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.

Download full-text


Available from: Charles A Peloquin, Nov 05, 2014
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    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.
    Preview · Article · Mar 2014 · International Journal of Mycobacteriology
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Tuberculous meningitis (TBM) is the most common form of central nervous system tuberculosis (TB) and has very high morbidity and mortality. TBM is typically a subacute disease with symptoms that may persist for weeks before diagnosis. Characteristic cerebrospinal fluid (CSF) findings of TBM include a lymphocytic-predominant pleiocytosis, elevated protein, and low glucose. CSF acid-fast smear and culture have relatively low sensitivity but yield is increased with multiple, large volume samples. Nucleic acid amplification of the CSF by PCR is highly specific but suboptimal sensitivity precludes ruling out TBM with a negative test. Treatment for TBM should be initiated as soon as clinical suspicion is supported by initial CSF studies. Empiric treatment should include at least four first-line drugs, preferably isoniazid, rifampin, pyrazinamide, and streptomycin or ethambutol; the role of fluoroquinolones remains to be determined. Adjunctive treatment with corticosteroids has been shown to improve mortality with TBM. In HIV-positive individuals with TBM, important treatment considerations include drug interactions, development of immune reconstitution inflammatory syndrome, unclear benefit of adjunctive corticosteroids, and higher rates of drug-resistant TB. Testing the efficacy of second-line and new anti-TB drugs in animal models of experimental TBM is needed to help determine the optimal regimen for drug-resistant TB.
    Full-text · Article · Dec 2011
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mycobacterium tuberculosis is a difficult pathogen to combat and the first-line drugs currently in use are 40-60 years old. The need for new TB drugs is urgent, but the time to identify, develop and ultimately advance new drug regimens onto the market has been excruciatingly slow. On the other hand, the drugs currently in clinical development, and the recent gains in knowledge of the pathogen and the disease itself give us hope for finding new drug targets and new drug leads. In this article we highlight the unique biology of the pathogen and several possible ways to identify new TB chemical leads. The Global Alliance for TB Drug Development (TB Alliance) is a not-for-profit organization whose mission is to accelerate the discovery and development of new TB drugs. The organization carries out research and development in collaboration with many academic laboratories and pharmaceutical companies around the world. In this perspective we will focus on the early discovery phases of drug development and try to provide snapshots of both the current status and future prospects.
    Full-text · Article · Sep 2011 · Future medicinal chemistry
Show more