Andrew H. Liu

Bacterial DNA in house and farm barn dust

BACKGROUNDnEarly in life, natural exposure to microbial components (eg, endotoxin) may mitigate allergy and asthma development in childhood. Bacterial DNA is a potent stimulus for the innate immune system; its immune stimulatory potential in dust is unknown.nnnOBJECTIVESnWe sought to quantify bacterial DNA and endotoxin content in dust from urban homes, rural homes, farm homes, and farm barns and to determine if dust DNA is immune-stimulatory.nnnMETHODSnTotal DNA, bacterial DNA, and endotoxin were measured in 32 dust samples. To measure bacterial DNA content, a quantitative polymerase chain reaction assay specific for bacterial ribosomal DNA was developed. Peripheral blood mononuclear cells from 5 adults were stimulated with endotoxin-free dust DNA with/without lipopolysaccharide (LPS) from selected dust samples. IL-12p40, IL-10, and tumor necrosis factor-alpha were measured in cell supernatants by enzyme-linked immunosorbent assay.nnnRESULTSnBacterial DNA in dust correlated with endotoxin (r = 0.56, P <.001) and total DNA content (r = 0.51, P =.003). The highest bacterial DNA levels were measured in farm barns (mean, 22.1 microg/g dust; range, 1.3 to 56.2), followed by rural homes (6.3 microg/g; 0.2 to 20), farm homes (2.2 microg/g; 0.1 to 9.1), and urban homes (0.6 microg/g; 0.1 to 1.2). Farm barn DNA significantly potentiated (P < or =.05) LPS-induced IL-10 and IL-12 p40 but not tumor necrosis factor-alpha release (13-fold, 3-fold, and 1.5-fold increases, respectively). DNA from 6 urban homes did not demonstrate this LPS-potentiating effect.nnnCONCLUSIONSnEndotoxin is a marker for bacterial DNA, which is also higher in locales of lower asthma and allergy prevalence. DNA from farm barn dust augments the immune modulatory effects of endotoxin and may combine with exposure to other such naturally occurring microbial components to mitigate allergy and asthma development.

Something old, something new: Indoor endotoxin, allergens and asthma

Endotoxin and allergen exposure have been explored in the context of asthma for more than a century. Building upon a pyramid of knowledge are recent observations that provide new insights to the effect of these exposures on the development of asthma. Some of these studies challenge some previously held concepts of the role of these exposures in asthma inception. Indoor allergens are well established as the basis of inflammation in sensitised asthmatics, contributing to disease severity. Then does greater exposure to indoor allergens cause allergen sensitisation and asthma as well? While risk of sensitisation to house dust mites generally increases with higher levels of exposure, this does not seem to hold for cats, where higher levels of cat allergen exposure are associated with less sensitisation. Indeed, several recent studies suggest that early childhood exposure to animals, as indoor pets or in farming stables, are associated with a lower prevalence of asthma, hay fever, and inhalant allergen sensitisation. Endotoxin in asthma provides a similar paradox. Endotoxin is a potent immune-stimulatory component of the bacterial cell wall of all gram-negative bacteria. As such, endotoxin is ubiquitous in our environment. Endotoxin exposure has been well demonstrated to underlie Monday Asthma or byssinosis in cotton workers, and has since emerged as a frequent cause of asthma-like symptoms in a wide range of occupational settings. Asthmatics are particularly sensitive to inhaled endotoxin, and inhalation induces both immediate and sustained airflow obstruction. The paradox of endotoxin exposure is that higher levels of exposure in early life might mitigate the development of allergy and persistent asthma. With endotoxin exposure being significantly higher in homes with animals and in farming households, where allergy and asthma are less likely to develop, endotoxin and other microbial exposures in early life may keep allergen sensitisation and asthma from developing by promoting Th1-type immune development. These observations, consistent with the Hygiene Hypothesis of allergy and asthma, are an encouraging glimpse of the potential for early immune modulatory approaches to asthma therapy and prevention.

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.

Effect of animal contact and microbial exposures on the prevalence of atopy and asthma in urban vs rural children in India

BACKGROUNDnEnvironmental factors, including microbial exposures and close animal contact, are implicated in the lower prevalence of asthma and allergy in rural vs urban children.nnnOBJECTIVESnTo determine (1) the prevalence of asthma, rhinitis, eczema, and atopic sensitization in rural and urban children in India; (2) differences in microbial and animal exposures in these locales; and (3) whether differences in environmental exposures account for the different rates of asthma and atopy in these locales.nnnMETHODSnOne child from each of 50 urban (Mysore) and 50 rural (Vinobha) households in southern India was randomly selected for data analysis. Allergy, asthma, health, environment, and lifestyle information was obtained using a questionnaire and household inspections. Atopy was determined via skin prick testing for common allergens. Endotoxin content was measured in house dust samples.nnnRESULTSnChildren from rural vs urban areas had lower prevalences of self-reported asthma (8% vs 30%; P = .005), rhinitis (22% vs 42%; P = .03), and atopic sensitization (36% vs 58%; P = .03). Higher median dust endotoxin loads were found in rural vs urban households (6.50 x 10(4) EU/m2 vs 1.27 x 10(4) EU/m2; P < .001). In multivariate analysis, close indoor animal contact (adjusted odds ratio [OR] 0.2; 90% confidence interval [CI], 0.05-0.9), outdoor animal contact (OR, 0.3; 90% CI, 0.1-0.8), and exclusive breastfeeding for at least 6 months (OR, 0.2; 90% CI, 0.1-0.5) were associated with lower atopic sensitization; mud flooring was associated with lower self-reported wheezing (OR, 0.1; 90% CI, 0.02-1.0).nnnCONCLUSIONnChildren in India who live with close animal contact and mud flooring and who were exclusively breastfed in infancy are less likely to develop asthma, rhinitis, and atopic sensitization.

Immune stimulatory DNA in farm barn dust

S. R. Roy 12, A. M. Schlitz t, Y. Shen l, A. H. Liul.2; IPediatric Allergy & Clinical Immunology, National Jewish Medical & Research Center, Denver, CO, 2University of Colorado Health Sciences Center, Denver, CO. RATIONALE: Naturally occurring microbial exposures, such as endotoxin, may mitigate allergy and asthma development in childhood. Bacterial DNA is similarly a potent stimulus for the immune system, but the immune stimulatory potential of DNA in dust has not been reported. We investigated the immune stimulatory potential of DNA extracted from farm barn dust. METHODS: DNA was extracted from dust from two farm barns and one urban home using commercial DNA extraction kits and endotoxin removal columns. PBMC from 3 adult subjects were stimulated x 24 hours with endotoxin-free dust DNA_+LPS. lL-12p40, IL-10 and TNF-c~ were measured in PBMC supernatants. RESULTS: More DNA was extracted from farm barn dust (80 lag/g and 106 lttg/g dust) compared to the urban home (27 lag/g). 3 lag/ml of farm barn or urban home dust DNA alone did not stimulate cytokine release. LPS alone (300 pg/ml) stimulated PBMCs to release IL-10 (15 pg/ml), ILl2 (94 pg/ml) and TNF-ot (197 pg/ml). When combined, 3 lag/ml of farm barn DNA and LPS showed potentiation of IL-10 (363 pg/ml; 24-fold increase) and IL-12p40 (272 pg/ml; 3-fold increase) release (p<0.05), but not of TNF-ot (312 pg/ml; 1.5-fold increase). IL-10 and IL-12 release stimulated by 10 lag/ml of farm barn DNA plus 300 pg/ml of LPS approached maximal cytokine release induced by 10 ng/ml of LPS alone. CONCLUSIONS: DNA from farm barn dust augments the immune modulatory effects of endotoxin, and may combine with other naturally occurring microbial exposures to mitigate allergy and asthma development. Funding: Supported by AAAAI (ERT), National Jewish institutional fund 64 A 3-mm Wheal Doesnt Discriminate Between Cat Allergic and Non-Allergic Patients

Asthma phenotypes at age 4: Follow-up of disadvantaged wheezing infants

5 5 Asthma Phenotypes at Age 4: Follow-up of Disadvantaged Wheezing Infants M. D. Klinnert l, M. R. Price 2, A. H. Liu I, C. A. Dennisl; ]Pediatrics, National Jewish Medical and Research Center, Denver, CO, 2pediatrics, National Jewish Medical and Research Center, Denver, CO. RATIONALE: Despite epidemiological evidence indicating an increase in asthma morbidity among low income minority children less than age 5 years, little is known regarding the natural history and phenotypic distribution of asthma in this group. METHODS: The Childhood Asthma Prevention Study recruited lowincome families of children age 9-24 months with >3 wheezing episodes. Home and laboratory assessments were conducted, and half of the families were randomized to environmental support lasting one year. At age 4 years the children were evaluated using prick skin testing, pulmonary functions, and medical record review, and caregiver symptom reports (modified ATS-B questionnaire assessing 5 symptoms) for the previous 12 months. We report here illness patterns for children (n=124) with complete 4-year evaluations, regardless of intervention assignment. RESULTS: Caregivers reported wheezing between 3 and 4 years for 85% of children. 58% were positive for 3/5 ATS-B questions, and 38% for 4/5 questions. 34% of the children had >1 positive skin test (atopic). Children meeting ATS-B criteria for asthma were no more likely to be atopic than those not (3/5 p=0.32; 4/5 p=0.60). Among the children meeting either criteria level, atopic children were significantly more likely to have had a corticosteroid burst (p<0.04) or hospitalization (p<0.005). However, atopic and nonatopic children were equally likely to utilize the ED for wheezing illness. CONCLUSIONS: Most disadvantaged children with frequent wheezing as infants showed significant morbidity at age 4 years, with continued wheezing and frequent ED visits. Those with both wheezing and atopy showed a pattern of more severe illness. Funding: N1H/NIAID