrosis progression rate was 0.71%/year (36 (23%) fast fibrosers). Clinical decompensation was independently associated by Cox regression only with CPA (p=0.007), with AUROCs of 0.81 (95% CI 0.71-0.91) compared to 0.68 (95% CI 0.56-0.81) for Ishak stage. Fast fibrosis defined by CPA progression was independently associated with histological de novo hepatitis (OR: 3.77), older donor age (OR: 1.03) and non-use/discontinuation of azathioprine before 1 year post-LT (OR: 3.85), whereas when defined by Ishak progression, fast fibrosers was only associated with histological de novo hepatitis.

CONCLUSIONS

CPA fibrosis progression rate is a better predictor of clinical outcome than progression by Ishak stage. Histological de novo hepatitis, older donor age and non-use/discontinuation of azathioprine are associated with rapid fibrosis progression in recurrent HCV chronic hepatitis after liver transplantation.

Toll-like receptors in hepatitis C infection: implications for pathogenesis and treatment

Hepatitis C virus (HCV) infection is a significant global health problem, affecting over 150 million people worldwide. While the critical role of the adaptive immune system in HCV infection is well-established, the importance of the innate immune system in HCV infection has only been recognized in more recent years. Toll-like receptors form the cornerstone of the innate immune response, and there is considerable evidence for their crucial role in hepatitis C infection. This review outlines recent advances made in our understanding of the role of Toll-like receptor function in HCV infection, exploring how HCV manipulates host immunity to evade immune clearance and establish persistent infection despite leading to inflammatory hepatic damage.

The role of natural killer cells in hepatitis C infection

HCV infection is an exponentially growing health burden worldwide, with an estimated 170 million people infected. Although therapies for HCV are continually improving, there remain a considerable proportion of patients who do not achieve viral eradication and develop liver disease. Natural killer (NK) cells are crucial for T-cell activation and are one of the first-line sentinel cell responders to viral infection. A recent explosion in studies exploring the role of NK cells in HCV infection has yielded important mechanistic information and intriguing potential therapeutic options for HCV infection. This review provides a general overview of normal NK cell function and outlines some of the important mechanisms characterizing the immune interplay between NK cells and HCV infection.

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.

Donor polymorphisms of toll-like receptor 4 associated with graft failure in liver transplant recipients

There have been many reports showing significant associations between recipient genetic variants and allograft outcomes, including acute rejection and graft failure, but less is known about the contribution of the donor genotype. We analyzed 37 single-nucleotide polymorphisms (SNPs) within the toll-like receptor 4 (TLR4) gene from deceased donor liver allografts transplanted into 738 recipients to determine their effects on liver graft failure (LGF). Two SNPs exhibited a significant association with LGF after adjustments for donor race and recipient race and corrections for multiple test comparisons: rs11536865 [hazard ratio (HR) = 2.5, P = 0.0003] and rs5030717 (HR = 1.67, P = 0.0008). An additional SNP, rs913930, exhibited a significant association in Caucasian donors (HR = 1.62, P = 0.0006), and 2 SNPs exhibited a suggestive association in African American donors: rs11536865 (HR = 2.45, P = 0.002) and rs5030717 (HR = 2.32, P = 0.002). Additionally, the liver donor risk index (HR = 2.56, 95% confidence interval = 1.54-4.26, P = 0.0003) and the recipient hepatitis C virus (HCV) status (HR = 1.53, 95% confidence interval = 1.04-2.24, P = 0.032) increased the risk of all-cause LGF in a Cox proportional hazards model adjusted for recipient race. Donor polymorphisms in TLR4 could be important factors in modulating TLR4 activity and, therefore, affect the risk of graft loss. Additionally, there is a suggestion of an interaction between polymorphisms within TLR4 and the HCV status.

Theoretical basis of a beneficial role for vitamin D in viral hepatitis

Abnormal bone metabolism and dysfunction of the calcium-parathyroid hormone-vitamin D axis have been reported in patients with viral hepatitis. Some studies suggested a relationship between vitamin D and viral hepatitis. Genetic studies have provided an opportunity to identify the proteins that link vitamin D to the pathology of viral hepatitis (i.e., the major histocompatibility complex class II molecules, the vitamin D receptor, cytochrome P₄₅₀, the renin-angiotensin system, apolipoprotein E, liver X receptor, toll-like receptor, and the proteins regulated by the Sp1 promoter gene). Vitamin D also exerts its effects on viral hepatitis via non-genomic factors, i.e., matrix metalloproteinase, endothelial vascular growth factor, prostaglandins, cyclooxygenase-2, and oxidative stress. In conclusion, vitamin D could have a beneficial role in viral hepatitis. Calcitriol is best used for viral hepatitis because it is the active form of the vitamin D₃ metabolite.

Polymorphisms of the CD14 genes are associated with susceptibility to alcoholic liver disease in Greek patients

BACKGROUND

The incidence and severity of alcoholic liver disease (ALD) in chronic drinkers has been found to correlate with some environmental factors and especially with the dose of alcohol consumption, but it is obvious that other parameters clearly contribute to individual alcohol susceptibility. Chronic ethanol exposure leads to continuous endotoxin-mediated Toll-like receptor-4 (TLR-4) and CD14 activation and subsequent cytokine release resulting in chronic inflammation with continued hepatocellular damage. Therefore, genetic studies of polymorphism in TLR-4 and CD14 genes seem to be appropriate in determining genetic susceptibility to ALD. Our aim is to evaluate in a series of Greek drinkers, the possible association of polymorphisms in the TLR-4 and CD14 genes with ALD.

METHODS

In 96 patients with ALD polymorphism of TLR-4 and CD14 genes were studied compared with 104 patients with cirrhosis of other etiology, 100 healthy subjects, and 50 patients with a history of alcohol abuse but without liver disease.

RESULTS

No association between ALD and the presence of the Asp299Gly and Thr399Ile polymorphisms in the TLR-4 gene could be documented in our patients. Regarding the CD14 -159 (C/T) genotypes, TT genotype and T allele were found to be overrepresented in alcoholic patients compared with patients with nonalcohol-induced liver disease and healthy controls. On the other side, when compared patients with ALD and patients with alcohol abuse and no liver disease, TT genotype was found to be significantly less frequent. There is no statistically significant association with the presence of the T allele and the severity of ALD, suggesting that CD14 polymorphism does not influence disease severity in advanced stages of the disease.

CONCLUSIONS

In our series in Greek patients with alcohol abuse and alcoholic cirrhosis, a significant negative association with the CD14 endotoxin receptor gene polymorphism (TT genotype) but not with the TLR-4 gene polymorphism was documented.

Immunosuppression and HCV recurrence after liver transplantation

HCV related liver disease is the most common indication for liver transplantation. Recurrence of HCV infection is universal and has a substantial impact on patient and graft survival. Immunosuppression is a major factor responsible for the accelerated recurrence and compressed natural history of recurrent HCV infection. Accumulating experience has provided data to support certain strategies for immunosuppressive regimens. From the available evidence, more severe recurrence results from repeated bolus corticosteroid therapy and anti-lymphocyte antibodies used to treat rejection. Low dose and slow tapering of steroids are better than high dose maintenance and/or rapid tapering. Recent meta-analyses favour steroid-free regimens but these are complicated to interpret as the absence of steroids may simply represent less immunopotency. There is no difference in HCV recurrence between tacrolimus and cyclosporine regimens, but tacrolimus increases graft and patient survival in HCV transplanted patients. There may be a beneficial effect of maintenance azathioprine given for 6 months or longer. There is no conclusive evidence for benefit of mycophenolate and interleukin-2 receptor blockers. Few data are available for mTOR inhibitors. Better evidence is needed to establish the optimal immunosuppressive regimen for HCV recipients and more randomized trials should be performed.

Risk factors for infection after liver transplantation

Infection is a common cause of morbidity and mortality after liver transplantation. Risk factors relate to transplantation factors, donor and recipient factors. Transplant factors include ischaemia-reperfusion damage, amount of intra-operative blood transfusion, level and type of immunosuppression, rejection, and complications, prolonged intensive care stay with dialysis or ventilation, type of biliary drainage, repeat operations, re-transplantation, antibiotics, antiviral regimen, and environment. Donor risk factors include infection, prolonged intensive care stay, quality of the donor liver (e.g. steatosis), and viral status. For the recipient the most important are MELD score >30, malnutrition, renal failure, acute liver failure, presence of infection or colonisation, and immune status for viruses like cytomegalovirus. In recent years it has become clear that genetic polymorphisms in innate immunity, especially the lectin pathway of complement activation and in Toll-like receptors importantly contribute to the infection risk after liver transplantation. Therefore, the risk for infections after liver transplantation is a multifactorial problem and all factors need attention to reduce this risk.

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.

Toll-like receptor 4 polymorphisms and the risk of gram-negative bacterial infections after liver transplantation

BACKGROUND

Toll-like receptor 4 (TLR4) is the main immune molecule that recognizes lipopolysaccharide from gram-negative bacteria. Single-nucleotide polymorphisms (SNPs) in the TLR4 gene that impair lipopolysaccharide recognition may influence gram-negative bacterial infections after liver transplantation.

METHODS

TLR4 D299G and T399I SNPs were assessed in a cohort of 706 liver transplant recipients and were associated with the clinical characteristics and outcome of gram-negative bacterial infections. Cox proportional hazard model was performed to determine covariates associated with outcomes after gram-negative bacterial infections.

RESULTS

Of 706 patients, there were 108 with microbiologically confirmed gram-negative bacterial infections, 135 with clinically suspected but not confirmed infections, and 463 patients without gram-negative bacterial infections. The proportions of TLR4 D299G (5/108 [4.6%] vs. 32/463 [6.9%]; P=0.39) and T399I SNPs (19/108 [17.6%] vs. 68/463 [14.7%]; P=0.45) did not differ between those with or without microbiologically confirmed gram-negative bacterial infections. Female gender (odds ratio 2.30, 95% confidence interval [CI]1.50-3.53; P<0.001) and ulcerative colitis (odds ratio 2.18, 95% CI 1.08-4.38; P=0.03) were associated with gram-negative bacterial infections. Among 108 patients with gram-negative bacterial infections, alcoholic liver disease (relative risk [RR] 4.87, 95% CI 1.54-15.44; P=0.007), initial septic shock (RR 10.19, 95% CI 2.70-38.37; P=0.001), and nosocomially-acquired infection (RR 4.61, 95% CI 1.51-14.14; P=0.007) were significantly associated with 90-day mortality after gram-negative bacterial infections. In contrast, TLR4 D299G and T399I SNPs were not significantly associated with mortality after gram-negative bacterial infections.

CONCLUSION

In this cohort of liver transplant recipients with long-term follow-up, no significant association was observed between TLR4 D299G and T399I SNPs and the risk and outcome of gram-negative bacterial infections.

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.

Biomarkers in solid organ transplantation: establishing personalized transplantation medicine

Technological advances in molecular and in silico research have enabled significant progress towards personalized transplantation medicine. It is now possible to conduct comprehensive biomarker development studies of transplant organ pathologies, correlating genomic, transcriptomic and proteomic information from donor and recipient with clinical and histological phenotypes. Translation of these advances to the clinical setting will allow assessment of an individual patient's risk of allograft damage or accommodation. Transplantation biomarkers are needed for active monitoring of immunosuppression, to reduce patient morbidity, and to improve long-term allograft function and life expectancy. Here, we highlight recent pre- and post-transplantation biomarkers of acute and chronic allograft damage or adaptation, focusing on peripheral blood-based methodologies for non-invasive application. We then critically discuss current findings with respect to their future application in routine clinical transplantation medicine. Complement-system-associated SNPs present potential biomarkers that may be used to indicate the baseline risk for allograft damage prior to transplantation. The detection of antibodies against novel, non-HLA, MICA antigens, and the expression of cytokine genes and proteins and cytotoxicity-related genes have been correlated with allograft damage and are potential post-transplantation biomarkers indicating allograft damage at the molecular level, although these do not have clinical relevance yet. Several multi-gene expression-based biomarker panels have been identified that accurately predicted graft accommodation in liver transplant recipients and may be developed into a predictive biomarker assay.

Explanted liver inflammatory grade predicts fibrosis progression in hepatitis C recurrence

Factors present prior to liver transplantation (LT) that predict fibrosis progression in recurrent hepatitis C infection (HCV) after LT would be important to identify. This study sought to determine if histologic grade of HCV in the explant predicts fibrosis progression in recurrent HCV. The clinical and histologic data of all 159 patients undergoing their first LT for HCV at our center from 1998 to 2001 were retrospectively reviewed with follow-up through June 2008. Twenty-five cases were excluded for: non-HCV-related graft loss <90 days (19), recidivism (4), or unavailable explant or follow-up biopsies (2). A single pathologist scored (Ishak) explants in a blinded fashion. Patients were grouped by explant inflammatory grade ≤ 4 (group1) and >4 (group 2). Prospectively scored liver biopsies (protocol months 1 and 4, annually, and as indicated clinically) were reviewed for development of advanced fibrosis (bridging or cirrhosis). Cox proportional hazard regression was used to analyze the association of explant grade, donor, viral and LT factors with progression to advanced fibrosis. The groups were well-matched for patient, viral, donor, and transplant factors. Five-year advanced fibrosis-free survival in group 1 versus group 2 was 63% versus 28%, P < 0.001. Explant grade >4 was associated with increased HCV-related graft loss at 1 (6% versus 3%) and 5 (36% versus 14%) years post-LT (P = 0.003). On univariate and multivariate Cox regression analysis, predictors of advanced fibrosis were explant grade >4 (hazard ratio [HR] = 3.3, 95% confidence interval [CI] = 1.9-5.6, P < 0.001) donor age >50 (HR = 3.3, 95% CI = 1.9-5.7, P < 0.001) and viral load at LT of >158,730 IU/mL (HR = 1.8, 95% CI = 1.05-3.1, P = 0.03).

CONCLUSION

Explant histologic grade can identify patients requiring more aggressive monitoring and intervention for HCV recurrence post-LT.

Bacterial infections, alloimmunity, and transplantation tolerance

Transplantation of solid organs across histocompatibility barriers in the absence of immunosuppression is invariably followed by acute allograft rejection. Although several immunosuppressive regimens have been developed to prevent allograft rejection, these global immunosuppressive agents effectively inhibit all T cells, leaving the host vulnerable to infections. Thus, a major goal in transplantation immunology is to induce donor-specific tolerance that results in the extended suppression of allograft-specific immune responses, while leaving the remainder of the immune system competent to fight infections and malignancies. Initial successes in identifying approaches that successfully induce transplantation tolerance in experimental models have led to a newer research focus of identifying potential barriers to the induction of such tolerance as well as events that may reverse established allograft tolerance. Both clinical and experimental studies have identified bacterial infections as a possible trigger of allograft rejection. Recently, experimental models of transplantation tolerance have identified that bacterial signals can promote acute allograft rejection either by preventing the induction of transplantation tolerance or by reversing tolerance after it has been stably established. This review summarizes experimental and clinical literature supporting the hypothesis that bacterial infections and innate immunity can qualitatively and quantitatively alter adaptive alloreactivity through effects on innate immune responses.

Relationship between the interleukin-28b gene polymorphism and the histological severity of hepatitis C virus-induced graft inflammation and the response to antiviral therapy after liver transplantation

Up to 30% of liver transplants will develop graft cirrhosis within 5 years after liver transplantation (LT) due to recurrent HCV-infection forwarding accelerated graft damage. Genetic variants of cytokines involved in the immune response may contribute to the degree of graft inflammation, fibrosis progression, and antiviral therapy outcome. The aim of our study was to analyze biochemical and histological inflammation extent based on protocol liver biopsies and to evaluate the role of genetic variants of IL-28b in HCV-related graft disease and antiviral treatment response. 183 patients, who underwent liver transplantation for HCV-induced liver disease, were genotyped for IL-28b (rs8099917, G ≥ T) by TaqMan Genotyping Assay. 56 of 159 patients have been successfully treated with interferon-based antiviral therapy. 605 protocol liver biopsies performed 0.5 to 10 and more than 10 years after transplantation were evaluated according to Desmet and Scheuer classification of inflammation and fibrosis. Prevalence of IL-28b-genotypes was correlated with histological severity of graft damage, levels of aminotransferases, occurrence of acute cellular rejection, pre-treatment viremia, and antiviral therapy outcome. Significant association of IL-28b-genotype distribution was observed to the median grade of inflammation (p < 0.001), mean levels of aminotransferases (ALT: p = 0.001, AST: p = 0.003), median pre-treatment viremia level within 1 year after LT (p = 0.046) and interferon-based antiviral therapy failure (p < 0.001). Among successfully treated patients, G-allele was significantly less frequent, and the genotype GG was not present at all. No differences were observed regarding acute cellular rejection (p = 0.798) and fibrosis stages (p = 0.586). IL-28b polymorphism seems to influence the degree of graft inflammation at biochemical and histological levels. G-allele might serve as a marker for graft inflammation and as a predictor for unfavorable antiviral therapy outcome in HCV-re-infected LT-population.

Functional assessment of Toll-like receptor 2 and its relevance in patients with Staphylococcus aureus infection of joint prosthesis

Staphylococcus aureus induces inflammation in experimental models through Toll-like receptor 2 (TLR2). The clinical relevance of this observation is debated. We evaluated the relationship between TLR2 R753Q single nucleotide polymorphism (SNP) and S aureus infection of joint prosthesis. Human embryonic kidney 293 (HEK293) cells transfected with wild-type and mutant R753Q TLR2 gene were assessed for response to S aureus peptidoglycan. Real-time polymerase chain reaction and gene sequencing of DNA were performed to assess TLR2 R753Q SNP in 76 patients with S aureus prosthetic joint infection (PJI) and 208 noninfected controls. HEK293 cells expressing wild-type TLR2 gene responded robustly to S aureus peptidoglycan, while cells with mutant R753Q TLR2 gene did not. The prevalence of R753Q SNP was high in S aureus PJI patients (heterozygous in 8%, and homozygous in 22%), although not significantly different from controls (12% and 27%, respectively). The TLR2 variant allele was not significantly associated with the risk or survival free of recurrent PJI S aureus. In conclusion, TLR2 R753Q SNP disabled the cellular response to S aureus peptidoglycan in vitro. However, TLR2 R753Q SNP was not significantly associated with the risk or outcome of PJI due to S aureus in human patients.

Polymorphism in 3'-untranslated region of toll-like receptor 4 gene is associated with protection from hepatitis B virus recurrence after liver transplantation

BACKGROUND

Hepatitis B virus (HBV) recurrence is one of the more severe complications following liver transplantation. Toll-like receptors (TLRs) play a key role in human immunity by recognizing various bacteria, viruses, fungi, and parasites. Single nucleotide polymorphisms (SNPs) in the TLRs are thought to have an impact on the susceptibility to some pathogens. This study focused on the association between polymorphisms in the TLRs and HBV recurrence after liver transplantation in Han Chinese patients.

METHODS

A total of 41 tag SNPs in TLRs were detected by the snapshot technique in 125 patients with primary HBV-related diseases receiving liver transplantation in our center from 2004 to 2008.

RESULTS

By comparing the genetic variations and clinical data between the HBV recurrence patients and nonrecurrence patients, we found that the variant genotype of rs11536889 (TLR4) was significantly associated with HBV recurrence after liver transplantation (P = 0.040, odds ratio was 0.390, 95% confidence interval 0.159-0.957).

CONCLUSION

Our findings indicate that polymorphism in 3'-untranslated regions of the TLR4 gene may be related to protection from HBV recurrence after liver transplantation in Han Chinese patients.

Very low frequencies of Toll-like receptor 2 supposed-2029T and 2258A (RS5743708) mutant alleles in southern Brazilian critically ill patients: would it be a lack of worldwide-accepted clinical applications of Toll-like receptor 2 variants?

Toll-like receptor 2 (TLR2) is a recognition receptor for the widest repertoire of pathogen-associated molecular patterns. Two polymorphisms of TLR2 could be linked to reduced nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) activation and to increased risk of infection (supposed-2029C>T and 2258G>A). We investigated the supposed-2029C>T and 2258G>A TLR2 polymorphisms in 422 critically ill patients of European origin from southern Brazil (295 with sepsis and 127 without sepsis) and reviewed 33 studies on these polymorphisms, conducting a quality assessment with a score system. Among our patients we found only one heterozygote (1/422) for the supposed-2029C>T and none for the 2258G>A (0/422) single nucleotide polymorphism (SNP). We were unable to find a clinical application of supposed-2029T and 2258A allele analyses in our southern Brazilian population. Our review detected that current TLR2 SNP assays had very controversial and contradictory results derived from reports with a variety of investigation quality criteria. We suggest that, if analyzed alone, the supposed-2029C>T and 2258G>A TLR2 SNP are not good candidates for genetic markers in studies that search for direct or indirect clinical applications between genotype and phenotype. Future efforts to improve the knowledge and to provide other simultaneous genetic markers might reveal a more effective TLR2 effect on the susceptibility to infectious diseases.

A single nucleotide polymorphism of Toll-like receptor 4 identifies the risk of developing graft failure after liver transplantation

BACKGROUND & AIMS

While studies in animal models have linked Toll-like receptor (TLR) 4 signaling to the pathophysiology of ischemia/reperfusion (IR) injury and liver fibrosis, the relevance of TLR4 activation after human liver transplantation is unknown. The TLR4 single nucleotide polymorphism (SNP) D299G is situated within the extracellular domain and diminishes receptor binding to danger-associated molecular patterns.

METHODS

We studied the influence of TLR4 D299G on IR injury and graft survival in 430 deceased donor LT recipients. Compared with livers expressing wild-type (WT) alleles, livers with a TLR4 loss-of-function allele were significantly more likely to have initial good graft function (IGGF) (OR 2.20, p=0.01). In contrast, there was no effect of recipient TLR4 genotype on the rate of IGGF.

RESULTS

The effect of TLR4 D299G on long-term graft survival was analyzed based on hepatitis C virus (HCV) serostatus. In HCV infected recipients, multivariate Cox regression analysis demonstrated a significant association between the presence of recipient, but not donor TLR4 D299G and long-term graft failure (HR 2.48, CI 1.28-4.81; p=0.007). There was no difference in graft survival between TLR4 mutant and WT recipients among non-HCV infected recipients.

CONCLUSIONS

Collectively, these results demonstrate the differential effects of donor and recipient TLR4 signaling in human liver transplantation. Donor TLR4 contributed to sterile injury following cold preservation and the recipient TLR4 genotype was linked with poor allograft survival among HCV infected recipients.

R753Q single-nucleotide polymorphism impairs toll-like receptor 2 recognition of hepatitis C virus core and nonstructural 3 proteins

BACKGROUND

Hepatitis C virus (HCV) core and nonstructural (NS) 3 proteins induce inflammation and immunity through a toll-like receptor (TLR) 2-dependent pathway. Individuals with the R753Q single-nucleotide polymorphism (SNP) in the TLR2 gene have increased the risk of allograft failure after liver transplantation for chronic hepatitis C.

METHODS

To test the hypothesis that R753Q SNP impairs TLR2 recognition of HCV proteins, a series of in vitro experiments were performed wherein stable clones of wild-type TLR2-deficient human embryonic kidney (HEK) 293 cells and HEK293 cells transfected with wild-type (HEK293-TLR2) or variant TLR2 genes (HEK293-TLR2-R753Q) were stimulated with HCV core and NS3 proteins. Cellular activation was assessed by nuclear factor-kappa B-driven luciferase activity, cytokine secretion, and gene upregulation.

RESULTS

Compared with TLR2-deficient HEK293 cells, HEK293-TLR2 cells had marked nuclear factor-kappa B-driven luciferase activity, had modest to marked upregulation in TLR2 signaling-associated genes, and secreted large quantities of interleukin-8 during exposure to HCV core and NS3 proteins. In contrast, HEK293-TLR2-R753Q cells did not respond to stimulation with HCV and behaved similarly like TLR2-deficient HEK293 cells.

CONCLUSION

R753Q SNP impairs TLR2-mediated immune recognition of HCV core and NS3 proteins. This biologic defect may account for the predisposition of patients to develop allograft failure after liver transplantation for chronic hepatitis C.

Polymorphisms in innate immunity genes associated with development of bronchiolitis obliterans after lung transplantation

BACKGROUND

Activation of the immune system is suggested to prevent transplant tolerance and to promote the development of bronchiolitis obliterans syndrome (BOS). The innate immune system is activated by the interaction of pathogen-associated molecular patterns of microorganisms with Toll-like receptors (TLRs). Activation of innate immunity via TLRs was shown to be a barrier to the induction of transplantation tolerance after lung transplantation. We hypothesized that polymorphisms in 10 genes coding for TLR1 to TLR10 might contribute to an altered immune response and the subsequent development of BOS.

METHODS

DNA was collected from 110 lung transplant recipients. Twenty patients developed BOS. The control group comprised 422 individuals. Sixty-four single-nucleotide polymorphisms (SNPs) in 10 genes coding for TLR1 to TLR10 were genotyped.

RESULTS

The genotype distribution of TLR2 (rs1898830 and rs7656411), TLR4 (rs1927911) and TLR9 (rs352162 and rs187084) was significantly different between BOS(pos) patients and BOS(neg) patients and controls. The BOS(pos) group had significantly more patients with 3 or 4 of these risk alleles compared with the BOS(neg) and control groups.

CONCLUSIONS

Polymorphisms in TLR2, TLR4 and TLR9 that recognize bacterial and viral pathogens are associated with BOS after lung transplantation.

Monitoring the operationally tolerant liver allograft recipient

PURPOSE OF REVIEW

A fundamental goal in transplantation is the establishment of allograft function without ongoing immunosuppression. Robust allograft tolerance has been established in experimental transplantation models, whereas clinical operational tolerance has been described most frequently following human liver transplantation.

RECENT FINDINGS

Clinical assessment of tolerance has been limited to laboratory evaluation of organ function. Additional tools include graft monitoring through biopsy and blood sampling for biomarker analysis. Current biomarkers under assessment in recent years include dendritic cell subsets, regulatory T cells, antidonor antibodies, and gene polymorphisms. Emerging microarray analysis that is being prospectively validated will also be reviewed. A further tool in the characterization of the tolerant patient will be the accurate enrollment of such patients into a multicenter registry that will prospectively follow the natural history of the patient withdrawn from immunosuppression and help facilitate the entry of interested patients to mechanistic and immune monitoring trials. The International Solid Organ Transplant Tolerance Registry (www.transplant-tolerance.org) will be briefly described.

SUMMARY

Effective biomarker characterization of the operationally tolerant liver allograft recipient would allow earlier, well tolerated, prospective drug withdrawal with the goal of extending the potential benefits of drug minimization to an increasing number of patients in a more predictable fashion.

The potential use of Toll-like receptor agonists to restore the dysfunctional immunity induced by hepatitis C virus

Hepatitis C virus (HCV) infection is a major public health concern with approximately 3% of the world's population is infected, posing social, economical and health burden. Less than 20% of the infected individuals clear the virus during the acute infection, while the rest develop chronic infection. The treatment of choice for HCV infection is pegylated interferon-alpha (IFN-alpha) in combination with ribavarin. Despite the cost and side effects of this treatment regimen, many patients fail this therapy and develop persistent HCV infection, leading to cirrhosis and hepatocellular carcinoma. Although the mechanisms underlying the failure to resolve HCV infection are poorly understood, the incapability of patients to develop effective anti-HCV immunity is a potential cause. We hypothesize that the dysfunctional anti-HCV immunity is due to the emergence of immunosuppressive cells coinciding with a decrease in the stimulatory dendritic cells (DCs) and natural killer (NK) cells. We further hypothesize that applying agents that can correct the imbalance between the immunosuppressive cells and stimulatory cells can results in resolution of chronic HCV. In this review article, we will discuss potential approaches, focusing on the use of Toll-like receptor agonists, to block the suppressive effects of the regulatory cells and restore the stimulatory effects of DCs and NK cells.

Outcome of recurrent hepatitis C virus after liver transplantation in a randomized trial of tacrolimus monotherapy versus triple therapy

Less potent immunosuppression is considered to reduce the severity of hepatitis C virus (HCV) recurrence after liver transplantation. An optimal regimen is unknown. We evaluated tacrolimus monotherapy versus triple therapy in a randomized trial of 103 first transplants for HCV cirrhosis. One hundred three patients who underwent transplantation for HCV were randomized to tacrolimus monotherapy (n = 54) or triple therapy with tacrolimus, azathioprine, and steroids (n = 49), which were tapered to zero by 3 to 6 months. Both groups had serial transjugular biopsies with hepatic venous pressure gradient (HVPG) measurement. The time to reach Ishak stage 4 was the predetermined endpoint. All factors documented in the literature as being associated with HCV recurrence and the allocated treatment were evaluated for reaching stage 4 and HVPG >or= 10 mm Hg. No significant preoperative, perioperative, or postoperative differences, including the frequency of biopsies between groups, were found. During a mean follow-up of 53.5 months, 9 monotherapy patients and 6 triple therapy patients died, and 5 monotherapy patients and 4 triple therapy patients underwent retransplantation. Stage 4 fibrosis was reached in 17 monotherapy patients and 10 triple therapy patients (P = 0.04), with slower fibrosis progression in the triple therapy patients (P = 0.048). Allocated therapy and histological acute hepatitis were independently associated with stage 4 fibrosis. HVPG increased to >or=10 mm Hg more rapidly in monotherapy patients versus triple therapy patients (P = 0.038). In conclusion, long-term maintenance immunosuppression with azathioprine and shorter term prednisolone with tacrolimus in HCV cirrhosis recipients resulted in a slower onset of histologically proven severe fibrosis and portal hypertension in comparison with tacrolimus alone, and this was independent of known factors affecting fibrosis.

The heterogeneous allelic repertoire of human toll-like receptor (TLR) genes

Toll-Like Receptors (TLR) are critical elements of the innate arm of the vertebrate immune system. They constitute a multigenic family of receptors which collectively bind a diverse array of – exogeneous as well as endogeneous – ligands. An exponential burst of knowledge has defined their biological role in fight against infections and generation/modulation of auto-immune disorders. Hence, they could at least be conceptually recognized – despite being structurally unrelated – as innate counterparts to Major Histocompatibility Complex (MHC) molecules – equally recognizing antigenic ligands (albeit structurally more homogeneous i.e., peptides), again derived from self and/or non-self sources – preeminent this time in adaptive immunity. Our great disparities in face of infections and/or susceptibility to auto-immune diseases have provoked an intense search for genetic explanations, in part satisfied by the extraordinary MHC allelic repertoire. An equally in-depth and systematic analysis of TLR diversity is lacking despite numerous independent reports of a growing number of SNPs within these loci. The work described here aims at providing a preliminary picture of the allelic repertoire – and not purely SNPs – of all 10 human TLR coding sequences (with exception of TLR3) within a single cohort of up to 100 individuals. It appears from our work that TLR are unequally polymorphic: TLR2 (DNA alleles: 7/protein alleles: 3), 4 (4/3), 7 (6/3), 8 (9/2) and 9 (8/3) being comparatively least diverse whereas TLR1 (11/10), 5 (14/12), 6 (10/8) and 10 (15/10) show a substantial number of alleles. In addition to allelic assignment of a large number of SNPs, 10 new polymorphic positions were hereby identified. Hence this work depicts a first overview of the diversity of almost all human TLR genes, a prelude for large-scale population genetics as well as genetic association studies.

Azathioprine in liver transplantation: a reevaluation of its use and a comparison with mycophenolate mofetil

Calcineurin inhibitors (CNIs) combined with steroids with or without azathioprine (AZA), have been a standard immunosuppression regimen after liver transplantation (LT). Since 2000 many centers have substituted AZA by mycophenolate mofetil (MMF). However, in LT the superiority of MMF over AZA is not clearly demonstrated. Therefore, we questioned the benefit of MMF versus AZA in LT with regard to rejection, renal dysfunction and hepatitis C virus (HCV) recurrence and survival. Using a literature search, relevant randomized controlled trials (RCT) and cohort studies were identified: two RCTs compared MMF to AZA only for acute rejection. Treated rejection was less with MMF in only one RCT (38.5% vs. 47.7%; p = 0.025), with no difference in patient and graft survival. No RCTs compared MMF and AZA in patients with CNI-related chronic renal dysfunction. Among two studies evaluating MMF, with substitution of AZA, one was stopped due to severe rejection. Recurrent HCV was less severe in 5/9 studies with AZA compared with 2/17 using MMF, six of which documented worse recurrence. Published data in LT show little, if any, clinical benefit of MMF versus AZA. RCTs should reevaluate AZA in LT. Evaluation of HCV replication and recurrence will be particularly important as AZA may have advantages over MMF.