RESUMEN
BACKGROUND: IL-13 is a signature cytokine of the helper T cell type 2 (TH2) pathway which underlies host defense to helminthic infection and activates production of IgE in both parasitized populations and in urban settings after allergen exposure. METHODOLOGY/PRINCIPAL FINDINGS: Two functional polymorphisms in IL13, rs1800925 (or c.1-1111C>T) and rs20541 (or R130Q) were previously found to be associated with Schistosoma hematobium infection intensity. They have not been thoroughly explored in S. mansoni-endemic populations, however, and were selected along with 5 tagging SNPs for genotyping in 812 individuals in 318 nuclear families from a schistosomiasis-endemic area of Conde, Bahia, in Brazil. Regression models using GEE to account for family membership and family-based quantitative transmission disequilibrium tests (QTDT) were used to evaluate associations with total serum IgE (tIgE) levels and S. mansoni fecal egg counts adjusted for non-genetic covariates. We identified a protective effect for the T allele at rs20541 (Pâ=â0.005) against high S. mansoni egg counts, corroborated by QTDT (Pâ=â0.014). Our findings also suggested evidence for protective effects for the T allele at rs1800925 and A allele at rs2066960 after GEE analysis only (Pâ=â0.050, 0.0002). CONCLUSIONS/SIGNIFICANCE: The two functional variants in IL13 are protective against high S. mansoni egg counts. These markers showed no evidence of association with tIgE levels, unlike tIgE levels previously studied in non-parasitized or atopic study populations.
Asunto(s)
Interleucina-13/genética , Polimorfismo de Nucleótido Simple , Schistosoma mansoni/patogenicidad , Esquistosomiasis mansoni/genética , Esquistosomiasis mansoni/prevención & control , Adulto , Animales , Brasil/epidemiología , Enfermedades Endémicas/prevención & control , Femenino , Humanos , Inmunoglobulina E/sangre , Desequilibrio de Ligamiento , Masculino , Esquistosomiasis mansoni/epidemiología , Esquistosomiasis mansoni/inmunología , Células Th2/inmunologíaRESUMEN
We describe a Turkish patient with tyrosine kinase 2 deficiency who suffered from disseminated Bacille Calmette-Guerin infection, neurobrucellosis, and cutaneous herpes zoster infection. Tyrosine kinase 2 deficiency should be considered in patients susceptible to herpes viruses and intramacrophage pathogens even in the absence of atopy, high serum IgE, and staphylococcal disease.
Asunto(s)
Síndromes de Inmunodeficiencia/enzimología , TYK2 Quinasa/deficiencia , Niño , Diagnóstico Diferencial , Estudios de Seguimiento , Humanos , Síndromes de Inmunodeficiencia/diagnóstico , Síndrome de Job/diagnóstico , Imagen por Resonancia Magnética , Masculino , TYK2 Quinasa/sangreRESUMEN
Sialic acid-binding immunoglobulin-like lectin-8 (Siglec-8) promotes the apoptosis of eosinophils and inhibits FcvarepsilonRI-dependent mediator release from mast cells. We investigated the genetic association between sequence variants in Siglec-8 and diagnosis of asthma, total levels of serum IgE (tIgE), and diagnosis of eosinophilic esophagitis (EE) in diverse populations. The effect of sequence variants on Siglec-8 glycan ligand-binding activity was also examined. Significant association with asthma was observed for SNP rs36498 (odds ratios (OR), 0.69, P=8.8 x 10(-5)) among African Americans and for SNP rs10409962 (Ser/Pro) in the Japanese population (OR, 0.69, P=0.019). Supporting this finding, we observed association between SNP rs36498 and current asthma among Brazilian families (P=0.013). Significant association with tIgE was observed for SNP rs6509541 among African Americans (P=0.016), and replicated among the Brazilian families (P=0.02). In contrast, no association was observed with EE in Caucasians. By using a synthetic polymer decorated with 6'-sulfo-sLe(x), a known Siglec-8 glycan ligand, we did not find any differences between the ligand-binding activity of HEK293 cells stably transfected with the rs10409962 risk allele or the WT allele. However, our association results suggest that the Siglec8 gene may be a susceptibility locus for asthma.
Asunto(s)
Antígenos CD/genética , Antígenos de Diferenciación de Linfocitos B/genética , Asma/genética , Predisposición Genética a la Enfermedad , Lectinas/genética , Polimorfismo de Nucleótido Simple , Adolescente , Adulto , Negro o Afroamericano/genética , Pueblo Asiatico/genética , Asma/etnología , Brasil , Niño , Preescolar , Femenino , Estudio de Asociación del Genoma Completo , Humanos , Masculino , Persona de Mediana Edad , Polimorfismo de Nucleótido Simple/fisiología , Población Blanca/genética , Adulto JovenRESUMEN
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 alpha-1B-adrenergic receptor (ADRA1B) gene on chromosome 5q33 (3.57 x 10(-6)); rs6052761, mapping to the prion-related protein (PRNP) gene on chromosome 20pter-p12 (2.27 x 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.
Asunto(s)
Asma/genética , Población Negra/genética , Predisposición Genética a la Enfermedad/genética , Estudio de Asociación del Genoma Completo , Adulto , Negro o Afroamericano/genética , Barbados , Femenino , Genotipo , Humanos , Masculino , Persona de Mediana Edad , Polimorfismo de Nucleótido SimpleRESUMEN
RATIONALE: Asthma prevalence and severity are high among underserved minorities, including those of African descent. The Duffy antigen/receptor for chemokines is the receptor for Plasmodium vivax on erythrocytes and functions as a chemokine-clearing receptor. Unlike European populations, decreased expression of the receptor on erythrocytes is common among populations of African descent, and results from a functional T-46C polymorphism (rs2814778) in the promoter. This variant provides an evolutionary advantage in malaria-endemic regions, because Duffy antigen/receptor for chemokines-negative erythrocytes are more resistant to infection by P. vivax. OBJECTIVES: To determine the role of the rs2814778 polymorphism in asthma and atopy as measured by total serum IgE levels among four populations of African descent (African Caribbean, African American, Brazilian, and Colombian) and a European American population. METHODS: Family-based association tests were performed in each of the five populations to test for association between the rs2814778 polymorphism and asthma or total IgE concentration. MEASUREMENTS AND MAIN RESULTS: Asthma was significantly associated with the rs2814778 polymorphism in the African Caribbean, Colombian, and Brazilian families (P < 0.05). High total IgE levels were associated with this variant in African Caribbean and Colombian families (P < 0.05). The variant allele was not polymorphic among European Americans. CONCLUSIONS: Susceptibility to asthma and atopy among certain populations of African descent is influenced by a functional polymorphism in the gene encoding Duffy antigen/receptor for chemokines. This genetic variant, which confers resistance to malarial parasitic infection, may also partially explain ethnic differences in morbidity of asthma.
Asunto(s)
Asma/genética , Población Negra/genética , Sistema del Grupo Sanguíneo Duffy/genética , Predisposición Genética a la Enfermedad/genética , Polimorfismo de Nucleótido Simple/genética , Receptores de Superficie Celular/genética , Adolescente , Adulto , Barbados , Brasil , Estudios de Casos y Controles , Colombia , Femenino , Humanos , Inmunoglobulina E/sangre , Masculino , Persona de Mediana Edad , Estados Unidos , Población Blanca/genéticaRESUMEN
BACKGROUND: Evidence of genetic control for total serum IgE (tIgE) level has been reported in multiple populations, although populations with substantial exposure to helminths have yielded lower estimates of heritability, despite evidence suggesting that genes also control a significant portion of the variation in the number of Schistosoma mansoni eggs per gram of fecal matter. METHODS: By use of a whole-population ascertainment scheme, 822 individuals were enrolled from a schistosomiasis-endemic area in Conde, Bahia, in Brazil. Heritability was estimated by using an additive polygenic model, and segregation analysis was performed for 2 quantitative traits, tIgE level and egg count. RESULTS: After adjusting for nongenetic covariates, the heritability of log-transformed tIgE level and log-transformed egg count was estimated at 60% and 31%, respectively. No evidence for a single major gene controlling tIgE level or egg count was observed in segregation analysis for 781 individuals and 403 individuals, respectively, in 318 families, however, which suggests complex biological control. CONCLUSIONS: The high heritability of tIgE level indicates that genetic factors are likely to control tIgE level even in the presence of helminthic infection. Substantial heritability for the burden of S. mansoni infection was confirmed in these Brazilian families. Further genetic studies will be needed to dissect the specific genetic factors that underlie these traits.
Asunto(s)
Enfermedades Endémicas , Inmunoglobulina E/sangre , Schistosoma mansoni/inmunología , Schistosoma mansoni/patogenicidad , Esquistosomiasis mansoni/epidemiología , Esquistosomiasis mansoni/genética , Adolescente , Adulto , Anciano , Animales , Anticuerpos Antihelmínticos/sangre , Brasil/epidemiología , Niño , Heces/parasitología , Femenino , Predisposición Genética a la Enfermedad , Humanos , Masculino , Persona de Mediana Edad , Recuento de Huevos de Parásitos , Schistosoma mansoni/crecimiento & desarrollo , Schistosoma mansoni/aislamiento & purificación , Esquistosomiasis mansoni/inmunología , Esquistosomiasis mansoni/parasitologíaRESUMEN
BACKGROUND: Myosin light chain kinase (MYLK) is a multifunctional protein involved in regulation of airway hyperreactivity and other activities relevant to asthma. OBJECTIVE: To determine the role of MYLK gene variants in asthma among African Caribbean and African American populations. METHODS: We performed association tests between single nucleotide polymorphisms (SNPs) in the MYLK gene and asthma susceptibility and total serum IgE concentrations in 2 independent, family-based populations of African descent. Previously we identified variants/haplotypes in MYLK that confer risk for sepsis and acute lung injury; we compared findings from our asthma populations to findings in the African American sepsis and acute lung injury groups. RESULTS: Significant associations between MYLK SNPs and asthma and total serum IgE concentrations were observed in the African Caribbean families: a promoter SNP (rs936170) in the smooth muscle form gave the strongest association (P=.009). A haplotype including rs936170 corresponding to the actin-binding activity of the nonmuscle and smooth muscle forms was negatively associated with asthma (eg, decreased risk in both the American (P=.005) and Caribbean families (P=.004), and was the same haplotype that conferred risk for severe sepsis (P=.002). RNA expression studies on PBMCs and rs936170 suggested a significant decrease in MYLK expression among patients with asthma with this variant (P=.025). CONCLUSION: MYLK polymorphisms may function as a common genetic factor in clinically distinct disease involving broanchial smooth muscle contraction and inflammation. CLINICAL IMPLICATIONS: Genetic variants in MYLK are significantly associated with both asthma and sepsis in populations of African ancestry (AU)
Asunto(s)
Humanos , Asma , Haplotipos , Sepsis , Quinasa de Cadena Ligera de Miosina/genética , Región del Caribe , BarbadosRESUMEN
Few comparison studies have been performed on single nucleotide polymorphism (SNP) tagging methods to examine their consistency and effectiveness in terms of inferences about association with disease. We applied several SNP tagging methods to SNPs on chromosome 12q (n=713) and compared the utility of these methods to detect association for asthma and serum IgE levels among a sample of African Caribbean families from Barbados selected through asthmatic probands. We found that a high level of information regarding association is retained in Clayton's htSNP, Stram's TagSNP, and de Bakker's Tagger. We also found a high degree of consistency between TagSNP and Tagger. Using this set of 713 SNPs on chromosome 12q, our study provides insight towards analytic strategies for future studies of complex traits.
Asunto(s)
Asma/genética , Población Negra/genética , Cromosomas Humanos Par 12/genética , Inmunoglobulina E/sangre , Polimorfismo de Nucleótido Simple/genética , Barbados , Humanos , Desequilibrio de LigamientoRESUMEN
BACKGROUND: Both a functional promoter polymorphism in the gene encoding CD14 (C-260T) and exposure to endotoxin are believed to play key roles in modulating the immune response and expression of atopic disease. OBJECTIVE: We aimed to evaluate the role of the CD14 C-260T polymorphism in a population of African descent and to test for interaction between this genotype and house dust endotoxin (HDE) exposure on atopic phenotypes. METHODS: Asthmatic probands and their families were recruited as part of the Barbados Asthma Genetics Study. The C-260T polymorphism and two additional CD14 promoter markers (G-1461T, C-1721T) were genotyped. Endotoxin was measured in house dust samples. RESULTS: Using a Family-Based Association Test, the C-260T allele appeared to be protective against asthma ( z = -2.444; P = .015) and asthma severity ( z = -2.615; P = .009) under a recessive model. No significant associations were observed for the G-1461T and C-1721T markers both individually and in haplotypes. In a case-control analysis, the CD14 TT genotype was found to reduce risk of asthma compared with the CD14 CC/CT genotypes (odds ratio [OR], 0.26; 95% CI, 0.14-0.49) and was associated with lower asthma severity scores ( P < .002). The TT genotype might protect against asthma for individuals with low HDE (OR, 0.09; 95% CI, 0.03-0.24), but may be a risk factor for individuals with high HDE (OR, 11.66; 95% CI, 1.03-131.7), suggesting a gene-environment interaction. CONCLUSION: These data suggest that the CD14-260 polymorphism may play a role in controlling risk to atopic disease and underscore the importance of incorporating key environmental exposures into studies of genetic risk factors.
Asunto(s)
Asma/etiología , Polvo/análisis , Endotoxinas/análisis , Receptores de Lipopolisacáridos/genética , Polimorfismo Genético , Adulto , Asma/genética , Barbados , Estudios de Casos y Controles , Composición Familiar , Femenino , Genotipo , Humanos , MasculinoRESUMEN
BACKGROUND: Both a functional promoter polymorphism in the gene encoding CD14 (C-260T) and exposure to endotoxin are believed to play key roles in modulating the immune response and expression of atopic disease. OBJECTIVE: We aimed to evaluate the role of the CD14 C-260T polymorphism in a population of African descent and to test for interaction between this genotype and house dust endotoxin (HDE) exposure on atopic phenotypes. METHODS: Asthmatic probands and their families were recruited as part of the Barbados Asthma Genetics Study. The C-260T polymorphism and two additional CD14 promoter markers (G-1461T, C-1721T) were genotyped. Endotoxin was measured in house dust samples. RESULTS: Using a Family-Based Association Test, the C-260T allele appeared to be protective against asthma (z=−2.444; P=.015) and asthma severity (z=−2.615; P=.009) under a recessive model. No significant associations were observed for the G-1461T and C-1721T markers both individually and in haplotypes. In a case-control analysis, the CD14 TT genotype was found to reduce risk of asthma compared with the CD14 CC/CT genotypes (odds ratio [OR], 0.26; 95% CI, 0.14-0.49) and was associated with lower asthma severity scores (P < .002). The TT genotype might protect against asthma for individuals with low HDE (OR, 0.09; 95% CI, 0.03-0.24), but may be a risk factor for individuals with high HDE (OR, 11.66; 95% CI, 1.03-131.7), suggesting a gene-environment interaction. CONCLUSION: These data suggest that the CD14-260 polymorphism may play a role in controlling risk to atopic disease and underscore the importance of incorporating key environmental exposures into studies of genetic risk factors.