Bacterial Thymidine Kinase as a Non-Invasive Imaging Reporter for Mycobacterium tuberculosis in Live Animals

Abstract

BackgroundBacteria can be selectively imaged in experimentally-infected animals using exogenously administered 1-(2′deoxy-2′-fluoro-β-D-arabinofuranosyl)-5-[125I]-iodouracil ([125I]-FIAU), a nucleoside analog substrate for bacterial thymidine kinase (TK). Our goal was to use this reporter and develop non-invasive methods to detect and localize Mycobacterium tuberculosis.Methodology/Principal Findings We engineered a M. tuberculosis strain with chromosomally integrated bacterial TK under the control of hsp60 - a strong constitutive mycobacterial promoter. [125I]FIAU uptake, antimicrobial susceptibilities and in vivo growth characteristics were evaluated for this strain. Using single photon emission computed tomography (SPECT), M. tuberculosis Phsp60 TK strain was evaluated in experimentally-infected BALB/c and C3HeB/FeJ mice using the thigh inoculation or low-dose aerosol infection models. M. tuberculosis Phsp60 TK strain actively accumulated [125I]FIAU in vitro. Growth characteristics of the TK strain and susceptibility to common anti-tuberculous drugs were similar to the wild-type parent strain. M. tuberculosis Phsp60 TK strain was stable in vivo and SPECT imaging could detect and localize this strain in both animal models tested.ConclusionWe have developed a novel tool for non-invasive assessment of M. tuberculosis in live experimentally-infected animals. This tool will allow real-time pathogenesis studies in animal models of TB and has the potential to simplify preclinical studies and accelerate TB research.

Noninvasive Determination of 2-[ 18 F]-Fluoroisonicotinic Acid Hydrazide Pharmacokinetics by Positron Emission Tomography in Mycobacterium tuberculosis-Infected Mice

“…S2 in the supplemental material). The live animals were then placed inside sealed biocontainment devices as described before (7,8), with the polyethylene-10 tubing extending through one of the ports of the biocontainment device. The device was seal tested, and a 1-ml insulin syringe was attached to the catheter hub to deliver radiotracer at the beginning of imaging.…”

Rifapentine Is Not More Active than Rifampin against Chronic Tuberculosis in Guinea Pigs

“…In addition, the greater intracellular accumulation of P relative to R (22), which may have rendered P-containing regimens more potent against predominantly intracellular TB infection in BALB/c mice relative to Rcontaining regimens (29,30), may not have provided an advantage in chronically infected guinea pigs, which harbor primarily extracellular bacilli within necrotic lung granulomas. A direct comparison of the antitubercular activities of RHZ and PHZ in C3HeB/FeJ mice (11,12), which, like guinea pigs, develop necrotic lung granulomas following M. tuberculosis infection but share common drug metabolism properties with BALB/c mice (26), could help determine the role of lung pathology on the potency of each combination regimen. Ultimately, protein-binding studies of each drug in guinea pigs and microdialysis studies of infected guinea pig lungs, or those of larger species, will be required to elucidate the protein-binding properties and penetration of each drug in necrotic lung lesions harboring persistent bacilli.…”

Noninvasive Pulmonary [ 18 F]-2-Fluoro-Deoxy- d -Glucose Positron Emission Tomography Correlates with Bactericidal Activity of Tuberculosis Drug Treatment

“…It could also represent an inherent limitation of [ 18 F]FDG-PET imaging. More-specific PET tracers, such as those measuring lymphoidassociated inflammation (25) or radiopharmaceutical or bioluminescence-based imaging biomarkers that directly label bacteria (5,8,14), are anticipated to provide better real-time information about bacterial burdens. However, unlike PET tracers, methods of directly labeling bacteria are currently limited to in vitro systems or experimentally infected animals.…”