Stephen H. Gregory Associate Professor of Medicine (Research)

Brown Affiliations

scholarly work

3. Gehring S, Dickson E, San Martin M, van Rooijen N, Papa EF, Harty MW, Tracy TF, Jr, Gregory SH. Kupffer cells abrogate cholestatic liver injury in mice. Gastroenterology 130:810-822, 2006.

2. Kuzushita N, Gregory SH, Monti NA, Gehring S, Wands JR. Vaccination with protein-transduced dendritic cells elicits a sustained response to hepatitis C viral antigens. Gastroenterology 130:453-464, 2006.

1. Lomas-Neira J, Chung CS, Perl, M, Gregory SH, Biffl W, Ayala A. Role of alveolar macrophage & migrating neutrophils in hemorrhage induced priming for ALI subsequent to septic challenge. Amer J Physiol 290:51-58, 2006.

5. Harty MW, Huddleston HM, Papa EF, Puthawala M, Tracy AP, Ramm G, Gehring S, Gregory SH, Tracy TF, Jr. Repair following cholestatic liver injury correlates with neutrophil infiltration and matrix metalloproteinase 8 activity. Surgery 138:313-320, 2005.

4. Wesche-Soldato DE, Chung CS, Lomas-Neira J, Doughty LA, Gregory SH, Ayala A. In vivo delivery of Caspase 8 or Fas siRNA improves the survival of septic mice. Blood 106:2295-2301, 2005.

6. Gehring S, Gregory SH, Kuzushita N, Wands JR. Type 1 interferon augments DNA-based vaccination against hepatitis C virus core protein. J Med Virol 75:249-257, 2004.

8. Wu H, Prince JE, Brayton CF, Shah C, Zeve D, Kaplan SL, Gregory SH, Smith CW, Ballantyne CM. Host resistance of CD18 knockout mice against systemic infection with Listeria monocytogenes. Infect Immun 71:5986-5993, 2003.

7. Lomas JL, Chung C-S, Grutkoski PS, LeBlanc BW, Lavigne L, Reichner J, Gregory SH, Doughty LA, Cioffi WG, Ayala A. Differential effects of MIP-2 and KC on hemorrhage induced neutrophil priming for lung inflammation: assessment by adoptive transfer in mice. Shock 19:358-365, 2003.

11. Ayala A, Chung C-S, Lomas JL, Song GY, Doughty LA, Gregory SH, Cioffi WG, LeBlanc BW, Reichner J, Simms HH, Grutkoski PS: Shock-induced neutrophil mediated priming for acute lung injury following sepsis in the mouse: divergent effects of TLR-4 opposed to combined TLR-4/FasL deficiency. Amer J Pathol 161:2283-2294, 2002.

10. Gregory SH, Wing EJ: Neutrophil-Kupffer cell interaction: a critical component of host defenses to systemic bacterial infections. J Leukoc Biol 72: 239-248, 2002.

9. Gregory SH, Cousens LP, van Rooijen N, Döpp EA, Carlos TM, Wing EJ: Complementary adhesion molecules promote neutrophil-Kupffer cell interaction and the elimination of bacteria taken up by the liver. J Immunol 168:308-315, 2002.

12. Gregory SH, Sagnimeni AJ, Zurowski NB, Thomson AW: Flt3 ligand promotes protective immunity to Listeria monocytogenes. Cytokines 13:202-208, 2001.

research overview

Currently, our laboratory is conducting experiments using mouse models to determine the factors that cause inflammation and protective immunity to bacteria that infect the liver and/or lungs.

research statement

Biodefense and emerging pathogens

Francisella tularensis, the causative agent of tularemia, is one of the most infectious bacteria known to man, as few as 10 organisms can cause fatal disease. Aerosolized F. tularensis represents a potentially dangerous biological weapon due to its high degree of infectivity, ease of dissemination, and capacity to cause severe illness. No safe vaccine is presently available for general use. Currently, our laboratory is conducting experiments to determine the factors that facilitate protective immunity to pneumonic tularemia using laser capture microdissection (LCM) to isolate relevant immune cell populations from the lungs of immune and non-immune mice infected with F. tularensis, and DNA microarray and real-time RT-PCR analyses to characterize gene expression. The significance of specific gene products to host defenses will be determined by treating mice with sequence-specific siRNA to knock-down gene expression and product synthesis. In response to an National Institute of Allergy and Infectious Diseases (NIAID) Biodefense initiative, experiments are also underway to develop a DNA-based vaccine and an immunization strategy to elicit protective mucosal immunity. The efficacy of resultant vaccine candidates will be tested in "humanized," HLA class I and class II double-transgenic mice challenged with aerosolized F. tularensis.

In addition to these studies, substantial effort in our laboratory is dedicated to delineating the factors that cause clearance of bacteria from the bloodstream and their elimination in the liver. Previously, we reported that efficient elimination depends upon the complex interaction of resident tissue macrophages (Kupffer cells) that line the liver sinusoids and bactericidal neutrophils, which accumulate rapidly in the liver in response to infection. To our knowledge, these studies represent the first documented evidence to indicate that the critical function of Kupffer cells may relate far more to their ability to regulate the proinflammatory or antimicrobial activities of other cell types (e.g., neutrophils in this instance) than to their own capacity to ingest and kill microorganisms.

The ability of Kupffer cells to modulate the biological activity of other cells is supported by our recent studies demonstrating the Kupffer-cell-dependent abrogation of cholestatic liver injury in a mouse model. Hepatocellular apoptosis and necrosis were exacerbated in Kupffer-cell-depleted or IL-6-deficient mice following ligation of the common bile duct. Recombinant IL-6 administered at the time of surgery reversed the severe liver damage seen otherwise in Kupffer-cell-depleted animals, thus demonstrating the critical role of IL-6 in protection. Similarly, invariant (i)NKT cells (a unique T cell population characterized by its ability to recognize glycolipids rather than peptides of host cell origin) alleviate liver injury in this model. Relative to wild-type animals, iNKT cell-deficient mice exhibit increased liver damage following bile duct ligation. This latter finding suggests the principal function of hepatic iNKT cells may be to moderate inflammation and suppress tissue injury rather than to mediate innate immunity to bacterial pathogens as broadly speculated in the literature.

funded research

1.Title: Francisella tularensis: innate resistance to inhalation
Role: Principal Investigator Assignment: R21 AI055657
Percent Effort: 30% Support: $200,000/year direct costs
Granting Agency: NIH/National Institute of Allergy and Infectious Diseases (NIAID) Period: 9/15/03 – 09/14/05 (no cost extension until 09/2006)
Aims: Determine the function of alveolar macrophages in innate host resistance to aerosolized F. tularensis using a mouse model.

2. Title: Neutrophil-macrophage interactions govern liver immunity
Role: Principal Investigator Assignment: 1R01 DK068097-02
Percent Effort: 30% Support: $180,000/year direct costs requested
Granting Agency: NIH/National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Period: 03/10/06 – 02/28/11
Aims: Determine the consequences of neutrophil-Kupffer cell and neutrophil-inflammatory macrophage interactions relevant to innate host defenses to systemic bacterial infections.

3. Title: A collaborative for vaccine research and development (Anne DeGroot, PI)
Role: Co-investigator Assignment:
Percent Effort: 5% Support: $70,000/yr direct costs ($25,000 to Gregory/Rhode Island Hospital (RIH))
Granting Agency: Brown University Period: 4/1/04-3/31/04
Aims: Create a human MHC class I (HLA-A*0201)/MHC class II (DRB1*0101) double transgenic mouse colony. Vaccinate mice with a DNA construct that encodes immunodominant epitopes derived from Francisella tularensis and expressed by A*0201 or DRB1. Assess the humoral and cell mediated responses.

4. Title: A genome-derived, epitope-driven tularemia vaccine (Anne De Groot, PI)
Role: Co-investigator Assignment: 1 R43 AI058326
Percent Effort: 15% Support: $859,773 total costs/2 years ($438,433 direct + indirect costs subcontracted to Gregory/RIH for the 2-year period)
Granting Agency: NIH/NIAID Period: 10/01/04-9/30/06
Aims: Develop a multi-epitope DNA vaccine against aerosolized Francisella tularensis

5. Title: Regulatory mechanisms of acute lung injury: phagocyte apoptosis (Alfred Ayala, PI)
Role: Collaborator Assignment: R01-HL073525
Percent Effort: 3% Support: $250,000/year direct costs
Granting Agency: NIH/National Heart, Lung and Blood Institute (NHLBI) Period: 9/1/03-8/31/07
Aims: The global objective of this was to determine the contribution of the neutrophil apoptotic response to the development of acute lung injury induced by a salient two-hit model of hemorrhage (priming) followed by subsequent infectious polymicrobial septic challenge (triggering) in the mouse

6. Title: Differential effects of sepsis on macrophage function (Alfred Ayala, PI)
Role: Collaborator Assignment: R01-GM46354-11
Percent Effort: 3% Support: $250,000/year direct costs
Granting Agency: NIH/National Institute of General Medical Sciences (NHGMS) Period: 9/1/03-8/31/07
Aims: The objectives of this project are to determine how sepsis, as opposed to chronic low dose endotoxin infusion, alters various macrophage, lymphocyte, and hepatocyte functional capacities in mice.

7. Title: Programmed cell death: role in septic immune suppression (Alfred Ayala, PI)
Role: Collaborator Assignment: R01GM053209
Percent Effort: 1% Support: $250,000/year direct costs
Granting Agency: NIH/NHGMS Period: 10/01/04-9/30/09
Aims: Determine the role of Fas ligand induced apoptosis of lymphocytes and macrophages in the aberrant response to septic stimuli and immune/nonimmune cell dysfunction.