Center for Childhood Asthma in the Urban Environment

Johns Hopkins Bloomberg School of Public Health  

Center for Childhood Asthma in the Urban Environment
Patrick Breysse, Ph.D.
pbreysse@jhsph.edu

Project Description

The long-term goals of this Center are to examine how exposures to environmental pollutants and allergens may relate to airway inflammation and respiratory morbidity in children with asthma living in the inner city of Baltimore, and to search for new ways to reduce asthma morbidity by reducing exposure to these agents. To accomplish these goals the Center includes both basic and applied research programs in combination with a community-based intervention research project. The first project is a community-based epidemiologic study of 400 children 6-12 and their homes to identify relevant airborne exposures and to examine genetic determinants of asthma morbidity resulting from these exposures. The second project is community-based participatory research project that is a randomized controlled clinical trial in 120 children of the effectiveness of behavioral methods to reducing pollutant and allergen exposures and their adverse health effects. The third project examines the mechanisms by which particulate matter may exacerbate an allergen-driven response in of the airways. The fourth project examines the effects of environmental particulates on the in vitro maturation of peripheral blood monocytes to dendritic cells. These projects are supported by core facilities for data management and exposure assessment. Another core facility increases the Center's existing community outreach and translational activities. An Administrative Core supports research and general meetings to integrate the interests and activities of the Center. A community advisory committee contributes to both the environmental epidemiology project and the community-based intervention research project planning, and meets periodically with Center researchers to discuss the Center's findings and progress. A seven-member External Advisory Committee has been recruited. Information gained by this coordinated interdisciplinary team allows rational plans to be made for future studies to examine susceptible children and to plan even more effective interventions in future studies with collaborating families in the East Baltimore community.

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Project Highlights

Mouse allergen exposure is strongly associated with inner-city asthma morbidity
Center investigators have published a series of papers documenting the importance of mouse allergen as a source of morbidity for inner-city asthmatic children.  Some findings are described in more detail below.

Although mouse allergen exposure is common in inner-city homes, little is known about the relationships between exposure and humoral immune responses to mouse allergen in this population.  Center investigators examined the relationships between mouse allergen exposure and allergen-specific IgE and IgG responses in inner-city children with asthma. Inner-city children with asthma underwent skin testing and venipuncture for determination of mouse allergen-specific IgE and IgG levels. Settled dust samples were collected from their homes for allergen analysis.  The study population (n = 112) was predominantly African-American (92%) with a mean age of 4.4 years. The prevalence rate of mouse sensitization was 25%, and did not consistently increase with increasing Mus m 1 levels.  Instead, the prevalence rate was lowest among those exposed to < 2 ug/g, increased among those exposed to 2-7.9, and 8-29.9 ug/g, and then decreased among participants exposed to > 29.9 ug/g (14%, 20%, 40%, and 28%, respectively). Similarly, the prevalence rates of mouse allergen-specific IgG and IgG4 did not increase across increasing exposure categories.  Mouse allergen-specific IgG and IgG4 were strongly associated with IgE-sensitization (OR [95% CI]: 82.8 [20.5-334.4] and 50.4 [14.0-181.7], respectively).  Center investigators therefore concluded that high level exposure to mouse allergen in children may be associated with attenuated humoral responses of all isotypes, rather than selective attenuation of IgE.  As a result, protection against allergic sensitization by high dose allergen exposure may not be mediated by preferential production of IgG over IgE.  [Matsui EC, Eggleston PA, Breysse PN, Rand CS, Diette GB. Mouse Allergen-specific Antibody Responses in Inner-city Children with Asthma.  J Allergy Clin Immunol  In Press.]

Indoor PM from inner-city Baltimore homes is significantly associated with asthma morbidity
Center investigators examined the association between indoor PM exposure and health outcomes in asthmatic children.  One hundred fifty asthmatic children enrolled in a cohort study were followed with repeated measures of indoor PM monitoring and health outcome assessment at baseline, 3, and 6 months.  Elevated indoor PM levels were significantly associated with increased respiratory symptoms and more frequent rescue medication use in our longitudinal analysis.  In longitudinal analysis, for every 10 µg/m³ increase in PM₁₀, there were more days with asthma symptoms (cough, wheeze, chest tightness) in the previous 2 weeks [IRR 1.03 (95% CI, 1.0-1.05)].  Likewise, for every 10 µg/m³ increase in PM₁₀, there were more nights with awakening with asthma symptoms [IRR 1.03 (95% CI, 1.0-1.06)] and more days with exercise symptoms [IRR 1.03 (95% CI, 1.0-1.06)].  For every 10 µg/m³ increase in PM₁₀, there was 7 % [IRR 1.07 (95% CI, 1.03-1.11)] increase in wheezing severe enough to limit speech and a 5 % [IRR 1.05 (95% CI, 1.03-1.08)] increase in beta-agonist use in the previous 2 weeks.  Similar relationships were found between health outcomes and PM_2.5 levels, though not all were statistically significant.  Thus, Center investigators have concluded that indoor PM from inner-city Baltimore homes is significantly associated with asthma morbidity. A manuscript based on this research is in preparation and Center investigators expect to submit it for publication by the end of the year.

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