BackgroundDespite the availability of many animal models for tuberculosis (TB) research, there still exists a need for better understanding of the quiescent stage of disease observed in many humans. Here, we explored the use of the Wistar rat model for the study of protective immunity and control of Mycobacterium tuberculosis (Mtb) infection.Methodology/Principal FindingsThe kinetics of bacillary growth, evaluated by the colony stimulating assay (CFU) and the extent of lung pathology in Mtb infected Wistar rats were dependent on the virulence of the strains and the size of the infecting inoculums. Bacillary growth control was associated with induction of T helper type 1 (Th1) activation, the magnitude of which was also Mtb strain and dose dependent. Histopathology analysis of the infected lungs demonstrated the formation of well organized granulomas comprising epithelioid cells, multinucleated giant cells and foamy macrophages surrounded by large numbers of lymphocytes. The late stage subclinical form of disease was reactivated by immunosuppression leading to increased lung CFU.ConclusionThe Wistar rat is a valuable model for better understanding host-pathogen interactions that result in control of Mtb infection and potentially establishment of latent TB. These properties together with the ease of manipulation, relatively low cost and well established use of rats in toxicology and pharmacokinetic analyses make the rat a good animal model for TB drug discovery.
Multi-modality imaging methods are of great importance in oncologic studies for acquiring complementary information, enhancing the efficacy in tumor detection and characterization. We hereby demonstrate a hybrid non-invasive in vivo imaging approach of utilizing magnetic resonance imaging (MRI) and Multispectral Optoacoustic Tomography (MSOT) for molecular imaging of glucose uptake in an orthotopic glioblastoma in mouse. The molecular and functional information from MSOT can be overlaid on MRI anatomy via image coregistration to provide insights into probe uptake in the brain, which is verified by ex vivo fluorescence imaging and histological validation. In vivo MSOT and MRI imaging of an orthotopic glioma mouse model injected with IRDye800-2DG. Image coregistration between MSOT and MRI enables multifaceted (anatomical, functional, molecular) information from MSOT to be overlaid on MRI anatomy images to derive tumor physiological parameters such as perfusion, haemoglobin and oxygenation.
PURPOSE: Here we demonstrate the potential of multispectral optoacoustic tomography (MSOT), a new non-invasive structural and functional imaging modality, to track the growth and changes in blood oxygen saturation (sO2) in orthotopic glioblastoma (GBMs) and the surrounding brain tissues upon administration of a vascular disruptive agent (VDA). METHODS: Nude mice injected with U87MG tumor cells were longitudinally monitored for the development of orthotopic GBMs up to 15 days and observed for changes in sO2 upon administration of combretastatin A4 phosphate (CA4P, 30 mg/kg), an FDA approved VDA for treating solid tumors. We employed a newly-developed non-negative constrained approach for combined MSOT image reconstruction and unmixing in order to quantitatively map sO2 in whole mouse brains. RESULTS: Upon longitudinal monitoring, tumors could be detected in mouse brains using single-wavelength data as early as 6 days post tumor cell inoculation. Fifteen days post-inoculation, tumors had higher sO2 of 63 ± 11% (n = 5, P < .05) against 48 ± 7% in the corresponding contralateral brain, indicating their hyperoxic status. In a different set of animals, 42 days post-inoculation, tumors had lower sO2 of 42 ± 5% against 49 ± 4% (n = 3, P < .05) in the contralateral side, indicating their hypoxic status. Upon CA4P administration, sO2 in 15 days post-inoculation tumors dropped from 61 ± 9% to 36 ± 1% (n = 4, P < .01) within one hour, then reverted to pre CA4P treatment values (63 ± 6%) and remained constant until the last observation time point of 6 hours. CONCLUSION: With the help of advanced post processing algorithms, MSOT was capable of monitoring the tumor growth and assessing hemodynamic changes upon administration of VDAs in orthotopic GBMs.
The use of an optical resolution photoacoustic microscopy (OR-PAM) system to evaluate the vascular disruptive effect of combretastatin A4 Phosphate (CA4P) on a murine orthotopic glioma with intact skull is described here. Second generation optical-resolution photoacoustic microscopy scanner with a 532 nm pulsed diode-pumped solid-state laser that specifically matches the absorption maximum of hemoglobin in tissues was used to image orthotopic glioma inoculated in mouse brain. Two-dimensional maps of brain vasculature with a lateral resolution of 5 μm and a depth of 700 μm at a field of view 5 × 4 mm were acquired on normal brain and glioma brain. Longitudinal imaging of the brain pre- and post-administration of CA4P, a FDA approved drug for solid tumors, enabled the monitoring of hemodynamic changes in tumor vasculature revealing the well documented vascular shutdown and recovery associated with this drug. Our study marks the beginning of potential prospects of this technology as an imaging tool for preclinical and clinical study of pathologies characterized by changes in the vasculature.
Mycobacterium tuberculosis is the causative agent of a pulmonary epidemic that is estimated to infect one-third of the world's population and that has an increased incidence of multidrug resistance. The evaluation of new chemical entities against M. tuberculosis is hampered by the lack of biological tools to help predict efficacy, from early drug development to clinical trials. As the rat is the animal species of choice in the pharmaceutical industry, we have developed a rat model of acute and chronic phases of M. tuberculosis infection for drug efficacy testing. In this model, we have evaluated the impact of tuberculosis drugs on T cell response using the enzyme-linked immunospot assay methodology. Infected rats treated with isoniazid (INH) or rifampin (RIF) responded to therapy, the potency of which was comparable to that seen in the mouse. Peripheral blood mononuclear cells from infected rats produced gamma interferon (IFN-␥) in response to RD-1 antigens, such as the 6-kDa early secretory antigen target (ESAT-6) and the 10-kDa culture filtrate protein (CFP-10). A decrease in IFN-␥ spot-forming cells (SFCs) was consistently observed in response to drug treatment. In both the acute-and chronic-phase models, the T cell response was more sensitive to ESAT-6 than to CFP-10. The SFC count in response to ESAT-6 appears to be an indicator of bacterial killing in the rat. Collectively, our data suggest that the ESAT-6 response could be used as a potential surrogate of drug efficacy in the rat and that such a readout could help shorten drug testing during preclinical development.Mycobacterium tuberculosis infection is among the world's leading infectious diseases, causing about 2 million deaths annually. The emergence of multidrug-resistant M. tuberculosis strains along with the increase of HIV coinfected cases worsens the situation (42). In countries with a high incidence of tuberculosis (TB), TB control programs rely on a diagnostic methods and drugs that have been developed decades ago and that are inadequate to effectively control the epidemic. The urgent need to develop new diagnostic tools as well as new therapeutic interventions is hampered by long clinical trials, where markers of infection and drug response are lacking (38).For decades, the tuberculin skin test (TST) has been used to diagnose TB (18). The TST measures cell-mediated immunity in the form of a delayed-type hypersensitivity response to the purified protein derivative (PPD), a crude mixture of antigens shared among M. tuberculosis, Mycobacterium bovis BCG, and several nontuberculous mycobacteria (NTM). As a result, the TST has lower specificity in populations with high BCG coverage and NTM exposure and shows poor sensitivity in immunocompromised individuals (30). The gamma interferon (IFN-␥) enzyme-linked immunospot (ELISpot) assay has emerged as an alternative to the TST. The assay consists of in vitro stimulation of peripheral blood mononuclear cells (PBMCs) using RD-1 antigens, the 6-kDa early secretory antigen target (ESAT-6) and the 10-kDa cul...
Pharmacokinetics of Gd(DO3A-Lys), a macrocyclic gadolinium-based magnetic resonance imaging (MRI) contrast agent functionalized with a lysine derivative, was studied in Wistar rats. Kinetic data were fitted using a two-compartment model and revealed Gd(DO3A-Lys) to have a distribution half-life, t1/2 (α), of 1.3 min, an elimination half-life, t1/2 (β), of 24.9 min and a large volume of distribution, VD , of 0.49 L/kg indicative of the agent being able to rapidly distribute into tissues and organs. Contrast-enhanced magnetic resonance angiography (CE-MRA) in an orthotopic U87MG glioma mouse model demonstrated considerable enhancement of both the tumor and surrounding vasculature after intravenous administration of Gd(DO3A-Lys). Applying dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in the glioma of different sizes further showed distinct uptake characteristics and patterns of enhancement, which suggests the potential for differentiating changes at different stages of tumor growth. Our results indicate that Gd(DO3A-Lys) could be a promising candidate for glioma MR imaging.
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