Molecular Basis of Human Phagocyte Interactions With Bacterial Pathogens

Human phagocytic cells such as polymorphonuclear leukocytes (PMNs) are readily mobilized to sites of infection and ingest microorganisms by a process known as phagocytosis. The combined effects of reactive oxygen species (ROS) and proteolytic peptides and enzymes released into forming bacterial phagosomes kill most ingested bacteria. However, many human bacterial pathogens have devised means to subvert normal phagocyte responses and the innate immune response and cause severe disease.

The overall objective of this study is to elucidate specific features of pathogen-phagocyte interactions that underlie evasion of the innate immune response or contribute to the pathophysiology of disease or inflammatory disorders. Therefore, specific projects will:

1. Identify and characterize specific mechanisms used by pathogenic microorganisms to evade or subvert normal phagocyte responses and therefore cause disease.
2. Investigate phagocyte response mechanisms to specific pathogenic microorganisms.
3. Identify specific bacterial structures and/or (gene) products that dictate differences in phagocyte responses among a range of pathogens so that generalized statements can be made about the pathophysiology of disease states.

The studies will be performed using multiple techniques including state-of-the-art equipment for genomics and proteomics strategies to identify target bacterial genes/proteins of interest or those up-regulated in phagocytes. Phagocyte-pathogen interactions will be examined using fluorescence-based real-time assays and video microscopy, confocal and electron microscopy in combination with enzymatic assays for ROS production, routine biochemistry, immunology and cell biology.

Implementing these studies will require isolation of phagocytic leukocytes from venous blood of healthy human volunteers. The study population will be all-inclusive except in certain instances where individuals possess genetic defects that impair phagocyte function (e.g., myeloperoxidase-deficiency) or have altered phagocyte function due to outside influences such as recent bacterial or viral infection.

The proposed studies will likely provide new information pertinent to understanding host cell-pathogen interactions and the pathophysiology of inflammatory conditions.

Study Overview

• Status: Recruiting
• Conditions: Host Defense Mechanisms

Detailed Description

Human phagocytic cells such as polymorphonuclear leukocytes (neutrophils or PMNs) are readily mobilized to sites of infection and ingest microorganisms by a process known as phagocytosis. The combined effects of reactive oxygen species (ROS) and antimicrobial peptides released into forming bacterial phagosomes kill most ingested bacteria. However, many bacterial pathogens have devised means to evade normal phagocyte responses and cause severe disease in humans.

The overall objective of this study is to elucidate specific features of pathogen-phagocyte interactions that underlie evasion of the innate immune response or contribute to the pathophysiology of disease or inflammatory disorders. Therefore, projects will address 3 specific aims:

1. Identify and characterize specific mechanisms used by pathogenic microorganisms to evade or subvert normal phagocyte responses and therefore cause disease.
2. Investigate phagocyte response mechanisms to specific pathogenic microorganisms.
3. Identify specific bacterial structures and/or (gene) products that dictate differences in phagocyte responses among a range of pathogens so that generalized statements can be made about the pathophysiology of disease states.

The studies will be performed using multiple techniques including state-of-the-art equipment for genomics and proteomics strategies to identify target bacterial genes/proteins of interest or those up-regulated in phagocytes. Phagocyte-pathogen interactions will be examined using fluorescence-based real-time assays and video microscopy, confocal and electron microscopy in combination with enzymatic assays for ROS production, routine biochemistry, immunology and cell biology.

Implementing these studies will require isolation of phagocytic leukocytes from venous blood of healthy human volunteers. The study population will be all-inclusive except in certain instances where individuals possess genetic defects that impair phagocyte function (e.g., myeloperoxidase-deficiency) or have altered phagocyte function due to outside influences such as recent bacterial or viral infection.

The proposed studies will likely provide new information pertinent to understanding host cell-pathogen interactions and the pathophysiology of inflammatory conditions.

• Study Type: Observational
• Enrollment (Estimated): 200

Contacts and Locations

• Study Contact: Name: Frank R De Leo, Ph.D.; Phone Number: (406) 363-9448; Email: fdeleo@niaid.nih.gov

Study Locations

• United States
  • Montana
    • Hamilton, Montana, United States, 59840
      • Recruiting
      • NIAID, Rocky Mountain Laboratories

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Volunteers will be selected from a healthy adult population, 21-65 years of age, with no known medical problems and will generally be NIH employees working at Rocky Mountain Laboratories (RML) or within the community of Hamilton, MT. No race or gender is excluded from the donor pool and reflects the diversity of the community and that of the employees at RML.

Description

• INCLUSION & EXCLUSION CRITERIA:

Volunteers will be selected from a healthy adult population, 18 years of age or older, with no known medical problems and will generally be NIH employees working at Rocky Mountain Laboratories (RML) or within the community of Hamilton, MT.

No race or gender is excluded from the donor pool and reflects the diversity of the community and that of the employees at RML.

The specific criteria for eligibility are as follows:

• Subjects must fit the definition of "healthy adults" as assessed by the medical/health screening evaluations, and willing to have blood and/or tissue samples stored for future use.
• Inasmuch as all subjects are RML employees, they will be 18 years of age or older.
• Children are excluded.
• Pregnant women will be identified by verbal history and are not eligible to donate blood for this protocol.
• The study population will be all-inclusive except in certain instances where individuals possess genetic defects that impair phagocyte function (e.g., myeloperoxidase-deficiency) or have altered phagocyte function due to outside influences such as recent bacterial or viral infection.
• Individuals below the normal hematocrit and hemoglobin ranges will be excluded from the protocol.

Study Plan

How is the study designed?

Design Details

• Observational Models: Other
• Time Perspectives: Other

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Healthy volunteers; Healthy adult volunteers at least 18 years of age.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
identify and characterize specific mechanisms used by pathogenic microorganisms to evade or subvert normal phagocyte responses and therefore cause disease.	The study involves the use of human subjects as a source of blood for in vitro assays with bacteria, the isolation of hematopoietic cells (polymorphonuclear leukocytes, mononuclear phagocytes, erythrocytes, and lymphocytes), and serum as a source of complement, antibody, and matrix-binding proteins.	Ongoing

Collaborators and Investigators

• Sponsor: National Institute of Allergy and Infectious Diseases (NIAID)
• Investigators: Principal Investigator: Frank R De Leo, Ph.D., National Institute of Allergy and Infectious Diseases (NIAID)

Publications and helpful links

General Publications

• Rungelrath V, DeLeo FR. Staphylococcus aureus, Antibiotic Resistance, and the Interaction with Human Neutrophils. Antioxid Redox Signal. 2021 Feb 20;34(6):452-470. doi: 10.1089/ars.2020.8127. Epub 2020 Jun 23.
• Kobayashi SD, Malachowa N, DeLeo FR. Neutrophils and Bacterial Immune Evasion. J Innate Immun. 2018;10(5-6):432-441. doi: 10.1159/000487756. Epub 2018 Apr 11.

Study record dates

Study Major Dates

• Study Start (Actual): February 12, 2001

Study Registration Dates

• First Submitted: June 19, 2006
• First Submitted That Met QC Criteria: June 19, 2006
• First Posted (Estimated): June 21, 2006

Study Record Updates

• Last Update Posted (Actual): April 18, 2024
• Last Update Submitted That Met QC Criteria: April 17, 2024
• Last Verified: September 15, 2023

More Information

Terms related to this study

• Keywords: Natural History; Pathogenesis; Neutrophil; Virulence; PHAGOCYTOSIS
• Other Study ID Numbers: 999901055; 01-I-N055

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No