The human immune system is often exposed to bacterial ligands through interactions with the microbiome and infections. Bacterial biofilms are associated with numerous human infections. The predominant protein expressed in enteric biofilms is amyloid curli that forms highly immunogenic complexes with DNA. Infection with curli- expressing bacteria or systemic exposure to purified curli-DNA complexes of Salmonella biofilms trigger autoimmunity via the generation type I interferons and anti-double stranded (ds)DNA. However, the mechanisms involved in the pro-autoimmune effects of curli/DNA complexes remain unknown. The primary objective of this application is to elucidate the mechanisms by which bacterial amyloids are recognized by the immune system, leading to their pathogenic effects in the host. Our central hypothesis is that curli/DNA complexes are pathogenic molecules that act by accessing multiple cellular compartments and engaging several Pattern Recognition Receptors, including, TLR2, TLR9 and NLRP3 resulting in inflammation and autoimmune responses. It is our expectation that successful completion of the proposed studies will identify bacterial amyloids as a novel powerful Pathogen-Associated Molecular Pattern (PAMP) that is recognized by the immune system via multiple receptors and establish a new paradigm that infections with amyloid- expressing bacteria are major environmental trigger fir complex human diseases.

Public Health Relevance

Enteric bacterial amyloid curli and DNA form complexes that are highly immunostimulatory and could lead to an autoimmune response during infection. Indeed, infection with curli-expressing bacteria accelerates the progress of a human autoimmune disease, systemic lupus erythematosus (SLE). Successful completion of the proposed study will have broader implications for amyloid expressing bacterial infections and amelioration of autoimmunity.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21AI132996-02
Application #
9501678
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Johnson, David R
Project Start
2017-06-15
Project End
2019-05-31
Budget Start
2018-06-01
Budget End
2019-05-31
Support Year
2
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Temple University
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
057123192
City
Philadelphia
State
PA
Country
United States
Zip Code
19122
Biesecker, Steven G; Nicastro, Lauren K; Wilson, R Paul et al. (2018) The Functional Amyloid Curli Protects Escherichia coli against Complement-Mediated Bactericidal Activity. Biomolecules 8: