Showing papers on "Plasmodium berghei published in 2002"
TL;DR: Synthetic GPI is shown to be a significant pro-inflammatory endotoxin of parasitic origin, and that several disease parameters in malarious mice are toxin-dependent, suggesting GPI may contribute to pathogenesis and fatalities in humans.
Abstract: The malaria parasite Plasmodium falciparum infects 5-10% of the world's population and kills two million people annually. Fatalities are thought to result in part from pathological reactions initiated by a malarial toxin. Glycosylphosphatidylinositol (GPI) originating from the parasite has the properties predicted of a toxin; however, a requirement for toxins in general and GPI in particular in malarial pathogenesis and fatality remains unproven. As anti-toxic vaccines can be highly effective public health tools, we sought to determine whether anti-GPI vaccination could prevent pathology and fatalities in the Plasmodium berghei/rodent model of severe malaria. The P. falciparum GPI glycan of the sequence NH(2)-CH(2)-CH(2)-PO(4)-(Man alpha 1-2)6Man alpha 1-2Man alpha 1-6Man alpha 1-4GlcNH(2)alpha 1-6myo-inositol-1,2-cyclic-phosphate was chemically synthesized, conjugated to carriers, and used to immunize mice. Recipients were substantially protected against malarial acidosis, pulmonary oedema, cerebral syndrome and fatality. Anti-GPI antibodies neutralized pro-inflammatory activity by P. falciparum in vitro. Thus, we show that GPI is a significant pro-inflammatory endotoxin of parasitic origin, and that several disease parameters in malarious mice are toxin-dependent. GPI may contribute to pathogenesis and fatalities in humans. Synthetic GPI is therefore a prototype carbohydrate anti-toxic vaccine against malaria.
480 citations
TL;DR: A simple in vivo double‐stranded RNA knockout approach to determine the function of the mosquito antimicrobial peptide gene Defensin concludes that this peptide is not a major antiparasitic factor in A. gambiae in vivo.
Abstract: Anopheles gambiae, the major vector of human malaria parasite, is an important insect model to study vector–parasite interactions. Here, we developed a simple in vivo double-stranded RNA (dsRNA) knockout approach to determine the function of the mosquito antimicrobial peptide gene Defensin. We injected dsRNA into adults and observed efficient and reproducible silencing of Defensin. Analysis of the knockdown phenotype revealed that this peptide is required for the mosquito antimicrobial defense against Gram-positive bacteria. In contrast, in mosquitoes infected by Plasmodium berghei, no loss of mosquito viability and no significant effect on the development and morphology of the parasite midgut stages were observed in the absence of Defensin. We conclude that this peptide is not a major antiparasitic factor in A. gambiae in vivo. Our results open new perspectives for the study of mosquito gene function in vivo and provide a basis for genome-scale systematic functional screens by targeted gene silencing.
347 citations
TL;DR: It is demonstrated that CD8+ αβ T cells, which sequester in the brain at the time when neurological symptoms appear, were responsible for CM mortality, suggesting a mechanism which unifies disparate observations in humans.
Abstract: Cerebral malaria (CM) develops in a small proportion of persons infected with Plasmodium falciparum and accounts for a substantial proportion of the mortality due to this parasite. The actual pathogenic mechanisms are still poorly understood, and in humans investigations of experimental CM are unethical. Using an established Plasmodium berghei-mouse CM model, we have investigated the role of host immune cells at the pathological site, the brain. We report in this study the detailed quantification and characterization of cells, which migrated and sequestered to the brain of mice with CM. We demonstrated that CD8(+) alphabeta T cells, which sequester in the brain at the time when neurological symptoms appear, were responsible for CM mortality. These observations suggest a mechanism which unifies disparate observations in humans.
326 citations
TL;DR: It is shown that LT α, not TNFα, is the principal mediator of murine CM, and studies in bone marrow (BM) chimeric mice showed the persistence of cerebral LTα mRNA after irradiation and engraftment of LTα-deficient BM, indicating that LTα originated from a radiation-resistant cell population.
Abstract: Cerebral malaria (CM) causes death in children and nonimmune adults. TNF-alpha has been thought to play a key role in the development of CM. In contrast, the role of the related cyto-kine lymphotoxin alpha (LTalpha) in CM has been overlooked. Here we show that LTalpha, not TNFalpha, is the principal mediator of murine CM. Mice deficient in TNFalpha (B6.TNFalpha-/-) were as susceptible to CM caused by Plasmodium berghei (ANKA) as C57BL/6 mice, and died 6 to 8 d after infection after developing neurological signs of CM, associated with perivascular brain hemorrhage. Significantly, the development of CM in B6.TNFalpha-/- mice was not associated with increased intracellular adhesion molecule (ICAM)-1 expression on cerebral vasculature and the intraluminal accumulation of complement receptor 3 (CR3)-positive leukocytes was moderate. In contrast, mice deficient in LTalpha (B6.LTalpha-/-) were completely resistant to CM and died 11 to 14 d after infection with severe anemia and hyperparasitemia. No difference in blood parasite burden was found between C57BL/6, B6.TNFalpha-/-, and B6.LTalpha-/- mice at the onset of CM symptoms in the two susceptible strains. In addition, studies in bone marrow (BM) chimeric mice showed the persistence of cerebral LTalpha mRNA after irradiation and engraftment of LTalpha-deficient BM, indicating that LTalpha originated from a radiation-resistant cell population.
259 citations
TL;DR: Transgene expression reducedPlasmodium berghei oocyst formation by 87% on average and greatly impaired transmission of the parasite to naive mice, indicating that PLA2 may be used as an additional effector gene to block the development of the malaria parasite in mosquitoes.
198 citations
TL;DR: The malaria protozoan, Plasmodium berghei, exhibits features typical of metazoan apoptotic cells including condensation of chromatin, fragmentation of the nuclear DNA and movement of phosphatidylserine from the inner to the outer lamellae of the cell membrane, which occur in vitro.
192 citations
TL;DR: It is shown that loss‐of‐ function mutations in two adhesive modules of the TRAP ectodomain, an integrin‐like A‐domain and a thrombospondin type I repeat, specifically decrease sporozoite invasion of host cells but do not affect sporozoites gliding and adhesion to cells.
Abstract: Plasmodium sporozoites, the transmission form of the malaria parasite, successively invade salivary glands in the mosquito vector and the liver in the mammalian host Sporozoite capacity to invade host cells is mechanistically related to their ability to glide on solid substrates, both activities depending on the transmembrane protein TRAP Here, we show that loss-of- function mutations in two adhesive modules of the TRAP ectodomain, an integrin-like A-domain and a thrombospondin type I repeat, specifically decrease sporozoite invasion of host cells but do not affect sporozoite gliding and adhesion to cells Irrespective of the target cell, ie in mosquitoes, rodents and cultured human or hamster cells, sporozoites bearing mutations in one module are less invasive, while those bearing mutations in both modules are non-invasive In Chinese hamster ovary cells, the TRAP modules interact with distinct cell receptors during sporozoite invasion, and thus act as independently active pass keys As these modules are also present in other members of the TRAP family of proteins in Apicomplexa, they may account for the capacity of these parasites to enter many cell types of phylogenetically distant origins
179 citations
TL;DR: It is shown that protective parasite-specific CD4+ T cells were depleted after infection with both lethal and nonlethal species of rodent Plasmodium, and in vivo administration of anti–interferon (IFN)-γ antibody blocks depletion, suggesting that IFN-γ is involved in the process.
Abstract: It is thought that both helper and effector functions of CD4+ T cells contribute to protective immunity to blood stage malaria infection. However, malaria infection does not induce long-term immunity and its mechanisms are not defined. In this study, we show that protective parasite-specific CD4+ T cells were depleted after infection with both lethal and nonlethal species of rodent Plasmodium. It is further shown that the depletion is confined to parasite-specific T cells because (a) ovalbumin (OVA)-specific CD4+ T cells are not depleted after either malaria infection or direct OVA antigen challenge, and (b) the depletion of parasite-specific T cells during infection does not kill bystander OVA-specific T cells. A significant consequence of the depletion of malaria parasite–specific CD4+ T cells is impaired immunity, demonstrated in mice that were less able to control parasitemia after depletion of transferred parasite-specific T cells. Using tumor necrosis factor (TNF)-RI knockout– and Fas-deficient mice, we demonstrate that the depletion of parasite-specific CD4+ T cells is not via TNF or Fas pathways. However, in vivo administration of anti–interferon (IFN)-γ antibody blocks depletion, suggesting that IFN-γ is involved in the process. Taken together, these data suggest that long-term immunity to malaria infection may be affected by an IFN-γ–mediated depletion of parasite-specific CD4+ T cells during infection. This study provides further insight into the nature of immunity to malaria and may have a significant impact on approaches taken to develop a malaria vaccine.
143 citations
TL;DR: Results suggest that P. berghei MAEBL is a sporozoite attachment protein that participates in specific binding to and infection of the mosquito salivary gland.
Abstract: Malarial sporozoites mature in the oocysts formed in the mosquito midgut wall and then selectively invade the salivary glands, where they wait to be transmitted to the vertebrate host via mosquito bite. Invasion into the salivary gland has been thought to be mediated by specific ligand-receptor interactions, but the molecules involved in these interactions remain unknown. MAEBL is a single transmembrane-like protein that is structurally related to merozoite adhesive proteins. We found MAEBL of the rodent malaria parasite, Plasmodium berghei, to be specifically produced by the sporozoites in the oocyst and localized in their micronemes, which are secretory organelles involved in malarial parasite invasion into the host cell. A targeted disruption experiment of the P. berghei MAEBL gene revealed that it was essential for sporozoite infection of the salivary gland and was involved in the attachment to the salivary gland surface. In contrast, the disruption of the MAEBL gene did not affect sporozoite motility in vitro nor infectivity to the vertebrate host. These results suggest that P. berghei MAEBL is a sporozoite attachment protein that participates in specific binding to and infection of the mosquito salivary gland.
127 citations
TL;DR: It is shown here that P. falciparum circumsporozoite protein functions in rodent parasite and thatP.
121 citations
TL;DR: It is found that P.falciparum ingestion triggers a midgut‐associated, as well as a systemic, response in the mosquito, with three genes, NOS, defensin and GNBP, being regulated by ingestion of gametocytes, the infectious stage of the parasite.
Abstract: Deciphering molecular interactions between the malaria parasite and its mosquito vector is an emerging area of research that will be greatly facilitated by the recent sequencing of the genomes of Anopheles gambiae mosquito and of various Plasmodium species. So far, most such studies have focused on Plasmodium berghei, a parasite species that infects rodents and is more amenable to studies. Here, we analysed the expression pattern of nine An.gambiae genes involved in immune surveillance during development of the human malaria parasite P.falciparum in mosquitoes fed on parasite-containing blood from patients in Cameroon. We found that P.falciparum ingestion triggers a midgut-associated, as well as a systemic, response in the mosquito, with three genes, NOS, defensin and GNBP, being regulated by ingestion of gametocytes, the infectious stage of the parasite. Surprisingly, we found a different pattern of expression of these genes in the An.gambiae–P.berghei model. Therefore, differences in mosquito reaction against various Plasmodium species may exist, which stresses the need to validate the main conclusions suggested by the P.berghei–An.gambiae model in the P.falciparum–An.gambiae system.
TL;DR: The entire life cycle of P. berghei, a useful model malaria parasite, can now be achieved in vitro, with efficiencies similar to those recorded in vivo and without the need for salivary gland invasion.
Abstract: Methods for reproducible in vitro development of the mosquito stages of malaria parasites to produce infective sporozoites have been elusive for over 40 years. We have cultured gametocytes of Plasmodium berghei through to infectious sporozoites with efficiencies similar to those recorded in vivo and without the need for salivary gland invasion. Oocysts developed extracellularly in a system whose essential elements include co-cultured Drosophila S2 cells, basement membrane matrix, and insect tissue culture medium. Sporozoite production required the presence of para-aminobenzoic acid. The entire life cycle of P. berghei, a useful model malaria parasite, can now be achieved in vitro.
TL;DR: Monoclonal and polyclonal Abs to P. falciparum repeats neutralize hybrid parasite infectivity, and mice immunized with a P. Falcon vaccine are protected against challenge with hybrid sporozoites.
Abstract: Malaria vaccines containing the Plasmodium falciparum Circumsporozoite protein repeat domain are undergoing human trials. There is no simple method to evaluate the effect of vaccine-induced responses on P. falciparum sporozoite infectivity. Unlike the rodent malaria Plasmodium berghei, P. falciparum sporozoites do not infect common laboratory animals and only develop in vitro in human hepatocyte cultures. We generated a recombinant P. berghei parasite bearing P. falciparum Circumsporozoite protein repeats. These hybrid sporozoites are fully infective in vivo and in vitro. Monoclonal and polyclonal Abs to P. falciparum repeats neutralize hybrid parasite infectivity, and mice immunized with a P. falciparum vaccine are protected against challenge with hybrid sporozoites.
TL;DR: A single copy gene that is highly conserved amongst Plasmodium species that encodes a secreted protein named PxSR is reported that is completely novel in biology and is only found in Apicomplexa parasites and is expressed in sporozoites of both human and rodent malaria species.
Abstract: Malaria parasites suffer severe losses in the mosquito as they cross the midgut, haemolymph and salivary gland tissues, in part caused by immune responses of the insect. The parasite compensates for these losses by multiplying during the oocyst stage to form the infectious sporozoites. Upon human infection, malaria parasites are again attenuated by sustained immune attack. Here, we report a single copy gene that is highly conserved amongst Plasmodium species that encodes a secreted protein named PxSR. The predicted protein is composed of a unique combination of metazoan protein domains that have been previously associated with immune recognition/activation and lipid/protein adhesion interactions at the cell surface, namely: (i) scavenger receptor cysteine rich (SRCR); (ii) pentraxin (PTX); (iii) polycystine-1, lipoxygenase, alpha toxin (LH2/PLAT); (iv) Limulus clotting factor C, Coch-5b2 and Lgl1 (LCCL). In our assessment the PxSR molecule is completely novel in biology and is only found in Apicomplexa parasites. We show that PxSR is expressed in sporozoites of both human and rodent malaria species. Disruption of the PbSR gene in the rodent malaria parasite P. berghei results in parasites that form normal numbers of oocysts, but fail to produce any sporozoites. We suggest that, in addition to a role in sporogonic development, PxSR may have a multiplicity of functions.
TL;DR: Analysis of the ultrastructure of P.berghei oocyst differentiation in the wild type, recombinants that do not produce or produce reduced amounts of CS, and corresponding complemented clones indicates that CS is essential for establishing polarity in the Oocyst.
Abstract: The sporozoite stage of the Plasmodium parasite is formed by budding from a multinucleate oocyst in the mosquito midgut. During their life, sporozoites must infect the salivary glands of the mosquito vector and the liver of the mammalian host; both events depend on the major sporozoite surface protein, the circumsporozoite protein (CS). We previously reported that Plasmodium berghei oocysts in which the CS gene is inactivated do not form sporozoites. Here, we analyzed the ultrastructure of P.berghei oocyst differentiation in the wild type, recombinants that do not produce or produce reduced amounts of CS, and corresponding complemented clones. The results indicate that CS is essential for establishing polarity in the oocyst. The amounts of CS protein correlate with the extent of development of the inner membranes and associated microtubules underneath the oocyst outer membrane, which normally demarcate focal budding sites. This is a first example of a protein controlling both morphogenesis and infectivity of a parasite stage.
TL;DR: The existence of the skin stage of malaria parasites before the liver stage and the blood stage is proposed, which would indicate that malaria infection occurs not only by blood feeding of the infective mosquito but also by probing of the mosquito.
TL;DR: Treatment of infected mice with the caspase inhibitor ZVAD-fmk decreased the number of mcp and the thrombocytopenia and caused a decrease in the mortality associated with CM, indicating a critical role of caspases in the expression of CM.
Abstract: Infection of mice with Plasmodium Berghei Anka (PbA) leads to a thrombocytopenia, due to a reduced platelet life span, eventually associated with a syndrome of severe or cerebral malaria (CM). Thrombocytopenia was associated with an increase in the number of microparticles (mcp) in plasma. More than >60% of these mcp were of platelet origin, as seen by staining with an anti-platelet antibody. The thrombocytopenia and the amount of mcp were decreased in mice treated with anti CD40L mAb, suggesting that CD40L is the main effector of the thrombocytopenia. Caspase-1, -3, -6, -8, -9 were activated in platelets from infected mice, as seen by the binding of labeled probes or the amount of pro-caspase-3. Treatment of infected mice with the caspases inhibitor ZVAD-fmk decreased the number of mcp and the thrombocytopenia, shoving that platelet caspases are responsible for platelet fragmentation. In addition, the caspase inhibitor also caused a decrease in the mortality associated with CM, indicating a critical role of caspases in the expression of CM.
TL;DR: Observations suggest that azadarachtin specifically disrupts the patterning of microtubules into more complex structures, such as mitotic spindles and axonemes, during gametogenesis in Plasmodium berghei.
Abstract: Transmission of malaria parasites from vertebrate blood to the mosquito vector depends critically on the differentiation of the gametocytes into gametes. This occurs in response to environmental stimuli encountered by the parasite in the mosquito bloodmeal. Male gametogenesis involves three rounds of DNA replication and endomitosis, and the assembly de novo of 8 motile axonemes. Azadirachtin, a plant limnoid and insecticide with an unkown mode of action, specifically inhibits the release of motile gametes from activated microgametocytes but does not inhibit growth and replication of a sexual blood stages. We have combined confocal laser scanning microscopy and transmission electron microscopy to examine the effect of azadirachtin on the complex reorganisation of the microtubule cytoskeleton during gametogenesis in Plasmodium berghei. Neither the replication of the genome nor the ability of tubulin monomers to assemble into microtubules upon gametocyte activation were prevented by azadirachtin. However, the drug interfered with the formation of mitotic spindles and with the assembly of microtubules into typical axonemes. Our observations suggest that azadarachtin specifically disrupts the patterning of microtubules into more complex structures, such as mitotic spindles and axonemes.
28 Jun 2002
TL;DR: Part I. Assessing Risk of Infection and Severity of Disease Vector Incrimination and Entomological Inoculation rates John C. Beier Epidemiological Measures of Risk of Malaria J. Bangs, Jason D. Maguire, and Mazie J. Barcus.
Abstract: Part I. Assessing Risk of Infection and Severity of Disease Vector Incrimination and Entomological Inoculation Rates John C. Beier Epidemiological Measures of Risk of Malaria J. Kevin Baird, Michael J. Bangs, Jason D. Maguire, and Mazie J. Barcus Part II. Laboratory Models Maintenance of the Plasmodium berghei Life Cycle Robert E. Sinden, Geoff A. Butcher, and A. L. Beetsma Mouse Models for Pre-Erythrocytic-Stage Malaria Laurent Renia, Elodie Belnoue, and Irene Landau Mouse Models for Erythrocytic-Stage Malaria Latifu A. Sanni, Luis F. Fonseca, and Jean Langhorne Nonhuman Primate Models : I. Nonhuman Primate Host-Parasite Combinations William E. Collins Nonhuman Primate Models : II. Infection of Saimiri and Aotus Monkeys with Plasmodium vivax William E. Collins Part III. Diagnosis and Typing Vector Analysis John C. Beier Genotyping of Plasmodium spp.: Nested PCR Georges Snounou Genotyping of Plasmodium falciparum: PCR-RFLP Analysis Ingrid Felger and Hans-Peter Beck Microsatellite Analysis in Plasmodium falciparum Xin-zhuan Su and Michael T. Ferdig Quantitation of Liver-Stage Parasites by Automated TaqMan (R) Real-Time PCR Adam A. Witney, Robert M. Anthony, and Daniel J. Carucci Quantitation of Liver-Stage Parasites by Competitive RT-PCR Kyle C. McKenna and Marcelo R. S. Briones Part IV. Molecular Biology Techniques Extraction and Purification of Plasmodium Total RNA Till Voss Extraction and Purification of Plasmodium Parasite DNA Hans-Peter Beck Southern Blotting of Parasite DNA Tobias Spielmann SDS-PAGE and Western Blotting of Plasmodium falciparum Proteins Roland A. Cooper Nested PCR Analysis of Plasmodium Parasites Georges Snounou and BalbirSingh RFLP Analysis Hans-Peter Beck Analysis of Gene Expression by RT-PCR Peter Preiser In Situ Detection of RNA in Blood- and Mosquito-Stage Malaria Parasites Joanne Thompson Purification of Chromosomes from Plasmodium falciparum Daniel J. Carucci, Paul Horrocks, and Malcolm J. Gardner Construction of Genomic Libraries from the DNA of Plasmodium Species Leda M. Cummings, Dharmendar Rathore, and Thomas F. McCutchan Construction of a Gene Library with Mung Bean Nuclease-Treated Genomic DNA Dharmendar Rathore and Thomas F. McCutchan Construction of Plasmodium falciparum l cDNA Libraries David A. Fidock, Dharmendar Rathore, and Thomas F. McCutchan Production of Stage-Specific Plasmodium falciparum cDNA Libraries Using Subtractive Hybridization David A. Fidock, Thanh V. Nguyen, Brenda T. Beerntsen, and Anthony A. James Construction and Screening of YAC Libraries Cecilia P. Sanchez, Martin Preuss, and Michael Lanzer Episomal Transformation of Plasmodium berghei Chris J. Janse and Andrew P. Waters Gene Targeting in Plasmodium berghei Vandana Thathy and Robert Menard Part V. Immunological Techniques Peptide Vaccination, Valentin Meraldi Jackeline F. Romero, and Giampietro Corradin DNA Vaccination Richard C. Hedstrom and Denise L. Doolan Assessing Antigen-Specific CD8+ and CD4+ T-Cell Responses in Mice After Immunization with Recombinant Viruses Moriya Tsuji Assessing CD4+ Helper T-Lymphocyte Responses by Lymphoproliferation Isabella A. Quakyi and Jeffrey D. Ahlers Limiting Dilution Analysis of Antigen-Specific CD4+ T-Cell Responses in Mice Elsa Seixas, Jean Langhorne, and Stuart Quin Cell Trafficking: Malaria Blood-Stage Parasite-Specific CD4+ T Cells After Adoptive Transfer into Mice Chakrit
TL;DR: Treatment with rIL-18 increased serum IFN-γ levels in mice infected with both parasites, delayed onset of parasitemia, conferred a protective effect, and thus increased survival rate of infected mice.
Abstract: A possible protective role of IL-18 in host defense against blood-stage murine malarial infection was studied in BALB/c mice using a nonlethal strain, Plasmodium yoelii 265, and a lethal strain, Plasmodium berghei ANKA. Infection induced an increase in mRNA expression of IL-18, IL-12p40, IFN-gamma, and TNF-alpha in the case of P. yoelii 265 and an increase of IL-18, IL-12p40, and IFN-gamma in the case of P. berghei ANKA. The timing of mRNA expression of IL-18 in both cases was consistent with a role in the induction of IFN-gamma protein expression. Histological examination of spleen and liver tissues from infected controls treated with PBS showed poor cellular inflammatory reaction, massive necrosis, a large number of infected parasitized RBCs, and severe deposition of hemozoin pigment. In contrast, IL-18-treated infected mice showed massive infiltration of inflammatory cells consisting of mononuclear cells and Kupffer cells, decreased necrosis, and decreased deposition of the pigment hemozoin. Treatment with rIL-18 increased serum IFN-gamma levels in mice infected with both parasites, delayed onset of parasitemia, conferred a protective effect, and thus increased survival rate of infected mice. Administration of neutralizing anti-IL-18 Ab exacerbated infection, impaired host resistance and shortened the mean survival of mice infected with P. berghei ANKA. Furthermore, IL-18 knockout mice were more susceptible to P. berghei ANKA than were wild-type C57BL/6 mice. These data suggest that IL-18 plays a protective role in host defense by enhancing IFN-gamma production during blood-stage infection by murine malaria.
TL;DR: The first evidence of loci associated with resistance to murine cerebral malaria, which may have important implications for the search for genetic factors controlling cerebral malaria in humans is provided.
Abstract: Malaria is a complex infectious disease in which the host/parasite interaction is strongly influenced by host genetic factors. The consequences of plasmodial infections range from asymptomatic to severe complications like the neurological syndrome cerebral malaria induced by Plasmodium falciparum in humans and Plasmodium berghei ANKA in rodents. Mice infected with P. berghei ANKA show marked differences in disease manifestation and either die from experimental cerebral malaria (ECM) or from hemolytic anemia caused by hyperparasitemia (HP). A majority of laboratory mouse strains so far investigated are susceptible to ECM; however, a number of wild-derived inbred strains show resistance. To evaluate the genetic basis of this difference, we crossed a uniquely ECM-resistant, wild-derived inbred strain (WLA) with an ECM susceptible laboratory strain (C57BL/6J). All of the (WLA × C57BL/6J) F1 and 97% of the F2 progeny displayed ECM resistance similar to the WLA strain. To screen for loci contributing to ECM resistance, we analyzed a cohort of mice backcrossed to the C57BL/6J parental strain. A genome wide screening of this cohort provided significant linkage of ECM resistance to marker loci in two genetic regions on chromosome 1 (χ2 = 18.98, P = 1.3 × 10−5) and on chromosome 11 (χ2 = 16.51, P = 4.8 × 10−5), being designated Berr1 and Berr2, respectively. These data provide the first evidence of loci associated with resistance to murine cerebral malaria, which may have important implications for the search for genetic factors controlling cerebral malaria in humans.
TL;DR: The data suggest that CTLA-4 expression prevents immune pathology by restricting T cell activation during malaria, and indicate that the development of cerebral malaria is mediated by a failure to down-regulate T cellactivation.
Abstract: Cytolytic T lymphocyte-associated Ag-4 (CD152) is a negatively regulating molecule, which is primarily expressed on T cells following their activation. In this study, we have examined the role of CTLA-4 expression in experimental blood-stage malaria. Similar to human malaria, CTLA-4 is expressed on CD4(+) T cells of C57BL/6 mice after infection with Plasmodium berghei. A kinetic analysis revealed that CTLA-4 expression was increased on day 5 postinfection and reached a peak on day 9 postinfection, when almost 10% of splenic CD4(+) T cells expressed CTLA-4. Blockade of CTLA-4 in vivo by a specific mAb and subsequent challenge with P. berghei caused neurological signs reminiscent of murine cerebral malaria and earlier death. Histologic examination of brain sections from anti-CTLA-4-treated mice revealed pathologic changes such as hemorrhages and edema, which were absent in control mice. Furthermore, treatment with anti-CTLA-4 also reversed the extensive loss of CD4(+) T cells and the suppressed T cell response occurring during blood-stage malaria. Our data suggest that CTLA-4 expression prevents immune pathology by restricting T cell activation during malaria. They also indicate that the development of cerebral malaria is mediated by a failure to down-regulate T cell activation.
TL;DR: Novel peptides are designed that produce high rates of mortality among protozoa of the genus Plasmodium, the malaria parasites, using existing antimicrobial peptide sequences as templates and synthesized three short novel hybrids, designated Vida1 to Vida3.
Abstract: Insects produce several types of peptides to combat a broad spectrum of invasive pathogenic microbes, including protozoans. However, despite this defense response, infections are often established. Our aim was to design novel peptides that produce high rates of mortality among protozoa of the genus Plasmodium, the malaria parasites. Using existing antimicrobial peptide sequences as templates, we designed and synthesized three short novel hybrids, designated Vida1 to Vida3. Each has a slightly different predicted secondary structure. The peptides were tested against sporogonic stages of the rodent malaria parasites Plasmodium berghei (in vitro and in vivo) and P. yoelii nigeriensis (in vitro). The level of activity varied for each peptide and according to the parasite stage targeted. Vida3 (which is predicted to have large numbers of beta sheets and coils but no alpha helices) showed the highest level of activity, killing the early sporogonic stages in culture and causing highly significant reductions in the prevalence and intensity of infection of P. berghei after oral administration or injection in Anopheles gambiae mosquitoes. The secondary structures of these peptides may play a crucial role in their ability to interact with and kill sporogonic forms of the malaria parasite.
TL;DR: The influence of the MHC haplotype on overcoming CM was analyzed by using MHC congenic mice with C57BL/10 and C3H backgrounds, and no correlation was found between MHC molecules and the development of CM.
Abstract: The neurological syndrome caused by Plasmodium berghei ANKA in rodents partially mimics the human disease. Several rodent models of cerebral malaria (CM) exist for the study of the mechanisms that cause the disease. However, since common laboratory mouse strains have limited gene pools, the role of their phenotypic variations causing CM is restricted. This constitutes an obstacle for efficient genetic analysis relating to the pathogenesis of malaria. Most common laboratory mouse strains are susceptible to CM, and the same major histocompatibility complex (MHC) haplotype may exhibit different levels of susceptibility. We analyzed the influence of the MHC haplotype on overcoming CM by using MHC congenic mice with C57BL/10 and C3H backgrounds. No correlation was found between MHC molecules and the development of CM. New wild-derived mouse strains with wide genetic polymorphisms were then used to find new models of resistance to CM. Six of the twelve strains tested were resistant to CM. For two of them, F1 progeny and backcrosses performed with the reference strain C57BL/6 showed a high level of heterogeneity in the number and characteristics of the genetic factors associated with resistance to CM.
TL;DR: The results suggest that A. albimanus hemolymph and midguts produce O−2 that may limit Plasmodium spp.
Abstract: The mechanisms of Plasmodium spp. elimination in resistant mosquitoes are not completely understood. Some resistant anopheline strains are able to melanize Plasmodium spp. ookinetes in their midguts. Because quinoid compounds are potent catalysts for free radical generation and because these radicals can be generated in association with melanogenesis, it is probable that they play an important role in the elimination of parasites. The production of the superoxide anion (O−2) in the hemolymph and midgut of Anopheles albimanus female mosquitoes and its cytotoxic effect on Plasmodium berghei ookinetes were analyzed. Ookinetes inoculated into the hemocoel of A. albimanus were covered with melanin and then encapsulated by hemocytes within 1 hr. The presence of O−2 in midguts and in hemolymph obtained by perfusion was verified by the reduction of 3-(4,5 dimethylthiazolil-2)-2,5-diphenyl tetrazolium bromide. O−2 was generated in the hemolymph obtained by perfusion and midguts only in the presence of dihydroxyphe...
TL;DR: This study supports the possibility that coma and death are mediated not by cell sequestration or breakdown of vascular permeability, similar in TNFR1-/- or TNFR2-/- mice, but by metabolic disturbances selectively mediated by theTNFR2.
TL;DR: The sequence analysis and gene structure of the Plasmodium falciparum maebl gene is reported here and it is reported that the dual stage expression of MAEBL makes it an excellent pre-erythrocytic and erythroCytic stage vaccine target antigen.