Asthma is a complex disease influenced by both genetics and environmental exposures, but the pathogenesis still remains unclear. Chitinase and chitinase-like proteins (CLPs) recently identified in humans have been found to play a significant role in both inflammation and asthma. Chitin - the ligand of these functional and non-functional enzymes -is a pathogen-associated molecular pattern that induces innate immune pathways, induces a Th2-type eosinophilic inflammation, and can act as an adjuvant for sensitization to bystander proteins. Chitin is an insoluble, long chain polymer of ?1-4-N-acetyl-D-glucosamine and is a structural component of common indoor organisms such as dust mites, cockroaches, and fungi that are known asthma triggers. Chitin will be common in the environment where these organisms are abundant. Exposure to elevated levels of fungi in individuals with specific polymorphisms in a chitinase gene (CHIT1) is associated with increased asthma symptoms, strongly implicating a gene by environment interaction. Increasing evidence suggests both chitinases and chitin play a significant role in asthma, hence it is critically important to evaluate the impact of environmental chitin exposure on asthmatic populations. However, there is currently no way to directly assess chitin loads in the indoor environment since there is no assay available to do so, as there is for indoor allergens. The lack of a chitin specific assay is a critical barrier to our ability to assess the extent to which chitin exposure i contributing to the exacerbation and development of asthma. The long-term goal of the research is to understand the role of airborne microbial exposures (and components of them e.g. chitin) in the development and exacerbation of asthma. Our objective is to develop an ELISA assay for quantifying chitin in environmental samples from air or dust. We will systematically examine the specificities of currently available chitin-binding proteins, choose the most optimal, and examine its specificity for further development in an ELISA assay. We will develop a protocol for testing environmental samples with issues unique to handling and detection of insoluble chitin. Finally we will use the new chitin assay on archived dust samples from previous cohort studies and will compare chitin content with existing measures of chitin-containing organisms (culturable fungi) and their allergens such as Der p1 and Der f1 from dust mites, Bla g1 from cockroach, and Alt a1 from Alternaria alternata. The successful outcome of this research and the production of a well characterized chitin environmental assay will have a considerable impact on the field, allowing it to advance in exploring the extent to which chitin exposure has an impact on asthma exacerbation and development and the extent of any gene - environment interaction.
Asthma is increasing in prevalence and is strongly associated with a variety of environmental exposures. This project will develop a new environmental assay for chitin that will allow future assessments of its role in the development and progression of allergic sensitization and asthma that, if significant, could lead to new public health interventions to reduce allergic disease.