A European study on the genetics of mite sensitization

BACKGROUND

Sensitization to mite allergens represents a prominent feature of atopy and an important predictor of bronchial asthma.

OBJECTIVE

It was the intention of this study to define genetic loci linked to mite sensitization because these could represent the genetic basis of the important atopic component of asthma.

METHODS

We studied a multiethnic white population of 99 families, including 224 sib pairs sensitized to Dermatophagoides pteronyssinus. A genome-wide candidate-region search was performed that covered potential asthma and atopy regions.

RESULTS

As for nonparametric linkage (NPL) analysis, 14 of the candidate regions showed evidence for linkage (NPL > 2.0), and 4 of them showed prominent linkage (NPL > 3.0). However, there were substantial ethnic differences. Maximizing the LOD score analysis identified candidate regions with suspected dominant and recessive mode of inheritance. Furthermore, genetic imprinting models provided significant evidence for linkage in the 8p23 region and revealed potential maternal imprinting. The regions found are distinct to those in asthma searches that have been found to be linked to asthma, as well to other inflammatory diseases. In addition, we could not find linkage to the HLA region. By different cutoff points of the phenotype definition, the IL cluster showed evidence of being linked to the degree of sensitization rather than to sensitization per se.

CONCLUSION

The results indicate that the genetic basis of the atopic component of asthma is different from that of the inflammatory component. Furthermore, it seems reasonable to assume that specific sensitizations are influenced by distinct genetic variants leading to their initiation versus those leading to their enhancement.

Association and linkage of atopic dermatitis with chromosome 13q12-14 and 5q31-33 markers

Atopic dermatitis is a chronic inflammatory skin disease that affects 10-20% of the population. Linkage of atopy, asthma, allergic rhinitis, and total serum IgE levels to several different chromosomal regions have been described extensively, but little is known about the genetic control of atopic dermatitis. We tested for the association and linkage between atopic dermatitis and five chromosomal regions: 5q31-33, 6p21.3, 12q15-24.1, 13q12-31, and 14q11.2/14q32.1-32.3. Marker analysis was performed in two Caucasian populations: (i) 192 unrelated German children with atopic dermatitis and 59 non-atopic children from a German birth cohort study (MAS'90), parental DNA was tested in 77 of 192 children with atopic dermatitis; (ii) 40 Swedish families with at least one family member with atopic dermatitis selected from the International Study of Asthma and Allergy in Children. Evidence for linkage and allelic association for atopic dermatitis was observed for markers on chromosome 13q12-14 and 5q31-33.

Studies on linkage and association of atopy with the chromosomal region 12q13-24

BACKGROUND

Several studies have shown linkage of bronchial asthma, allergic rhinitis and total serum IgE concentration to the chromosomal region 12q13-24 in ethnical diverse populations. This region harbours a number of candidate genes for asthma and atopy, including stem cell factor (SCF), leukotriene A4 hydrolase (LTA4H), thyroid receptor 2 (TR2), and signal transducer and activator of transcription 6 (STAT6). However, the same region was shown as well to be linked to other diseases with inflammatory character. So far no variants in any of these genes have been published which would allow association studies and confirm the pathogenicity of any of these genes.

OBJECTIVE

We wanted to test for linkage of the chromosomal region 12q13-24 with the atopic phenotype without regard to clinical manifestations. Furthermore we screened for common nucleotide polymorphisms in candidate genes to enable association studies.

METHODS

We employed sib-pair linkage analysis and transmission disequilibrium testing with regard to four highly polymorphic microsatellite markers in 12q13-24 in atopic nuclear families. In addition, we looked for polymorphisms in the genes coding for SCF, LTA4H, TR2 and STAT6 performing SSCP-analysis and direct genomic sequencing.

RESULTS

We found no evidence for linkage of the genomic region 12q13-24 to elevated total serum IgE levels, specific sensitization to common inhalant allergens or atopy. Furthermore we identified three nucleotide polymorphisms including one common variant in the gene coding for SCF. No association of this polymorphism and any of the atopic phenotypes was seen.

CONCLUSION

We conclude from our data that genes in the chromosomal region 12q13-24 and in particular SCF are unlikely to exert a major effect on the induction of the atopic phenotype in our Caucasian population. However, we did not focus on the asthmatic and thereby inflammatory aspect of atopy which might explain these results in contradiction to previous studies.

Common polymorphisms and alternative splicing in the ILT3 gene are not associated with atopy

Recently, a linkage of the chromosomal region 19q13.4 with bronchial asthma has been demonstrated. This region harbours the so-called leucocyte receptor cluster with the gene for immunoglobulin-like-transcript 3 (ILT3) as a member. ILT3 represents an inhibitory receptor bearing three immunoreceptor tyrosine inhibitory motifs (ITIM). The protein mediates downregulation of cell activation through recruitment of different SH2-containing protein tyrosine phosphatases. With regard to the negative immunoregulatory function particularly on B-cells, ILT3 represents a candidate gene for atopy and asthma. The aim of this study was to screen for common polymorphisms in the gene coding for ILT3 and to test for association with the atopic phenotype. Using single-stranded conformal polymorphism-analysis and direct genomic sequencing seven polymorphisms, three mutations, a common deletion of 7 bp in the third intron and evidence for further alternative splicing of the ILT3 gene were found. Although no association was found with atopy phenotypes, it might prove useful to test for association with bronchial asthma.

The Ile198Thr and Ala379Val variants of plasmatic PAF-acetylhydrolase impair catalytical activities and are associated with atopy and asthma

The platelet-activating factor (PAF) represents a phospholipid with complex biological functions, including involvement in inflammatory processes. The degrading enzyme PAF acetylhydrolase (PAFAH) represents a candidate for asthma and other atopic diseases. Two loss-of-function mutations of PAFAH are associated with severe asthma in Japanese individuals. Our aim was to look for further PAFAH variants in white populations, their possible association with atopic and asthmatic phenotypes, and their functional importance. We picked up three common variants in the PAFAH gene: Arg92His (exon 4), Ile198Thr (exon 7), and Ala379Val (exon 11). The known loss-of-function mutations were not seen. The variant allele Thr198 was found to be highly associated with total IgE concentrations in an atopic population (P=.009) and with "atopic asthma" in an asthmatic population (P=.008). The variant allele Val379 was found to be highly associated with "specific sensitization" in the atopic population (P=.002) and with "asthma" in the asthmatic population (P=.003). By use of recombinant PAFAH enzymes, the variant Val379 showed increased (14 microM) and Thr198 markedly increased (42 microM) KM values compared to the wild type (7 microM); furthermore, Vmax of Val379 was highly increased (132%). Thr198 and Val379 influence plasmatic PAFAH toward lower substrate affinities and therefore are very likely to prolong the activities of PAF. At the same time, they are associated with an increased risk to develop asthma and atopy. Thus, two PAFAH variants seem to play a key role in atopic and asthmatic processes in Caucasian populations.

Increased left ventricular mass index and nocturnal systolic blood pressure in patients with Type 2 diabetes mellitus and microalbuminuria

AIMS

To compare left ventricular mass (LVM) index and function in patients with Type 2 diabetes mellitus with and without microalbuminuria and to investigate the clinical determinants of left ventricular hypertrophy.

METHODS

Echocardiography, electrocardiography and 24-h ambulatory blood pressure monitoring were performed in microalbuminuric (n = 29) and normoalbuminuric (n = 29) patients with Type 2 diabetes and no clinical evidence of heart disease. Groups were individually matched for age, sex and diabetes duration and smoking status.

RESULTS

LVM index (62 (34-87) vs. 52 (33-89) g/m2.7, P = 0.04) and LVH prevalence, using two out of three definitions, were greater in patients with microalbuminuria (LVM/height2.7: 72 vs. 59%, P = 0.27, LVM/height: 66 vs. 38%, P = 0.04, LVM/body surface area: 59 vs. 31%, P = 0.03). Night-time systolic blood pressure (126 (99-163) vs. 120 (104-157) mmHg, P = 0.005) and the night/day systolic blood pressure ratio (0.92 (0.08) vs. 0.88 (0.06), P = 0.04) were higher in those with microalbuminuria. Systolic and diastolic function were similar in both groups. Linear regression analyses showed that body mass index (BMI) was significantly related to loge LVM index (R2 = 11.8%, P = 0.005) and a relationship with night/day systolic blood pressure was also suggested (R2 = 4.6%, P = 0.057).

CONCLUSIONS

In patients with Type 2 diabetes, LVH is more common and severe in those with microalbuminuria. Its presence may be related to raised night/day systolic blood pressure ratio and is significantly related to BMI. The high prevalence of LVH strengthens the case for echocardiographic screening in Type 2 diabetes to identify high risk patients who might benefit from aggressive cardiovascular risk factor intervention.

Common polymorphisms in the CTLA-4 and CD28 genes at 2q33 are not associated with asthma or atopy

Recently, genetic linkage of the chromosomal region 2q33 with asthma has been shown. The genes coding for CD28 and CTLA-4 have been localized to this chromosomal region. CD28 and CTLA-4 have been shown to be involved as an important costimulatory signal in the regulation of allergic inflammation and TH2 cytokine production, and thus both genes are good candidate genes for asthma and atopy. Two common polymorphisms in the CTLA-4 gene and one polymorphism in the CD28 gene found by single-strand conformation polymorphisms (SSCP) analysis and direct genomic sequencing were tested for association with asthma and atopy phenotypes in a population of 260 largely atopic children and young adults. No association was found between any of the three polymorphisms and asthma or atopy phenotypes. The newly described common CD28 polymorphism is situated in the third intron of the gene. We conclude that neither gene is likely to exert a major influence on the development of asthma or atopy in our population. However, it might prove useful to test for association of these polymorphisms with asthma in populations recruited through asthmatic but not necessarily atopic individuals.

[Prospective study of JCR-Oligo I of the Child and Adolescence Rheumatology Working Group]

Intra-articular injection of corticosteroids is a powerful anti-inflammatory treatment with relatively few side effects. To date no prospective RCT exists on its use in children with oligoarthritis type I. Thus, in January 2000 the Arbeitsgemeinschaft started a multicenter RCT to compare in children with this diagnosis the initial treatment recommended in the textbooks, which is NSAID plus physiotherapy, with the early use of intra-articular injection of Triamcinolonhexacetonide. In the synovial fluid the presence of cytokines and the specific reactivity of T cells will be explored, and a highly sensitive screening for infectious agents will be performed.

Q methodology, risk training and quality management

The results of a Q methodological study of professional understandings of the notion of risk in mental health services within the UK are discussed in relation to the relevance for staff training and quality assurance. The study attempted to access the diversity of understandings of risk issues amongst a multi-professional group of staff (n = 60) attending inter-agency risk training workshops in 1998. Q methodology is presented as both an appropriate means for such inquiry and as a novel experiential technique for training purposes. A tentative argument is advanced that the qualitative accounts generated by Q research could assist in systematic reviews of quality, complementing the singularly quantitative approaches typically represented in the audit process.

Elevated gene expression of interleukin-8 in cord blood is a sensitive marker for neonatal infection

Bacterial infection is a major cause of neonatal morbidity and mortality. Early diagnosis is essential for a successful treatment and outcome. Cytokine plasma levels are suggested to be sensitive parameters for the diagnosis of neonatal sepsis. The aim of this study was to assess cytokine mRNA expression in cord blood cells as a marker for neonatal infection. In a prospective study, cord blood samples of neonates with septic bacterial infection were analyzed qualitatively and semiquantitatively by reverse transcriptase-polymerase chain reaction (RT-PCR) for mRNA expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, IL-8, as well as for IL-8 cord plasma levels. Results were compared to those of non-septic neonates. A method was used requiring only a microvolume (25 microl or less) of cord blood. Cord plasma levels of IL-8 were significantly elevated in septic infants (n = 9) when compared to infants with not confirmed sepsis (n = 22) and healthy infants that served as controls (n = 68) (median 1,686 vs 262.7 vs 33.1 pg/ml, P < 0.001). The presence of IL-6 and TNF-alpha gene expression was observed more frequently in septic than in non-septic patients; sensitivity, however, reached only 56 and 67%, respectively. When using a semiquantitative approach for analyzing IL-8 mRNA levels, a high sensitivity (86%) and specificity (96%) for the detection of sepsis was achieved. A new method for the early diagnosis of neonatal infection is described measuring cytokine mRNA in neonatal cord blood cells. With this molecular approach only a microvolume of blood is required for analysis.

Characterization of the membrane-bound and a soluble form of human IL-4 receptor alpha produced by alternative splicing

IL-4 plays a major role in IgE production. Its signal is conferred to effector cells through binding to the alpha chain of the membrane-bound human IL-4 receptor (huIL-4Ralpha). Here we present the genomic structure and organization of huIL-4Ralpha. The promotor region shows binding sites for several transcription factors involved in inflammatory processes. HuIL-4Ralpha has been shown to be organized differently to that of mouse IL-4Ralpha. A soluble form of huIL-4Ralpha is produced by alternative splicing of the huIL-4Ralpha gene (shuIL-4Ralpha/splice). Expression of the corresponding mRNA coding for the extracellular part of the receptor and an additional three amino acids is also shown. A second form of huIL-4Ralpha, i.e. shuIL-4Ralpha/prot, is produced by limited proteolysis of the receptor (shedding) and is already known. These results reveal a complex pattern for the regulation of the IL-4 pathway at the receptor level. The patterns of expression of all three receptor proteins as well as their individual meaning in the context of inflammation still have to be elucidated.

The recognition pattern of sequential B cell epitopes of beta-lactoglobulin does not vary with the clinical manifestations of cow's milk allergy

BACKGROUND

beta-Lactoglobulin (BLG) represents one of the major allergens causing cow's milk allergy (CMA) - a disease with a wide spectrum of clinical symptoms. The aim of this study was to evaluate sequential B cell epitopes of BLG by the Pin-ELISA method. Furthermore, we wanted to investigate a possible association of the IgE recognition patterns in sera of patients with BLG sensitization and the type of clinical reactions following contact with cow's milk.

METHODS

Overlapping sequential decapeptides corresponding to the amino acid sequence of BLG were used in Pin-ELISAs specific for human IgE. Tested sera were from 14 individuals with CMA, 8 of them with a history of immediate systemic reactions and 6 with delayed skin reactions following contact with cow's milk. All of them showed specific IgE antibodies to BLG in the CAP-RAST. Control sera were from 5 healthy nonallergic individuals.

RESULTS

All sera from BLG-sensitized individuals showed IgE binding with one region of BLG corresponding to amino acids 95-113. Furthermore, individual sera showed reactions with two further regions, 12-27 and 124-135. Inhibition of IgE binding to BLG with one soluble synthetic peptide confirmed the major epitope. No differences were found in the B cell epitope recognition pattern to BLG in the two groups of patients with CMA, characterized by acute systemic or delayed skin reactions.

CONCLUSIONS

Using IgE Pin-ELISAs we were able to confirm previously described sequential B cell epitopes of BLG. However, the recognition pattern of one of the major cow's milk allergens is not predictive of the clinical type of reaction.

Pulmonary function in children of school age is related to the number of siblings in their family

It has been suggested that the number of siblings in a family is a surrogate variable for exposure to early infections. Since there may be an association between early respiratory infections and impaired lung function in later life, the aim of this study was to elucidate the relationship between the number of siblings and pulmonary function. We analyzed pulmonary function data from 677 schoolchildren living in 431 nuclear families. Our results show that forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV(1)) expressed as a percentage of deviation from the predicted values (FVC%, FEV(1)%) increase significantly in line with the number of siblings in a family (FVC%: no sibling = reference, 1 sibling = +1.3%, 2 siblings = +1.9%, 3 siblings = +4.0%, 4 or more siblings = +5.1%; P-value for trend = 0.01; FEV(1)%: no sibling = reference, 1 sibling = +1.6%, 2 siblings = +2.0%, 3 siblings = +4.3%, 4 or more siblings = +6.5%; P-value for trend = 0.007). Pulmonary function values were no more strongly related to the number of older siblings than to the number of younger siblings (difference between the trend for older and younger siblings for FCV%: P = 0.7; FEV(1)%: P = 0.9). The association between pulmonary function and number of siblings can be explained neither by the child's atopic status, prevalence of asthma, or history of pneumonia, nor by former or current cigarette smoke exposure. This suggests that pulmonary function status of the child appears to be related to the number of siblings, and is unlikely to be explained solely by exposure to infections early in life. Our data therefore adds strength to the hypothesis that factors which cause the size of a sibship to influence a child's respiratory health have not yet been adequately explained.

Upper airway inflammation in children exposed to ambient ozone and potential signs of adaptation

In order to investigate nasal inflammation and subsequent adaptation after ambient ozone exposure, nasal lavage (NL) fluid was collected from 170 schoolchildren on 11 occasions (time points) between March and October. Eosinophil cationic protein (ECP), albumin and leukocytes were quantified as markers of nasal inflammation. The highest half-hour outdoor O3 concentration for each individual on the day prior to the NL was used as a measure of exposure (O3indiv). To avoid confounding with exposure to common environmental allergens, the study population was restricted to children without sensitization to inhalant allergens. In the initial period of increased O3 levels in May (time point 4), with a median O3indiv of 135 microg x m(-3) (5th-95th percentile 100-184 microg x m(-3)), the highest medians of all 11 leukocyte and ECP measurements were observed. The highest O3indiv were observed in June at time point 7 (O3indiv 173 microg x m(-3), 5th-95th percentile 120-203 microg x m(-3)). Cross-sectional analysis of all 11 time points revealed no significant association of O3indiv on the one hand and ECP, albumin and leukocyte levels on the other. A multivariable model estimated using generalized estimating equations showed a statistically significant association of O3indiv and leukocytes and ECP as the dependent variable, when time points 1-4 were analysed (p<0.05). In the same model, this association diminished continuously when time points 5-11 were added stepwise, in spite of high O3 exposure. Not even a tendency towards an O3 effect could be recognized when time points 1-8 were considered. The results indicate: 1) acute inflammation of the nasal mucosa after the first increase in ambient ozone levels, with 2) a significant dose-dependent increase in leukocyte and eosinophil cationic protein levels, and 3) possible adaptation of the nasal mucosa in spite of constant high levels of ozone exposure in children during the summer season.

Cyanosis due to diastolic right-to-left shunting across a ventricular septal defect in a patient with repaired tetralogy of Fallot and pulmonary atresia

Cyanosis as a result of right-to-left shunting across a ventricular septal defect is commonly encountered in patients with congenital heart disease when systolic pressure in the right ventricle exceeds that in the left ventricle. Reported is the case of a child who remained cyanosed after surgical correction of pulmonary atresia despite right ventricular systolic pressure being lower than left ventricular pressure. Colour-flow Doppler showed a residual ventricular septal defect, with right-to-left shunting in diastole alone.

Low prevalence of the immunoglobulin-A-binding beta antigen of the C protein among Streptococcus agalactiae isolates causing neonatal sepsis

Streptococcus agalactiae (Group B streptococcus, GBS) is the most important pathogen causing neonatal sepsis. The role of bacterial proteins contributing to pathogenicity in GBS infections has not yet been clearly determined, but the C protein complex has been suggested to be involved in both virulence and protective immunity. The aim of this study was to assess the prevalence of GBS strains bearing the gene encoding for the beta antigen of the C protein among clinical isolates from 68 neonates with sepsis, 45 newborns colonized without clinical signs of infection, and 50 isolates from pregnant women. The prevalence of the beta antigen gene in all three groups was low (24% vs. 19% vs. 22%) [corrected], and the differences between groups were not statistically significant. Clinical characteristics and cytokine plasma levels did not differ between septic patients with beta antigen-positive and -negative strains. The beta-antigen gene was not found among serotype III isolates, which accounted for roughly half of all the strains isolated. Thus, polymerase chain reaction (PCR) analysis based on the beta antigen gene seems not helpful for distinguishing invasive from colonizing GBS strains. A vaccine based on peptide antigens from the beta antigen of the C protein would most probably not provide protection against the majority of GBS isolates. When analyzing the PCR products of the C protein beta antigen gene by DNA sequencing, a genetic heterogeneity was observed, revealing small repetitive genetic elements within the amplified fragment, an observation that should be studied further.