Francisella tularensis (Ft), the causative agent of fatal human disease tularemia has long been developed as a biological weapon due to its ability to cause severe illness. Ft is now classified as a category A select agent by the CDC based on its possible use as a bioterror agent. Ft is an intracellular pathogen. During its replication cycle, Ft escapes from the phagosome and replicates within the cytosol of several cell types; thus, the role of cytosolic pattern recognition receptors, especially the NLRs and inflammasome in innate immunity against Ft assumes great importance. The inflammasome is a cytosolic multi-protein complex that activates caspase1 to produce pro-inflammatory cytokines IL-1? and IL-18 required for recruitment and activation of other immune cells to promote bacterial clearance. Very little is known regarding the role of the inflammasome in host defense against virulent Ft strains. Our overall hypothesis is that active repression of the inflammasome is essentially required for intracellular survival of Ft. Results from the studies conducted during our two previous R15 funding cycles have demonstrated that Ft encoded factors suppress Aim2 and Nlrp3 inflammasomes; both the Aim2 and Nlrp3 are dispensable for vaccine-induced protective immune responses; and Nlrp3 plays an inflammasome-independent detrimental role in Ft infected macrophages and mice. The scientific premise of the current proposal is built upon two unanswered questions emanating from these studies: (1) what are the consequences of suppression of the Aim2 inflammasome by Ft on the overall development of innate immune responses? (2) How does Nlrp3 exert its detrimental effects on the host following Ft infection? In specific aim 1, we will investigate the mechanisms through which Aim2 regulates the host?s immunity to Ft infection. We will investigate the consequences of suppression of the Aim2 inflammasome on the overall development of innate immune responses during Francisella infection. The inflammasome-independent roles of NLRs, especially as negative regulators of inflammation, have come to the forefront in recent years. Our preliminary studies demonstrate that Nlrp3 increases the susceptibility of mice and suppresses the production of pro-inflammatory cytokines in mice and macrophages infected with Ft.
In specific aim 2, we will investigate the mechanisms through which Nlrp3 regulates the host?s immunity and plays a detrimental role by dampening the host?s innate immune responses against Francisella. These proposed studies are novel and will enhance our understanding of the unique pathogenic mechanisms of Ft, which are essential for the development of effective therapeutics and vaccines against tularemia.

Public Health Relevance

The potential of Francisella tularensis, a Category A bioterror agent to cause severe infection is due to its ability to suppress the host?s innate immune system. The proposed studies will explore how Francisella evades the host innate immune responses. Defining the molecular mechanism(s) of suppression of innate immunity will be an essential first step towards the development of immunotherapeutic, as well as effective vaccine strategies to combat this fatal disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Academic Research Enhancement Awards (AREA) (R15)
Project #
2R15AI107698-03
Application #
10046747
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Mukhopadhyay, Suman
Project Start
2013-07-16
Project End
2023-08-31
Budget Start
2020-09-08
Budget End
2023-08-31
Support Year
3
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Albany College of Pharmacy
Department
Social Sciences
Type
Schools of Arts and Sciences
DUNS #
797866969
City
Albany
State
NY
Country
United States
Zip Code
12208
Mansour, Ahd A; Banik, Sukalyani; Suresh, Ragavan V et al. (2018) An Improved Tobacco Mosaic Virus (TMV)-Conjugated Multiantigen Subunit Vaccine Against Respiratory Tularemia. Front Microbiol 9:1195
Alqahtani, Maha; Ma, Zhuo; Ketkar, Harshada et al. (2018) Characterization of a Unique Outer Membrane Protein Required for Oxidative Stress Resistance and Virulence of Francisella tularensis. J Bacteriol 200:
Rabadi, Seham M; Sanchez, Belkys C; Varanat, Mrudula et al. (2016) Antioxidant Defenses of Francisella tularensis Modulate Macrophage Function and Production of Proinflammatory Cytokines. J Biol Chem 291:5009-21
Ma, Zhuo; Russo, Vincenzo C; Rabadi, Seham M et al. (2016) Elucidation of a mechanism of oxidative stress regulation in Francisella tularensis live vaccine strain. Mol Microbiol 101:856-78
Banik, Sukalyani; Mansour, Ahd Ahmed; Suresh, Ragavan Varadharajan et al. (2015) Development of a Multivalent Subunit Vaccine against Tularemia Using Tobacco Mosaic Virus (TMV) Based Delivery System. PLoS One 10:e0130858
Suresh, Ragavan Varadharajan; Ma, Zhuo; Sunagar, Raju et al. (2015) Preclinical testing of a vaccine candidate against tularemia. PLoS One 10:e0124326
Ma, Zhuo; Banik, Sukalyani; Rane, Harshita et al. (2014) EmrA1 membrane fusion protein of Francisella tularensis LVS is required for resistance to oxidative stress, intramacrophage survival and virulence in mice. Mol Microbiol 91:976-95