Early childhood infectious diseases and the development of asthma up to school age: a birth cohort study

Prevalence of allergy-related symptoms in Singaporean children in the second year of life

This study describes the cross-sectional prevalence of symptoms associated with eczema (chronic itchy rash), asthma (wheeze), and allergic rhinitis (rhinoconjunctivitis) in 1026 subjects between 18.5 and 23 months old (median age is 21 months) in Singapore. The first 2 yr cumulative prevalence of chronic itchy rash, wheeze, and rhinoconjunctivitis were 22.1% (n=227), 22.9% (n=235), and 8.4% (n=86) respectively. In total, 42.2% (414 of 979) reported ever having any of these symptoms. Eczema, although prevalent, was diagnosed only in 34.4% (n=78) of children with chronic itchy rash. Children with this eczematous rash were also more prone to wheeze (cOR=2.0, 95% CI: 1.2-3.0) and rhinoconjunctivitis (cOR=2.0, 95% CI: 1.4-2.8). Similarly, subjects who reported rhinoconjunctivitis and chronic itchy rash were 2.4 times (95% CI: 1.6-3.6) and 1.4 times (95% CI: 1.0-2.0) more at risk of wheezing respectively. Family history of allergy was a significant risk factor for chronic itchy rash (aOR=1.8, 95% CI: 1.3-2.4) and wheeze (aOR=1.7, 95% CI: 1.3-2.4). Thus, symptoms related to allergy were already prevalent during the second year of life. Significant proportions of these symptoms are likely to be due to true atopy as strong relationship with familial history and comorbidity with other potential allergic symptoms were observed.

Childhood infections and risk of wheezing and allergic sensitisation at age 7-8 years

BACKGROUND

Childhood atopic disease has been associated with exposure to infections early in life. There is however considerable controversy on this issue, since evidence exists for both protective and adverse effects of infections. Aim of this study was to investigate the association between childhood infections and the occurrence of wheeze and allergic sensitisation in 7-8-year-old Dutch and German children.

METHODS

A nested case-control study was conducted among German and Dutch children participating in a large longitudinal study on respiratory health. Parents of 510 7-8-year-old children with respiratory complaints and an equal number of children without respiratory complaints were asked to complete a questionnaire. Blood samples were collected for specific serum Immunoglobulin E (IgE) analysis. Data on childhood infections were collected through records of the participating Municipal Health Services.

RESULTS

No association was found between recent wheeze and any of the childhood infections investigated. For scarlet fever infection an increased risk of allergic sensitisation (OR: 2.82; 95% CI: 1.40-5.72) and sensitisation against grasses (OR: 3.00; 95% CI: 1.35-6.69) at the age of 7-8 years was found. Varicella infection tended towards increased risk of sensitisation against grasses (OR: 1.88; 95% CI: 0.99-3.58). For allergic sensitisation and sensitisation against grasses the odds ratios increased with increasing number of infections.

CONCLUSIONS

The results do not lend support to the suggestion that childhood infection protects against wheezing or allergic sensitisation at age 7-8 years. Scarlet fever or varicella infection presented an increased risk of allergic sensitisation.

[Childhood infections: friends or foes?]

Asthma prevalence has increased significantly; this increase appears to be relatively recent. The observed increases in this prevalence cannot be genetic in origin; on the other hand lifestyles have changed in many ways for environment or feeding. The hygiene hypothesis must be distinguished in terms whether one is addressing asthma or atopy. Although there are associations between asthma and atopy, they are not interchangeable. The pathogenic links between childhood infections and asthma require an undisputed definition of asthma. But many wheezing syndromes have been recognized in the pediatric age group, some overlap exists between these various phenotypes. The age at first severe infection seems to be crucial in determining the outcome of reinfection and suggests that the environment of the neonatal lung is a major determinant of disease and allergic patterns in later life.

Use of antibacterials in infancy: clinical implications for childhood asthma and allergies

Evidence from experimental studies in rodents and results from epidemiologic studies with a retrospective design suggest a possible causal association between antibacterial use in early childhood and asthma. Such an association is thought to be mediated by antibacterial-induced alterations in the intestinal flora, leading to a skewing of the immune system of young children toward an atopic phenotype. However, results from recently conducted prospective studies suggest that the previously observed association between antibacterial use in early childhood and asthma is not one of 'cause and effect' but rather that frequent antibacterial use in early childhood may be a marker of an increased risk of being diagnosed with asthma later in childhood. Although antibacterials should not be used excessively in young children, their use in early childhood is not likely to explain the increased prevalence of asthma and allergies in children in industrialized countries.

Asthma and indoor air: contrasts in the dose response to cat and dust-mite

The role of the indoor environment in asthma is of major concern because (i) the disease has become more severe; (ii) we spend>or=90% of our lives indoors and (iii) a large proportion of asthmatic children and young adults are allergic to allergens found indoors. Recent evidence that children raised in a home with animals, i.e. indoor cat or dog, are less likely to become allergic has provided a great opportunity to understand the mechanisms controlling the prevalence of allergic disease. In addition the results pose a challenge to many of the hypotheses about reasons for the increase in asthma. The evidence that children or adults who make a modified TH2 response i.e. immunoglobulin (Ig)G and IgG4 ab without IgE, are not at increased risk of asthma strongly supports the role of IgE in asthma. Equally the results may give insight into a form of tolerance that could be a target for protecting patients against allergic disease.

PRACTICAL IMPLICATIONS

Evidence for the immune response to cat allergen shows that the alternative response to an allergy, TH2 response, is a controlled or modified form of the response not a Th1 response. Furthermore, avoiding cats in the home in most communities would not decrease the prevalence of sensitization to cats because there is cat allergen distributed in schools, other public buildings, and homes without a cat.

Risk of physician-diagnosed asthma in the first 6 years of life

OBJECTIVE

The objective of this cohort study was to determine if complications of pregnancy and labor, characteristics at birth, and exposure to infections influence the incidence of asthma in the first 6 years of life.

DESIGN

We identified all children born between 1980 and 1990 in the Province of Manitoba, Canada. We used records of physician contacts (inpatient and outpatient) and services of the universal provincial health insurance plan to follow up 170,960 children from birth to the age of 6 years to identify the first diagnosis of asthma. Information on mothers and siblings was also obtained to determine family history of disease and exposure to infections.

RESULTS

During the study period, a diagnosis of asthma was made in 14.1% of children by the age of 6 years. The incidence was higher in boys than in girls, in those with family history of allergic diseases. It was higher in urban than in rural areas, and lowest in those born in winter. Asthma was more likely in those with low birth weight and premature birth. Certain congenital abnormalities and complications of pregnancy and labor also increased the risk of asthma. The risk of asthma increased with maternal age. Both upper and lower respiratory infections increased the risk of subsequent asthma, and this effect was more important than exposure to familial respiratory infections, which also tended to increase asthma risk. The risk of asthma decreased with the number of siblings when siblings had a history of allergic disorders.

CONCLUSIONS

In addition to genetic influences, intrauterine and labor conditions are determinants of asthma. Exposure to both upper and lower respiratory tract infections increases the risk; these infections do not explain the protective effect associated with the increasing number of siblings.

Allergic airway inflammation is exacerbated during acute influenza infection and correlates with increased allergen presentation and recruitment of allergen-specific T-helper type 2 cells

BACKGROUND

Respiratory viral infections are a leading cause of the hospitalization of asthmatics, however, the cellular immunological interactions which underlie these two diseases remain elusive.

OBJECTIVE

We sought to characterize the effect influenza viral infection has on allergic airway inflammation and to identify the cellular pathways involved.

METHODS

We have used an ovalbumin (OVA) model of allergic airway inflammation, which involves sensitization of animals with OVA adsorbed in alum adjuvant followed by an intranasal challenge with OVA in phosphate-buffered saline. To study T cell recruitment into the lung, we adoptively transferred in vitro activated T cell receptor-transgenic T cells, which were subsequently identified by fluorescence-activated cell sorting (FACS) analysis. In addition, to study in vivo dendritic cell (DC) migration, we administered fluorescently labelled dextran and identified DCs that had phagocytosed it by FACS analysis.

RESULTS

We found that different stages of influenza infection had contrasting effects upon the outcome of OVA-induced allergic airway inflammation. The allergic response against OVA was exacerbated during the acute stage of influenza infection; however, mice were protected against the development of airway eosinophilia at late time-points following infection. We investigated the mechanisms responsible for the virus-induced exacerbation and found that the response was partially independent of IL-4 and that there was increased delivery of inhaled allergens to the draining lymph node during the acute stage of the infection. In addition, virus-induced inflammation in the lung and draining lymph node resulted in the non-specific recruitment of circulating allergen-specific effector/memory cells.

CONCLUSION

In addition to virus-mediated damage to the lung and airways, influenza viral infection can also enhance unrelated local allergic responses.

Atopic disease and its determinants -- a focus on the potential role of childhood infection

BACKGROUND

Atopic diseases develop on a genetic background and are modulated by environmental factors among which some infectious diseases are thought to have a protective influence.

OBJECTIVE

The aim of this study was to determine the influence of infectious diseases in younger ages, bacterial and viral, on atopic diseases and sensitization to aero- and food-allergens in adults.

METHODS

A population-based sample of 4262 subjects aged 25-74 years were interviewed concerning their history of infectious disease within the first 18 years of life. Information about allergic disease, including atopic eczema, allergic rhinitis (AR), and asthma was obtained. A blood sample was drawn and analysed for allergen-specific IgE antibodies against food- and aero-allergens.

RESULTS

Multiple logistic regression analyses identified viral infection to be associated with AR (adjusted odds ratio (OR) = 1.39; 95% confidence interval (95% CI): 1.13-1.72) and sensitization to aeroallergens (OR = 1.21; 95% CI: 1.05-1.41). Bacterial disease was a negative predictor for atopy development in the subgroup of patients sensitized to nutritional allergens with concomitant atopic eczema (OR = 0.34; 95% CI: 0.11-0.99), AR (OR = 0.67; 95% CI: 0.42-1.07), or asthma (OR = 0.41; 95% CI: 0.19-0.87). Influences of viral and bacterial infection on AR differed with regard to family history of atopic disease.

CONCLUSION

In our study population, history of viral infection was consistently positively associated with AR. Our data suggests that bacterial infections might be preventive for specific subgroups of atopy.

The Copenhagen Prospective Study on Asthma in Childhood (COPSAC): design, rationale, and baseline data from a longitudinal birth cohort study

BACKGROUND

The atopic diseases asthma, atopic dermatitis, and allergic rhinitis are the most common chronic diseases in children, and their prevalence has increased recently in industrialized nations. Little is known about the genetic-environmental interaction factors driving such proliferation.

OBJECTIVE

To investigate the relationships among genetic, environmental, and lifestyle factors in the development of atopic diseases in high-risk children with the aim of developing evidence-based prevention strategies.

METHODS

The Copenhagen Prospective Study on Asthma in Childhood is a single-center, birth cohort study of children of asthmatic mothers. Objective assessments begin at birth, with scheduled visits every 6 months and when acute symptoms manifest. Clinical outcomes comprise preasthma, asthma, atopic dermatitis, allergic rhinitis, allergy, lung function, and bronchial responsiveness. Exposure assessments comprise respiratory, intestinal, and skin microbiology; the child's diet; indoor and outdoor air quality; allergens; and indicators of lifestyle. Genetic characteristics of probands and parents are evaluated. Quality assurance follows Good Clinical Practice guidelines.

RESULTS

Four hundred eleven infants of asthmatic mothers were enrolled at the age of 1 month. The children were born between August 2, 1998, and December 28, 2001. Compared with the Copenhagen population, mothers of the cohort population were less likely to have given natural childbirth. The households were slightly less affluent, with fewer children and fewer pets. Whites may be overrepresented. At age 2 years, 93% of the infants were still actively participating in the cohort.

CONCLUSIONS

This longitudinal birth cohort study of high-risk Danish infants consists of objective phenotyping, detailed information on exposure, high data quality, and a high participant retention rate.

Antibiotic use in the first year of life and asthma in early childhood

BACKGROUND

An association between antibiotic use in early life and asthma in childhood has been reported in five retrospective studies and one longitudinal study.

OBJECTIVE

To examine the relation between the use of oral antibiotics in the first year of life and asthma in early childhood.

METHODS

Longitudinal follow-up of 4408 children enrolled in a health maintenance organization (HMO) from birth to the age of 5 years.

RESULTS

After adjusting for sex and illnesses of the lower respiratory tract (LRIs), we found a significant association between antibiotic use in the first year of life and asthma between the ages of 1 and 2 years (odds ratio (OR) for 1-2 vs. no courses of antibiotics=1.9, 95% confidence interval (CI)=1.3-2.7; OR for 3-4 vs. no courses of antibiotics=1.6, 95% CI=1.1-2.4; OR for at least 5 vs. no courses of antibiotics=2.1, 95% CI=1.5-3.2). After adjustment for sex and LRIs in the first year of life, there was no significant association between antibiotic use in the first year of life and asthma that was initially diagnosed between the ages of 2 and 5 years and that persisted up to the age of 5 years (OR for 1-2 vs. no courses of antibiotics=1.1, 95% CI=0.8-1.4; OR for 3-4 vs. no courses of antibiotics=1.3, 95% CI=0.9-1.8; OR for at least 5 vs. no courses of antibiotics=1.0, 95% CI=0.7-1.4). Conclusions Our findings do not support the hypothesis that antibiotic use in early life is associated with the subsequent development of asthma in childhood but rather suggest that frequent antibiotic use in early life is more common among asthmatic children.

Infections, medication use, and the prevalence of symptoms of asthma, rhinitis, and eczema in childhood

BACKGROUND

The "hygiene hypothesis" postulates that infections during infancy may protect against asthma and atopy. There is also some evidence that antibiotic and/or paracetamol use may increase the risk of asthma.

METHODS

The study measured the association between infections, and medication use early in life and the risk of asthma at age 6-7 years. It involved 1584 children who had been notified to public health services with serious infections at age 0-4 years, and 2539 children sampled from the general population. For both groups, postal questionnaires were completed by parents.

RESULTS

There was little difference in the prevalence of current wheezing between the childhood infections group (prevalence = 23.5%) and the general population group (prevalence = 24.3%). There was also little difference whether the major site of infection was gastrointestinal (prevalence = 24.1%), invasive (prevalence = 24.6%) or respiratory (prevalence = 21.1%). However, in both groups, there were associations with antibiotic (OR = 1.78, 95% CI 1.49 to 2.14) or paracetamol (OR = 1.38, 95% CI 1.04 to 1.83) use in the first year of life or recent paracetamol use (OR = 2.10, 95% CI 1.78 to 2.49) and current wheezing. There was a weak protective effect of childhood infections in children who had not used antibiotics in the first year of life (OR = 0.78, 95% CI 0.55 to 1.10).

CONCLUSIONS

These findings are consistent with other evidence that antibiotic use early in life may increase the risk of asthma. They are also consistent with some preliminary evidence associating paracetamol use with an increased risk of asthma. Any protective effect of notifiable childhood infections was weak.

Influence of MMR-vaccinations and diseases on atopic sensitization and allergic symptoms in Swiss schoolchildren

The prevalence of asthma and allergic disease has increased in many countries. It has been proposed that vaccinations may contribute to the development of allergic disease by reducing clinical infections in infancy or through the direct IgE-inducing effects of the vaccines. Evidence for a potential role of immunizations in the development of allergic disease is scarce. Therefore the objective was to study the associations between vaccinations against measles, mumps and rubella (MMR), natural infections of these diseases and atopic sensitization to indoor and outdoor allergens and allergic symptoms in schoolchildren. The cross-sectional study including 1537 8(th) grade school children aged 13-15 years living in 10 communities across Switzerland was organized in the framework of an environmental health surveillance program within the School Health Services (Swiss Surveillance Program of Childhood Asthma and Allergies with respect to Air Pollution and Climate, SCARPOL). Main outcome measures were asthma and sneezing during pollen season assessed by parental questionnaires and atopic sensitization determined by IgE concentrations to various allergens. It was found that parents' reported history of measles or mumps was associated with a stronger immune response than two or more vaccinations against the respective infection (measles: geometric mean IgG titers (GMT) lU/ml (95% Cl) 2.8 (2.0-3.9) vs. 1.2 (1.0-1.4), mumps: GMT PE/ml (95% Cl) 16.3 (13.9-19.1) vs. 8.5 (6.1-11.7). With respect to atopic sensitization similar associations for exposure by natural MMR-infections or MMR-vaccinations were found: measles: OR (95% Cl) 1.02 (0.53-1.96) vs. 1.22 (0.69-2.16), mumps: 0.59 (0.38-0.93) vs. 0.79 (0.49-1.27), rubella: 0.93 (0.61-1.43) vs. 0.95 (0.66-1.37), respectively. Inverse relationships were found between the risk of asthma and a positive disease history or vaccination of measles 0.36 (0.14-0.91) vs. 0.45 (0.21-0.98) or a positive serum titer against measles 0.65 (0.35-1.20). From the present study can be concluded that exposure by MMR-vaccinations or natural MMR-infections in childhood does not increase the risk of sensitization to common allergens as well as to allergic respiratory diseases. MMR-vaccinations or natural MMR-infections are therefore an unlikely factor contributing to the increase in atopic disease in developed countries.

Perinatal risk factors for bronchial hyperresponsiveness and atopy after a follow-up of 20 years

BACKGROUND

Perinatal risk factors are associated with lung function and respiratory symptoms in adult life. Whether the same holds for distinctive asthma features, such as bronchial hyperresponsiveness (BHR) and atopy, has scarcely been studied.

OBJECTIVE

We sought to identify the perinatal risk factors for the development of BHR and atopy.

METHODS

BHR and atopy were measured after 20 years' follow-up in 597 of 3162 babies born from 1975 through 1978. Factors directly related to delivery of these children were studied in association with the presence of BHR and atopy.

RESULTS

Twenty-five percent had BHR, and 47% had atopy. Delivery duration of longer than 12 hours was associated with the development of atopy (odds ratio [OR], 2.24; 95% CI, 1.30-3.86), and severe respiratory infection in the first year of life was associated with the development of BHR (OR, 2.69; 95% CI, 1.41-5.16). Nonatopic subjects born after induced labor and current smokers were more likely to have BHR (ORs of 2.41 [95% CI, 1.07-5.41] and 2.50 [95% CI, 1.12-5.59], respectively). Prenatal smoke exposure and childhood pet keeping decreased the risk for atopy, especially in BHR-positive subjects (ORs of 0.51 [95% CI, 0.27-0.99] and 0.46 [95% CI, 0.24-0.88], respectively).

CONCLUSIONS

It has been shown that events before or during birth still have an effect on respiratory health 20 years later. We put forward that an extreme hormonal status during delivery primes the fetal immune system toward atopy development. Furthermore, a severe respiratory infection in the first year of life appears associated with BHR development, and prenatal smoke exposure might be protective for the development of atopy, yet explanatory mechanisms are lacking thus far.

Does previous infection protect against atopic eczema and recurrent wheeze in infancy?

BACKGROUND

Frequent infection in infancy and early childhood has been hypothesized to explain the low prevalence of asthma and other atopic disease among children in developing countries (the so-called 'hygiene hypothesis'), but the low prevalence in Eastern Europe remains unexplained.

OBJECTIVE

To test the hygiene hypothesis in the Republic of Belarus by examining the relationship between gastrointestinal (GI) and respiratory infection and two potentially atopic outcomes in the first 12 months of life: atopic eczema and recurrent wheeze. METHODS; We carried out two case-control studies nested within a large (n=17 046) randomized trial in Belarus, with cases defined as (1) first occurrence of atopic eczema (n=819) and (2) second episode of wheezing (n=112). Incidence density sampling was used to select four matched controls born within 1 month at the same hospital as the case. Exposure was defined as one or more episodes of GI or respiratory infection (examined separately) with onset >7 days before onset of the case's atopic outcome. Analyses controlled for family atopic history, duration of exclusive breastfeeding, sex, birth weight, maternal education, and (for recurrent wheeze) maternal smoking.

RESULTS

For atopic eczema, prior GI infection occurred in 7.4% of cases vs. 6.0% of controls [adjusted OR=1.27 (0.94-1.72)] and prior respiratory infection in 35.2% vs. 32.6% [adjusted OR=1.14 (95% CI=0.94-1.37)]. For recurrent wheeze, prior GI infection occurred in 9.8% of cases vs. 7.4% of controls [adjusted OR=1.30 (0.60-2.82)].

CONCLUSION

Our results do not support the hypothesis that infection protects against atopic eczema or recurrent wheezing in the first 12 months of life.

Risk factors for atopy among school children in a rural area of Latin America

BACKGROUND

Infection with common childhood infectious diseases including geohelminth infections may provide protection against the development of atopy and allergic disease. Few studies have investigated risk factors for atopy among children living in rural areas of Latin America.

OBJECTIVE

To identify risk factors associated with atopy among school-age children in a rural area of Latin America.

METHODS

Analytic cross-sectional study of school-age children conducted in seven rural schools in Pichincha Province in Ecuador. Detailed risk factor information was obtained by questionnaire, stool samples were collected for identification of geohelminth parasites, and Mantoux testing was performed to determine tuberculin sensitization.

RESULTS

A total of 1002 children from seven rural schools were recruited. The prevalence of geohelminth infections was high (70.1% were infected with at least one geohelminth parasite) and the prevalence of allergic sensitization was high (20.0% had evidence of aeroallergen sensitization). Factors associated with significant protection against atopy in multivariate analyses were the presence of overcrowding in the child's home, low socio-economic level, and infection with geohelminth parasites, and the protective effects of the three factors were statistically independent.

CONCLUSION

Low socio-economic level, overcrowding and geohelminth infection, are independently protective against atopy among school-age children living in a rural area of Latin America.

Prenatal and early postnatal environments are significant predictors of total immunoglobulin E concentration in Filipino adolescents

BACKGROUND

Recent evidence suggests that atopic disease may in part be mediated by fetal growth, as well as exposure to infectious disease early in life. Few studies have been able to evaluate these associations simultaneously, or to investigate prospectively the long-term effects of early environments while adequately controlling for potentially confounding variables.

OBJECTIVE

To examine how prenatal growth and infectious disease in infancy are related to total IgE production in adolescence.

METHODS

Ninety-nine adolescents (aged 14-15 years) were selected from a larger cohort study according to the following criteria: full-term birth, currently healthy, and small-for-gestational age (N=53) or appropriate-for-gestational age (N=46). Plasma total IgE was measured with ELISA, and analysed in relation to anthropometric, nutritional, and environmental quality data collected prospectively beginning in the third trimester prior to birth.

RESULTS

Each episode of infectious morbidity recorded at bimonthly intervals in the first 6 months of life was associated with a 0.12 log IU/mL reduction in total IgE in adolescence (P=0.004). Prenatal undernutrition was associated with increased adolescent IgE, but only under conditions of an unsanitary household environment (P=0.002). Each additional kilogram gained per month in the first 6 months of life was associated with an increase in adolescent IgE of 0.74 log IU/mL (P=0.03). Each quartile increase in weekly household income at the time of blood sampling was associated with a 0.10 log IU/mL reduction in total IgE (P=0.02).

CONCLUSION

Infectious disease in infancy, as well as interactions between prenatal and postnatal environments, appear to have long-term effects on adolescent total IgE production. Future research should investigate the mechanisms behind these effects, and their implications for symptoms of atopic disease.

Influences in allergy: epidemiology and the environment

Many decades after the first descriptions of hay fever in the 19th century, we still struggle with the formation of a cogent conception embracing all the many fragments of insight into the various aspects of allergic and asthmatic diseases. Although in daily practice we can grasp and allocate most of the clinical manifestations, in research the fundamental structures are only in part recognized. We therefore presume that the underlying mechanisms are complex and multifaceted. We have explored in countless directions while branching into ever more detailed analyses of phenomena, all of which are associated with the conditions of interest. But how can we rearrange these pieces to advance toward a broader understanding of asthma and allergies? Epidemiology as a scientific tool to study the occurrence, the natural course, and the determinants of a condition in various sociocultural environments might contribute to the edifice of such a scaffold. This review does not intend to present a comprehensive digest of the relevant literature: the reader can refer to other "state of the art" reviews. The intention is to discuss some conceptual cornerstones and to illustrate them with a few examples.

A novel promoter polymorphism in the gene encoding complement component 5 receptor 1 on chromosome 19q13.3 is not associated with asthma and atopy in three independent populations

BACKGROUND

The inflammatory functions of complement component 5 (C5) are mediated by its receptor, C5R1, which is expressed on bronchial, epithelial, vascular endothelial and smooth muscle cells. A susceptibility locus for murine allergen-induced airway hyper-responsiveness was identified in a region syntenic to human chromosome 19q13, where linkage to asthma has been demonstrated and where the gene encoding C5R1 is localized.

OBJECTIVE

The aim of this study was to screen for novel polymorphisms in the C5R1 gene and to determine whether any identified polymorphisms are associated with asthma and/or atopy and whether they are functional.

METHODS

Single-nucleotide polymorphism (SNP) detection in the gene encoding C5R1 was performed by direct sequencing. Genotyping was performed in three populations characterized for asthma and/or atopy: (1) 823 German children from The Multicenter Allergy Study; (2) 146 individuals from Tangier Island, Virginia, a Caucasian isolate; and (3) asthma case-parent trios selected from 134 families (N=783) in Barbados. Functional studies were performed to evaluate differences between the wild-type and the variant alleles.

RESULTS

We identified a novel SNP in the promoter region of C5R1 at position -245 (T/C). Frequency of the -245C allele was similar in the German (31.5%) and Tangier Island (36.3%) populations, but higher in the Afro-Caribbean population (53.0%; P=0.0039 to <0.0001). We observed no significant associations between the -245 polymorphism and asthma or atopy phenotypes. Upon examination of the functional consequences of the -245T/C polymorphism, we did not observe any change in promoter activity.

CONCLUSION

This new marker may provide a valuable tool to assess the risk for C5a-associated disorders, but it does not appear to be associated with asthma and/or atopy.

Bystander suppression of allergic airway inflammation by lung resident memory CD8+ T cells

CD8+ memory T cells have recently been recognized as playing a key role in natural immunity against unrelated viral infections, a phenomenon referred to as "heterologous antiviral immunity." We now provide data that the cellular immunological interactions that underlie such heterologous immunity can play an equally important role in regulating T helper 2 immune responses and protecting mucosal surfaces from allergen-induced inflammation. Our data show that CD8+ T cells, either retained in the lung after infection with influenza virus, or adoptively transferred via the intranasal route can suppress allergic airway inflammation. The suppression is mediated by IFN-gamma, which acts to reduce the activation level, T helper 2 cytokine production, airways hyperresponsiveness, and migration of allergen-specific CD4+ T cells into the lung, whereas the systemic and draining lymph node responses remain unchanged. Of note, adoptive transfer of previously activated transgenic CD8+ T cells conferred protection against allergic airway inflammation, even in the absence of specific-antigen. Airway resident CD8+ T cells produced IFN-gamma when directly exposed to conditioned media from activated dendritic cells or the proinflammatory cytokines IL-12 and IL-18. Taken together these data indicate that effector/memory CD8+ T cells present in the airways produce IFN-gamma after inflammatory stimuli, independent of specific-antigen, and as a consequence play a key role in modifying the degree and frequency of allergic responses in the lung.

The hygiene hypothesis of atopic disease--an extended version

The hygiene hypothesis of atopic disease suggests that environmental changes in the industrialized world have lead to reduced microbial contact at an early age and thus resulted in the growing epidemic of atopic eczema, allergic rhinoconjunctivitis, and asthma. The epidemiological findings have been combined with the Th1/Th2 paradigm of immune responsiveness to provide a coherent theory. Recent advances in epidemiology and immunology demonstrate, however, that the hygiene hypothesis may need to be extended in three respects. First, the importance of infections in causing immune deviance may be outweighed by other sources of microbial stimulation, perhaps most importantly by the indigenous intestinal microbiota. Second, immunomodulatory and suppressive immune responses complement the Th1/Th2 paradigm. Third, in addition to protection against atopy, protection against infectious, inflammatory, and autoimmune diseases may also depend upon healthy host-microbe interactions implicated in the hygiene hypothesis.

Asthma, allergy, and upper airway disease

The practitioner must be aware of the strong interrelationship between asthma, allergy, eczema, otitis media, viral upper respiratory infection, and sinusitis. When allergy, eczema, otitis media (particularly after the age of 2 years), viral upper respiratory infection, or sinusitis is present in a patient, asthma must be considered as possible sequelae. If a patient has symptoms of intermittent or persistent asthma, consideration must be given to the presence of allergy, eczema, otitis media, viral upper respiratory infection, or sinusitis as comorbid conditions or possible triggers for the asthma symptoms. Failure to evaluate the entire upper and lower airway for these interrelated conditions will result in incomplete treatment and incomplete symptom relief [61]. This article reviews the strong association between diseases of the upper and lower airway [62,63]. Treatment and control of upper airway symptoms is essential for control of asthma symptoms. Control of allergy, eczema, otitis, sinusitis, and viral symptoms result in improved outcomes for asthma patients. Reduction of these asthma triggers and comorbid conditions is also likely to reduce asthma medication requirements while improving symptoms status.

Variation in childhood asthma among former preterm infants

OBJECTIVES

The role of in utero and perinatal exposures in modifying asthma risk among children born prematurely was assessed. Study design Former preterm children (n=251) were identified from a birth cohort. Examinations, including lung function testing, were performed at ages 8 to 11 years. Perinatal exposures were ascertained from neonatal medical records.

RESULTS

Univariate predictors of asthma included male gender, African American ethnicity, maternal asthma, and birth weight. Asthmatics were less likely to have been small for gestational age (SGA) than nonasthmatics (12.4% vs 22.7%, P=.04) and had more neonatal pulmonary disease. After adjusting for maternal asthma and demographic factors, asthma was associated with chronic lung disease of infancy, neonatal mechanical ventilation and corticosteroid use, and a higher childhood body mass index. Children who were septic postbirth and girls who were SGA were less likely to have asthma (OR for sepsis, 0.2; 95% CI, 0.1-0.6; OR for girls who were SGA compared with girls who were not SGA, 0.05; CI, 0.01-0.34).

CONCLUSIONS

Among premature children, female SGA status and neonatal sepsis appear protective relative to the development of childhood asthma. Differential susceptibility to asthma among preterm children may relate to exposures that operate in the in utero and early postnatal environment to accelerate lung development, alter innate immunity, or both.

Can we prevent allergy?

Allergic conditions continue to increase steeply. The last two decades have seen many prevention trials, studying the effect of dietary and environmental interventions. These trials have yielded invaluable information about the atopic march and also highlighted the need for a clear and commonly used nomenclature as well as a need for better outcome measures. This review discusses primary and secondary prevention studies and their results.

Effects of intestinal microflora and the environment on the development of asthma and allergy

The aim of previous research into the causes of allergic diseases, including asthma was mostly to identify potential risk factors in the environment. No major risk factors have been identified, however. Over the past 10 years, focus has, therefore, more been directed towards protective factors that could enhance the development of tolerance to allergens which were previously encountered early in life, but are now lost in modern affluent societies. In particular, the role of childhood infections has been discussed, but so far these studies have not been conclusive. Recent epidemiological studies and experimental research suggest that the microbial environment and exposure to microbial products in infancy modifies immune responses and enhances the development of tolerance to ubiquitous allergens. The intestinal microflora may play a particular role in this respect, as it is the major external driving force in the maturation of the immune system after birth, and animal experiments have shown it to be a prerequisite for normal development of oral tolerance. Recent studies have shown differences in the composition of the microflora between healthy and allergic infants in countries with a high and low prevalence of allergies and between healthy and allergic infants within such countries. These differences are apparent within the first week of life and thus precede clinical symptoms. The use of live microorganisms that might be beneficial to health has a long tradition and the safety is well documented. Very recently, several prospective intervention studies, modifying the gut flora from birth have yielded encouraging results and may suggest a new mode of primary prevention of allergy in the future.

Asthma and atopy - the price of affluence?

Irrespective of improved knowledge of many aspects of atopic diseases, the unfavorable trends in their prevalence particularly among children could not have been reversed. A growing body of evidence suggests that something may lack from our societal affluence that has the capacity to provide protection against the development of atopic diseases. Much attention during the last years has been devoted to the hygiene hypothesis. This review outlines the impact of environment and lifestyle, particularly from the perspective of the East-West gradient, on the development of atopic diseases, with a special emphasis on the hygiene hypothesis in its broadest sense.

Influence of climate factors on emergency visits for childhood asthma attack

BACKGROUND

Asthma attack shows strong seasonality. The purpose of the present study was to quantify the contribution of climate variables and other seasonal factors on the incidence of emergency visits for childhood asthma in Tokyo, Japan.

METHODS

The number of children who visited emergency rooms at Jikei university hospitals in Tokyo during 1998-2002 (5559 visits) was retrieved retrospectively from files from the Department of Pediatrics, and compared with 45 climate parameters from the Meteorological Agency using multiple regression models with a stepwise backward elimination approach.

RESULTS

The number of visits (3.7 +/- 3.1) per night increased significantly when climate conditions showed a rapid decrease from higher barometric pressure, from higher air temperature and from higher humidity, as well as lower wind speed. The best-fit model demonstrated that a 22% variation in the number of visits was explained by a linear relationship with 12 climate variables, which increased to 36% after adjusting for calendar month and day of the week. Moreover, when the number of asthma visits was cut off at nine per night, the area under the receiver operator characteristics curve was 0.91 (95% CI: 0.89-0.94) in the multiple logistic regression model using the same variables.

CONCLUSIONS

These results suggest that these models might quantify contributions of specific climate conditions and other seasonal factors on the number of emergency visits per night for childhood asthma attack in Tokyo, Japan.

Epigenetic inheritance of fetal genes in allergic asthma

Asthma has been associated with an exaggerated T-helper type 2 (Th2) over Th1 responses to allergic and nonallergic stimuli, which leads to chronic airway inflammation and airway remodeling. In the present article, we propose that many of the genes involved in IgE synthesis and airways (re)modeling in asthma are persistent or reminiscent fetal genes which may not be silenced during early infancy (or late pregnancy). Genes of the embryologic differentiation of ectodermic and endodermic tissues may explain some of the patterns of airway remodeling in asthma. In utero programming leads to gene expression, the persistence of which may be associated with epigenetic inheritance phenomena induced by nonspecific environmental factors. Clear delineation of these issues may yield new information on the mechanisms of asthma and new targets for therapeutic intervention and primary prevention.

Is the increase in allergic asthma associated with an inborn Th1 maturation or with an environmental Th1 trigger defect?

The main reason for the asthma epidemic in industrialized countries is unknown. While childhood mortality from acute respiratory infection is still high in developing countries where asthma prevalence is low, there might be a suppressed natural selection in industrialized countries with a high asthma prevalence. Children with an inborn Th1 maturation defect might survive by better health care and antibiotic use at the cost of higher asthma and allergy rates. Another distinct group of children maybe represented by those having an environmental Th1 trigger deficit where the immune systems is not being sufficiently exposed in early life. Both, a Th1 maturation and a Th1 trigger defect may contribute to a dual Th1 allergy theory.

Early prescriptions of antibiotics and the risk of allergic disease in adults: a cohort study

BACKGROUND

It is frequently asserted that antibiotic prescriptions in childhood are associated with the development of allergic disease, especially asthma. A study was undertaken to establish the direction of this relationship.

METHODS

A retrospective cohort study of 746 adults was performed in three general practices. Antibiotic prescriptions in the first 5 years of life, collected from contemporary medical records, were related to self-reports of asthma and hay fever and the results of skin prick testing with common aeroallergens.

RESULTS

There was no relationship between early antibiotic prescription and atopy, either for all antibiotic use (OR 1.01) or for antibiotics prescribed at different ages. The significant associations between prescriptions at ages 4 and 5 and hay fever (OR 1.23 and 1.16, respectively) were explained by coexisting asthma. Relationships between antibiotic use and asthma (allergic or otherwise) were statistically significant and strengthened with increasing age of prescription, but were largely confined to antibiotics prescribed for lower respiratory symptoms.

CONCLUSIONS

The reported associations between childhood antibiotic use and asthma are most plausibly explained by "reverse causation"--the tendency for prescriptions to be written for the early manifestations of pre-existing asthma.

Endotoxins and allergy: lessons from the murine model

Exposure early in life to organic dusts containing immunomodulatory components such as endotoxins and immunizing components such as aeroallergens may greatly influence whether subsequent encounters with allergens lead rather to sensitization or unresponsiveness. We investigated the effects of endotoxin in the context of allergen-mediated immune responses in a murine model of allergen sensitization. Systemic sensitization with ovalbumin induced high serum levels of allergen-specific IgE, predominant Th2-type cytokine production, eosinophilic airway inflammation and in vivo airway hyperreactivity. Endotoxins were either applied systemically prior to sensitization, or via the airways prior to airway challenges, or by repeated inhalation during the first weeks of life prior to subsequent sensitization. Different effects of endotoxins on allergen-induced immune responses may be attributed to differences in dosing, route of application, time relationship with allergen sensitization and the concurrent exposure to endotoxin and allergen. The results of these studies may help to define the effects of endotoxin on allergen-mediated immune reactions and to further delineate the important interrelationships between environment and disease development. Finally, this may lead to new strategies in the prevention and treatment of allergic diseases.

CD8+ T cells and immunoregulatory networks in asthma

It is well established that infection with respiratory viruses can cause acute local inflammation in humans and is a leading cause in the hospitalization of asthmatics. Less well recognized is the potential for viral infections to actually protect against the development of asthma, as are the cellular mechanisms which might underlie such protection. This review outlines the basic immunological pathways involved in atopic asthma and details the currently recognized cellular mechanisms induced by respiratory viral infections which can protect against the development of asthma. Specifically, it appears that virus infection induced memory T cells that remain in tissues, e.g. the lung and airways, can under certain circumstances create a local cytokine milieu which inhibits the development of ensuing allergic immune responses at that site. One key aspect of this immune modulation is the cytokine-dependent communication which occurs between the innate and the adaptive immune systems. The mechanistic principles underlying this form of immunomodulation should be taken into consideration when developing future forms of therapy and rational vaccine design.

Respiratory syncytial virus up-regulates TLR4 and sensitizes airway epithelial cells to endotoxin

Airway epithelial cells are unresponsive to endotoxin (lipopolysaccharide (LPS)) exposure under normal conditions. This study demonstrates that respiratory syncytial virus (RSV) infection results in increased sensitivity to this environmental exposure. Infection with RSV results in increased expression of Toll-like receptor (TLR) 4 mRNA, protein, and increased TLR4 membrane localization. This permits significantly enhanced LPS binding to the epithelial monolayer that is blocked by disruption of the Golgi. The increased TLR4 results in an LPS-induced inflammatory response as demonstrated by increased mitogen-activated protein (MAP) kinase activity, IL-8 production, and tumor necrosis factor alpha production. RSV infection also allowed for tumor necrosis factor alpha production subsequent to TLR4 cross-linking with an immobilized antibody. These data suggest that RSV infection sensitizes airway epithelium to a subsequent environmental exposure (LPS) by altered expression and membrane localization of TLR4. The increased interaction between airway epithelial cells and LPS has the potential to profoundly alter airway inflammation.

Adenoidectomy during early life and the risk of asthma

The objective of the study was to evaluate the risk of asthma in children who had undergone an adenoidectomy, an operation frequently performed on children with glue ear or recurrent otitis media. Two surveys were carried out, a nation-wide questionnaire returned by 483 individuals (survey A) and a survey of hospital discharge records involving 1616 children who had undergone an adenoidectomy and 161 control children who had undergone probing of the nasolacrimal duct due to congenital obstruction (survey B). The questionnaire (survey A) showed that an adenoidectomy before the age of 4 years was associated with asthma (OR 3.19, 95% CI 1.25; 8.13) and with allergy to animal dust (OR 2.50, 95% CI 1.27; 4.95). In survey B, asthma diagnosis was retrieved from the national asthma register. It showed also that adenoidectomy at an early age was associated with an increased risk of asthma (OR 6.74, 95% CI 2.99; 15.2). There was an association between asthma and adenoidectomy, even before adenoidectomy had actually been performed. The risk of asthma was highest among children who had had adenoidectomy because of recurrent otitis media. The observed association between an adenoidectomy and asthma may be explained by an underlying factor predisposing to both recurrent otitis media and asthma.

Atopic diseases of childhood

PURPOSE OF REVIEW

The incidence of atopic diseases, including atopic dermatitis, allergic rhinitis, and asthma, has increased in developed countries over the past several decades. These diseases comprise a large component of general pediatric practice. This review will highlight some of the recent advances in understanding the pathogenesis and natural history of these diseases, as well as the current approaches to the treatment of children with atopic diseases.

RECENT FINDINGS

Recent studies have identified multiple risk factors for the development and progression of atopic diseases. As a result, much research is focused on identifying therapies that can be initiated at a young age to prevent disease progression. New treatment options have become available in recent years, such as topical immunomodulators for atopic dermatitis, leukotriene antagonists for seasonal allergic rhinitis, and alpha-immunoglobulin E therapy for asthma. The importance of viewing allergic rhinitis and asthma as disorders of a single airway has been emphasized. Finally, an update on the national asthma guidelines was recently released in an effort to promote optimal asthma care.

SUMMARY

This review summarizes many of the recent advances in the diagnosis and treatment of atopic diseases in children. Although not intended to be a comprehensive review of this broad field, it provides a framework for appreciating the complexity of these diseases and for effectively managing them.

Predominance of rhinovirus in the nose of symptomatic and asymptomatic infants

Respiratory infections in infancy may protect against developing Th2-mediated allergic disease (hygiene hypothesis). To estimate the relative contribution of particular viruses to the development of the immune system and allergic disease, we investigated longitudinally the prevalence of respiratory viral infections in infants. One hundred and twenty-six healthy infants were included in this prospective birth cohort study in their first year of life. Physical examination was performed and nasal brush samples were taken during routine visits every 6 months and during an upper respiratory tract infection (URTI) (sick visits). The prevalence of respiratory viral infections in infants with URTI, infants with rhinitis without general malaise and infants without nasal symptoms was studied. Rhinovirus was the most prevalent pathogen during URTI and rhinitis in 0- to 2-year-old infants ( approximately 40%). During URTI, also respiratory syncytial virus ( approximately 20%) and coronavirus ( approximately 10%) infections were found, which were rarely detected in infants with rhinitis. Surprisingly, in 20% of infants who did not present with nasal symptoms, rhinovirus infections were also detected. During routine visits at 12 months, a higher prevalence of rhinovirus infections was found in infants who attended day-care compared with those who did not. We did not observe a relation between breast-feeding or smoking by one or both parents and the prevalence of rhinovirus infections. The parental history of atopy was not related to the prevalence of rhinovirus infection, indicating that the genetic risk of allergic disease does not seem to increase the chance of rhinovirus infections. In conclusion, rhinovirus infection is the most prevalent respiratory viral infection in infants. It may therefore affect the maturation of the immune system and the development of allergic disease considerably.

A meta-analysis of the association between childhood type 1 diabetes and atopic disease

OBJECTIVE

To review the published literature and perform a meta-analysis summarizing the evidence in support of an inverse association between type 1 diabetes and the atopic disorders: asthma, eczema, and allergic rhinitis in children.

RESEARCH DESIGN AND METHODS

MEDLINE, Web of Science, and PubMed were searched to identify relevant studies. These were assessed on quality criteria, and odds ratios (ORs) and 95% CIs were calculated for each study from the reported prevalences of atopy in children with diabetes and in control children. Meta-analysis was then used to derive a combined OR and test for heterogeneity in findings between studies.

RESULTS

Twenty-five studies were identified. Heterogeneity in the findings from different studies was evident but was considerably reduced when the asthma and rhinitis analyses were restricted to those studies judged to be of adequate design. The meta-analysis revealed an inverse association between asthma and type 1 diabetes, but the finding only attained significance when analysis was restricted to the studies of adequate design (OR 0.82, 95% CI 0.68-0.99). In this subset an association of similar magnitude was observed between eczema and type 1 diabetes (0.82, 0.62-1.10) although this failed to attain statistical significance, and heterogeneity between studies was still present. There was little evidence of an association between rhinitis and type 1 diabetes (0.97, 0.82-1.16) in this subset of studies.

CONCLUSIONS

Our analysis suggests that there is a small but significant reduction in the prevalence of asthma in children with type 1 diabetes, but the findings for the other atopic diseases are less conclusive.

Virus infections, wheeze and asthma

Viral infections are the most frequent triggers of wheeze and asthma and yet their role in the development of symptoms remains controversial. Pre-existing airway abnormalities contribute to early virus-induced symptoms which usually remit in early childhood, whereas an interaction with airway inflammation causes exacerbations in asthma. However, the distinction between these two groups and the reason why some but not other children wheeze with viral infections is still debated. The effect of early infections on the developing immune system is also complex. The successful maturation of the T-cell response from a predominantly type 2 (atopic predisposition) at birth to a predominantly type 1 (optimal viral immunity) response, is influenced by genetic factors and the number of infections, as both are known to affect outcome. The relative parts played by predisposition and immunomodulation by early infections in later development of asthma are still controversial. These contentions are gradually being resolved by detailed prospective studies.

Virus infections, wheeze and asthma

Viral infections are the most frequent triggers of wheeze and asthma and yet their role in the development of symptoms remains controversial. Pre-existing airway abnormalities contribute to early virus-induced symptoms which usually remit in early childhood, whereas an interaction with airway inflammation causes exacerbations in asthma. However, the distinction between these two groups and the reason why some but not other children wheeze with viral infections is still debated. The effect of early infections on the developing immune system is also complex. The successful maturation of the T-cell response from a predominantly type 2 (atopic predisposition) at birth to a predominantly type 1 (optimal viral immunity) response, is influenced by genetic factors and the number of infections, as both are known to affect outcome. The relative parts played by predisposition and immunomodulation by early infections in later development of asthma are still controversial. These contentions are gradually being resolved by detailed prospective studies.

The C-159T polymorphism in the CD14 promoter is associated with serum total IgE concentration in atopic Chinese children

Activation of macrophages through CD14 by microbes is crucial in inducing immunity by type 1 T helper cells. A C-to-T polymorphism at position -159 of CD14 was associated with serum total IgE level in Caucasians but not in Japanese subjects. The objective of this study is to determine whether this polymorphic marker is associated with atopy and asthma phenotypes in Chinese children. Restriction fragment length polymorphism was used to characterize CD14/-159 genotypes. Microparticle immunoassay was used to measure serum total IgE level; fluorescent enzyme immunoassay was performed to measure serum concentrations of specific IgE to aeroallergens; and enzyme-linked immunosorbent assay was used to measure serum levels of soluble CD14 (sCD14). Lung function in asthmatics was assessed by spirometry. Two hundred and fifty-eight patients and 92 control children were recruited. Their mean serum total IgE concentrations were 331 and 74 kIU/l, respectively (p < 0.0001). Atopy, defined as the presence of at least one allergen-specific IgE in serum, was found in 220 (85%) patients and in 41 (45%) controls (p < 0.0001). Serum sCD14 levels were significantly associated with CD14/-159 genotypes (p = 0.004). Atopic subjects with CC genotype in CD14/-159 had the highest serum total IgE levels compared with CT and TT genotypes, with the respective mean values being 661, 427 and 380 kIU/l (p = 0.015). Similarly, a higher proportion of subjects with CC genotype had increased serum total IgE concentration (p = 0.039). This polymorphic marker was not associated with asthma or aeroallergen sensitization in our cohort. Our results suggest that the C-159T of CD14 was associated with serum total IgE concentration in atopic Chinese children.

Fungal levels in the home and lower respiratory tract illnesses in the first year of life

The association between home dampness and lower respiratory symptoms in children has been well documented. Whether fungal exposures contribute to this association is uncertain. In a prospective birth cohort of 499 children of parents with asthma/allergies, we examined in-home fungal concentrations as predictors of lower respiratory illnesses (LRI) (croup, pneumonia, bronchitis, and bronchiolitis) in the first year. In multivariate analyses, we found a significant increased relative risk (RR) between LRI and high levels (more than the 90th percentile) of airborne Penicillium (RR = 1.73, 95% confidence interval [CI], 1.23, 2.43), dust-borne Cladosporium (RR = 1.52; CI, 1.02, 2.25), Zygomycetes (RR = 1.96; CI, 1.35, 2.83), and Alternaria (RR = 1.51; CI, 1.00, 2.28), after controlling for sex, presence of water damage or visible mold/mildew, born in winter, breastfeeding, and being exposed to other children through siblings. In a multivariate analysis, the RR of LRI was elevated in households with any fungal level at more than the 90th percentile (RR = 1.86; CI, 1.21, 2.88). Exposure to high fungal levels increased the risk of LRI in infancy, even for infants with nonwheezing LRI. Actual mechanisms remain unknown, but fungi and their components (glucans, mycotoxins, and proteins) may increase the risk of LRI by acting as irritants or through increasing susceptibility to infection.

Airway infections in infancy and the presence of allergy and asthma in school age children

AIM

To investigate the association between a history of otitis media and respiratory tract infections in infancy and allergic sensitisation and asthma in school age children of atopic and non-atopic parents.

METHODS

Based on a survey of 4585 schoolchildren, three groups of children aged 6-16 years were selected, of whom 502 were eligible with complete data: (1) diagnosed asthma (n = 166); (2) wheeze within past 12 months (n = 155); and (3) no asthma/no wheeze (n = 181). This study population was further analyzed by subgroups of children with or without parental atopy. Main outcome measures were allergic sensitisation verified by skin prick test and asthma.

RESULTS

Children of atopic parents had a reduced risk of developing allergic sensitisation in school age if they had a combined history of both otitis media and lower respiratory tract infections during infancy (adjusted odds ratio (aOR) 0.13, 95% CI 0.03 to 0.50) or a history of otitis media (aOR 0.31, 95% CI 0.12 to 0.83). A history of lower respiratory tract infections in infancy increased the risk of asthma in children of non-atopic parents (aOR 4.21, 95% CI 1.68 to 10.57).

CONCLUSION

In the present study population, a history of otitis media in infancy seems to be negatively associated with allergic sensitisation in school age children of atopic parents, whereas a history of lower respiratory tract infections was positively associated with asthma in children of non-atopic parents.

Reduced risk of atopic disorders in adults with Helicobacter pylori infection

BACKGROUND

Childhood infections may be necessary to prime the developing immune system in an appropriate manner. In developed countries, the incidence of childhood infections is decreasing, which might explain the observed rise in the prevalence of asthma and other atopic disorders in recent years.

AIM

To determine whether Helicobacter pylori gastritis, a chronic bacterial infection that is usually acquired in early childhood and then persists throughout life, affects the risk of developing asthma and other atopic disorders.

STUDY DESIGN

Cross-sectional study of the prevalence of three atopic disorders in 3244 subjects participating in a community-based, prospective, randomized, controlled trial of H. pylori eradication, the Bristol Helicobacter Project. The presence or absence of active H. pylori infection was determined by the 13C-urea breath test. The prevalence of asthma, eczema and allergic rhinitis was measured by assessing the use of appropriate medications as surrogate markers for these conditions.

RESULTS

There was a 30% reduction in the prevalence of all three atopic disorders in people who had active H. pylori infection, although for each individual atopic disorder the numbers were not quite large enough to reach statistical significance.

CONCLUSIONS

H. pylori infection is associated with a substantially reduced risk of three common atopic disorders. This is further indirect evidence of the importance of childhood infections in influencing the development of a normal immune response. As such infections become progressively less common in developed countries such as the UK, other methods will need to be developed to try to reduce the risk of atopic disorders.

Allergy: the price we pay for cleaner living?

OBJECTIVES

There is an urgent need to identify the environmental changes responsible for the increasing burden of allergic disease. A reduction in the diversity and magnitude of "microbial burden" in early life has been implicated in this growing propensity for allergy sensitization. The "hygiene hypothesis" proposes that deficient bacteria-derived maturation signals during early immune development increases the susceptibility to allergic responses. This article reviews the current evidence for this relationship in the context of improved public health and living conditions.

DATA SOURCES

Evidence derived from a wide range of epidemiologic and intervention studies in humans and experimental animal models is reviewed.

RESULTS

There is extensive epidemiologic evidence linking allergic disease with a number of lifestyle factors that may reflect reduced microbial burden. These studies cannot exclude other possible causal pathways because most parameters (such as family size) are only indirect measures of early childhood infection. However, direct evidence that bacteria can inhibit allergic immune responses provides a plausible mechanistic basis for the hygiene hypothesis. In both animals and humans, microbial antigens can promote nonallergic (type 1) responses and inhibit allergic (type 2) immune responses. These pro-type 1 effects have been used in allergen immunotherapy and other treatments for allergic disease with some success. Although the potential benefits of bacterial exposure appear most relevant in early life when immune responses develop, the role in disease prevention remains controversial. Furthermore, there is currently no evidence that existing childhood vaccine programs to prevent serious infectious disease are responsible for the increase in allergic disease.

CONCLUSIONS

Although microbial antigens can inhibit allergic immune responses, these effects appear to depend on the timing of exposure, the genetic susceptibility of the individual, the nature of the organism, and other poorly defined factors in prevailing environment. Although there is indirect support for the hygiene hypothesis, there is currently no definitive proof that reduced microbial burden is the cause of the current "allergy epidemic."

Overcoming childhood asthma disparities of the inner-city poor

Asthmatic children living in low-income families in United States inner city communities continue to have disproportionately high rates of hospitalizations, emergency department visits, disability, and death. Current research implicates a combination of environmental, biologic, and disease mismanagement factors that underlie these poor outcomes. Multifaceted studies are underway to better understand this inner-city path to severe asthma. Efforts to optimize interventions, to implement them broadly, and to sustain them are also underway on local and national levels. It is hoped that these efforts will limit the severe consequences of asthma, narrow disparities in outcomes, and substantially reduce medical expenditures for asthma.

Atopy, Helicobacter pylori and the hygiene hypothesis

It is uncertain whether the exposure to infections may decrease or increase the risk of allergy development in adult age. According to the hygiene hypothesis, an early childhood infection can down-regulate immunity, suppressing allergic and autoimmune disorders. Novel epidemiological data from a cross-sectional survey show that in subjects with active Helicobacter pylori infection the prevalence of asthma, eczema, allergic rhinitis is lower than in H. pylori-negative subjects. This information is supported by several mechanistic disease models, but is in contrast with previous reports on the association between H. pylori and atopic conditions. The public health relevance of both allergic disorders and H. pylori-related diseases calls for prospective and therapeutic studies. Studies able to show a cause-effect relationship are now essential to bring evidence that might make the case against H. pylori eradication in children and when such intervention is not highly recommended.

Natural history of asthma

For some children, asthma is a disease whose symptoms seem to remit with time. Numerous children, however, develop disease that is persistent throughout their lifetimes and is associated with more severe symptoms, increased airway reactivity, and loss of lung function. These children typically have a family history of asthma and demonstrate increased airways reactivity and atopy in childhood. A clearer picture of the natural history of asthma in the developing child has been derived from the results of several longitudinal studies. Although some questions have been clarified, several questions still remain. Now that the incidence and severity of asthma seem to be increasing, children born in the last 10 years may experience more severe disease or a different pathophysiology than those born 30 to 40 years ago. New cohort studies are needed to assess this possibility. Additional investigations into the genetics of asthma causation will help elucidate the different phenotypic expressions of this complex disease. Once these different phenotypic groups can be identified early in life, further studies can be performed to explore the impact of therapeutic intervention on the severity of asthma symptoms and loss of lung function.