Periodontitis is classified as a microbiota shift disease, whereby a very rich and diverse commensal flora characteristic for good oral health becomes dominated by several Gram-negative, anaerobic bacterial species, among which, Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola constitute the so called """"""""red complex"""""""" of microorganisms frequently associated with the development and progression of the disease. The common consequence of these three bacteria and a secondary periodontopathogen, Prevotella intermedia, is their production of proteolytic enzymes. Proteases of P. gingivalis and T. denticola are known to dysregulate tissue homeostasis and/or to frustrate defensive inflammatory responses, thus, significantly contributing to pathological changes in the infected periodontium. In contrast, virtually nothing is known about proteases of T. forsythia and P. intermedia although it has been well documented that proteases from the former organism are produced in vivo and their activity correlates with periodontal destruction. Here, we postulate that novel proteases produced by T. forsythia (forsypsin) and P. intermedia (interpains) promote periodontal tissue damage by deregulation of tightly controlled host proteolytic systems. Furthermore, we suggest that the combined proteolytic activity produced locally by periodontopathogens may be a primary mechanism for synergistic periodontal tissue damage and contributes to mutual survival of the red complex bacteria. Most interestingly, we have found that forsypsin and interpains, as well as many other acknowledged virulence factors of P. gingivalis and T. forsythia share with gingipains a conserved C-terminal domain. We have shown that this domain, together with a unique periplasmic protein and a unique outer membrane translocon protein conserved in these species is essential for gingipain secretion. This implies that a novel bacterial protein export system is employed by periodontopathogens to secrete a number of confirmed and putative virulence factors. For these reasons, the specific aims of this project are as follows: 1) to use an array of biochemical and molecular biological methods to investigate the mechanism of gingipain translocation through the outer membrane of P. gingivalis and confirm the presence of this unique secretion pathway in both T. forsythia and P. intermedia;2) to characterize novel proteases from T. forsythia and P. intermedia, especially with regard to their ability to complement and/or synergize with the gingipain activity, and 3) to determine the complementary or synergistic role of proteases from P. gingivalis, T. forsythia and P. intermedia for in vivo proliferation and dissemination of bacteria in monomicrobial and mixed microbial infections using a murine chamber model.

Public Health Relevance

The results of these proposed studies should not only illuminate the synergistic role of bacterial proteases in mixed infections but also shed light on a novel pathway for the secretion of virulence factors unique to P. gingivalis, T. forsythia and P. intermedia. This insight may enable the design of antibodies or chemical compounds to block the export of multiple virulence factors from major periodontopathogens, which in the long term, may revolutionize treatment and prophylaxis of periodontal disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE009761-19
Application #
8089488
Study Section
Oral, Dental and Craniofacial Sciences Study Section (ODCS)
Program Officer
Lunsford, Dwayne
Project Start
1991-08-01
Project End
2013-06-30
Budget Start
2011-07-01
Budget End
2012-06-30
Support Year
19
Fiscal Year
2011
Total Cost
$299,325
Indirect Cost
Name
University of Louisville
Department
Dentistry
Type
Schools of Dentistry
DUNS #
057588857
City
Louisville
State
KY
Country
United States
Zip Code
40292
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