Effects of dog ownership and genotype on immune development and atopy in infancy

Farm animal exposure, respiratory illnesses, and nasal cell gene expression

BACKGROUND

Farm exposures in early life reduce the risks for childhood allergic diseases and asthma. There is less information about how farm exposures relate to respiratory illnesses and mucosal immune development.

OBJECTIVE

We hypothesized that children raised in farm environments have a lower incidence of respiratory illnesses over the first 2 years of life than nonfarm children. We also analyzed whether farm exposures or respiratory illnesses were related to patterns of nasal cell gene expression.

METHODS

The Wisconsin Infant Study Cohort included farm (n = 156) and nonfarm (n = 155) families with children followed to age 2 years. Parents reported prenatal farm and other environmental exposures. Illness frequency and severity were assessed using illness diaries and periodic surveys. Nasopharyngeal cell gene expression in a subset of 64 children at age 2 years was compared to farm exposure and respiratory illness history.

RESULTS

Farm versus nonfarm children had nominally lower rates of respiratory illnesses (rate ratio 0.82 [95% CI, 0.69, 0.97]) with a stepwise reduction in illness rates in children exposed to 0, 1, or ≥2 animal species, but these trends were nonsignificant in a multivariable model. Farm exposures and preceding respiratory illnesses were positively related to nasal cell gene signatures for mononuclear cells and innate and antimicrobial responses.

CONCLUSIONS

Maternal and infant exposure to farms and farm animals was associated with nonsignificant trends for reduced respiratory illnesses. Nasal cell gene expression in a subset of children suggests that farm exposures and respiratory illnesses in early life are associated with distinct patterns of mucosal immune expression.

The Primary Prevention of Atopy: Does Early Exposure to Cats and Dogs Prevent the Development of Allergy and Asthma in Children? A Comprehensive Analysis of the Literature

The current literature shows mixed results relating to the significance of environmental exposure, such as owning a pet, and the development of atopy in children. Our review aimed to collect the most recent evidence on the association between early-life cat and dog ownership and the development of allergy and asthma. A comprehensive literature review was performed using PubMed and Scopus. The search included the main keywords of our PICO: (((early exposure) AND (children) AND (allergy)) OR (asthma)) AND (dog) OR (cat). Randomized controlled trials (RCTs), case-control studies, clinical trials, meta-analyses, and systematic reviews of children within the last five years (2018-2023) were searched and included. During the search process, 52 articles from PubMed and 43 from Scopus were found. A total of 17 articles were deemed to be suitable and included. Fairly consistent results regarding early exposure to pets, in particular dogs, and the prevention of food allergies have been described. Furthermore, there seems to be a protective effect against allergy and asthma in relation to the number of pets owned. The likelihood of a child developing allergy and asthma seems to be influenced by various factors, including the child's genetic background and early exposure to different environmental factors, including allergens that may interact with the gut microbiota and immune system.

The impact of prenatal dog keeping on infant gut microbiota development

INTRODUCTION

Prenatal and early-life dog exposure has been linked to reduced childhood allergy and asthma. A potential mechanism includes altered early immune development in response to changes in the gut microbiome among dog-exposed infants. We thus sought to determine whether infants born into homes with indoor dog(s) exhibit altered gut microbiome development.

METHODS

Pregnant women living in homes with dogs or in pet-free homes were recruited in southeast Michigan. Infant stool samples were collected at intervals between 1 week and 18 months after birth and microbiome was assessed using 16S ribosomal sequencing. Perinatal maternal vaginal/rectal swabs and stool samples were sequenced from a limited number of mothers. Mixed effect adjusted models were used to assess stool microbial community trajectories comparing infants from dog-keeping versus pet-free homes with adjustment for relevant covariates.

RESULTS

Infant gut microbial composition among vaginally born babies became less similar to the maternal vaginal/rectal microbiota and more similar to the maternal gut microbiota with age-related accumulation of bacterial species with advancing age. Stool samples from dog-exposed infants were microbially more diverse (p = .041) through age 18 months with enhanced diversity most apparent between 3 and 6 months of age. Statistically significant effects of dog exposure on β-diversity metrics were restricted to formula-fed children. Across the sample collection period, dog exposure was associated with Fusobacterium genera enrichment, as well as enrichment of Collinsella, Ruminococcus, Clostridaceae and Lachnospiraceae OTUs.

CONCLUSION

Prenatal/early-life dog exposure is associated with an altered gut microbiome during infancy and supports a potential mechanism explaining lessened atopy and asthma risk. Further research directly linking specific dog-attributable changes in the infant gut microbiome to the risk of allergic disorders is needed.

B cell repertoire in children with skin barrier dysfunction supports altered IgE maturation associated with allergic food sensitization

The skin is a major immune organ and skin barrier dysfunction is a major risk factor for the development of the inappropriate immune response seen in allergic disease. Skin barrier disruption alters the landscape of antigens experienced by the immune system and the downstream impacts on the antibody repertoire remain poorly characterized, particularly for the IgE isotype responsible for allergic specificity and in early life, when allergic disease is developing. In this study, we sequenced antibody gene repertoires from a large and well-characterized cohort of children with atopic dermatitis and found that food sensitization was associated with lower mutation frequencies in the IgE compartment. This trend was abrogated in children living with pets during the first year of life. These results elucidate potential molecular mechanisms underlying the protective effects of pet ownership and non-antiseptic environs reported for allergic disease, and the hygiene hypothesis more broadly. We also observed increased IgE diversity and increased isotype-switching to the IgE isotype, suggesting that B cell development, particularly isotype-switching, is heavily altered in the those with food allergen sensitizations relative to those without food allergen sensitizations. Unlike for food antigens, aeroallergen sensitization exhibited no effect on IgE mutation or diversity. Consistent patterns of antibody rearrangement were associated with food allergen sensitization in subjects with atopic dermatitis. Thus, we propose the Immune Repertoire in Atopic Disease (IRAD) score, to quantify this repertoire shift and to aid clinically in patient diagnosis and risk stratification.

[Are pets, dog or cat, a risk or a protector factor for the development or exacerbation of asthma? Systematic review of systematic reviews]

BACKGROUND

Preliminary studies have shown conflicting results on the association between exposure to pets (cat or dog) and asthma. Previous scientific evidence has not been clear to determine if avoiding or allowing the exposure to pets could prevent, improve, or worsen the development of asthma and its symptoms.

OBJECTIVE

To try to explain the controversial relationship between exposure to pets (dog or cat) and its effect on the development of asthma or the exacerbation of symptoms in both children and adults.

METHODS

A standardized search in five electronic databases by an independent reviewer was carried out. The final sample of studies included in the overview of systematic reviews was screened and synthesized through a master table. A narrative description of the results was made.

RESULTS

This systematic review of systematic found determined principally that having a cat could be a risk factor and having a dog a protective factor in the development of asthma. However, early exposure to both cats and dogs (before the age of two) reduces the probability of asthma symptoms and wheezing in the school years. Additionally, having antecedents of sensibilization to pets allergen could be a risk factor to exacerbate asthma in both children and adults.

Associations between fetal or infancy pet exposure and food allergies: The Japan Environment and Children's Study

The hygiene hypothesis suggests that pet exposure is effective in preventing allergic disease, and some studies have reported the beneficial effects of dog exposure during fetal development or early infancy on food allergy. However, the effects of exposure to pets other than dogs on the kinds of food allergies remains unaddressed. This study aimed to explore the effect of exposure to various species of pets on the risk of food allergies. We obtained information on pet exposure and food allergy from the Japan Environment and Children's Study, a nationwide, prospective birth cohort study that included 97,413 mothers and their children. We examined the associations between exposure to various species of pets during fetal development or early infancy and the incidence risk of food allergies. We conducted logistic regression analysis for each pet species, causative food, and timing of exposure. Exposure to dogs or cats during fetal development or early infancy was estimated to reduce the incidence risk of food allergies until the age of 3 years. Dog exposure was estimated to reduce the incidence risk of egg, milk, and nut allergies, and cat exposure was estimated to reduce the incidence risk of egg, wheat, and soybean allergies. However, hamster exposure was estimated to increase the incidence risk of nut allergy. In conclusion, the association between pet exposure and food allergies might differ depending on the pet species and causative food. Continued dog and cat exposure from fetal development to infancy was estimated to reduce the incidence risk of food allergies. The findings of this study shall aid in the design of future studies.

Cord blood immune profile: Associations with higher prenatal plastic chemical levels

Prenatal exposure to plastic chemicals has been associated with alterations to early-life immune function in children. However, previous studies have generally been small and focused on limited repertoires of immune indices. In a large population-based pre-birth cohort (n = 1074), third-trimester measurements of eight phthalate metabolites and three analogues of bisphenols were used to estimate prenatal exposure to phthalate and bisphenol compounds. In cord blood, immune cell populations were measured by flow cytometry and an extensive panel of cytokines and chemokines were measured by multiplex immunoassay. We used these cord blood analytes to estimate "early life" immune profiles. The full study sample comprises data from 774 infants with prenatal plastic metabolite measurements and any cord blood immune data. Multiple linear regression analysis was used to evaluate whether prenatal phthalate and bisphenol exposure was prospectively associated with cord blood immune cell populations and cytokine and chemokine levels. Generally, inverse associations were observed between prenatal phthalate exposure and cord blood immune indices. Higher exposure to di-n-butyl phthalate was associated with lower cord blood levels of platelet-derived growth factor (PDGF) and interferon gamma-induced protein 10 (IP-10); higher exposure to the sum of dibutyl phthalates was associated with lower cord blood levels of IP-10; and higher exposure to benzyl butyl phthalate was associated with lower cord blood levels of interleukin 1 beta (IL-1β). There was less evidence of associations between bisphenols and cord blood immune indices. These results extend previous work examining prenatal plastic chemical exposure and early-life immune development and highlight the importance of further examination of potential associations with health-related outcomes.

Biomass Smoke Exposure and Atopy among Young Children in the Western Highlands of Guatemala: A Prospective Cohort Study

Women and children in rural regions of low-income countries are exposed to high levels of household air pollution (HAP) as they traditionally tend to household chores such as cooking with biomass fuels. Early life exposure to air pollution is associated with aeroallergen sensitization and developing allergic diseases at older ages. This prospective cohort study assigned HAP-reducing chimney stoves to 557 households in rural Guatemala at different ages of the study children. The children's air pollution exposure was measured using personal CO diffusion tubes. Allergic outcomes at 4-5 years old were assessed using skin prick tests and International Study of Asthma and Allergies in Childhood (ISAAC)-based questionnaires. Children assigned to improved stoves before 6 months old had the lowest HAP exposure compared to the other groups. Longer exposure to the unimproved stoves was associated with higher risks of maternal-reported allergic asthma (OR = 2.42, 95% CI: 1.11-5.48) and rhinitis symptoms (OR = 2.01, 95% CI: 1.13-3.58). No significant association was found for sensitization to common allergens such as dust mites and cockroaches based on skin prick tests. Reducing HAP by improving biomass burning conditions might be beneficial in preventing allergic diseases among children in rural low-income populations.

Household size, T regulatory cell development, and early allergic disease: a birth cohort study

BACKGROUND

Children born to larger households have less allergic disease. T regulatory cell (Treg) development may be a relevant mechanism, but this has not been studied longitudinally.

OBJECTIVE

We aim to (i) describe how prenatal and postnatal environmental factors are associated with Treg development and (ii) investigate whether serial Treg measures predict allergic outcomes at 1 year of age.

METHODS

A birth cohort (n = 1074) with information on prenatal and postnatal early life factors. Both naïve Treg (nTreg) and activated Treg (aTreg) cell populations (as a proportion of CD4⁺ T cells) were available in 463 infants at birth (cord blood), 600 at 6 months, and 675 at 12 months. 191 infants had serial measures. Measures of allergic status at 12 months were polysensitization (sensitization to 2 or more allergens), clinically proven food allergy, atopic eczema, and atopic wheeze.

RESULTS

Infants born to larger households (3 or more residents) had higher longitudinal nTreg proportions over the first postnatal year with a mean difference (MD) of 0.67 (95% CI 0.30-1.04)%. Higher nTreg proportions at birth were associated with a reduced risk of infant allergic outcomes. Childcare attendance and breastfeeding were associated with higher longitudinal nTreg proportions (MD 0.48 (95% CI 0.08-0.80)%.

CONCLUSION

Multiple prenatal and postnatal microbial factors are associated with nTreg and aTreg development. Larger household size was associated with higher nTreg at birth which in turn was associated with reduced allergic sensitization and disease at 12 months of age.

Spatial-Temporal Accessibility and Inequality of Veterinary Service in Hong Kong: A Geographic Information System-Based Study

Veterinary services are vital to the welfare of pets and their owners. Previous studies examined multiple factors affecting pet owners' decision to consult veterinarians, yet few studied the spatial accessibility of veterinary services. This study is one of the pioneering studies on the spatial-temporal accessibility of veterinary service and how it is associated with social and spatial inequality in Hong Kong. We measured the spatial availability and accessibility of both general and 24/7 veterinary clinics (i.e., veterinary clinics offering service for 24 hours, seven days a week or providing emergency services outside of business hours) using Geographic Information System and principal component analysis. We found that the spatial distribution pattern of general and 24/7 veterinary clinics can be explained by the average district-to-district distances and the area of a district. In addition, social and spatial inequality of access to veterinary services were observed. The spatial accessibility of general veterinary clinics within walking distance is negatively correlated with household size and the number of public-housing and subsidized-housing households, but positively correlated with the number of private-housing households. The spatial availability and accessibility of 24/7 veterinary service are positively correlated with the number of private housing households and households with the highest monthly household income, and the latter also positively correlates with a population with a post-secondary degree, further shedding light on the social and spatial inequality issue that communities with wealthier households and highly educated populations have more accessibility to 24/7 veterinary services. Last, we argue that the need-based veterinary support tends to target remote rural areas while overlooking the new growth areas close to the traditional urban core but poor in accessibility to veterinary care. Therefore, a comprehensive investigation into the pet ownership landscape and their needs over space and time will be beneficial to construct a more robust animal welfare system in Hong Kong.

Associations between maternal and environmental exposures on atopic disease in the offspring of mothers with asthma

Background and Objective

Available data on the impact of perinatal and environmental factors on atopic diseases in the offspring are sparse and conflicting. We, therefore, investigated the impact of these factors on the risk of atopic diseases in the offspring of women with asthma.

Methods

Pregnant women referred to give birth at Copenhagen University Hospital‐Hvidovre, Denmark, have since 2007 been invited to participate in the Management of Asthma during Pregnancy program. Women with diagnosed asthma, currently prescribed asthma medication, first visit to the respiratory out‐patient clinic within the first 18 weeks of pregnancy that completed an online questionnaire about atopic diseases in their child were included in the current study.

Results

Five hundred and seventy‐one pregnancies were included. Among the off‐spring, 113 children (21%) had doctor‐diagnosed asthma, 178 (31%) atopic dermatitis (AD), and 55 (32%) both AD and doctor‐diagnosed asthma. AD in the offspring was associated with having a dog at home (odds ratio [OR], 2.56; 95% confidence interval [CI], [1.40–4.67], p = .002), whereas having a cat at home was associated with a higher risk of asthma in the offspring (OR, 2.16; 95% CI, [1.14–4.11], p = .02). The associations remained significant after adjusting for maternal age, smoking status, allergy, treatment with inhaled corticosteroids, forced expiratory volume in 1 s less than 80% predicted, uncontrolled asthma, and history of pre‐pregnancy asthma exacerbations. No association was found between gestational weight gain (GWG) in first trimester and total GWG and atopic disease in the offspring.

Conclusion

Having pets at home is associated with AD and asthma in the offspring of mothers with asthma.

Dogs as Pets and Pests: Global Patterns of Canine Abundance, Activity, and Health

Dogs (Canis familiaris) were the first domesticated species and, at an estimated population of 1 billion individuals, are globally ubiquitous today. Describing the tremendous morphometric diversity and evolutionary origins of dogs is a scientific endeavor that predates Darwin, yet our interdisciplinary understanding of the species is just beginning. Here, I present global trends in dog abundance, activity, and health. While the human-dog relationship has for millennia been close, it is also complicated. As pets, companion dogs are often treated as family members and constitute the largest sector of the ever-growing >$200 billion USD global pet care industry. As pests, free-roaming dogs are an emerging threat to native species via both predation and nonconsumptive effects (e.g., disturbance, competition for resources, and hybridization). Furthermore, I briefly discuss mounting evidence of dogs as not only infectious disease reservoirs but also as bridges for the transmission of pathogens between wild animals and humans in zoonotic spillover events, triggering intensive dog population management strategies such as culling. Dog mobility across the urban-wildland interface is an important driver for this and other adverse effects of canines on wildlife populations and is an active topic of disease ecologists and conservation biologists. Other canine scientists, including veterinary clinicians and physiologists, study more mechanistic aspects of dog mobility: the comparative kinetics, kinematics, and energetics of dog locomotor health. I outline the prevalent methodological approaches and breed-specific findings within dog activity and health research, then conclude by recognizing promising technologies that are bridging disciplinary gaps in canine science.

Sensitization to peanut, egg or pets is associated with skin barrier dysfunction in children with atopic dermatitis

BACKGROUND

Children with atopic dermatitis (AD) are often sensitized to food and aeroallergens, but sensitization patterns have not been analysed with biologic measures of disease pathogenicity.

OBJECTIVE

We sought to define allergen sensitization grouping(s) using unbiased machine learning and determine their associations with skin filaggrin (FLG) and transepidermal water loss (TEWL) (assesses skin barrier integrity), S100A8 and S100A9 expression (assesses skin inflammation) and AD severity.

METHODS

We studied 400 children with AD in the Mechanisms of Progression from Atopic Dermatitis to Asthma in Children (MPAACH) cohort to identify groupings of food and aeroallergen sensitizations. MPAACH is a paediatric AD cohort, aged 1-2, recruited through hospital/community settings between 2016 and 2018. We analysed these groupings' associations with AD biomarkers: skin FLG, S100A8 and S100A9 expression, total IgE, TEWL and AD severity.

RESULTS

An unbiased machine learning approach revealed five allergen clusters. The most common cluster (N = 131), SPT_PEP, had sensitization to peanut, egg and/or pets. Three low prevalence clusters, which included children with allergen sensitization other than peanut, egg or pets, were combined into SPT_Other . SPT_NEG included children with no sensitization(s). SPT_PEP children had higher median non-lesional TEWL (16.9 g/m² /h) and IgE (90 kU/L) compared with SPT_OTHER (8.8 g/m² /h and 24 kU/L; p = .01 and p < .001) and SPT_NEG (9 g/m² /h and 26 kU/L; p = .003 and p < .001). SPT_PEP children had lower median lesional (0.70) and non-lesional (1.09) FLG expression compared with SPT_OTHER (lesional: 0.9; p = .047, non-lesional: 1.78; p = .01) and SPT_NEG (lesional: 1.47; p < .001, non-lesional: 2.21; p < .001). There were no differences among groupings in S100A8 or S100A9 expression.

CONCLUSIONS AND CLINICAL RELEVANCE

In this largely clinic-based cohort of young children with AD, allergic sensitization to peanut, egg, cat or dog was associated with more severe disease and skin barrier function but not markers of cutaneous inflammation. These data need replicating in a population-based cohort but may have important implications for understanding the interaction between AD and allergic sensitization.

Association between pet ownership and physical activity levels, atopic conditions, and mental health in Singapore: a propensity score-matched analysis

Although existing literature increasingly suggests a positive influence of pet ownership on human physical activity levels, results from many European, American, and Japanese studies have been inconsistent. How pet ownership impacts mental health and atopy is likewise controversial and whether distinct demographic subgroups experience differential effects is unclear. This cross-sectional study surveyed participants (n = 823) via a self-administered online questionnaire. Comparisons of outcomes between pet owners and non-pet owners with subgroup analyses were performed within a propensity score-matched subset (n = 566) of respondents. There were no differences in physical activity levels or mental health scores between pet owners and non-pet owners. In subgroup analyses, compared to non-pet owners, main pet caregivers reported 14.1 (95% CI 2.79–25.3) and 19.0 (95% CI 4.70–33.3) more minutes per week of moderate- and vigorous-intensity physical activity respectively and higher SF-36 emotional well-being (β = 2.7, 95% CI 0.100–5.32) and energy scores (β = 3.8, 95% CI 0.410–7.27). Age was a significant effect modifier of the association between pet ownership and emotional well-being, energy and social functioning scores, with greater scores above the ages of 39, 35 and 39 years old respectively (interaction p = 0.043, 0.044, 0.042). Finally, pet acquisition was associated with worsening of allergic rhinitis, while pet ownership cessation was associated with improvement of allergic rhinitis and eczema symptoms. To our knowledge, this is the first study addressing the public health impact of pet ownership in Southeast Asia and its findings add contextual nuance to suggest potential benefits derived from pet ownership.

Patterns of farm exposure are associated with reduced incidence of atopic dermatitis in early life

BACKGROUND

Farm exposures may reduce the risk of atopic dermatitis (AD) in children, but this is controversial and US data are limited.

OBJECTIVE

This study was conducted to identify patterns of farm exposure in Wisconsin family farms that modify AD incidence and prevalence in early childhood.

METHODS

Environmental exposures, health history, and clinical outcomes were prospectively recorded for 111 farm families and 129 non-farm families enrolled in the Wisconsin Infant Study Cohort birth cohort study. Exposures from the prenatal and early postnatal (2-month) visits were evaluated together with parental report of AD diagnosis by a health care provider through age 24 months. Latent class analysis was performed with prenatal and early postnatal farm-exposure variables to assign farm children to 3 classes.

RESULTS

Overall, children of farm families had reduced AD incidence (P = .03). Within farm families, exposures including poultry (3% vs 28%; P = .003), pig (4% vs 25%; P = .04), feed grain (13% vs 34%; P = .02), and number of animal species were inversely associated with AD incidence. Among the latent class groups, children in families with diverse or more intense farm exposures (classes A and B) had reduced AD incidence, whereas low-exposure (class C) infants had AD incidence similar to that in nonfarm children.

CONCLUSIONS

Infants in Wisconsin farm families had reduced AD incidence, and patterns of farm exposures further defined AD risk. These findings suggest that exposure to diverse farm animals, feed, and bedding during the prenatal period and in early infancy reduce the risk of early-onset AD, a phenotype associated with multiple other atopic diseases.

Effect of Exposure to Cats and Dogs on the Risk of Asthma and Allergic Rhinitis: A Systematic Review and Meta-analysis

BACKGROUND

Controversies persist regarding whether exposure to cat or dog increases the risk of asthma and allergic rhinitis.

OBJECTIVE

This meta-analysis aimed to assess the associations between exposure to cats or dogs and the development of asthma and allergic rhinitis.

METHODS

A systematic review was performed to identify case-control and cohort studies before May 2019, evaluating the association between exposure to cats and dogs and the risk of asthma and rhinitis. The risk of bias was assessed using the Newcastle-Ottawa Scale. The odds ratios (ORs) and risk ratios (RRs) were pooled for case-control and cohort studies, respectively. Subgroup analyses were performed on prespecified study-level characteristics.

RESULTS

The meta-analysis of 34 cohort studies showed a protective role of exposure to cats [RR: 0.88, 95% confidence interval (CI): 0.77-0.99] or dogs (RR: 0.85, 95% CI: 0.73-0.97) in the development of asthma. The subgroup analysis of birth cohort (RR: 0.74, 95% CI: 0.56-0.93) and children population (RR: 0.83, 95% CI: 0.70-0.96) also suggested a favorable role of exposure to dogs in the development of asthma. Pooled evidence from 13 case-control studies indicated no significant impact of cats (OR: 1.66, 95% CI: 0.39-2.94) and dogs (OR: 1.22, 95% CI: 0.92-1.52) on the development of asthma. A pooled analysis of five cohort studies showed a favorable effect of exposure to cats (RR: 0.60, 95% CI: 0.33-0.86) or dogs (RR: 0.68, 95% CI 0.44-0.90) on the development of allergic rhinitis.

CONCLUSION

The findings indicated a protective effect of exposure to cats and dogs, especially ownership, on the development of asthma and allergic rhinitis.

Yard vegetation is associated with gut microbiota composition

Gut microbes play an essential role in the development and functioning of the human immune system. A disturbed gut microbiota composition is often associated with a number of health disorders including immune-mediated diseases. Differences in host characteristics such as ethnicity, living habit and diet have been used to explain differences in the gut microbiota composition in inter-continental comparison studies. As our previous studies imply that daily skin contact with organic gardening materials modify gut microflora, here we investigated the association between living environment and gut microbiota in a homogenous western population along an urban-rural gradient. We obtained stool samples from 48 native elderly Finns in province Häme in August and November 2015 and identified the bacterial phylotypes using 16S rRNA Illumina MiSeq sequencing. We assumed that yard vegetation and land cover classes surrounding homes explain the stool bacterial community in generalized linear mixed models. Diverse yard vegetation was associated with a reduced abundance of Clostridium sensu stricto and an increased abundance of Faecalibacterium and Prevotellaceae. The abundance of Bacteroides was positively and strongly associated with the built environment. Exclusion of animal owners did not alter the main associations. These results suggest that diverse vegetation around homes is associated with health-related changes in gut microbiota composition. Manipulation of the garden diversity, possibly jointly with urban planning, is a promising candidate for future intervention studies that aim to maintain gut homeostasis.

Shaping of infant B cell receptor repertoires by environmental factors and infectious disease

Antigenic exposures at epithelial sites in infancy and early childhood are thought to influence the maturation of humoral immunity and modulate the risk of developing immunoglobulin E (IgE)-mediated allergic disease. How different kinds of environmental exposures influence B cell isotype switching to IgE, IgG, or IgA, and the somatic mutation maturation of these antibody pools, is not fully understood. We sequenced antibody repertoires in longitudinal blood samples in a birth cohort from infancy through the first 3 years of life and found that, whereas IgG and IgA show linear increases in mutational maturation with age, IgM and IgD mutations are more closely tied to pathogen exposure. IgE mutation frequencies are primarily increased in children with impaired skin barrier conditions such as eczema, suggesting that IgE affinity maturation could provide a mechanistic link between epithelial barrier failure and allergy development.

Markers of microbial exposure lower the incidence of atopic dermatitis

BACKGROUND

The hygiene hypothesis proposes that reduced exposure to infectious agents in early life would explain the increase of allergic and autoimmune diseases observed over the past decades in high-income countries.

METHODS

We conducted a matched case-control study on incident atopic dermatitis (AD). Cases were 426 outpatient children with a first diagnosis of incident AD. Controls were 426 children attending a pediatric/dermatological visit for nonatopic disorders matched to cases (1:1). Particular attention was paid to the time elapsed between the markers of microbial exposure and disease onset, and we considered for controls the same time window of exposures from birth as his/her matched case. Odds ratios (ORs) were computed using multivariable conditional logistic regression models, according to center, sex, age, and period of enrollment, and including as potential confounders a family history of any allergy in parents, type of delivery, having siblings, keeping pets, age at weaning, and having had ≥4 infections.

RESULTS

The OR of AD first occurrence was 0.35 (P-value = .039) for children who had experienced ≥4 infections compared with those with no infections. A decreasing trend in risk was observed with increasing number of siblings (P-value = .023), the protective effect reaching about 40% for children with 2 or more siblings (OR = 0.62; P-value = .048). Pet keeping, in particular daily contact with dogs, was inversely associated with AD risk (OR = 0.40; P-value = .004).

CONCLUSIONS

These results support the hygiene hypothesis in its broad sense. Early-life environmental exposures, including pathogens and commensals, act as "microbes contact carriers" influencing immune system balance early in life.

Early Life Domestic Pet Ownership, and the Risk of Pet Sensitization and Atopic Dermatitis in Preschool Children: A Prospective Birth Cohort in Shanghai

Background: Although domestic pet ownership is on the rise, the impact of early life pet ownership on children's pet sensitization and atopic dermatitis (AD) remains controversial. Methods: Shanghai Allergy Cohort is an ongoing prospective study followed up to the age of 5 years. Pregnant mothers were recruited and their offspring were followed up every year by a group of pediatricians. Information on furred pet ownership was collected by the questionnaire. AD was diagnosed by dermatologists according to disease history and Williams criteria at 5 years ± 1 months. Skin prick test (SPT) was performed to determine sensitization to specific allergens. Multiple logistic regression models were used to evaluate the associations between pet ownership and AD, dog/cat sensitization. Results: In the 538 children at preschool age, 112 (20.82%) were diagnosed with AD. Dermatophagoides pteronyssinus and Dermatophagoides farina were the most common allergens, and almost 10% of children were positive to dog and cat. The percentage of positive SPT reactors at 5-year old was 65.28% in the group of children with AD, higher than that in non-AD group (44.57%). Domestic pet ownership at both infant and preschool period was positively associated with an increased risk of sensitization to dog (OR _adjusted = 2.85 [95% CI: 1.08-7.50 for infant exposure], OR _adjusted = 2.73 [95% CI: 1.33-5.61] for preschool exposure), and interestingly, pet ownership at infant period negatively associated with higher risk of AD at 5-year old (OR adjusted = 0.33 [95% CI: 0.12-0.88]). Conclusion: This is the first prospective birth cohort study in Shanghai that found half of preschool children had positive allergen sensitization even in the non-AD children. Although early life exposure to dog may increase the risk of dog sensitization, it significantly decreased the risk of AD. The underlying mechanisms warrant further investigations.

Birth Mode, Breastfeeding, Pet Exposure, and Antibiotic Use: Associations With the Gut Microbiome and Sensitization in Children

PURPOSE OF REVIEW

The infant gut microbiota has become a focus of multiple epidemiologic and cohort studies. This microbiome is derived from the mother (via the vaginal canal, maternal skin contact, breastfeeding, and possibly in utero microbial transfer) and is likely influenced by multiple external factors. It is now believed by some experts that colonization and formation of the newborn and alterations of gut microbiota in children are dependent on earlier alterations of the microbiota of mothers during or perhaps even before pregnancy. This review will focus on specific factors (pet keeping, breastfeeding, antibiotic use, and mode of delivery) that influence the infant gut microbiome and atopy.

RECENT FINDINGS

This is a review of recent literature describing how pet keeping, breastfeeding, antibiotic use, and mode of delivery influences and changes the infant gut microbiome and atopy. General trends in gut microbiota differences have emerged in different birth cohorts when each external factor is analyzed, but consistency between studies is difficult to replicate. The aforementioned factors do not seem to confer an overwhelming risk for development of atopy alone. This review provides a comprehensive review of early life environmental factors and their influence on the infant gut microbiome and atopy.

Report from the National Institute of Allergy and Infectious Diseases workshop on "Atopic dermatitis and the atopic march: Mechanisms and interventions"

Atopic dermatitis (AD) affects up to 20% of children worldwide and is an increasing public health problem, particularly in developed countries. Although AD in infants and young children can resolve, there is a well-recognized increased risk of sequential progression from AD to other atopic diseases, including food allergy (FA), allergic rhinitis, allergic asthma, and allergic rhinoconjunctivitis, a process referred to as the atopic march. The mechanisms underlying the development of AD and subsequent progression to other atopic comorbidities, particularly FA, are incompletely understood and the subject of intense investigation. Other major research objectives are the development of effective strategies to prevent AD and FA, as well as therapeutic interventions to inhibit the atopic march. In 2017, the Division of Allergy, Immunology, and Transplantation of the National Institute of Allergy and Infectious Diseases sponsored a workshop to discuss current understanding and important advances in these research areas and to identify gaps in knowledge and future research directions. International and national experts in the field were joined by representatives from several National Institutes of Health institutes. Summaries of workshop presentations, key conclusions, and recommendations are presented herein.

Dog introduction alters the home dust microbiota

Research has largely reported that dog exposure is associated with reduced allergic disease risk. Responsible mechanism(s) are not understood. The goal was to investigate whether introducing a dog into the home changes the home dust microbiota. Families without dogs or cats planning to adopt a dog and those who were not were recruited. Dust samples were collected from the homes at recruitment and 12 months later. Microbiota composition and taxa (V4 region of the 16S rRNA gene) were compared between homes that did and did not adopt a dog. A total of 91 dust samples from 54 families (27 each, dog and no dog; 17 dog and 20 no dog homes with paired samples) were analyzed. A significant dog effect was seen across time in both unweighted UniFrac and Canberra metrics (both P = .008), indicating dog introduction may result in rapid establishment of rarer and phylogenetically related taxa. A significant dog-time interaction was seen in both weighted UniFrac (P < .001) and Bray-Curtis (P = .002) metrics, suggesting that while there may not initially be large relative abundance shifts following dog introduction, differences can be seen within a year. Therefore, dog introduction into the home has both immediate effects and effects that emerge over time.

Consensus document on dog and cat allergy

The prevalence of sensitization to dogs and cats varies by country, exposure time and predisposition to atopy. It is estimated that 26% of European adults coming to the clinic for suspected allergy to inhalant allergens are sensitized to cats and 27% to dogs. This document is intended to be a useful tool for clinicians involved in the management of people with dog or cat allergy. It was prepared from a consensus process based on the RAND/UCLA method. Following a literature review, it proposes various recommendations concerning the diagnosis and treatment of these patients, grounded in evidence and clinical experience. The diagnosis of dog and cat allergy is based on a medical history and physical examination that are consistent with each other and is confirmed with positive results on specific IgE skin tests. Sometimes, especially in polysensitized patients, molecular diagnosis is strongly recommended. Although the most advisable measure would be to avoid the animal, this is often impossible and associated with a major emotional impact. Furthermore, indirect exposure to allergens occurs in environments in which animals are not present. Immunotherapy is emerging as a potential solution to this problem, although further supporting studies are needed.

Exposure and Sensitization to Pets Modify Endotoxin Association with Asthma and Wheeze

BACKGROUND

Pets are major contributors of endotoxin in homes, but whether they influence endotoxin association with respiratory outcomes is unclear.

OBJECTIVE

To examine whether exposure and sensitization to dog and cat modify the relationship between endotoxin exposure and asthma and wheeze.

METHODS

We analyzed data from 6051 participants in the 2005-2006 cycle of the National Health and Nutrition Examination Survey (NHANES). House dust from bedroom floor and bedding was evaluated for endotoxin and for dog (Canis familiaris 1) and cat (Feline domesticus 1) allergens. The NHANES also collected data on respiratory outcomes and measured IgE specific to allergens. Associations of log-endotoxin and pet exposure with respiratory outcomes were examined, adjusting for covariates including pet avoidance.

RESULTS

Dog and cat ownership among participants was 48.3% and 37.5%, respectively. Endotoxin geometric mean (SE) was 15.49 (0.50) EU/mg. Endotoxin and pet allergen levels were significantly higher in households with a dog or cat. Overall, endotoxin was positively associated with wheeze (odds ratio [OR], 1.30; 95% CI, 1.04-1.62), but not with asthma. However, in participants nonsensitized to dog, the odds of endotoxin association with wheeze were higher with exposure to dog allergen (OR, 1.80; 95% CI, 1.27-2.53; P_interaction = .048). In participants sensitized to cat and exposed to cat allergen, endotoxin became positively associated with asthma (OR, 1.92; 95% CI, 1.21-3.0; P_interaction = .040). With coexposure to dog and cat allergens, endotoxin association with asthma and wheeze was exacerbated (OR, 2.00; 95% CI, 1.04-3.83; P_interaction = .012 and OR, 1.88; 95% CI, 1.32-2.66; P_interaction = .016, respectively).

CONCLUSIONS

Exposure to dog and cat allergens enhances the association of endotoxin with asthma and wheeze.

Asthma Genetics in the Post-GWAS Era

Genome-wide association studies (GWAS) of asthma have yielded exciting results and identified novel risk alleles and loci. But, like other common complex diseases, asthma-associated alleles have small effect sizes and account for little of the prevalence of asthma. In this review, I discuss the limitations of GWAS approaches and the major challenges facing geneticists in the post-GWAS era and propose alternative strategies to address these challenges. In particular, I propose that focusing on genetic variations that influences gene expression and using cell models of gene-environment interactions in cell types that are relevant to asthma will allow us to more completely characterize the genetic architecture of asthma.

Domestic dog exposure at birth reduces the incidence of atopic dermatitis

BACKGROUND

While the etiopathogenesis of atopic dermatitis is complex and poorly understood, neonatal exposures are important for disease occurrence. However, the effect of dog exposure on the risk of atopic dermatitis is unresolved.

OBJECTIVE

We investigated whether domestic dog exposure affected the risk of atopic dermatitis in children during the first 3 years of life.

METHODS

Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) are ongoing prospective clinical birth cohort studies. Data from 411 children born to mothers with asthma (COPSAC₂₀₀₀ ) and 700 unselected children (COPSAC₂₀₁₀ ) were analyzed following the same protocols at the same research site. Atopic dermatitis was diagnosed prospectively according to the Hanifin-Rajka criteria. Parental history of asthma, eczema, or rhinitis was defined by self-reported physician diagnosis. In the COPSAC₂₀₀₀ , maternal specific serum IgE against eight inhalant allergens was sampled after the children's birth and at pregnancy week 24 in the COPSAC₂₀₁₀ cohort. Associations between dog exposure and atopic dermatitis were analyzed by Cox proportional hazard regression models and adjusted for lifestyle confounders.

RESULTS

In the COPSAC₂₀₀₀ and COPSAC₂₀₁₀ cohorts, the risk of atopic dermatitis was significantly lower in children with domestic dog exposure (_adjusted HR = 0.46 [0.25-0.87], P = 0.02; and _adjusted HR = 0.58 [0.36-0.93], P = 0.03, respectively). The risk of atopic dermatitis decreased in a dose-dependent manner with increasing number of dogs (_adjusted HR = 0.58 [0.38-0.89], P = 0.01) in the COPSAC₂₀₁₀ . The protective effect was restricted to children born to mothers with atopic disease in the unselected COPSAC₂₀₁₀ cohort (_adjusted HR = 0.39 [0.19-0.82], P = 0.01), as no effect was observed in children born to mothers without atopic disease (_adjusted HR = 0.92 [0.49-1.73], P = 0.79). Paternal atopic status did not affect the risk of atopic dermatitis. We found no significant interaction between the CD14 T/T genotype and domestic dog exposure in either cohort (COPSAC₂₀₀₀ , P = 0.36; and COPSAC₂₀₁₀ cohort, P = 0.42).

CONCLUSION

Neonatal domestic dog exposure was associated with a strongly reduced risk of atopic dermatitis in two independent birth cohorts and in a dose-dependent manner. While the mechanisms involved are unclear, our findings raise the question of whether in utero exposures may affect the risk of atopic dermatitis and emphasize the importance of the early environment for disease trajectory.

Racial differences in pet ownership in families of children with asthma

BACKGROUND

Exposure to household domestic animals such as cats and dogs in early life may have some role in pathogenesis of asthma. Racial differences exist in the prevalence of asthma. We hypothesized that there may also be racial differences in pet ownership in families with asthma.

METHODS

A cross sectional study was conducted from June 2011 to December 2014 on 823 of 850 (97%) families of children with asthma for pet ownership. Comparisons among racial groups were done using chi square analysis and one-way analysis of variance.

RESULTS

The mean age of the cohort was 6.9±4.4 years. A total of 540 (65.62%) patients were Caucasian, 195 (23.7%) African American, 42 (5.1%) hispanics, and 26 (3.2%) biracial with one Caucasian parent. Pets in the home were reported by 470 (58.5%) households. Significantly fewer African American and hispanic families had pets in the home (26.9% and 44.7%) than biracial and Caucasian families (72% and 69.9%, P<0.001). Likewise, significantly more biracial and Caucasian families were noted to have dogs (52% and 54.4%) or cats (25.4% and 40%) or both cats and dogs (28% and 18%) than African Americans families (20.3%, P<0.001; 7.1%, P<0.001) and (4.6%, P<0.001), respectively.

CONCLUSIONS

Among families with asthmatic children, pet ownership is significantly more likely in Caucasian families compared with African-American and Hispanic families, thus there is a racial diversity in pet ownership among families of children with asthma.

Pet Ownership and Cancer Risk in the Women's Health Initiative

BACKGROUND

Pet ownership and cancer are both highly prevalent in the United States. Evidence suggests that associations may exist between this potentially modifiable factor and cancer prevention, though studies are sparse. The present report examined whether pet ownership (dog, cat, or bird) is associated with lower risk for total cancer and site-specific obesity-related cancers.

METHODS

This was a prospective analysis of 123,560 participants (20,981 dog owners; 19,288 cat owners; 1,338 bird owners; and 81,953 non-pet owners) enrolled in the Women's Health Initiative observational study and clinical trials. Cox proportional hazards models were used to estimate HR and 95% confidence intervals for the association between pet ownership and cancer, adjusted for potential confounders.

RESULTS

There were no significant relationships between ownership of a dog, cat, or bird and incidence of cancer overall. When site-specific cancers were examined, no associations were observed after adjustment for multiple comparisons.

CONCLUSION

Pet ownership had no association with overall cancer incidence.

IMPACT

This is the first large epidemiologic study to date to explore relationships between pet ownership and cancer risk, as well as associated risks for individual cancer types. This study requires replication in other sizable, diverse cohorts. Cancer Epidemiol Biomarkers Prev; 25(9); 1311-6. ©2016 AACR.

Incidence and risk factors for food hypersensitivity in UK infants: results from a birth cohort study

BACKGROUND

The prevalence of food hypersensitivity in the UK is still largely open to debate. Additionally its pathogenesis is also unclear although it is known that there are differing phenotypes. Determining its prevalence, along with identifying those factors associated with its development will help to assess its clinical importance within the national setting and also add to the debate on appropriate prevention strategies.

METHODS

A population based birth cohort study conducted in Hampshire, UK as part of the EuroPrevall birth cohort study. 1140 infants were recruited with 823 being followed up until 2 years of age. Infants with suspected food reactions were assessed including specific IgE measurement and skin prick testing. Diagnosis of food hypersensitivity was by positive double-blind, placebo-controlled food challenge (DBPCFC) where symptoms up to 48 h after the end of the food challenge were considered indicative of a food hypersensitivity. Factors associated with food hypersensitivity and its two phenotypes of IgE-mediated and non-IgE-mediated disease were modelled in a multivariable logistic regression analysis.

RESULTS

Cumulative incidence of food hypersensitivity by 2 years of age was 5.0 %. The cumulative incidence for individual food allergens were hens' egg 2.7 % (1.6-3.8); cows' milk 2.4 % (1.4-3.5); peanut 0.7 % (0.1-1.3); soy 0.4 % (0.0-0.8); wheat 0.2 % (0.0-0.5) and 0.1 % (0.0-0.32) for fish. The cumulative incidence of IgE-mediated food allergy was 2.6 % with 2.1 % reacting to hens' egg. For non-IgE-mediated food allergy the cumulative incidence was 2.4 % (cows' milk 1.7 %). Predictors for any food hypersensitivity were wheeze, maternal atopy, increasing gestational age, age at first solid food introduction and mean healthy dietary pattern score. Predictors for IgE mediated allergy were eczema, rhinitis and healthy dietary pattern score whereas for non-IgE-mediated food allergy the predictors were dog in the home, healthy dietary pattern score, maternal consumption of probiotics during breastfeeding and age at first solid food introduction.

CONCLUSIONS

Just under half the infants with confirmed food hypersensitivity had no demonstrable IgE. In an exploratory analysis, risk factors for this phenotype of food hypersensitivity differed from those for IgE-mediated food allergy except for a healthy infant diet which was associated with less risk for both phenotypes.

Environmental exposures and family history of asthma

BACKGROUND

Asthma pathogenesis is a complex interaction of genetic, ethnic, environmental and social/life style risk factors.

AIM

The goal of this study was to identify associations, if any, in children with asthma, between environmental risk factors (exposure to second-hand tobacco smoke (STS), pet ownership, race and a family history of asthma.

METHODS

After IRB approval, from June 2011 to December 2014, 823 children with asthma were enrolled in this prospective cross sectional study. At the initial visit, families completed a questionnaire with information on family history of asthma, having a pet at home and exposure to STS by parents at home. Chi square analyses were calculated, with alpha level of significance ≤0.05.

RESULTS

History of asthma in parents, siblings or grandparents was reported by 575 (69.8%) patients including father (n = 154, 17.8%) and mother (n = 235, 26.5%). Children with family history of asthma (n = 575) were significantly more likely to have a pet at home and exposure to STS (n = 347, 60.3% and n = 198, 34.4%, respectively) compared to families without a history of asthma (n = 124, 50%, p = 0.006 and n = 44, 17.7%, p < 0.001, respectively). Similarly, asthmatic children with exposure to STS (n = 241) were significantly more likely to have a pet at home and a family history of asthma (n = 153, 63.5% and n = 197, 81.7%, respectively) compared to children with no STS exposure (n = 315, 55.5%, p = 0.034 and n = 371, 65.3%, p < 0.001 respectively).

CONCLUSIONS

Significantly more asthmatic children with immediate relatives with a history of asthma have a pet at home and experience STS exposure compared to children without relatives with a history of asthma, suggesting association between life style choices/environmental exposures and family history of asthma.

Assessment of pet exposure by self-report in epidemiological studies of allergy and asthma: a systematic review

OBJECTIVE

In epidemiological studies that aim to investigate the relationship between pet exposure and allergy/asthma, pet exposure is often ascertained by means of a questionnaire, but it is unclear which questionnaire items are used. The objective of this study was to systematically review self-reported pet exposure assessment in questionnaires used in epidemiological studies which explore the associations between pets and allergy/asthma.

METHODS

A systematic literature search was conducted in PubMed and papers were selected according to pre-specified eligibility criteria. The pet exposure questions used were classified within a framework including direct pet contact, indirect pet contact (e.g. through carers or grandparents) and avoidance behaviour. Authors were contacted when the questions used were not reported in detail.

RESULTS

Ninety-six full text papers were systematically reviewed. All studies assessed direct pet contact, but less than half (45%) explicitly assessed whether pets were allowed indoors. The vast majority of studies assessed both pet exposures during the first year of life and after the first year of life. The minority (13%) assessed whether pet(s) were kept at places regularly visited by the child and pet exposure in utero (15%). Even fewer studies assessed indirect contact to pets (n = 8) and avoidance behaviour (n = 10).

CONCLUSIONS

In epidemiological studies, the ascertainment of pet exposure through questionnaires appears to vary greatly. This variation might partly explain the inconsistent and contradictory results of the effects of pet exposure on the development of allergy and asthma.

Promising candidates for allergy prevention

Recent advances in understanding environmental risk factors for allergic diseases in children have led to renewed efforts aimed at prevention. Factors that modify the probability of developing allergies include prenatal exposures, mode of delivery, diet, patterns of medication use, and exposure to pets and farm animals. Recent advances in microbial detection techniques demonstrate that exposure to diverse microbial communities in early life is associated with a reduction in allergic disease. In fact, microbes and their metabolic products might be essential for normal immune development. Identification of these risk factors has provided new targets for prevention of allergic diseases, and possibilities of altering microbial exposure and colonization to reduce the incidence of allergies is a promising approach. This review examines the rationale, feasibility, and potential effect for the prevention of childhood allergic diseases and explores possible strategies for enhancing exposure to beneficial microbes.

The evolution of the hygiene hypothesis: the role of early-life exposures to viruses and microbes and their relationship to asthma and allergic diseases. Curr Opin Allergy Clin Immunol. 2014;14:390-396. [PMID: 25102107 DOI: 10.1097/aci.0000000000000101]

PURPOSE OF REVIEW

Understanding the mechanisms involved in the development of asthma and allergic diseases is expanding, due in part to sequencing advances that have led to the identification of new viral strains such as human rhinovirus strain C (HRV-C) and the human microbiome project.

RECENT FINDINGS

Recent studies have identified new ways in which viral and microbial exposures in early life interact with host genetic background/variants to modify the risk for developing asthma and allergic diseases. Recent research suggests that HRV-C is the main pathogenic agent associated with infant wheeze, hospitalizations and likely the subsequent development of asthma. Pulmonary He MRI suggests that HRV infection in early childhood and subsequent immune responses initiate airway remodeling. Numerous studies of the microbiome indicate that intestinal and airway microbiome diversity and composition contribute to the cause of asthma and allergic diseases.

SUMMARY

Susceptibility to asthma and allergic diseases is complex and involves genetic variants and environmental exposures (bacteria, viruses, smoking, and pet ownership), alteration of our microbiome and potentially large-scale manipulation of the environment over the past century.

TLR4 enhances histamine-mediated pruritus by potentiating TRPV1 activity

Background

Recent studies have indicated that Toll-like receptor 4 (TLR4), a pathogen-recognition receptor that triggers inflammatory signals in innate immune cells, is also expressed on sensory neurons, implicating its putative role in sensory signal transmission. However, the possible function of sensory neuron TLR4 has not yet been formally addressed. In this regard, we investigated the role of TLR4 in itch signal transmission.

Results

TLR4 was expressed on a subpopulation of dorsal root ganglia (DRG) sensory neurons that express TRPV1. In TLR4-knockout mice, histamine-induced itch responses were compromised while TLR4 activation by LPS did not directly elicit an itch response. Histamine-induced intracellular calcium signals and inward currents were comparably reduced in TLR4-deficient sensory neurons. Reduced histamine sensitivity in the TLR4-deficient neurons was accompanied by a decrease in TRPV1 activity. Heterologous expression experiments in HEK293T cells indicated that TLR4 expression enhanced capsaicin-induced intracellular calcium signals and inward currents.

Conclusions

Our data show that TLR4 on sensory neurons enhances histamine-induced itch signal transduction by potentiating TRPV1 activity. The results suggest that TLR4 could be a novel target for the treatment of enhanced itch sensation.

Environmental changes, microbiota, and allergic diseases

During the last few decades, the prevalence of allergic disease has increased dramatically. The development of allergic diseases has been attributed to complex interactions between environmental factors and genetic factors. Of the many possible environmental factors, most research has focused on the most commonly encountered environmental factors, such as air pollution and environmental microbiota in combination with climate change. There is increasing evidence that such environmental factors play a critical role in the regulation of the immune response that is associated with allergic diseases, especially in genetically susceptible individuals. This review deals with not only these environmental factors and genetic factors but also their interactions in the development of allergic diseases. It will also emphasize the need for early interventions that can prevent the development of allergic diseases in susceptible populations and how these interventions can be identified.

Effects of early-life exposure to allergens and bacteria on recurrent wheeze and atopy in urban children

BACKGROUND

Wheezing illnesses cause major morbidity in infants and are frequent precursors to asthma.

OBJECTIVE

We sought to examine environmental factors associated with recurrent wheezing in inner-city environments.

METHODS

The Urban Environment and Childhood Asthma study examined a birth cohort at high risk for asthma (n = 560) in Baltimore, Boston, New York, and St Louis. Environmental assessments included allergen exposure and, in a nested case-control study of 104 children, the bacterial content of house dust collected in the first year of life. Associations were determined among environmental factors, aeroallergen sensitization, and recurrent wheezing at age 3 years.

RESULTS

Cumulative allergen exposure over the first 3 years was associated with allergic sensitization, and sensitization at age 3 years was related to recurrent wheeze. In contrast, first-year exposure to cockroach, mouse, and cat allergens was negatively associated with recurrent wheeze (odds ratio, 0.60, 0.65, and 0.75, respectively; P ≤ .01). Differences in house dust bacterial content in the first year, especially reduced exposure to specific Firmicutes and Bacteriodetes, was associated with atopy and atopic wheeze. Exposure to high levels of both allergens and this subset of bacteria in the first year of life was most common among children without atopy or wheeze.

CONCLUSIONS

In inner-city environments children with the highest exposure to specific allergens and bacteria during their first year were least likely to have recurrent wheeze and allergic sensitization. These findings suggest that concomitant exposure to high levels of certain allergens and bacteria in early life might be beneficial and suggest new preventive strategies for wheezing and allergic diseases.

Introduction to genetics and genomics in asthma: genetics of asthma

While asthma is a heterogeneous disease, a strong genetic basis has been firmly established. Rather than being a single disease entity, asthma consists of related, overlapping syndromes [Barnes (Proc Am Thor Soc 8:143-148, 2011)] including three general domains: variable airway obstruction, airway hyper-responsiveness, and airway inflammation with a considerable proportion, but not all, of asthma being IgE-mediated further adding to its heterogeneity. This chapter reviews the approaches to the elucidation of genetics of asthma from the early evidence of familial clustering to the current state of knowledge with genome-wide approaches. The conclusion is that research efforts have led to a tremendous repository of genetic determinants of asthma, most of which fall into the above phenotypic domains of the syndrome. We now look to future integrative approaches of genetics, genomics (Chap. 10), and epigenetics (Chap. 11) to better understand the causal mechanism through which, these genetic loci act in manifesting asthma.

New insights into the epidemiology of childhood atopic dermatitis

There is a growing desire to explain the worldwide rise in the prevalence of atopic dermatitis (AD). Trend data on the burden of AD suggest that the picture in the developing world may soon resemble that of wealthier nations, where AD affects over 20% of children. This, combined with significant variations in prevalence within countries, emphasizes the importance of environmental factors. Many hypotheses have been explored, from the modulation of immune priming by hygiene, gut microbiota diversity, and exposure to endotoxins through farm animals to the effects of pollution, climate, and diet. The discovery of the filaggrin skin barrier gene and its importance in AD development and severity has brought the focus on gene-environment interactions and the identification of environmental factors that impact on skin barrier function. This article reviews our current understanding of the epidemiology of AD, with an emphasis on the findings reported in the international literature over the last 5 years.

A cross-sectional analysis of pet-specific immunoglobulin E sensitization and allergic symptomatology and household pet keeping in a birth cohort population

It is unknown whether family members with detectable specific immunoglobulin E (sIgE) and/or allergic symptoms to pets are more or less likely to reside in a household with pets. We cross-sectionally investigated potential relationships between family members' allergic sensitization and symptoms to dogs and cats and current household pet-keeping practices, using birth cohort data. Blood samples taken from children enrolled in a birth cohort and their biological mothers and fathers, when the children were aged 18 years, were assessed for sIgE to dog and cat allergens. Interviews assessed subjects' self-reported pet exposure symptoms, current household pet-keeping practices, and socioeconomic characteristics. Overall, household dog or cat keeping was not associated with sIgE to these animals and/or self-reported allergic symptoms in the presence of these animals, even after controlling for factors such as education and household income. In subgroup analyses, current household dog keeping among dog-symptomatic teens (n = 40) was significantly lower than among teens who were not dog symptomatic (n = 289), at 48.8 and 61.1%, respectively (p = 0.036). Current household cat keeping was significantly lower among cat-symptomatic mothers (n = 27) compared with mothers who were not cat symptomatic (n = 120), at 24.3 and 37.0%, respectively (p = 0.015). However, when considering those who were both sensitized and reported symptoms, only the mother and cat-keeping associations persisted (p = 0.049). When cat-sensitized mothers report allergic symptoms to cats, these pets may be less likely to be kept in homes. Elevated dog and cat allergen sIgE does not appear to be associated with the keeping of these pets.

Is there an association between microbial exposure and food allergy? A systematic review

The environmental factors driving the recent increase in the prevalence of food allergy (FA) are unclear. Since associations have been demonstrated between microbial exposure and the likelihood of eczema and respiratory allergies, we reviewed the evidence for FA. Medline was systematically searched from inception to the end of July 2012 for studies investigating links between FA and environmental exposures, likely to influence microbial exposure, such as Caesarean delivery, family size, day-care attendance, childhood infections, immunizations and antibiotic use. We selected studies reporting food challenge data, reported doctor-diagnosed (RDD) FA and food sensitization. Methodological differences and study heterogeneity precluded meta-analysis. A total of 46 studies were identified, of which 28 (60.9%) were prospective and 13 (28.3%) used food challenges to diagnose FA. Caesarean delivery was investigated in 13 studies, of which three infant cohorts demonstrated an increase in challenge-proven FA (one cohort) and food sensitization (two cohorts), and one cross-sectional study reported increased RDDFA. Four studies investigated the effect of having siblings, with one infant cohort demonstrating less challenge-proven FA and a cross-sectional study showing a decrease in RDDFA. Attending childcare before 6 months was associated with less challenge-proven FA in one cohort. A cross-sectional survey identified an inverse relationship between hepatitis A serology and peanut sensitization. One of eleven trials investigating probiotics demonstrated a quicker acquisition of milk tolerance amongst allergic infants. Factors influencing microbial exposure may be partly responsible for rising FA burden, but further prospective studies using double-blind placebo controlled food challenges as an outcome are required.

Pet exposure and risk of atopic dermatitis at the pediatric age: a meta-analysis of birth cohort studies

BACKGROUND

Findings on pet exposure and the risk of atopic dermatitis (AD) in children are inconsistent.

OBJECTIVE

With the aim to summarize the results of exposure to different pets on AD, we undertook a meta-analysis of epidemiologic studies on this issue.

METHODS

In August 2012, we conducted a systematic literature search in Medline and Embase. We included analytic studies considering exposure to dogs, cats, other pets, or pets overall during pregnancy, infancy, and/or childhood, with AD assessment performed during infancy or childhood. We calculated summary relative risks and 95% CIs using both fixed- and random-effects models. We computed summary estimates across selected subgroups.

RESULTS

Twenty-six publications from 21 birth cohort studies were used in the meta-analyses. The pooled relative risks of AD for exposure versus no exposure were 0.72 (95% CI, 0.61-0.85; I(2) = 46%; results based on 15 studies) for exposure to dogs, 0.94 (95% CI, 0.76-1.16; I(2) = 54%; results based on 13 studies) for exposure to cats, and 0.75 (95% CI, 0.67-0.85; I(2) = 54%; results based on 11 studies) for exposure to pets overall. No heterogeneity emerged across the subgroups examined, except for geographic area.

CONCLUSION

This meta-analysis reported a favorable effect of exposure to dogs and pets on the risk of AD in infants or children, whereas no association emerged with exposure to cats.

Factors associated with degree of atopy in Latino children in a nationwide pediatric sample: the Genes-environments and Admixture in Latino Asthmatics (GALA II) study

BACKGROUND

Atopy varies by ethnicity, even within Latino groups. This variation might be due to environmental, sociocultural, or genetic factors.

OBJECTIVE

We sought to examine risk factors for atopy within a nationwide study of US Latino children with and without asthma.

METHODS

Aeroallergen skin test responses were analyzed in 1830 US Latino subjects. Key determinants of atopy included country/region of origin, generation in the United States, acculturation, genetic ancestry, and site to which subjects migrated. Serial multivariate zero-inflated negative binomial regressions stratified by asthma status examined the association of each key determinant variable with the number of positive skin test responses. In addition, the independent effect of each key variable was determined by including all key variables in the final models.

RESULTS

In baseline analyses African ancestry was associated with 3 times (95% CI, 1.62-5.57) as many positive skin test responses in asthmatic participants and 3.26 times (95% CI, 1.02-10.39) as many positive skin test responses in control participants. Generation and recruitment site were also associated with atopy in crude models. In final models adjusted for key variables, asthmatic patients of Puerto Rican (exp[β] [95% CI], 1.31 [1.02-1.69]) and mixed (exp[β] [95% CI], 1.27 [1.03-1.56]) ethnicity had a greater probability of positive skin test responses compared with Mexican asthmatic patients. Ancestry associations were abrogated by recruitment site but not region of origin.

CONCLUSIONS

Puerto Rican ethnicity and mixed origin were associated with degree of atopy within US Latino children with asthma. African ancestry was not associated with degree of atopy after adjusting for recruitment site. Local environment variation, represented by site, was associated with degree of sensitization.

Controversial role of pets in the development of atopy in children

BACKGROUND

Exposure to environmental allergens originating from different sources has been implicated in the sensitization to the respective allergens and development of atopic diseases. Keeping domestic animals is associated with exposure to relevant allergens but there are controversial data whether this exposure promotes or protects from the development of atopy.

DATA SOURCES

We herein reviewed the literature regarding the available data for the exposure to pets (cats and/or dogs) and the development of atopy. For this purpose, we searched the PubMed database.

RESULTS

This review attempts to answer the following questions that arise from the daily practice and the relevant studies, which are: a) is pet keeping associated with sensitization? b) is there an association between keeping pets and the development of asthma, allergic rhinitis and eczema, and, c) what is the underlying mechanism of any possible protective association? Despite the fact that several studies and meta-analyses have been conducted to explore the role of pets in the development of atopy, there are still conflicting pieces of evidence. It seems that there are different effects depending on the type of pets, the time and duration of exposure, and the genetic background of the individual.

CONCLUSION

Further appropriately designed birth cohort studies are needed to explore whether exposure to relevant allergens from pets promotes or protects from the development of atopy.

An approach to preschool wheezing: to label as asthma?

Asthma is considered a chronic disease, but not all preschool wheezing is asthma since most will eventually grow out of their symptoms. Although still a matter of debate, preschool wheezing can be classified in 2 major groups: virus-induced wheezing and multitrigger wheezing, having a different prognosis and a different treatment approach. Virus-induced wheezing is the most common phenotype of preschool wheezing and is usually associated with a good prognosis. Treatment should be conservative, but if preventive treatment is required, leukotriene-receptor antagonists might be the first choice treatment. Multitrigger wheezing is associated with an allergic disposition and has a higher risk of persistent symptoms. Inhaled corticosteroids may give short-term reduction in exacerbations, but the beneficial effect of long-term use of inhaled corticosteroids and other anti-inflammatory agents have not yet been established. This review aims to give an opinion on preschool wheezing, and its association with asthma.