The inflammatory airway response in asthma may be the result of immune cells that are dysregulated towards environmental factors such as airborne fungi. The long-term goal of this project is to better understand the pathophysiological mechanisms of Th2-type airway inflammation in asthma. Exposure to the fungus, Alternaria, has long been implicated in the development and exacerbation of human asthma. After intranasal exposure to Alternaria spores and individual proteins, naive mice exhibit marked eosinophilic airway inflammation, enhanced Th2 sensitization to innocuous antigens, and airway hyperreactivity. Despite the well-documented clinical importance of Alternaria in the development, onset, and exacerbation of allergic airway diseases such as asthma, little knowledge exists about the role of individual fungal products in these pathological states. The importance of and detailed mechanisms of allergen uptake and movement through the epithelial cell layer (endocytosis and transcytosis) have not been explored to any great extent. This innovative project focuses on the secreted major Alternaria allergen Alt_a_1. It will assess the role of Alt_a_1 in allergic disease by utilizing bronchoalveolar epithelial cells and murine models of airway inflammation. We have discovered that Alt_a_1 is proinflammatory and harbors a unique amino acid motif (RXLR) that facilitates binding to cell surface PI-3-P and cellular entry.
In aim 1 the role of Alt_a_1 in innate and adaptive immune responses in vitro and in murine models of asthma will be investigated. The effects of recombinant Alt_a_1 protein and fungal knockout mutants lacking Alt_a_1 will be examined.
In specific aim 2 the importance of the Alt_a_1's esterase activity and RXLR motif in cellular entry and immunological responses will be characterized. Recombinant Alt_a_1 will be used to define amino acid residues required for esterase activity, for PI-3-P binding, and for cellular entry. Epithelial cell immune responses following treatment with the Alt_a_1 proteins will be investigated. This project will lead to a better understanding of the mechanisms of persistent and recurrent airway inflammation and may lead to the development of more specific and effective therapies and prevention strategies, especially if PI-3-P-mediated cell entry proves of general importance to allergenicity.

Public Health Relevance

Westernized countries are experiencing striking increases in the prevalence of asthma. Successful completion of this project will increase our understanding of the pathogenesis mechanisms of the allergic asthma-associated, airborne fungus, Alternaria. Successful execution of this project may provide insight into the design and implementation of novel therapeutic approaches for prevention and treatment of allergic asthma due to sensitivity to airborne fungi and possibly other sources of allergens.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21AI094071-02
Application #
8313847
Study Section
Special Emphasis Panel (ZRG1-IMM-K (02))
Program Officer
Minnicozzi, Michael
Project Start
2011-08-05
Project End
2013-07-31
Budget Start
2012-08-01
Budget End
2013-07-31
Support Year
2
Fiscal Year
2012
Total Cost
$195,967
Indirect Cost
$70,967
Name
Virginia Polytechnic Institute and State University
Department
None
Type
Organized Research Units
DUNS #
003137015
City
Blacksburg
State
VA
Country
United States
Zip Code
24061