scholarly journals Developing New Drugs for Mycobacterium tuberculosis Therapy: What Information Do We Get from Preclinical Animal Models?

2020 ◽  
Vol 64 (12) ◽  
Author(s):  
G. L. Drusano ◽  
Brandon Duncanson ◽  
C. A. Scanga ◽  
S. Kim ◽  
S. Schmidt ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Animal Models ◽  
Scale Up ◽  
New Drugs ◽  
Model Systems ◽  
Infection Model ◽  
New Agents ◽  
Content Type ◽  
Preclinical Animal Models ◽  
The Impact

ABSTRACT Preclinical animal models of infection are employed to develop new agents but also to screen among molecules to rank them. There are often major differences between human pharmacokinetic (PK) profiles and those developed by animal models of infection, and these may lead to substantial differences in efficacy relative to that seen in humans. Linezolid is a repurposed agent employed to great effect for therapy of Mycobacterium tuberculosis. In this study, we used the hollow-fiber infection model (HFIM) to evaluate the impact of different pharmacokinetic profiles of mice and nonhuman primates (NHP) versus humans on bacterial cell kill as well as resistance suppression. We examined both plasma and epithelial lining fluid (ELF) profiles. We examined simulated exposures equivalent to 600 mg and 900 mg daily of linezolid in humans. For both plasma and ELF exposures, the murine PK profile provided estimates of effect that were biased low relative to human and NHP PK profiles. Mathematical modeling identified a linkage between minimum concentrations (Cmin) and bacterial kill and peak concentrations (Cpeak) and resistance suppression, with the latter being supported by a prospective validation study. Finding new agents with novel mechanisms of action against M. tuberculosis is difficult. It would be a tragedy to discard a new agent because of a biased estimate of effect in a preclinical animal system. The HFIM provides a system to benchmark evaluation of new compounds in preclinical animal model systems against human PK effects (species scale-up estimates of PK), to safeguard against unwarranted rejection of promising new agents.

scholarly journals Multiscale Model of Mycobacterium tuberculosis Infection Maps Metabolite and Gene Perturbations to Granuloma Sterilization Predictions

2016 ◽  
Vol 84 (5) ◽  
pp. 1650-1669 ◽  
Author(s):  
Elsje Pienaar ◽  
William M. Matern ◽  
Jennifer J. Linderman ◽  
Joel S. Bader ◽  
Denise E. Kirschner
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Host Immunity ◽  
New Drugs ◽  
Metabolic Enzyme ◽  
Adaptation To Hypoxia ◽  
Mycobacterium Tuberculosis Infection ◽  
Lipid Inclusion ◽  
Content Type ◽  
The Impact

Granulomas are a hallmark of tuberculosis. Inside granulomas, the pathogenMycobacterium tuberculosismay enter a metabolically inactive state that is less susceptible to antibiotics. UnderstandingM. tuberculosismetabolism within granulomas could contribute to reducing the lengthy treatment required for tuberculosis and provide additional targets for new drugs. Two key adaptations ofM. tuberculosisare a nonreplicating phenotype and accumulation of lipid inclusions in response to hypoxic conditions. To explore how these adaptations influence granuloma-scale outcomesin vivo, we present a multiscalein silicomodel of granuloma formation in tuberculosis. The model comprises host immunity,M. tuberculosismetabolism,M. tuberculosisgrowth adaptation to hypoxia, and nutrient diffusion. We calibrated our model toin vivodata from nonhuman primates and rabbits and apply the model to predictM. tuberculosispopulation dynamics and heterogeneity within granulomas. We found that bacterial populations are highly dynamic throughout infection in response to changing oxygen levels and host immunity pressures. Our results indicate that a nonreplicating phenotype, but not lipid inclusion formation, is important for long-termM. tuberculosissurvival in granulomas. We used virtualM. tuberculosisknockouts to predict the impact of both metabolic enzyme inhibitors and metabolic pathways exploited to overcome inhibition. Results indicate that knockouts whose growth rates are below ∼66% of the wild-type growth rate in a culture medium featuring lipid as the only carbon source are unable to sustain infections in granulomas. By mapping metabolite- and gene-scale perturbations to granuloma-scale outcomes and predicting mechanisms of sterilization, our method provides a powerful tool for hypothesis testing and guiding experimental searches for novel antituberculosis interventions.

scholarly journals Monkey Models of Tuberculosis: Lessons Learned

2014 ◽  
Vol 83 (3) ◽  
pp. 852-862 ◽  
Author(s):  
Juliet C. Peña ◽  
Wen-Zhe Ho
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Animal Models ◽  
Nonhuman Primates ◽  
Lessons Learned ◽  
Preclinical Testing ◽  
Content Type ◽  
Cynomolgus Macaques ◽  
Drug Regimens

The use of animal models has been invaluable for studying the pathogenesis ofMycobacterium tuberculosisinfection, as well as for testing the efficacy of vaccines and drug regimens for tuberculosis. Among the applied animal models, nonhuman primates, particularly macaques, share the greatest anatomical and physiological similarities with humans. As such, macaque models have been used for investigating tuberculosis pathogenesis and preclinical testing of drugs and vaccines. This review focuses on published major studies which illustrate how the rhesus and cynomolgus macaques have enriched and may continue to advance the field of global tuberculosis research.

scholarly journals In VivoEfficacy of Anuran Trypsin Inhibitory Peptides against Staphylococcal Skin Infection and the Impact of Peptide Cyclization

2015 ◽  
Vol 59 (4) ◽  
pp. 2113-2121 ◽  
Author(s):  
U. Malik ◽  
O. N. Silva ◽  
I. C. M. Fensterseifer ◽  
L. Y. Chan ◽  
R. J. Clark ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Cyclic Peptide ◽  
Sequence Similarity ◽  
Infection Model ◽  
Content Type ◽  
Wide Range ◽  
Inhibitory Activities ◽  
The Impact

ABSTRACTStaphylococcus aureusis a virulent pathogen that is responsible for a wide range of superficial and invasive infections. Its resistance to existing antimicrobial drugs is a global problem, and the development of novel antimicrobial agents is crucial. Antimicrobial peptides from natural resources offer potential as new treatments against staphylococcal infections. In the current study, we have examined the antimicrobial properties of peptides isolated from anuran skin secretions and cyclized synthetic analogues of these peptides. The structures of the peptides were elucidated by nuclear magnetic resonance (NMR) spectroscopy, revealing high structural and sequence similarity with each other and with sunflower trypsin inhibitor 1 (SFTI-1). SFTI-1 is an ultrastable cyclic peptide isolated from sunflower seeds that has subnanomolar trypsin inhibitory activity, and this scaffold offers pharmaceutically relevant characteristics. The five anuran peptides were nonhemolytic and noncytotoxic and had trypsin inhibitory activities similar to that of SFTI-1. They demonstrated weakin vitroinhibitory activities againstS. aureus, but several had strong antibacterial activities againstS. aureusin anin vivomurine wound infection model. pYR, an immunomodulatory peptide fromRana sevosa, was the most potent, with complete bacterial clearance at 3 mg · kg−1. Cyclization of the peptides improved their stability but was associated with a concomitant decrease in antimicrobial activity. In summary, these anuran peptides are promising as novel therapeutic agents for treating infections from a clinically resistant pathogen.

scholarly journals Preexposure to Isavuconazole Increases the Virulence of Mucorales but Not Aspergillus fumigatus in a Drosophila melanogaster Infection Model

2018 ◽  
Vol 63 (2) ◽  
pp. e01896-18 ◽  
Author(s):  
Sebastian Wurster ◽  
Russell E. Lewis ◽  
Nathaniel D. Albert ◽  
Dimitrios P. Kontoyiannis
Keyword(s):  
Drosophila Melanogaster ◽  
Aspergillus Fumigatus ◽  
Clinical Isolates ◽  
Infection Model ◽  
Content Type ◽  
The Impact

ABSTRACT Breakthrough mucormycosis in patients receiving isavuconazole prophylaxis or therapy has been reported. We compared the impact of isavuconazole and voriconazole exposure on the virulence of clinical isolates of Aspergillus fumigatus and different Mucorales species in a Drosophila melanogaster infection model. In contrast to A. fumigatus, a hypervirulent phenotype was found in all tested Mucorales upon preexposure to either voriconazole or isavuconazole. These findings may contribute to the explanation of breakthrough mucormycosis in isavuconazole-treated patients.

Identification of new agents for the prevention of prostate cancer using preclinical animal models

2003 ◽  
Vol 2 (6) ◽  
pp. 13
Author(s):  
Vernon E Steele ◽  
David L McCormick ◽  
Maarten C Bosland ◽  
K.V.N Rao ◽  
Ronald A Lubet
Keyword(s):  
Prostate Cancer ◽  
Animal Models ◽  
New Agents ◽  
Preclinical Animal Models

scholarly journals Coxiella burnetii Intratracheal Aerosol Infection Model in Mice, Guinea Pigs, and Nonhuman Primates

2019 ◽  
Vol 87 (12) ◽  
Author(s):  
A. E. Gregory ◽  
E. J. van Schaik ◽  
K. E. Russell-Lodrigue ◽  
A. P. Fratzke ◽  
J. E. Samuel
Keyword(s):  
Animal Models ◽  
Coxiella Burnetii ◽  
Guinea Pigs ◽  
Nonhuman Primates ◽  
Q Fever ◽  
Febrile Illness ◽  
Cell Vaccine ◽  
Infection Model ◽  
Atypical Pneumonia ◽  
Content Type

ABSTRACT Coxiella burnetii, the etiological agent of Q fever, is a Gram-negative bacterium transmitted to humans by inhalation of contaminated aerosols. Acute Q fever is often self-limiting, presenting as a febrile illness that can result in atypical pneumonia. In some cases, Q fever becomes chronic, leading to endocarditis that can be life threatening. The formalin-inactivated whole-cell vaccine (WCV) confers long-term protection but has significant side effects when administered to presensitized individuals. Designing new vaccines against C. burnetii remains a challenge and requires the use of clinically relevant modes of transmission in appropriate animal models. We have developed a safe and reproducible C. burnetii aerosol challenge in three different animal models to evaluate the effects of pulmonary acquired infection. Using a MicroSprayer aerosolizer, BL/6 mice and Hartley guinea pigs were infected intratracheally with C. burnetii Nine Mile phase I (NMI) and demonstrated susceptibility as determined by measuring bacterial growth in the lungs and subsequent dissemination to the spleen. Histological analysis of lung tissue showed significant pathology associated with disease, which was more severe in guinea pigs. Infection using large-particle aerosol (LPA) delivery was further confirmed in nonhuman primates, which developed fever and pneumonia. We also demonstrate that vaccinating mice and guinea pigs with WCV prior to LPA challenge is capable of eliciting protective immunity that significantly reduces splenomegaly and the bacterial burden in spleen and lung tissues. These data suggest that these models can have appreciable value in using the LPA delivery system to study pulmonary Q fever pathogenesis as well as designing vaccine countermeasures to C. burnetii aerosol transmission.

scholarly journals The Impact of Leadered and Leaderless Gene Structures on Translation Efficiency, Transcript Stability, and Predicted Transcription Rates in Mycobacterium smegmatis

2020 ◽  
Vol 202 (9) ◽  
Author(s):  
Tien G. Nguyen ◽  
Diego A. Vargas-Blanco ◽  
Louis A. Roberts ◽  
Scarlet S. Shell
Keyword(s):  
Gene Expression ◽  
Mycobacterium Tuberculosis ◽  
Mycobacterium Smegmatis ◽  
Half Life ◽  
Untranslated Regions ◽  
Translation Efficiency ◽  
Production Rates ◽  
Content Type ◽  
The Impact ◽  
Mrna Half Life

ABSTRACT Regulation of gene expression is critical for Mycobacterium tuberculosis to tolerate stressors encountered during infection and for nonpathogenic mycobacteria such as Mycobacterium smegmatis to survive environmental stressors. Unlike better-studied models, mycobacteria express ∼14% of their genes as leaderless transcripts. However, the impacts of leaderless transcript structures on mRNA half-life and translation efficiency in mycobacteria have not been directly tested. For leadered transcripts, the contributions of 5′ untranslated regions (UTRs) to mRNA half-life and translation efficiency are similarly unknown. In M. tuberculosis and M. smegmatis, the essential sigma factor, SigA, is encoded by a transcript with a relatively short half-life. We hypothesized that the long 5′ UTR of sigA causes this instability. To test this, we constructed fluorescence reporters and measured protein abundance, mRNA abundance, and mRNA half-life and calculated relative transcript production rates. The sigA 5′ UTR conferred an increased transcript production rate, shorter mRNA half-life, and decreased apparent translation rate compared to a synthetic 5′ UTR commonly used in mycobacterial expression plasmids. Leaderless transcripts appeared to be translated with similar efficiency as those with the sigA 5′ UTR but had lower predicted transcript production rates. A global comparison of M. tuberculosis mRNA and protein abundances failed to reveal systematic differences in protein/mRNA ratios for leadered and leaderless transcripts, suggesting that variability in translation efficiency is largely driven by factors other than leader status. Our data are also discussed in light of an alternative model that leads to different conclusions and suggests leaderless transcripts may indeed be translated less efficiently. IMPORTANCE Tuberculosis, caused by Mycobacterium tuberculosis, is a major public health problem killing 1.5 million people globally each year. During infection, M. tuberculosis must alter its gene expression patterns to adapt to the stress conditions it encounters. Understanding how M. tuberculosis regulates gene expression may provide clues for ways to interfere with the bacterium’s survival. Gene expression encompasses transcription, mRNA degradation, and translation. Here, we used Mycobacterium smegmatis as a model organism to study how 5′ untranslated regions affect these three facets of gene expression in multiple ways. We furthermore provide insight into the expression of leaderless mRNAs, which lack 5′ untranslated regions and are unusually prevalent in mycobacteria.

scholarly journals Correlation between Disease Severity and the Intestinal Microbiome in Mycobacterium tuberculosis-Infected Rhesus Macaques

mBio ◽  
2019 ◽  
Vol 10 (3) ◽  
Author(s):  
Sivaranjani Namasivayam ◽  
Keith D. Kauffman ◽  
John A. McCulloch ◽  
Wuxing Yuan ◽  
Vishal Thovarai ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Host Resistance ◽  
Rhesus Macaques ◽  
Severe Disease ◽  
Predictive Biomarker ◽  
Host Susceptibility ◽  
Intestinal Microbiome ◽  
Metagenomic Sequencing ◽  
Content Type ◽  
The Impact

ABSTRACT The factors that determine host susceptibility to tuberculosis (TB) are poorly defined. The microbiota has been identified as a key influence on the nutritional, metabolic, and immunological status of the host, although its role in the pathogenesis of TB is currently unclear. Here, we investigated the influence of Mycobacterium tuberculosis exposure on the microbiome and conversely the impact of the intestinal microbiome on the outcome of M. tuberculosis exposure in a rhesus macaque model of tuberculosis. Animals were infected with different strains and doses of M. tuberculosis in three independent experiments, resulting in a range of disease severities. The compositions of the microbiotas were then assessed using a combination of 16S rRNA and metagenomic sequencing in fecal samples collected pre- and postinfection. Clustering analyses of the microbiota compositions revealed that alterations in the microbiome after M. tuberculosis infection were of much lower magnitude than the variability seen between individual monkeys. However, the microbiomes of macaques that developed severe disease were noticeably distinct from those of the animals with less severe disease as well as from each other. In particular, the bacterial families Lachnospiraceae and Clostridiaceae were enriched in monkeys that were more susceptible to infection, while numbers of Streptococcaceae were decreased. These findings in infected nonhuman primates reveal that certain baseline microbiome communities may strongly associate with the development of severe tuberculosis following infection and can be more important disease correlates than alterations to the microbiota following M. tuberculosis infection itself. IMPORTANCE Why some but not all individuals infected with Mycobacterium tuberculosis develop disease is poorly understood. Previous studies have revealed an important influence of the microbiota on host resistance to infection with a number of different disease agents. Here, we investigated the possible role of the individual’s microbiome in impacting the outcome of M. tuberculosis infection in rhesus monkeys experimentally exposed to this important human pathogen. Although M. tuberculosis infection itself caused only minor alterations in the composition of the gut microbiota in these animals, we observed a significant correlation between an individual monkey’s microbiome and the severity of pulmonary disease. More importantly, this correlation between microbiota structure and disease outcome was evident even prior to infection. Taken together, our findings suggest that the composition of the microbiome may be a useful predictor of tuberculosis progression in infected individuals either directly because of the microbiome’s direct influence on host resistance or indirectly because of its association with other host factors that have this influence. This calls for exploration of the potential of the microbiota composition as a predictive biomarker through carefully designed prospective studies.

scholarly journals Apotransferrin in Combination with Ciprofloxacin Slows Bacterial Replication, Prevents Resistance Amplification, and Increases Antimicrobial Regimen Effect

2019 ◽  
Vol 63 (5) ◽  
Author(s):  
Paul G. Ambrose ◽  
Brian D. VanScoy ◽  
Brian M. Luna ◽  
Jun Yan ◽  
Amber Ulhaq ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Bactericidal Effect ◽  
Bacterial Density ◽  
Infection Model ◽  
Time Curve ◽  
Content Type ◽  
Wide Range ◽  
Bacterial Replication ◽  
The Impact

ABSTRACT There has been renewed interest in combining traditional small-molecule antimicrobial agents with nontraditional therapies to potentiate antimicrobial effects. Apotransferrin, which decreases iron availability to microbes, is one such approach. We conducted a 48-h one-compartment in vitro infection model to explore the impact of apotransferrin on the bactericidal activity of ciprofloxacin. The challenge panel included four Klebsiella pneumoniae isolates with ciprofloxacin MIC values ranging from 0.08 to 32 mg/liter. Each challenge isolate was subjected to an ineffective ciprofloxacin monotherapy exposure (free-drug area under the concentration-time curve over 24 h divided by the MIC [AUC/MIC ratio] ranging from 0.19 to 96.6) with and without apotransferrin. As expected, the no-treatment and apotransferrin control arms showed unaltered prototypical logarithmic bacterial growth. We identified relationships between exposure and change in bacterial density for ciprofloxacin alone (R2 = 0.64) and ciprofloxacin in combination with apotransferrin (R2 = 0.84). Addition of apotransferrin to ciprofloxacin enabled a remarkable reduction in bacterial density across a wide range of ciprofloxacin exposures. For instance, at a ciprofloxacin AUC/MIC ratio of 20, ciprofloxacin monotherapy resulted in nearly 2 log10 CFU increase in bacterial density, while the combination of apotransferrin and ciprofloxacin resulted in 2 log10 CFU reduction in bacterial density. Furthermore, addition of apotransferrin significantly reduced the emergence of ciprofloxacin-resistant subpopulations compared to monotherapy. These data demonstrate that decreasing the rate of bacterial replication with apotransferrin in combination with antimicrobial therapy represents an opportunity to increase the magnitude of the bactericidal effect and to suppress the growth rate of drug-resistant subpopulations.

scholarly journals Generic Vancomycin Enriches Resistant Subpopulations of Staphylococcus aureus after Exposure in a Neutropenic Mouse Thigh Infection Model

2011 ◽  
Vol 56 (1) ◽  
pp. 243-247 ◽  
Author(s):  
Carlos A. Rodriguez ◽  
Maria Agudelo ◽  
Andres F. Zuluaga ◽  
Omar Vesga
Keyword(s):  
Staphylococcus Aureus ◽  
Population Analysis ◽  
Recovery Process ◽  
Control Group ◽  
Infection Model ◽  
Content Type ◽  
Sterile Saline ◽  
Generic Products ◽  
The Impact

ABSTRACTPrevious studies have shown that “bioequivalent” generic products of vancomycin are less effectivein vivoagainstStaphylococcus aureusthan the innovator compound. Considering that suboptimal bactericidal effect has been associated with emergence of resistance, we aimed to assessin vivothe impact of exposure to innovator and generic products of vancomycin onS. aureussusceptibility. A clinical methicillin-resistantS. aureus(MRSA) strain from a liver transplant patient with persistent bacteremia was used for which MIC, minimum bactericidal concentration (MBC), and autolytic properties were determined. Susceptibility was also assessed by determining a population analysis profile (PAP) with vancomycin concentrations from 0 to 5 mg/liter. ICR neutropenic mice were inoculated in each thigh with ∼7.0 log10CFU. Treatment with the different vancomycin products (innovator and three generics; 1,200 mg/kg of body weight/day every 3 h) started 2 h later while the control group received sterile saline. After 24 h, mice were euthanized, and the thigh homogenates were plated. Recovered colonies were reinoculated to new groups of animals, and the exposure-recovery process was repeated until 12 cycles were completed. The evolution of resistance was assessed by PAP after cycles 5, 10, 11, and 12. The initial isolate displayed reduced autolysis and higher resistance frequencies thanS. aureusATCC 29213 but without vancomycin-intermediateS. aureus(VISA) subpopulations. After 12 cycles, innovator vancomycin had significantly reduced resistant subpopulations at 1, 2, and 3 mg/liter, while the generic products had enriched them progressively by orders of magnitude. The great capacity of generic vancomycin to select for less susceptible organisms raises concerns about the role of therapeutic inequivalence of any antimicrobial on the epidemiology of resistance worldwide.

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