Comparative Studies Evaluating Mouse Models Used for Efficacy Testing of Experimental Drugs against Mycobacterium tuberculosis

Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
Antimicrobial Agents and Chemotherapy (Impact Factor: 4.48). 12/2010; 55(3):1237-47. DOI: 10.1128/AAC.00595-10
Source: PubMed


Methodologies for preclinical animal model testing of drugs against Mycobacterium tuberculosis vary from laboratory to laboratory; however, it is unknown if these variations result in different outcomes. Thus, a series of head-to-head comparisons of drug regimens in three commonly used mouse models (intravenous, a low-dose aerosol, and a high-dose aerosol infection model) and in two strains of mice are reported here. Treatment with standard tuberculosis (TB) drugs resulted in similar efficacies in two mouse species after a low-dose aerosol infection. When comparing the three different infection models, the efficacies in mice of rifampin and pyrazinamide were similar when administered with either isoniazid or moxifloxacin. Relapse studies revealed that the standard drug regimen showed a significantly higher relapse rate than the moxifloxacin-containing regimen. In fact, 4 months of the moxifloxacin-containing combination regimen showed similar relapse rates as 6 months of the standard regimen. The intravenous model showed slower bactericidal killing kinetics with the combination regimens tested and a higher relapse of infection than either aerosol infection models. All three models showed similar outcomes for in vivo efficacy and relapse of infection for the drug combinations tested, regardless of the mouse infection model used. Efficacy data for the drug combinations used also showed similar results, regardless of the formulation used for rifampin or timing of the drugs administered in combination. In all three infection models, the dual combination of rifampin and pyrazinamide was less sterilizing than the standard three-drug regimen, and therefore the results do not support the previously reported antagonism between standard TB agents.

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Available from: Charles A Peloquin, Nov 05, 2014
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    • "The control plasmid without the RFP was not introduced into the WT strain, as the purpose was to determine if the metabolic burden due to the RFP could adversely affect the strain's ability to cause natural pathogenesis. The outbred, immunocompetent Swiss mice were used as they are commonly used for in vivo efficacy testing of lead anti-tubercular molecules [37] and are also used in-house. The mice were given a high dose (1.5 · 10 6 bacilli/mouse) intravenous infection of wild type/ FS of MTB H37Rv. "
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    ABSTRACT: Background Mycobacterium tuberculosis is known to slow down its transcriptional activity during dormancy. Hence, while using reporter strains, it is important to couple the reporter gene to a promoter that is strong and sensitive both in active and dormant M. tuberculosis. Since respiration is an indispensable process even in dormant bacteria, validation of the promoters of respiratory chain genes – type II NADH dehydrogenase (Pndh) and adenosine triphosphate (ATP) synthase operon (Patps) – of MTB was undertaken for this purpose. Methods Putative promoter containing sequences were cloned upstream of a red fluorescent protein (RFP) gene. Mycobacterium smegmatis or M. tuberculosis carrying episomal constructs were validated for growth, fitness and fluorescence in different models in vitro and in vivo. Results Either promoter can drive stable and strong expression of RFP in actively growing and dormant M. smegmatis in vitro without significantly affecting growth or viability. Fluorescence due to Pndh and Patps was significantly higher than Phsp60. The fitness of M. tuberculosis H37Rv counterparts was unaffected inside J774 macrophages. In immunocompetent mice, despite an initial attenuation in the lungs, both strains reached loads similar to wild type during chronic infection. In the spleen, the fluorescent strain counts were similar to wild type counts throughout. RFP fluorescence in tissue homogenates was more homogenous among mice due to Pndh compared with Patps. Conclusions Coupling an appropriate reporter to the promoter of ndh-2 gene of M. tuberculosis can make the reporter expression respiration sensitive and thereby reliably detect both active and dormant populations of the reporter strain.
    International Journal of Mycobacteriology 03/2014; 3(1). DOI:10.1016/j.ijmyco.2013.12.002
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    • "Animal models are critically important in testing the efficacy of new drugs and vaccines against TB [82]. The challenge of animal models of TBM is that TBM in humans is considered to typically occur a certain period of time after a primary infection through the respiratory tract, a condition that would be difficult to mimic in experimental animals. "
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