Marcus Krueger

Sequence variants affecting eosinophil numbers associate with asthma and myocardial infarction

Eosinophils are pleiotropic multifunctional leukocytes involved in initiation and propagation of inflammatory responses and thus have important roles in the pathogenesis of inflammatory diseases. Here we describe a genome-wide association scan for sequence variants affecting eosinophil counts in blood of 9,392 Icelanders. The most significant SNPs were studied further in 12,118 Europeans and 5,212 East Asians. SNPs at 2q12 (rs1420101), 2q13 (rs12619285), 3q21 (rs4857855), 5q31 (rs4143832) and 12q24 (rs3184504) reached genome-wide significance (P = 5.3 × 10−14, 5.4 × 10−10, 8.6 × 10−17, 1.2 × 10−10 and 6.5 × 10−19, respectively). A SNP at IL1RL1 associated with asthma (P = 5.5 × 10−12) in a collection of ten different populations (7,996 cases and 44,890 controls). SNPs at WDR36, IL33 and MYB that showed suggestive association with eosinophil counts were also associated with atopic asthma (P = 4.2 × 10−6, 2.2 × 10−5 and 2.4 × 10−4, respectively). We also found that a nonsynonymous SNP at 12q24, in SH2B3, associated significantly (P = 8.6 × 10−8) with myocardial infarction in six different populations (6,650 cases and 40,621 controls).

A sequence variant on 17q21 is associated with age at onset and severity of asthma

A sequence variant (rs7216389-T) near the ORMDL3 gene on chromosome 17q21 was recently found to be associated with childhood asthma. We sought to evaluate the effect of rs7216389-T on asthma subphenotypes and its correlation with expression levels of neighboring genes. The association of rs7216389-T with asthma was replicated in six European and one Asian study cohort (N=4917 cases N=34 589 controls). In addition, we found that the association of rs7216389-T was confined to cases with early onset of asthma, particularly in early childhood (age: 0–5 years OR=1.51, P=6.89·10−9) and adolescence (age: 14–17 years OR=1.71, P=5.47·10−9). A weaker association was observed for onset between 6 and 13 years of age (OR=1.17, P=0.035), but none for adult-onset asthma (OR=1.07, P=0.12). Cases were further stratified by sex, asthma severity and atopy status. An association with greater asthma severity was observed among early-onset asthma cases (P=0.0012), but no association with sex or atopy status was observed among the asthma cases. An association between sequence variants and the expression of genes in the 17q21 region was assessed in white blood cell RNA samples collected from Icelandic individuals (n=743). rs7216389 associated with the expression of GSDMB and ORMDL3 genes. However, other sequence variants showing a weaker association with asthma compared with that of rs7216389 were more strongly associated with the expression of both genes. Thus, the contribution of rs7216389-T to the development of asthma is unlikely to operate only through an impact on the expression of ORMDL3 or GSDMB genes.

TLR-4 and CD14 Polymorphisms in Respiratory Syncytial Virus Associated Disease

Respiratory syncytial virus (RSV) is the most common viral respiratory pathogen during infancy world wide. It induces innate and adaptive immune response in host cells. The toll like receptor 4 (TLR4)/CD14 complex is particularly important for the initiation of an innate immune response to RSV. Thus we were interested whether an association exists between severe RSV associated diseases and polymorphisms within TLR4 and CD14. We genotyped the CD14 promotor polymorphism -C159T and the two common TLR4 amino acid variants (D259G, and T359I) in 131 infants with severe RSV associated diseases and 270 controls. Statistical analyses of single polymorphisms made use of the Armitage’s trend test, haplotypes were calculated by FAMHAP, FASTEHPLUS and Arlequin. All polymorphisms were in Hardy Weinberg Equilibrium. We found marginal association between amino acid exchange D259G in TLR4 with RSV infection p = 0.0545). Furthermore, haplotypes analysis of the two TLR4 polymorphisms by three independent programs revealed association of haplotypes with severe RSV infection (p ≤ 0.0010). In contrast, the promotor polymorphism within CD14 was not associated with susceptibility to RSV disease. We conclude from our study, that TLR4 polymorphisms, and particularly the haplotypes, may influence the genetic predisposition to severe RSV infection.

Impact of IL8 and IL8-Receptor alpha polymorphisms on the genetics of bronchial asthma and severe RSV infections

BackgroundInterleukin 8 (IL8) belongs to the family of chemokines. It mediates the activation and migration of neutrophils from peripheral blood into tissue and hereby plays a pivotal role in the initiation of inflammation. Thus it is important in inflammatory lung diseases like bronchial asthma or severe infections by Respiratory Syncytial Virus (RSV). IL8 acts through binding to the IL8-Receptor alpha (IL8RA). For both genes association with asthma has been described. In addition, IL8 has been found in association with RSV bronchiolitis. The aim of our study was to test both genes for association with asthma and severe RSV infections. In addition we were interested in whether a common genetic background of both diseases exists in regards to these genes.MethodsWe genotyped the two IL8 promotor polymorphisms -251A/T and -781C/T and the three amino acid variants M31R, S276T and R335C in IL8RA on 322 children with asthma, 131 infants with severe RSV associated diseases and 270 controls. Statistical analyses made use of the Armitages trend test for single polymorphisms and FAMHAP for calculations of haplotypes.ResultsWe found association of the IL8 polymorphism -781C/T as well as IL8 haplotypes with asthma (p = 0.011 and p = 0.036, respectively). In addition, direct comparison of the asthmatic population with the RSV population revealed significant differences, both for -781C/T alone (p = 0.034) and IL8 haplotypes (p = 0.005). The amino acid variants in IL8RA were evenly distributed in between all three populations.ConclusionWe conclude from our data that IL8 might play a role in the genetic predisposition to asthma and that these effects are different or even opposite to the effects on severe RSV diseases. Furthermore, IL8RA is unlikely to play a major role in the genetics of either disease.

Surfactant protein B polymorphisms are associated with severe respiratory syncytial virus infection, but not with asthma

BackgroundSurfactant proteins (SP) are important for the innate host defence and essential for a physiological lung function. Several linkage and association studies have investigated the genes coding for different surfactant proteins in the context of pulmonary diseases such as chronic obstructive pulmonary disease or respiratory distress syndrome of preterm infants. In this study we tested whether SP-B was in association with two further pulmonary diseases in children, i. e. severe infections caused by respiratory syncytial virus and bronchial asthma.MethodsWe chose to study five polymorphisms in SP-B: rs2077079 in the promoter region; rs1130866 leading to the amino acid exchange T131I; rs2040349 in intron 8; rs3024801 leading to L176F and rs3024809 resulting in R272H. Statistical analyses made use of the Armitages trend test for single polymorphisms and FAMHAP and FASTEHPLUS for haplotype analyses.ResultsThe polymorphisms rs3024801 and rs3024809 were not present in our study populations. The three other polymorphisms were common and in tight linkage disequilibrium with each other. They did not show association with bronchial asthma or severe RSV infection in the analyses of single polymorphisms. However, haplotypes analyses revealed association of SP-B with severe RSV infection (p = 0.034).ConclusionThus our results indicate a possible involvement of SP-B in the genetic predisposition to severe RSV infections in the German population. In order to determine which of the three polymorphisms constituting the haplotypes is responsible for the association, further case control studies on large populations are necessary. Furthermore, functional analysis need to be conducted.

Association of TNF-α with severe respiratory syncytial virus infection and bronchial asthma

Tumor necrosis factor (TNF‐)α is a proinflammatory cytokine that is important in the innate host defence and thus in the defence of infectious agents. However, in excess it provokes the development of chronic inflammatory diseases. The aim of this study was to test association of TNF with severe RSV bronchiolitis as example of an infectious disease and asthma as representative for a chronic inflammatory condition. The following study populations were genotyped for 4 polymorphisms within TNF‐β (rs909253) and TNF‐α (rs1799964, rs1799724, rs1800629): 322 asthmatic children, 151 children with severe respiratory syncytial virus (RSV) bronchiolitis and 270 controls. Furthermore, serum TNF‐α levels were measured by a FlowCytomix Assay. Asthma showed association with two TNF‐α polymorphisms as well as with TNF haplotpyes (p = 0.0050). In contrast, RSV bronchiolitis was associated with TNF haplotypes (p < 0.00001) but not with any single polymorphism. In addition, TNF‐α serum levels correlated with rs1799724 (p = 0.034). A genetically mediated up‐regulation of TNF‐α expression might provoke a pronounced inflammation of the airways and thus a more severe course of RSV infection as well as the onset of asthma. It remains to be elucidated whether severe RSV bronchiolitis starts TNF‐α upregulation and is one first step in the direction to asthma later in life, or whether both dieases are independent from each other and supported by TNF‐α upregulation.

Interleukin (IL)-18 Polymorphism 133C/G Is Associated With Severe Respiratory Syncytial Virus Infection

Background: Respiratory syncytial virus (RSV) is a major cause of bronchiolitis in infants. During the course of RSV infection, predominant T helper cell (TH) 2 response is associated with disease progression, whereas predominant TH1 reaction provides convalescence. Interleukin (IL)-18 plays an important role in adjusting the TH1/TH2 immune response to viral infections. Thus, we tested the hypothesis that polymorphisms in IL-18 were associated with severe RSV-associated diseases. Methods: We chose to study the promotor polymorphisms −607A/C (rs1946518) and −137G/C (rs187238), the 2 exon polymorphisms 113T/G (rs360718) and 127C/T (rs360717), and 2 intron polymorphisms 5304A/G (rs795467) and 133G/C (rs360721) within the IL-18 gene. Genotyping was performed on 154 children with severe RSV infection as defined by strict clinical criteria and on 270 controls. Statistical analyses of single polymorphisms made use of the Armitages trend test, haplotypes were calculated with FASTEHPLUS and FAMHAP. Results: −133G/C showed association with severe RSV infection (P = 0.043). The association was further supported by haplotype analyses with all 6 polymorphisms (P < 0.00001 for association with RSV). Conclusions: This study indicates possible involvement of IL-18 in the determination of severe RSV-associated diseases. Defining the genetic basis of RSV bronchiolitis might help us in identifying new drug targets for a more specific therapy. In addition, it might enable an early identification of children at risk for RSV bronchiolitis and thus make a selective prevention feasible.

Lipopolysaccharide binding protein is a potential marker for invasive bacterial infections in children.

Background: The aim of this study was to test the hypothesis that elevated lipopolysaccharide binding protein (LBP) serum concentration is a useful marker in the early diagnosis of invasive bacterial infection in children. We measured LBP in serum and cerebrospinal fluid (CSF) of children with proven invasive infection caused by Haemophilus influenzae, Streptococcus pneumoniae and Neisseria meningitidis. Patients and Methods: Samples were collected from 39 children (aged 2 months to 17 years) with bacterial sepsis (n = 19) or meningitis (n = 20). Bacterial infection was diagnosed when a blood or CSF culture was positive and clinical signs of invasive infection were present. The control group consisted of serum (n = 60) and CSF (n = 19) samples from children with neurologic disease, juvenile idiopathic arthritis or viral infection. In 10 patients with bacterial infection, follow-up samples (24 and 48 hours) were available. LBP values were measured by an immunochemiluminescence analyzer (IMMULITE; DPC Biermann, Bad Nauheim, Germany) and compared with tumor necrosis factor-α and interleukin-8 concentrations. Results: The median LBP serum concentrations in patients with bacterial infection were markedly elevated compared with the control groups (45.0 [33.1–55.2] versus 8.3 [6.8–10.1] &mgr;g/mL [median and 5–95% confidence interval]; P < 0.0001). Follow-up serum values of LBP were persistently elevated despite adequate antibiotic treatment, whereas tumor necrosis factor-α and interleukin-8 concentrations decreased. In contrast, LBP concentrations in the CSF were below the detection limit of 0.5 &mgr;g/mL in 67% of patients with bacterial meningitis (median <0.5 &mgr;g/mL), whereas tumor necrosis factor-α and interleukin-8 levels were highly elevated. Conclusion: LBP serum concentration is elevated in serum of children with invasive bacterial infection and could be a promising diagnostic marker.

Polymorphisms of toll like receptors in the genetics of severe RSV associated diseases.

Toll like receptors (TLRs) are an essential part of the innate immune response. So far, ten different TLRs were identified in humans. They recognize a wide range of microbial and viral pathogens. Infection by respiratory syncytial virus (RSV) is still a major health problem, about 2% of all children are hospitalised due to RSV bronchiolitis during their first 2 years of live. TLR4 has already been described in association with RSV associated diseases by us and others. Thus we were interested whether other TLRs are also involved in the genetics of severe RSV infection. We genotyped 19 polymorphisms in the autosomal TLRs, these are TLR1, 2, 3, 5, 6, 9 and 10. Association analyses by the Armitages Trend test revealed weak association of one TLR9 promoter polymorphism with RSV infection (p = 0.013). In addition, association was found with TLR10 haplotypes (p = 0.024). We conclude from our data – that – although we can not rule out a minor involvement of TLR9 polymorphism and TLR10 haplotypes – TLRs other than TLR4 do not play a major role in the genetics of severe RSV associated diseases. Future studies should focus on additional genes of the innate immune response.

Haplotypes of surfactant protein C are associated with common paediatric lung diseases.

Surfactant protein C is part of the surfactant complex lining up the alveoles and thereby inhibiting collapse of the airways. In addition it is involved in innate immune responses. Rare polymorphisms within surfactant protein C have been linked to sporadic paediatric lung diseases, like proteinosis or interstitial lung diseases. One study in the Finnish population described association of common polymorphisms with neonatal respiratory syndrome. Other common lung diseases have not yet been investigated for association with this gene. The aim of this study was to test surfactant protein C for association with bronchial asthma and with severe respiratory syncytial virus associated diseases in infancy. The two common amino acid variants Asn138Thr and Asn186Ser were genotyped on 322 children with asthma, 131 children with severe respiratory syncytial virus associated diseases and 270 controls. Statistical analyses of single polymorphisms made use of the Armitages trend test; haplotypes were calculated with FAMHAP and FASTEHPLUS. Polymorphisms were in Hardy–Weinberg equilibrium and in tight linkage equilibrium in all populations. Single polymorphisms showed no association with the diseases, however, surfactant protein C haplotypes were associated with severe respiratory syncytial virus associated diseases (p = 0.013). Furthermore, an inverse haplotype distribution was found between children with asthma and respiratory syncytial virus infection (p = 0.00025). The results of our study might suggest opposing roles of surfactant Protein C in the genetic predisposition for respiratory syncytial virus associated diseases vs. asthma. The causal mechanism for this observation has still to be shown.