Project description:<h4>Background</h4>Parasitaemia, the percentage of infected erythrocytes, is used to measure progress of experimental Plasmodium infection in infected hosts. The most widely used technique for parasitaemia determination is manual microscopic enumeration of Giemsa-stained blood films. This process is onerous, time consuming and relies on the expertise of the experimenter giving rise to person-to-person variability. Here the development of image-analysis software, named Plasmodium AutoCount, which can automatically generate parasitaemia values from Plasmodium-infected blood smears, is reported.<h4>Methods</h4>Giemsa-stained blood smear images were captured with a camera attached to a microscope and analysed using a programme written in the Python programming language. The programme design involved foreground detection, cell and infection detection, and spurious hit filtering. A number of parameters were adjusted by a calibration process using a set of representative images. Another programme, Counting Aid, written in Visual Basic, was developed to aid manual counting when the quality of blood smear preparation is too poor for use with the automated programme.<h4>Results</h4>This programme has been validated for use in estimation of parasitemia in mouse infection by Plasmodium yoelii and used to monitor parasitaemia on a daily basis for an entire challenge infection. The parasitaemia values determined by Plasmodium AutoCount were shown to be highly correlated with the results obtained by manual counting, and the discrepancy between automated and manual counting results were comparable to those found among manual counts of different experimenters.<h4>Conclusions</h4>Plasmodium AutoCount has proven to be a useful tool for rapid and accurate determination of parasitaemia from infected mouse blood. For greater accuracy when smear quality is poor, Plasmodium AutoCount, can be used in conjunction with Counting Aid.
Project description:Cerebral malaria (CM) is a major complication of Plasmodium falciparum infection in children. The pathogenesis of CM involves vascular inflammation, immune stimulation, and obstruction of cerebral capillaries. Platelets have a prominent role in both immune responses and vascular obstruction. We now demonstrate that the platelet-derived chemokine, platelet factor 4 (PF4)/CXCL4, promotes the development of experimental cerebral malaria (ECM). Plasmodium-infected red blood cells (RBCs) activated platelets independently of vascular effects, resulting in increased plasma PF4. PF4 or chemokine receptor CXCR3 null mice had less severe ECM, including decreased T cell recruitment to the brain, and platelet depletion or aspirin treatment reduced the development of ECM. We conclude that Plasmodium-infected RBCs can directly activate platelets, and platelet-derived PF4 then contributes to immune activation and T cell trafficking as part of the pathogenesis of ECM.
Project description:Malaria is caused by Plasmodium parasites, which are transmitted via the bites of infected Anopheline mosquitoes. Midgut invasion is a major bottleneck for Plasmodium development inside the mosquito vectors. Malaria parasites in the midgut are surrounded by a hostile environment rich in digestive enzymes, while a rapidly responding immune system recognizes Plasmodium ookinetes and recruits killing factors from the midgut and surrounding tissues, dramatically reducing the population of invading ookinetes before they can successfully traverse the midgut epithelium. Understanding molecular details of the parasite-vector interactions requires precise measurement of nascent protein synthesis in the mosquito during Plasmodium infection. Current expression profiling primarily monitors alterations in steady-state levels of mRNA, but does not address the equally critical issue of whether the proteins encoded by the mRNAs are actually synthesized.In this study, we used sucrose density gradient centrifugation to isolate actively translating Anopheles gambiae mRNAs based upon their association with polyribosomes (polysomes). The proportion of individual gene transcripts associated with polysomes, which is determined by RNA deep sequencing, reflects mRNA translational status. This approach led to identification of 1017 mosquito transcripts that were primarily regulated at the translational level after ingestion of Plasmodium falciparum-infected blood. Caspar, a negative regulator of the NF-kappaB transcription factor Rel2, appears to be substantially activated at the translational levels during Plasmodium infection. In addition, transcripts of Dcr1, Dcr2 and Drosha, which are involved in small RNA biosynthesis, exhibited enhanced associations with polysomes after P. falciparum challenge. This observation suggests that mosquito microRNAs may play an important role in reactions against Plasmodium invasion.We analyzed both total cellular mRNAs and mRNAs that are associated with polysomes to simultaneously monitor transcriptomes and nascent protein synthesis in the mosquito. This approach provides more accurate information regarding the rate of protein synthesis, and identifies some mosquito factors that might have gone unrecognized because expression of these proteins is regulated mainly at the translational level rather than at the transcriptional level after mosquitoes ingest a Plasmodium-infected blood meal.
Project description:Microarray studies using synchronized Plasmodium falciparum parasites have revealed a ‘continuous cascade’ of gene expression. Reports vary regarding the stability in these transcriptional patterns in the presence of external stressors. Using Plasmodium yoelii 17X parasites replicating in vivo, we have examined differential gene expression in parasites isolated from individual mice, from independent infections, during ascending and peak parasitemia and in the presence and absence of host antibody responses. Across experimental conditions, transcription was surprisingly stable. Differential gene expression was greatest when comparing differences due to parasite load and/or host cell availability; however, even these changes were modest. Of genes that were differentially expressed, many are of unknown function. There was little to no differential expression of members of the yir and pyst-a multigene families, although a relatively large number of these were expressed during blood-stage infection regardless of experimental condition. Taken together, these results indicate that 1) P. yoelii gene expression remains stable in the presence of a changing host environment and 2) concurrent expression of a large number of the yir and pyst-a genes may function to divert host immune responses away from invariant protective antigens. 1. P. yoelii 17X gene expression profiles were determined in blood-stage parasites isolated from infected Balb/c mice (male, 8-12 weeks old) as follows: a. Mouse 1 (M1), Mouse 2 (M2), Mouse 3 (M3), Donor (D) mouse – three mice simultaneously infected with P. yoelii 17X iRBCs from a single donor mouse. Parasite RNA was isolated early during infection when parasitemia was ascending as follows: M1 - day 11 at 13.0% parasitemia; M2 - day 10 at 11.1% parasitemia; M3 - day 10 at 18.6% parasitemia; D – day 11 at 18.7% parasitemia. b. Infection #1 (I1), infection #2 (I2), infection #3 (I3), infection #4 (I4) – four groups of mice infected on four separate occasions using P. yoelii 17X iRBCs obtained from four separate donor mice. In each case, P. yoelii 17X RNA was isolated from iRBCs obtained on days 10-11 of infection when parasitemia was ascending and was ~15%. c. Day 10 (D10), Day 14 (D14) – P. yoelii 17X RNA isolated from iRBCs during infection #2 on day 10 (14% parasitemia, 14.4% reticulocytes) and on day 14 of infection #2 (43.5% parasitemia, 57.9% reticulocytes). d. WT and JHD - P. yoelii 17X RNA isolated from iRBCs during infection #4 from immunologically intact, wild-type Balb/c mice and B cell deficient, JHD mice on a Balb/c background (ascending infection, 15% parasitemia). e. QA and RMP - P. yoelii 17X RNA isolated from iRBCs during infection #1 from mice previously immunized with a preparation of membrane proteins isolated from P. yoelii 17X infected reticulocytes (PyRMP) (day 12, 13.3% parasitemia and Quil A immunized (QA) control mice (day 10, 15.6% parasitemia) 2. On each array, gene expression in P. yoelii 17X blood-stage parasites was evaluated relative to a standard comparator of purified P. yoelii 17XL total RNA (pooled RNA from 45 mice, mean parasitemia ~35%). Each sample was analyzed on three replicate arrays, one of which was a standard dye-flip. One exception was the infection #3 sample which was analyzed on only on two arrays. On each array, oligonucleotides were spotted in duplicate. 3. Through the use of the standard reference RNA, the following 15 pairwise comparisons across samples were made: (M1 vs M2); (M2 vs M3); (M1 vs M3); (D vs M1); (D vs M2); (D vs M3); (I1 vs I2); (I1 vs I3); (I1 vs I4); (I2 vs I3); (I2 vs I4); (I3 vs I4); (D10 vs D14); (WT vs JHD); (QA vs RMP)
Project description:Transcription profiling by array of mouse male retinas to investigate IGF-I-induced chronic gliosis and retinal stress IGF-I exert multiple effects in different retinal cell populations in both physiological and pathological conditions. Transgenic mice overexpressing IGF-I in the retina showed impaired electroretinographic responses at 6-7 months of age that worsen with age. This retinal neuronal dysfunction was correlated with the loss of rod photoreceptors, bipolar, ganglion and amacrines cells. Neuronal alterations were preceded by the overexpression of retinal stress markers, acute phase proteins and gliosis-related genes. IGF-I overexpression leads to chronic gliosis and microgliosis in TgIGF-I retinas, with mild oxidative stress, impaired recycling of glutamate and defective potassium buffering. These impaired supportive functions can contribute to neurodegeneration in TgIGF-I retinas, together with the increased production of pro-inflammatory cytokines, potential mediators of neuronal death. 3 transgenic and 3 wild type biological replicates examined.
Project description:<h4>Background</h4>The Plasmodium falciparum histidine-rich protein II (PfHRP2) is a common biomarker used in malaria rapid diagnostic tests (RDTs), but can persist in the blood for up to 40 days following curative treatment. The persistence of PfHRP2 presents a false positive limitation to diagnostic interpretation. However, the in vivo dynamics and compartmentalization underlying PfHRP2 persistence have not been fully characterized in the plasma and erythrocyte (RBC) fraction of the whole blood.<h4>Methods</h4>The kinetics and persistence of PfHRP2 in the plasma and RBC fractions of the whole blood were investigated post-treatment in human clinical samples and samples isolated from BALB/c mice infected with a novel transgenic Plasmodium berghei parasite engineered to express PfHRP2 (PbPfHRP2).<h4>Results</h4>PfHRP2 levels in human RBCs were consistently 20-40 times greater than plasma levels, even post-parasite clearance. PfHRP2 positive, DNA negative, once-infected RBCs were identified in patients that comprised 0.1-1% of total RBCs for 6 and 12 days post-treatment, even post-atovaquone-proguanil regimens. Transgenic PbPfHRP2 parasites in BALB/c mice produced and exported tgPfHRP2 to the RBC cytosol similar to P. falciparum. As in humans, tgPfHRP2 levels were found to be approximately 20-fold higher within the RBC fraction than the plasma post-treatment. RBC localized tgPfHRP2 persisted longer than tgPfHRP2 in the plasma after curative treatment. tgPfHRP2 positive, but DNA negative once-infected RBCs were also detected in mouse peripheral blood for 7-9 days after curative treatment.<h4>Conclusions</h4>The data suggest that persistence of PfHRP2 is due to slower clearance of protein from the RBC fraction of the whole blood. This appears to be a result of the presence PfHRP2 in previously infected, pitted cells, as opposed to PfHRP2 binding naïve RBCs in circulation post-treatment. The results thus confirm that the extended duration of RDT positivity after parasite clearance is likely due to pitted, once-infected RBCs that remain positive for PfHRP2.
Project description:In this study, samples from the 2013-2016 West African Ebola virus outbreak from patients in Guinea with Ebola virus disease (EVD) were analyzed to discover and classify what other pathogens were present. Throat swabs were taken from deceased EVD patients, and peripheral blood samples were analyzed that had been taken from patients when they presented at the treatment center with acute illness. High-throughput RNA sequencing (RNA-seq) and bioinformatics were used to identify the potential microorganisms. This approach confirmed Ebola virus (EBOV) in all samples from patients diagnosed as acute positive for the virus by quantitative reverse transcription-PCR in deployed field laboratories. Nucleic acid mapping to Plasmodium was also used on the patient samples, confirming results obtained with an antigen-based rapid diagnostic test (RDT) conducted in the field laboratories. The data suggested that a high Plasmodium load, as determined by sequence read depth, was associated with mortality and influenced the host response, whereas a lower parasite load did not appear to affect outcome. The identifications of selected bacteria from throat swabs via RNA-seq were confirmed by culture. The data indicated that the potential pathogens identified in the blood samples were associated with translocation from the gut, suggesting the presence of bacteremia, which transcriptome data suggested may induce or aggravate the acute-phase response observed during EVD. Transcripts mapping to different viruses were also identified, including those indicative of lytic infections. The development of high-resolution analysis of samples from patients with EVD will help inform care pathways and the most appropriate general antimicrobial therapy to be used in a resource-poor setting. IMPORTANCE Our results highlight the identification of an array of pathogens in the blood of patients with Ebola virus disease (EVD). This has not been done before, and the data have important implications for the treatment of patients with EVD, particularly considering antibiotic stewardship. We show that EVD patients who were also infected with Plasmodium, particularly at higher loads, had more adverse outcomes than patients with lower levels of Plasmodium. However, the presence of Plasmodium did not influence the innate immune response, and it is likely that the presence of EBOV dominated this response. Several viruses other than EBOV were identified, and bacteria associated with sepsis were also identified. These findings were indicative of bacterial translocation across the gut during the acute phase of EVD.
Project description:Plasmodium multigene families play a central role in the pathogenesis of malaria. The Plasmodium interspersed repeat (pir) genes comprise the largest multigene family in many Plasmodium spp. However their function(s) remains unknown. Using the rodent model of malaria, Plasmodium chabaudi, we show that individual CIR proteins have differential localizations within infected red cell (iRBC), suggesting different functional roles in a blood-stage infection. Some CIRs appear to be located on the surface of iRBC and merozoites and are therefore well placed to interact with host molecules. In line with this hypothesis, we show for the first time that a subset of recombinant CIRs bind mouse RBCs suggesting a role for CIR in rosette formation and/or invasion. Together, our results unravel differences in subcellular localization and ability to bind mouse erythrocytes between the members of the cir family, which strongly suggest different functional roles in a blood-stage infection.
Project description:Cerebral malaria (CM) is a severe and rapidly progressing complication of infection by Plasmodium parasites that is associated with high rates of mortality and morbidity. Treatment options are currently few, and intervention with artemisinin (Art) has limited efficacy, a problem that is compounded by the emergence of resistance to Art in Plasmodium parasites. Rocaglates are a class of natural products derived from plants of the Aglaia genus that have been shown to interfere with eukaryotic initiation factor 4A (eIF4A), ultimately blocking initiation of protein synthesis. Here, we show that the rocaglate CR-1-31B perturbs association of Plasmodium falciparum eIF4A (PfeIF4A) with RNA. CR-1-31B shows potent prophylactic and therapeutic antiplasmodial activity in vivo in mouse models of infection with Plasmodium berghei (CM) and Plasmodium chabaudi (blood-stage malaria), and can also block replication of different clinical isolates of P. falciparum in human erythrocytes infected ex vivo, including drug-resistant P. falciparum isolates. In vivo, a single dosing of CR-1-31B in P. berghei-infected animals is sufficient to provide protection against lethality. CR-1-31B is shown to dampen expression of the early proinflammatory response in myeloid cells in vitro and dampens the inflammatory response in vivo in P. berghei-infected mice. The dual activity of CR-1-31B as an antiplasmodial and as an inhibitor of the inflammatory response in myeloid cells should prove extremely valuable for therapeutic intervention in human cases of CM.
Project description:Malaria is a disease with diverse symptoms depending on host immune status and pathogenicity of Plasmodium parasites. The continuous parasite growth within a host suggests mechanisms of immune evasion by the parasite and/or immune inhibition in response to infection. To identify pathways commonly inhibited after malaria infection, we infected C57BL/6 mice with four Plasmodium yoelii strains causing different disease phenotypes and 24 progeny of a genetic cross. mRNAs from mouse spleens day 1 and/or day 4 post infection (p.i.) were hybridized to a mouse microarray to identify activated or inhibited pathways, upstream regulators, and host genes playing an important role in malaria infection. Strong interferon responses were observed after infection with the N67 strain, whereas initial inhibition and later activation of hematopoietic pathways were found after infection with 17XNL parasite, showing unique responses to individual parasite strains. Inhibitions of pathways such as Th1 activation, dendritic cell (DC) maturation, and NFAT immune regulation were observed in mice infected with all the parasite strains day 4 p.i., suggesting universally inhibited immune pathways. As a proof of principle, treatment of N67-infected mice with antibodies against T cell receptors OX40 or CD28 to activate the inhibited pathways enhanced host survival. Controlled activation of these pathways may provide important strategies for better disease management and for developing an effective vaccine.