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Kong Y, Cirillo JD. Fluorescence Imaging of Mycobacterial Infection in Live Mice Using Fluorescent Protein-Expressing Strains. Methods Mol Biol 2018; 1790:75-85. [PMID: 29858784 DOI: 10.1007/978-1-4939-7860-1_6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Fluorescence imaging has been applied to various areas of biological research, including studies of physiological, neurological, oncological, cell biological, molecular, developmental, immunological, and infectious processes. In this chapter, we describe methods of fluorescent imaging applied to examination of subcutaneous and pulmonary mycobacterial infections in an animal model. Since slow growth of Mycobacterium tuberculosis (Mtb) hinders development of new diagnostics, therapeutics, and vaccines for tuberculosis (TB), we developed fluorescent protein (FP) expressing mycobacterial strains for in vivo imaging, which can be used to track bacterial location and to quantitate bacterial load directly in living animals. After comparison of imaging data using strains expressing different fluorescent proteins, we found that strains expressing L5-tdTomato display the greatest fluorescence. Here, we describe detailed protocols for tdTomato-labeled M. bovis BCG imaging in real time for subcutaneous and pulmonary infections in living mice. These procedures allow rapid and accurate determination of bacterial numbers in live mice.
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Affiliation(s)
- Ying Kong
- Department of Microbiology, Immunology, and Biochemistry, University of Tennessee Health Science Center, Memphis, TN, USA.
| | - Jeffrey D Cirillo
- Department of Microbial Pathogenesis and Immunology, Texas A & M University Health Science Center, Bryan, TX, USA
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2
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Durkee MS, Nooshabadi F, Cirillo JD, Maitland KC. Optical model of the murine lung to optimize pulmonary illumination. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-12. [PMID: 29573254 PMCID: PMC8355613 DOI: 10.1117/1.jbo.23.7.071208] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 03/01/2018] [Indexed: 05/05/2023]
Abstract
We describe a Monte Carlo model of the mouse torso to optimize illumination of the mouse lung for fluorescence detection of low levels of pulmonary pathogens, specifically Mycobacterium tuberculosis. After validation of the simulation with an internally illuminated optical phantom, the entire mouse torso was simulated to compare external and internal illumination techniques. Measured optical properties of deflated mouse lungs were scaled to mimic the diffusive properties of inflated lungs in vivo. Using the full-torso model, a 2 × to 3 × improvement in average fluence rate in the lung was seen for dorsal compared with ventral positioning of the mouse with external illumination. The enhancement in average fluence rate in the lung using internal excitation was 40 × to 60 × over external illumination in the dorsal position. Parameters of the internal fiber optic source were manipulated in the model to guide optimization of the physical system and experimental protocol for internal illumination and whole-body detection of fluorescent mycobacteria in a mouse model of infection.
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Affiliation(s)
- Madeleine S. Durkee
- Texas A&M University, Department of Biomedical Engineering, College Station, Texas, United States
| | - Fatemeh Nooshabadi
- Texas A&M University, Department of Biomedical Engineering, College Station, Texas, United States
| | - Jeffrey D. Cirillo
- Texas A&M Health Science Center, Department of Molecular Pathogenesis and Immunology, Bryan, Texas, United States
| | - Kristen C. Maitland
- Texas A&M University, Department of Biomedical Engineering, College Station, Texas, United States
- Address all correspondence to: Kristen C. Maitland, E-mail:
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Yang HJ, Kong Y, Cheng Y, Janagama H, Hassounah H, Xie H, Rao J, Cirillo JD. Real-time Imaging of Mycobacterium tuberculosis, Using a Novel Near-Infrared Fluorescent Substrate. J Infect Dis 2017; 215:405-414. [PMID: 27421748 PMCID: PMC6061879 DOI: 10.1093/infdis/jiw298] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 07/06/2016] [Indexed: 11/14/2022] Open
Abstract
Slow growth of Mycobacterium tuberculosis, the causative agent of tuberculosis, hinders advancement in all areas of research toward prevention and treatment. Real-time imaging with reporter enzyme fluorescence (REF) that uses custom fluorogenic substrates for bacterial enzymes allows rapid and specific detection of M. tuberculosis in live animals. We have synthesized a novel REF substrate, CNIR800, that carries a near-infrared (NIR) fluorochrome IRDye 800CW, with a quencher connected through the lactam ring that is hydrolyzed by the enzyme BlaC (β-lactamase) that is naturally expressed by M. tuberculosis. CNIR800 produces long-wavelength emission at 795 nm upon excitation (745 nm) and exhibits significantly improved signal to noise ratios for detection of M. tuberculosis. The detection threshold with CNIR800 is approximately 100 colony-forming units (CFU) in vitro and <1000 CFU in the lungs of mice. Additionally, fluorescence signal from cleaved CNIR800 reaches maximal levels 4-6 hours after administration in live animals, allowing accurate evaluation of antituberculous drug efficacy. Thus, CNIR800 represents an excellent substrate for accurate detection of M. tuberculosis rapidly and specifically in animals, facilitating research toward understanding pathogenic mechanisms, evaluation of therapeutic outcomes, and screening new vaccines.
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Affiliation(s)
- Hee-Jeong Yang
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health Science Center, Bryan
| | - Ying Kong
- Department of Microbiology, Immunology, and Biochemistry, University of Tennessee Health Science Center, Memphis
| | - Yunfeng Cheng
- Department of Radiology, Stanford University, California
| | - Harish Janagama
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health Science Center, Bryan
| | - Hany Hassounah
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health Science Center, Bryan
| | - Hexin Xie
- Department of Radiology, Stanford University, California
| | - Jianghong Rao
- Department of Radiology, Stanford University, California
| | - Jeffrey D Cirillo
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health Science Center, Bryan
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Nooshabadi F, Yang HJ, Cheng Y, Durkee MS, Xie H, Rao J, Cirillo JD, Maitland KC. Intravital excitation increases detection sensitivity for pulmonary tuberculosis by whole-body imaging with β-lactamase reporter enzyme fluorescence. JOURNAL OF BIOPHOTONICS 2017; 10:821-829. [PMID: 27753271 PMCID: PMC5703064 DOI: 10.1002/jbio.201600132] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 08/08/2016] [Accepted: 09/18/2016] [Indexed: 05/08/2023]
Abstract
Tuberculosis is a pulmonary disease with an especially high mortality rate in immuno-compromised populations, specifically children and HIV positive individuals. The causative agent, Mycobacterium tuberculosis (Mtb), is a very slow growing and difficult organism to work with, making both diagnosis and development of effective treatments cumbersome. We utilize a fiber-optic fluorescence microendoscope integrated with a whole-body imaging system for in vivo Mtb detection. The system exploits an endogenous enzyme of Mtb (β-lactamase, or BlaC) using a BlaC-specific NIR fluorogenic substrate. In the presence of BlaC, this substrate is cleaved and becomes fluorescent. Using intravital illumination of the lung to excite this probe, sensitivity of the optical system increases over trans- and epi-illumination methods of whole-body fluorescence imaging. We demonstrate that integration of these imaging technologies with BlaC-specific fluorescent reporter probe improves the level of detection to ∼100 colony forming units, a 100× increase in sensitivity in comparison to epi-illumination and a 10× increase in sensitivity in comparison to previous work in intravital excitation of tdTomato-expressing Mtb. This lower detection threshold enables the study of early stage bacterial infections with clinical strains of Mtb and longitudinal studies of disease pathogenesis and therapeutic efficacy with multiple time points in a single animal.
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Affiliation(s)
- Fatemeh Nooshabadi
- Biomedical Engineering Department, 3120 TAMU, Texas A&M University, College Station, TX 77843, United States
| | - Hee-Jeong Yang
- Microbial Pathogenesis and Immunology Department, Texas A&M University Health Science Center, Bryan, Texas 77807, United States
| | - Yunfeng Cheng
- Radiology Department, Stanford University, Stanford, CA 94304, United States
| | - Madeleine S. Durkee
- Biomedical Engineering Department, 3120 TAMU, Texas A&M University, College Station, TX 77843, United States
| | - Hexin Xie
- Radiology Department, Stanford University, Stanford, CA 94304, United States
| | - Jianghong Rao
- Radiology Department, Stanford University, Stanford, CA 94304, United States
| | - Jeffrey D. Cirillo
- Microbial Pathogenesis and Immunology Department, Texas A&M University Health Science Center, Bryan, Texas 77807, United States
| | - Kristen C. Maitland
- Biomedical Engineering Department, 3120 TAMU, Texas A&M University, College Station, TX 77843, United States
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Sule P, Tilvawala R, Behinaein P, Walkup GK, Cirillo JD. New directions using reporter enzyme fluorescence (REF) as a tuberculosis diagnostic platform. Tuberculosis (Edinb) 2016; 101S:S78-S82. [PMID: 27729258 DOI: 10.1016/j.tube.2016.09.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Although tuberculosis (TB) is one of the most common causes of morbidity and mortality in humans worldwide and diagnostic methods have been in place for more than 100 years, diagnosis remains a challenge. The main problems with diagnosis relate to the time needed to obtain a definitive result, difficulty in obtaining sputum, the primary clinical material used, and the ability of the causative agent, Mycobacterium tuberculosis, to cause disease in nearly any tissue within the body. In order to decrease incidence of TB, discovery of a novel interventions will be required, since current technologies have only been able to control numbers of infections, not reduce them. Diagnostic innovation is particularly needed because there are no effective pediatric or extrapulmonary TB diagnostic methods and multiple-drug resistance is only identified in less than 25% of those patients that are thought to have it. The most common diagnostic method worldwide remains acid-fast stain on sputum, with a threshold of ∼10,000 bacteria/ml that is only reached ∼5-6 months after development of symptoms. In order to obtain definitive diagnostic results earlier during the disease process, we have developed a diagnostic method designated reporter enzyme fluorescence (REF) that utilizes BlaC produced by M. tuberculosis and custom substrates to produce a specific fluorescent signal with as few as 10 bacteria/ml in clinical samples. We believe that the unique biology of the REF technique will allow it to contribute new diagnostic information that is complementary to all existing diagnostic tests as well as those currently known to be in development.
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Affiliation(s)
- Preeti Sule
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health Science Center, Center for Airborne Pathogens Research and Imaging, Medical Research & Education Building, 8447 State Hwy 47, Bryan, TX 77807, USA
| | - Ronak Tilvawala
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health Science Center, Center for Airborne Pathogens Research and Imaging, Medical Research & Education Building, 8447 State Hwy 47, Bryan, TX 77807, USA
| | - Parnia Behinaein
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health Science Center, Center for Airborne Pathogens Research and Imaging, Medical Research & Education Building, 8447 State Hwy 47, Bryan, TX 77807, USA
| | - Grant K Walkup
- Agios Pharmaceuticals, 88 Sydney St., Cambridge, MA 02139, USA
| | - Jeffrey D Cirillo
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health Science Center, Center for Airborne Pathogens Research and Imaging, Medical Research & Education Building, 8447 State Hwy 47, Bryan, TX 77807, USA.
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Nusbaum RJ, Calderon VE, Huante MB, Sutjita P, Vijayakumar S, Lancaster KL, Hunter RL, Actor JK, Cirillo JD, Aronson J, Gelman BB, Lisinicchia JG, Valbuena G, Endsley JJ. Pulmonary Tuberculosis in Humanized Mice Infected with HIV-1. Sci Rep 2016; 6:21522. [PMID: 26908312 PMCID: PMC4808832 DOI: 10.1038/srep21522] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 01/26/2016] [Indexed: 11/09/2022] Open
Abstract
Co-infection with HIV increases the morbidity and mortality associated with tuberculosis due to multiple factors including a poorly understood microbial synergy. We developed a novel small animal model of co-infection in the humanized mouse to investigate how HIV infection disrupts pulmonary containment of Mtb. Following dual infection, HIV-infected cells were localized to sites of Mtb-driven inflammation and mycobacterial replication in the lung. Consistent with disease in human subjects, we observed increased mycobacterial burden, loss of granuloma structure, and increased progression of TB disease, due to HIV co-infection. Importantly, we observed an HIV-dependent pro-inflammatory cytokine signature (IL-1β, IL-6, TNFα, and IL-8), neutrophil accumulation, and greater lung pathology in the Mtb-co-infected lung. These results suggest that in the early stages of acute co-infection in the humanized mouse, infection with HIV exacerbates the pro-inflammatory response to pulmonary Mtb, leading to poorly formed granulomas, more severe lung pathology, and increased mycobacterial burden and dissemination.
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Affiliation(s)
| | | | | | - Putri Sutjita
- University of Texas Medical Branch, Galveston, TX 77555, USA
| | | | | | - Robert L Hunter
- University of Texas-Houston Health Science Center, Houston, TX 77030, USA
| | - Jeffrey K Actor
- University of Texas-Houston Health Science Center, Houston, TX 77030, USA
| | | | - Judith Aronson
- University of Texas Medical Branch, Galveston, TX 77555, USA
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Nooshabadi F, Yang HJ, Bixler JN, Kong Y, Cirillo JD, Maitland KC. Intravital Fluorescence Excitation in Whole-Animal Optical Imaging. PLoS One 2016; 11:e0149932. [PMID: 26901051 PMCID: PMC4762773 DOI: 10.1371/journal.pone.0149932] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 02/06/2016] [Indexed: 12/22/2022] Open
Abstract
Whole-animal fluorescence imaging with recombinant or fluorescently-tagged pathogens or cells enables real-time analysis of disease progression and treatment response in live animals. Tissue absorption limits penetration of fluorescence excitation light, particularly in the visible wavelength range, resulting in reduced sensitivity to deep targets. Here, we demonstrate the use of an optical fiber bundle to deliver light into the mouse lung to excite fluorescent bacteria, circumventing tissue absorption of excitation light in whole-animal imaging. We present the use of this technology to improve detection of recombinant reporter strains of tdTomato-expressing Mycobacterium bovis BCG (Bacillus Calmette Guerin) bacteria in the mouse lung. A microendoscope was integrated into a whole-animal fluorescence imager to enable intravital excitation in the mouse lung with whole-animal detection. Using this technique, the threshold of detection was measured as 103 colony forming units (CFU) during pulmonary infection. In comparison, the threshold of detection for whole-animal fluorescence imaging using standard epi-illumination was greater than 106 CFU.
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Affiliation(s)
- Fatemeh Nooshabadi
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, United States of America
| | - Hee-Jeong Yang
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, Bryan, Texas, United States of America
| | - Joel N. Bixler
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, United States of America
| | - Ying Kong
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, Bryan, Texas, United States of America
| | - Jeffrey D. Cirillo
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, Bryan, Texas, United States of America
| | - Kristen C. Maitland
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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Bruckbauer ST, Kvitko BH, Karkhoff-Schweizer RR, Schweizer HP. Tn5/7-lux: a versatile tool for the identification and capture of promoters in gram-negative bacteria. BMC Microbiol 2015; 15:17. [PMID: 25648327 PMCID: PMC4328036 DOI: 10.1186/s12866-015-0354-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 01/19/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The combination of imaging technologies and luciferase-based bioluminescent bacterial reporter strains provide a sensitive and simple non-invasive detection method (photonic bioimaging) for the study of diverse biological processes, as well as efficacy of therapeutic interventions, in live animal models of disease. The engineering of bioluminescent bacteria required for photonic bioimaging is frequently hampered by lack of promoters suitable for strong, yet stable luciferase gene expression. RESULTS We devised a novel method for identification of constitutive native promoters in Gram-negative bacteria. The method is based on a Tn5/7 transposon that exploits the unique features of Tn5 (random transposition) and Tn7 (site-specific transposition). The transposons are designed such that Tn5 transposition will allow insertion of a promoter-less bacterial luxCDABE operon downstream of a bacterial gene promoter. Cloning of DNA fragments from luminescent isolates results in a plasmid that replicates in pir (+) hosts. Sequencing of the lux-chromosomal DNA junctions on the plasmid reveals transposon insertion sites within genes or operons. The plasmid is also a mini-Tn7-lux delivery vector that can be used to introduce the promoter-lux operon fusion into other derivatives of the bacterium of interest in an isogenic fashion. Alternatively, promoter-containing sequences can be PCR-amplified from plasmid or chromosomal DNA and cloned into a series of accompanying mini-Tn7-lux vectors. The mini-Tn5/7-lux and mini-Tn7-lux vectors are equipped with diverse selection markers and thus applicable in numerous Gram-negative bacteria. Various mini-Tn5/7-lux vectors were successfully tested for transposition and promoter identification by imaging in Acinetobacter baumannii, Escherichia coli, and Burkholderia pseudomallei. Strong promoters were captured for lux expression in E. coli and A. baumannii. Some mini-Tn7-lux vectors are also equipped with attB sites for swapping of the lux operon with other reporter genes using Gateway technology. CONCLUSIONS Although mini-Tn5-lux and mini-Tn7-lux elements have previously been developed and used for bacterial promoter identification and chromosomal insertion of promoter-lux gene fusions, respectively, the newly developed mini-Tn5/7-lux and accompanying accessory plasmids streamline and accelerate the promoter discovery and bioluminescent strain engineering processes. Availability of vectors with diverse selection markers greatly extend the host-range of promoter probe and lux gene fusion vectors.
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Affiliation(s)
- Steven T Bruckbauer
- Department of Microbiology, Immunology and Pathology, and Rocky Mountain Regional Center of Excellence for Biodefense and Emerging Infectious Diseases Research, Colorado State University, Fort Collins, 80523, CO, USA. .,Present Address: Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, 53706, WI, USA.
| | - Brian H Kvitko
- Department of Microbiology, Immunology and Pathology, and Rocky Mountain Regional Center of Excellence for Biodefense and Emerging Infectious Diseases Research, Colorado State University, Fort Collins, 80523, CO, USA. .,Present Address: MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, 48824, MI, USA.
| | - RoxAnn R Karkhoff-Schweizer
- Department of Microbiology, Immunology and Pathology, and Rocky Mountain Regional Center of Excellence for Biodefense and Emerging Infectious Diseases Research, Colorado State University, Fort Collins, 80523, CO, USA.
| | - Herbert P Schweizer
- Department of Microbiology, Immunology and Pathology, and Rocky Mountain Regional Center of Excellence for Biodefense and Emerging Infectious Diseases Research, Colorado State University, Fort Collins, 80523, CO, USA. .,Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Emerging Pathogens Institute, PO Box 100266, Gainesville, 32610-0266, FL, USA.
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Vijayakumar S, Finney John S, Nusbaum RJ, Ferguson MR, Cirillo JD, Olaleye O, Endsley JJ. In vitro model of mycobacteria and HIV-1 co-infection for drug discovery. Tuberculosis (Edinb) 2014; 93 Suppl:S66-70. [PMID: 24388652 DOI: 10.1016/s1472-9792(13)70013-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Tuberculosis (TB) has become a global health threat in the wake of the Human Immunodeficiency Virus (HIV) pandemic and is the leading cause of death in people with HIV/AIDS. Treatment of patients with Mycobacterium tuberculosis (Mtb)/HIV co-infection is complicated by drug interactions and toxicity that present huge challenges for clinical intervention. Discovery efforts to identify novel compounds with increased effectiveness and decreased drug-drug interactions against Mtb, HIV-1, or both, would be greatly aided by the use of a co-infection model for screening drug libraries. Currently, inhibitors of Mtb are screened independently in mycobacterial cell cultures or target based biochemical screens and less often in macrophages or peripheral blood leukocytes. Similarly, HIV-1 drugs are screened in vitro independently from anti-mycobacterial compounds. Here, we describe an in vitro model where primary human peripheral blood mononuclear cells or monocyte-derived macrophages are infected with Mycobacterium bovis BCG and HIV-1, and used to evaluate drug toxicity and activity in a co-infection setting. Our results with standard compounds (e.g. Azidothymidine, Rifampicin) demonstrate the utility of this in vitro model to evaluate drug effectiveness relevant to cellular toxicity, HIV-1 replication, and intracellular mycobacterial growth, through the use of ELISA, bacterial enumeration, and multi-variate flow cytometry. This model and associated assays have great value in accelerating the discovery of compounds for use in Mtb/HIV-1 co-infected patients.
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Affiliation(s)
- Sudhamathi Vijayakumar
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA
| | - Sarah Finney John
- Department of Pharmaceutical Sciences, Texas Southern University, Houston, TX, USA
| | - Rebecca J Nusbaum
- Institute for Translational Science, University of Texas Medical Branch, Galveston, TX, USA
| | - Monique R Ferguson
- Department of Internal Medicine, Division of Infectious Diseases, University of Texas Medical Branch, Galveston, TX, USA
| | - Jeffrey D Cirillo
- Department of Microbial Pathogenesis and Immunology Texas A&M Health Sciences Center, College Station, TX, USA
| | - Omonike Olaleye
- Department of Pharmaceutical Sciences, Texas Southern University, Houston, TX, USA
| | - Janice J Endsley
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA; Institute for Human Infections and Immunity, Center for Tropical Diseases, Sealy Center for Vaccine Development, and Center for Biodefense and Emerging Infectious Diseases, UTMB, Galveston, TX, USA.
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Real-time bioluminescence imaging of mixed mycobacterial infections. PLoS One 2014; 9:e108341. [PMID: 25265287 PMCID: PMC4180448 DOI: 10.1371/journal.pone.0108341] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 08/28/2014] [Indexed: 01/18/2023] Open
Abstract
Molecular analysis of infectious processes in bacteria normally involves construction of isogenic mutants that can then be compared to wild type in an animal model. Pathogenesis and antimicrobial studies are complicated by variability between animals and the need to sacrifice individual animals at specific time points. Live animal imaging allows real-time analysis of infections without the need to sacrifice animals, allowing quantitative data to be collected at multiple time points in all organs simultaneously. However, imaging has not previously allowed simultaneous imaging of both mutant and wild type strains of mycobacteria in the same animal. We address this problem by using both firefly (Photinus pyralis) and click beetle (Pyrophorus plagiophthalamus) red luciferases, which emit distinct bioluminescent spectra, allowing simultaneous imaging of two different mycobacterial strains during infection. We also demonstrate that these same bioluminescence reporters can be used to evaluate therapeutic efficacy in real-time, greatly facilitating our ability to screen novel antibiotics as they are developed. Due to the slow growth rate of mycobacteria, novel imaging technologies are a pressing need, since they can they can impact the rate of development of new therapeutics as well as improving our understanding of virulence mechanisms and the evaluation of novel vaccine candidates.
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Abstract
Mycobacterium tuberculosis (M.tb) is the second leading infectious cause of death worldwide and the primary cause of death in people living with HIV/AIDS. There are several excellent animal models employed to study tuberculosis (TB), but many have limitations for reproducing human pathology and none are amenable to the direct study of HIV/M.tb co-infection. The humanized mouse has been increasingly employed to explore HIV infection and other pathogens where animal models are limiting. Our goal was to develop a small animal model of M.tb infection using the bone marrow, liver, thymus (BLT) humanized mouse. NOD-SCID/γc(null) mice were engrafted with human fetal liver and thymus tissue, and supplemented with CD34(+) fetal liver cells. Excellent reconstitution, as measured by expression of the human CD45 pan leukocyte marker by peripheral blood populations, was observed at 12 weeks after engraftment. Human T cells (CD3, CD4, CD8), as well as natural killer cells and monocyte/macrophages were all observed within the human leukocyte (CD45(+)) population. Importantly, human T cells were functionally competent as determined by proliferative capacity and effector molecule (e.g. IFN-γ, granulysin, perforin) expression in response to positive stimuli. Animals infected intranasally with M.tb had progressive bacterial infection in the lung and dissemination to spleen and liver from 2-8 weeks post infection. Sites of infection in the lung were characterized by the formation of organized granulomatous lesions, caseous necrosis, bronchial obstruction, and crystallization of cholesterol deposits. Human T cells were distributed throughout the lung, liver, and spleen at sites of inflammation and bacterial growth and were organized to the periphery of granulomas. These preliminary results demonstrate the potential to use the humanized mouse as a model of experimental TB.
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