Air Pollution Particulate Matter Effects on Adaptive Human Antimycobacterial ImmunityEPA Grant Number: FP917826
Title: Air Pollution Particulate Matter Effects on Adaptive Human Antimycobacterial Immunity
Investigators: Ibironke, Olufunmilola Adeboye
Institution: Rutgers, The State University of New Jersey
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2015 through August 31, 2018
Project Amount: $132,000
RFA: STAR Graduate Fellowships (2015) RFA Text | Recipients Lists
Research Category: Academic Fellowships
Urban air pollution poses serious threats to global public health as increasing evidence from epidemiological studies shows strong associations between exposure to particulate matter (PM), a key component of ambient air pollution, and adverse health effects including tuberculosis. PM come from combustion sources such as from vehicles and industrial processes, forest fires, road dust and windblown soil and exposure to PM2.5 (particles < 2.5mm in diameter) that is able to penetrate deeply into the lungs is estimated to cause ~1% of mortality from acute respiratory infections in children under 5 years globally. This research will assess if PM2.5 exposure alters T cell-mediated responses to Mycobacterium tuberculosis (M.tb), the causative agent of tuberculosis and thus how PM-mediated alterations of human adaptive immunity may contribute to inefficient control of M.tb.
I will use seasonal bulk samples of ambient particulate matter (PM2.5) collected in Iztapalapa, a densely populated municipality of Mexico City known for its high pollution levels, for this research. To examine the effect of air pollution PM on functional ability of T cells to lyse infected phagocytes and to directly kill intracellular bacteria, peripheral blood mononuclear cells (PBMC) will be isolated from heparinized blood of healthy Interferon Gamma Release Assay (IGRA) positive and negative human donors and monocyte-derived macrophages (MDM) will be generated. MDMs will be exposed to PM2.5 followed by stimulation with Mycobacterium tuberculosis (M.tb) and co- incubated with isolated autologous CD8+ T cells. On varying days of incubation, co-cultured cells will be fixed, permeabilized by cytofix/cytoperm solution, stained with monoclonal antibody specific for human perforin and then analyzed by flow cytometry. A portion of the co-cultured cells will be subjected to Granzyme B (grB) ELISPOT assays to measure the frequencies of grB-secreting cells directly. Data evaluation will be done by ImmunoSpot Imaging Analyzer systems, Cellular Tech Ltd. Decreased production of granzymes and perforins upon PM exposure will indicate decrease killing of M.tb. To investigate the underlying mechanisms of altered IFN-γ expression upon PM exposure observed during my preliminary studies, I will examine the expression of relevant transcription factors involved in the expression of IFN-γ. Cell extracts will be prepared from M.tb-infected PBMC stimulated with or without PM2.5 and analyzed by SDS PAGE. Western blotting using specific antibodies will be used to determine whether PM reduces the level of expression of T-bet, (known to directly activate expression of IFN-γ) and signal transducer and activator of transcription (STAT) 1 and 4. I will also examine their mRNA levels by real time (RT)-PCR and employ the use of anti-phospho antibodies to examine STAT6 and GATA3 mRNA and protein expression in these extracts upon PM exposure.
Air pollution PM2.5-induced alterations of adaptive antimycobacterial immune responses may confer a major risk of loss of immunological control over Mycobacterium tuberculosis (M.tb) infection. As such, understanding the molecular mechanisms of air pollution effects on human adaptive immunity to M.tb is crucial. This research will study the effects of “real world” urban PM2.5 (collected from Mexico City, highly polluted city) on adaptive anti-M.tb immune responses in M.tb-infected peripheral blood mononuclear cells (PBMC) from healthy Interferon Gamma Release Assay (IGRA) positive and negative human donors. This assay has been approved by US FDA for diagnosis of M.tb infection. PM exposure is expected to decrease the ability of human T cells to control M.tb infection which may indicate suppression of adaptive antimycobacterial immunity as protective immunity to M.tb has been ascribed to T cell-mediated immunity. PM-induced alteration of M.tb-specific T cell function would affect the efficacy of tuberculosis (TB) vaccine and have implications for most infectious diseases vaccine development as currently used TB vaccine candidates in clinical trials and vaccines of most infectious diseases are designed to induce T-cell mediated immune responses. Given the wide geographical scales for both air pollution and M.tb infections, new knowledge to be gained from this study will have significant global health implications. Expected results will provide unique information needed to prompt urgent implementation of interventions necessary to control urban air pollution that contributes to the development and progression of various diseases.