When Mycobacterium tuberculosis (M. tb) infection occurs by airborne transmission, bacilli are deposited in the alveolar spaces of the lungs. The traditional view is that M. tb is somewhat """"""""static"""""""" during initial infection, does not induce an immune response, and it is taken up by non-activated alveolar macrophages (AMs) that serve as an important reservoir for infection. However, we hypothesize that upon deposition in the alveolar space M. tb enters a dynamic phase where it encounters pulmonary surfactant that contains homeostatic and antimicrobial enzymes (hydrolases) which alter the M. tb cell wall. These hydrolases release biologically active M. tb fragments into the local milieu and stimulate a variety of lung cells within the alveoli that changes the pulmonary microenvironment, and thus the outcome of infection. We recently published that hydrolases present in the human lung surfactant dramatically alter the cell envelope of M. tb during infection releasing cell wall fragments into the lung milieu. As a result of these M. tb cell wall modifications, bacilli had a significant decrease in association with human macrophages followed by an increase in phagosome-lysosome fusion, which translated to a significant decrease in M. tb intracellular survival within these cells and an increase in inflammatory cytokine production leading to better control of infection. In addition to remodeling of the M. tb cell wall by host lung hydrolases, we hypothesize that M. tb cell wall fragments released in response to human lung surfactant hydrolases will influence the infection outcome. Our preliminary data show that released M. tb cell wall fragments generated upon contact with lung surfactant hydrolases are capable of activating primary human alveolar compartment cells. Moreover, human macrophages exposed to these fragments are better able to control M. tb infection. These findings add a new concept to the contribution of the lung environment to M. tb-host interactions at different stages of infection such as at the initial stage of infection;following release from lysed macrophages;and when M. tb is found extracellularly within lung cavities. In all of these stages, M. tb is in intimte contact with extracellular host secretions containing hydrolases that will alter its cell wall and release fragments. To address our hypothesis we propose to: i) Determine the structure of M. tb cell wall fragments released following exposure to the human alveolar hydrolases;ii) Determine how M. tb cell wall modifications and released cell wall fragments generated by surfactant hydrolases influence the establishment of M. tb infection in vitro using human primary alveolar compartment cells;and iii) Determine how M. tb cell wall modifications and released cell wall fragments generated by surfactant hydrolases influence the course of M. tb infection in vivo. This application is innovative and unique in examining an important and little known relationship between lung surfactant and M. tb infection and challenges our existing knowledge of host-pathogen interactions that have been elucidated in vitro. The role of the lung environment that M. tb encounters during infection is understudied and very little is known about its contribution t M. tb pathogenesis.

Public Health Relevance

One third of the world is infected with Mycobacterium tuberculosis (M. tb) killing one person worldwide every 14 seconds. This application will determine how mucosal degradative enzymes of the human lung surfactant alter the cell wall of M. tb influencing the immune response of the host and impacting the course of M. tb infection.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Host Interactions with Bacterial Pathogens Study Section (HIBP)
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Lacourciere, Karen A
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Ohio State University
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Moliva, J I; Hossfeld, A P; Canan, C H et al. (2018) Exposure to human alveolar lining fluid enhances Mycobacterium bovis BCG vaccine efficacy against Mycobacterium tuberculosis infection in a CD8+ T-cell-dependent manner. Mucosal Immunol 11:968-978
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Scordo, Julia M; Arcos, Jesús; Kelley, Holden V et al. (2017) Mycobacterium tuberculosis Cell Wall Fragments Released upon Bacterial Contact with the Human Lung Mucosa Alter the Neutrophil Response to Infection. Front Immunol 8:307
Torrelles, Jordi B; Schlesinger, Larry S (2017) Integrating Lung Physiology, Immunology, and Tuberculosis. Trends Microbiol 25:688-697
Arcos, J; Sasindran, S J; Moliva, J I et al. (2017) Mycobacterium tuberculosis cell wall released fragments by the action of the human lung mucosa modulate macrophages to control infection in an IL-10-dependent manner. Mucosal Immunol 10:1248-1258
Moliva, Juan I; Turner, Joanne; Torrelles, Jordi B (2017) Immune Responses to Bacillus Calmette-Guérin Vaccination: Why Do They Fail to Protect against Mycobacterium tuberculosis? Front Immunol 8:407
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Scordo, Julia M; Knoell, Daren L; Torrelles, Jordi B (2016) Alveolar Epithelial Cells in Mycobacterium tuberculosis Infection: Active Players or Innocent Bystanders? J Innate Immun 8:3-14
Pina-Mimbela, Ruby; Madrid, Jesús Arcos; Kumar, Anand et al. (2015) Polyphosphate kinases modulate Campylobacter jejuni outer membrane constituents and alter its capacity to invade and survive in intestinal epithelial cells in vitro. Emerg Microbes Infect 4:e77
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