Ultra-low Dose Aerosol Infection of Mice with Mycobacterium tuberculosis More Closely Models Human Tuberculosis

Secondary sigma factors in bacteria direct transcription of defence regulons in response to specific stresses. To identify which sigma factors in the human respiratory pathogen Mycobacterium tuberculosis are important for adaptive survival in vivo, defined null mutations were created in individual sigma factor genes. In this study, in vitro growth virulence and guinea pig pathology of M. tuberculosis mutants lacking functional sigma factors (SigC, SigF, or SigM) were compared to the parent strain, H37Rv. None of the mutant strains exhibited a growth deficiency in Middlebrook 7H9 broth, nor were any impaired for intracellular replication in the human monocytic macrophage cell-line THP-1. Following low-dose aerosol infection of guinea pigs, however, differences could be detected. While a SigM mutant resulted in lung and spleen granulomas of comparable composition to those found in H37Rv-infected animals, a SigF mutant was partially attenuated, exhibiting necrotic spleen granulomas and ill-defined lung granulomas. SigC mutants exhibited attenuation in the lung and spleen; notably, necrotic granulomas were absent. These data suggest that while SigF may be important for survival in the lung, SigC is likely a key regulator of pathogenesis and adaptive survival in the lung and spleen. Understanding how SigC mediates survival in the host should prove useful in the development of anti-tuberculosis therapies.

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Immunological Basis for Reactivation of Tuberculosis in Mice

Infection and Immunity ◽

10.1128/iai.69.5.3264-3270.2001 ◽

2001 ◽

Vol 69 (5) ◽

pp. 3264-3270 ◽

Cited By ~ 47

Author(s):

J. Turner ◽

M. Gonzalez-Juarrero ◽

B. M. Saunders ◽

J. V. Brooks ◽

P. Marietta ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Bacterial Growth ◽

Chronic Infection ◽

Low Dose ◽

Inbred Strains ◽

Lymphocyte Response ◽

Inbred Strains Of Mice ◽

Show Evidence ◽

Circulating Lymphocytes ◽

Aerosol Infection

ABSTRACT In this study different inbred strains of mice appeared to control and contain a low dose aerosol infection with Mycobacterium tuberculosis in a similar manner, giving rise to a chronic state of disease. Thereafter, however, certain strains gradually began to show evidence of regrowth of the infection, whereas others consistently did not. Using C57BL/6 mice as an example of a resistant strain and CBA/J mice as an example of a strain susceptible to bacterial growth, we found that these animals revealed distinct differences in the cellular makeup of lung granulomas. The CBA/J mice exhibited a generally poor lymphocyte response within the lungs and vastly increased degenerative pathology at a time associated with regrowth of the infection. As a possible explanation for these events, it was then observed that the CBA/J mouse strain was also less able to upregulate adhesion molecules, including CD11a and CD54, on circulating lymphocytes. These results therefore suggest that a failure to control a chronic infection with M. tuberculosis may reflect an inability to localize antigen-specific lymphocytes within the lung.

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Low-dose aerosol infection model for testing drugs for efficacy against Mycobacterium tuberculosis.

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.40.12.2809 ◽

1996 ◽

Vol 40 (12) ◽

pp. 2809-2812 ◽

Cited By ~ 76

Author(s):

B P Kelly ◽

S K Furney ◽

M T Jessen ◽

I M Orme

Keyword(s):

Mycobacterium Tuberculosis ◽

Low Dose ◽

Bacterial Load ◽

Lung Model ◽

Exposure Model ◽

Infection Model ◽

High Dose ◽

Level Of Activity ◽

Days Of Therapy ◽

Aerosol Infection

As a paradigm for chronic infectious diseases, tuberculosis exhibits a variety of clinical presentations, ranging from primary pulmonary tuberculosis to reactivation tuberculosis and cavitary disease. To date, the animal models used in evaluating chemotherapy of tuberculosis have been high-dose intravenous models that mimic the disseminated forms of the disease. In the present study, we have used a low-dose aerosol exposure model which we feel better reflects newly diagnosed tuberculosis in patients converting to tuberculin positivity. As appropriate examples of chemotherapy, four rifamycins (rifampin, rifabutin, rifapentine, and KRM-1648) were tested, first in an in vitro murine macrophage model and then in the low-dose aerosol infection model, for their activity against Mycobacterium tuberculosis. In both models, KRM-1648 had the highest level of activity of the four compounds. In the infected-lung model, rifabutin, rifapentine, and KRM-1648 all had sterilizing activity when given orally at 5 mg/kg of body weight per day. When given at 2.5 mg/kg/day, KRM-1648 had the highest level of activity of the four drugs, reducing the bacterial load by 2.7 logs over 35 days of therapy.

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The Purinergic P2X7 Receptor Is Not Required for Control of Pulmonary Mycobacterium tuberculosis Infection

Infection and Immunity ◽

10.1128/iai.73.5.3192-3195.2005 ◽

2005 ◽

Vol 73 (5) ◽

pp. 3192-3195 ◽

Cited By ~ 22

Author(s):

Amy J. Myers ◽

Brandon Eilertson ◽

Scott A. Fulton ◽

JoAnne L. Flynn ◽

David H. Canaday

Keyword(s):

Mycobacterium Tuberculosis ◽

Mouse Model ◽

P2x7 Receptor ◽

Low Dose ◽

Wild Type ◽

Mycobacterium Tuberculosis Infection ◽

P2x7 Receptors ◽

Purinergic P2x7 Receptor ◽

Aerosol Infection

ABSTRACT The importance in vivo of P2X7 receptors in control of virulent Mycobacterium tuberculosis was examined in a low-dose aerosol infection mouse model. P2X7−/− mice controlled infection in lungs as well as wild-type mice, suggesting that the P2X7 receptor is not required for control of pulmonary M. tuberculosis infection.

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Evaluation of Once-Weekly Therapy for Tuberculosis Using Isoniazid plus Rifamycins in the Mouse Aerosol Infection Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.42.11.3047 ◽

1998 ◽

Vol 42 (11) ◽

pp. 3047-3048 ◽

Cited By ~ 16

Author(s):

Jason V. Brooks ◽

Ian M. Orme

Keyword(s):

Animal Model ◽

Mycobacterium Tuberculosis ◽

Low Dose ◽

Infection Model ◽

Model Data ◽

Highly Effective ◽

Clinical Conditions ◽

Aerosol Infection ◽

Weekly Therapy

ABSTRACT Once-weekly therapy with combinations of isoniazid plus a rifamycin was tested in the mouse low-dose aerosol infection model against two strains of Mycobacterium tuberculosis. Combinations of isoniazid and rifalizil and isoniazid and rifapentine were both highly effective. These animal model data thus support the evaluation of these regimens under clinical conditions.

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SWR Mice Are Highly Susceptible to Pulmonary Infection with Mycobacterium tuberculosis

Infection and Immunity ◽

10.1128/iai.71.9.5266-5272.2003 ◽

2003 ◽

Vol 71 (9) ◽

pp. 5266-5272 ◽

Cited By ~ 25

Author(s):

Oliver C. Turner ◽

Robert G. Keefe ◽

Isamu Sugawara ◽

Hiroyuki Yamada ◽

Ian M. Orme

Keyword(s):

Mycobacterium Tuberculosis ◽

Low Dose ◽

Pulmonary Infection ◽

Inflammatory Cell ◽

Inbred Mice ◽

Bacterial Load ◽

Lower Percentage ◽

Effector Memory ◽

Aerosol Infection ◽

Lung Surface Area

ABSTRACT Inbred mice differ in their abilities to control the growth of Mycobacterium tuberculosis in the lung and can as a result be regarded as either resistant or susceptible strains. In this study we report that the SWR mouse is both highly susceptible and in addition appears incapable of establishing a characteristic state of chronic disease after low-dose aerosol infection. In comparison to C57BL/6 mice, SWR mice were unable to contain the bacterial load in the lungs, resulting in progressive fatal disease. Histologic analysis of the lung tissue revealed evidence of a florid inflammatory cell response in the SWR mice leading to degeneration and necrosis and consolidation of a large percentage of the lung surface area. Digestion of infected lungs and analysis by flow cytometry demonstrated an initially similar but eventually higher number of lymphocytes accumulating in the SWR mice. Additionally, in contrast to the C57BL/6 mice, SWR mice had a significantly lower percentage of CD4 T cells in the lungs showing evidence of proliferation and positive intracellular staining for gamma interferon during the first two months of infection, and a lower percentage of both CD4 and CD8T cells exhibiting differentiation to an effector/memory phenotype during the first month of infection. We propose that further investigation of the SWR mouse may provide a new animal model for immunocompetent individuals apparently unable to effectively control the growth of M. tuberculosis in the lung.

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Individual Mycobacterium tuberculosis Resuscitation-Promoting Factor Homologues Are Dispensable for Growth In Vitro and In Vivo

Infection and Immunity ◽

10.1128/iai.72.1.515-526.2004 ◽

2004 ◽

Vol 72 (1) ◽

pp. 515-526 ◽

Cited By ~ 84

Author(s):

JoAnn M. Tufariello ◽

William R. Jacobs, ◽

John Chan

Keyword(s):

Mycobacterium Tuberculosis ◽

Stationary Phase ◽

Essential Gene ◽

Micrococcus Luteus ◽

Expression Patterns ◽

Active Growth ◽

Prolonged Incubation ◽

Aerosol Infection

ABSTRACT Mycobacterium tuberculosis possesses five genes with significant homology to the resuscitation-promoting factor (Rpf) of Micrococcus luteus. The M. luteus Rpf is a secreted ∼16-kDa protein which restores active growth to cultures of M. luteus rendered dormant by prolonged incubation in stationary phase. More recently, the Rpf-like proteins of M. tuberculosis have been shown to stimulate the growth of extended-stationary-phase cultures of Mycobacterium bovis BCG. These data suggest that the Rpf proteins can influence the growth of mycobacteria; however, the studies do not demonstrate specific functions for the various members of this protein family, nor do they assess the function of M. tuberculosis Rpf homologues in vivo. To address these questions, we have disrupted each of the five rpf-like genes in M. tuberculosis Erdman, and analyzed the mutants for their growth in vitro and in vivo. In contrast to M. luteus, for which rpf is an essential gene, we find that all of the M. tuberculosis rpf deletion mutant strains are viable; in addition, all show growth kinetics similar to Erdman wild type both in vitro and in mouse organs following aerosol infection. Analysis of rpf expression in M. tuberculosis cultures from early log phase through late stationary phase indicates that expression of the rpf-like genes is growth phase-dependent, and that the expression patterns of the five M. tuberculosis rpf genes, while overlapping to various degrees, are not uniform. We also provide evidence that mycobacterial rpf genes are expressed in vivo in the lungs of mice acutely infected with virulent M. tuberculosis.

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Expression of the Nitric Oxide Synthase 2 Gene Is Not Essential for Early Control of Mycobacterium tuberculosis in the Murine Lung

Infection and Immunity ◽

10.1128/iai.68.12.6879-6882.2000 ◽

2000 ◽

Vol 68 (12) ◽

pp. 6879-6882 ◽

Cited By ~ 105

Author(s):

Andrea M. Cooper ◽

John E. Pearl ◽

Jason V. Brooks ◽

Stefan Ehlers ◽

Ian M. Orme

Keyword(s):

Nitric Oxide ◽

Mycobacterium Tuberculosis ◽

Nitric Oxide Synthase ◽

Low Dose ◽

Interleukin 12 ◽

Infection Model ◽

Rapid Progression ◽

Ifn Γ ◽

Nitric Oxide Synthase 2 ◽

Oxide Synthase

ABSTRACT The interleukin-12 and gamma interferon (IFN-γ) pathway of macrophage activation plays a pivotal role in controlling tuberculosis. In the murine model, the generation of supplementary nitric oxide by the induction of the nitric oxide synthase 2 (NOS2) gene product is considered the principal antimicrobial mechanism of IFN-γ-activated macrophages. Using a low-dose aerosol-mediated infection model in the mouse, we have investigated the role of nitric oxide in controllingMycobacterium tuberculosis in the lung. In contrast to the consequences of a systemic infection, a low dose of bacteria introduced directly into the lungs of mice lacking the NOS2 gene is controlled almost as well as in intact animals. This is in contrast to the rapid progression of disease in mice lacking IFN-γ or a key member of the IFN signaling pathway, interferon regulatory factor 1. Thus while IFN-γ is pivotal in early control of bacterial growth in the lung, this control does not completely depend upon the expression of the NOS2 gene. The absence of inducible nitric oxide in the lung does, however, result in increased polymorphonuclear cell involvement and eventual necrosis in the pulmonary granulomas of the infected mice lacking the NOS2 gene.

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Disparate Effects of Metformin on Mycobacterium tuberculosis Infection in Diabetic and Nondiabetic Mice

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01422-20 ◽

2020 ◽

Vol 65 (1) ◽

pp. e01422-20

Author(s):

Harindra D. Sathkumara ◽

Karyna Hansen ◽

Socorro Miranda-Hernandez ◽

Brenda Govan ◽

Catherine M. Rush ◽

...

Keyword(s):

Type 2 Diabetes ◽

Mycobacterium Tuberculosis ◽

Disease Burden ◽

Low Dose ◽

Diabetic Mice ◽

Antidiabetic Drug ◽

Mycobacterium Tuberculosis Infection ◽

Therapeutic Concentration ◽

Content Type

ABSTRACTComorbid type 2 diabetes poses a great challenge to the global control of tuberculosis. Here, we assessed the efficacy of metformin (MET), an antidiabetic drug, in mice infected with a very low dose of Mycobacterium tuberculosis. In contrast to diabetic mice, infected nondiabetic mice that received the same therapeutic concentration of MET presented with significantly higher disease burden. This warrants further studies to investigate the disparate efficacy of MET against tuberculosis in diabetic and nondiabetic individuals.

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Antimicrobial Peptide against Mycobacterium Tuberculosis That Activates Autophagy Is an Effective Treatment for Tuberculosis

Pharmaceutics ◽

10.3390/pharmaceutics12111071 ◽

2020 ◽

Vol 12 (11) ◽

pp. 1071

Author(s):

Erika A. Peláez Coyotl ◽

Jacqueline Barrios Palacios ◽

Gabriel Muciño ◽

Daniel Moreno-Blas ◽

Miguel Costas ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Antimicrobial Peptide ◽

Low Dose ◽

Antibiotic Activity ◽

Drug Resistant ◽

Mice Model ◽

Therapeutic Modalities ◽

Mdr Tb ◽

A Cell

Mycobacterium tuberculosis (MTB) is the principal cause of human tuberculosis (TB), which is a serious health problem worldwide. The development of innovative therapeutic modalities to treat TB is mainly due to the emergence of multi drug resistant (MDR) TB. Autophagy is a cell-host defense process. Previous studies have reported that autophagy-activating agents eliminate intracellular MDR MTB. Thus, combining a direct antibiotic activity against circulating bacteria with autophagy activation to eliminate bacteria residing inside cells could treat MDR TB. We show that the synthetic peptide, IP-1 (KFLNRFWHWLQLKPGQPMY), induced autophagy in HEK293T cells and macrophages at a low dose (10 μM), while increasing the dose (50 μM) induced cell death; IP-1 induced the secretion of TNFα in macrophages and killed Mtb at a dose where macrophages are not killed by IP-1. Moreover, IP-1 showed significant therapeutic activity in a mice model of progressive pulmonary TB. In terms of the mechanism of action, IP-1 sequesters ATP in vitro and inside living cells. Thus, IP-1 is the first antimicrobial peptide that eliminates MDR MTB infection by combining four activities: reducing ATP levels, bactericidal activity, autophagy activation, and TNFα secretion.

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