Project description:We aimed at finding differently expressed genes in whole blood cells of African children with asymptomatic Plasmodium falciparum infection (A), uncomplicated malaria (U), severe malarial anemia (A) and cerebral malaria (Ce) compared one to another and to healthy children (Co). Understanding malarial immunopathology in the human host represents and enormous challenge for transcriptomic research. In this work, we used microarray and real-time RT-PCR technology to pursue deeper knowledge about the mechanisms underlying this disease in African children. To this end, we investigated the genomic transcriptional profiles in whole blood of healthy children and children with asymptomatic infection, uncomplicated malaria, malaria associated with severe anemia and cerebral malaria and compared them with previously published microarray results. We were able to discriminate between the different presentations of P. falciparum infection using supervised and unsupervised clustering of microarray data and unsupervised double-hierarchical clustering of real-time RT-PCR results of a set of 22 genes known to be expressed in at least one of the principal blood cell lineages. We further found considerable overlap between genes regulated in Kenyan and Gabonese children with symptomatic malaria, in contrast to adults with acute malaria from Cameroon. Different signatures for transcription factor binding sites in promoters of genes either up-regulated in symptomatic disease, specifically up-regulated in uncomplicated malaria or specifically down-regulated in cerebral malaria point out that similar gene expression in each of these clinical presentations is probably a result of common regulation at the transcriptional level. Immunoglobulin production, complement regulation and IFN beta signalling emerged as most discrepant features between uncomplicated malaria and all other investigated presentations, correlating with IRF7 and ISRE binding signatures in the corresponding genes. Down-regulation of several genes in cerebral malaria seems instead to be a response to hypoxia orchestrated by AhRF, GABP and HIF1 transcription factors. ARG1, BPI, CD163, IFI27, HP and TNFAIP6 transcript levels correlated positively with lactatemia and inversely with hemoglobin concentration and should be evaluated as prognostic markers to direct early therapeutic measures and prevent malarial disease evolution and death.
Project description:Malaria infection triggers vigorous host immune responses; however, the parasite ligands, host receptors and the signaling pathways responsible for these reactions remain unknown or controversial. Malaria parasites primarily reside within red blood cells (RBCs), thereby hiding themselves from direct contact and recognition by host immune cells. Host responses to malaria infection are very different from those elicited by bacterial and viral infections and the host receptors recognizing parasite ligands have been elusive. Here we investigated mouse genome-wide transcriptional responses to infections with two strains of Plasmodium yoelii (N67 and N67C) and discovered differences in innate response pathways corresponding to strain-specific disease phenotypes. Using in vitro RNAi gene knockdown and knockout mice, we demonstrated that a strong IFN-I response triggered by RNA Polymerase III and melanoma differentiation-associated protein 5 (MDA5), not Toll-like receptors (TLRs), binding of parasite DNA/RNA contributed to a decline of parasitemia in N67-infected mice. We showed that conventional dendritic cells were the major sources of early IFN-I, and that surface expression of phosphatidylserine (PS) on infected RBC (iRBC) might promote their phagocytic uptake, leading to the release of parasite ligands and the IFN-I response in N67 infection. In contrast, an elevated inflammatory response mediated by CD14/TLR and p38 signaling played a role in disease severity and early host death in N67C-infected mice. In addition to identifying cytosolic DNA/RNA sensors and signaling pathways previously unrecognized in malaria infection, our study demonstrates the importance of parasite genetic backgrounds in malaria pathology and provides important information for studying human malaria pathogenesis. Spleen RNA from mice, 4 days post infection with Plasmodium yoelii (strain N67 or N67C), or mock infection (N). Replicates from 6 individual mice per condition.
Project description:Malaria infection triggers vigorous host immune responses; however, the parasite ligands, host receptors and the signaling pathways responsible for these reactions remain unknown or controversial. Malaria parasites primarily reside within red blood cells (RBCs), thereby hiding themselves from direct contact and recognition by host immune cells. Host responses to malaria infection are very different from those elicited by bacterial and viral infections and the host receptors recognizing parasite ligands have been elusive. Here we investigated mouse genome-wide transcriptional responses to infections with two strains of Plasmodium yoelii (N67 and N67C) and discovered differences in innate response pathways corresponding to strain-specific disease phenotypes. Using in vitro RNAi gene knockdown and knockout mice, we demonstrated that a strong IFN-I response triggered by RNA Polymerase III and melanoma differentiation-associated protein 5 (MDA5), not Toll-like receptors (TLRs), binding of parasite DNA/RNA contributed to a decline of parasitemia in N67-infected mice. We showed that conventional dendritic cells were the major sources of early IFN-I, and that surface expression of phosphatidylserine (PS) on infected RBC (iRBC) might promote their phagocytic uptake, leading to the release of parasite ligands and the IFN-I response in N67 infection. In contrast, an elevated inflammatory response mediated by CD14/TLR and p38 signaling played a role in disease severity and early host death in N67C-infected mice. In addition to identifying cytosolic DNA/RNA sensors and signaling pathways previously unrecognized in malaria infection, our study demonstrates the importance of parasite genetic backgrounds in malaria pathology and provides important information for studying human malaria pathogenesis.
Project description:The diversity of human immune responses to P. falciparum is unknown and yet immune decision-making likely dictates outcome of infection We infected 15 malaria-naïve human volunteers with P. falciparum and used longitudinal whole blood transcriptional profiling to independently analyse the immune response in every volunteer
Project description:Analysis of blood samples taken throughout the acute phase of infection from mice infected with avirulent P. chabaudi AS strain or virulent CB strain The influence of parasite genetic factors on immune responses and development of severe pathology of malaria is largely unknown. In this study, we performed genome-wide transcriptomic profiling of whole blood during blood-stage infections of two strains of the rodent malaria parasite Plasmodium chabaudi that differ in virulence. We identified several transcriptomic signatures associated with the virulent infection, including signatures for lung inflammation, stronger and prolonged anemia and platelet aggregation. The latter two signatures were detected prior to pathology. The anemia signature indicated deregulation of host erythropoiesis, and the lung inflammation signature was linked to increased neutrophil infiltration, more cell death and greater parasite sequestration in the lungs. This comparative whole-blood transcriptomics profiling of virulent and avirulent malaria infections shows the validity of this approach to inform severity of malarial infection and provide insight into pathogenic mechanisms.
Project description:Comparative analysis of Genome wide expression was performed to demonstrate diagnostic potential of expression profiling and to identify host response genes in scrub typhus. The results showed that there is a unique expression pattern in peripheral blood leukocytes of scrub typhus infected patients that could discriminate scrub typhus from the other infections and also provided insight into host transcriptional responses to this paticular infection. Genome-wide expression in peripheral blood mononuclear cells (PBMCs) from patients with scrub typhus were compared to those from healthy control and from patients with dengue fever, murine typhus or malaria.
Project description:Cumulative malaria parasite exposure in endemic regions often results in the acquisition of partial immunity and asymptomatic infections. There is limited information on how host-parasite interactions mediate maintenance of chronic symptomless infections that sustain malaria transmission. Here, we have determined the gene expression profiles of the parasite population and the corresponding host peripheral blood mononuclear cells (PBMCs) from 21 children (<15 years). We compared children who were defined as uninfected, asymptomatic and those with febrile malaria. Children with asymptomatic infections had a parasite transcriptional profile characterized by a bias toward trophozoite stage (~12 hours-post invasion) parasites and low parasite levels, while earlier ring stage parasites were characteristic of febrile malaria. The host response of asymptomatic children was characterized by downregulated transcription of genes associated with inflammatory responses, compared with children with febrile malaria, which may lead to less cytoadherence of more mature parasite stages. Interestingly, the host responses during febrile infections that followed an asymptomatic infection featured stronger inflammatory responses, whereas the febrile host responses from previously uninfected children featured increased humoral immune responses. The priming effect of prior asymptomatic infection may explain the blunted acquisition of antibody responses seen to malaria antigens following natural exposure or vaccination in malaria endemic areas.
Project description:Falciparum malaria is clinically heterogeneous and the relative contribution of parasite and host in shaping disease severity remains unclear. We explored the interaction between inflammation and parasite variant surface antigen (VSA) expression, asking whether this relationship underpins the variation observed in controlled human malaria infection (CHMI). We uncovered marked heterogeneity in the host response to blood challenge; some volunteers remained quiescent, others triggered interferon-stimulated inflammation and some showed transcriptional evidence of myeloid cell suppression. Significantly, only inflammatory volunteers experienced hallmark symptoms of malaria. When we tracked temporal changes in parasite VSA expression to ask whether variants associated with severe disease rapidly expand in naive hosts, we found no transcriptional evidence to support this hypothesis. These data indicate that parasite variants that dominate severe malaria do not have an intrinsic growth or survival advantage; instead, they presumably rely upon infection-induced changes in their within-host environment for selection.