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Protozoan Parasite (protozoan + parasite)
Selected AbstractsA combined proteomic and transcriptomic approach to the study of stage differentiation in Leishmania infantumPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 12 2006François McNicoll Abstract Protozoan parasites of the genus Leishmania are found as promastigotes in the sandfly vector and as amastigotes in mammalian macrophages. Mechanisms controlling stage-regulated gene expression in these organisms are poorly understood. Here, we applied a comprehensive approach consisting of protein prefractionation, global proteomics and targeted DNA microarray analysis to the study of stage differentiation in Leishmania. By excluding some abundant structural proteins and reducing complexity, we detected and identified numerous novel differentially expressed protein isoforms in L.,infantum. Using 2-D gels, over 2200,protein isoforms were visualized in each developmental stage. Of these, 6.1% were strongly increased or appeared unique in the promastigote stage, while the relative amounts of 12.4% were increased in amastigotes. Amastigote-specific protein isoform and mRNA expression trends correlated modestly (53%), while no correlation was found for promastigote-specific spots. Even where direction of regulation was similar, fold-changes were more modest at the RNA than protein level. Many proteins were present in multiple spots, suggesting that PTM is extensive in this organism. In several cases, different isoforms appeared to be specific to different life stages. Our results suggest that post-transcriptional controls at translational and post-translational levels could play major roles in differentiation in Leishmania parasites. [source] Modelling parasite dissemination: host cell subversion and immune evasion by Toxoplasma gondiiCELLULAR MICROBIOLOGY, Issue 3 2010Henrik Lambert Summary Protozoan parasites belong to the most widespread and devastating human pathogens. Their ability to manipulate host responses and establish infection in their hosts continues to puzzle researchers. Recent developments of experimental model systems are contributing to the discovery of new aspects of the biology of parasite dissemination. Here, we review current knowledge on strategies utilized by the apicomplexan parasite Toxoplasma gondii to disseminate and establish infection in its host. Recent findings have revealed intricate mechanisms by which this obligate intracellular protozoan sequesters cellular functions of the immune system to assure propagation. These mechanisms include the hijacking of migratory leucocytes, modulation of migratory properties of infected cells and rapid transfer of parasites between different leucocyte populations by cytotoxicity-induced parasite egress. Collectively, Toxoplasma strikes a delicate balance, assuring efficient dissemination and establishment of asymptomatic lifelong infection in its host while protecting its intracellular entity and limiting host pathology. [source] Histones and histone modifications in protozoan parasitesCELLULAR MICROBIOLOGY, Issue 12 2006William J. Sullivan Jr Summary Protozoan parasites are early branching eukaryotes causing significant morbidity and mortality in humans and livestock. Single-celled parasites have evolved complex life cycles, which may involve multiple host organisms, and strategies to evade host immune responses. Consequently, two key aspects of virulence that underlie pathogenesis are parasite differentiation and antigenic variation, both of which require changes in the expressed genome. Complicating these requisite alterations in the parasite transcriptome is chromatin, which serves as a formidable barrier to DNA processes including transcription, repair, replication and recombination. Considerable progress has been made in the study of chromatin dynamics in other eukaryotes, and there is much to be gained in extending these analyses to protozoan parasites. Much of the work completed to date has focused on histone acetylation and methylation in the apicomplexans and trypanosomatids. As we describe in this review, such studies provide a unique vantage point of the evolutionary picture of eukaryotic cell development, and reveal unique phenomena that could be exploited pharmacologically to treat protozoal diseases. [source] Actin and myosin in Gregarina polymorphaCYTOSKELETON, Issue 2 2004Matthew B. Heintzelman Abstract Actin and two class XIV unconventional myosins have been cloned from Gregarina polymorpha, a large protozoan parasite inhabiting the gut of the mealworm Tenebrio molitor. These proteins were most similar to their homologues expressed in the coccidian and haemosporidian Apicomplexa such as Toxoplasma and Plasmodium despite the significant morphological differences among these parasites. Both actin and G. polymorpha myosin A (GpMyoA), a 92.6-kDa protein characterized by a canonical myosin head domain and short, highly basic tail, localized to both the longitudinally-disposed surface membrane folds (epicytic folds) of the parasite as well as to the subjacent rib-like myonemes that gird the parasite cortex. G. polymorpha myosin B (GpMyoB), a 96.3-kDa myosin, localized exclusively to the epicytic folds of the parasite. Both myosins were tightly associated with the cortical cytoskeleton and were solubilized only with a combination of high salt and detergent. Both GpMyoA and GpMyoB could bind to actin in an ATP-sensitive fashion. The distribution of actin and the unconventional myosins in G. polymorpha was consistent with their proposed participation in both the rapid (1,10 ,m/sec) gliding motility exhibited by the gregarines as well as the myoneme-mediated bending motions that have been observed in these parasites. Cell Motil. Cytoskeleton 58:83,95, 2004. © 2004 Wiley-Liss, Inc. [source] Associations between host migration and the prevalence of a protozoan parasite in natural populations of adult monarch butterfliesECOLOGICAL ENTOMOLOGY, Issue 2 2000Sonia M. Altizer Summary 1. Monarch butterflies Danaus plexippus (L.) (Lepidoptera: Nymphalidae) are susceptible to infection by the obligate protozoan parasite Ophryocystis elektroscirrha (McLaughlin and Myers) (Apicomplexa: Neogregarinida). Because monarchs form resident and migratory populations in different parts of the world, this host,parasite system provides the opportunity to examine how variation in parasite prevalence relates to host movement patterns. 2. Parasite prevalence was evaluated using 14 790 adult monarchs captured between 1968 and 1997. Comparison of three populations in North America indicated that parasite prevalence is associated negatively with host dispersal distances. A continuously breeding, nonmigratory population in southern Florida showed high prevalence (over 70% heavily infected). The western population migrates moderate distances to overwintering sites on the Pacific Coast and has intermediate prevalence (30% heavily infected). The eastern migratory population, which travels the longest distance to Mexican overwintering sites, has exhibited less than 8% infection throughout the past 30 years. 3. Variation in parasite loads within North American migratory populations was investigated to determine whether the prevalence of heavy infection and average parasite loads declined during migration or overwintering. Average parasite loads of summer-breeding adults in western North America decreased with increasing distance from overwintering sites. This suggests that heavily infected monarchs are less likely to remigrate long distances in spring. No differences in the frequency of heavily infected adults were found among eastern or western North American monarchs throughout the overwintering period, however, suggesting that this parasite does not affect overwintering mortality. 4. Changes in the prevalence of monarchs with low parasite loads demonstrate that spore transfer occurs during migration and overwintering, possibly when adult butterflies contact each other as a result of their clustering behaviour. 5. This study of geographical and temporal variation in O. elektroscirrha among populations of D. plexippus demonstrates the potential role of seasonal migration in mediating interactions between hosts and parasites, and suggests several mechanisms through which migratory behaviour may influence parasite prevalence. [source] Depletion of immature B,cells during Trypanosoma cruzi infection: involvement of myeloid cells and the cyclooxygenase pathwayEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 6 2005Elina Zuniga Abstract The ability of a microorganism to elicit or evade B,cell responses represents a determinant factor for the final outcome of an infection. Although pathogens may subvert humoral responses at different stages of B,cell development, most studies addressing the impact of an infection on the B,cell compartment have focused on mature B,cells within peripheral lymphoid organs. Herein, we report that a protozoan infection, i.e. a Trypanosoma cruzi infection, induces a marked loss of immature B,cells in the BM, which also compromises recently emigrated B,cells in the periphery. The depletion of BM immature B,cells is associated with an increased rate of apoptosis mediated by a parasite-indirect mechanism in a Fas/FasL-independent fashion. Finally, we demonstrated that myeloid cells play an important role in B,cell depletion, since CD11b+ BM cells from infected mice secrete a product of the cyclooxygenase pathway that eliminates immature B,cells. These results highlight a previously unrecognized maneuver used by a protozoan parasite to disable B,cell generation, limiting host defense and favoring its chronic establishment. [source] Identification of exocytotic membrane proteins, syntaxin-1 and SNAP-25, in Entamoeba histolytica from hamster liverHEPATOLOGY RESEARCH, Issue 6 2007Javier Ventura-Juárez Entamoeba histolytica is a protozoan parasite causing dysentery and in some cases liver abscesses. These effects have been attributed to cytolytic substances released by exocytosis. In this study, the presence of the proteins syntaxin-1 and SNAP-25, which are assumed to be involved in exocytosis, were examined by immunohistochemistry, immunoelectron microscopy and western blot analysis. Syntaxin-1 and SNAP-25 were expressed in the vesicular, vacuolar and plasma membranes of E. histolytica trophozoites. It can be concluded that these proteins might be involved in exocytosis processes. [source] Analysis of Cryptosporidium parvum oocyst transport in porous mediaHYDROLOGICAL PROCESSES, Issue 11 2004Song-Bae Kim Abstract Cryptosporidium parvum is a protozoan parasite, transmitted through aqueous environments in the form of an oocyst. In this study, a transport model into which sorption, filtration and inactivation mechanisms are incorporated is applied to simulate laboratory column data, and the suitability of a kinetic model to describe the C. parvum oocyst transport and removal in porous media is compared with an equilibrium model. The kinetic model is applied to simulate previous column experimental data and successfully simulates the concentration peak; the late time tailing effect appeared in the breakthrough curves, indicating that the kinetic model is more suitable than the equilibrium one at simulating the fate and transport of the oocysts in porous media. Simulation illustrates that sorption causes retardation along with a tailing in the breakthrough curve. Additionally, filtration acts as a major mechanism of removing the oocysts from the aqueous phase, whereas the role of inactivation in reducing the viable oocyst concentration is minimal. Copyright © 2004 John Wiley & Sons, Ltd. [source] Detection of Cryptosporidium parvum in lettuceINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2007John E. Moore Summary Human cryptosporidiosis has emerged as an important gastrointestinal infection in the 1990s as a result of the ingestion of mainly contaminated water and to a lesser extent foodstuffs containing the protozoan parasite, Cryptosporidium parvum. This pathogen has particular clinical significance for immunocompromised persons, including AIDS patients and cancer patients receiving toxic chemotherapeutic drug regimens. There have been a limited number of studies performed examining the occurrence of the parasite on vegetables, including lettuce. Detection rates are very dependent on the laboratory isolation technique employed and has ranged from 1.2% to 14.5%. Current best practice of laboratory recovery, isolation and detection methods include detergent removal, oocysts concentration by immunomagnetic separation, followed by a combination of immunofluorescent microscopy and a nested PCR approach. Employment of contaminated non-potable water in the production of vegetables, particularly lettuce, may represent an important potential source of entry of pathogens into food processing and the human food chain. Given that lettuce is an important constituent of hamburger dressing, and the size of the fast-food industry, where lettuce is an important constituent, horticultural producers of lettuce should therefore place special emphasis on developing suitable and efficient Hazard Analysis Critical Control Point strategies for the critical control of oocysts depending on the type of unit operation employed and vegetable being processed. This review aims to examine (i) the incidence of C. parvum in vegetables, particularly lettuce and (ii) laboratory detection methods for the isolation and identification of this parasite from lettuce. [source] Polymorphisms in the sequences of Marteilia internal transcribed spacer region of the ribosomal RNA genes (ITS-1) in Spain: genetic types are not related with bivalve hostsJOURNAL OF FISH DISEASES, Issue 6 2005B Novoa Abstract Marteilia refringens is a protozoan parasite causing a disease notifiable to the Office International des Epizooties (OIE) and its distribution has implications for the transfer of live animals. The internal transcribed spacer-1 (ITS-1) from Marteilia clones contains polymorphism. Digestion with HhaI reveals two different restriction profiles, previously referred as ,O' (Marteilia from oyster or Marteilia refringens) and ,M' (Marteilia from mussels or Marteilia maurini). The aim of the present work was to determine whether the two previously described Marteilia molecular types (O and M) exist in the Iberian Peninsula and the strictness of the association with their bivalve host species. The sequence variability in the ITS-1 of Marteilia species was studied in mussels, Mytilus galloprovincialis, and flat oysters, Ostrea edulis, from different geographical locations in Spain, to establish the existence and the distribution of different species or molecular types. Although there were two distinct evolutionary lineages that corresponded more or less strictly with the ,M' and ,O' types, it was evident from the estimated phylogeny that some ,O' types have switched to ,M' type, and vice versa. Moreover, ,O' types were found in mussels and ,M' types were found in oysters, which suggests that there have been several cross-species transmissions of Marteilia between mussels and oysters. [source] Protecting babies: vaccine strategies to prevent foetopathy in Neospora caninum -infected cattlePARASITE IMMUNOLOGY, Issue 3 2006Review Article SUMMARY Neospora caninum is an apicomplexan protozoan parasite that is a significant infectious abortifacient agent in cattle. Despite the fact that it is a member of a well described taxonomic group, it is a relatively newly discovered parasite and its biology is not yet fully understood. Cattle become infected either congenitally via transplacental transmission or post-natally by ingesting oocysts derived from the definitive host; dogs and coyotes are the only definitive hosts that have been described to date. It is not known which of these two forms of transmission occurs most frequently and which is the most likely to result in abortion; there are no drugs available to treat infected cattle, so current control strategies rely on prevention of infection by management methods and strict hygiene; an effective vaccine would be a great advantage in its control. Neospora caninum is an economically important veterinary pathogen, but we can also draw analogies between its foetopathic effects and those of human pathogens such as Toxoplasma gondii, Chlamydophila abortus and Plasmodium falciparum. Understanding the immune response and the materno,foetal relationship in N. caninum -infected cattle may help us to design vaccination strategies, not only for neosporosis but also for other foetopathic agents. [source] Paraflagellar rod protein-specific CD8+ cytotoxic T lymphocytes target Trypanosoma cruzi -infected host cellsPARASITE IMMUNOLOGY, Issue 8 2002Ruth A. Wrightsman Summary Our previous studies show that in mice immunized with the paraflagellar rod (PFR) proteins of Trypanosoma cruzi protective immunity against this protozoan parasite requires MHC class I-restricted T cell function. To determine whether PFR-specific CD8+ T cell subsets are generated during T. cruzi infection, potential CTL targets in the PFR proteins were identified by scanning the amino acid sequences of the four PFR proteins for regions of 8,10 amino acids that conform to predicted MHC class I H-2b binding motifs. A subset of the peptide sequences identified were synthesized and tested as target antigen in 51Cr-release assays with effector cells from chronically infected T. cruzi mice. Short-term cytotoxic T lymphocyte (CTL) lines specific for two of the peptides, PFR-1164,171 and PFR-3123,130, showed high levels of lytic activity against peptide-pulsed target cells, secreted interferon (IFN)-, in response to parasite-infected target cells, and were found to be CD8+, CD4,, CD3+, TCR,,+ cells of the Tc1 subset. Challenge of PFR immunized CD8,/, and perforin-deficient (PKO) mice confirmed that while CD8+ cells are required for survival of T. cruzi challenge infection, perforin activity is not required. Furthermore, while lytic activity of PFR-specific CD8+ T cell lines derived from PKO mice was severely impaired, the IFN-, levels secreted by CTLs from PKO mice were equivalent to that of normal mice, suggesting that the critical role played by CD8+ T cells in immunity to the parasite may be secretion of type 1 cytokines rather than lysis of parasite infected host cells. [source] The History of Toxoplasma gondii,The First 100 YearsTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 6 2008JITENDER P. DUBEY ABSTRACT. In this paper the history of Toxoplasma gondii and toxoplasmosis is reviewed. This protozoan parasite was first discovered in 1908 and named a year later. Its medical importance remained unknown until 1939 when T. gondii was identified in tissues of a congenitally infected infant, and veterinary importance became known when it was found to cause abortion storms in sheep in 1957. The discovery of a T. gondii specific antibody test, Sabin,Feldman dye test in 1948 led to the recognition that T. gondii is a common parasite of warm-blooded hosts with a worldwide distribution. Its life cycle was not discovered until 1970 when it was found that felids are its definitive host and an environmentally resistant stage (oocyst) is excreted in feces of infected cats. The recent discovery of its common infection in certain marine wildlife (sea otters) indicates contamination of our seas with T. gondii oocysts washed from land. Hygeine remains the best preventive measure because currently there is no vaccine to prevent toxoplasmosis in humans. [source] Heritabilities and quantitative trait loci for blood gases and blood pH in swineANIMAL GENETICS, Issue 2 2009G. Reiner Summary Maintaining pH and blood gases in a narrow range is essential to sustain normal biochemical reactions. Decreased oxygenation, poor tissue perfusion, disturbance to CO2 expiration, and shortage of HCO3, can lead to metabolic acidosis. This is a common situation in swine, and originates from a broad range of medical conditions. pH and blood gases appear to be under genetic control, and populations with physiological traits closer to the pathological thresholds may be more susceptible to developing pathological conditions. However, little is known about the genetic basis of such traits. We have therefore estimated phenotypic and genetic variability and identified quantitative trait loci (QTL) for pH and blood gases in blood samples from 139 F2 pigs from the Meishan/Pietrain family. Samples were taken before and after challenge with Sarcocystis miescheriana, a protozoan parasite of muscle. Twenty-seven QTL influencing pH and blood gases were identified on nine chromosomes. Five of the QTL were significant on a genome-wide level; 22 QTL were significant on a chromosome-wide level. QTL for pH-associated traits have been mapped to SSC3, 18 and X. QTL associated with CO2 have been detected on SSC6, 7, 8 and 9, and QTL associated with O2 on SSC2 and SSC8. QTL showed specific health/disease patterns that were related to the physiological state of the pigs from day 0, to acute disease (day 14), convalescence (day 28) and chronic disease (day 42). The results demonstrate that pH and blood gases are influenced by multiple chromosomal areas, each with relatively small effects. [source] Mapping of quantitative trait loci for clinical,chemical traits in swineANIMAL GENETICS, Issue 1 2009G. Reiner Summary Clinical,chemical traits are diagnostic parameters essential for characterization of health and disease in veterinary practice. The traits show significant variability and are under genetic control, but little is known about the fundamental genetic architecture of this variability, especially in swine. We have identified QTL for alkaline phosphatase (ALP), lactate (LAC), bilirubin (BIL), creatinine (CRE) and ionized sodium (Na+), potassium (K+) and calcium (Ca++) from the serum of 139 F2 pigs from a Meishan/Pietrain family before and after challenge with Sarcocystis miescheriana, a protozoan parasite of muscle. After infection, the pigs passed through three stages representing acute disease, subclinical disease and chronic disease. Forty-two QTL influencing clinical,chemical traits during these different stages were identified on 15 chromosomes. Eleven of the QTL were significant on a genome-wide level; 31 QTL were chromosome-wide significant. QTL showed specific health/disease patterns with respect to the baseline values of the traits as well as the values obtained through the different stages of disease. QTL influencing different traits at different times were found primarily on chromosomes 1, 3, 7 and 14. The most prominent QTL for the investigated clinical,chemical traits mapped to SSC3 and 7. Baseline traits of ALP, LAC, BIL, Ca++ and K+ were influenced by QTL regions on SSC3, 6, 7, 8 and 13. Single QTL explained up to 21.7% of F2 phenotypic variance. Our analysis confirms that variation of clinical,chemical traits is associated with multiple chromosomal regions. [source] Communication between Toxoplasma gondii and its host: impact on parasite growth, development, immune evasion, and virulenceAPMIS, Issue 5-6 2009IRA J. BLADER Toxoplasma gondii is an obligate intracellular protozoan parasite that can infect most warm-blooded animals and cause severe and life-threatening disease in developing fetuses and in immune-compromised patients. Although Toxoplasma was discovered over 100 years ago, we are only now beginning to appreciate the importance of the role that parasite modulation of its host has on parasite growth, bradyzoite development, immune evasion, and virulence. The goal of this review is to highlight these findings, to develop an integrated model for communication between Toxoplasma and its host, and to discuss new questions that arise out of these studies. [source] Molecular characteristics of an immobilization antigen gene of the fish-parasitic protozoan Ichthyophthirius multifiliis strain ARS-6AQUACULTURE RESEARCH, Issue 16 2009De-Hai Xu Abstract Ichthyophthirius multifiliis (Ich), a ciliated protozoan parasite of fish, expresses surface antigens (i-antigens), which react with host antibodies that render them immobile. The nucleotide sequence of an i-antigen gene of I. multifiliis strain ARS-6 was deduced. The predicted protein of 47 493 Da is comprised of 460 amino acids (aa's) arranged into five imperfect repeats with periodic cysteine residues with the structure: CX(19)20CX2CX16,27CX2CX20(21)CX3. The N-terminal aa's typify a signal peptide motif while a stretch of C-terminal aa's resemble a glycosyl,phosphatidyl,inositol (GPI)-anchor addition site. The degree of deduced i-antigen aa sequence identity of strain ARS-6 (GenBank accession # ACH87654 and # ACH95659) with other I. multifiliis i-antigen sequences present in GenBank ranges from 99% to 36% identity with 52 kDa i-antigens of I. multifiliis strain G5 (accession #s AAK94941 and AAK01661 respectively). Immunoblot analysis of i-antigens following exposure of I. multifiliis theronts to catfish anti- I. multifiliis immune serum did not show any appreciable alteration in i-antigen expression. The mechanism that regulates i-antigen expression in I. multifiliis remains a puzzling question. [source] Two crystal structures of dihydrofolate reductase-thymidylate synthase from Cryptosporidium hominis reveal protein,ligand interactions including a structural basis for observed antifolate resistanceACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2005Amy C. Anderson Cryptosporidium hominis is a protozoan parasite that causes acute gastrointestinal illness. There are no effective therapies for cryptosporidiosis, highlighting the need for new drug-lead discovery. An analysis of the protein,ligand interactions in two crystal structures of dihydrofolate reductase-thymidylate synthase (DHFR-TS) from C. hominis, determined at 2.8 and 2.87,Å resolution, reveals that the interactions of residues Ile29, Thr58 and Cys113 in the active site of C. hominis DHFR provide a possible structural basis for the observed antifolate resistance. A comparison with the structure of human DHFR reveals active-site differences that may be exploited for the design of species-selective inhibitors. [source] Chemotaxis of Entamoeba histolytica towards the pro-inflammatory cytokine TNF is based on PI3K signalling, cytoskeleton reorganization and the Galactose/N-acetylgalactosamine lectin activityCELLULAR MICROBIOLOGY, Issue 8 2008Samantha Blazquez Summary Entamoeba histolytica is the protozoan parasite responsible for human amoebiasis. During invasive amoebiasis, migration is an essential process and it has previously been shown that the pro-inflammatory compound tumour necrosis factor (TNF) is produced and that it has a migratory effect on E. histolytica. This paper focuses on the analysis of parasite signalling and cytoskeleton changes leading to directional motility. TNF-induced signalling was PI3K-dependent and could lead to modifications in the polarization of certain cytoskeleton-related proteins. To analyse the effect of TNF signalling on gene expression, we used microarray analysis to screen for genes encoding proteins that were potentially important during chemotaxis towards TNF. Interestingly, we found that elements of the galactose/N-acetylgalactosamine lectin (Gal/GalNAc lectin) were upregulated during chemotaxis as well as genes encoding proteins involved in cytoskeleton dynamics. The ,-actinin protein appeared to be an important candidate to link the Gal/GalNAc lectin to the cytoskeleton during chemotaxis signalling. Dominant negative parasites blocked for Gal/GalNAc lectin signalling were no longer able to chemotax towards TNF. These results have given us an insight on how E. histolytica changes its cytoskeleton dynamics during chemotaxis and revealed the capital role of PI3K and Gal/GalNAc lectin signalling in chemotaxis. [source] Immune response to leishmania: paradox rather than paradigmFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 2 2007Parul Tripathi Abstract The leishmaniases are a group of diseases caused by protozoan parasites of the genus Leishmania. Various Leishmania species can cause human infection, producing a spectrum of clinical manifestations. It is estimated that 350 million people are at risk, with a global yearly incidence of 1,1.5 million for cutaneous and 500 000 for visceral leishmaniasis (VL). VL is a major cause of morbidity and mortality in East Africa and the Indian subcontinent. Coinfection with HIV enhances the risk of the disease. The only control measure currently available in India is case detection and treatment with antimonial drugs, which are expensive, not always available and cannot be self-administered. Newer drugs like oral miltefosine have not become widely available. Vector and reservoir control is difficult due to the elusive nature of the vector and the diversity of the animal reservoir. A detailed knowledge of immune response to the parasite would help in designing prophylactic and therapeutic strategies against this infection. [source] Role of the Toll/interleukin-1 receptor signaling pathway in host resistance and pathogenesis during infection with protozoan parasitesIMMUNOLOGICAL REVIEWS, Issue 1 2004Ricardo T. Gazzinelli Summary:, Different studies have illustrated the activation of the innate immune system during infection with protozoan parasites. Experiments performed in vivo also support the notion that innate immunity has a crucial role in resistance as well as pathogenesis observed during protozoan infections such as malaria, leishmaniasis, toxoplasmosis, and trypanosomiasis. While major advances have been made in the assignment of bacterial molecules as Toll-like receptors (TLRs) agonists as well as defining the role of the Toll/interleukin-1 receptor (TIR) signaling pathway in host resistance to bacterial infection, this research area is now emerging in the field of protozoan parasites. In this review, we discuss the recent studies describing parasite molecules as TLR agonists and those studies indicating the essential role of the TIR-domain bearing molecule named myeloid differentiation factor 88 in host resistance to infection with protozoan parasites. Together, these studies support the hypothesis that the TIR signaling pathway is involved in the initial recognition of protozoan parasites by the immune system of the vertebrate host, early resistance to infection, development of acquired immunity, as well as pathology observed during acute infection with this class of pathogens. [source] Multiplex PCR detection of slowly-evolving trypanosomatids and neogregarines in bumblebees using broad-range primersJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2010I. Meeus Abstract Aims:, The aims of this study were to design universal markers for different protozoan parasites of Bombus spp. based on the phylogenetic position of two important bumblebee parasites Crithidia bombi and Apicystis bombi. Methods and Results:, Standard PCR and extraction techniques were used to amplify and sequence 18S rDNA. Phylogenetic analysis of the rDNA was performed in order to predict the parasite range of the primers. Conclusions:,Crithidia bombi phylogenetically clusters with the trypanosomatids with slowly-evolving SSU-rRNA sequences (SE), while A. bombi is the closest sister group of Mattesia. A multiplex was designed containing an internal control and two broad-range primer pairs, detecting C. bombi and other SE trypanosomatids and also A. bombi and other neogregarines. Significance and Impact of the Study:, Sequence data generated will further improve the current systematics of insect trypanosomatids and gregarines that remain troublesome. Broad-range markers for bumblebee parasites are necessary tools enabling the screening of commercially imported colonies and thus controlling their worldwide distribution and to discover related emerging parasites. [source] Gastrointestinal parasites of the grasscutter (Thryonomys swinderianus, Temminck 1827) on the Accra Plains of GhanaAFRICAN JOURNAL OF ECOLOGY, Issue 3 2009Theodora Kankam Abstract The gastrointestinal parasites of the grasscutter were investigated between 1996 and 2006 using 180 grasscutters from the Accra Plains. The aim of the study was to develop strategies for the control of the parasites under captive management. The gastrointestinal tracts of the animals were examined for the presence of both helminth and protozoan parasites with the aid of a hand lens, the direct smear and Willis Flotation techniques. In all, fourteen species of helminths were found including twelve nematodes and two cestodes. Trichuris muris was the most common nematode encountered, whilst Hepatocola hepatica was the least commonly encountered nematode. Three genera of protozoans, viz, Trichomonas spp, Giardia spp and Eimeria spp were also encountered, with Giardia spp and Trichomonas spp being reported for the first time in the grasscutter. Eimeria spp were the most prevalent protozoa. The widespread occurrence of protozoal and helminthic parasites in the grasscutter suggests that routine treatment of grasscutters with coccidiostats, anti-flagellates and anthelminthics such as dimetridazole and albendazole may contribute significantly to improve productivity of animals and reduce the pressure on wild populations. Résumé Les parasites gastro-intestinaux de l'aulacode ont étéétudiés entre 1996 et 2006 sur 180 animaux des plaines d'Accra. Le but de l'étude était de mettre au point des stratégies pour le contrôle des parasites en captivité. Le tractus gastro-intestinal des animaux fut examiné pour détecter la présence d'helminthes et de protozoaires parasites au moyen d'une lentille à main, par prélèvement direct et par la technique de flottaison de Willis. En tout, on a trouvé 14 espèces d'helminthes, y compris 12 nématodes et deux cestodes. Trichuris murisétait le nématode le plus commun tandis que Hepatocola hepaticaétait le nématode le moins observé. Trois genres de protozoaires, c.-à-d. Trichomonas spp, Giardia spp et Eimeriaspp furent aussi observés, Giardia spp et Trichomonas spp étant rapportés pour la première fois chez l'aulacode. Eimeria spp était le protozoaire le plus répandu. La large présence de protozoaires et d'helminthes parasites chez l'aulacode suggère que le traitement de routine des aulacodes avec des coccidiostats, des antiflagellés et des antihelmintiques tels que le dimétridazole et l'albendazole peut contribuer significativement à améliorer la productivité des animaux et à réduire la pression sur les populations sauvages. [source] Developmentally induced changes of the proteome in the protozoan parasite Leishmania donovaniPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 9 2003Meike Bente Abstract In order to proceed through their life cycle, protozoan parasites of the genus Leishmania cycle between sandflies and mammals. This change of environment correlates with the differentiation from the promastigote stage (insect form) to the amastigote stage (intracellular mammalian form). The molecular basis underlying this major transformation is poorly understood so far; however, heat shock protein 90 (HSP90) appears to play a pivotal role. To further elucidate this process we identified proteins expressed preferentially in either of the two life cycle stages. By using two-dimensional (2-D) gel electrophoresis we observed defined changes in the protein pattern. A total of approximately 2000 protein spots were visualized. Of these, 31 proteins were present only in promastigotes. The abundance of 65 proteins increased during heat-induced in vitro amastigote differentiation, while a decreased abundance is observed for four proteins late in amastigote differentiation. Further analyses using matrix-assisted laser desorption/ionization-time of flight mass spectrometry and peptide mass fingerprinting 67 protein spots were identified representing 41 different proteins known from databases and eight hypothetical proteins. Further studies showed that most of the stage-specific proteins fall into five groups of functionally related proteins. These functional categories are: (i) stress response (e.g. heat, oxidative stress); (ii) cytoskeleton and cell membrane; (iii) energy metabolism and phosphorylation; (iv) cell cycle and proliferation; and (v) amino acid metabolism. Very similar changes in the 2-D protein pattern were obtained when in vitro amastigote differentiation was induced either by pharmacological inhibition of HSP90 or by a combination of heat stress and acidic pH supporting the critical role for HSP90 in life cycle control. [source] Stress response pathways in protozoan parasitesCELLULAR MICROBIOLOGY, Issue 12 2008Nathalie Vonlaufen Summary Diseases caused by protozoan parasites have a dramatic impact on world health. Emerging drug resistance and a general lack of experimental understanding has created a void in the medicine cabinet used to treat these widespread infections. A novel therapeutic idea that is receiving more attention is centred on targeting the microbe's response to the multitude of environmental stresses it encounters. Protozoan pathogens have complex life cycles, often having to transition from one host to another, or survive in a cyst form in the environment until a new host arrives. The need to respond to environmental cues and stress, and endure in less than optimal conditions, is paramount to their viability and successful progression through their life cycle. This review summarizes the research on parasitic stress responses for Apicomplexa, kinetoplastids and anaerobic protozoa, with an eye towards how these processes may be exploited therapeutically. [source] Golgi biogenesis in simple eukaryotesCELLULAR MICROBIOLOGY, Issue 3 2007Cynthia Y. He Summary The accurate duplication of cellular organelles is important to ensure propagation through successive generations. The semi-conserved replication of DNA and DNA-containing organelles has been well studied, but the mechanisms used to duplicate most other organelles remain elusive. These include the centrosomes, which act as microtubule organizing centres during interphase and orient the mitotic spindle poles during mitosis. Centrosomes can also act as basal bodies, nucleating the growth of cilia or flagella. Even less understood are the mechanisms used to duplicate membrane-bound organelles that do not contain DNA. These include organelles involved in the secretory pathway such as the endoplasmic reticulum and the Golgi apparatus. This review will summarize the current knowledge of Golgi biogenesis in simple eukaryotic organisms, in particular, two protozoan parasites, Toxoplasma gondii and Trypanosoma brucei. [source] Histones and histone modifications in protozoan parasitesCELLULAR MICROBIOLOGY, Issue 12 2006William J. Sullivan Jr Summary Protozoan parasites are early branching eukaryotes causing significant morbidity and mortality in humans and livestock. Single-celled parasites have evolved complex life cycles, which may involve multiple host organisms, and strategies to evade host immune responses. Consequently, two key aspects of virulence that underlie pathogenesis are parasite differentiation and antigenic variation, both of which require changes in the expressed genome. Complicating these requisite alterations in the parasite transcriptome is chromatin, which serves as a formidable barrier to DNA processes including transcription, repair, replication and recombination. Considerable progress has been made in the study of chromatin dynamics in other eukaryotes, and there is much to be gained in extending these analyses to protozoan parasites. Much of the work completed to date has focused on histone acetylation and methylation in the apicomplexans and trypanosomatids. As we describe in this review, such studies provide a unique vantage point of the evolutionary picture of eukaryotic cell development, and reveal unique phenomena that could be exploited pharmacologically to treat protozoal diseases. [source] RNA interference in protozoan parasitesCELLULAR MICROBIOLOGY, Issue 6 2004Elisabetta Ullu Summary RNA interference or RNAi is defined as the mechanism through which gene-specific, double-stranded RNA (dsRNA) triggers degradation of homologous transcripts. Besides providing an invaluable tool to downregulate gene expression in a variety of organisms, it is now evident that RNAi extends its tentacles into both the nucleus and the cytoplasm and is involved in a variety of gene silencing phenomena. Here we review the current status of RNAi in protozoan parasites that cause diseases of considerable medical and veterinary importance throughout Africa, Asia and the Americas. RNAi was first discovered in Trypanosoma brucei, a species of the family Trypanosomatidae, and it rapidly became the method of choice to downregulate gene expression in these organisms. At the same time, mechanistic studies exposed a role for RNAi in the control of retroposon transcript abundance. Whereas RNAi is also present in T. congolense, other members of the same family of organisms, namely T. cruzi and Leishmania major, are RNAi-negative. In apicomplexan parasites, there is experimental evidence for RNAi in Plasmodium, but this is not supported by their genetic make up. In contrast, the genome of Toxoplasma gondii harbours gene candidates with convincing similarity to ,classical' RNAi genes. Thus, as previously shown in fungi, protozoan parasites are genetically heterogeneous as far as the RNAi pathway is concerned. Finally, database mining predicts that Entamoeba histolytica and Giardia intestinalis have an RNAi pathway and the presence of RNAi genes in Giardia supports the view that gene silencing by dsRNA appeared very early during evolution of the eukaryotic lineage. [source] Cytoplasmic tail motifs mediate endoplasmic reticulum localization and export of transmembrane reporters in the protozoan parasite Toxoplasma gondiiCELLULAR MICROBIOLOGY, Issue 6 2000Heinrich C. Hoppe In mammalian cells and yeasts, amino acid motifs in the cytoplasmic tails of transmembrane proteins play a prominent role in protein targeting in the early secretory pathway by mediating localization to or rapid export from the endoplasmic reticulum (ER). However, early sorting events are poorly characterized in protozoan parasites. Here, we show that a C-terminal QKTT sequence mediates the ER localization of chimeric reporter constructs consisting of bacterial alkaline phosphatase (BAP) fused to the transmembrane domain (TMD) and truncated cytoplasmic tail of the human low-density lipoprotein receptor (LDL) receptor or of murine lysosome-associated membrane protein (lamp-1) in Toxoplasma gondii. The cytoplasmic tail of human TGN46 also determines ER localization of BAP chimeras in the parasite, but this can be overcome by the addition at the C-terminus of the tail of an acidic patch, which functions as an ER export signal in conjunction with an upstream tyrosine motif. These results suggest that COPI-dependent ER retrieval and COPII-dependent export mechanisms mediated by KKXX and DXE motifs of mammalian cells are generally conserved in T. gondii. In contrast, the failure of the QKTT motif and TGN46 cytoplasmic tail to induce steady-state ER localization of vesicular stomatitis virus glycoprotein (VSVG) chimeras in HeLa and NRK cells indicates that significant differences in early secretory trafficking also exist. [source] | |||||||||||||||||||