Transcriptional signatures in human macrophage-like cells infected by Leishmania infantum, Leishmania major and Leishmania tropica.

Background: In the Mediterranean basin, three Leishmania species have been identified: L. infantum, L. major and L. tropica, causing zoonotic visceral leishmaniasis (VL), zoonotic cutaneous leishmaniasis (CL) and anthroponotic CL, respectively. Despite animal models and genomic/transcriptomic studies provided important insights, the pathogenic determinants modulating the development of VL and CL are still poorly understood. This work aimed to identify host transcriptional signatures shared by cells infected with L. infantum, L. major, and L. tropica, as well as specific transcriptional signatures elicited by parasites causing VL (i.e., L. infantum) and parasites involved in CL (i.e., L. major, L. tropica). Methodology/Principal findings: U937 cells differentiated into macrophage-like cells were infected with L. infantum, L. major and L. tropica for 24h and 48h, and total RNA was extracted. RNA sequencing, performed on an Illumina NovaSeq 6000 platform, was used to evaluate the transcriptional signatures of infected cells with respect to non-infected cells at both time points. The EdgeR package was used to identify differentially expressed genes (fold change > 2 and FDR-adjusted p-values < 0.05). Then, functional enrichment analysis was employed to identify the enriched ontology terms in which these genes are involved. At 24h post-infection, a common signature of 463 dysregulated genes shared among all infection conditions was recognized, while at 48h post-infection the common signature was reduced to 120 genes. Aside from a common transcriptional response, we evidenced different upregulated functional pathways characterizing L. infantum-infected cells, such as VEGFA-VEGFR2 and NFE2L2-related pathways, indicating vascular remodeling and reduction of oxidative stress as potentially important factors for visceralization. Conclusions: The identification of pathways elicited by parasites causing VL or CL could lead to new therapeutic strategies for leishmaniasis, combining the canonical anti-leishmania compounds with host-directed therapy. Author summary: Leishmaniasis is a zoonosis caused by the intracellular parasite of the genus Leishmania. In the Mediterranean region, the human disease can be present mainly in two forms: cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL), which can be fatal if untreated. The clinical presentation of the disease depends on the parasite species and host characteristics. However, the molecular mechanisms underlying the development of the visceral form of leishmaniasis are not yet fully understood. In this study, we have determined the gene expression profile in cells infected by three Leishmania species (L. infantum, L. major, L. tropica) responsible for different forms of the disease. The results have allowed us to identify an expression profile (and the related pathways) shared by cells infected by all Leishmania species. Aside this common response, we also identified a transcriptional response distinguishing cells infected by L. infantum, L. major or L. tropica, as well as the relevant pathways in which these genes participate. Therefore, our results contribute to the knowledge of the host cell mechanisms that are activated along infection with different Leishmania species causing different forms of the disease and, therefore, may help develop new host-directed therapy for Leishmaniasis. [ABSTRACT FROM AUTHOR]