Poultry exposure and environmental protection against asthma in rural children

Advancing Understanding of Childhood Asthma: Lessons Learned from Birth Cohort Studies

Asthma and allergies are some of the most common chronic disorders affecting children, the prevalence of which has been increasing in countries and regions undergoing rapid development like China. To curb the rising tide of allergies and safeguard the health of future generations, it is of critical importance to understand how asthma inception is influenced by factors acting at different life stages. Birth cohorts represent a powerful tool to investigate the temporal sequence of exposures along the natural course of asthma. We examined recent evidence on birth cohort studies of asthma and allergic diseases and evaluated their strengths and weaknesses. Essential elements for a successful birth cohort are proposed to further elucidate asthma etiology and pathogenies. Initiating new cohorts in understudied populations with the application of advanced analytical approaches will be needed. Moreover, fostering collaborative networks using standardized methodologies should be prioritized to enable integration of findings across diverse cohorts. There remains an urgent and unmet need to further translate the seminal findings from asthma birth cohort studies into targeted primary prevention strategies to eradicate the disease.

Immune modulation by rural exposures and allergy protection

BACKGROUND

Growing up on traditional farms protects children from the development of asthma and allergies. However, we have identified distinct asthma-protective factors, such as poultry exposure. This study aims to examine the biological effect of rural exposure in China.

METHODS

We recruited 67 rural children (7.4 ± 0.9 years) and 79 urban children (6.8 ± 0.6 years). Depending on the personal history of exposure to domestic poultry (DP), rural children were further divided into those with DP exposure (DP+ , n = 30) and those without (DP- , n = 37). Blood samples were collected to assess differential cell counts and expression of immune-related genes. Dust samples were collected from poultry stables inside rural households. In vivo activities of nasal administration of DP dust extracts were tested in an ovalbumin-induced asthma model.

RESULTS

There was a stepwise increase in the percentage of eosinophils (%) from rural DP+ children (median = 1.65, IQR = [1.28, 3.75]) to rural DP- children (3.40, [1.70, 6.50]; DP+ vs. DP- , p = .087) and to the highest of their urban counterparts (4.00, [2.00, 7.25]; urban vs. DP+ , p = .017). Similarly, rural children exhibited reduced mRNA expression of immune markers, both at baseline and following lipopolysaccharide (LPS) stimulation. Whereas LPS stimulation induced increased secretion of Th1 and proinflammatory cytokines in rural DP+ children compared to rural DP- children and urban children. Bronchoalveolar lavage of mice with intranasal instillation of dust extracts from DP household showed a significant decrease in eosinophils as compared to those of control mice (p < .05). Furthermore, DP dust strongly inhibited gene expression of Th2 signature cytokines and induced IL-17 expression in the murine asthma model.

CONCLUSIONS

Immune responses of rural children were dampened compared to urban children and those exposed to DP had further downregulated immune responsiveness. DP dust extracts ameliorated Th2-driven allergic airway inflammation in mice. Determining active protective components in the rural environment may provide directions for the development of primary prevention of asthma.

From preschool wheezing to asthma: Environmental determinants

Wheezing is common among preschool children, representing a group of highly heterogeneous conditions with varying natural history. Several phenotypes of wheezing have been proposed to facilitate the identification of young children who are at risk of subsequent development of asthma. Epidemiological and immunological studies across different populations have revealed the key role of environmental factors in influencing the progression from preschool wheezing to childhood asthma. Significant risk factors include severe respiratory infections, allergic sensitization, and exposure to tobacco smoke. In contrast, a farming/rural environment has been linked to asthma protection in both human and animal studies. Early and intense exposures to microorganisms and microbial metabolites have been demonstrated to alter host immune responses to allergens and viruses, thereby driving the trajectory away from wheezing illness and asthma. Ongoing clinical trials of candidate microbes and microbial products have shown promise in shaping the immune function to reduce episodes of viral-induced wheezing. Moreover, restoring immune training may be especially important for young children who had reduced microbial exposure due to pandemic restrictions. A comprehensive understanding of the role of modifiable environmental factors will pave the way for developing targeted prevention strategies for preschool wheezing and asthma.

Effect of altered human exposome on the skin and mucosal epithelial barrier integrity

Pollution in the world and exposure of humans and nature to toxic substances is continuously worsening at a rapid pace. In the last 60 years, human and domestic animal health has been challenged by continuous exposure to toxic substances and pollutants because of uncontrolled growth, modernization, and industrialization. More than 350,000 new chemicals have been introduced to our lives, mostly without any reasonable control of their health effects and toxicity. A plethora of studies show exposure to these harmful substances during this period with their implications on the skin and mucosal epithelial barrier and increasing prevalence of allergic and autoimmune diseases in the context of the "epithelial barrier hypothesis". Exposure to these substances causes an epithelial injury with peri-epithelial inflammation, microbial dysbiosis and bacterial translocation to sub-epithelial areas, and immune response to dysbiotic bacteria. Here, we provide scientific evidence on the altered human exposome and its impact on epithelial barriers.

Global, regional, and national incidence of six major immune-mediated inflammatory diseases: findings from the global burden of disease study 2019

Background

The causes for immune-mediated inflammatory diseases (IMIDs) are diverse and the incidence trends of IMIDs from specific causes are rarely studied. The study aims to investigate the pattern and trend of IMIDs from 1990 to 2019.

Methods

We collected detailed information on six major causes of IMIDs, including asthma, inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis, psoriasis, and atopic dermatitis, between 1990 and 2019, derived from the Global Burden of Disease study in 2019. The average annual percent change (AAPC) in number of incidents and age standardized incidence rate (ASR) on IMIDs, by sex, age, region, and causes, were calculated to quantify the temporal trends.

Findings

In 2019, rheumatoid arthritis, atopic dermatitis, asthma, multiple sclerosis, psoriasis, inflammatory bowel disease accounted 1.59%, 36.17%, 54.71%, 0.09%, 6.84%, 0.60% of overall new IMIDs cases, respectively. The ASR of IMIDs showed substantial regional and global variation with the highest in High SDI region, High-income North America, and United States of America. Throughout human lifespan, the age distribution of incident cases from six IMIDs was quite different. Globally, incident cases of IMIDs increased with an AAPC of 0.68 and the ASR decreased with an AAPC of -0.34 from 1990 to 2019. The incident cases increased across six IMIDs, the ASR of rheumatoid arthritis increased (0.21, 95% CI 0.18, 0.25), while the ASR of asthma (AAPC = -0.41), inflammatory bowel disease (AAPC = -0.72), multiple sclerosis (AAPC = -0.26), psoriasis (AAPC = -0.77), and atopic dermatitis (AAPC = -0.15) decreased. The ASR of overall and six individual IMID increased with SDI at regional and global level. Countries with higher ASR in 1990 experienced a more rapid decrease in ASR.

Interpretation

The incidence patterns of IMIDs varied considerably across the world. Innovative prevention and integrative management strategy are urgently needed to mitigate the increasing ASR of rheumatoid arthritis and upsurging new cases of other five IMIDs, respectively.

Funding

The Global Burden of Disease Study is funded by the Bill and Melinda Gates Foundation. The project funded by Scientific Research Fund of Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital (2022QN38).

Asthma-protective agents in dust from traditional farm environments

BACKGROUND

Growing up on traditional European or US Amish dairy farms in close contact with cows and hay protects children against asthma, and airway administration of extracts from dust collected from cowsheds of those farms prevents allergic asthma in mice.

OBJECTIVES

This study sought to begin identifying farm-derived asthma-protective agents.

METHODS

Our work unfolded along 2 unbiased and independent but complementary discovery paths. Dust extracts (DEs) from protective and nonprotective farms (European and Amish cowsheds vs European sheep sheds) were analyzed by comparative nuclear magnetic resonance profiling and differential proteomics. Bioactivity-guided size fractionation focused on protective Amish cowshed DEs. Multiple in vitro and in vivo functional assays were used in both paths. Some of the proteins thus identified were characterized by in-solution and in-gel sodium dodecyl sulfate-polyacrylamide gel electrophoresis enzymatic digestion/peptide mapping followed by liquid chromatography/mass spectrometry. The cargo carried by these proteins was analyzed by untargeted liquid chromatography-high-resolution mass spectrometry.

RESULTS

Twelve carrier proteins of animal and plant origin, including the bovine lipocalins Bos d 2 and odorant binding protein, were enriched in DEs from protective European cowsheds. A potent asthma-protective fraction of Amish cowshed DEs (≈0.5% of the total carbon content of unfractionated extracts) contained 7 animal and plant proteins, including Bos d 2 and odorant binding protein loaded with fatty acid metabolites from plants, bacteria, and fungi.

CONCLUSIONS

Animals and plants from traditional farms produce proteins that transport hydrophobic microbial and plant metabolites. When delivered to mucosal surfaces, these agents might regulate airway responses.

From Amish farm dust to bacterial lysates: The long and winding road to protection from allergic disease

Allergic diseases typically begin in early life and can impose a heavy burden on children and their families. Effective preventive measures are currently unavailable but may be ushered in by studies on the "farm effect", the strong protection from asthma and allergy found in children born and raised on traditional farms. Two decades of epidemiologic and immunologic research have demonstrated that this protection is provided by early and intense exposure to farm-associated microbes that target primarily innate immune pathways. Farm exposure also promotes timely maturation of the gut microbiome, which mediates a proportion of the protection conferred by the farm effect. Current research seeks to identify allergy-protective compounds from traditional farm environments, but standardization and regulation of such substances will likely prove challenging. On the other hand, studies in mouse models show that administration of standardized, pharmacological-grade lysates of human airway bacteria abrogates allergic lung inflammation by acting on multiple innate immune targets, including the airway epithelium/IL-33/ILC2 axis and dendritic cells whose Myd88/Trif-dependent tolerogenic reprogramming is sufficient for asthma protection in adoptive transfer models. To the extent that these bacterial lysates mimic the protective effects of natural exposure to microbe-rich environments, these agents might provide an effective tool for prevention of allergic disease.

What Have Mechanistic Studies Taught Us About Childhood Asthma?

Childhood asthma is a chronic heterogeneous syndrome consisting of different disease entities or phenotypes. The immunologic and cellular processes that occur during asthma development are still not fully understood but represent distinct endotypes. Mechanistic studies have examined the role of gene expression, protein levels, and cell types in early life development and the manifestation of asthma, many under the influence of environmental stimuli, which can be both protective and risk factors for asthma. Genetic variants can regulate gene expression, controlled partly by different epigenetic mechanisms. In addition, environmental factors, such as living space, nutrition, and smoking, can contribute to these mechanisms. All of these factors produce modifications in gene expression that can alter the development and function of immune and epithelial cells and subsequently different trajectories of childhood asthma. These early changes in a partially immature immune system can have dramatic effects (e.g., causing dysregulation), which in turn contribute to different disease endotypes and may help to explain differential responsiveness to asthma treatment. In this review, we summarize published studies that have aimed to uncover distinct mechanisms in childhood asthma, considering genetics, epigenetics, and environment. Moreover, a discussion of new, powerful tools for single-cell immunologic assays for phenotypic and functional analysis is included, which promise new mechanistic insights into childhood asthma development and therapeutic and preventive strategies.