The CD14 C-159T polymorphism is not associated with asthma or asthma severity in an Australian adult population

Advances in asthma genetics

While asthma has a strong genetic component, our current ability to systematically understand and predict asthma risk remains low, despite over a hundred genetic associations. The reasons for this unfilled gap range from technical limitations of current approaches to fundamental deficiencies in the way we understand asthma. These are discussed in the context of genomic advances.

Inflammatory Markers and Genetic Polymorphisms in Workers Exposed to Flour Dust

OBJECTIVE

The aim of this study is to evaluate inflammatory markers and pro-inflammatory CD14 and Toll-like Receptor 4 (TLR4) polymorphisms in workers exposed to flour dust.

METHODS

Polymorphisms in TLR4 and CD14 were identified in our study population of 167 workers that included 63 healthy subjects (HS), 45 atopic subjects (A), and 59 subjects diagnosed clinically with occupational asthma/rhinitis (OAR). Endpoint measures in this study included fractional exhaled nitric oxide and serum concentrations of interleukin IL-6, IL-8, and tumor necrosis factor-alpha (TNF-α).

RESULTS

We identified a polymorphism in CD14 (rs2569190) that may be differentially expressed (P = 0.06). IL-6 concentrations in the serum were significantly higher in the A and OAR groups (P < 0.01) than in subjects in the HS group, while IL-8 concentrations were significantly elevated only in the OAR group (P < 0.01). Interestingly, TNF-α concentrations in the OAR group were significantly reduced when compared with subjects in the HS group (P < 0.01).

CONCLUSION

Cytokines are likely a defensive response in atopic and healthy workers. A protective genotype is hypothesized for occupational asthma.

Role of offending out-door aero-allergen and CD14 C(-159)T polymorphism in development and severity of asthma in a Kolkata patient population

Objective

Present study involved identification of offending out-door aero-allergens and associated genetic pathway in nasso-bronchial asthma among Kolkata population.

Methods

Skin-prick test was done among 950 asthmatic patients against 11 common aero-allergens and total serum IgE concentration was measured. PCR-RFLP was done in patients and non-asthmatic control (n=220 in each) to characterize functional polymorphism, C(-159)T, of CD14, a positional candidate gene for allergy. Association of genetic polymorphisms was made with clinico-pathological conditions.

Results

We identified Cocos nucifera as the most common aero-allergen sensitizer among atopic patients in Kolkata. Patients with childhood-onset asthma were significantly more sensitive towards aero-allergens and had significantly higher serum IgE level than those of adult-onset (p< 0.0001). No significant difference was found in distribution of SNP genotypes of CD14 among case and control (p=0.178). However among patients, frequency of C allele is significantly higher in childhood-onset group than that of adult-onset and concordantly in former CC genotype was associated with significant higher level of serum IgE than CT and TT.

Conclusion

In Kolkata, pollen is a common out-door aero-allergen and Cocos nucifera is predominant among pollens. Childhood-onset and adult-onset of asthma showed significant difference in allergen sensitivity as well as genetic background with respect to CD14 polymorphism.

Overview of systematic reviews in allergy epidemiology

BACKGROUND

There is a substantial body of evidence on the epidemiology of allergic conditions, which has advanced the understanding of these conditions. We aimed to systematically identify systematic reviews and meta-analyses on the epidemiology of allergic diseases to assess what has been studied comprehensively and what areas might benefit from further research.

METHODS

We searched PubMed and EMBASE up to 12/2014 for systematic reviews on epidemiological research on allergic diseases. We indexed diseases and topics covered and extracted data on the search characteristics of each systematic review.

RESULTS

The search resulted in 3991 entries after removing duplicates, plus 20 other items found via references and conference abstracts; 421 systematic reviews were relevant and included in this overview. The majority contained some evidence on asthma (72.9%). Allergic rhinitis, atopic eczema and food hypersensitivity were covered in 15.7%, 24.5% and 9.0%, respectively. Commonly studied risk factors for atopic eczema included dietary and microbial factors, while for asthma, pollution and genetic factors were often investigated in systematic reviews. There was some indication of differing search characteristics across topics.

CONCLUSION

We present a comprehensive overview with an indexed database of published systematic reviews in allergy epidemiology. We believe that this clarifies where most research interest has focussed and which areas could benefit from further research. We propose that this effort is updated every few years to include the most recently published evidence and to extend the search to an even broader list of hypersensitivity/allergic disorders.

No Association Between -159C/T Polymorphism of the CD14 Gene and Asthma Risk: a Meta-Analysis of 36 Case-Control Studies

Numerous studies have evaluated the association between -159C/T polymorphism of the CD14 gene and asthma risk; however, these studies have yielded inconsistent results. We performed meta-analyses to investigate the association between CD14-159C/T polymorphism and asthma risk. Studies were identified from PubMed, Embase, and two Chinese databases. Odds ratios (ORs) with 95 % confidence interval (CI) were used to evaluate the strength of association. Thirty-six studies were collected for meta-analysis, which involved 6954 cases and 7525 controls. In the overall populations, no significant association between the CD14-159C/T polymorphism and asthma risk was found for the dominant (OR = 0.90, 95 % CI = 0.81-1.01, P = 0.08) or other models; stratified analyses indicated that the CD14-159C/T polymorphism was not associated with asthma risk in Caucasians or Asians or adults or children. Among the atopic asthma populations, no significant results were observed in the all-combined or subgroup analyses. This meta-analysis demonstrates that the CD14-159C/T polymorphism may not be a risk factor for asthma.

Association of CD14 -159 (-260C/T) polymorphism and asthma risk: an updated genetic meta-analysis study

BACKGROUND

It has been reported that the cluster of differentiation 14 (CD14) gene -159C/T variant may be associated with asthma risk. However, some studies yielded conflicting results. Therefore, a comprehensive meta-analysis was designed to assess the precise association.

METHODS

A systematic search in PubMed, Embase (Ovid), China National Knowledge Internet (CNKI), and Wan fang databases was conducted up to August 15, 2015. Odds ratio (OR) and 95% confidence interval (CI) were used to pool the effect size. We used I to assess heterogeneity, and a funnel plot and Egger test to assess publication bias.

RESULTS

In total, 34 studies involving 15,641 subjects were included in this meta-analysis. There was a statistically significant association between CD14 -159C/T polymorphism and asthma risk observed in dominant model (TT+TC vs CC: OR = 0.86, 95% CI = 0.77-0.97, P = 0.012) and codominant model (TC vs CC: OR = 0.88, 95% CI = 0.78-0.99, P = 0.035) in adults. However, there may be no significant association between CD14 159C/T and atopic and nonatopic asthma risk.

CONCLUSION

In summary, the overall results suggested that the CD14 -159C/T variant may decrease the risk of asthma susceptibility in adults. However, no significant association between CD14 159C/T and atopic and nonatopic asthma susceptibility was identified. More studies with larger sample size are needed to validate the findings from this study.

Hesperidin inhibits inflammatory response induced by Aeromonas hydrophila infection and alters CD4+/CD8+ T cell ratio

Background. Aeromonas hydrophila is an opportunistic bacterial pathogen that is associated with a number of human diseases. Hesperidin (HES) has been reported to exert antioxidant and anti-inflammatory activities. Objectives. The aim of this study was to investigate the potential effect of HES treatment on inflammatory response induced by A. hydrophila infection in murine. Methods. A. hydrophila-infected mice were treated with HES at 250 mg/kg b.wt./week for 4 consecutive weeks. Phagocytosis, reactive oxygen species production, CD4⁺/CD8⁺ T cell ratio, and CD14 expression on intestinal infiltrating monocytes were evaluated. The expression of E-selectin and intercellular adhesion molecule 1 on stimulated HUVECs and RAW macrophage was evaluated. Results. Percentage of CD4⁺ T cells in the intestinal tissues of infected treated mice was highly significantly increased; however, phagocytic index, ROS production, CD8⁺ T cells percentage, and CD14 expression on monocytes were significantly reduced. On the other hand, HES significantly inhibited A-LPS- and A-ECP-induced E-selectin and ICAM-1 expression on HUVECs and ICAM-1 expression on RAW macrophage. Conclusion. Present data indicated that HES has a potential role in the suppression of inflammatory response induced by A. hydrophila toxins through downmodulation of ROS production and CD14 and adhesion molecules expression, as well as increase of CD4⁺/CD8⁺ cell ratio.

CD14 -159C/T polymorphism contributes to the susceptibility to tuberculosis: evidence from pooled 1,700 cases and 1,816 controls

CD14 is a receptor for lipopolysaccharide and plays an important role in innate immune against infections induced by microorganisms. A functional polymorphism in promoter region of CD14 gene, -159C/T, was extensively investigated with tuberculosis (TB) risk, but the association results were inconclusive. We performed a meta-analysis to synthesize association results of CD14 -159C/T polymorphism with TB risk from 8 studies including 1,700 TB cases and 1,816 controls. Based on the heterogeneity between studies evaluated by χ2-based Q test, a fixed- or random-effect model was applied to estimate the pooled odds ratio (OR) and 95% confidence interval (CI). Potential publication bias was evaluated with the funnel plot as well as the linear regression asymmetry test proposed by Egger et al. We found that the -159T allele was significantly associated with an increased risk of TB (OR 1.27, 95% CI 1.01-1.61) as compared with -159C allele. Individuals with -159TT genotype showed a significantly increased risk of TB than those with -159CT/CC genotype (OR 1.52, 95% CI 1.11-2.08). These associations were not attributed to potential publication bias (P>0.05 for Egger's test). The results from this meta-analysis indicate that CD14 -159C/T polymorphism is associated with TB predisposition and may serve as a candidate of susceptibility biomarker for TB.

Role of infections in the induction and development of asthma: genetic and inflammatory drivers

Genetic and environmental factors interact to initiate and even maintain the course of asthma. As one of the highly risky environmental factors, infections in predisposed individuals can promote asthma development and exacerbations and/or prolong symptoms. This review will describe our current understanding of the genetic markers of innate immunity in the induction and development of asthma, the diverse roles of infections in modulating allergic inflammation, host susceptibility to infections and subsequent acute exacerbations in an allergic setting, and the therapeutic or preventive implications of existing knowledge. Current challenges and future directions in basic and clinical research of asthma are also discussed.

CD14 tobacco gene-environment interaction in atopic children

Studying gene-environment interactions may elucidate the complex origins of atopic diseases. The aim of this study was to evaluate the association of CD14 polymorphisms and atopy in Egyptian children and to study whether atopy is influenced by CD14 interaction with tobacco smoke exposure. CD14 -159 C/T and CD14 -550 C/T were genotyped in 500 asthmaic children, 150 allergic rhinitis children and 150 controls. We found that CD14 -159T allele, CD14 -550T allele and CD14 -159T/-550T haplotype were significantly associated with atopic asthma and allergic rhinitis groups. CD14 -159 TT and CD14 -550 TT genotypes associated with elevated IgE levels in children exposed to tobacco smoke. The TT genotype of CD14 -159 C/T and CD14 -550 C/T was associated with higher serum levels of sCD14. The present study indicated that CD14 gene polymorphisms may contribute to susceptibility to atopy in Egyptian children and influenced with tobacco smoke exposure.

Racial differences in the association of CD14 polymorphisms with serum total IgE levels and allergen skin test reactivity

Background

The CD14 C-159T single nucleotide polymorphism (SNP) has been investigated widely as a candidate genetic locus in patients with allergic disease. There are conflicting results for the association of the CD14 C-159T SNP with total serum immunoglobulin E (IgE) levels and atopy. There are limited data regarding the association of the CD14 C-159T SNP in subjects of African ancestry. The aim of the study was to determine whether the C-159T SNP and other CD14 SNPs (C1188G, C1341T) were associated with total serum IgE levels and with allergy skin test results in nonatopic and atopic subjects; as well as in Caucasian and African American subjects.

Methods

A total of 291 participants, 18–40 years old, were screened to determine whether they were atopic and/or asthmatic. Analyses were performed to determine the association between CD14 C-159T, C1188G, or C1341T genotypes with serum IgE levels and with the number of positive skin tests among Caucasian or African American subjects.

Results

We found no significant association of serum total IgE level with CD14 C-159T, C1188G, or C1341T genotypes within nonatopic or atopic subjects. Subjects with CD14-159 T alleles had significantly more positive allergen skin tests than subjects without CD14-159 T alleles (P = 0.0388). There was a significant association between the CD14 1188 G allele, but not the CD14 1341 T allele, with the number of positive skin-test results in Caucasians, but not in African Americans.

Conclusion

These results support a possible association between CD14 polymorphisms and atopy. CD14-159 T or CD14 1188 G alleles were associated with atopic disease. For subjects with CD14 1188 G alleles, the association with atopic disease was stronger in Caucasians compared to African Americans.

Clinical application of human β-defensin and CD14 gene polymorphism in evaluating the status of chronic inflammation

Background

Periodontitis is a common disease that affects the periodontal tissue supporting the teeth. This disease is attributed to multiple risk factors, including diabetes, cigarette smoking, alcohol, pathogenic microorganisms, genetics and others. Human beta-defensin-1 (hBD-1) is a cationic antimicrobial peptide with cysteine-rich ß-sheets and broad-spectrum antimicrobial activity. CD14 is a protein involved in the detection of bacterial lipopolysaccharide (LPS) and has also been associated with periodontitis. This study investigates the single nucleotide polymorphic (SNP) region, -1654(V38I), of the human beta-defensin-1 (hBD-1) gene as well as the -159 region of the CD14 gene in subjects with chronic periodontitis.

Methods

Blood samples from periodontally healthy subjects and periodontitis patients were obtained. DNA was extracted from the blood and was used to perform restriction digest at the polymorphic G1654A site of DEFB1 with the enzyme HincII. The polymorphic site 159TT of CD14 was digested with the enzyme AvaII. Enzyme-linked immunosorbent assay (ELISA) was performed on soluble samples to determine the protein expressions.

Results

The control and patient groups expressed 35% and 38% 1654 A/A genotype of DEFB1, respectively. The A allele frequency of the control group was 40%, while the patient blood group was 54%. The mean hBD-1 protein levels of the control and patient samples were 102.83 pg/mL and 252.09 pg/mL, respectively. The genotype distribution of CD14 in healthy subjects was 16% for C/C, 26% for T/T and 58% for C/T. The genotype frequencies of CD14 in periodontitis patients were 10% for C/C, 43% for T/T and 47% for C/T. The CD14 protein expression determined by ELISA showed a mean protein level of the control samples at 76.28ng/mL and the patient blood samples at 179.27ng/mL with a p value of 0.001.

Our study demonstrated that patients suffering from chronic periodontitis present more commonly with the 1654A/A genotype on the DEFB1 gene and the 159T/T genotype on the CD14 gene.

Conclusions

This study purely investigated the association between periodontitis and one polymorphic site on both DEFB1 and CD14 gene, with the purpose of expanding knowledge for the future development in diagnostic markers or therapeutic interventions to combat this disease.

CD14 gene polymorphism is not associated with asthma but rather with bronchial obstruction and hyperreactivity in Slovenian children with non-atopic asthma

BACKGROUND

Though the associations of CD14 with asthma have already been studied, the results of different independent studies are in conflict, mostly due to differences in the pathogenesis of varying asthma sub-phenotypes. The aim of our study was to perform an association analysis of promoter single nucleotide polymorphism (SNP) -159C/T (rs2569190) in the CD14 gene for Slovenian children with asthma.

METHODS

We analyzed SNP -159C/T in a group of all asthmatics, and separately in a group of atopic and non-atopic asthmatics. We also analyzed the influence of SNP -159C/T on clinical parameters and the response to therapy with inhaled corticosteroids. We have genotyped 247 children with asthma and a median age of 11 years (interquartile range, 5 years), and 158 healthy controls with a median age of 13 years (interquartile range, 5 years). We performed genotyping using a polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) analysis.

RESULTS

We found that SNP -159C/T in CD14 is not associated with asthma in Slovenian children. However, non-atopic asthmatics with CT or TT genotypes have a lower FEV1/FVC ratio as a measure of bronchial obstruction (87.4%, compared to 91.8% in patients with the CC genotype, p = 0.017). Non-atopic asthmatics with CC or CT genotypes also have increased bronchial hyperreactivity measured by PC20 of methacholine (0.41 mg/ml, compared to 1.50 mg/ml in patients with a TT genotype, p = 0.018).

CONCLUSIONS

Our results suggest that CD14 is associated with asthma severity in Slovenian children with non-atopic asthma.

Association of CD14 -260 (-159) C>T and asthma: a systematic review and meta-analysis

Background

Asthma is a phenotypically diverse disease with genetic susceptibility. A single nucleotide polymorphism (SNP) in the CD14 gene at position -260 (also known as -159) C>T has been inconsistently associated with asthma. The aim of this study was to estimate the combined likelihood of developing asthma given the CD14 -260C>T genotype.

Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic search and meta-analysis of the literature was conducted to estimate the association between this SNP and asthma. Planned subgroup analyses were performed to detect potential sources of heterogeneity from selected study characteristics. Post-hoc sensitivity analysis was performed to identify studies exerting excessive influence on among-study heterogeneity and combined effects.

Results

Meta-analysis of 23 studies yielded a non-significant overall association with high heterogeneity across studies. After restricting analysis to studies using atopic asthma and non-atopic non-asthma case-control phenotypes and excluding studies influencing heterogeneity, the genotype-specific odds ratios (ORs) suggested a codominant model. Carriers of the TT and CT genotypes were about 33% less likely (OR = 0.67, 95% CI: 0.54-0.84) and about 20% less likely (OR = 0.80, 95% CI: 0.66-0.95), respectively, to have atopic asthma compared to carriers of the CC genotype. Among-study heterogeneity may be explained by overly broad asthma phenotype definitions, gene-environment interactions, and gene-gene interactions.

Conclusions

A protective dose-response relationship between the CD14 -260T allele and atopic asthma susceptibility was observed. These results demonstrate the importance of precisely specified case-control groups as well as the need to assess interactions in the investigation of complex diseases such as asthma.

The lung: the natural boundary between nature and nurture

Common lung diseases such as asthma, COPD, and pulmonary fibrosis cause significant morbidity and mortality in the U.S. and worldwide. Research investigating the mechanisms of disease etiology has clearly indicated that genetic attributes and environmental exposures each play important roles in the development of these diseases. Emerging evidence underscores the importance of the interplay between genetic predisposition and environmental factors in fully understanding the development of lung disease. Herein we discuss recent advances in knowledge and technology surrounding the role of genetics, the environment, and gene-environment interactions in these common lung diseases.

The effect of CD14 C159T polymorphism on in vitro IgE synthesis and cytokine production by PBMC from children with asthma

BACKGROUND

Even though the genotype at the promoter region of the CD14 molecule is known to affect the atopic phenotypes, the cellular and molecular basis of this association is largely unknown.

OBJECTIVE

To investigate the effect of lipopolysaccharide (LPS) on IgE production and cytokine profile by peripheral blood mononuclear cells (PBMC) obtained from asthmatic children with the TT and the CC genotypes at position -159 of the CD14 gene.

METHODS

Peripheral blood mononuclear cells from asthmatic children with alternative genotypes at CD14 C159T locus were stimulated with 2 and 200 ng/ml LPS in vitro. The IgE, IgG and, IgM response was determined by ELISA and Ig έ-germline, IgG, and IgM transcription by real-time PCR. A cluster of cytokines was measured by cytometric bead array.

RESULTS

Asthmatic children with the TT genotype but not those with the CC genotype responded with increased IgE synthesis and germline transcription to LPS stimulation. There were no genotype-related differences in IgG and IgM. TT but not the CC genotype was associated with significantly increased interleukin (IL)-4/IL-12 and IL-4/interferon-gamma (IFN-γ) ratios in the culture supernatant. There were no genotype-related differences in IL-1β, IL-7, IL-10, IL-13, IL-17A, granulocyte colony stimulating factor, granulocyte macrophage colony stimulating factor, monocyte chemotactic protein, and tumor necrosis factor alpha.

CONCLUSION

Peripheral blood mononuclear cells from asthmatic children with the TT genotype at position -159 of the CD14 gene make more IgE than those with the CC genotype following LPS stimulation because of increased germline transcription and have an augmented Th2 cytokine profile.

The -159C/T polymorphism in the CD14 gene and the risk of asthma: a meta-analysis

The -159C/T polymorphism in the CD14 gene has been implicated in susceptibility to asthma, but a large number of studies have reported inconclusive results. The aim of this study is to investigate the association between the -159C/T polymorphism in the CD14 gene and the risk of asthma by meta-analysis. We searched Pubmed, Embase, CNKI database, Wanfang database, Weipu database, and Chinese Biomedical database, covering all publications (last search been performed on April 20, 2010). Statistical analysis was performed by using the softwares Revman 4.2 and STATA 10.0. A total of 17 case-control studies in 17 articles (4,246 cases and 3,631 controls) were included in this meta-analysis. There was no association between this polymorphism and asthma risk in combined analyses (odds ratio (OR) = 0.86 and 95% confidence interval (95% CI) = 0.72-1.02, P = 0.09 for TC + TT vs. CC). In the subgroup analysis by age, ethnicity, and atopic status, no significant associations of asthma risks were obtained from age groups, ethnic groups, and atopic groups for TC + TT vs. CC comparison. For atopic population, significant decreased atopic asthma risks were found among Asian population (OR = 0.69, 95% CI 0.52-0.92, P = 0.01) and children population (OR = 0.69, 95% CI 0.54-0.89, P = 0.0004) for TC + TT vs. CC comparison. This meta-analysis suggests that CD14 is a candidate gene for atopic asthma susceptibility. The -159C/T polymorphism may be a protective factor for atopic asthma in Asian and children. More studies are needed to validate these associations.

CD14 (C-260T) polymorphism is not associated with sudden infant death syndrome (SIDS) in a large South Australian cohort

Similarities have been drawn between models of endotoxic shock and gross and microscopic pathology observed in sudden infant death syndrome (SIDS) cases. Polymorphisms in genes that influence the expression of endotoxin receptors could affect the outcome of toxaemia, and could, therefore, play a role in SIDS. The CD14 gene promoter contains a single nucleotide polymorphism that affects the level of CD14 gene expression. The TT genotype of the CD14 (C-260T) polymorphism causes a significantly higher density of CD14 receptor expression on monocytes which makes the individual more sensitive to endotoxin than those with the wild-type (CC). This investigation was designed to determine whether SIDS infants have a higher frequency of the CD14 (C-260T) polymorphism compared with non-SIDS controls. One hundred and sixteen SIDS and 228 control infants were genotyped using PCR followed by restriction fragment length analysis of amplified product. Carriage of the TT or CT genotypes did not significantly differ between SIDS and control infants (P = 0.218 and 0.081, respectively). The frequencies observed in the control group were consistent with Hardy-Weinberg equilibrium and did not differ significantly from the published frequencies in Caucasian Australians. These results suggest that CD14 (C-260T) polymorphism is unlikely to be implicated in SIDS.

Association of the CD14 Gene Polymorphism C-159T with Allergic Rhinitis

Background

Altered expression of the cluster differentiation antigen, CD14, may affect the proportion of T-helper type 1 (Th1) to Th2 cells, thereby influencing the immunoglobulin E (IgE) response and associated inflammatory phenotype in allergic conditions. Therefore, the gene encoding CD14 is considered as a positional candidate gene for atopy. Recently, a functional C-159 T polymorphism has been described in the promoter region of the gene and has been associated with increased gene expression and atopic phenotypes in various ethnic populations. We evaluated the relationship between the C-159 T polymorphism in the promoter of the CD14 gene and the total serum IgE level in Chinese adult patients with allergic rhinitis.

Methods

Polymerase chain reaction with restriction fragment length polymorphism (RFLP) analysis was used to determine the C-159 T polymorphism in subjects with allergic rhinitis (n = 92) and nonallergic disease controls (n = 72). Total serum IgE was also measured.

Results

In the allergic rhinitis group, the frequency of the TT homozygotes was significantly higher than for the control group (p < 0.05). In both groups, the C-159 T polymorphism is not associated with serum IgE levels.

Conclusions

TT homozygotes are more common in adult patients with allergic rhinitis among the Chinese population.

The role of lipopolysaccharide in the development of atopy in humans

Atopy is a highly prevalent condition and remains the single biggest risk factor for asthma. Although atopy has a heritable component, the time frame of the increase in the prevalence indicates that it is not due to genetic factors alone. The relationship between allergen exposure and sensitization is complex. Lipopolysaccharide (LPS) and its bioactive moiety endotoxin are common to all gram-negative bacteria, and have been used as a surrogate of microbial load. Endotoxin can be readily measured in dust collected from homes. Some studies have demonstrated a clear inverse dose-response relationship between exposure to endotoxin and the risk of atopy but this finding has not been reproduced in all studies. Our innate immune system recognizes LPS readily via the LPS signal transduction pathway, which has the trimolecular complex of CD14/TLR4/MD2 at the core. A common single-nucleotide polymorphism in the promoter region of CD14 rs2569190 C to T (CD14/-260 or CD14/-159) has been associated with elevated sCD14. Although early studies suggested that this variant was associated with more severe atopy, this finding was not uniformly replicated. It has now been demonstrated in four independent populations that high exposure to endotoxin in the domestic environment is protective against the development of atopy, but only among carriers of the C allele, that is, the environmental exposure is only relevant when taken in the context of the genotype. Furthermore, this interaction is biologically plausible. We propose that neither the environmental exposure nor the genotype in isolation is sufficient to cause complex diseases like asthma and atopy, but disease results from the one acting in the context of the other, of which CD14 and endotoxin is one example contributing to the risk for atopy.

Opposite gene by environment interactions in Karelia for CD14 and CC16 single nucleotide polymorphisms and allergy

BACKGROUND

Finnish Karelians have a higher prevalence of allergic disease than Russian Karelians. As both populations are generally from the same ethnic group, the Karelian population offers a unique opportunity to analyse genetic and allergic disease interactions between 'Western' and 'Eastern' environments.

OBJECTIVES

We investigated associations between allergic diseases and CD14 and CC16 polymorphisms in Finnish vs Russian Karelian women.

METHODS

Adult female Karelians (330 Finnish and 274 Russian) were recruited, examined for a range of symptoms and conditions including rhinitis, itchy rash, asthma and atopy and genotyped for CD14 C-159T and CC16 A38G.

RESULTS

For both CD14 C-159T and CC16 A38G, the risk allele for atopic phenotypes in Finnish Karelia was the protective allele in Russian Karelia. For CD14 C-159T, an interactive effect on ever itchy rash (P(interaction) = 0.004), itchy rash <12 mo (P(interaction) = 0.001) and dry cough at night in the past 12 months (<12 months) (P(interaction) = 0.011) was found; the risk allele was C in Russians and T in Finns. For CC16 A38G, an interaction was significant for ever rhinitis (P(interaction) = 0.006), rhinitis <12 mo (P(interaction) = 0.004), and marginally significant for ever hayfever (P(interaction) = 0.07), allergic eye symptoms <12 mo (P(interaction) = 0.09); their risk allele was G in Russians and A in Finns.

CONCLUSION

An Eastern vs Western environment appears to exert an effect via opposite alleles on risk of allergic diseases in adult women.

The association with the -159C/T polymorphism in the promoter region of the CD14 gene and juvenile idiopathic arthritis in a Chinese Han population

OBJECTIVE

Juvenile idiopathic arthritis (JIA) is generally considered to be caused by interaction of genetic and environmental factors. We investigated the association of a C-to-T transition in the promoter region of the CD14 gene on chromosome 5q31.1 and JIA in a Chinese Han population.

METHODS

One hundred sixty-three children with JIA and 281 healthy children (age- and sex-matched to JIA group) were studied. Polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) was used for analysis of the genotypes. (Trial registration number ChiCTR-CCC-00000312.)

RESULTS

CD14 promoter-159 genotype frequencies of CC, CT, and TT were 11.48%, 49.18%, and 39.34%, respectively, in the systemic onset JIA group; 21.62%, 43.24%, and 35.14%, in the polyarticular JIA group; 16.67%, 50%, and 33.33%, in the oligoarticular JIA group; 6.9%, 75.86%, and 17.24%, in the group with other types of JIA; and 37.01%, 46.98%, and 16.01%, in the control group. Genotype frequency and allele frequency distribution were in accord with Hardy-Weinberg equilibrium. There were statistically significant differences in frequencies of genotype and allele in CD14 C-159T polymorphism between JIA group and control group (genotype: chi-squared = 33.168, p < 0.05, CT vs CC, OR 2.946, 95% CI 1.739-4.990; TT vs CC, OR 5.426, 95% CI 2.977-9.891. Allele: chi-squared = 33.168, p < 0.05, T vs C, OR 2.251, 95% CI 1.704-2.973). The T allele frequencies of boys and girls were significantly higher than those in the control group (p < 0.001 of both).

CONCLUSION

CD14 gene promoter C-159T polymorphism is significantly correlated with JIA in the Chinese Han population. The T allele of the C-159T polymorphism of CD14 gene may be a genetic risk factor for JIA.

CD14 and toll-like receptor gene polymorphisms, country living, and asthma in adults

RATIONALE

It has been shown that country living protects against asthma, which may be explained by microbial exposures.

OBJECTIVES

To study whether single nucleotide polymorphisms (SNPs) in CD14 and Toll-like receptor (TLR) 2, TLR4 and TLR9 genes are associated with asthma in adults, and whether these SNPs modify associations between country living and asthma.

METHODS

Twenty-five SNPs in CD14, TLR2, TLR4, and TLR9 genes were genotyped in adult subjects from the French Epidemiological study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness, and Atopy (EGEA). We conducted a case-control analysis on unrelated subjects (239 with asthma and 596 without asthma), and a family-based association test (FBAT) in 192 families ascertained through probands with asthma.

MEASUREMENTS AND MAIN RESULTS

The TLR2/+596 C allele was associated with an increased risk for asthma in both case-control and family-based analyses (under a dominant model, odds ratio [OR] 1.91 and 95% confidence interval [CI] 1.34-2.72, P = 0.0003; Z statistics from FBAT = 2.48, P = 0.01). In skin prick test (SPT) positive subjects, the CD14/-260 C allele was negatively associated with asthma (additive model, OR 0.66; CI 0.48-0.91). Significant gene-environment interactions between variation in CD14 and TLR genes and country living during childhood were found for ten SNPs. In SPT positive subjects carrying CD14/-260 CC, country living protected against asthma (OR, 0.32; 95% CI, 0.12-0.85), whereas country living was not associated with asthma in subjects who were atopic and carrying CD14/-260 T (OR, 1.11; 95% CI, 0.65-1.90) (gene-environment interaction, P < 0.05).

CONCLUSIONS

TLR2 and CD14 SNPs were associated with asthma and atopic asthma respectively. In addition, CD14, TLR2, TLR4, and TLR9 SNPs modified associations between country living and asthma.

Does the relationship between IgE and the CD14 gene depend on ethnicity?

This review considers the data from studies analysing associations between the CD14C-159T single nucleotide polymorphism (SNP) and asthmatic phenotypes and discusses the variability of the conclusions. By searching PubMed and EMBASE for articles on CD14C-159T -related population or family-based association studies, 47 were identified up till September 2007. Collectively, the studies reviewed herein consistently showed population differences in frequencies of the alleles of the SNP, with African descent having the highest C allele frequencies, followed by Caucasians and Asians. The T allele of the SNP was associated with increased sCD14 in some studies but not in others. Inconsistently, the C allele, or even occasionally the T allele, was associated with atopic phenotypes in a population subgroup. There are several explanations for these inconsistencies, including lack of power, linkage disequilibrium, gene-gene interactions, population admixture and gene-environment interactions. If the SNP was associated with functional changes to the coded protein and thus modulating susceptibility to allergic disease, its effect may be modest and dependent on other co-existent, ethnicity-specific, genetic or environmental risk factors.

Bovine CD14 gene characterization and relationship between polymorphisms and surface expression on monocytes and polymorphonuclear neutrophils

Background

CD14 is an important player in host innate immunity in that it confers lipopolysaccharide sensitivity to cell types like neutrophils, monocytes and macrophages. The study was aimed at characterizing the CD14 gene of cattle for sequence variations and to determine the effect of variations on the expression of the protein on the surfaces of monocytes and neutrophils in healthy dairy cows.

Results

Five SNPs were identified: two within the coding regions (g.A1908G and g.A2318G, numbering is according to GenBank No. EU148609), one in the 5' (g.C1291T) and two in the 3' (g.A2601G and g.G2621T) untranslated regions. SNP 1908 changes amino acid 175 of the protein (p.Asn175Asp, numbering is according to GenBank No. ABV68569), while SNP 2318 involves a synonymous codon change. Coding region SNPs characterized three gene alleles A (GenBank No. EU148609), A₁ (GenBank No. EU148610) and B (GenBank No. EU148611) and two deduced protein variants A (ABV68569 and ABV68570) and B (ABV68571). Protein variant A is more common in the breeds analyzed. All SNPs gave rise to 3 haplotypes for the breeds. SNP genotype 1908AG was significantly (P < 0.01) associated with a higher percentage of neutrophils expressing more CD14 molecules on their surfaces. The promoter region contains several transcription factor binding sites, including multiple AP-1 and SP1 sites and there is a high conservation of amino acid residues between the proteins of closely related species.

Conclusion

The study has provided information on sequence variations within the CD14 gene and proteins of cattle. The SNP responsible for an amino acid exchange may play an important role in the expression of CD14 on the surfaces of neutrophils. Further observations involving a larger sample size are required to validate our findings. Our SNP and association analyses have provided baseline information that may be used at defining the role of CD14 in mediating bacterial infections. The computational analysis on the promoter and comparative analysis with other species has revealed regions of regulatory element motifs that may indicate important regulatory effects on the gene.

Asthma genetics: personalizing medicine

Asthma is a chronic inflammatory lung disease that leads to significant morbidity, mortality, and economic burden. The clinical symptoms, which are a result of airway inflammation and reversible airway obstruction, have led to the mainstay of therapies for asthma: anti-inflammatory medications and bronchodilators. However, the efficacies of the various classes of medications are not equal among all patients and may be affected by asthma phenotypes, environmental exposures, and genetic differences. Similarly, the risk for developing asthma and the natural history of the disease show great inter-individual variability due to these same factors. Over the past few decades, much effort has been focused on the genetics of asthma, and investigators have identified more than one hundred potential asthma susceptibility genes, of which at least ten have been replicated in numerous independent studies. In parallel, researchers have also identified genetic factors that impact the pharmacotherapeutic responses to the major classes of asthma medications. While the results of previous studies have been promising, future investigations need to combine genetics, pharmacogenetics, accurate disease phenotyping, and environmental exposures to build the foundation for personalized and predictive medicine for the 21st century. The ultimate goal is to enable physicians to identify those at risk for asthma, intervene to prevent or attenuate the disease, and select the optimal medical regimen for each individual patient. If successful, the resulting paradigm shift in medical practice will lead to improved clinical outcomes and decreased health care expenditures.

Discovering susceptibility genes for asthma and allergy

Asthma and asthma-related traits are complex diseases with strong genetic and environmental components. Rapid progress in asthma genetics has led to the identification of several candidate genes that are associated with asthma-related traits. Typically the phenotypic impact of each of these genes, including the ones most often replicated in association studies, is mild, but larger effects may occur when multiple variants synergize within a permissive environmental context. Despite the achievements made in asthma genetics formidable challenges remain. The development of novel, powerful tools for gene discovery, and a closer integration of genetics and biology, should help to overcome these challenges.

Childhood asthma epidemiology: insights from comparative studies of rural and urban populations

Asthma is one of the most common chronic respiratory disorders. Many epidemiology studies have suggested an increasing trend of asthma in many different regions of the world but the exact reasons explaining such trend remain unclear. Nevertheless, changing environmental factors are most likely important in explaining the trend of asthma. Studies in the past decade have clearly shown a mark difference in the prevalence between urban and rural regions. The consistent findings of a markedly lower prevalence of asthma in children and adults who have been brought up in a farming environment clearly indicate the importance of environmental influence of asthma development. Although the exact protective environmental factors in the rural region remain to be defined, there have been many studies suggesting that early exposure to microbes or microbial products may play a role in modulating the immune system so as to reduce the future risk of asthma and allergies. Advances in the understanding of the genetic predisposition and how these genetic factors may interact with specific environment factors are of paramount importance for the future development of primary preventive strategies for asthma.

CD14, endotoxin, and asthma risk: actions and interactions

A functional single nucleotide polymorphism in the 5 genomic region of CD14 (CD14/-159) is one of the most widely tested genetic variations in relation to asthma and associated traits. The results of these studies have shown a remarkable, statistically significant heterogeneity, with some studies indicating the T-allele as a risk factor, others the C-allele, and others finding no association. Recent studies in which exposure to house-dust endotoxin or to domestic sources of microbial exposure were assessed concomitantly with CD14/-159 have shown a consistent, replicable gene-environment interaction. Specifically, results suggest that the C-allele is a risk factor for allergic phenotypes at low levels of exposure, whereas the T-allele is a risk factor at high levels of exposure. This finding seems to be explained by a genetically-determined heterogeneity for the protective effect of microbial exposure on allergic phenotypes, with homozygotes for the C-allele showing a much stronger negative association between exposure and allergic outcomes than carries of the other two genotypes. These results suggest that the often encountered, limited replicability of genetic associations may, at least in part, be due to complex interactions between genes and environment in determining asthma-related outcomes.

Association between Q551R IL4R genetic variants and atopic asthma risk demonstrated by meta-analysis

BACKGROUND

IL4R, the gene encoding the alpha chain of the IL-4 and IL-13 receptors, has received extensive attention as a candidate gene for asthma risk. However, the results from studies testing for associations of the I50V and Q551R IL4R genetic variants are conflicting.

OBJECTIVE

We sought to determine the average risk of asthma associated with the I50V and Q551R IL4R variants based on the results of case-control studies reported in the literature.

METHODS

Meta-analyses were performed with data from case-control association studies that met specified inclusion criteria (9 and 8 studies for I50V and Q551R, respectively). Random-effects models were used to calculate combined odds ratios (ORs) and significance of associations. Analyses were performed for asthma in general and for subgroups based on the atopy status of the asthma population.

RESULTS

The R551 IL4R variant was significantly associated with increased risk of asthma, most notably atopic asthma (combined OR, 1.6; P = .004). Exclusion of the outlier study reporting an OR of less than 1 greatly increased the significance of association (OR, 1.8; P = 3 x 10(-9)). I50V variants were not significantly associated with asthma.

CONCLUSIONS

A meta-analysis of results from case-control studies strongly supports the conclusion that the R551 IL4R variant imparts a modest yet significant risk for atopic asthma.

CLINICAL IMPLICATIONS

Knowledge that the R551 IL4R variant is associated with increased asthma risk should provide a basis for understanding the heterogeneity of asthma pathogenesis and for pharmacogenetic approaches to treat individuals carrying this variant.

No association of polymorphisms in the 5' region of the CD14 gene and food allergy in a Japanese population

BACKGROUND

The gene encoding CD14 is a positional candidate gene for allergic diseases as it is localized on chromosome 5q31, a region that is linked to atopy-related phenotypes. Although it has been shown that a polymorphism in the 5' region of the CD14 gene is associated with food allergy in white subjects, it is not clear whether this association is also present in the Japanese population.

METHODS

Eighty-eight children with food allergy were recruited along with 101 children controls without food allergy. DNA samples from these subjects were genotyped by PCR-based restriction fragment length polymorphism (RFLP) assay to investigate the relationship between two polymorphisms in the 5' region of the CD14 gene (C-159T and C-550T) and food allergy.

RESULTS

There was no association among the CD14 alleles, dominant model or recessive model of either polymorphism with food allergy.

CONCLUSIONS

The CD14-159 and -550 polymorphisms might not play a major role in the pathogenesis of food allergy in Japanese children.

Genetic predisposition to asthma and atopy

A large number of studies have tried to identify heritable components in the susceptibility to asthma and atopy phenotypes. This review examines the evidence of multigenetic inheritance for these conditions. We identified in the literature at least 372 gene-disease association studies for asthma and 124 for atopy published in the last 6 years. Gene-environment analyses were performed in 41 and 14 articles, respectively, in the same time period. Many postulated associations have been probed with limited sample sizes and will require more extensive replication and large-scale evidence. Meta-analyses have been performed for polymorphisms in 5 genes and provide modest evidence for genetic association of asthma with ADAM33 and TNFA gene polymorphisms. Meta-analyses of linkage studies show that it is unlikely to detect strong linkage peaks for asthma susceptibility. However, linkage was claimed between loci on chromosomes 2, 4, 6, 9, 10, 11 and 15 and total serum IgE levels. Careful definitions and standardization of phenotypes across teams of investigators are important to endorse. New large-scale testing platforms may offer new opportunities for discovering susceptibility gene variants, but they need to be coupled with careful study design, international collaboration, and possibly also dissection of gene-environment interactions.

The early-life origins of asthma

PURPOSE OF REVIEW

Inflammatory mediators produced from activated mast cells and T helper type 2 cells drive allergic inflammation. The pathways required for mast and T helper type 2 cell activation and the effects of their products are being defined in order to identify new therapeutics. We focus on recent findings on the chief inducer of mast cell activation, the IgE receptor-signaling cascade, and the development of new inhibitors of this pathway. We also summarize work that examines the molecular mechanisms utilized by the interleukin IL-4/13 receptors and characterizes therapeutic compounds that target these pathways.

RECENT FINDINGS

The tyrosine kinases Lyn, Fyn and Syk have complex roles in IgE receptor signaling. Biochemical analysis and gene expression profiling have shed light on both the positive and negative functions of these proteins and establish additional connections with downstream pathways. Syk inhibitors were identified that may prove useful as antiinflammatory agents. Progress has been made in characterizing how IL-4/13 interact with their cognate receptors that will aid in the design of inhibitors of these interactions.

SUMMARY

Recent studies have advanced our understanding of how the IgE receptor and IL-4/13 receptors function. This new knowledge may lead to the development of novel and highly specific inhibitors of allergic inflammation.

Gene by environment interaction in asthma

Asthma is a chronic inflammatory disease of the airways that is highly prevalent in the Western world. It is a genetically complex disease caused by multiple genetic and environmental factors, which may interact. Genetic research has recently incorporated environmental factors to investigate gene by environment interaction, and the first examples of gene by environment interaction in asthma have been reported. Linkage analyses indicate that one or more genes on chromosome 5q interact with environmental tobacco smoke in infancy in asthma development. Several candidate genes have been consistently shown to interact with the environment. These include the innate immunity genes CD14 and Toll-like receptor 4, and microbial exposures, as well as the detoxifying gene family glutathione-S-transferase and environmental tobacco smoke exposure and air pollutants. Gene by environment interaction is important in asthma pathogenesis, and future studies should take the interaction of both factors into account.

Failure to find an association between CD14-159C/T polymorphism and asthma: a family-based association test and meta-analysis

BACKGROUND

CD14 is an essential component of the receptor for lipopolysaccharide (LPS). LPS stimulates T-helper type 1 (Th1) cytokine expression, potentially suppressing Th2 immune responses involved in IgE-mediated allergic diseases. Previous studies have reported that -159C/T, a promoter polymorphism of CD14, is associated with total serum IgE levels and atopy, but other studies have shown conflicting results.

METHODS

To examine possible associations of CD14 polymorphisms with asthma susceptibility, we performed transmission disequilibrium tests (TDTs) of 137 Japanese families identified through children with atopic asthma.

RESULTS

We found no association between -159C/T polymorphism and asthma (p= 0.37). Quantitative TDT and ANOVA showed no association between the -159C/T genotype and total serum IgE levels. We also performed a meta-analysis of data from all available studies. Neither a fixed-effects model nor a random-effect model showed a significant odds ratio for the -159C/T polymorphism (p > 0.1).

CONCLUSIONS

Our data indicate that CD14 does not contribute substantially to susceptibility to asthma. Further studies examining both genotypes and environmental factors will be necessary to elucidate the role of CD14 in the development of allergic diseases.

The role of Toll-like receptors and related receptors of the innate immune system in asthma

PURPOSE OF REVIEW

The biology of the innate immunity receptors is of central importance in the host response to the environment. Identifying genetic variants that alter the innate immune response is highly relevant to understanding asthma pathogenesis. This review summarizes recent studies of the role of innate immunity receptors, including Toll-like receptors and CD14, in the pathogenesis of asthma.

RECENT FINDINGS

The majority of studies published since 2004 have been genetic association studies in various clinical settings, which have found positive associations of single nucleotide polymorphisms in TLR2, TLR4, TLR6 and TLR10 with asthma or atopy, although the number of studies is small and the results not yet replicated. The designs for CD14 genetic studies have been more sophisticated and have included gene-environment interaction. The results of CD14 gene associations with asthma and atopy are suggestive but have not been fully replicated. Potential reasons for non-replication of TLR and CD14 association studies include insufficient power, type I error, population heterogeneity and different phenotypes studied. In addition, there may be differences in CD14 genetic effects between childhood and adulthood, and between levels of endotoxin exposure.

SUMMARY

The evidence is still being accumulated for the role of Toll-like receptor polymorphisms in the pathogenesis of asthma. There is emerging evidence for the role of CD14 polymorphisms in the development of asthma and atopy. Further studies of innate immunity in asthma and allergy are required, using rigorous study design, measurement of environmental exposure and intermediate phenotypes to demonstrate single nucleotide polymorphism functionality.

Gene by Environment Interaction: The -159C/T Polymorphism in the Promoter Region of the CD14 Gene Modifies the Effect of Alcohol Consumption on Serum IgE Levels

BACKGROUND

Serum IgE is increased in heavy drinkers. Endotoxin mediates most of the immunological alterations associated with heavy drinking. The -159C/T polymorphism in the promoter region of the gene encoding CD14 (an endotoxin receptor) is associated with serum IgE levels in different populations.

AIM

To investigate the possible interaction between alcohol intake and the -159C/T polymorphism in the promoter region of the CD14 gene for serum IgE levels.

METHODS

A total of 415 individuals (51.6% males, median age 50 years, range 18-92 years) were studied. A total of 140 individuals were alcohol abstainers, 112 were moderate drinkers (1-280 g/week), and 163 were heavy drinkers (>280 g/week). Main determinations included the CD14/-159C/T genotype, a panel of skin prick tests, total serum IgE, and specific serum IgE against common aeroallergens (Phadiatop test).

RESULTS

Heavy drinking was associated with increased total serum IgE values and with positive specific serum IgE to common aeroallergens, but the association was stronger in carriers of the CD14/-159C allele (either CC homozygotes or CT heterozygotes) than in CD14/-159TT homozygotes. Both additive and multiplicative interactions between heavy drinking and the CD14/-159C allele for total and specific serum IgE values was still present after adjusting for potential confounders. Neither alcohol consumption nor the CD14/-159 genotype was associated with skin prick test positivity.

CONCLUSIONS

The CD14/-159C/T polymorphism modifies the effect of alcohol consumption on serum IgE levels.

Old meets new: the interaction between innate and adaptive immunity

The innate immune system is an ancient and diverse collection of defenses, including the recognition of pathogens through the use of germline-encoded pathogen receptors. The adaptive immune system, encompassing T and B cell responses, is a more recent development that utilizes somatically recombined antigen receptor genes to recognize virtually any antigen. The adaptive immune system has the advantage of flexibility and immunologic memory but it is completely dependent upon elements of the innate immune system for the initiation and direction of responses. Appropriate innate and acquired immune system interactions lead to highly efficient recognition and clearance of pathogens, but maladaptive interactions between these two systems can result in harmful immunologic responses including allergy, autoimmunity, and allograft rejection.