Linkages and associations to intermediate phenotypes underlying asthma and allergic disease:

PAI-1 Gene Polymorphism Was Associated with an Increased Risk of Allergic Diseases: Evidence from a Meta-Analysis of 14 Case-Control Studies

INTRODUCTION

In recent years, many studies have focused on the association between plasminogen activator inhibitor (PAI)-1 gene 4G/5G polymorphism and risk of allergic diseases, but the results have been inconclusive.

OBJECTIVE

We conducted this meta-analysis to study the exact relationship between PAI-1 polymorphism and susceptibility to allergic diseases.

METHODS

All eligible studies were determined by an electronic literature search. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association under all of the models.

RESULTS

A total of 14 studies involving 2,327 cases and 2,838 controls were included in this meta-analysis. Overall, we found a significant association between PAI-1 polymorphism and risk of allergic diseases (4G/4G + 4G/5G vs. 5G/5G: OR 1.76, 95% CI 1.39-2.22, p < 0.00001). In a subgroup analysis by ethnicity, we found a markedly increased risk in Asians (OR 1.62, 95% CI 1.26-2.09, p = 0.0002) and Caucasians (OR 1.78, 95% CI 1.26-2.52, p = 0.001). In addition, significant associations between PAI-1 polymorphism and risk of allergic diseases were observed in both adults (OR 1.71, 95% CI 1.23-2.38, p = 0.001) and children (OR 1.87, 95% CI 1.42-2.46, p < 0.00001). In a subgroup analysis by different allergic diseases, a significantly increased risk was found for asthma (OR 1.78, 95% CI 1.33-2.39, p = 0.001) but not for rhinitis (OR 1.51, 95% CI 0.79-2.89, p = 0.22).

CONCLUSION

This meta-analysis demonstrated that PAI-1 gene 4G/5G polymorphism was associated with an increased risk of allergic diseases.

Genome-wide association studies on IgE regulation: are genetics of IgE also genetics of atopic disease?

PURPOSE OF REVIEW

Total IgE levels are considered a useful endophenotype for studying the genetics of atopic diseases. However, the role and significance of genetic factors influencing IgE regulation for atopic diseases as endpoints is unclear.

RECENT FINDINGS

Recently, genome-wide association studies (GWASs) have been applied to atopic traits with considerable success. A total of seven published GWASs on asthma, one GWAS on eczema, and one GWAS on total IgE have reported 11 new loci. Most of these loci appear to be trait-specific. A notable exception is the Th2 cytokine cluster, where genetic variation seems to be relevant across atopic phenotypes.

SUMMARY

GWASs have identified several novel asthma and eczema loci as well as novel loci for IgE levels. In this review, we evaluate the interrelation between these loci and summarize to which degree recent findings on IgE reflect genetic vulnerability for atopic disease.

A quantitative genetic analysis of intermediate asthma phenotypes

AIM

To study the relative contribution of genetic and environmental factors to the correlation between exhaled nitric oxide (FeNO), airway responsiveness, airway obstruction, and serum total immunoglobulin E (IgE).

METHODS

Within a sampling frame of 21,162 twin subjects, 20-49 years of age, from the Danish Twin Registry, a total of 575 subjects (256 intact pairs and 63 single twins) who either themselves and/or their co-twins reported a history of asthma at a nationwide questionnaire survey, were clinically examined. Traits were measured using standard techniques. Latent factor models were fitted to the observed data using maximum likelihood methods.

RESULTS

Additive genetic factors explained 67% of the variation in FeNO, 43% in airway responsiveness, 22% in airway obstruction, and 81% in serum total IgE. In general, traits had genetically and environmentally distinct variance structures. The most substantial genetic similarity was observed between FeNO and serum total IgE, genetic correlation (rhoA) = 0.37, whereas the strongest environmental resemblance was observed between airway responsiveness and airway obstruction, specific environmental correlation (rhoE) = -0.46, and between FeNO and airway responsiveness, rhoE = 0.34.

CONCLUSIONS

Asthma is a complex disease characterized by a set of etiologically heterogeneous biomarkers, which likely constitute diverse targets of intervention.

Cecal ligation and puncture

The model of cecal ligation and puncture (CLP) in rodents has been used extensively to investigate the clinical settings of sepsis and septic shock. This model produces a hyperdynamic, hypermetabolic state that can lead to a hypodynamic, hypometabolic stage, and eventual death. Blood cultures are positive for enteric organisms very early after CLP. The model has been widely used over the past 26 years and is highly versatile in adapting to a range of severity and testing objectives. It is inexpensive to prepare and technically straightforward. Aspects of sepsis research investigated using CLP include energetics, metabolism, resuscitation, antibiotic therapy, microbial factors, cardiovascular responses, immune function, mediator release, and cytokine expression patterns. The challenge of the small circulating blood volume in rodents can be overcome by using micromethods that enable analysis of small volumes, or alternatively, by using a large number of animals to obtain serial samples.

Classic pars planitis: strong correlation of class II genes with gender and some clinical features in Mexican mestizos

The purpose of this study was the investigation of human leukocyte antigen (HLA) genes in Mexicans with classical Pars Planitis (CPP). Seventy-nine unrelated patients and 204 healthy controls were studied. HLA-A, -B, and -C typing was done on T cells isolated with immunomagnetic beads. HLA-DRB1, -DQA1, and -DQB1 loci were typed by polymerase chain reaction-sequence-specific oligonucleotide probes. The significance and strength of HLA associations were assessed. Stratification analyses were performed to analyze correlations between HLA alleles and clinical manifestations or gender. The mean age of CPP patients was 10 years old. The disease was recurrent (21.3%); 58% were males and 89.6% were bilaterally affected. A 3-year follow-up demonstrated no other associated disease. DRB1*0802 was significantly increased (odds ratio [OR] = 2.8, etiologic fraction [EF] = 18.96%). In females, HLA-B51 (OR = 9.8) was associated with nonsymmetrical onset and HLA-Cw1 (OR = 4.7) with symmetrical onset; DRB1*0802 was increased in males (OR = 3.9, p =5.0 E-05, EF = 38.3%) and contributed to their symmetrical onset (OR = 4.6, p =4.6 E-06, EF = 29.4%). Corneal peripheral endotheliopathy correlated with DQB1*0602 in females (OR = 17, EF = 47.1%). A susceptibility allele of Amerindian ancestry is responsible for juvenile CPP in Mexicans; HLA-B locus contributes to severity in females and DRB1*0802 in males. CPP should be classified as an heterogeneous illness taking into account ethnicity, and clinical and genetic characteristics.

Atopic asthma and TNF-308 alleles: linkage disequilibrium and association analyses

The association of a tumor necrosis factor -308 allele (TNF2) to asthma has been reported in some studies but not in others. The aim of this study was to test this association in a population recruited on the basis of allergy to Parietaria. In the study population, asthma was positively associated to HLA-DRB1*03 (p = 0.01) and to the haplotype TNF2/DRB1*03 (p = 0.02). In the parent subgroup, the proportion of asthmatics was increased in patients with TNF2 (p = 0.01), but the primary association of asthma was to the haplotype TNF2/DRB1*1104 (p = 0.005). The study population was subdivided according to prick skin test (ST) positivity to Lolium, Parietaria, and D. pteronyssinus. Asthma was associated to HLA-DRB1*03 and to the haplotype TNF2/DRB1*03 (p = 0.0015 and 0.0001, respectively) in patients ST positive to Lolium, and to the haplotype TNF2/DRB1*1104 (p = 0.025) in patients ST positive to Parietaria. The transmission disequilibrium test detected excess transmission of HLA-DRB1*03 and of the haplotype TNF2/DRB1*03 (p = 0.03 and 0.04, respectively) to siblings with asthma and ST positivity to Lolium and of HLA-DRB1*1104 and of the haplotype TNF2/DRB1*1104 (p = 0.04 and 0.015, respectively) to siblings with asthma and ST positivity to Parietaria. Taken together, these observations indicate that the haplotypes TNF2/DRB1*03 and TNF2/*B1*1104 contain alleles controlling atopic asthma in patients with sensitization to Lolium and Parietaria, respectively. This suggests that the association of asthma to TNF2 reflects linkage disequilibrium with genes influencing specific immune response.

Personalised prescribing for asthma--is pharmacogenetics the answer?

An individual's response to anti-asthma medication is likely to arise from a complex interaction between social, environmental and inherited factors. Studies indicate that genetic factors may account for 60-80% of the heterogeneity in treatment responsiveness in asthmatics. Identifying the genetic variants responsible may potentially lead to the development of novel treatments, improved effectiveness in the use of existing treatments and better prediction of efficacy in phase II and III trials. This article will briefly outline the current methods of identifying relevant treatment-responsive genes and their genetic variants. The pharmacogenetics of the main asthma treatment groups will then be reviewed in detail. Finally, the impact of pharmacogenetics on the pharmaceutical industry, and clinical practice in the future will be discussed.