Abstract
Visceral leishmaniasis is an infectious parasitic disease caused by the protozoan parasites Leishmania donovani and Leishmania infantum. The drugs currently used to treat visceral leishmaniasis suffer from toxicity and the emergence of parasite resistance, and so a better solution would be the development of an effective subunit vaccine; however, no approved vaccine currently exists. The comparative testing of a large number of vaccine candidates requires a quantitative and reproducible experimental murine infection model, but the parameters that influence infection pathology have not been systematically determined. To address this, we have established an infection model using a transgenic luciferase-expressing L. donovani parasite and longitudinally quantified the infections using in vivo bioluminescent imaging within individual mice. We examined the effects of varying the infection route, the site of adjuvant formulation administration, and standardised the parasite preparation and dose. We observed that the increase in parasite load within the liver during the first few weeks of infection was directly proportional to the parasite number in the initial inoculum. Finally, we show that immunity can be induced in pre-exposed animals that have resolved an initial infection. This murine infection model provides a platform for systematic subunit vaccine testing against visceral leishmaniasis.
Highlights
Visceral leishmaniasis is an infectious parasitic disease caused by the protozoan parasites Leishmania donovani and Leishmania infantum
We establish a reproducible and highly quantitative murine infection model for evaluating vaccine candidates for visceral leishmaniasis (VL) by selecting a transgenic L. donovani parasite expressing the firefly luciferase and investigating the effects of experimental parameters that are known to influence the progression of infection, and which could affect comparative vaccine testing
To establish a reproducible and quantitative murine infection model of VL, we transfected the LV9 strain of L. donovani and selected a recombinant parasite that constitutively expressed the firefly luciferase gene to permit tracking and quantification of infected mice using in vivo imaging
Summary
Visceral leishmaniasis is an infectious parasitic disease caused by the protozoan parasites Leishmania donovani and Leishmania infantum. Modified immuno-compromised mice such as Rag[1] and Rag2-deficient mice have been used successfully as models for VL and unlike the BALB/c strain, these mice more closely reflect human disease pathology since they do not clear parasites from the liver[25,26,27,28] Uses of these immunodeficient animals, are generally limited to studies involving drug trials or in vivo parasite propagation since they are incapable of generating adaptive immune responses. Because of their genetic tractability and characterization, mice have become a useful model organism to characterise host factors and immune responses to Leishmania spp. infections Despite these advantages, variations in infection pathology within a cohort of infected animals and the difficulty of repeatedly quantifying parasite loads in visceral organs within an individual animal are challenges to address for comparative vaccinology studies. We establish a reproducible and highly quantitative murine infection model for evaluating vaccine candidates for VL by selecting a transgenic L. donovani parasite expressing the firefly luciferase and investigating the effects of experimental parameters that are known to influence the progression of infection, and which could affect comparative vaccine testing
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