The role of parasite sanctuary sites and interaction with Kupffer cells in treatment failure of Visceral Leishmaniasis

Visceral Leishmaniasis (VL) or Kala-Azar is a neglected tropical disease caused by Leishmania parasites that are able to survive inside macrophages. Miltefosine (MIL) is an oral drug used to treat VL patients but is increasingly failing to permanently clear parasites from the patient. Parasites from these relapse patients do not seem to display an increased resistance to the drug but are able to modify the immune system to promote survival inside macrophages even in conditions where the drug is administered.The impact of drug treatment on parasite survival will be evaluated in various tissues using molecular and imaging technologies in rodent models of VL following a natural parasite transmission. Recently, two syngeneic strains of L. infantum were selected with different levels of sensitivity to MIL-treatment in vivo. The resistant strain (and its sensitive counterpart) was made bioluminescent by introduction of the luciferase enzyme (PpyRE9). The use of bioluminescence imaging (BLI) allows the non-invasive evaluation of the parasite burden and distribution in various tissues and allows assessing the impact of MIL-treatment in vivo. The transgenic parasites will additionally be provided with a fluorescent marker (DsRed or TagGFP2) for detecting parasites by flow cytometry. This project aims to gain insights into the multifactorial causes of MIL-therapy failure and will focus specifically on the impact of the activation state of Kupffer cells (KC) and the recruitment of neutrophils. Infection with the two transgenic parasite lines will be followed by in vivo imaging in (i) KC-reporter (Clec4f-YFP DTR) mice in which KCs can be detected and enriched through their YFP signal and (ii) Genista mice in which a recessive mutation is responsible for a neutropenic condition with absence of mature neutrophils. This approach will allow to gain insights into the cell-based immunological basis of treatment failure. By transcriptional studies, this study will also allow us to identify the involved immunological pathways and potentially allow the design of host-directed therapies to reduce the risk of relapse. The multidisciplinary approach will lead to new insights into the complex interactions between the parasite, the host and the drug and will allow the formulation of recommendations for treatment against VL.

Keywords:INFECTIONS, PARASITOLOGY, IMMUNOLOGY, LEISHMANIA

Disciplines:Microbiology, Immunology, Veterinary medicine