IL-13 polymorphisms contribute to the risk of asthma: a meta-analysis

Evaluation of IL-4 and IL-13 Single Nucleotide Polymorphisms and Their Association With Childhood Asthma and Its Severity: A Hospital-Based Case-Control Study

BACKGROUND AND OBJECTIVES

Asthma is a common, chronic, atopic respiratory disease that is on the rise among children and adults worldwide. Various environmental, genetic, and biological interactions contribute to the surge in susceptibility to this disease. Interleukin (IL) genes, particularly IL-4 and IL-13, have been linked to asthma pathogenesis. The present study aims to investigate the genetic aberrations, specifically single nucleotide polymorphisms (SNPs) of IL-4 and IL-13, and their association with childhood asthma and its severity.

METHODS

An unmatched hospital-based case-control study was conducted in a tertiary care hospital in Assam, India. The sample size was calculated to be 120 (60 cases and 60 controls) using the Epi Info software version 7.2 (Centers for Disease Control and Prevention, Atlanta, GA, USA), assuming a confidence interval of 95%, a power of the study at 80%, a ratio of control to cases as 1, a proportion of controls with exposure at 22%, and a proportion of cases with exposure at 46%. A total of 53 clinically diagnosed cases of childhood asthma in the age range of three to 12 years and 39 healthy controls free from respiratory diseases and having no history of asthma and/or allergy of the same age group attending a tertiary care hospital were included in the study. Children who never had asthma or allergies and who did not suffer from any upper or lower respiratory infections for the previous four weeks were considered controls. Prior informed consent and ethical clearance were obtained. Very seriously ill cases and controls were excluded from the study. The genetic investigation used polymerase chain reaction (PCR), followed by restriction fragment length polymorphism (RFLP), to discover SNPs in the IL-4 and IL-13 genes. Sequencing analysis was done for the cases with +2044 G>A of the IL-13 gene in relation to the severity of the disease. The difference in the proportions of specific SNPs between cases and controls was analyzed using the χ2 test (a p-value of <0.05 was considered significant).

RESULTS

Both the rs2070874 and rs2243250 polymorphisms of IL-4 showed no statistically significant associations. The mutation of the IL-13 gene in 1111C>T was higher among cases than controls. Both genotypic and allelic distributions of the +2044G>A polymorphism of the IL-13 gene revealed a significant association (p<0.05) with the severity of the disease.

CONCLUSION

Genetic aberrations in SNPs of IL-4 and IL-13 are prevalent among the pediatric patients of the study region. The SNP +2044G>A of IL-13 is instrumental in disease manifestation and severity among the pediatric population of the study region.

Pb and Cd exposure linked with Il-10 and Il-13 gene polymorphisms in asthma risk relevant immunomodulation in children

Genetic variants and environmental factor of heavy metal exposure accelerate the risk of immune-mediated respiratory diseases, including asthma in children. This study aims to investigate the effects and interaction of Pb, Cd exposure from e-waste and interleukin (IL)-10, IL-13 gene polymorphisms on interleukin expressions in children. Pb, Cd levels, Il-10 (rs1800871, rs1800872, rs1800896) and Il-13 (rs20541, rs1800925) polymorphisms were determined in blood or urine of 155 children (75 from e-waste-exposed area, Guiyu and 80 from reference area, Haojiang). Blood Pb and urine Cd levels of e-waste-exposed children were both higher (mean: 5.89 vs. 3.35 μg/dL; 6.04 vs. 1.82 μg/g, both P < 0.05). Exposed children had a larger proportion of high blood Pb level (> 5.00 μg/dL) (66.67% vs. 4.11%, P < 0.001), but they had no statistically different proportion of high urine Cd level (> 1.00 μg/g creatinine). Median levels of IL-13 decreased (3.674 vs. 4.410 ng/L, P < 0.01), but of IL-10 did not vary in serum of exposed children. The analyses revealed no significant associations of Pb or Cd with Il-10 or Il-13 gene polymorphisms. The high blood Pb and urine Cd level were respectively associated with the low IL-13 ( < 3.696 ng/L) and low IL-10 ( < 0.361 ng/L) level, after adjustment for children's age, gender, and BMI (both P ≤ 0.05). Children homozygous carrying major allele for Il-13 (rs20541 and rs1800925) had additive interactions with high blood Pb level on low IL-13 expression (OR = 5.37, 95% CI: 1.96, 14.73 and OR = 8.45, 95% CI: 2.61, 27.32; both P ≤ 0.001). In contrast, no interaction was observed amongst Pb or Cd with Il-10 gene polymorphisms on its expression. Our findings suggest that Pb exposure interacting with Il-13 gene polymorphisms negatively regulates IL-13 expression, which may pose a risk to abnormal asthma-relevant immunomodulation in preschool children.

Convergent Evidence Supports TH2LCRR as a Novel Asthma Susceptibility Gene

Asthma is a common complex disease with apparent genetic predispositions, and previous genome-wide association studies suggest that rs1295686 within the IL13 (interleukin 13) gene is significantly associated with asthma. Analysis of the data provided by the 1000 Genomes Project indicated that there are additional four SNPs in nearly complete linkage disequilibrium with rs1295686 in Caucasians. However, the causal SNPs and the associated mechanism remain unclear. To investigate this issue, functional genomics approaches were utilized to analyze the functions of these SNPs. Dual-luciferase assays indicated that the functional SNP is not rs1295686 but a haplotype consisting of other three SNPs, rs1295685, rs848 and rs847. Through chromosome conformation capture, it was found that the enhancer containing the three functional SNPs interacts with the promoter of TH2LCRR (T helper type 2 locus control region associated RNA), a recently identified long non-coding RNA. RNA-seq data analysis indicated that TH2LCRR expression is significantly increased in asthma patients and is dependent on the genotype at this locus, indicating that TH2LCRR is a novel susceptibility gene for asthma and that these SNPs confer asthma risk by regulating TH2LCRR expression. By chromatin immunoprecipitation, the related transcription factors that bind in the region surrounding these three SNPs were identified, and their interactions were investigated by functional genomics approaches. Our effort identified a novel mechanism through which genetic variations at this locus could influence asthma susceptibility.

Atopy in Kashmir-validation from a case control study with respect to IgE and Interleukin genes

OBJECTIVES

Increased levels of serum Immunoglobulin-E (IgE) and different genetic variants of cytokines are common biochemical manifestation in Allergy. The current study was aimed to study the association of IgE and different variants of Interleukin-4 (IL-4), and Interleukin-13 (IL-13) genes with different kind of allergies.

METHODS

A pre-tested questionnaire was used to collect all the dietary, life style and clinical details by a trained staff. A blood sample of 2 ml each was collected in coagulated and anti-coagulated vials. DNA and serum samples were extracted and stored until further use. Serum IgE were estimated by ELISA while as the genotypic analysis was done by PCR-RFLP methods.

RESULTS

Statistically a significant difference of serum IgE levels were observed among cases and controls (P < 0.05). The observed significant difference of serum IgE levels were retained among subjects who also harboured variant genotypes of IL-4 and IL-13 genes (P < 0.05). Additionally, the above genetic variants significantly modified the risk of allergy when stratification was done based on various clinical characteristics.

CONCLUSION

Our study suggests that increased IgE levels and in association with variant forms of IL-4 and IL-13 genes are significantly associated with different types of allergies in study population.

Interleukin 4 and Interleukin 4 receptor alpha gene variants and risk of atopy - A case control study based assessment

INTRODUCTION

IL4 pathway is known to upregulate IgE mediated immune responses and responsible for the manifestation of Atopic disorders. The current study was aimed to elucidate the genetic variations of Interleukin 4 (IL4) and Interleukin 4 receptor alpha (IL4R) genes and their possible association with atopic subjects.

METHODS

The well-designed questionnaire was used to collect the subject demographic and clinical details. Biochemical parameters were analysed using Chemiluminescent Immunoassay (CLIA) technique. The genotyping was performed using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP).

RESULTS

We observed a statistically significant difference of serum Immunoglobulin-E (IgE) levels among cases and controls (P<0.05). Subjects harbouring the variant genotypes of I50V and Q576R single nucleotide polymorphisms (SNPs) in IL4R gene showed statistically differential risk towards atopic disorders. However, the variants genotype of 70 bp VNTR polymorphism in IL4 gene showed a protective role towards in predisposition to Atopy. On stratification, the above genetic variants had a significant impact on modifiable and non-modifiable factors associated with the disease.

CONCLUSION

Our study demonstrates that increased IgE levels and IL4 gene variants (I50V and Q576R) are significantly associated towards predisposition to allergic disorders in this study population.

IL-13 and FOXO3 genes polymorphisms regulate IgE levels in asthmatic patients

Immunoglobulin E (IgE) serves a crucial role in the pathogenesis of several allergic disorders, and elevated levels of total serum IgE have been associated with asthma. IgE is responsible for the release of several asthma-associated inflammatory mediators from mast cells, such as histamine and prostaglandins. The aim of the present study was to assess the association of interleukin (IL)-13 single nucleotide polymorphism (SNP) rs20541 and forkhead box O3a (FOXO3a) SNP rs13217795 with IgE levels in asthmatic patients and a healthy control group. Genetic polymorphism analysis of SNPs was performed using PCR/restriction fragment length polymorphism. Total serum IgE levels were measured using an ELISA kit. Genotypes were grouped into three models: Co-dominant, dominant and recessive. Major and minor alleles for IL-13 SNP rs20541 and FOXO3a SNP rs13217795 were C and T, whereas for IL-13, they were G and A, respectively. There was a significant association between the IL-13 rs20541 SNP and the total IgE serum levels, in which pure minor alleles were associated with a significant reduction (~5x lower) in IgE serum levels compared with the major alleles in asthmatic subjects and to a lesser extent in the control subjects. Additionally, the FOXO3a rs13217795 SNP was associated with a significant increase in total IgE levels (~5x higher) in the asthmatic patients compared with the control subjects. In conclusion, the present study confirmed that there was a significant association between the IL-13 SNP rs20541 and asthma, and an association between the FOXO3a SNP rs13217795 with asthma pathogenicity in Jordanian subjects.

Role of IL13 genetic polymorphism in the development of bronchial asthma in children

Bronchial asthma is a multifactorial disease, with both environmental factors and genetic predisposal affecting its development. A number of gene associations have been obtained between polymorphisms of cytokine genes produced by different types of immune cells and asthma development. Interleukin-13 is involved in allergic inflammation, increased bronchial hypersensitivity, regulation of eosinophil levels and IgE production by B cells, thus making it promising for studying IL13 gene polymorphisms in bronchial asthma coupled to development of the disease. The aim of this study was to investigate possible association between asthma and IL13 rs1800925 polymorphism in the children of Caucasian origin in Eastern Siberia. Four groups of patients with asthma were examined (mean age 12.8±1.2 years): with a controlled (n = 95) and uncontrolled course (n = 107), with severe (n = 71) and moderate severity (n = 131) diseases. The control group consisted of healthy individuals: children (n = 33) and adults (n = 102). DNA was isolated with sorbent method; genotyping was carried out using RT-PCR using specific oligonucleotide primers and fluorescent TaqMan probes. The allele and genotype frequencies were compared by the χ-square test using an online calculator. The odds ratio (OR) with a 95% confidence interval (CI) was performed to link genetic markers with pathological phenotypes. The CT IL13 rs1800925 genotype was shown to be associated with moderate asthma and cases of uncontrollable clinical course, whereas the TT genotype was associated with severe asthma. Thus, rs1800925 polymorphism of IL13 gene (the T* variant is known to be associated with increased IL-13 expression) may be associated with bronchial asthma in children. Our data are consistent with results of other authors. E.g., Liu Z. et al. revealed an association between rs1800925 IL13 and the risk of developing asthma in children, with CT and TT genotypes being more common in the patient group. Radhakrishnan A. et al., was studied rs1800925 IL13 in adult population of Malaysia and found that the T* allele frequency in the group of patients significantly exceeds the frequency of this allele in the control group. Thus, the results of our study showed that IL13 rs1800925 polymorphism is associated with bronchial asthma in children, especially, with level of its control and severity of the disease.

Identification of Novel Biomarkers for Drug Hypersensitivity After Sequencing of the Promoter Area in 16 Genes of the Vitamin D Pathway and the High-Affinity IgE Receptor

The prevalence of allergic diseases and drug hypersensitivity reactions (DHRs) during recent years is increasing. Both, allergic diseases and DHRs seem to be related to an interplay between environmental factors and genetic susceptibility. In recent years, a large effort in the elucidation of the genetic mechanisms involved in these disorders has been made, mostly based on case-control studies, and typically focusing on isolated SNPs. These studies provide a limited amount of information, which now can be greatly expanded by the complete coverage that Next Generation Sequencing techniques offer. In this study, we analyzed the promoters of sixteen genes related to the Vitamin D pathway and the high-affinity IgE receptor, including FCER1A, MS4A2, FCER1G, VDR, GC, CYP2R1, CYP27A1, CYP27B1, CYP24A1, RXRA, RXRB, RXRG, IL4, IL4R, IL13, and IL13RA1. The study group was composed of patients with allergic rhinitis plus asthma (AR+A), patients with hypersensitivity to beta-lactams (BLs), to NSAIDs including selective hypersensitivity (SH) and cross-reactivity (CR), and healthy controls without antecedents of atopy or adverse drug reactions. We identified 148 gene variations, 43 of which were novel. Multinomial analyses revealed that three SNPs corresponding to the genes FCER1G (rs36233990 and rs2070901), and GC (rs3733359), displayed significant associations and, therefore, were selected for a combined dataset study in a cohort of 2,476 individuals. The strongest association was found with the promoter FCER1G rs36233990 SNP that alters a transcription factor binding site. This SNP was over-represented among AR+A patients and among patients with IgE-mediated diseases, as compared with control individuals or with the rest of patients in this study. Classification models based on the above-mentioned SNPs were able to predict correct clinical group allocations in patients with DHRs, and patients with IgE-mediated DHRs. Our findings reveal gene promoter SNPs that are significant predictors of drug hypersensitivity, thus reinforcing the hypothesis of a genetic predisposition for these diseases.

Mechanisms of gastrointestinal allergic disorders

Gastrointestinal (GI) allergic disease is an umbrella term used to describe a variety of adverse, food antigen-driven, immune-mediated diseases. Although these diseases vary mechanistically, common elements include a breakdown of immunologic tolerance, a biased type 2 immune response, and an impaired mucosal barrier. These pathways are influenced by diverse factors such as diet, infections, exposure to antibiotics and chemicals, GI microbiome composition, and genetic and epigenetic elements. Early childhood has emerged as a critical period when these factors have a dramatic impact on shaping the immune system and therefore triggering or protecting against the onset of GI allergic diseases. In this Review, we will discuss the latest findings on the molecular and cellular mechanisms that govern GI allergic diseases and how these findings have set the stage for emerging preventative and treatment strategies.

Genetic polymorphisms of Th2 interleukins, history of asthma or eczema and childhood acute lymphoid leukaemia: Findings from the ESCALE study (SFCE)

BACKGROUND

Previous studies on the putative role of allergy in the aetiology of childhood leukaemia have reported contradictory results. The present study aimed to analyse the relation between a medical history of asthma or eczema and childhood acute lymphoid leukaemia (ALL) in light of potential candidate gene-environment interactions.

METHODS

Analyses were based on a subset of 434 cases of ALL and 442 controls successfully genotyped and of European ancestry children enrolled in a French population-based case-control study conducted in 2003-2004. Information about medical history was obtained during a standardized interview with the mothers. Candidate polymorphisms in genes of the Th2 cytokines IL4, IL10, IL13 and IL4-receptor, were genotyped or imputed.

RESULTS

None of the variant alleles were directly associated with childhood acute lymphoid leukaemia. A medical history of asthma or eczema was reported more often in the control group (OR = 0.7 [0.5-1.0]). This association was mostly seen in the group of children not carrying the IL13-rs20541 variant allele (Interaction Odds Ratio IOR 1.9, p-interaction = 0.07) and in those carrying the IL10 triple variant haplotype (IOR 0.5, p-interaction = 0.04). No interaction was observed with the candidate polymorphisms in IL4 and IL4R.

CONCLUSION

This study provides a new insight into the relationship between allergic symptoms and childhood acute lymphoid leukaemia, by suggesting this inverse association could be limited to children carrying certain genetic polymorphisms. If confirmed, these results could help better understand the biological mechanisms involved in the development of childhood acute lymphoid leukaemia.

Associations of TAP1 genetic polymorphisms with atopic diseases: asthma, rhinitis and dermatitis

Controversial findings have been reported regarding to the effect of the transporter associated with antigen processing 1 (TAP1) polymorphisms exerted on the atopic diseases susceptibility. To gain a better understanding of the effects of TAP1 polymorphisms on the risk of atopic diseases, a retrospective study was carried out to evaluate the association of the most common TAP1 polymorphisms, rs1057141 and rs1135216, with the risk of atopic diseases. From studies published in PubMed, Embase, and Web of Science up to July 2017, ten eligible studies were selected for meta-analysis. The pooled results from rs1135216 polymorphism showed increased risk of atopic diseases in homozygote and recessive comparison. From the subgroup analysis by ethnicity, it was found that rs1135216 polymorphism contributed to atopic diseases susceptibility among Africans in all the five genetic models. Subgroup analysis by atopic types indicated significant association of TAP1 polymorphism rs1135216 with asthma in the allele, dominant and recessive models and with allergic rhinitis in the recessive model. As to rs1057141, increased risk of atopic disease in the allelic, dominant and heterozygous model was found in African population. Overall, this meta-analysis study demonstrated that rs1135216 polymorphism may contribute to atopic diseases susceptibility in Asians and Africans as assessed in this study. However, well designed large-scale case-control studies are needed to confirm such preliminary findings.

Association of IL-13 rs20541 and rs1295686 variants with symptomatic asthma in a Saudi Arabian population

OBJECTIVE

Interleukin 13 (IL-13) plays a critical pro-inflammatory role in asthma. Several single nucleotide polymorphisms (SNPs) are associated with asthma susceptibility in specific populations; however, further replicative studies in other ethnic groups are mandatory.

METHODS

The association between IL-13 SNPs rs762534, rs20541, rs1295686, and rs1800925 (risk alleles A, A, T, and A, respectively) and asthma predisposition in a Saudi Arabian cohort was examined via a case-control cross-sectional study.

RESULTS

The frequencies of alleles between asthmatics and control populations were significantly different for rs20541 and rs1295686 SNPs (p < 0.001), whereas the frequencies of genotypes between asthmatics and controls were significantly different only for rs20541. The association of the risk (minor) alleles with asthma was examined using the dominant genetic model. Individuals with at least one copy of the risk alleles A (for rs20541) and T (for rs1295686) had significantly greater odds of being asthmatic (OR = 2.13, 95% CI = 1.39-3.26, p < 0.0001; OR = 1.69, 95% CI = 1.12-2.54, p = 0.008) relative to their most common homozygous genotypes. On the other hand, the minor A alleles for rs762534 and rs1800925 were not significantly associated with asthma risk. Regarding haplotype association analysis, individuals with at least one copy of the minor "risk" allele for both rs20541 and rs1295686 (CATG and CATA, respectively) had greater odds of being asthmatic relative to CGCG haplotype; however, this trend was not statistically significant (p > 0.3).

CONCLUSIONS

IL-13 minor T and A alleles for rs1295686 and rs20541, respectively, were associated with significantly higher risk of asthma in the Saudi Arabian population.

Role of IL-13 Genetic Variants in Signalling of Asthma

Asthma is a chronic inflammatory disease of the lower airways characterised by intermittent airway narrowing and airflow obstruction. The aim of this study was to examine the association of IL-13 Arg 130 Gln (A/G) and -1112C/T cytokine gene polymorphisms and to know the secretion of IL-13 cytokine levels and the interactions between the IL-13 130A/G and IL-13Rα1/IL-4Rα complex cytokine genes. The study population comprised of atopic and non-atopic asthma patients and healthy controls (HC) (N = 120). Single nucleotide polymorphisms (SNPs) were determined by restriction fragment length polymorphism (RFLP). IL-13 cytokine serum levels were measured by enzyme-linked immunosorbent assay (ELISA), and homology modelling of IL-13 A/G cytokine gene was performed through in silico analysis. In IL-13 130A/G cytokine gene AG, GG genotypes (p < 0.0042, OR = 2.87, CI 1.46-5.65; OR = 1.92, CI 1.06-3.48) were found to be significant in atopic asthma patients vs HC. The mean IL-13 serum cytokine levels were found to be significantly high in atopic (38.48 ± 36.54) and non-atopic (36.05 ± 34.54) asthma patients whereas total serum IgE levels were significantly high at p < 0.0001 in atopic and low in non-atopic asthma patients at p < 0.003 compared to HC. In silico analysis indicated that residue IL-13 130 with charge modifying variants was crucial in ligand-receptor interactions. IL-13 cytokine serum levels were significantly high in atopic and non-atopic asthma patients compared to HC. The GG genotype of IL-13 130A/G cytokine gene might be involved in the induced production of total IgE and IL-13 cytokine serum levels suggesting IL-13 may be important in the signalling of asthma.

Association between IL-13 +1923C/T polymorphism and asthma risk: a meta-analysis based on 26 case-control studies

Asthma is a serious and hereditary respiratory disorder affecting all age groups. Interleukin-13 (IL-13) is a central regulator of allergic inflammation. The purpose of the present study was to estimate the relationship between IL-13 +1923C/T polymorphism and asthma susceptibility. Relevant case-control studies published between January 2000 and July 2016 were searched in the online databases. Review Manage (RevMan) 5.3 was used to conduct the statistical analysis. The pooled odds ratio (OR) with its 95% confidence interval (CI) was employed to calculate the strength of association. A total of 26 articles were retrieved, including 17642 asthma patients and 42402 controls. Overall, our results found that IL-13 +1923C/T polymorphism was significantly associated with increased risk of asthma under each genetic model (P<0.00001). Subgroup analysis by ethnicity showed that alleles and genotypes of this variant correlated with asthma among Asians and Caucasians, but only TT genotype under the homozygote model in Africans. When stratified by age group, this variant highly correlated with asthma in children and moderately in adults. Furthermore, the TT, CT and CC genotypes in asthma group were all significantly associated with increased IgE levels in sera of asthma patients when compared with controls. Our results suggested that IL-13 +1923C/T polymorphism contributed to the development of asthma. Further case-control studies with more ethnicities are still needed.

Structural Characterisation Reveals Mechanism of IL-13-Neutralising Monoclonal Antibody Tralokinumab as Inhibition of Binding to IL-13Rα1 and IL-13Rα2

Interleukin (IL)-13 is a pleiotropic T helper type 2 cytokine frequently associated with asthma and atopic dermatitis. IL-13-mediated signalling is initiated by binding to IL-13Rα1, which then recruits IL-4Rα to form a heterodimeric receptor complex. IL-13 also binds to IL-13Rα2, considered as either a decoy or a key mediator of fibrosis. IL-13-neutralising antibodies act by preventing IL-13 binding to IL-13Rα1, IL-4Rα and/or IL-13Rα2. Tralokinumab (CAT-354) is an IL-13-neutralising human IgG4 monoclonal antibody that has shown clinical benefit in patients with asthma. To decipher how tralokinumab inhibits the effects of IL-13, we determined the structure of tralokinumab Fab in complex with human IL-13 to 2 Å resolution. The structure analysis reveals that tralokinumab prevents IL-13 from binding to both IL-13Rα1 and IL-13Rα2. This is supported by biochemical ligand-receptor interaction assay data. The tralokinumab epitope is mainly composed of residues in helices D and A of IL-13. It is mostly light chain complementarity-determining regions that are driving paratope interactions; the variable light complementarity-determining region 2 plays a key role by providing residue contacts for a network of hydrogen bonds and a salt bridge in the core of binding. The key residues within the paratope contributing to binding were identified as Asp50, Asp51, Ser30 and Lys31. This study demonstrates that tralokinumab prevents the IL-13 pharmacodynamic effect by binding to IL-13 helices A and D, thus preventing IL-13 from interacting with IL-13Rα1 and IL-13Rα2.

The role of polymorphism of interleukin-2, -10, -13 and TNF-α genes in cutaneous T-cell lymphoma pathogenesis

INTRODUCTION

As the pathogenesis of cutaneous T-cell lymphomas (CTCL) is not fully understood, inherited gene polymorphisms are considered to play a role in the development of lymphomas.

AIM

To investigate whether certain gene polymorphisms might be involved in the development of CTCL.

MATERIAL AND METHODS

In the case-control study we compared the frequency of nine selected single nucleotide polymorphisms (SNP) of seven genes (rs1800587/-889 C/T of interleukin (IL)-1α, rs2069762/-330G/T) and rs2069763/+166G/T of IL-2, rs1800925/-1112 C/T of IL-13, rs1800896/-1082 A/G of IL-10, rs4073/-251 A/T of IL-8, rs5370/K198N, rs180054/-1370T/G of endothelin-1 and rs1800629/-308 G/A of TNF-α) in 43 CTCL and Polish cases using the amplification refractory mutation system polymerase chain reaction method.

RESULTS

We have found that two genotypes, -330GG of IL-2 and -1112TT of IL-13 both promoter variants associated with "hypertranscription phenotype", were over-represented in CTCL patients compared to healthy controls, and they increase the risk of malignancy development (OR = 5.82, p = 0.001 for IL-2 -330 GG, and OR = 5.67, p = 0.0024 for IL-13 -1112 TT). On the other hand, high transcription -308A allele of the TNF-α gene and -1082GG of IL-10 genotype is less frequent in lymphoma patients and has protective effects on the development of CTCL (OR = 0.45, p = 0.0466 for -308A of TNF-α, and OR = 0.35, p = 0.0329 for -1082GG of IL-10 genes).

CONCLUSIONS

Our results indicate that hypertranscription promoter variants of IL-2 and IL-13 genes could be estimated as the risk factor for development of CTCL, while TNF-α and IL-10 variants have a protective effect.

Genetic susceptibility to allergic bronchopulmonary aspergillosis in asthma: a genetic association study

BACKGROUND

In patients with asthma, the fungus Aspergillus fumigatus can cause allergic bronchopulmonary aspergillosis (ABPA). Familial ABPA is reported, and some genetic factors have been associated with the disease, however, these are small studies (n ≤ 38) and do not explain all cases of ABPA.

METHODS

We analysed SNPs in 95 ABPA patients, comparing frequencies to 152 atopic asthmatic and 279 healthy controls. Twenty two genes were selected from literature, and 195 tagging SNPs were analysed for genetic association with ABPA using logistic regression corrected for multiple testing. We also analysed monocyte-derived macrophage gene expression before and during co-culture with A. fumigatus.

RESULTS

Seventeen ABPA-associated SNPs (ABPA v Atopic asthma) were identified. Three remained significant after correction for multiple testing; IL13 rs20541, IL4R rs3024656, TLR3 rs1879026. We also identified minor differences in macrophage gene expression responses in the ABPA group compared to the control groups.

CONCLUSIONS

Multiple SNPs are now associated with ABPA. Some are novel associations. These associations implicate cytokine pathways and receptors in the aberrant response to A. fumigatus and susceptibility to ABPA, providing insights into the pathogenesis of ABPA and/or its complications. We hope these results will lead to increased understanding and improved treatment and diagnostics for ABPA.

Shared genetic variants between serum levels of high-density lipoprotein cholesterol and wheezing in a cohort of children from Cyprus

Background

In a cohort of children in Cyprus, we recently reported low levels of high density lipoprotein cholesterol (HDL-C) to be associated with asthma. We examined whether genetic polymorphisms that were previously linked individually to asthma, obesity, or HDL-C are associated with both asthma and HDL-C levels in the Cyprus cohort.

Methods

We assessed genotypes frequencies in current-wheezers (n = 190) and non-asthmatic controls (n = 671) and HDL-C levels across several genotypes. Binary logistic regression models were used to assess the effect of genotypes on wheezing risk and examined whether this effect is carried out through changes of HDL–C.

Results

Of the 16 polymorphisms tested, two polymorphisms TNFa rs3093664 and PRKCA rs9892651 presented significant differences in genotype distribution among current-wheezers and controls. Higher HDL-C levels were noted in carriers of genotype GG of polymorphism TNFa rs3093664 that was protective for wheezing Vs AG and AA genotypes (65.3 Vs 51.8 and 53.3 mg/dl, p-value < 0.001 and p-value for trend = 0.028). In polymorphism PRKCA rs9892651, HDL-C levels were lower in carriers of CC and TC genotypes that were more frequent in current-wheezers Vs TT genotype (52.2 and 52.7 Vs 55.2 mg/dl, p-value = 0.042 and p-value for trend = 0.02). The association of TNFa rs3093664 with wheezing is partly mediated by its effect on HDL-C whereas association of PRKCA rs9892651 with wheezing appeared to be independent of HDL-C.

Conclusions

We found evidence that two SNPs located in different genetic loci, are associated with both wheezing and HDL-C levels, although more studies in other populations are needed to confirm our results.

Electronic supplementary material

The online version of this article (doi:10.1186/s13052-016-0276-1) contains supplementary material, which is available to authorized users.

An Interleukin 13 Polymorphism Is Associated with Symptom Severity in Adult Subjects with Ever Asthma

Different genes are associated with categorical classifications of asthma severity. However, continuous outcomes should be used to catch the heterogeneity of asthma phenotypes and to increase the power in association studies. Accordingly, the aim of this study was to evaluate the association between single nucleotide polymorphisms (SNPs) in candidate gene regions and continuous measures of asthma severity, in adult patients from the general population. In the Gene Environment Interactions in Respiratory Diseases (GEIRD) study (www.geird.org), 326 subjects (aged 20–64) with ever asthma were identified from the general population in Verona (Italy) between 2007 and 2010. A panel of 236 SNPs tagging 51 candidate gene regions (including one or more genes) was analysed. A symptom and treatment score (STS) and pre-bronchodilator FEV₁% predicted were used as continuous measures of asthma severity. The association of each SNP with STS and FEV₁% predicted was tested by fitting quasi-gamma and linear regression models, respectively, with gender, body mass index and smoking habits as potential confounders. The Simes multiple-test procedure was used for controlling the false discovery rate (FDR). SNP rs848 in the IL13 gene region (IL5/RAD50/IL13/IL4) was associated with STS (TG/GG vs TT genotype: uncorrected p-value = 0.00006, FDR-corrected p-value = 0.04), whereas rs20541 in the same gene region, in linkage disequilibrium with rs848 (r² = 0.94) in our sample, did not reach the statistical significance after adjusting for multiple testing (TC/CC vs TT: uncorrected p-value = 0.0003, FDR-corrected p-value = 0.09). Polymorphisms in other gene regions showed a non-significant moderate association with STS (IL12B, TNS1) or lung function (SERPINE2, GATA3, IL5, NPNT, FAM13A) only. After adjusting for multiple testing and potential confounders, SNP rs848 in the IL13 gene region is significantly associated with a continuous measure of symptom severity in adult subjects with ever asthma.

Polymorphisms in the interleukin 4, interleukin 4 receptor and interleukin 13 genes and allergic phenotype: A case control study

PURPOSE

Interleukin 4 (IL4), interleukin 4 receptor (IL4R) and interleukin 13 (IL13) play a key role in the pathogenesis of allergy and asthma development. IL4 and IL13 strongly influence bronchial hyperreactivity in response to allergen, airway remodeling, airway inflammation and airway smooth muscle proliferation. Both IL4 and IL13 exert biologic effect via interleukin 4 receptor. The aim of this study was to evaluate the impact of the polymorphisms within interleukin 4 (rs2243250, rs2227284), interleukin 4 receptor α chain (rs1805010, rs1805011) and interleukin 13 (rs20541) genes on the incidence of allergic phenotype in Polish pediatric population.

MATERIAL/METHODS

We compared 177 asthmatic pediatric patients with 194 healthy children. Five polymorphisms within IL4, IL13 and IL4Rα genes were analyzed. Genotypes of four polymorphisms (rs2243250, rs2227284, rs1805011, rs20541) were assigned by TaqMan SNP Genotyping Assays (Applied Biosystems), whereas rs18050100 polymorphism was established using PCR-RFLP method.

RESULTS

We observed an association of rs1805011 polymorphism of IL4Rα gene with allergy (p=0.021), mild asthma (p=0.00005) and atopic dermatitis (p=0.0056). Significant correlation was found between rs20541 in IL-13 gene and the positive skin prick test results (p=0.029), along with rs2243250 polymorphism with clinical atopy (p=0.033) and rs2227284 with total IgE levels (p=0.00047). No associations were found for rs1805010.

CONCLUSIONS

Our results indicate that rs1805011 polymorphism of IL4Rα gene seems to influence allergy risk, especially mild asthma and atopic dermatitis predisposition in Polish children. Subgroup analysis of three other SNPs revealed possible influence on allergy development.

Association between polymorphism of the interleukin-13 gene and susceptibility to hepatocellular carcinoma in the Chinese population

Objective

Interleukin-13 (IL-13) is a potent pleiotropic cytokine that is produced by activated CD4 T cells. This study was undertaken to determine the relationship between two IL-13 gene single nucleotide polymorphisms (SNP rs1800925 and SNP rs20541) and the incidence of hepatitis B virus-related (HBV) hepatocellular carcinoma (HCC).

Method

Three hundred and ninety-eight HBV-positive individuals (192 HCC and 206 patients with chronic hepatitis) and one hundred and ninety-two healthy participants from the First Affiliated Hospital of Guangxi Medical University were enrolled in this study.

Results

The results showed no significant differences between the genotype and allele frequencies of the IL-13 gene rs1800925 and rs20541 polymorphisms and chronic hepatitis B risk after adjusting for age, sex, tobacco use, and alcohol intake using binary logistic regression analyses. Regarding the rs20541 SNP, the GA genotype was significantly related to a decreased risk of HCC after adjusting for age, sex, tobacco use, and alcohol intake using binary logistic regression analyses (The odds ratio (OR) = 0.54, 95% confidence intervals (CI) 0.34–0.87). The adjusted OR for the GA and AA genotypes combined was 0.68 (95% CI 0.39–0.90).

Conclusion

This study indicates that the functional IL-13 rs20541 polymorphism may contribute to the risk of HCC and that the rs20541 polymorphism is a protective factor for HCC.

Association of Single Nucleotide Polymorphisms in Toll-like Receptor Genes With Asthma Risk: A Systematic Review and Meta-analysis

Purpose

Asthma is a complex disease, with contributions from multiple genes, various genetic backgrounds, and environmental factors. Many human epidemiological studies have demonstrated that single nucleotide polymorphisms (SNPs) in Toll-like receptor (TLR) genes are inconsistently associated with asthma risk. Some have demonstrated differences concerning the study design and effect size, and conflicting results have been reported. A meta-analysis is necessary to determine the magnitude of this association.

Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, a systematic search and meta-analysis of the literature was conducted to estimate the association of SNPs in TLR genes with asthma risk. We screened the medical literature based on the following keyword searches in MEDLINE and EMBASE databases: 'TLR', 'polymorphism', 'asthma', and their combinations.

Results

Meta-analysis of eight studies on TLR4 Asp299Gly showed a marginal association of TLR4 with asthma risk (odds ratio [OR]=0.814 [95% confidence interval [CI], 0.652-1.016; P=0.069]) in the recessive model. TLR4 Thr399Ile was not associated with asthma risk under any genetic model. Meta-analysis of four studies on TLR2 Arg753Gln indicated that TLR2 might be significantly associated with asthma in the dominant and codominant models (P=0.029, P=0.030, and P=0.009, respectively). TLR9 -1237 was marginally associated with asthma risk (OR=0.408 [95% CI, 0.163-1.021; P=0.065]) in the codominant model. Analysis using the allele contrast model showed that the major TLR9 -1237 T allele tended to be a significant protective factor with OR=0.689 (95% CI, 0.471-1.007; P=0.055).

Conclusions

The results showed that TLR4 Asp299Gly, TLR2 Arg753Gln, and TLR9-1237 might contribute significantly to asthma susceptibility. Future genetic association studies would consolidate these findings.

Genetic polymorphisms and asthma: findings from a case-control study in the Madeira island population

BACKGROUND

Asthma is a complex disease influenced by multiple genetic and environmental factors. While Madeira has the highest prevalence of asthma in Portugal (14.6%), the effect of both genetic and environmental factors in this population has never been assessed. We categorized 98 asthma patients according to the Global Initiative for Asthma (GINA) guidelines, established their sensitization profile, and measured their forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) indexes. Selected single nucleotide polymorphisms (SNPs) were analysed as potential markers for asthma susceptibility and severity in the interleukin 4 (IL4), interleukin 13 (IL13), beta-2-adrenergic receptor (ADRB2), a disintegrin and metalloprotease 33 (ADAM33), gasdermin-like (GSDML) and the signal transducer and activator of transcription 6 (STAT6) genes comparatively to a population reference set.

RESULTS

Although mites are the major source of allergic sensitization, no significant difference was found amongst asthma severity categories. IL4-590*CT/TT and IL4-RP2*253183/183183 were found to predict the risk (2-fold) and severity (3 to 4-fold) of asthma and were associated with a lower FEV1 index. ADRB2-c.16*AG is a risk factor (3.5-fold), while genotype GSDML-236*TT was protective (4-fold) for moderate-severe asthma. ADAM33-V4*C was associated to asthma and mild asthma by the transmission disequilibrium test (TDT). Finally, ADAM33-V4*CC and STAT6-21*TT were associated with higher sensitization (mean wheal size ≥10 mm) to house dust (1.4-fold) and storage mite (7.8-fold).

CONCLUSION

In Madeira, IL4-590C/T, IL4-RP2 253/183, GSDML-236C/T and ADAM33-V4C/G SNPs are important risk factors for asthma susceptibility and severity, with implications for asthma healthcare management.

PPAR-γ inhibits IL-13-induced collagen production in mouse airway fibroblasts

Interleukin-13 (IL-13) plays an important role in extracellular matrix production of airway remodeling in asthma. Activation of PPAR-γ has been shown to inhibit the occurrence of airway fibrosis in asthma, yet it remains unknown whether the effect of PPAR-γ on suppression of airway fibrosis is associated with the inhibition of IL-13 signaling. In the present study, primary cultured airway fibroblasts were stimulated with IL-13, and JAK inhibitor, PDGF receptor blocker and MEK inhibitor were applied to investigate the involvement of these pathways in IL-13-induced collagen production. Our results demonstrate that IL-13 dose- and time-dependently induced collagen production in primary cultured mouse airway fibroblasts; this effect was blocked by inhibition of JAK/STAT6 signal pathway. IL-13 also stimulated JAK/STAT6-dependent PDGF production, elevation of PDGF in turn activated ERK1/2 MAPK and caused collagen production. Activation of PPAR-γ by rosiglitazone reduced IL-13-induced collagen expression by suppression of STAT6-driven PDGF production. Our results indicate that activation of JAK/STAT6 signal and subsequent PDGF generation and ERK1/2 MAPK activation mediate IL-13-induced collagen production in airway fibroblasts. This study suggests that activation of PPAR-γ might be a novel strategy for the treatment of asthma partially by inhibition of airway fibrosis.

Interaction of prenatal maternal smoking, interleukin 13 genetic variants and DNA methylation influencing airflow and airway reactivity

BACKGROUND

Asthma is characterized by airflow limitation and airway reactivity (AR). Interleukin-13 (IL-13) is involved in the pathogenesis of asthma. Two functional SNPs, rs20541 and rs1800925, of the IL-13 gene (IL13) have been frequently associated with asthma-related lung functions. However, genetic variation alone does not fully explain asthma risk. DNA-methylation (DNA-M) is an epigenetic mechanism that regulates gene expression and can be influenced by both environment and genetic variants. To explore the interplay of prenatal maternal smoking, genetic variants and DNA-M, we used a two-stage model: (1) identifying cytosine phosphate guanine (CpG) sites where DNA-M is influenced by the interaction between genetic variants and maternal smoking during pregnancy (conditional methQTL (methylation quantitative trait loci)); and (2) determining the effect of the interaction between DNA-M of CpG (from stage 1) and SNPs (modifying genetic variants; modGV) on airflow limitation and AR in 245 female participants of the Isle of Wight birth cohort. DNA-M was assessed using the Illumina Infinium HumanMethylation450 BeadChip.

FINDINGS

Six CpG sites were analyzed in stage 1. DNA-M at cg13566430 was influenced by interaction of maternal smoking during pregnancy and rs20541. In stage 2, genotype at rs1800925 interacted with DNA-M at cg13566430 significantly affecting airflow limitation (P = 0.042) and AR (P = 0.01).

CONCLUSION

Both genetic variants and environment affect DNA-M. This study supports the proposed two-stage model (methQTL and modGV) to study genetic variants, environment and DNA-M interactions in asthma-related lung function.

Association of IL-4-590 C>T and IL-13-1112 C>T gene polymorphisms with the susceptibility to type 2 diabetes mellitus

Background. The goal of the study is to investigate the association of IL-4-590 and IL-13-1112 genetic polymorphisms with type 2 diabetes mellitus (T2DM) in Egyptian patients. Subjects and Methods. The study included 135 cases with T2DM and 75 healthy unrelated age-matched controls from the same locality of Egypt. DNA was extracted and processed by the ARMS-PCR technique for characterization of genetic variants of IL-4-590 C>T and IL-13-1112 C>T polymorphisms. Results. Egyptian cases with T2DM showed a lower frequency of the IL-4-590 CC homozygous genotype compared to controls (10.4% versus 43.48%) with a higher CT heterozygous genotype (85.2% versus 47.8%). Similarly, cases showed a lower frequency of the IL-13-1112 CC genotype (20.7% versus 56.8%) with a higher frequency of the heterozygous IL-13-1112 CT genotype (76.3% versus 41.3%). Both polymorphisms showed significantly positive associations with T2DM in the dominant, codominant, and overdominant models of inheritance. On the other hand, comparing genotypes of subgroups related to gender, positive family history, and positive consanguinity showed a nonsignificant difference (P > 0.05). Conclusion. Heterozygous genotypes (IL-4-590 CT and IL-13-1112 CT) could be considered as risk factors, while the homozygous wild types (-590 CC and -1112 CC) might be considered protective to T2DM.

Interleukin-13 +1923C/T polymorphism is associated with asthma risk: a meta-analysis

There are controversies on the association between interleukin-13 (IL-13) +1923C/T polymorphism (rs1295686) and the risk of asthma. We performed this study to assess the association by the method of meta-analysis. A systematic search current to October 16, 2012, was conducted using PubMed, EMBASE, and China National Knowledge Infrastructure (CNKI) and identified ten studies comprising 13698 cases and 38209 controls. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. There was a significant association between IL-13 +1923C/T polymorphism and asthma risk in codominant model. When stratified by ethnicity, IL-13 +1923C/T polymorphism remained significantly associated with higher asthma risk in Asians and Caucasians. In the subgroup analysis by study quality, a significantly increased asthma risk was observed in high quality studies. Sensitivity analysis and cumulative analysis further strengthened the validity of the results. No publication bias was found in this meta-analysis. In conclusion, results from this meta-analysis suggested that IL-13 +1923C/T polymorphism was a risk factor of asthma.

Genetic association between selected cytokine genes and glioblastoma in the Han Chinese population

Background

Glioblastoma (GBM) is the most malignant brain tumor. Many abnormal secretion and expression of cytokines have been found in GBM, initially speculated that the occurrence of GBM may be involved in these abnormal secretion of cytokines. This study aims to detect the association of cytokine genes with GBM.

Methods

We selected seven tag single nucleotide polymorphisms (tSNPs) in six cytokine genes, which previously reported to be associated with brain tumors, and analyzed their association with GBM in a Han Chinese population using χ² test and genetic model analysis.

Results

We found two risk tSNPs and one protective tSNP. By χ² test, the rs1801275 in IL-4R showed an increased risk of GBM. In the genetic model analysis, the genotype “TC” of rs20541 in IL-13 gene showed an increased risk of GBM in over-dominant model (OR = 2.00; 95% CI, 1.13-3.54, p = 0.015); the genotype “CT” of rs1800871 in the IL-10 gene showed a decrease risk in the over-dominant model (OR = 0.57; 95% CI, 0.33 – 0.97; p = 0.037). The genotype “AG” of rs1801275 in the IL-4R gene showed an increase risk in over-dominant model (OR = 2.29; 95% CI, 1.20 - 4.35; p = 0.0081) We further analyzed whether the six cytokine genes have a different effect on the disease in gender specific population, and found that the allele “G” of rs2243248 in the IL-4 gene showed a decrease risk of GBM in female (OR = 0.35, 95% CI, 0.13 - 0.94, p = 0.0032), but the allele “T” showed a decrease risk in male (OR = 0.30, 95% CI, 0.17 - 0.53, p = 0.0032).

Conclusions

Our findings, combined with previously reported results, suggest that cytokine genes have potential role in GBM development, which may be useful to early prognostics for GBM in the Han Chinese population.

Effects of polymorphisms -1112C/T and +2044A/G in interleukin-13 gene on asthma risk: a meta-analysis

Background

Associations between interleukin-13 (IL-13) polymorphisms and asthma risk remained controversial and ambiguous. Therefore, we performed a meta-analysis to assess the associations between IL-13 polymorphisms and asthma susceptibility.

Methods

Pubmed, EMBASE, Chinese National Knowledge Infrastructure (CNKI) and Wangfang databases were searched. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to calculate the strength of association in the random-effects model.

Results

Thirty-four studies were included in this meta-analysis. The results indicated that IL13 -1112C/T polymorphism was significantly associated with asthma risk (OR = 1.20, 95% CI 1.08–1.34, P = 0.0009) in a dominant genetic model. When stratifying for race, IL13 -1112C/T polymorphism exhibited increased asthma risk in Caucasians (OR = 1.30, 95% CI 1.09–1.55, P = 0.003), while no significant association was found in Asians and African Americans. In the subgroup analysis based on atopic status, significant association was observed in atopic patients (OR = 1.25, 95% CI 1.07–1.45, P = 0.004) but not in the non-atopic patients. In addition, a significant association between IL13+2044A/G polymorphism and asthma risk was observed (OR = 1.18, 95% CI 1.08–1.28, P = 0.0002). In the subgroup analysis by ethnicity, there were significant associations between IL13+2044A/G polymorphism and asthma risk in Asians (OR = 1.19, 95% CI 1.04–1.36, P = 0.01) and Caucasians (OR = 1.22, 95% CI 1.06–1.40, P = 0.005) but not in African Americans. In the subgroup analysis stratified by atopic status, a marginal significant association was found in atopic patients (OR = 1.12, 95% CI 1.00–1.26, P = 0.05).

Conclusions

This meta-analysis suggested that the IL13 -1112C/T and +2044A/G polymorphisms were risk factors for asthma.

Association between polymorphisms in interleukin-4Rα and interleukin-13 and glioma risk: a meta-analysis

INTRODUCTION

It has been suggested that allergies are inversely associated with glioma risk. Single nucleotide polymorphisms in two allergy-related genes [interleukin (IL)-4Rα, IL-13] have been implicated in susceptibility to glioma; however, results from the published studies remained inconclusive.

METHODS

To derive a more precise relationship, we conducted a meta-analysis including seven case-control studies that investigated the influence of IL-4Rα rs1801275 and IL13 rs20541 polymorphisms on glioma risk. Data were extracted from these studies and pooled odds ratios (OR) with 95% confidence intervals (CI) were used to investigate the strength of the association.

RESULTS

Overall, the pooled analysis showed that there was no significant association between the IL-4Rα rs1801275 polymorphism and glioma risk (OR = 0.99, 95%CI: 0.79-1.25, AG/GG vs. AA). However, we found that the IL13 rs20541 variant genotypes (GA/AA) were significantly associated with reduced risk for glioma (OR = 0.85, 95%CI: 0.75-0.97, GA/AA vs. GG). In the stratified analyses by ethnicity, marginally significant association between the IL13 rs20541 polymorphism and decreased glioma risk was found among Asian populations in dominant models (OR = 0.84, 95%CI: 0.70-1.00, GA/AA vs. GG).

CONCLUSIONS

This meta-analysis suggests that the IL13 rs20541 but not the IL-4Rα rs1801275 polymorphism may be a genetic predictor for glioma. More studies with larger sample size are warranted to further elucidate the impact of the IL13 rs20541 polymorphism on glioma risk.

Association between IL13 gene polymorphisms and susceptibility to cancer: a meta-analysis

BACKGROUND/AIMS

Interleukin-13 (IL13) is an immunoregulatory cytokine which plays an important role in carcinogenesis through affecting tumor immunosurveillance. Many studies had reported the influence of IL13 rs1800925 and rs20541 polymorphisms on cancer risk, however, with inconclusive results. The aim of the present study was to conduct a meta-analysis to clarify the relationship.

METHODS

Twenty studies including a total of 6713 cancer cases and 8693 controls for IL13 rs20541 polymorphism and 4081 cancer cases and 6202 controls for IL13 rs1800925 polymorphism were included in the meta-analysis. Data were extracted from these studies and odds ratios with corresponding 95% confidence intervals were computed to estimate the strength of the association.

RESULTS

Overall, the IL13 rs20541 polymorphism were associated with significantly decreased cancer risk in all genetic models (AA vs. GG: OR=0.82, 95%CI=0.71-0.95; GA vs. GG: OR=0.92, 95%CI=0.85-0.99; GA/AA vs. GG: OR=0.90, 95%CI=0.85-0.97; AA vs. GG/GA: OR=0.85, 95CI%=0.74-0.98). In the stratified analyses, significant effects were found among European populations, studies with population-based controls and studies of glioma. No influence of the IL13 rs1800925 polymorphism on the overall cancer risk was observed. However, in the stratified analyses, we found the IL13 rs1800925 polymorphism was significantly associated with decreased risk for glioma (CT vs. TT: OR=0.72, 95%CI=0.55-0.93; CT/TT vs. TT: OR=0.76, 95%CI=0.62-0.89).

CONCLUSION

Our meta-analysis suggests that the IL13 rs20541 polymorphism contributes to susceptibility to cancer, especially for glioma; and the IL13 rs1800925 polymorphism may be associated with glioma risk.

Candidate human genetic polymorphisms and severe malaria in a Tanzanian population

Human genetic background strongly influences susceptibility to malaria infection and progression to severe disease and death. Classical genetic studies identified haemoglobinopathies and erythrocyte-associated polymorphisms, as protective against severe disease. High throughput genotyping by mass spectrometry allows multiple single nucleotide polymorphisms (SNPs) to be examined simultaneously. We compared the prevalence of 65 human SNP's, previously associated with altered risk of malaria, between Tanzanian children with and without severe malaria. Five hundred children, aged 1–10 years, with severe malaria were recruited from those admitted to hospital in Muheza, Tanzania and compared with matched controls. Genotyping was performed by Sequenom MassArray, and conventional PCR was used to detect deletions in the alpha-thalassaemia gene. SNPs in two X-linked genes were associated with altered risk of severe malaria in females but not in males: heterozygosity for one or other of two SNPs in the G6PD gene was associated with protection from all forms of severe disease whilst two SNPs in the gene encoding CD40L were associated with respiratory distress. A SNP in the adenyl cyclase 9 (ADCY9) gene was associated with protection from acidosis whilst a polymorphism in the IL-1α gene (IL1A) was associated with an increased risk of acidosis. SNPs in the genes encoding IL-13 and reticulon-3 (RTN3) were associated with increased risk of cerebral malaria. This study confirms previously known genetic associations with protection from severe malaria (HbS, G6PD). It identifies two X-linked genes associated with altered risk of severe malaria in females, identifies mutations in ADCY9, IL1A and CD40L as being associated with altered risk of severe respiratory distress and acidosis, both of which are characterised by high serum lactate levels, and also identifies novel genetic associations with severe malaria (TRIM5) and cerebral malaria(IL-13 and RTN3). Further studies are required to test the generality of these associations and to understand their functional consequences.