Actinobacillus actinomycetemcomitans is a Gram-negative, facultative anaerobic bacterium that colonizes the human oral cavity and the upper respiratory tract. This bacterium is strongly associated with localized aggressive periodontitis (LAP) and with cases of adult periodontitis. This pathogen is the causative agent for other serious infections including infectious endocarditis, soft tissue abscesses, pneumonia, and may contribute to cardiovascular disease. The periodontium is believed to be the source for these non-oral diseases, but little is known about the tropism used by A. actinomycetemcomitans to colonize the oral cavity and to infiltrate and disseminate in tissues. Pathogens have developed diverse strategies to be successful in colonization of host tissues. A common theme amongst these pathogens is the ability to initiate infection by adhesion to specific host macromolecules under stringent or hostile conditions. These molecules include proteins secreted by host cells that form the extracellular matrix (ECM). A. actinomycetemcomitans is found in the connective tissue of the periodontium and in close association with collagen fibers in infected tissues. The bacterium also binds to the ECM proteins, collagen, fibronectin and laminin. Using a genetic approach, we have identified the first A. actinomycetemcomitans collagen adhesin, Ema (extracellular matrix protein adhesin) A and multiple genes involved in regulating the expression of ECM protein adhesin activity. EmaA is structurally related to YadA, a multipurpose ECM protein adhesin of the enteropathogenic bacterium Yersinia enterocolitica, and is associated with bacterial cell surface appendages. These EmaA structures are proposed to be fundamental for collagen adhesion. To elucidate the role of EmaA in colonization and pathogenicity of the bacterium, we propose to 1) map the functional domains of EmaA by determining the collagen binding, subcellular localization, and assembly of surface structures in A. actinomycetemcomitans, 2) investigate the surface structures associated with EmaA by transmission electron microscopy and the role of these structures in resistance to the innate immune response of the host, and 3) determine the number of EmaA molecules required for the assembly of structures on the surface of A. actinomycetemcomitans. A long term goal of the proposed research is to identify and characterize bacterial adhesins that are required for the colonization of the oral cavity and non-oral tissues. These adhesins may serve as targets for future drug development involving small molecules or vaccines that disrupt host-pathogen interactions. Lay statement: Binding to host tissues is the initial phase of all infectious diseases. Understanding how bacteria interact with host cells or tissue constituents will aid in the development of novel therapeutics to prevent initiation or progression of the disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE013824-09
Application #
7637408
Study Section
Oral, Dental and Craniofacial Sciences Study Section (ODCS)
Program Officer
Lunsford, Dwayne
Project Start
2000-07-01
Project End
2011-06-30
Budget Start
2009-07-01
Budget End
2010-06-30
Support Year
9
Fiscal Year
2009
Total Cost
$346,676
Indirect Cost
Name
University of Vermont & St Agric College
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
066811191
City
Burlington
State
VT
Country
United States
Zip Code
05405
Azari, Fereshteh; Radermacher, Michael; Mintz, Keith P et al. (2012) Correlation of the amino-acid sequence and the 3D structure of the functional domain of EmaA from Aggregatibacter actinomycetemcomitans. J Struct Biol 177:439-46
Tang, G; Kawai, T; Komatsuzawa, H et al. (2012) Lipopolysaccharides mediate leukotoxin secretion in Aggregatibacter actinomycetemcomitans. Mol Oral Microbiol 27:70-82
Jiang, X; Ruiz, T; Mintz, K P (2012) Characterization of the secretion pathway of the collagen adhesin EmaA of Aggregatibacter actinomycetemcomitans. Mol Oral Microbiol 27:382-96
Tang, Gaoyan; Ruiz, Teresa; Mintz, Keith P (2012) O-polysaccharide glycosylation is required for stability and function of the collagen adhesin EmaA of Aggregatibacter actinomycetemcomitans. Infect Immun 80:2868-77
Jiang, X; Ruiz, T; Mintz, K P (2011) The extended signal peptide of the trimeric autotransporter EmaA of Aggregatibacter actinomycetemcomitans modulates secretion. J Bacteriol 193:6983-94
Tang, Gaoyan; Mintz, Keith P (2010) Glycosylation of the collagen adhesin EmaA of Aggregatibacter actinomycetemcomitans is dependent upon the lipopolysaccharide biosynthetic pathway. J Bacteriol 192:1395-404
Yu, Chunxiao; Mintz, Keith P; Ruiz, Teresa (2009) Investigation of the three-dimensional architecture of the collagen adhesin EmaA of Aggregatibacter actinomycetemcomitans by electron tomography. J Bacteriol 191:6253-61
Gallant, Claude V; Sedic, Maja; Chicoine, Erin A et al. (2008) Membrane morphology and leukotoxin secretion are associated with a novel membrane protein of Aggregatibacter actinomycetemcomitans. J Bacteriol 190:5972-80
Yu, Chunxiao; Ruiz, Teresa; Lenox, Christopher et al. (2008) Functional mapping of an oligomeric autotransporter adhesin of Aggregatibacter actinomycetemcomitans. J Bacteriol 190:3098-109
Tang, Gaoyan; Kitten, Todd; Munro, Cindy L et al. (2008) EmaA, a potential virulence determinant of Aggregatibacter actinomycetemcomitans in infective endocarditis. Infect Immun 76:2316-24

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