ABSTRACT: Systemic injection of salivary glands P. berghei ANKA GFP-sporozoites into IFNAR-/- mice or salivary glands extracts from non-infected mosquitoes into wild-type C57BL/6 mice. Data obtained were compared with part of hybridizations from experiment E-TABM-839
ORGANISM(S): Mus musculus
DISEASE(S): P. berghei ANKA GFP sporozoite's infection
Project description:We show that an ongoing malaria blood stage infection impairs the establishment of Plasmodium sporozoites in hepatocytes and that secondary infections can only be established after a previous infection has been cleared from circulation. Using control mice, mice infected with sporozoites only, mice infected by iRBCs only or mice reinfected, we show that this impairment is not due to an effect of the acquired host immune response or to a decrease in host cell survival. Instead, an ongoing blood stage infection leads to a significant increase in the expression of hepcidin, a peptide hormone that is secreted by the liver and controls body iron homeostasis. A rapid increase of hepcidin levels during blood stage infection causes sequestration of iron in storage forms within cells of reticuloendothelial system decreasing its availability in hepatocytes, where it is required for Plasmodium sporozoite establishment.
Project description:P. berghei ANKA parasites were collected from the blood at 74h after infection of wild-type and TCRδ-/- mice with 2x10^4 sporozoites (samples were pooled from 3 mice/ group) and mRNA was sequenced by RNA-seq.
Project description:Salivary glands are the only mosquito tissue invaded by Plasmodium sporozoites being a key stage for the effective parasite transmission and maturation, making knowledge regarding Anopheles sialome highly relevant to understand this process. In this study, we report for the first time a transcriptomic analysis using RNA-seq of An. gambiae infected by P. berghei.
Project description:Using in vitro models, total RNA was extracted from Plasmodium berghei infected hepatocytes at different time points (6,12,18,24 hours post-infection) and hybridized with Affymetrix microarrays. These genes are candidate for functional analysis, and we aim to use different tools to manipulate their expression and assess their impact in the infection.
Project description:MalariaM-bM-^@M-^Ys cycle of infection requires parasite transmission between a mosquito vector and a vertebrate host. Plasmodium regulates transmission by translationally repressing specific mRNAs until their products are needed. We demonstrate that the Plasmodium yoelii Pumilio-FBF family member Puf2 allows the sporozoite to retain its infectivity in the mosquito salivary glands while awaiting transmission. Puf2 mediates this critical feature solely through its RNA-Binding Domain (RBD) likely by protecting and silencing specific mRNAs. Puf2 storage granules are distinct from stress granules and P-bodies and dissolve rapidly after infection of hepatocytes, likely releasing the protected and silenced transcripts for M-bM-^@M-^Xjust-in-timeM-bM-^@M-^Y translation by early exoerythrocytic forms (EEFs). Further corroborating this model, pypuf2- sporozoites have no apparent defect in host infection early after invading the salivary glands, but become progressively noninfectious and subsequently prematurely transform into EEFs during prolonged salivary gland residence. In contrast, the premature overexpression of Puf2 in oocysts causes striking deregulation of sporozoite maturation, resulting in fewer oocyst sporozoites that are non-infectious and unable to colonize the salivary glands. Maintenance of Puf2 expression in liver stage parasites produces no phenotype, suggesting that a window of permissive expression exists. Finally, by conducting the first comparative RNAseq analysis of Plasmodium sporozoites, we have uncovered that Puf2 may play a role in both the protection of specific transcripts as well as RNA turnover via the CCR4/Not complex. These findings uncover requirements for maintaining a window of opportunity for the malaria parasite to accommodate the unpredictable moment of transmission from mosquito to vertebrate host. Wild-type (Py17XNL) and pypuf2 -salivary gland sporozoites
Project description:Many eukaryotic developmental and cell fate decisions are effected post-transcriptionally that mechanistically involve RNA binding proteins as regulators of translation of key mRNAs. In the unicellular eukaryote malaria parasite, Plasmodium, one of the most dramatic changes in cell morphology and function occurs during transmission between mosquito and human host. In the mosquito salivary glands, Plasmodium sporozoites are slender, motile and remain infectious for several weeks; only after transmission and liver cell invasion, does the parasite rapidly transform into a round, non-motile exo-erythrocytic form (EEF) that gives rise to thousands of infectious merozoites to be released into the blood stream. Here we demonstrate a Plasmodium homolog of the RNA binding protein, Pumilio, as a key regulator of the sporozoite to EEF transformation. In the absence of Pumilio-2 (Puf2) Plasmodium berghei sporozoites initiate early stage EEF development inside mosquito salivary glands with characteristic morphological changes; puf2- salivary gland sporozoites lose gliding motility, cell traversal ability and are less infective. Global expression profiling confirmed that transgenic parasites exhibit genome-wide transcriptional adaptations typical for Plasmodium intra-hepatic development. The data demonstrate that Puf2 is a key player in regulating developmental control, and imply that transformation of salivary gland-resident sporozoites into early liver stage parasites is regulated by a post-translational mechanism.
Project description:In addressing R. microplus - A. marginale interactions, we propose and test three linked hypotheses. The first is that the tick gene response is organ specific: the midgut gene regulation is unique during feeding and during acquisition of A. marginale as compared to the salivary gland. This distinction is relevant as the two organs serve very different roles in the transmission biology of A. marginale with early survival and replication within the midgut epithelium, composed of highly phagocytic cells, required for initial colonization while a second round of replication in the salivary gland acini, composed of highly secretory cells, is required for transmission of an infectious dose in the saliva. Importantly, both the midgut epithelium and salivary glands have been identified as separate and distinct barriers for transmission of A. marginale and thus represent two potential sites where transmission could be blocked. The second hypothesis to be tested is that the salivary gland transcriptome is temporally dynamic. Initiation of tick attachment and feeding involves secretion of a virtual pharmacopeia including lytic enzymes, anticoagulants, and inhibitors of the mammalian innate immune and nocioceptive systems. Concomitantly, the acini provide an environment where A. marginale replicates >100 fold and are secreted into the saliva. Prior studies show that duration of feeding is a critical component of transmission efficiency, with increased efficiency positively correlated with time of tick feeding. The third hypothesis to be tested is that A. marginale colonization does not significantly modulate the tick midgut and salivary gland transcriptome. This hypothesis is based on observations by ourselves and others that tick infection does not impart a significant fitness cost on the vector. This is in contrast to other bacterial and protozoal pathogens that have dramatic effects on success of tick attachment, engorgement, and survival. A. marginale, similar to other tick-borne pathogens in the Family Anaplasmataceeae, is believed to have evolved from an arthropod-specific bacterium with relatively late adaptation to specific niches in mammalian hosts. Consequently, we predict that A. marginale is well adapted to its tick vector and utilizes the normal signaling pathways of the feeding tick with few, if any, effects on the midgut and salivary gland transcriptome. In this manuscript, we report the testing of these three hypotheses and present the results in context of the vector-pathogen-mammalian host interaction at the time of transmission. A Roche NimbleGen high-density gene expression microarray was custom designed based on the expressed sequence tag (EST) database, B. microplus Gene Index Version 2 (BmiGI V2) for R. microplus. The expression level of 14,447 R. microplus genes was analyzed from total RNA extracted from 10 different tick tissue samples; 30 arrays were included since triplicates of each different sample were analyzed as follow: unfed (midgut and salivary glands), blood feeding (2 days midgut and 2, 6 and 9 days salivary glands), A. marginale-infected blood feeding (2 days midgut and 2, 6 and 9 days salivary glands).
Project description:Gametocytogenesis and gametogenesis in malaria parasites are complex processes of cell differentiation and development likely involving many gene products. Gametocytes develop in the blood of the vertebrate host but mature gametocytes are not activated until taken up by the mosquito vector. Several distinct mutants have been described that block gametogenesis but the detailed molecular causes for the mutant phenotypes are not understood. To investigate whether a block in gametogenesis also results in a changed transcriptional profile, we studied two gene deletions mutants; act2(-) lacking stage-specific actin II and CDPK4(-) lacking calcium-dependent protein kinase 4. Whole-genome microarray analysis was performed from RNA of mature gametocytes to compare the transcriptomes of the mutants with wild-type Plasmodium berghei. The microarray analysis identified ~12% of all genes being differentially expressed in either or both mutants compared to normal gametocytes, as defined by at least two-fold change in transcript abundance. A large proportion of differentially expressed genes in both mutants overlapped consistent with the developmental gametocyte arrest. Distinct profiles in each mutant were also observed. Microarray experiments were performed as dual-color hybridizations on Agilent-024169 custom whole genome Plasmodium berghei 44K arrays. To compensate for dye-specific effects, a dye-reversal color-swap was applied.
Project description:We found that oral activated charcoal (oAC) provided significant protection against P. berghei ANKA-induced ECM, significantly increasing overall survival time compared to untreated mice. Protection from ECM by oAC was associated with a reduced numbers of splenic TNF+ CD4+ T cells and multifunctional IFNy+TNF+ CD4+ and CD8+ T cells. Furthermore, we identified a whole blood gene expression signature (68 genes) associated with protection from ECM. To evaluate whether oAC might affect current best available anti-malarial treatment, a group of female C57BL/6 mice infected with PbA received Activated Charcoal. At day 6 p.i., and prior to the first deaths of untreated PbA-infected mice, 5 untreated PbA-infected mice (Group 1) and 5 AC-treated PbA-infected mice (Group 2) were killed and fresh blood (300-500�l per mouse) was collected and processed into RNA. Blood was also taken from uninfected control mice (�baseline�- Group 3).