Toll-like receptor-1, -2, and -6 genotypes in relation to salivary human beta-defensin-1, -2, -3 and human neutrophilic peptide-1

AIM

To examine whether functional gene polymorphisms of toll-like receptor (TLR)1, TLR2, and TLR6 are related to the salivary concentrations of human beta-defensins (hBDs)-1, -2, -3, and human neutrophilic peptide (HNP)-1.

MATERIALS AND METHODS

Polymorphisms of TLR1 (rs5743618), TLR2 (rs5743708), and TLR6 (rs5743810) were genotyped by PCR-based pyrosequencing from the salivary samples of 230 adults. Salivary hBD-1, -2, -3, and HNP-1 concentrations were measured using enzyme-linked immunosorbent assay. General and periodontal health examinations, including panoramic radiography, were available for all participants.

RESULTS

The genotype frequencies for wild types and variant types were as follows: 66.5% and 33.5% for TLR1, 95.5% and 4.5% for TLR2, and 25.1% and 74.9% for TLR6, respectively. The TLR2 heterozygote variant group exhibited higher salivary hBD-2 concentrations than the TLR2 wild-type group (p = .038). On the contrary, elevated hBD-2 concentrations were detected in the TLR6 wild-type group compared with the TLR6 heterozygote and homozygote variant group (p = .028). The associations between TLR6 genotypes and salivary hBD-2 concentrations remained significant after adjusting them for periodontal status, age, and smoking.

CONCLUSION

hBD-2 concentrations in saliva are related to TLR2 and TLR6 polymorphisms, but only the TLR6 genotype seems to exhibit an independent association with the salivary hBD-2 concentrations.

Risk factors for irreversible airway obstruction after infant bronchiolitis

BACKGROUND

Increasing evidence shows that environmental factors in childhood play a role in development of irreversible airway obstruction. We evaluated early-life and preschool-age risk factors for irreversible airway obstruction in adolescence after bronchiolitis in infancy.

METHODS

This study is a secondary analysis of data collected during prospective long-term follow-up of our post-bronchiolitis cohort. Risk factor data were collected during hospitalisation and on follow-up visits at 5-7 and 10-13 years of ages. Lung function was measured from 103 participants with impulse oscillometry at 5-7 years of age and from 89 participants with flow-volume spirometry at 10-13 years of age.

RESULTS

Asthma diagnosis at <12 months of age showed a significant association with irreversible airway obstruction at 10-13 years of age independently from current asthma. Irreversible airway obstruction was less frequent in children with variant than wild genotype of the Toll-like receptor 4(TLR4) rs4986790, but the significance was lost in logistic regression adjusted for current asthma and weight status. Higher post-bronchodilator respiratory system resistance at 5 Hz and lower baseline and post-bronchodilator reactance at 5 Hz by impulse oscillometry at 5-7 years of age were associated with irreversible airway obstruction at 10-13 years of age.

CONCLUSION

Asthma diagnosis during the first living year and worse lung function at preschool age increased the risk for irreversible airway obstruction at 10-13 years of age after bronchiolitis. TLR4 rs4986790 polymorphism may be protective for development of irreversible airway obstruction after bronchiolitis.

Using Linear Discriminant Analysis to Characterize Novel Single Nucleotide Polymorphisms and Expression Profile Changes in Genes of Three Breeds of Rabbit (Oryctolagus cuniculus)

The objectives of this study were to investigate polymorphisms and changes in expression patterns of the genes FGF5, PGAM2, TLR2 and IL10 in V-line, Baladi Black and Baladi Red rabbits. Blood samples were collected from 180 healthy rabbits (n = 60 for each breed) for DNA extraction and DNA sequencing. At 3 mo of age, 20 randomly selected females from each breed were euthanized for gene expression quantification in muscle and spleen samples. PCR-DNA sequencing revealed single nucleotide polymorphisms (SNPs) among the 3 breeds that provided a monomorphic pattern for 3 of the 4 genes analyzed. Linear discriminant analysis (LDA) was used to classify the SNPs of these genes in the 3 breeds. The overall percentage of correctly classified cases for the model was 75%, with percentages of 100% for FGF5, 63% for IL10, and 100% for TLR2. Breed was a significant predictor for gene classification with estimation (1.00). Expression profiles of the genes were higher in V-line as compared with Baladi Black or Baladi Red. The LDA discriminated the 3 breeds using results of the gene expression profile as predictors for classification. Overall, 73% of the cases were correctly classified by gene expression. The identified SNPs, along with changes in mRNA levels of FGF5, PGAM2, TLR2, and IL10, could provide a biomarker for efficient characterization of rabbit breeds and could thus help develop marker assisted selection for growth and immune traits in rabbits.

Toll-like receptor 10 rs10004195 variation may be protective against Bacillus Calmette-Guérin osteitis after newborn vaccination

AIM

Toll-like receptor 1 (TLR1), TLR2, TLR6 and TLR10 form the TLR2 subfamily. In our previous controlled studies in 132 subjects with osteitis after newborn Bacillus Calmette-Guérin (BCG) vaccination, TLR1, TLR2 and TLR6 variations were associated with the risk of BCG osteitis. Now, we evaluated the role of ten single nucleotide polymorphisms (SNP) of the TLR10 gene in this cohort.

METHODS

Five synonymous TLR10 SNPs (rs10004195, rs10856837, rs10856838, rs1109695 and rs11466652), and five missense TLR10 SNPs (rs11096955, rs11096957, rs11466649, rs11466653 and rs11466658) were determined by polymerase chain reaction (PCR)-based sequencing in 132 former BCG osteitis patients.

RESULTS

TLR10 rs10004195 polymorphism was associated with the risk of BCG osteitis, compared to Finnish population controls. The variant genotype (AT/AA) was present in 13.6% of cases versus 26.2% of controls (p = 0.024). Correspondingly, the minor allele frequency (MAF) was lower (0.075) in cases than in controls (0.152; p = 0.009). There were no significant differences in the genotypes of the other nine studied TLR10 SNPs or in the corresponding MAFs between cases and controls.

CONCLUSION

Among ten studied TLR10 gene polymorphisms, the variation only in the TLR10 rs10004195 was associated with the BCG osteitis risk after newborn BCG vaccination.

Pathogenesis and Host Immune Response in Leprosy

Leprosy is an ancient insidious disease caused by Mycobacterium leprae, where the skin and peripheral nerves undergo chronic granulomatous infections, leading to sensory and motor impairment with characteristic deformities. Susceptibility to leprosy and its disease state are determined by the manifestation of innate immune resistance mediated by cells of monocyte lineage. Due to insufficient innate resistance, granulomatous infection is established, influencing the specific cellular immunity. The clinical presentation of leprosy ranges between two stable polar forms (tuberculoid to lepromatous) and three unstable borderline forms. The tuberculoid form involves Th1 response, characterized by a well demarcated granuloma, infiltrated by CD4⁺ T lymphocytes, containing epitheloid and multinucleated giant cells. In the lepromatous leprosy, there is no characteristic granuloma but only unstructured accumulation of ineffective macrophages containing engulfed pathogens. Th1 response, characterised by IFN-γ and IL-2 production, activates macrophages in order to kill intracellular pathogens. Conversely, a Th2 response, characterized by the production of IL-4, IL-5 and IL-10, helps in antibody production and consequently downregulates the cell-mediated immunity induced by the Th1 response. M. lepare has a long generation time and its inability to grow in culture under laboratory conditions makes its study challenging. The nine-banded armadillo still remains the best clinical and immunological model to study host-pathogen interaction in leprosy. In this chapter, we present cellular morphology and the genomic uniqueness of M. leprae, and how the pathogen shows tropism for Schwann cells, macrophages and dendritic cells.

Toll-like receptor 10 rs4129009 gene polymorphism is associated with post-bronchiolitis lung function in adolescence

AIM

The aim was to evaluate the association of polymorphisms in the Toll-like receptor (TLR) 2 subfamily encoding genes with lung function by spirometry at 10-13 years of age in children who had been hospitalised for bronchiolitis at <6 months of age.

METHODS

In a prospective cohort of 166 former bronchiolitis patients, 138 returned a structured questionnaire and 89 attended a clinical follow-up visit including spirometry before and after bronchodilation at 10-13 years of age. Data on polymorphisms of the TLR1, TLR2, TLR6 and TLR10 genes were available from 81-82 children.

RESULTS

In the TLR10 rs4129009, the wild (AA) genotype was associated with lower FEV1/FVC before (92.4 vs 97.4, P = .002) and after (95.5 vs 98.6, P = .011) bronchodilator administration, compared to those with the variant genotype. When the TLR10 rs4129009 and TLR2 rs5743708 genotypes, and the TLR10 rs4129009 and TLR1 rs5743618 genotypes, respectively, were analysed as combined, both baseline and post-bronchodilator FEV1/FVC were lowest in the subjects with the wild (AA) genotype of the TLR10 rs4129009.

CONCLUSION

In this post-bronchiolitis follow-up, lung function in children with the variant TLR10 rs4129009 genotype with potentially altered TLR10 function was superior to lung function in those with the wild genotype.

Association of MBL2, TLR1, TLR2 and TLR6 Polymorphisms With Production of IFN-γ and IL-12 in BCG Osteitis Survivors R1

BACKGROUND

Interferon-gamma (IFN-γ) is a key cytokine in defense against mycobacteria, including Bacillus Calmette-Guérin (BCG). Mannose-binding lectin (MBL) and toll-like receptors (TLRs) are pattern-recognizing molecules of innate immunity. The aim of the present study was to investigate the relationship between polymorphisms in MBL, TLR1, TLR2 and TLR6 encoding genes and stimulated IFN-γ and interleukin-12 (IL-12) ex vivo production in BCG osteitis survivors.

METHODS

Data on single nucleotide polymorphisms in the MBL2 gene and TLR1, TLR2 and TLR6 genes were available from 132 former BCG osteitis patients, and data on ex vivo IFN-γ and IL-12 production were available from 115 and 118 patients, respectively. The present study is a secondary analysis of these available data. In an earlier study, we were able to characterize low IFN-γ and low IL-12 producers after BCG+IL-12 or BCG+IFN-γ stimulations, respectively.

RESULTS

Three patients had the homozygous variant MBL2 genotype, and one of them was a low IFN-γ producer (both concentration and response <5th percentile). The heterozygous variant MBL2 genotype showed no association with IFN-γ or IL-12 production. The TLR2 variant genotype was present in 14 subjects; 28.6% of them were low IFN-γ producers versus 7.8% of those 103 with the TLR2 wild genotype (P = 0.037). TLR1 or TLR6 polymorphisms had no significant associations with stimulated ex vivo IFN-γ or IL-12 production.

CONCLUSIONS

Preliminary evidence was found that variant genotypes of the MBL2 gene (if homozygous) and variant genotypes of the TLR2 gene (only heterozygotes present) are associated with low IFN-γ production.

Is there any relationship between Toll-like receptor 3 c.1377C/T and -7C/A polymorphisms and susceptibility to Crimean Congo hemorrhagic fever?

Crimean-Congo hemorrhagic fever (CCHF) is an infectious disease that is caused by CCHF virus. A family of transmembrane receptors called as Toll-like receptors (TLRs) selectively acts in recognizing a wide range of microbial components and endogenous molecules released by damaged tissue and have been preserved throughout evolution. TLRs initiate some signaling cascades which activate the innate immune system. Mainly four TLRs act in protection against viral infections; TLR3 is one of them. TLR3 identifies dsRNA. By producing inflammatory cytokines and type I interferons, it generates an antiviral immune response. Proper response to TLR ligands may be impaired by single nucleotide polymorphisms (SNPs) within TLR genes in some indviduals, and this can cause varied susceptibility to infections. In the present work, polymerase chain reaction-based restriction fragment length polymorphism is used to analyze the frequencies of TLR3 (c.1377C/T and -7C/A) polymorphisms in 149 CCHF patients and 171 healthy adults as controls, in Cumhuriyet University, Sivas/Turkey. We also investigated the relation between these polymorphisms and severity or mortality of CCHF disease. This is the first study investigating the TLR3 SNPs in patients with CCHF. In the present study, the frequency of the TLR3 (c.1377C/T and -7A/C) genotypes in fatal and non-fatal cases were comparable, however, the homozygous mutant (TT) genotype frequency of TLR3 c.1377C/T in CCHF patients was significantly higher than that of the healthy controls. In conclusion, presence of TLR3 c.1377 TT genotype may have a role in the susceptibility to CCHF. J. Med. Virol. 88:1690-1696, 2016. © 2016 Wiley Periodicals, Inc.

Gene Polymorphism of Toll-Like Receptors and Lung Function at Five to Seven Years of Age after Infant Bronchiolitis

Aim

Toll-like receptors (TLR) play a crucial role in innate immunity, protecting the host from pathogens such as viruses. Genetic variations in TLRs have been associated with the severity of viral bronchiolitis in infancy and with the later occurrence of post-bronchiolitis asthma. The aim of the present study was to evaluate if there are any exploratory associations between TLR gene polymorphisms and lung function at 5 to 7 years of age in former bronchiolitis patients.

Methods

We performed impulse oscillometry (IOS) at the median age of 6.3 years for 103 children who had been hospitalized for bronchiolitis at less than six months of age. The main parameters evaluated were airway resistance and reactance at 5Hz in baseline and post-exercise measurements. Data on single nucleotide polymorphisms (SNP) of TLR1 rs5743618, TLR2 rs5743708, TLR6 rs5743810 and TLR10 rs4129009 (TLR2 subfamily) and TLR3 rs3775291, TLR4 rs4986790, TLR7 rs179008, TLR8 rs2407992 and TLR 9 rs187084 were available for analyses.

Results

The TLR4 rs4986790 wild genotype A/A was associated with a greater Rrs5 response (0.72 vs. -0.42, p = 0.03) to exercise. In TLR6 rs5743810, the minor allele T was associated with greater Rrs5 response (0.80 vs. -0.03, p = 0.04) to exercise. In TLR7 rs179008, the major allele A was associated with baseline decline in dRrs/df (-1.03 vs 0.61, p = 0.01) and increased Fres (2.28 vs. 0.89, p = 0.01) in girls.

Conclusion

Among the nine studied TLRs, only TLR7 rs179008 showed some exploratory associations with post-bronchiolitis lung function deficiency, and polymorphisms of TLR4 rs4986790, and TLR6 rs5743810 in particular, with airway reactivity. These findings call for further confirmatory studies.

Toll-like receptor 2 subfamily gene polymorphisms are associated with Bacillus Calmette-Guérin osteitis following newborn vaccination

AIM

Toll-like receptor (TLR) 1, 2, 6 and 10, the TLR2 subfamily, are known to be associated with immunity against tuberculosis. We evaluated whether polymorphisms in genes encoding TLR1, TLR2 and TLR6 were associated with osteitis in infants who received the Bacillus Calmette-Guérin (BCG) vaccination soon after birth.

METHODS

Blood samples from 132 adults aged 21-49 who had BCG osteitis in early childhood were analysed in a controlled study for TLR1 T1805G (rs5743618), TLR2 G2258A (rs5743708) and TLR6 C745T (rs5743810) gene single nucleotide polymorphisms.

RESULTS

The frequencies of the variant genotypes differed between the cases and controls: 11.4% versus 5.7% for TLR2 G2258A (p = 0.033) and 77.3% versus 61.6% for TLR6 C745T (p = 0.001). The TLR2 and TLR6 variant genotypes were associated with a higher risk of BCG osteitis, with adjusted odds ratios (aOR) of 2.154 (95%CI 1.026-4.521) and 1.907 (95%CI 1.183-3.075), respectively. The frequency of the TLR1 T1805G variant genotype was 19.7% in the cases and 33.6% in the controls (p = 0.003). The TLR1 variant genotype was associated with a lower risk of BCG osteitis (aOR 0.554, 95%CI 0.336-0.911).

CONCLUSION

Gene polymorphisms that regulate the function of the TLR2 subfamily play a role in the development of BCG osteitis in vaccinated infants.

The association of genetic variants in toll-like receptor 2 subfamily with allergy and asthma after hospitalization for bronchiolitis in infancy

BACKGROUND

Toll-like receptors (TLRs) are a pivotal part of the innate immunity system. Variations in TLR genes have been connected to autoimmune conditions, such as allergy and asthma. The TLR2 subfamily comprises TLR1, TLR2, TLR6 and TLR 10. We hypothesized that polymorphism of the TLR2 subfamily may be associated with prevalence of post-bronchiolitic asthma and/or atopy.

METHODS

TLR1rs5743618, TLR2rs5743708 and TLR6rs5743810 single nucleotide polymorphisms of 133 children who had been hospitalized for bronchiolitis at <6 months of age were analyzed. Doctor-diagnosed asthma and atopy as well as their occurrence during the first 6 years of life were evaluated during a follow-up visit.

RESULTS

At the mean age of 6.4 years, asthma was present in 17 (13%) patients, there was asthma diagnosis during the first 6 years of life in 39 (29%) and current doctor-diagnosed allergic rhinitis in 57 (43%) patients. Twenty-four (24%) children with G/G genotype in TLR1 rs5743618 were diagnosed to have asthma between 1 and 6 years of age (vs. 13 (38%) of those with G/T or T/T genotypes; P = 0.04). In addition, 11/60 (18%) children with TLR6 rs5743810 C/T versus 36/73 (49%) children of other genotypes had atopic eczema at follow up. Only 2 children (8%) with wild genotype in all investigated single nucleotide polymorphisms had asthma during the first 6 years of life (vs. 30% in those with variant genotype of TLR1, TLR2 and/or TLR6).

CONCLUSION

In this study, we demonstrated that TLR1 rs5743618 was associated with asthma and atopic eczema during the first 6 years of life after early bronchiolitis. In addition, TLR6 rs5743810 was associated with present atopy at preschool age.

Toll-like receptor 2 subfamily genotypes are not associated with severity of bronchiolitis or postbronchiolitis wheezing in infants

AIM

Expression of toll-like receptor (TLR) 2 subfamily genes, including genes encoding TLR1, TLR2, TLR6 and TLR10, have been connected to allergy and asthma. This controlled study investigated the association of TLR1, TLR2 and TLR6 gene polymorphisms with clinical characteristics and subsequent wheezing in young infants with bronchiolitis.

METHODS

In all, 129 full-term infants hospitalised for bronchiolitis at the age of <6 months were clinically followed up until a mean age of 18 months. Genotyping of the TLR1 T1805G, TLR2 G2258A and TLR6 C745T polymorphisms was carried out by pyrosequencing and in 318 healthy, Finnish controls.

RESULTS

There were no significant associations between TLR1, TLR2 or TLR6 genotypes and severity of bronchiolitis or risk of postbronchiolitis wheezing. TLR6 polymorphism was associated with allergy in univariate analyses. Minor allele frequency (MAF) in the TLR1 gene (17%) in the hospitalised children was similar to our Finnish controls, but different to European controls from other studies. MAF in the TLR6 gene was 50% versus 41% in both the Finnish and European controls. MAF in the TLR2 gene was low (3%) in study subjects and in both controls.

CONCLUSION

TLR2 subfamily gene polymorphisms were not associated with severity of bronchiolitis or risk of postbronchiolitis wheezing.

Distinct signaling pathways regulate TLR2 co-stimulatory function in human T cells

Toll-like receptor 2 (TLR2) serves as a co-stimulatory receptor for human T cells by enhancing T cell receptor (TCR)-induced cytokine production and proliferation. However, it is unknown where signals from the TCR and TLR2 converge to enhance T cell activation. To address this gap, we examined changes in TCR-induced signaling following concurrent TLR2 activation in human T cells. Both proximal TCR-mediated signaling and early NFκB activation were not enhanced by TCR and TLR2 co-activation, potentially due to the association of TLR2 with TLR10. Instead, TLR2 co-induction did augment Akt and Erk1/Erk2 activation in human T cells. These findings demonstrate that TLR2 activates distinct signaling pathways in human T cells and suggest that alterations in expression of TLR2 co-receptors may contribute to aberrant T cell responses.

Leprosy and the human genome

Despite the availability of effective treatment for several decades, leprosy remains an important medical problem in many regions of the world. Infection with Mycobacterium leprae can produce paucibacillary disease, characterized by well-formed granulomas and a Th1 T-cell response, or multibacillary disease, characterized by poorly organized cellular infiltrates and Th2 cytokines. These diametric immune responses confer states of relative resistance or susceptibility to leprosy, respectively, and have well-defined clinical manifestations. As a result, leprosy provides a unique opportunity to dissect the genetic basis of human in vivo immunity. A series of studies over the past 40 years suggests that host genes influence the risk of leprosy acquisition and the predilection for different clinical forms of the disease. However, a comprehensive, cellular, and molecular view of the genes and variants involved is still being assembled. In this article, we review several decades of human genetic studies of leprosy, including a number of recent investigations. We emphasize genetic analyses that are validated by the replication of the same phenotype in independent studies or supported by functional experiments demonstrating biological mechanisms of action for specific polymorphisms. Identifying and functionally exploring the genetic and immunological factors that underlie human susceptibility to leprosy have yielded important insights into M. leprae pathogenesis and are likely to advance our understanding of the immune response to other pathogenic mycobacteria. This knowledge may inform new treatment or vaccine strategies for leprosy or tuberculosis.

Comparative genomics of Toll-like receptor signalling in five species

BACKGROUND

Over the last decade, several studies have identified quantitative trait loci (QTL) affecting variation of immune related traits in mammals. Recent studies in humans and mice suggest that part of this variation may be caused by polymorphisms in genes involved in Toll-like receptor (TLR) signalling. In this project, we used a comparative approach to investigate the importance of TLR-related genes in comparison with other immunologically relevant genes for resistance traits in five species by associating their genomic location with previously published immune-related QTL regions.

RESULTS

We report the genomic localisation of TLR1-10 and ten associated signalling molecules in sheep and pig using in-silico and/or radiation hybrid (RH) mapping techniques and compare their positions with their annotated homologues in the human, cattle and mouse whole genome sequences. We also report medium-density RH maps for porcine chromosomes 8 and 13. A comparative analysis of the positions of previously published relevant QTLs allowed the identification of homologous regions that are associated with similar health traits in several species and which contain TLR related and other immunologically relevant genes. Additional evidence was gathered by examining relevant gene expression and association studies.

CONCLUSION

This comparative genomic approach identified eight genes as potentially causative genes for variations of health related traits. These include susceptibility to clinical mastitis in dairy cattle, general disease resistance in sheep, cattle, humans and mice, and tolerance to protozoan infection in cattle and mice. Four TLR-related genes (TLR1, 6, MyD88, IRF3) appear to be the most likely candidate genes underlying QTL regions which control the resistance to the same or similar pathogens in several species. Further studies are required to investigate the potential role of polymorphisms within these genes.

Signatures of natural selection are not uniform across genes of innate immune system, but purifying selection is the dominant signature

We tested the opposing views concerning evolution of genes of the innate immune system that (i) being evolutionary ancient, the system may have been highly optimized by natural selection and therefore should be under purifying selection, and (ii) the system may be plastic and continuing to evolve under balancing selection. We have resequenced 12 important innate-immunity genes (CAMP, DEFA4, DEFA5, DEFA6, DEFB1, MBL2, and TLRs 1, 2, 4, 5, 6, and 9) in healthy volunteers (n = 171) recruited from a region of India with high microbial load. We have compared these data with those of European-Americans (EUR) and African-Americans (AFR). We have found that most of the human haplotypes are many mutational steps away from the ancestral (chimpanzee) haplotypes, indicating that humans may have had to adapt to new pathogens. The haplotype structures in India are significantly different from those of EUR and AFR populations, indicating local adaptation to pathogens. In these genes, there is (i) generally an excess of rare variants, (ii) high, but variable, degrees of extended haplotype homozygosity, (iii) low tolerance to nonsynonymous changes, (iv) essentially one or a few high-frequency haplotypes, with star-like phylogenies of other infrequent haplotypes radiating from the modal haplotypes. Purifying selection is the most parsimonious explanation operating on these innate immunity genes. This genetic surveillance system recognizes motifs in pathogens that are perhaps conserved across a broad range of pathogens. Hence, functional constraints are imposed on mutations that diminish the ablility of these proteins to detect pathogens.