Publications

2011

Sow, Fatoumata B, Subhadra Nandakumar, Vijayakumar Velu, Kathryn L Kellar, Larry S Schlesinger, Rama R Amara, William P Lafuse, Thomas M Shinnick, and Suraj B Sable. (2011) 2011. “Mycobacterium Tuberculosis Components Stimulate Production of the Antimicrobial Peptide Hepcidin.”. Tuberculosis (Edinburgh, Scotland) 91 (4): 314-21. https://doi.org/10.1016/j.tube.2011.03.003.

We investigated the in vitro production of the antimicrobial peptide hepcidin by cells of the innate immune system that harbor Mycobacterium tuberculosis. Stimulation of mouse lung macrophages with M. tuberculosis or IFN-γ + M. tuberculosis induced hepcidin mRNA. In human alveolar A549 epithelial cells, lipoglycans of M. tuberculosis, in particular mannose-capped lipoarabinomannan and phosphatidyl-myo-inositol mannosides, were strong inducers of hepcidin mRNA. In mouse dendritic cells, hepcidin mRNA was increased by subcellular fractions and culture filtrate proteins of M. tuberculosis and by TLR2 and TLR4 agonists, but not by TLR9 agonists, IL-1α, IL-6 or TNF-α. Flow cytometry evaluation of human peripheral blood mononuclear cells demonstrated that CD11c(+) myeloid dendritic cells stimulated with killed M. tuberculosis or live M. bovis BCG produced hepcidin. The production of the antimicrobial peptide hepcidin by cells that interact with M. tuberculosis suggests a host defense mechanism against mycobacteria.

Day, Judy, Avner Friedman, and Larry S Schlesinger. (2011) 2011. “Modeling the Host Response to Inhalation Anthrax.”. Journal of Theoretical Biology 276 (1): 199-208. https://doi.org/10.1016/j.jtbi.2011.01.054.

Inhalation anthrax, an often fatal infection, is initiated by endospores of the bacterium Bacillus anthracis, which are introduced into the lung. To better understand the pathogenesis of an inhalation anthrax infection, we propose a two-compartment mathematical model that takes into account the documented early events of such an infection. Anthrax spores, once inhaled, are readily taken up by alveolar phagocytes, which then migrate rather quickly out of the lung and into the thoracic/mediastinal lymph nodes. En route, these spores germinate to become vegetative bacteria. In the lymph nodes, the bacteria kill the host cells and are released into the extracellular environment where they can be disseminated into the blood stream and grow to a very high level, often resulting in the death of the infected person. Using this framework as the basis of our model, we explore the probability of survival of an infected individual. This is dependent on several factors, such as the rate of migration and germination events and treatment with antibiotics.

2010

Wang, Shu-Hua, Dwight A Powell, Haikady N Nagaraja, Jessica D Morris, Larry S Schlesinger, and Joanne Turner. (2010) 2010. “Evaluation of a Modified Interferon-Gamma Release Assay for the Diagnosis of Latent Tuberculosis Infection in Adult and Paediatric Populations That Enables Delayed Processing.”. Scandinavian Journal of Infectious Diseases 42 (11-12): 845-50. https://doi.org/10.3109/00365548.2010.498021.

The objective of the study was to evaluate the specificity of a modified interferon-gamma release assay (IGRA) procedure that allows storage of blood samples for up to 32 h before processing. A total of 116 subjects were enrolled in the study. Two blood samples were collected from each volunteer; 1 specimen was processed within 8 h and analyzed using the T-SPOT®.TB test and the second specimen was stored overnight and processed 23-32 h later after addition of the T-Cell Xtend™ reagent and then analyzed using the T-SPOT.TB test. A total of 108 paired T-SPOT.TB and T-SPOT.TB plus T-Cell Xtend tests were analyzed on specimens from 97 adults and 11 children. The median age of the subjects was 28 y with 68.5% female and 78.7% white. The overall agreement between the 2 tests was 98.2% (106/108). The specificity of the T-SPOT.TB test was 99.1% (107/108) and for T-SPOT.TB plus T-Cell Xtend was 97.2%. The 2 tests were comparable in results. Increasing storage time of the collected blood specimen prior to processing provides flexibility for clinicians and laboratories. Additional studies in larger and diverse patient populations including immunocompromised and paediatric patients, and patients with active TB disease or latent tuberculosis infection are needed.

Rajaram, Murugesan S, V, Michelle N Brooks, Jessica D Morris, Jordi B Torrelles, Abul K Azad, and Larry S Schlesinger. (2010) 2010. “Mycobacterium Tuberculosis Activates Human Macrophage Peroxisome Proliferator-Activated Receptor Gamma Linking Mannose Receptor Recognition to Regulation of Immune Responses.”. Journal of Immunology (Baltimore, Md. : 1950) 185 (2): 929-42. https://doi.org/10.4049/jimmunol.1000866.

Mycobacterium tuberculosis enhances its survival in macrophages by suppressing immune responses in part through its complex cell wall structures. Peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear receptor superfamily member, is a transcriptional factor that regulates inflammation and has high expression in alternatively activated alveolar macrophages and macrophage-derived foam cells, both cell types relevant to tuberculosis pathogenesis. In this study, we show that virulent M. tuberculosis and its cell wall mannose-capped lipoarabinomannan induce PPARgamma expression through a macrophage mannose receptor-dependent pathway. When activated, PPARgamma promotes IL-8 and cyclooxygenase 2 expression, a process modulated by a PPARgamma agonist or antagonist. Upstream, MAPK-p38 mediates cytosolic phospholipase A(2) activation, which is required for PPARgamma ligand production. The induced IL-8 response mediated by mannose-capped lipoarabinomannan and the mannose receptor is independent of TLR2 and NF-kappaB activation. In contrast, the attenuated Mycobacterium bovis bacillus Calmette-Guérin induces less PPARgamma and preferentially uses the NF-kappaB-mediated pathway to induce IL-8 production. Finally, PPARgamma knockdown in human macrophages enhances TNF production and controls the intracellular growth of M. tuberculosis. These data identify a new molecular pathway that links engagement of the mannose receptor, an important pattern recognition receptor for M. tuberculosis, with PPARgamma activation, which regulates the macrophage inflammatory response, thereby playing a role in tuberculosis pathogenesis.

Sweet, Lindsay, Prachi P Singh, Abul K Azad, Murugesan S Rajaram V, Larry S Schlesinger, and Jeffrey S Schorey. (2010) 2010. “Mannose Receptor-Dependent Delay in Phagosome Maturation by Mycobacterium Avium Glycopeptidolipids.”. Infection and Immunity 78 (1): 518-26. https://doi.org/10.1128/IAI.00257-09.

The ability of pathogenic mycobacteria to block phagosome-lysosome fusion is critical for its pathogenesis. The molecules expressed by mycobacteria that inhibit phagosome maturation and the mechanism of this inhibition have been extensively studied. Recent work has indicated that mannosylated lipoarabinomannan (ManLAM) isolated from Mycobacterium tuberculosis can function to delay phagosome-lysosome fusion and that this delay requires the interaction of ManLAM with the mannose receptor (MR). However, the molecules expressed by other pathogenic mycobacteria that function to inhibit phagosome maturation have not been well described. In the present study, we show that phagosomes containing silica beads coated with glycopeptidolipids (GPLs), a major surface component of Mycobacterium avium, showed limited acidification and delayed recruitment of late endosomal/lysosomal markers compared to those of phosphatidylcholine-coated beads. The carbohydrate component of the GPLs was required, as beads coated only with the lipopeptide core failed to delay phagosome-lysosome fusion. Moreover, the ability of GPLs to delay phagosome maturation was dependent on the macrophage expression of the MR. Using CHO cells expressing the MR, we confirmed that the GPLs bind this receptor. Finally, human monocyte-derived macrophages knocked down for MR expression showed increased M. avium phagosome-lysosome fusion relative to control cells. Together, the data indicate that GPLs can function to delay phagosome-lysosome fusion and suggest that GPLs, like ManLAM, work through the MR to mediate this activity.

Day, Judy, Larry S Schlesinger, and Avner Friedman. (2010) 2010. “Tuberculosis Research: Going Forward With a Powerful ‘translational Systems Biology’ Approach.”. Tuberculosis (Edinburgh, Scotland) 90 (1): 7-8. https://doi.org/10.1016/j.tube.2009.12.002.

Due to the complexity of the immune response to a Mycobacterium tuberculosis infection, identifying new, effective therapies and vaccines to combat it has been a problematic issue. Although many advances have been made in understanding particular mechanisms involved, they have, to date, proved insufficient to provide real breakthroughs in this area of tuberculosis research. The term "Translational Systems Biology" has been formally proposed to describe the use of experimental findings combined with mathematical modeling and/or engineering principles to understand complex biological processes in an integrative fashion for the purpose of enhancing clinical practice. This opinion piece discusses the importance of using a Translational Systems Biology approach for tuberculosis research as a means by which to go forward with the potential for significant breakthroughs to occur.

Mohapatra, Nrusingh P, Shilpa Soni, Murugesan S Rajaram V, Pham My-Chan Dang, Tom J Reilly, Jamel El-Benna, Corey D Clay, Larry S Schlesinger, and John S Gunn. (2010) 2010. “Francisella Acid Phosphatases Inactivate the NADPH Oxidase in Human Phagocytes.”. Journal of Immunology (Baltimore, Md. : 1950) 184 (9): 5141-50. https://doi.org/10.4049/jimmunol.0903413.

Francisella tularensis contains four putative acid phosphatases that are conserved in Francisella novicida. An F. novicida quadruple mutant (AcpA, AcpB, AcpC, and Hap [DeltaABCH]) is unable to escape the phagosome or survive in macrophages and is attenuated in the mouse model. We explored whether reduced survival of the DeltaABCH mutant within phagocytes is related to the oxidative response by human neutrophils and macrophages. F. novicida and F. tularensis subspecies failed to stimulate reactive oxygen species production in the phagocytes, whereas the F. novicida DeltaABCH strain stimulated a significant level of reactive oxygen species. The DeltaABCH mutant, but not the wild-type strain, strongly colocalized with p47(phox) and replicated in phagocytes only in the presence of an NADPH oxidase inhibitor or within macrophages isolated from p47(phox) knockout mice. Finally, purified AcpA strongly dephosphorylated p47(phox) and p40(phox), but not p67(phox), in vitro. Thus, Francisella acid phosphatases play a major role in intramacrophage survival and virulence by regulating the generation of the oxidative burst in human phagocytes.

Dai, Shipan, Nrusingh P Mohapatra, Larry S Schlesinger, and John S Gunn. (2010) 2010. “Regulation of Francisella Tularensis Virulence.”. Frontiers in Microbiology 1: 144. https://doi.org/10.3389/fmicb.2010.00144.

Francisella tularensis is one of the most virulent bacteria known and a Centers for Disease Control and Prevention Category A select agent. It is able to infect a variety of animals and insects and can persist in the environment, thus Francisella spp. must be able to survive in diverse environmental niches. However, F. tularensis has a surprising dearth of sensory and regulatory factors. Recent advancements in the field have identified new functions of encoded transcription factors and greatly expanded our understanding of virulence gene regulation. Here we review the current knowledge of environmental adaptation by F. tularensis, its transcriptional regulators and their relationship to animal virulence.

Torrelles, Jordi B, and Larry S Schlesinger. (2010) 2010. “Diversity in Mycobacterium Tuberculosis Mannosylated Cell Wall Determinants Impacts Adaptation to the Host.”. Tuberculosis (Edinburgh, Scotland) 90 (2): 84-93. https://doi.org/10.1016/j.tube.2010.02.003.

Mycobacterium tuberculosis (the causal agent of TB) has co-evolved with humans for centuries. It infects via the airborne route and is a prototypic highly adapted intracellular pathogen of macrophages. Extensive sequencing of the M. tuberculosis genome along with recent molecular phylogenetic studies is enabling us to gain insight into the biologic diversity that exists among bacterial strains that impact the pathogenesis of latent infection and disease. The majority of the M. tuberculosis cell envelope is comprised of carbohydrates and lipids, and there is increasing evidence that these microbial determinants that are readily exposed to the host immune system play critical roles in disease pathogenesis. Studies from our laboratory and others have raised the possibility that M. tuberculosis is adapting to the human host by cloaking its cell envelope molecules with terminal mannosylated (i.e. Man-alpha-(1–>2)-Man) oligosaccharides that resemble the glycoforms of mammalian mannoproteins. These mannosylated biomolecules engage the mannose receptor (MR) on macrophages during phagocytosis and dictate the intracellular fate of M. tuberculosis by regulating formation of the unique vesicular compartment in which the bacterium survives. The MR is highly expressed on alveolar macrophages (predominant C-type lectin on human cells) and functions as a scavenger receptor to maintain the healthiness of the lung by clearing foreign particles and at the same time regulating dangerous inflammatory responses. Thus M. tuberculosis exploits MR functions to gain entry into the macrophage and survive. Key biochemical pathways and mycobacterial determinants involved in the development and maintenance of the M. tuberculosis phagosome are being identified. The phylogenetic diversity observed in M. tuberculosis strains that impact its cell wall structure together with the genetic diversity observed in human populations, including those elements that affect macrophage function, may help to explain the extraordinary evolutionary adaptation of this pathogen to the human host. Major developments in these areas are the focus of this review.

2009

Wang, Shu-Hua, Preeti Pancholi, Kurt Stevenson, Mitchell A Yakrus, Ray Butler, Larry S Schlesinger, and Julie E Mangino. (2009) 2009. “Pseudo-Outbreak of ‘Mycobacterium Paraffinicum’ Infection and/Or Colonization in a Tertiary Care Medical Center.”. Infection Control and Hospital Epidemiology 30 (9): 848-53. https://doi.org/10.1086/599071.

OBJECTIVE: To investigate a pseudo-outbreak of "Mycobacterium paraffinicum" (unofficial taxon) infection and/or colonization, using isolates recovered from clinical and environmental specimens.

DESIGN: Outbreak investigation.

SETTING: University-affiliated, tertiary-care hospital.

METHODS: M. paraffinicum, a slow-growing, nontuberculous species of mycobacteria, was recovered from 21 patients and an ice machine on a single patient care unit over a 2.5-year period. The clinical, epidemiological, and environmental investigation of this pseudo-outbreak is described.

RESULTS: Twenty-one patients with pulmonary symptoms and possible risk factors for tuberculosis were admitted to inpatient rooms that provided airborne isolation conditions in 2 adjacent hospital buildings. In addition, 1 outpatient had induced sputum cultured for mycobacteria in the pulmonary function laboratory. Of the samples obtained from these 21 patients, 26 isolates from respiratory samples and 1 isolate from a stool sample were identified as M. paraffinicum. Environmental isolates obtained from an ice machine in the patient care unit where the majority of the patients were admitted were also identified as M. paraffinicum.

CONCLUSIONS: An epidemiological investigation that used molecular tools confirmed the suspicion of a pseudo-outbreak of M. paraffinicum infection and/or colonization. The hospital water system was identified as the source of contamination.