Tissue and host species-specific transcriptional changes in models of experimental visceral leishmaniasis

Abstract

Background: Human visceral leishmaniasis, caused by infection with Leishmania donovani or L. infantum, is a potentially fatal disease affecting 50,000-90,000 people yearly in 75 disease endemic countries, with more than 20,000 deaths reported. Experimental models of infection play a major role in understanding parasite biology, host-pathogen interaction, disease pathogenesis, and parasite transmission. In addition, they have an essential role in the identification and pre-clinical evaluation of new drugs and vaccines. However, our understanding of these models remains fragmentary. Although the immune response to Leishmania donovani infection in mice has been extensively characterized, transcriptomic analysis capturing the tissue-specific evolution of disease has yet to be reported. Methods: We provide an analysis of the transcriptome of spleen, liver and peripheral blood of BALB/c mice infected with L. donovani. Where possible, we compare our data in murine experimental visceral leishmaniasis with transcriptomic data in the public domain obtained from the study of L. donovani-infected hamsters and patients with human visceral leishmaniasis. Digitised whole slide images showing the histopathology in spleen and liver are made available via a dedicated website, www.leishpathnet.org. Results: Our analysis confirms marked tissue-specific alterations in the transcriptome of infected mice over time and identifies previously unrecognized parallels and differences between murine, hamster and human responses to infection. We show commonality of interferon-regulated genes whilst confirming a greater activation of type 2 immune pathways in infected hamsters compared to mice. Cytokine genes and genes encoding immune checkpoints were markedly tissue specific and dynamic in their expression, and pathways focused on non-immune cells reflected tissue specific immunopathology. Our data also addresses the value of measuring peripheral blood transcriptomics as a potential window into underlying systemic disease. Conclusions: Our transcriptomic data, coupled with histopathologic analysis of the tissue response, provide an additional resource to underpin future mechanistic studies and to guide clinical research.

Transcriptional blood signatures for active and amphotericin B treated visceral leishmaniasis in India

“…Given the many studies that have identified the importance of regulatory IL-10 in VL pathogenesis [54, 56–59], it was of some interest in our study that IL10 was not identified as a top differentially expressed gene or as a significantly enriched signalling pathway in either comparison of active cases with healthy controls, or of active cases with treated cases. Nor did we observed perturbation of IL10R as has been reported in experimental transcriptional profiling studies of VL [24]. Indeed, downregulated expression of the type 2 cytokine gene IL4 was the strongest response associated with effective cure in liposome-encapsulated amphotericin B treated cases, in line with previous studies showing that IL-4 levels were two-fold higher in VL patients who had failed treatment compared to previously untreated patients, whereas IL-10 levels were comparable in both [58].…”

“…Cxcl9, Gbp1 (encoding the interferon-γ-induced guanylate binding protein GBP1 identified here as one of the top 10 induced genes when comparing active versus treated cases), and Ifng were also identified as part of a common signature of 26 genes upregulated in blood, spleen and liver throughout the course of experimental infection with L . donovani in susceptible BALB/c mice, with Cxcl9 and Gbp1 reported as hub genes from a STRING analysis [24].…”

“…More recently, whole blood transcriptional profiling has been used to study human host responses to protozoan pathogens such as malaria [20, 21] and Chagas disease caused by Trypanosoma cruzi [22, 23]. Expression profiling has also been applied in the context of animal models [24–26] and in human studies [15, 27–29] of the leishmaniases. In particular, whole blood transcriptomics was used to compare expression profiles in patients with active VL caused by L .…”

Leishmaniasis immunopathology—impact on design and use of vaccines, diagnostics and drugs

“…In human VL, comparisons between the whole blood transcriptome of healthy endemic controls with active cases, drug-cured cases and asymptomatic individuals have been reported from Brazil [45] and India [46]. Transcriptomic analysis of the splenic, hepatic and blood response to infection over time has been performed in mice [47] and for spleen only in hamsters [48]. High level analysis of these various reports indicates (i) IFN signatures are a prominent feature of infection; (ii) Th2 responses are variably represented with a bias to more severe disease; iii) changes associated with cell cycle, lipid metabolism, angiogensis and hematological disturbances are evident in active disease and reduced after treatment; iv) treated patients, at least over the time period of study, fail to fully return to a homeostatic state.…”

Comparison of whole blood and spleen transcriptional signatures over the course of an experimental malaria infection

“…Instead, most studies rely on the detection of immune signatures in peripheral blood to evaluate the performance of vaccine candidates 5,6 , or to identify markers of protective immunity or pathology in humans 7–9 . Despite this obvious discrepancy and mounting evidence of tissue-specific differences in gene expression during immune responses 10,11 , there has not been a comprehensive analysis of simultaneous measurements from blood and spleen over the course of a Plasmodium infection to evaluate how similar or dissimilar the immune signatures in these two tissues are.…”