The effects of CCR7 and related signaling pathways on Leishmania major -infected human dendritic cells

Dissection of the macrophage response towards infection by the Leishmania-viral endosymbiont duo and dynamics of the type I interferon response

Leishmania RNA virus 1 (LRV1) is a double-stranded RNA virus found in some strains of the human protozoan parasite Leishmania, the causative agent of leishmaniasis, a neglected tropical disease. Interestingly, the presence of LRV1 inside Leishmania constitutes an important virulence factor that worsens the leishmaniasis outcome in a type I interferon (IFN)–dependent manner and contributes to treatment failure. Understanding how macrophages respond toward Leishmania alone or in combination with LRV1 as well as the role that type I IFNs may play during infection is fundamental to oversee new therapeutic strategies. To dissect the macrophage response toward infection, RNA sequencing was performed on murine wild-type and Ifnar-deficient bone marrow–derived macrophages infected with Leishmania guyanensis (Lgy) devoid or not of LRV1. Additionally, macrophages were treated with poly I:C (mimetic virus) or with type I IFNs. By implementing a weighted gene correlation network analysis, the groups of genes (modules) with similar expression patterns, for example, functionally related, coregulated, or the members of the same functional pathway, were identified. These modules followed patterns dependent on Leishmania, LRV1, or Leishmania exacerbated by the presence of LRV1. Not only the visualization of how individual genes were embedded to form modules but also how different modules were related to each other were observed. Thus, in the context of the observed hyperinflammatory phenotype associated to the presence of LRV1, it was noted that the biomarkers tumor-necrosis factor α (TNF-α) and the interleukin 6 (IL-6) belonged to different modules and that their regulating specific Src-family kinases were segregated oppositely. In addition, this network approach revealed the strong and sustained effect of LRV1 on the macrophage response and genes that had an early, late, or sustained impact during infection, uncovering the dynamics of the IFN response. Overall, this study contributed to shed light and dissect the intricate macrophage response toward infection by the Leishmania-LRV1 duo and revealed the crosstalk between modules made of coregulated genes and provided a new resource that can be further explored to study the impact of Leishmania on the macrophage response.

Identification of gene expression profiles in Leishmania major infection by integrated bioinformatics analyses

Gene expression profiling in mouse models of leishmaniasis has given useful information to understand the molecular pathways active in lesions and to discover new diagnostic/therapeutic targets. Although the host response plays a critical role in protection from leishmaniasis and promoting disease severity, there are still unexplained aspects in the mechanism of non-healing cutaneous lesions, which need biomarkers for both targeted- therapy and diagnosis. To address this, transcriptional profiling of the skin lesions obtained from BALB/c mice infected with Leishmania major and healthy skin from naïve mice were evaluated by bioinformatics analysis, and then the results were validated by Revers Transcriptase-PCR. Five genes among the up-regulated differentially expressed genes named FCGR4, CCL4, CXCL9, Arg1 and IL-1β were found to have relatively high diagnostic value for CL due to L. major. Pathway analysis revealed that Triggering Receptor Expressed On Myeloid Cells 1 (TREM1) signaling pathways are active in cutaneous lesions, providing new insights for the understanding and treatment of leishmaniasis.