Update on Asthma Genetics: Results From Meta-Analyses of Candidate Gene Association Studies.

Several studies have investigated the risk factors associated with asthma. Both genetic and environmental factors are considered to contribute to asthma susceptibility. Individual genetic association studies usually suffer from small sample size leading to biased results. Meta-analysis is a powerful tool that has the potential to resolve this limitation by increasing the statistical power of analyses. The current review summarizes the recent knowledge concerning genetic factors involved in asthma predisposition based on meta-analyses. Using the keywords: asthma, meta-analysis, polymorphism, we searched Pubmed, Medline, Embase and Google Scholar databases for the associated articles. Genetic polymorphisms in twenty-three genes are associated with asthma risk in meta-analyses. However, polymorphisms in nine genes showed none significant association. These findings are used to assess the genetic risk factors and to understand the molecular pathways related to asthma.

Intercellular adhesion molecule 1 K469E gene polymorphism is associated with presence of skin lesions in Tunisian Behçet's disease patients.

Intercellular adhesion molecule 1 (ICAM1) gene polymorphisms have been implicated in the susceptibility to inflammatory diseases. The expression of both soluble and tissue ICAM1 were increased in Behçet's disease (BD) but the contribution of ICAM1 gene polymorphisms to this disease remains unknown. We sought to establish the association of ICAM1 gene K469E polymorphism in exon 6 with susceptibility for BD. One hundred and thirty-five Tunisian patients who satisfied the International Study Group criteria for BD and 157 healthy blood donor controls from the same geographic area were genotyped by polymerase chain reaction method for the K469E ICAM1 gene polymorphisms in exon 6. There were no significant differences in the distribution of the K469E allele or genotype frequencies between the BD patients and healthy controls in the ICA1 gene. Among patients, significant association was found between the presence of skin lesions and the studied polymorphism in the distribution of the K469E allele (P = 0.004; odds ratio = 1.26; 95% confidence interval = 2.13-3.62) and genotype frequencies (P = 0.0028; chi(2) = 11.75). Our findings suggest that K469E ICAM1 gene polymorphism was associated with Tunisian BD patients with skin lesions.

Toll-like-receptor gene polymorphisms in a Tunisian population with Behçet's disease.

OBJECTIVE: The manifestations of BD are considered to have developed as a result of immunological dysfunction, which is suggested to be induced by microbial pathogens. The Toll-like receptor (TLR) genes were known to be associated with a variety of infectious diseases due to their central role in both innate and adaptive immunity. In this report, we investigated the possible association between BD patients and genetic variations within the TLR 2, 4 and 9 genes in a Tunisian population. PATIENTS AND METHODS: 135 Tunisian BD patients and 159 healthy blood donors from the same geographical area were genotyped by polymerase chain reaction for the TLR polymorphisms. RESULTS: Among the TLR polymorphisms, only the distribution of TLR9 1486 T/C genotype (p=0.07; chi2=3.30; OR=1.54; 95% CI=0.94-2.51) and allele (p=0.08; chi2=2.91; OR=1.34; 95% CI=0.94-1.92) frequencies was different between BD patients and healthy controls, but did not reach statistical significance. For the TLR9 1237 T/C, the distribution of genotypes and alleles were not significantly different comparing total patients with controls. There were no associations between the studied polymorphisms and the main clinical manifestations of BD. The G, T and A allele of the TLR4 1896 A/G, TLR4 11196 C/T and TLR2 12408 G/A polymorphisms were uncommon and absent in the Tunisian population. CONCLUSION: Our results showed that SNPs in the TLR2, 4 and 9 genes were not significantly associated with susceptibility to BD.

Elevated levels of MMP-9 and TIMP-1 in the cerebrospinal fluid of neuro-Behçet's disease.

Matrix metalloproteinases (MMP-) are involved in leukocyte invasion into the central nervous system (CNS) during inflammation. In a retrospective cohort study of 18 neuro-BD patients, CSF samples were studied for MMP-9, TIMP-1 and cell characteristics in neuro-BD patients compared to 12 Headache attributed to BD (HaBD) patients, 15 multiple sclerosis (MS) and 20 Non-inflammatory Neurological Disease (NIND) patients. Concentrations of MMP-9 and TIMP-1 were measured in CSF by using an enzyme-linked immunosorbent assay (ELISA). The MMP-9/TIMP-1 ratio was significantly increased in neuro-BD group (mean +/- SD: 0.145+/-0.045) compared to (HaBD) (0.065+/-0.029; p=0.0001) and NIND patients (0.070+/-0.031; p=0.0001). No significant differences were observed between neuro-BD and MS patients. A significant correlation was observed between CSF-PMN cells and MMP-9 in neuro-BD patients (r=0.714; p=0.0009), indicating probably that PMN cells were in part the source of MMP-9. A significantly positive correlation was also observed between MMP-9 and CSF-mononuclear cells in neuro-BD patients (r=0.623; p=0.0012). This is the first study to evaluate the expression of matrix metalloproteinase-9 and tissue inhibitors of metalloproteinase-1 in cerebrospinal fluid of neuro-BD patients. It demonstrates increased matrix metalloproteinase-9/tissue inhibitors of metalloproteinase-1 ratio. The results suggested that MMPs released in the CSF may be involved in the pathogenesis of neuro-BD by promoting local damage, similarly as suspected in other inflammatory diseases.

CTLA-4 +49A/G polymorphism is associated with Behçet's disease in a Tunisian population.

The involvement of excessive T-helper cell functions in the pathogenesis of Behçet's disease (BD) has been reported. Cytotoxic T-lymphocyte antigen-4 (CTLA-4) plays a role in T-cell downregulation. In this report, we investigated the possible association between BD patients and the CTLA-4 +49A/G polymorphism in Tunisian population. A total of 135 Tunisian BD patients and 151 healthy blood donors from the same geographic area were genotyped by polymerase chain reaction for the CTLA-4 +49 A/G polymorphism. A highly significant difference between Tunisian BD patients and healthy controls was found regarding the distribution of CTLA-4 +49 A allele [P < 10(-7); chi(2) = 75.63; odds ratio (OR) = 4.63; 95% confidence interval (CI) = 3.20-6.72] and genotype frequencies (P < 10(-7); chi(2) = 71.02). Furthermore, in the BD group, the A allele was predominant in males (76.3%) when compared with females (62%), (P = 0.014; chi(2) = 5.97; OR = 1.99; 95% CI = 1.10-3.59). No relationship was found between the studied genotype and clinical manifestations. Our results show a gene dose effect of the A allele on the BD. The A allele exerts a stronger effect on disease susceptibility in males compared with females.

Vascular endothelial growth factor gene polymorphisms and serum levels in Behçet's disease.

Vascular endothelial growth factor (VEGF) is important for angiogenesis and inflammation, both of which are codependent and contribute to the pathophysiology of Behçet's disease (BD). In this report, we sought to investigate whether the selected VEGF polymorphisms [-634 C/G, +936 C/T and an 18 bp insertion/deletion (I/D) at -2549 of the VEGF promoter region] are associated with susceptibility and severity of BD in the Tunisian population. One hundred and thirty-five Tunisian BD patients and 157 healthy controls were recruited. The VEGF gene was genotyped by polymerase chain reaction followed by digestion with restriction endonucleases. VEGF serum levels of BD patients and healthy controls were measured by enzyme-linked immunosorbent assay. We found no association between the VEGF polymorphisms and the susceptibility to BD. However, when data were analysed according to the presence of each symptom, we found a positive association between VEGF 18 bp I/D polymorphism and ocular involvement as well as BD severity. Indeed, among the BD patients, the frequency of the 18 bp I/I genotype was less in patients with ocular inflammation (6.1% vs 24.6%, P = 0.007) and in patients with severe BD (9.2% vs 21.4%, P = 0.0014). Moreover, the mean serum VEGF level was considerably higher in BD patients (P < 0.01) than in healthy controls. We suggest that VEGF gene polymorphisms may be involved in the development of the ocular BD as well as the severity of the disease.

Serum BAFF levels and skin mRNA expression in patients with Behçet's disease.

OBJECTIVE: Serum levels of the B-cell activating factor in the tumor necrosis factor family (BAFF), a potent contributor to B-cell survival, are elevated in patients with systemic autoimmune diseases. The objective of this study was to determine serum BAFF levels and to link the results to the clinical features in patients with skin manifestations. METHODS: Serum BAFF levels were examined by an enzyme-linked immunosorbent assay (ELISA) in 42 patients with BD (16 with active disease), 20 healthy controls, and in 20 patients with systemic lupus erythematosus (SLE) and 15 patients with multiple sclerosis (MS), who served as the disease control groups. Expression of BAFF messenger RNA (mRNA) in the skin was quantified by a real-time reverse transcription-polymerase chain reaction; the expression of BAFF receptor (BAFF-R) on CD19+ B cells was assessed by flow cytometry; and ELISA was used to evaluate the production of IgG, interleukin-6 (IL-6) and IL-10 by isolated B cells. RESULTS: Serum BAFF levels were elevated in patients with active BD compared to the healthy controls, and correlated positively with the extent of skin lesions. Disease remission was accompanied by decreased BAFF levels. SLE patients had the highest serum BAFF levels. Skin biopsies showed BAFF mRNA expression to be up-regulated in active BD patients. BAFF-R expression on B cells was increased in BD patients with vasculitis. Furthermore, in BD patients the ability to produce IgG and IL-6 (but not IL-10) was enhanced in BAFF-stimulated B lymphocytes. CONCLUSION: These results suggest that BAFF and its signalling in B cells contribute to B cell abnormalities and the development of skin disease in patients with BD.

A polymorphism in the CCL2 chemokine gene is associated with asthma risk: a case-control and a family study in Tunisia.

Asthma is a complex genetic disorder characterized by chronic airway inflammation. We hypothesized that genetic polymorphisms in chemokines and their receptors alter leukocyte mobilization and may thus influence the risk and severity of childhood asthma. Distributions of the chemokine CCL2-2578G, CCL2-927C, CCR2-V64I, CX3CR1-V249I and CX3CR1-T280M receptor polymorphisms were examined in a case-control study of 121 children with asthma and 226 age-matched healthy controls and then replicated in a family study of 99 simplex families (297 individuals). The case-control study revealed that the CCL2-2578G allele was less frequent in children with than in those without asthma (P=0.0012). No association with asthma was found for the CCL2-927, CCR2 or CX3CR1 polymorphisms. The finding in the family study that the CCL2-2578G allele was transmitted less often by heterozygous parents to their children with asthma (P=0.0016) confirms the association of CCL2-2578G with asthma risk. Biochemical studies indicated that plasma CCL2 concentrations were higher in both patients (P=0.0214) and controls (P=0.001) carrying the G allele than in subjects with other polymorphisms. Both case-control and family-based studies suggest a protective effect of allele CCL2-2578G in Tunisian asthmatic children.

Toll-like receptors and CD14 genes polymorphisms and susceptibility to asthma in Tunisian children.

Many studies have shown the implication of CD14 and toll-like receptors (TLRs) 2, 4 and 9 in the pathogenesis of asthma or atopy. To evaluate the association of CD14 and TLRs gene polymorphisms with asthma or atopy, 210 asthmatic children, 224 controls and 80 families were enrolled in this study. Six single nucleotide polymorphisms TLR2 (+2408 G-->A), TLR4 (+1196 C-->T), TLR4 (+896 A-->G), TLR9 (-1237 T-->C), TLR9 (-1486 T-->C) and CD14 (-159 C-->T) were genotyped using polymerase chain reaction followed by restriction fragment length polymorphism in the case-control and family study. The -1237C allele in TLR9 gene polymorphisms was associated with increased risk of asthma [odds ratio 1.53, 95% confidence interval (1.03-2.27)], although no statistically significant differences in allele or genotype frequencies of four other TLRs polymorphisms were evident between the asthmatic and control groups. The CD14 -159 C allele was found to be significantly higher in the asthmatic group when compared with controls (P=0.0006<0.05). Transmission disequilibrium test of 80 asthmatic families showed significant transmission of the -159 C allele in the CD14 gene to asthma-affected offspring. It was concluded that TLR9 and CD14 gene polymorphisms may contribute to an inherited predisposition to asthma in Tunisian children.

Promoter polymorphism of the IL-18 gene is associated with atopic asthma in Tunisian children.

Several lines of evidence point to a relevant role of IL-18 in the process of asthma. Some studies suggest that the polymorphism in the gene of IL-18 can be involved in many inflammatory and atopic diseases such as asthma. The aim of our study is to estimate the frequency of the IL-18-607 C/A (rs 1946518) promoter polymorphism in Tunisian children with asthma. We investigated whether the presence of this polymorphism -607 C/A was associated with asthma or atopy and whether this polymorphism influenced the severity of asthma in affected children. We examined also the relationship between the IL-18 gene polymorphism and the serum total IgE level. The IL-18/-607 C/A polymorphism was analysed by polymerase chain reaction and restriction fragment-length polymorphism (PCR-RFLP) analysis. A total of 105 asthma patients and 112 controls as part of the whole children population were studied in a case-control study. Among the 105 children with asthma, 40 were also studied for linkage analyses with their respective parents. We noted that the A allele was associated with statistically significant increases in the risk of asthma in the case-control study (odd ratio (OR) = 1.55, 95% confidence interval (CI) 1.03-2.33. Moreover, the A allele was also associated with atopic asthma (P = 0.008), but not with asthma severity. The transmission disequilibrium test (TDT) analysis in this family study did not suggest a preferential transmission of the IL-18/ -607 C/A polymorphism to affected children. There is no correlation between the IgE level and the IL-18 -607 C/A promoter polymorphism. Our data indicate that IL-18 -607 C/A promoter polymorphism is associated with susceptibility to developing asthma in Tunisian population.

Behçet's disease in Tunisia. Demographic, clinical and genetic aspects in 260 patients.

OBJECTIVES: To analyze demographic, clinical and genetic features of Behçet's disease (BD) in Tunisia and to compare them with other ethnic and geographic groups. METHODS: Two hundred and sixty patients with BD (International Study Group criteria) received in the Department of Internal Medicine of the University Hospital La Rabta in Tunisia, from 1987 to 2006, were retrospectively studied. Demographic, clinical, and genetic data were recorded and analyzed using SPSS 11.0. RESULTS: The cohort consisted of 188 males and 72 females (M/F = 2.61). The mean age at the onset of the disease was 29 years. Oral and genital ulcers (GU) were seen in 100% and 83% respectively. The most other common clinical features of BD were ocular involvement (51%), arthritis (38.8%), venous thrombosis (33%) and neuropsychiatric symptoms (24.2%). Only 1.5% had gastrointestinal lesions. HLA-B51 frequency was significantly higher in patients with BD (54% vs. 25.5% in healthy controls, p < 0.05). DVT and pseudofolliculitis were significantly more frequent in men whereas arthritis and erythema nodosum were significantly more frequent in women. DVT was also significantly more frequent in patients with GU and those with neurological involvement. GU, positive pathergy test and DVT were significantly less frequent in patients with ocular involvement. Neurological involvement consisted of 47 cases with CNS parenchymal lesions and 22 with cerebral vascular lesions (13 had both lesions); HLA B51 was significantly less frequent in patients with neurological involvement. CONCLUSION: Our series was characterized by particular aspects such as high frequency of DVT and neuropsychiatric involvement, and rare occurrence of gastrointestinal lesions. The results confirm the ethnic and geographic variation of BD expression.

Paradoxical high regulatory T cell activity in Behçet's disease.

CD4+CD25(bright) T cells and NKT cells are potent immunoregulatory cells and are therefore attractive targets for immunotherapy. The possibility of modulating CD4+CD25(bright) T cell function using NKT cells, and vice versa, reveals a new route for harnessing suppressor T cells with therapeutic properties. However, the questions of where, when and how NKT cells interact with CD4+CD25(bright) T cells are still unknown. Disease studies have investigated the regulatory properties of these T-cell subsets independently of each other. Recent reports have provided evidence for cross-talk between CD4+CD25(bright) T cells and NKT cells and consequently, the immunoregulatory networks are seen in a new perspective. Activated NKT cells seem to modulate quantitatively and qualitatively CD4+CD25(bright) T cell function through IL-2-dependent mechanisms, whereas CD4+CD25(bright) T cells can suppress the proliferation, cytokine release and cytotoxic activity of NKT cells by cell-contact-dependent mechanisms. Importantly, CD4+CD25(bright) T cells and NKT cells share crucial signalling pathways that could be responsible for immune dysregulations in Behçet's disease (BD). The advances in our understanding of the interactions between distinct subsets of regulatory T cells might unveil new waves for modulating these cells with the inflammatory process in BD.

Levels of IL-15 in serum and cerebrospinal fluid of patients with Behçet's disease.

Interleukin-15 (IL-15) is a novel proinflammatory cytokine, involved in the pathogenesis of inflammatory/autoimmune disease. The objective of our study was to measure serum and cerebrospinal fluid (CSF) IL-15 levels in patients with Behçet's disease (BD). CSF/serum IL-15 ratio was introduced to assess the origin of elevated IL-15 levels. We measured serum and CSF-IL-15 levels in 40 patients with BD (20 patients in active stage). Inflammatory and non-inflammatory neurological disease patients acted as controls. Active BD patients have significantly higher serum IL-15 levels (median 10.4 pg/ml; range 5.3-17.4) compared with BD in remission (6.05 pg/ml; 4-10.4) and healthy controls (4.65 pg/ml; 3.9-6.2). Similar serum IL-15 levels were found in active neuro-BD and inflammatory neurological disease (9.5 pg/ml; 5-13). Elevated levels of IL-15 were observed in CSF samples from neuro-BD patients (11 pg/ml; 8.5-15) and inflammatory neurological disease patients (10 pg/ml; 6.5-14) compared with patients with non-inflammatory neurological disease (4 pg/ml; 4-5.5; P < 0.001). Vascular cerebral BD lesions were associated with high CSF/serum IL-15 ratio. Our findings suggest that IL-15 is involved in BD inflammatory process, particularly in vasculitis foci, as an elevated CSF/serum IL-15 ratio characterizes vascular cerebral lesions.

CD4+CD25+ regulatory T cells in patients with Behçet's disease.

OBJECTIVE: To investigate whether the CD4+CD25+ regulatory T cell (Treg) population, which plays important role in autoimmune diseases is related to the pathophysiology of Behçet's disease (BD). METHODS: Forty-two patients with BD (20 patients in active disease) fulfilling the criteria of the International Study Group of BD. Twenty age-matched healthy controls were studied. We analyzed CD4+CD25+/high T cells and the mRNA expression of Foxp3, cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), and transforming growth factor beta (TGF-beta) in BD. We have studied the ability of CD4+CD25+ (Treg) to regulate proliferation of CD4+CD25- T cells during active BD stage. RESULTS: Active BD patients had significantly higher CD4+CD25+/high T cells, as compared with BD in the remission stage, and healthy controls. There was no significant differences in the CD4+ CD25+/high T cells expression between healthy controls and remission BD. In active BD, mRNA for Forkhead box p3 (Foxp3) and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) were highly expressed when compared to remission BD and healthy controls. There was no differences in the mRNA expression for TGF-beta in active BD, remission BD and healthy controls. Functionally, CD4+CD25+/high T cells in active BD were impaired in their proliferative responses and could suppress the proliferation of their CD4+CD25- counterparts. CONCLUSION: These data demonstrate that CD4+CD25+ Treg cells, with the potential to regulate suppression of effector T cells, were increased in the peripheral circulation of active BD patients. The role of CD4+CD25+/high T cells in the regulatory process of the inflammation in active BD, could be taken in account.

Promising new therapies for Behcet's disease.

Improved understanding of the pathogenic mechanisms of Behcet's disease (BD), and especially of the molecular basis involved in its pathogenesis, has sparked a new generation of potential BD treatments with improved side effect profiles and/or more specific targeting of the immune system. These therapies include new immunosuppressants, biologic medications, tolerizing agents, and immunoablation techniques, a number of which are currently in use in clinical practice (interferons). While some of these new therapies target specific inflammatory mechanisms in SLE (tumor necrosis factor-alpha inhibitors), others work by non-specific inhibition of the immune system (immunoablation). Each of these approaches will be discussed in this review.

Circulating soluble CD28 in patients with Behçet's disease: relationship to clinical manifestations.

OBJECTIVE: This study evaluates the presence of serum soluble CD28 (sCD28) in Behçet's disease (BD) and its relationship with clinical manifestations. METHODS: Soluble CD28 concentration was determined by ELISA in 120 patients with BD (80 patients in active stage), 60 patients with rheumatoid arthritis (RA) and 60 healthy subjects. RESULTS: Concentrations of sCD28 were significantly higher in patients with BD and RA than in healthy subjects. Patients with active BD expressed the highest level of sCD28 in serum. Soluble CD28 exhibited a drastic increase in active BD patients, compared to BD in remission. Soluble CD28 concentrations were higher in patients with active BD patients having vasculitis. Significant positive correlation was observed in a longitudinal study of 15 BD patients, between sCD28 and C-reactive protein. CONCLUSION: Our study suggests that fluctuations of sCD28 in BD reflects disease activity and should be assessed in evaluating disease activity.

[Pulmonary complications of Behcet's disease and Takayasu's arteritis]. / Manifestations thoraciques des maladies de behçet et de Takayasu.

INTRODUCTION: Behçet's disease and Takayasu's arteritis are both forms of large vessel vasculitis involving autoreactive T cells active against HSP 60. STATE OF THE ART: Behçet's disease is more common than Takayasu's arteritis. Pulmonary aneurysms represent the major complication of pulmonary Behçet's disease and have a poor prognosis, being associated with massive haemoptysis. In situ pulmonary artery thrombus can lead to pulmonary infarction. Superior vena cava thrombosis progresses slowly, allowing the development of a prominent collateral circulation. Vascular inflammation can spread to the mediastinum, the pleura and the lungs with diffuse pulmonary haemorrhages, bronchiolitis and organising pneumonia. Electron beam tomodensitometry and MRI are the best diagnostic techniques for assessing pulmonary vascular lesions. In Takayasu's arteritis the pulmonary arteries are less frequently involved than the aorta. Pulmonary hypertension (PHT) and lung infarcts can complicate pulmonary arterial involvement and the association of malaise, fever and weight loss with PHT is characteristic of the disease. The diagnosis is confirmed by imaging means, particularly MRI, demonstrating parietal vascular inflammation. CONCLUSION: Treatment of both conditions is based upon steroids and immunosuppression. Endovascular treatment may be used in a complementary way for aneurysms, arterial occlusion, and vena cava obstruction. However, patients often respond poorly to treatment and clinical trials using TNFalpha blockade, interferon alpha and vasodilators are in progress.