Monocytes and macrophages sense pathogens, tumors, tissue damage, and host-derived mediators in their environment and respond by differentiating into distinct functional phenotypes that mediate host innate immune responses. However, the process of macrophage differentiation has been described in terms of its """"""""plasticity,"""""""" implying that these cells can modulate their functions reversibly through differentiation in response to rapid changes in the environment. For example, """"""""classically activated"""""""" macrophages (CA-MX) are highly microbicidal, yet their production of inflammatory cytokines and nitric oxide may damage host tissue. At the other end of the functional spectrum, """"""""alternatively activated"""""""" macrophages (AA-MX), induced by IL-4 and IL- 13, mediate """"""""wound healing"""""""" through elimination of damaged tissue and other anti-inflammatory mechanisms. For the past 26 years of this grant, my laboratory has sought to understand more fully the complex molecular underpinnings of macrophage differentiation and how this impacts host defenses and disease outcome. Our work in this funding cycle has focused primarily on the mechanisms by which Toll-like receptor (TLR) signaling induced by conserved microbial structures, such as bacterial lipopolysaccharide (LPS) or Respiratory Syncytial Virus (RSV) fusion (F) protein, and cell-derived cytokines, such as interferons (IFNs), drive this complex process. In the proposed application, the overarching hypothesis to be tested is that activation of specific intracellular signaling pathways distal to TLR and/or cytokine receptor engagement programs expression of discrete cassettes of pro- and anti-inflammatory genes that dictate the manner in which the host responds to infection.
Three Specific Aims are proposed to test this hypothesis in vitro and in vivo, with the ultimate goal of identifying novel therapeutic interventions for diseases where macrophages are required for containing the invading pathogen or preventing or repairing tissue damage caused by pathogens. This proposal details innovative experimental approaches that will: (1) define the earliest interactions between MyD88, IRAK1 and IRAK4, and TRAF6 that mediate TLR-dependent signaling and identify compensatory signaling pathways that will protect against IRAK4 deficiency in response to bacterial and viral infections;(2) elucidate novel mechanisms through which TLR signaling is negatively regulated, either through depletion of membrane- associated TIRAP or through previously unrecognized mechanisms of endotoxin tolerance, and (3) examine the roles of TLR4 and IFN-b in the induction of AA-MX as a mechanism for prevention or repair of lung damage induced by RSV infection. At the conclusion of these comprehensive studies, we will have defined processes that govern the initial interaction of TLR agonists and/or IFN that lead to changes in macrophage activation with the expectation that this knowledge will translate into reasonable therapeutic approaches for controlling tumors or invading pathogens or counteracting inflammatory damage to tissues induced by pathogens.

Public Health Relevance

Macrophages are white blood cells that are the front line of defense against many pathogens. An in- depth understanding of how macrophages sense and respond to invading microbes, obtained by analyzing the molecular processes that mediate their functions, is the goal of this project. Our findings will lead to development of new drugs that will increase the capacity of macrophages to kill bacteria and viruses more effectively or to prevent or repair damage to tissues caused by bacterial or viral infection.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Immunity and Host Defense (IHD)
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Minnicozzi, Michael
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University of Maryland Baltimore
Schools of Medicine
United States
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Prantner, Daniel; Perkins, Darren J; Vogel, Stefanie N (2017) AMP-activated Kinase (AMPK) Promotes Innate Immunity and Antiviral Defense through Modulation of Stimulator of Interferon Genes (STING) Signaling. J Biol Chem 292:292-304
Prantner, Daniel; Shirey, Kari Ann; Lai, Wendy et al. (2017) The ?-defensin retrocyclin 101 inhibits TLR4- and TLR2-dependent signaling and protects mice against influenza infection. J Leukoc Biol 102:1103-1113
Perrin-Cocon, Laure; Aublin-Gex, Anne; Sestito, Stefania E et al. (2017) TLR4 antagonist FP7 inhibits LPS-induced cytokine production and glycolytic reprogramming in dendritic cells, and protects mice from lethal influenza infection. Sci Rep 7:40791
Perkins, Darren J; Vogel, Stefanie N (2016) Inflammation: Species-specific TLR signalling -- insight into human disease. Nat Rev Rheumatol 12:198-200
Keegan, Achsah D; Shirey, Kari Ann; Bagdure, Dayanand et al. (2016) Enhanced allergic responsiveness after early childhood infection with respiratory viruses: Are long-lived alternatively activated macrophages the missing link? Pathog Dis 74:
Perkins, Darren J; Rajaiah, Rajesh; Tennant, Sharon M et al. (2015) Salmonella Typhimurium Co-Opts the Host Type I IFN System To Restrict Macrophage Innate Immune Transcriptional Responses Selectively. J Immunol 195:2461-71
Rajaiah, Rajesh; Perkins, Darren J; Ireland, Derek D C et al. (2015) CD14 dependence of TLR4 endocytosis and TRIF signaling displays ligand specificity and is dissociable in endotoxin tolerance. Proc Natl Acad Sci U S A 112:8391-6
Piao, Wenji; Shirey, Kari Ann; Ru, Lisa W et al. (2015) A Decoy Peptide that Disrupts TIRAP Recruitment to TLRs Is Protective in a Murine Model of Influenza. Cell Rep 11:1941-52
Mistry, Pragnesh; Laird, Michelle H W; Schwarz, Ryan S et al. (2015) Inhibition of TLR2 signaling by small molecule inhibitors targeting a pocket within the TLR2 TIR domain. Proc Natl Acad Sci U S A 112:5455-60
Perkins, Darren J; Vogel, Stefanie N (2015) Space and time: New considerations about the relationship between Toll-like receptors (TLRs) and type I interferons (IFNs). Cytokine 74:171-4

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