TLR2 Arg753Gln Polymorphisms Research Articles

TLR Polymorphisms in FMF: Association of TLR-2 (Arg753Gln) and TLR-4 (Asp299Gly, Thre399Ile) Polymorphisms and Myeloid Cell TLR-2 and TLR-4 Expression with the Development of Secondary Amyloidosis in FMF

Amyloidosis is the major complication of familial Mediterranean fever (FMF). Toll-like receptors (TLR) are involved in the activation of an innate immune system TLR-2 and TLR-4 recognize lipoteichoic acid and lipopolysaccharides (LPS), respectively. While TLR-2 Arg753Gln polymorphism upregulates, TLR-4 Asp299Gly and Thre399Ile polymorphisms downregulate inflammation. We investigated the effect of these polymorphisms on the development of amyloidosis in FMF patients. We also investigated myeloid cell TLR-2 and TLR-4 expressions in these patients. We studied 26 FMF patients and 13 FMF patients with amyloidosis. TLR-2 Arg753Gln and TLR-4 Asp299Gly and Thr399Ile polymorphisms were analyzed with the polymerase chain reaction-restriction fragment length polymorphism method. Myeloid cell baseline TLR-2 and TLR-4 and LPS-induced TLR-4 expressions were evaluated. The TLR-2 and TLR-4 polymorphism rate was compared with the results of 100 healthy subjects in our previous study. In addition, 13 healthy controls were enrolled for leukocyte TLR-2 and TLR-4 expressions. Serum amyloid A (SAA) levels were measured in these 13 control cases and in FMF patients during attack-free periods. The frequency of TLR-2 Arg753Gln, TLR-4 Asp299Gly, and Thr399Ile polymorphisms in healthy controls in our previous study were 1%, 3%, and 2%, respectively. The frequency of these polymorphisms were not different in FMF patients (with or without amyloidosis) compared to the control group. Likewise, myeloid cell TLR-2 and TLR-4 expressions were not different among the controls and FMF patients. However, LPS-induced TLR-4 expression in granulocytes was more prominent in FMF patients. There was no correlation between TLR-2 and TLR-4 expressions and SAA levels. Neither myeloid cell TLR-2 and TLR-4 expressions nor TLR-2 Arg753Gln, TLR-4 Asp299Gly, and Thr399Ile polymorphisms seem to affect the development of secondary amyloidosis in FMF patients in our study population.

Identification of polymorphisms in the Toll-like receptor gene and the association with allergic rhinitis

The TLRs gene encodes the principal innate immunity receptor in humans. The TLR2 Arg753Gln and Arg677Trp polymorphisms have been associated with a reduced response of monocytes and cell lines to challenge with mycobacteria. The TLR4 Asp299Gly and Thr399Ile polymorphisms have been associated with a reduction in the inflammatory responses to lipopolysaccharide in humans. It has been suggested that TLR2 and TLR4 polymorphisms may be associated with allergic responses; thus, we hypothesized that TLR2 and TLR4 polymorphisms may modify the relative risk for development of allergic rhinitis. The Taqman assay and high-resolution melt (HRM) were used for genotyping. We analyzed two single nucleotide polymorphisms (SNPs; 597T>C and 1350T>C) in the TLR2 gene and 1 SNP (4216G>C) in the TLR4 gene. We compared the genotype of these SNPs in patients with allergic rhinitis and controls without allergic rhinitis. We also estimated the haplotype frequencies between the two groups. The genotype and allele frequencies of the 597T>C and 1350T>C SNPs in the TLR2 gene were not significantly different between the patients with allergic rhinitis and controls (P > 0.05). The genotype and allele frequencies of 4216G>C in the TLR4 gene were not significantly different between the patients with allergic rhinitis and controls (P > 0.05). Haplotype analysis of the following two different (597)-(1350) major haplotypes (frequency >0.05) were present in the TLR2 gene: T-C and C-C. The C-C haplotype was positively associated with allergic rhinitis (P = 0.048). Our study suggests that the TLR2 gene polymorphisms might be susceptible to the development of allergic rhinitis. Further functional studies of TLR2 genetics in light of the associations with allergic rhinitis inflammation would help clarify the role of TLR2 genetics in clinical evaluations.

TLR-2 Arg753Gln, TLR-4 Asp299Gly, and TLR-4 Thr399Ile polymorphisms in Henoch Schonlein purpura with and without renal involvement

Infections may trigger or aggravate glomerulonephritidis and renal vasculitis like Henoch Schonlein purpura (HSP). HSP is seen more frequently in patients with familial Mediterranean fever in which TLR-2 Arg753Gln polymorphism frequency is increased. Although renal involvement is the most important factor affecting the prognosis in HSP, it is not known which patients will have renal disease or why some patients have severe renal involvement while some others have mild renal disease. We investigated the role of TLR-2 and TLR-4 polymorphisms on the incidence and severity of renal involvement in HSP patients. We studied HSP patients with and without nephritis (n = 15 for each group) and healthy controls (n = 100). TLR-2 Arg753Gln and TLR-4 Asp299Gly/Thr399Ile polymorphisms were analyzed with polymerase chain reaction-restriction fragment length polymorphism method. The frequency of TLR-2 Arg753Gln, TLR-4 Asp299Gly, and Thr399Ile polymorphisms in healthy controls were 1, 3, and 2%, respectively. The frequencies of these polymorphisms were not different in HSP patients with or without nephritis compared to healthy controls. TLR-2 Arg753Gln, TLR-4 Asp299Gly, and Thr399Ile polymorphisms are not increased in HSP or HSP nephritis patients.

Association Between Toll-Like Receptor Polymorphisms and the Outcome of Liver Transplantation for Chronic Hepatitis C Virus

Experimental models suggest that immune cells recognize hepatitis C virus (HCV) through toll-like receptor (TLR)-2 and TLR4. We assessed the association between the single nucleotide polymorphism in genes that encode for these receptors and the outcome of liver transplantation for chronic HCV. A historical cohort of 92 liver transplant patients with chronic HCV were screened for TLR2 Arg753Gln and TLR4 Asp299Gly and Thr399Ile polymorphisms. The results were correlated with the predefined composite primary outcome of cirrhosis, retransplantation, and death. Statistical analysis was performed using Kaplan-Meier estimation and Cox proportional hazard model. The mean patient age was 49+/-9 years. Sixty percent were male and 84% were white. Twelve (13%) patients had TLR2 Arg753Gln and 32 (35%) had TLR4 Asp299Gly and/or Thr399Ile polymorphism. During the mean follow-up period of 32 months after liver transplantation, the composite primary outcome occurred in 19 (24%) of 80 patients without TLR2 polymorphism, one (14%) of seven patients with heterozygous TLR2 polymorphism, and in all five (100%) patients with homozygous TLR2 polymorphism (P=0.0007). Time-to-event analysis showed a significant association between homozygous TLR2 polymorphism and the primary outcome (P<0.0001). After adjusting for donor age and azathioprine use, homozygous TLR2 mutation (RR 5.20 [1.65-13.9]; P=0.007) remained associated with the primary outcome. TLR4 polymorphisms were not associated with primary outcome. Homozygous TLR2 Arg753Gln polymorphism is associated with allograft failure and mortality after liver transplantation for chronic HCV. The potential clinical relevance of this observation should encourage studies to assess its biologic mechanism.

Toll-Like Receptor-2 Arg753Gln Polymorphism and Herpes Virus Infections in Transplantation

Toll-like receptors (TLR) mediate a phylogenetically primitive, nonclonal mechanism of pathogen recognition based on binding to structurally conserved pathogen-associated molecular patterns (1). Stimulation of TLR by its ligand results in the secretion of cytokines that mediate the innate immune control of infections while pathogen-directed adaptive immunity is established (1). Functional single nucleotide polymorphisms in TLRs are therefore hypothesized to influence the pathogenesis of infectious diseases (2). We conducted this hypothesis- generating study to determine the clinical relevance of TLR2 Arg753Gln polymorphism in transplant recipients. This particular TLR2 polymorphism predisposes to staphylococcal infections in humans (2). Ninety-five patients, consisting of 80 solid organ transplant (predominantly liver recipients [80%]) and 15 allogeneic hematopoietic stem cell transplant recipients, were screened for TLR2 Arg753Gln polymorphism using a LightCycler polymerase chain reaction assay (3). Five of 95 transplant recipients possessed the TLR2 Arg753Gln polymorphism (Table 1). Collectively, all five patients with the TLR2 Arg753Gln polymorphism developed at least one herpes infection during the first five years after transplantation: cytomegalovirus (CMV), n=4, including two CMV disease and two asymptomatic CMV infection; herpes simplex virus (HSV), n=2; Epstein-Barr virus (EBV), n=1; varicella zoster virus (VZV), n=1. Except for one patient with recurrent pneumonia due to presumed bacterial pathogen, there were no significant bacterial infections. By comparison, only two herpes infections (one asymptomatic CMV infection and one CMV disease) occurred in a group of five patients without TLR2 Arg753Gln polymorphism that were selected and matched to the cases based on age, gender, allograft type, CMV serostatus, and length of follow-up.TABLE 1: Clinical characteristics of five patients with toll-like receptor 2 Arg753Gln polymorphismThis study demonstrates that herpes virus infections are common among transplant recipients with TLR2 polymorphism. This clinical observation is supported by experimental data demonstrating the role of TLR2 in herpes virus pathogenesis (4). In experimental models, TLR2 was demonstrated as immune sensor for HSV, CMV, and VZV (5–9). Because cells with TLR2 Arg753Gln polymorphism have impaired response to its ligand (4), it is plausible that this could have predisposed to herpes infections. However, this study also demonstrates that the spectrum of illness due to herpes viruses among patients with TLR2 polymorphism varied from asymptomatic primary infection to recurrent and tissue-invasive reactivation disease. Of particular interest is the clinical course of CMV in patients four and five (Table 1). Characteristically, CMV-naïve recipients of allografts from CMV-seropositive donors are at highest risk of CMV disease. With TLR2 polymorphism, one would expect a defective immune response that leads to uncontrolled viral replication and CMV disease. On the contrary, the patients developed asymptomatic CMV infection, implying that TLR2 polymorphism does not by itself completely impede CMV-specific immunity. Indeed, the patients developed humoral responses within three months after transplantation. Although this study is novel since it is the first to assess the clinical relevance of TLR2 Arg753Gln polymorphism on infections after transplantation, it is limited from drawing substantive conclusions because of the small number of subjects. Nonetheless, the intriguing observations in this hypothesis-generating study should encourage further investigations aimed at assessing the impact of TLR polymorphisms on herpes and other infections after transplantation. Albert J.Eid Robert A. Brown Raymund R. Razonable Division of Infectious Diseases Mayo Clinic College of Medicine Rochester, MN

Toll-like receptor 2 Arg753Gln gene polymorphism in Turkish patients with Behcet's disease

Having considered the impact of the function of TLR2 in the recognition of several microorganisms that are thought to have an association with Behçet's disease (BD), we aimed to determine a possible association between the TLR2 Arg753Gln polymorphism and susceptibility to BD. We genotyped 83 patients with BD, 95 ethnically matched healthy controls, 12 patients with recurrent aphthous stomatitis (RAS) and 21 patients with rheumatoid arthritis (RA) by restriction fragment length polymorphism after PCR amplification of the genomic region encompassing the polymorphic site. Comparison of the TLR2 Arg753Gln A allele and A/G genotype frequencies did not show a significant difference between patients with BD and healthy controls (1.2% vs. 0.6%, and 2.1% vs. 1.1%, respectively). None of the patients from the RAS and RA groups had the A allele or A/G genotype. Our results indicate that the TLR2 Arg753Gln polymorphism does not play a role in the aetiopathogenesis of BD.

Polymorphisms of toll-like receptor 2 and 4 genes in rheumatoid arthritis and systemic lupus erythematosus.

Human toll-like receptors (TLRs) participate in the innate response and signal the activation of adaptive immunity. Therefore, these TLRs may be important in autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). We investigated, by using a polymerase chain reaction restriction-fragment length polymorphism method, the possible association between the polymorphisms of TLR2 (Arg677Trp and Arg753Gln) and TLR4 (Asp299Gly and Thr399Ile) genes with the susceptibility or severity of RA and SLE. Our study population consisted of 122 patients with SLE, 224 patients with RA, and a control group of 199 healthy individuals. The TLR2 polymorphisms were very rare in our population; no individual carrying the TLR2-Arg677Trp polymorphism was observed, whereas the TLR2-Arg753Gln polymorphism was present in only 1% of the total population. We found no statistically significant differences in the TLR4-Asp299Gly and the TLR4-Thr399Ile genotype or allele distribution between SLE patients, RA patients, and control individuals. Similarly, no association was found with any of the demographic and clinical parameters tested either in RA or in SLE patients. In conclusion, a case-control study was used to analyze, for the first time, the influence of TLR2 and TLR4 gene polymorphism on the predisposition and clinical characteristics of SLE and RA but provided no evidence for association of TLR2 or TLR4 gene polymorphism with either disease in the population under study.