1204. Role of Macrophage Heme Oxygenase and its Product Carbon Monoxide in Human Tuberculosis
Session: Oral Abstract Session: Biomarkers of Infectious Diseases
Saturday, October 5, 2013: 9:18 AM
Room: The Moscone Center: 300
Background: Mycobacterium tuberculosis (Mtb) causes about two million deaths annually. We previously showed that Mtb infection of mice induces the production of the host enzyme heme oxygenase (HO1) within infected macrophages, and the subsequent production of carbon monoxide (CO) gas by HO1 is sensed by mycobacteria to initiate a dormancy program. Mouse macrophages deficient in heme oxygenase are defective in controlling intracellular Mtb infection and it was recently shown by others that mice deficient in heme oxygenase succumb to mycobacterial infection more readily than wild type mice. While the mechanisms used by mouse macrophages to control intracellular Mtb infection, including nitric oxide synthase, the respiratory burst, acidification and heme oxygenase are well studied, how human macrophages react to and control Mtb infection remains poorly understood.

Methods: We performed immunohistochemistry for HO1 on biopsy samples from tuberculosis cases. We used banked DNA from the Houston Tuberculosis Initiative to perform a case-control study on polymorphisms in the HO1 promoter from 138 individuals with active tuberculosis and 136 without active tuberculosis.  Both studies were approved by the IRB at the University of Texas Southwestern Medical Center. Human macrophages infected with Mtb were also subjected to confocal microscopy, multiplexed cytokine assays and intracellular CFU assays. To identify CO resistance genes, an Mtb transposon library was screened and mutants tested in vitro and in mice for CO susceptibility and attenuation.

Results: We show that HO1 is induced in human tuberculosis lesions, that Mtb infection of human macrophages in vitro induces HO1 and that a polymorphism in the HO1 promoter confers susceptibility to human tuberculosis. We also show by confocal microscopy that HO1 colocalizes with Mtb in human macrophages, and HO1 enzymatic activity in human macrophages is necessary for inflammatory cytokine production and intracellular survival. Finally, we demonstrate that Mtb encodes for a novel CO resistance gene that is essential for mycobacterial virulence in vivo.

Conclusion: We demonstrate an important new role for heme oxygenase derived carbon monoxide in controlling Mtb infection in humans.

Angela C. Collins, B.S.1, Vineetha Zacharia, B.S.1, Vidhya Nair, MD, MS1, Denise K. Marciano, MD, PhD1, Edward A. Graviss, PhD, MPH2 and Michael U. Shiloh, MD, PhD1, (1)Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, (2)The Methodist Hospital Research Institute, Houston, TX


A. C. Collins, None

V. Zacharia, None

V. Nair, None

D. K. Marciano, None

E. A. Graviss, None

M. U. Shiloh, None

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