Clinical Research Directory

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.

Host Response to Infection by Direct Analysis of Leukocyte Single Cell-type Gene Expression/transcript Abundance, Direct LS-TA. a Prospective Study Will Evaluate the Performance of Direct LS-TA in Triage Febrile Patients Into Major Categories of Infections: Viral, Bacterial or Active Tuberculosis.

Febrile illness is a common condition and it is crucial to have an early triage of patients according to various aetiologies to enable appropriate treatment. Currently, most screening/diagnostic tests target the detection of pathogens, while only a few assays aim to understand the host response, and they are mostly based on a measurement of serum proteins (e.g. CRP or procalcitonin). Recently, blood transcriptome has been explored to differentiate bacterial and viral infections. However, gene expression in blood represents a composite score of gene expression of all the component cell-types present in the sample. Here, we propose to develop a rapid test that can determine gene expressions of a specified single cell type in peripheral blood (e.g., monocytes or granulocytes) as a host response biomarker to differentiate three major categories of infections that are bacterial, viral, and tuberculosis The assay is called Direct Leukocyte Single cell-type transcript abundance (TA) assay (DIRECT LS-TA) as it can directly determine the gene expression of a specified single cell-type among various other leukocyte populations directly in a peripheral blood sample. Such results signify the nature of host response according to 3 or more axes (Type I or Type II interferon signaling response or pro-inflammatory cytokine signaling) And it can be used to indicate the type of underlying infection (viral, bacterial, or active tuberculosis).