Macrophage and T-Cell Gene Expression in a Model of Early Infection with the Protozoan Leishmania chagasi

Abstract

Visceral leishmaniasis is a potentially fatal infectious disease caused by the protozoan parasite Leishmania infantum/chagasi in the New World, or by L. donovani or L. infantum/chagasi in the Old World. Infection leads to a variety of outcomes ranging from asymptomatic infection to active disease, characterized by fevers, cachexia, hepatosplenomegaly and suppressed immune responses. We reasoned that events occurring during the initial few hours when the parasite encounters cells of the innate and adaptive immune systems are likely to influence the eventual immune response that develops. Therefore, we performed gene expression analysis using Affymetrix U133Plus2 microarray chips to investigate a model of early infection with human monocyte-derived macrophages (MDMs) challenged with wild-type L. chagasi parasites, with or without subsequent co-culture with Leishmania-naïve, autologous T-cells. Microarray data generated from total RNA were analyzed with software from the Bioconductor Project and functional clustering and pathway analysis were performed with DAVID and Gene Set Enrichment Analysis (GSEA), respectively. Many transcripts were down-regulated by infection in cultures containing macrophages alone, and the pattern indicated a lack of a classically activated phenotype. By contrast, the addition of autologous Leishmania-naïve T cells to infected macrophages resulted in a pattern of gene expression including many markers of type 1 immune cytokine activation (IFN-γ, IL-6, IL-1α, IL-1β). There was simultaneous up-regulation of a few markers of immune modulation (IL-10 cytokine accumulation; TGF-β Signaling Pathway). We suggest that the initial encounter between L. chagasi and cells of the innate and adaptive immune system stimulates primarily type 1 immune cytokine responses, despite a lack of classical macrophage activation. This local microenvironment at the site of parasite inoculation may determine the initial course of immune T-cell development.

Genome-Wide Association Study of Cell-Mediated Response in Dogs Naturally Infected by Leishmania infantum

“…Previous studies have shown that L. infantum downregulates expression of mediators from innate and adaptive immunity in the early stage of infection in phagocytes (6,10,16). These findings are consistent with the idea that an early suppression would prevent T cell activation and would allow a silent establishment of infection.…”

“…Thus, mature APC are able to activate naive T lymphocytes and instruct T helper 1 (Th1) differentiation during antigen presentation. Th1 clones release interferon gamma (IFN-␥) and TNF-␣, which attract macrophages, activate antileishmanial mechanisms, and induce more proinflammatory cytokines (12)(13)(14)(15)(16). The adaptive response to canine Leishmania infection is markedly mixed, since L. infantum induces Th1 and T regulatory (Treg) responses.…”

Blood Transcriptional Profiling Reveals Immunological Signatures of Distinct States of Infection of Humans with Leishmania infantum

“…Moreover, macrophage cultures infected with species of L . donovani complex exhibit an overall suppression of gene expression, suggesting a failure of proper macrophage activation [18,42]. However, the regulation of gene expression in MDM infected with L .…”

“…However, the regulation of gene expression in MDM infected with L . chagasi was significantly impacted by the co-culture with autologous Leishmania-naïve T cells [18], suggesting that the inflammatory milieu of complex microenvironments such as the infection foci and peripheral blood influence the transcriptional programs of immune cells. Indeed, gene expression profiling of liver-resident macrophages (Kuppfer cells) from mice infected with L .…”

Human Dendritic Cells Exhibit a Pronounced Type I IFN Signature following Leishmania major Infection That Is Required for IL-12 Induction

“…Several studies have utilized microarray technologies to study global gene expression profiles of host cells during Leishmania infection, in both murine model (34-36) and human systems (9, 37-39). Here, we build upon a previously published microarray dataset that explored the transcriptional profile of L. major infected DCs, representing 7 donors pooled together at a single time point of infection (16 hrs) (9), by analyzing the expression profiles of 3 additional independent donors across early infection time points (2, 4, 8, and 24 hrs).…”