In this application we will explore the hypothesis that Toll-like receptor 2 (TLR2) is the master regulator controlling both protective and pathologic features of the tubercle granuloma. The hypothesis builds on novel findings made in our laboratory. Previously we had reported that TLR9 and TLR2 induce pro- and anti-inflammatory cytokines, respectively, in M. tuberculosis (Mtb)-infected dendritic cells (DCs), while TLR2 induces both pro- and anti-inflammatory cytokines in infected macrophages. A reasonable prediction, based on these observations, is that during Mtb infection the innate anti-inflammatory response triggered by TLR2 may control the magnitude of Th1 effector and memory T cell activation. Contrary to expectation, we found that the absence of TLR2 did not affect the magnitude of the Th1 effector response generated following aerosol infection with Mtb or the induction of recall Th1 memory immunity in response to Mtb challenge. However, the consequence of TLR2 absence to host resistance was manifested at the level of the granuloma. The infected lungs of TLR2KO mice exhibited enhanced inflammation associated with reduced infiltration of FoxP3[+] T regulatory cells (Tregs) into the lung, while lungs from infected WT animals had resolved their inflammation and had small, compact granulomas. Tregs have been shown to thwart host antimicrobial responses against persistent pathogens. Surprisingly, despite the absence of Tregs, lungs from chronically-infected TLR2KO mice exhibited enhanced bacterial burden and loss of granuloma integrity in comparison with infected WT mice indicating a hitherto under-appreciated role for TLR2 in controlling antimicrobial responses in vivo in the granuloma. Preliminary gene expression studies point to the role of TLR2-induced matrix metaloproteinases in regulating granuloma maturation. The following specific hypotheses will be tested in the proposal: i) TLR2-induced MMPs regulate granuloma maturation;ii)TLR2 is essential for macrophage control of Mtb replication and containment within the granuloma;iii) TLR2 induces Tregs which operate primarily as inhibitors of lung immune pathology but not as inhibitors of macrophage antimicrobial responses;iv) TLR2-triggers two distinct signaling pathways for the induction of pro- and anti-inflammatory cytokine production within Mtb- infected macrophages, and v) the signaling pathways cross-regulate each other and Mtb can maneuver the pathways to its own benefit. The collective findings from the proposed studies will provide insights into TLR2-triggered signaling pathways in the tubercle granuloma and unique ways in which they can be manipulated therapeutically.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI084822-03
Application #
8433535
Study Section
Immunity and Host Defense Study Section (IHD)
Program Officer
Jacobs, Gail G
Project Start
2011-03-01
Project End
2013-06-30
Budget Start
2013-03-01
Budget End
2013-06-30
Support Year
3
Fiscal Year
2013
Total Cost
$163,536
Indirect Cost
$58,705
Name
University of Medicine & Dentistry of NJ
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
623946217
City
Newark
State
NJ
Country
United States
Zip Code
07107