Background The genetic determinants of the human innate immune response are poorly understood. Apolipoprotein (Apo) E, a lipid-trafficking protein that affects inflammation, has well-described ...wild-type (ε3) and disease-associated (ε2 and ε4) alleles, but its connection to human innate immunity is undefined. Objective We sought to define the relationship of APOε4 to the human innate immune response. Methods We evaluated APOε4 in several functional models of the human innate immune response, including intravenous LPS challenge in human subjects, and assessed APOε4 association to organ injury in patients with severe sepsis, a disease driven by dysregulated innate immunity. Results Whole blood from healthy APOε3 / APOε4 volunteers induced higher cytokine levels on ex vivo stimulation with Toll-like receptor (TLR) 2, TLR4, or TLR5 ligands than blood from APOε3 / APOε3 patients, whereas TLR7/8 responses were similar. This was associated with increased lipid rafts in APOε3/APOε4 monocytes. By contrast, APOε3 / APOε3 and APOε3 / APOε4 serum neutralized LPS equivalently and supported similar LPS responses in Apoe -deficient macrophages, arguing against a differential role for secretory APOE4 protein. After intravenous LPS, APOε3/APOε4 patients had higher hyperthermia and plasma TNF-α levels and earlier plasma IL-6 than APOε3/APOε3 patients. APOE4-targeted replacement mice displayed enhanced hypothermia, plasma cytokines, and hepatic injury and altered splenic lymphocyte apoptosis after systemic LPS compared with APOE3 counterparts. In a cohort of 828 patients with severe sepsis, APOε4 was associated with increased coagulation system failure among European American patients. Conclusions APOε4 is a determinant of the human innate immune response to multiple TLR ligands and associates with altered patterns of organ injury in human sepsis.
Background Atopic dermatitis (AD) is characterized by dry skin and a hyperactive immune response to allergens, 2 cardinal features that are caused in part by epidermal barrier defects. Tight ...junctions (TJs) reside immediately below the stratum corneum and regulate the selective permeability of the paracellular pathway. Objective We evaluated the expression/function of the TJ protein claudin-1 in epithelium from AD and nonatopic subjects and screened 2 American populations for single nucleotide polymorphisms in the claudin-1 gene (CLDN1). Methods Expression profiles of nonlesional epithelium from patients with extrinsic AD, nonatopic subjects, and patients with psoriasis were generated using Illumina's BeadChips. Dysregulated intercellular proteins were validated by means of tissue staining and quantitative PCR. Bioelectric properties of epithelium were measured in Ussing chambers. Functional relevance of claudin-1 was assessed by using a knockdown approach in primary human keratinocytes. Twenty-seven haplotype-tagging SNPs in CLDN1 were screened in 2 independent populations with AD. Results We observed strikingly reduced expression of the TJ proteins claudin-1 and claudin-23 only in patients with AD, which were validated at the mRNA and protein levels. Claudin-1 expression inversely correlated with TH 2 biomarkers. We observed a remarkable impairment of the bioelectric barrier function in AD epidermis. In vitro we confirmed that silencing claudin-1 expression in human keratinocytes diminishes TJ function while enhancing keratinocyte proliferation. Finally, CLDN1 haplotype-tagging SNPs revealed associations with AD in 2 North American populations. Conclusion Collectively, these data suggest that an impairment in tight junctions contributes to the barrier dysfunction and immune dysregulation observed in AD subjects and that this may be mediated in part by reductions in claudin-1.
Abstract Background Chronic schistosomiasis and its severe complication, periportal fibrosis, are characterized by a predominant Th2 response. To date, specific SNPs in ST2 have been some of the most ...consistently associated genetic variants for asthma. Objectives We investigated the role of ST2 (a receptor for the Th2 cytokine IL-33) in chronic and late-stage schistosomiasis caused by S. japonicum , and the potential effect of ST2 genetic variants on stage of disease and ST2 expression. Methods 947 adult participants (339 with end-stage schistosomiasis and liver cirrhosis, 307 with chronic infections without liver fibrosis, and 301 health controls) were recruited from a S. japonicum -endemic area (Hubei, China). Six ST2 SNPs were genotyped. Serum sST2 was measured by ELISA, and ST2 expression in normal liver tissues, HBV-induced fibrotic liver tissues and S. japonicum -induced fibrotic liver tissues was measured by immunohistochemistry. Results: sST2 levels were significantly higher in the end-stage group (36.04 95 %CI 33.85;38.37) compared to chronic cases and controls (22.7 95% CI 22.0;23.4, p-value < 1E-10). In addition, S. japonicum -induced fibrotic liver tissues showed increased ST2 staining compared to normal liver tissues (p-value=0.0001). Markers rs12712135, rs1420101 and rs6543119 were strongly associated with sST2 levels (p-values 2E-10, 5E-05 and 6E-05 respectively), and these results were replicated in an independent cohort from Brazil living in a S. mansoni endemic region. Conclusion We demonstrate for the first time that end-stage schistosomiasis is associated with elevated sST2 levels, and show that ST2 genetic variants are associated with sST2 levels in patients with schistosomiasis.
Background Asthma is a complex disease characterized by striking ethnic disparities not explained entirely by environmental, social, cultural, or economic factors. Of the limited genetic studies ...performed on populations of African descent, notable differences in susceptibility allele frequencies have been observed. Objectives We sought to test the hypothesis that some genes might contribute to the profound disparities in asthma. Methods We performed a genome-wide association study in 2 independent populations of African ancestry (935 African American asthmatic cases and control subjects from the Baltimore–Washington, DC, area and 929 African Caribbean asthmatic subjects and their family members from Barbados) to identify single-nucleotide polymorphisms (SNPs) associated with asthma. Results A meta-analysis combining these 2 African-ancestry populations yielded 3 SNPs with a combined P value of less than 10−5 in genes of potential biologic relevance to asthma and allergic disease: rs10515807, mapping to the α-1B-adrenergic receptor (ADRA1B) gene on chromosome 5q33 (3.57 × 10−6 ); rs6052761, mapping to the prion-related protein (PRNP) gene on chromosome 20pter-p12 (2.27 × 10−6 ); and rs1435879, mapping to the dipeptidyl peptidase 10 (DPP10) gene on chromosome 2q12.3-q14.2. The generalizability of these findings was tested in family and case-control panels of United Kingdom and German origin, respectively, but none of the associations observed in the African groups were replicated in these European studies. Evidence for association was also examined in 4 additional case-control studies of African Americans; however, none of the SNPs implicated in the discovery population were replicated. Conclusions This study illustrates the complexity of identifying true associations for a complex and heterogeneous disease, such as asthma, in admixed populations, especially populations of African descent.
Allergic asthma is a complex disorder that results from a combination of genetic and environmental factors. Studies suggest that helminth infections can activate a regulatory network characterized by ...the production of regulatory cytokines, such as interleukin 10 and transforming growth factor β1 (TGF-β1) and subsequently protect against immune-mediated diseases, such as asthma. On the other hand, TGF-β1 is increased in the lungs of individuals with asthma and may modulate airway inflammation. The role of TGF- β 1 single-nucleotide polymorphisms (SNPs) in allergic disease remains inconclusive.
To evaluate the effects of genetic variations in the TGF-β1 on allergy and helminths infections in children.
We tested for association among 4 TGF-β1 SNPs and allergic asthma, specific IgE, skin prick test result, and IL-10 production in 1,335 Brazilians. In addition, we analyzed the association with markers of helminth infection (parasite burden, anti-Ascaris IgE, and worm specific IgG4). The polymorphisms were genotyped using Taq Man probes.
We found an association between rs1800470 (C allele) and atopic wheezing (odds ratio OR, 0.60; 95% confidence interval CI, 0.37-0.95) and markers of allergy (OR, 0.41; 95% CI, 0.22-0.79). In contrast, a positive association was observed between the haplotype ACCA and Trichuris trichiura infection (OR, 1.85; P = .003) and Ascaris lumbricoides infection (OR, 2.01; P < .001). This haplotype was also associated with increased IL-10 production (β = 50.7; P < .001).
Individuals with TGF-β1 polymorphisms have an increased susceptibility to helminth infections and a lower risk of developing allergy. These studies suggest that immune modulation of allergic disease results not only from environmental factors but also from genetic susceptibility and IL-10 production.
Background Helminth infections are associated with protection against allergies. It is postulated that IL-10 production after helminth infection suppresses skin hypersensitivity and increases IgG4 ...production, protecting against allergies. Objective We aimed to determine whether IL10 polymorphisms are associated with helminth infection and the risk of wheeze and allergy. Methods Twelve IL10 single nucleotide polymorphisms were genotyped in 1353 children aged 4 to 11 years living in a poor urban area in Salvador, Brazil. Wheezing status, Ascaris lumbricoides and Trichuris trichiura infection, IL-10 production by peripheral blood leukocytes stimulated with A lumbricoides extract, serum total IgE levels, specific IgE levels, skin prick test responses to common aeroallergens, and IgG4 and IgE anti– A lumbricoides antibody levels were measured in all children. Association tests were performed by using logistic or linear regression when appropriate, including sex, age, helminth infection, and principal components for ancestry informative markers as covariates by using PLINK. Results Allele G of marker rs3024496 was associated with the decreased production of IL-10 by peripheral blood leukocytes in response to A lumbricoides stimulation. Allele C of marker rs3024498 was negatively associated with helminth infection or its markers. Marker rs3024492 was positively associated with the risk of atopic wheeze, total IgE levels, and skin prick test responses to cockroach. Conclusions Our findings suggest that IL10 polymorphisms might play a role in the production of IL-10, helminth infection, and allergy. We hypothesize that polymorphisms related to protection against helminths, which would offer an evolutionary advantage to subjects in the past, might be associated with increased risk of allergic diseases.
Background Lung function is a long-term predictor of mortality and morbidity. Objective We sought to identify single nucleotide polymorphisms (SNPs) associated with lung function. Methods We ...performed a genome-wide association study (GWAS) of FEV1 , forced vital capacity (FVC), and FEV1 /FVC in 1144 Hutterites aged 6 to 89 years, who are members of a founder population of European descent. We performed least absolute shrinkage and selection operation regression to select the minimum set of SNPs that best predict FEV1 /FVC in the Hutterites and used the GRAIL algorithm to mine the Gene Ontology database for evidence of functional connections between genes near the predictive SNPs. Results Our GWAS identified significant associations between FEV1 /FVC and SNPs at the THSD4-UACA-TLE3 locus on chromosome 15q23 ( P = 5.7 × 10−8 to 3.4 × 10−9 ). Nine SNPs at or near 4 additional loci had P < 10−5 with FEV1 /FVC. Only 2 SNPs were found with P < 10−5 for FEV1 or FVC. We found nominal levels of significance with SNPs at 9 of the 27 previously reported loci associated with lung function measures. Among a predictive set of 80 SNPs, 6 loci were identified that had a significant degree of functional connectivity (GRAIL P < .05), including 3 clusters of β-defensin genes, 2 chemokine genes ( CCL18 and CXCL12 ), and TNFRSF13B. Conclusion This study identifies genome-wide significant associations and replicates results of previous GWASs. Multimarker modeling implicated for the first time common variation in genes involved in antimicrobial immunity in airway mucosa that influences lung function.
Background Loss-of-function null mutations R501X and 2282del4 in the skin barrier gene, filaggrin ( FLG ), represent the most replicated genetic risk factors for atopic dermatitis (AD). Associations ...have not been reported in African ancestry populations. Atopic dermatitis eczema herpeticum (ADEH) is a rare but serious complication of AD resulting from disseminated cutaneous herpes simplex virus infections. Objective We aimed to determine whether FLG polymorphisms contribute to ADEH susceptibility. Methods Two common loss-of-function mutations plus 9 FLG single nucleotide polymorphisms were genotyped in 278 European American patients with AD, of whom 112 had ADEH, and 157 nonatopic controls. Replication was performed on 339 African American subjects. Results Significant associations were observed for both the R501X and 2282del4 mutations and AD among European American subjects ( P = 1.46 × 10−5 , 3.87 × 10−5 , respectively), but the frequency of the R501X mutation was 3 times higher (25% vs 9%) for ADEH than for AD without eczema herpeticum (EH) (odds ratio OR, 3.4; 1.7-6.8; P = .0002). Associations with ADEH were stronger with the combined null mutations (OR, 10.1; 4.7-22.1; P = 1.99 × 10−11 ). Associations with the R501X mutation were replicated in the African American population; the null mutation was absent among healthy African American subjects, but present among patients with AD (3.2%; P = .035) and common among patients with ADEH (9.4%; P = .0049). However, the 2282del4 mutation was absent among African American patients with ADEH and rare (<1%) among healthy individuals. Conclusion The R501X mutation in the gene encoding filaggrin, one of the strongest genetic predictors of AD, confers an even greater risk for ADEH in both European and African ancestry populations, suggesting a role for defective skin barrier in this devastating condition.
Quality controls were performed as described previously.6 The Cochran-Armitage trend test was used to test for association between each SNP and disease status by using PLINK.7 AÂ linear regression ...analysis was performed to test for associations between individual genetic markers and log-adjusted total serum IgE (tIgE) concentrations and log-adjusted Eczema Area and Severity Index (EASI) scores, and a multiple logistic regression model was used to test for SNP-SNP interactions among cases only between TSLP and its receptors by using SAS version 9.1 software (SAS Institute, Inc, Cary, NC).
Background A subset of atopic dermatitis is associated with increased susceptibility to eczema herpeticum (ADEH+). We previously reported that common single nucleotide polymorphisms (SNPs) in the ...IFN-γ (IFNG) and IFN-γ receptor 1 (IFNGR1) genes were associated with the ADEH+ phenotype. Objective We sought to interrogate the role of rare variants in interferon pathway genes for the risk of ADEH+. Methods We performed targeted sequencing of interferon pathway genes ( IFNG , IFNGR1 , IFNAR1 , and IL12RB1 ) in 228 European American patients with AD selected according to their eczema herpeticum status, and severity was measured by using the Eczema Area and Severity Index. Replication genotyping was performed in independent samples of 219 European American and 333 African American subjects. Functional investigation of loss-of-function variants was conducted by using site-directed mutagenesis. Results We identified 494 single nucleotide variants encompassing 105 kb of sequence, including 145 common, 349 (70.6%) rare (minor allele frequency <5%), and 86 (17.4%) novel variants, of which 2.8% were coding synonymous, 93.3% were noncoding (64.6% intronic), and 3.8% were missense. We identified 6 rare IFNGR1 missense variants, including 3 damaging variants (Val14Met V14M, Val61Ile, and Tyr397Cys Y397C) conferring a higher risk for ADEH+ ( P = .031). Variants V14M and Y397C were confirmed to be deleterious, leading to partial IFNGR1 deficiency. Seven common IFNGR1 SNPs, along with common protective haplotypes (2-7 SNPs), conferred a reduced risk of ADEH+ ( P = .015-.002 and P = .0015-.0004, respectively), and both SNP and haplotype associations were replicated in an independent African American sample ( P = .004-.0001 and P = .001-.0001, respectively). Conclusion Our results provide evidence that both genetic variants in the gene encoding IFNGR1 are implicated in susceptibility to the ADEH+ phenotype.
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