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Antimony resistant Leishmania donovani but not sensitive ones drives greater frequency of potent T-regulatory cells upon interaction with human PBMCs: role of IL-10 and TGF-? in early immune response.

ABSTRACT: In India the sand fly, Phlebotomus argentipes, transmitted parasitic disease termed kala-azar is caused by Leishmania donovani (LD) in humans. These immune-evading parasites have increasingly developed resistance to the drug sodium antimony gluconate in endemic regions. Lack of early diagnosis methods for the disease limits the information available regarding the early interactions of this parasite with either human tissues or cell lineages. We reasoned that peripheral blood mononuclear cells (PBMCs) from healthy human beings could help compare some of their immune signatures once they were exposed for up to 8 days, to either pentavalent antimony sensitive (Sb(S)-LD) or resistant (Sb(R)-LD) Leishmania donovani isolates. At day 2, PBMC cultures exposed to Sb(S)-LD and Sb(R)-LD stationary phase promastigotes had four and seven fold higher frequency of IL-10 secreting monocyte-macrophage respectively, compared to cultures unexposed to parasites. Contrasting with the CD4(+)CD25-CD127- type-1 T-regulatory (Tr1) cell population that displayed similar features whatever the culture conditions, there was a pronounced increase in the IL-10 producing CD4(+)CD25(+)CD127low/- inducible T-regulatory cells (iTregs) in the PBMC cultures sampled at day 8 post addition of Sb(R)-LD. Sorted iTregs from different cultures on day 8 were added to anti-CD3/CD28 induced naïve PBMCs to assess their suppressive ability. We observed that iTregs from Sb(R)-LD exposed PBMCs had more pronounced suppressive ability compared to Sb(S)-LD counterpart on a per cell basis and is dependent on both IL-10 and TGF-?, whereas IL-10 being the major factor contributing to the suppressive ability of iTregs sorted from PBMC cultures exposed to Sb(S)-LD. Of note, iTreg population frequency value remained at the basal level after addition of genetically modified Sb(R)-LD lacking unique terminal sugar in surface glycan. Even with limitations of this artificial in vitro model of L. donovani-human PBMC interactions, the present findings suggest that Sb(R)-LD have higher immunomodulatory capacity which may favour aggressive pathology.

SUBMITTER: Guha R

PROVIDER: S-EPMC4102415 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature

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Antimony resistant Leishmania donovani but not sensitive ones drives greater frequency of potent T-regulatory cells upon interaction with human PBMCs: role of IL-10 and TGF-β in early immune response.

Guha Rajan R Das Shantanabha S Ghosh June J Sundar Shyam S Dujardin Jean Claude JC Roy Syamal S

PLoS neglected tropical diseases 20140717 7

In India the sand fly, Phlebotomus argentipes, transmitted parasitic disease termed kala-azar is caused by Leishmania donovani (LD) in humans. These immune-evading parasites have increasingly developed resistance to the drug sodium antimony gluconate in endemic regions. Lack of early diagnosis methods for the disease limits the information available regarding the early interactions of this parasite with either human tissues or cell lineages. We reasoned that peripheral blood mononuclear cells (P ...[more]

PMID: 25032977

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Project description:Antimonials (Sb) were used for decades for chemotherapy of visceral leishmaniasis (VL). Now abandoned in the Indian subcontinent (ISC) because of Leishmania donovani resistance, this drug offers a unique model for understanding drug resistance dynamics. In a previous phylogenomic study, we found two distinct populations of L. donovani: the core group (CG) in the Gangetic plains and ISC1 in the Nepalese highlands. Sb resistance was only encountered within the CG, and a series of potential markers were identified. Here, we analyzed the development of resistance to trivalent antimonials (SbIII) upon experimental selection in ISC1 and CG strains. We observed that (i) baseline SbIII susceptibility of parasites was higher in ISC1 than in the CG, (ii) time to SbIII resistance was higher for ISC1 parasites than for CG strains, and (iii) untargeted genomic and metabolomic analyses revealed molecular changes along the selection process: these were more numerous in ISC1 than in the CG. Altogether these observations led to the hypothesis that CG parasites are preadapted to SbIII resistance. This hypothesis was experimentally confirmed by showing that only wild-type CG strains could survive a direct exposure to the maximal concentration of SbIII The main driver of this preadaptation was shown to be MRPA, a gene involved in SbIII sequestration and amplified in an intrachromosomal amplicon in all CG strains characterized so far. This amplicon emerged around 1850 in the CG, well before the implementation of antimonials for VL chemotherapy, and we discuss here several hypotheses of selective pressure that could have accompanied its emergence.IMPORTANCE The "antibiotic resistance crisis" is a major challenge for scientists and medical professionals. This steady rise in drug-resistant pathogens also extends to parasitic diseases, with antimony being the first anti-Leishmania drug that fell in the Indian subcontinent (ISC). Leishmaniasis is a major but neglected infectious disease with limited therapeutic options. Therefore, understanding how parasites became resistant to antimonials is of commanding importance. In this study, we experimentally characterized the dynamics of this resistance acquisition and show for the first time that some Leishmania populations of the ISC were preadapted to antimony resistance, likely driven by environmental factors or by drugs used in the 19th century.

Project description:The inability of sodium antimony gluconate (SAG)-unresponsive kala-azar patients to clear Leishmania donovani (LD) infection despite SAG therapy is partly due to an ill-defined immune-dysfunction. Since dendritic cells (DCs) typically initiate anti-leishmanial immunity, a role for DCs in aberrant LD clearance was investigated. Accordingly, regulation of SAG-induced activation of murine DCs following infection with LD isolates exhibiting two distinct phenotypes such as antimony-resistant (Sb(R)LD) and antimony-sensitive (Sb(S)LD) was compared in vitro. Unlike Sb(S)LD, infection of DCs with Sb(R)LD induced more IL-10 production and inhibited SAG-induced secretion of proinflammatory cytokines, up-regulation of co-stimulatory molecules and leishmanicidal effects. Sb(R)LD inhibited these effects of SAG by blocking activation of PI3K/AKT and NF-kappaB pathways. In contrast, Sb(S)LD failed to block activation of SAG (20 microg/ml)-induced PI3K/AKT pathway; which continued to stimulate NF-kappaB signaling, induce leishmanicidal effects and promote DC activation. Notably, prolonged incubation of DCs with Sb(S)LD also inhibited SAG (20 microg/ml)-induced activation of PI3K/AKT and NF-kappaB pathways and leishmanicidal effects, which was restored by increasing the dose of SAG to 40 microg/ml. In contrast, Sb(R)LD inhibited these SAG-induced events regardless of duration of DC exposure to Sb(R)LD or dose of SAG. Interestingly, the inhibitory effects of isogenic Sb(S)LD expressing ATP-binding cassette (ABC) transporter MRPA on SAG-induced leishmanicidal effects mimicked that of Sb(R)LD to some extent, although antimony resistance in clinical LD isolates is known to be multifactorial. Furthermore, NF-kappaB was found to transcriptionally regulate expression of murine gammaglutamylcysteine synthetase heavy-chain (mgammaGCS(hc)) gene, presumably an important regulator of antimony resistance. Importantly, Sb(R)LD but not Sb(S)LD blocked SAG-induced mgammaGCS expression in DCs by preventing NF-kappaB binding to the mgammaGCS(hc) promoter. Our findings demonstrate that Sb(R)LD but not Sb(S)LD prevents SAG-induced DC activation by suppressing a PI3K-dependent NF-kappaB pathway and provide the evidence for differential host-pathogen interaction mediated by Sb(R)LD and Sb(S)LD.

Dataset Information

Antimony resistant Leishmania donovani but not sensitive ones drives greater frequency of potent T-regulatory cells upon interaction with human PBMCs: role of IL-10 and TGF-? in early immune response.

Publications

Antimony resistant Leishmania donovani but not sensitive ones drives greater frequency of potent T-regulatory cells upon interaction with human PBMCs: role of IL-10 and TGF-β in early immune response.

Similar Datasets

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