Dual Transcriptome Profiling ofLeishmania-Infected Human Macrophages Reveals Distinct Reprogramming Signatures

Abstract

Macrophages are mononuclear phagocytes that constitute a first line of defense against pathogens. While lethal to many microbes, they are the primary host cells of Leishmania spp. parasites, the obligate intracellular pathogens that cause leishmaniasis. We conducted transcriptomic profiling of two Leishmania species and the human macrophage over the course of intracellular infection by using high-throughput RNA sequencing to characterize the global gene expression changes and reprogramming events that underlie the interactions between the pathogen and its host. A systematic exclusion of the generic effects of large-particle phagocytosis revealed a vigorous, parasite-specific response of the human macrophage early in the infection that was greatly tempered at later time points. An analogous temporal expression pattern was observed with the parasite, suggesting that much of the reprogramming that occurs as parasites transform into intracellular forms generally stabilizes shortly after entry. Following that, the parasite establishes an intracellular niche within macrophages, with minimal communication between the parasite and the host cell later during the infection. No significant difference was observed between parasite species transcriptomes or in the transcriptional response of macrophages infected with each species. Our comparative analysis of gene expression changes that occur as mouse and human macrophages are infected by Leishmania spp. points toward a general signature of the Leishmania-macrophage infectome.

Exploitation of the Host Cell Membrane Fusion Machinery by Leishmania Is Part of the Infection Process

“…major or L . amazonensis leads to the up-regulation of Syt II, VI, and VIII [20]. The underlying mechanism, including the parasite factors and/or host proteins involved, and the repercussions on PV ( p arasitophorous v acuole) formation and infection outcome have yet to be uncovered.…”

SILAC-based quantitative proteomics reveals pleiotropic, phenotypic modulation in primary murine macrophages infected with the protozoan pathogenLeishmania donovani

“…These M1 and M2 phenotypes represent the extremes of a continuous spectrum of polarisation states [7]. Even though both the initial Leishmania infection through the bite of infected sand flies and the later acute stages of the disease are characterised by inflammation of the infected tissue [8, 9], Leishmania thrives in these environments by efficiently dampening the pro-inflammatory response of its infected host cell, possibly by exploiting developmental programs underlying macrophage phenotypic plasticity [10].…”

“…However, this ideal concept of ‘macrophage deactivation’ upon Leishmania infection is clearly an oversimplification, as the macrophage response to infection under clinically more relevant conditions can depend on many parameters, including the host cell differentiation state, the tissue context, and parasite species or even strain [19, 20]. Systems-level, ‘omics’ approaches revealed the complex interface between the parasite and the macrophage and shed important new light on the host cell response to Leishmania infection, particularly at the transcript level [8, 9, 19, 21–27]. However, transcript abundance does not always correlate with protein levels and thus may not give an accurate picture of the cellular phenotype.…”

Dual RNA-seq reveals no plastic transcriptional response of the coccidian parasiteEimeria falciformisto host immune defenses

“…We used a "dual RNA-seq" approach, i.e., we simultaneously assessed the transcriptomes of host and parasite in biological samples containing both species [28][29][30][31][32]. Applying this to an infection of E. falciformis in the mouse, we produced host and parasite transcriptomes from the same samples, tissue, and time-points.…”