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Chagas disease is a zoonosis caused by the protozoan parasite Trypanosoma cruzi. Clinical outcomes range from long-term asymptomatic carriage to cardiac, digestive, neurological and composite presentations that can be fatal in both acute and chronic stages of the disease. Studies of T. cruzi in animal models, principally mice, have informed our understanding of the biological basis of this variability and its relationship to infection and host response dynamics. Hamsters have higher translational value for many human infectious diseases, but they have not been well developed as models of Chagas disease. We transposed a real-time bioluminescence imaging system for T. cruzi infection from mice into female Syrian hamsters (Mesocricetus auratus). This enabled us to study chronic tissue pathology in the context of spatiotemporal infection dynamics. Acute infections were widely disseminated, whereas chronic infections were almost entirely restricted to the skin and subcutaneous adipose tissue. Neither cardiac nor digestive tract disease were reproducible features of the model. Skeletal muscle had only sporadic parasitism in the chronic phase, but nevertheless displayed significant inflammation and fibrosis, features also seen in mouse models. Whereas mice had normal locomotion, all chronically infected hamsters developed hindlimb muscle hypertonia and a gait dysfunction resembling spastic diplegia. With further development, this model may therefore prove valuable in studies of peripheral nervous system involvement in Chagas disease. Author summary: Chagas disease is a caused by American trypanosomes (Trypanosoma cruzi). These are microscopic parasites that circulate in wild mammals across most of the Americas and can also be transmitted to humans. Much of our knowledge about how T. cruzi causes Chagas disease comes from studies of infections in mice, but the data do not capture the full range of clinical outcomes seen in humans. For many other pathogens the hamster has proved to be a valuable model of human infections. We therefore aimed to apply some of the latest advances in T. cruzi infection imaging technology to studies in this alternative experimental model. In the early stages, parasites were widely disseminated throughout the body, but after several months parasites became almost entirely restricted to the skin. Hamsters did not show signs of heart or gut disease, which are common in humans, but they did develop skeletal muscle pathology. Stiffness in the hindlimbs grew progressively worse and resulted in a visibly altered gait, suggestive of damage to the nervous system. With further development, this model may therefore prove valuable in studies of peripheral nervous system involvement in Chagas disease. [ABSTRACT FROM AUTHOR]

Chagas disease is caused by Trypanosoma cruzi, a protozoan parasite that displays considerable genetic diversity. Infections result in a range of pathological outcomes, and different strains can exhibit a wide spectrum of anti-parasitic drug tolerance. The genetic determinants of infectivity, virulence and therapeutic susceptibility remain largely unknown. As experimental tools to address these issues, we have generated a panel of bioluminescent:fluorescent parasite strains that cover the diversity of the T. cruzi species. These reporters allow spatio-temporal infection dynamics in murine models to be monitored in a non-invasive manner by in vivo imaging, provide a capability to detect rare infection foci at single-cell resolution, and represent a valuable resource for investigating virulence and host:parasite interactions at a mechanistic level. Importantly, these parasite reporter strains can also contribute to the Chagas disease drug screening cascade by ensuring that candidate compounds have pan-species in vivo activity prior to being advanced into clinical testing. The parasite strains described in this paper are available on request. Author summary: Chagas disease results from infection with the protozoan parasite Trypanosoma cruzi and is a major public health problem throughout Latin America. T. cruzi is a genetically diverse species and infection can result in a wide range of pathological outcomes, mainly associated with the heart and/or digestive tract. Research on Chagas disease, ranging from fundamental biology to drug development, has been greatly aided by the availability of genetically modified parasite reporter strains that express bioluminescent:fluorescent fusion proteins. In combination with mouse models and imaging technology, these strains allow infections to be monitored in real-time, with high sensitivity, and infection foci to be visualised at single-cell resolution. Here, we describe an extensive panel of bioluminescent and fluorescent strains that cover the diversity of the T. cruzi species. These reporter strains, that are available on request, should have wide utility in many areas of Chagas disease research. In particular, as part of the drug development screening programme, they can be used to ensure that candidate compounds have in vivo activity across the species prior to being advanced into clinical testing. [ABSTRACT FROM AUTHOR]

Background: Human African trypanosomiasis is caused by infection with parasites of the Trypanosoma brucei species complex, and threatens over 70 million people in sub-Saharan Africa. Development of new drugs is hampered by the limitations of current rodent models, particularly for stage II infections, which occur once parasites have accessed the CNS. Bioluminescence imaging of pathogens expressing firefly luciferase (emission maximum 562 nm) has been adopted in a number of in vivo models of disease to monitor dissemination, drug-treatment and the role of immune responses. However, lack of sensitivity in detecting deep tissue bioluminescence at wavelengths below 600 nm has restricted the wide-spread use of in vivo imaging to investigate infections with T. brucei and other trypanosomatids. Methodology/Principal findings: Here, we report a system that allows the detection of fewer than 100 bioluminescent T. brucei parasites in a murine model. As a reporter, we used a codon-optimised red-shifted Photinus pyralis luciferase (PpyRE9H) with a peak emission of 617 nm. Maximal expression was obtained following targeted integration of the gene, flanked by an upstream 5′-variant surface glycoprotein untranslated region (UTR) and a downstream 3′-tubulin UTR, into a T. brucei ribosomal DNA locus. Expression was stable in the absence of selective drug for at least 3 months and was not associated with detectable phenotypic changes. Parasite dissemination and drug efficacy could be monitored in real time, and brain infections were readily detectable. The level of sensitivity in vivo was significantly greater than achievable with a yellow firefly luciferase reporter. Conclusions/Significance: The optimised bioluminescent reporter line described here will significantly enhance the application of in vivo imaging to study stage II African trypanosomiasis in murine models. The greatly increased sensitivity provides a new framework for investigating host-parasite relationships, particularly in the context of CNS infections. It should be ideally suited to drug evaluation programmes. [ABSTRACT FROM AUTHOR]