bluuebunny/crossref_metadata_2025 huggingface dataset:
Interspecific differences in the nematode surface coat betweenMeloidogyne incognitaandM. arenariarelated to the adhesion of the bacteriumPasteuria penetrans
Authors: Davies K. G. , Danks C.
Published: June 2009

Spores of the bacteriumPasteuria penetransadhered to second-stage juveniles of bothMeloidogyne incognitaandM. arenaria, but in standard attachment assays far fewer adhered to the latter species. Similarly, a polyclonal antibody was shown not to recognize the surface coat ofM. arenariabut did recognize the surface coat ofM. incognita. Although the incubation of whole, intact 2nd-stage juveniles ofM. incognitain a series of detergents and protein-denaturing agents at room temperature did not reduce the number of spores adhering after exposure to the bacterium, incubation in buffer (PBS) alone at 100 °C for 2 min did. Immunoblotting of cuticle extracts onto nitrocellulose and probing the blots with antibody showed that the antibody recognized a large protein ofMr80 kDa and a series of smaller proteins of approximately 43 kDa onM. incognitawhich were not recognized in extracts fromM. arenaria. As incubation of the 2nd-stage juveniles in antibody prohibited spore attachment it is suggested that these proteins may be involved in spore adhesion. Large differences exist betweenM. incognitaandM. arenariain the amounts of surface-associated proteins on the 2nd-stage juvenile cuticle.
Purification and properties of phosphoenolpyruvate carboxylase from Molinema dessetae (Nematoda: Filarioidea)
Authors: Loiseau P. M. , Gayral P. , Petek F.
Published: June 2009

The presence of phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31), an enzyme at the branchpoint of glycolysis and the Krebs cycle was detected in the Filaria Molinema dessetae. This enzyme has not previously been identified in Helminths, which have so far been found to only possess a phosphoenolpyruvate carboxykinase (EC 4.1.1.32). This enzyme had a level of activity comparable to that of pyruvate kinase, and was relatively less active than enzymes such as malate dehydrogenase or lactate dehydrogenase. We propose here a method of purification of M. dessetae PEP-carboxylase. When purified to electrophoretic homogeneity, the enzyme had a molecular weight of 64 kDa. Kinetic studies indicated that the carboxylation reaction had an optimal pH of 5·8. The enzyme was inhibited by cations such as Fe2+, Zn2+, Cd2+, Cu2+ but required the presence of Mg2+ or Mn2+. The enzyme was thermostable. The apparent Km value of 2·38 mmol for phosphoenolpyruvate for the carboxylation reaction was higher than previously reported values. The Km value for KHCO3 was found to be 1·6 mmol. PEP-carboxylase did not catalyse the reverse reaction.
Pharmacological profile of the 5-hydroxytryptamine receptor ofFasciola hepaticabody wall muscle
Authors: Tembe E. A. , Holden-Dye L. , Smith S. W. G. , Jacques P. A. M. , Walker R. J.
Published: June 2009

5-HT is a candidate for the excitatory transmitter at the neuromuscular junction in trematodes includingFasciola hepatica.This study has determined the response of a muscle strip preparation fromFasciola hepaticato 5-HT and a range of agonists that distinguish between the vertebrate receptor 5-HT subtypes. 5-HT increased the resting tone and the rhythmic activity of the muscle strip. Of the 19 compounds tested, only 10 had an effect similar to 5-HT and all but 2 of these were tryptamine compounds. 5-HT was more potent than tryptamine whilst 4-OH-tryptamine had no effect, suggesting that the response is mediated by a 5-HT rather than a tryptamine receptor. 5-Fluorotryptamine and 5-carboxyamidotryptamine were the most potent agonists. 8-OH-DPAT also mimicked the effect of 5-HT, though less potently. Assuming that these agents elicit their response through a common receptor, this suggests the presence of a 5-HT receptor with similar properties in terms of agonist recognition as the vertebrate 5-HT1class of receptor involved in controllingFasciolamuscle motility.
Trypanosoma (Nannomonas) congolense: molecular characterization of a new genotype from Tsavo, Kenya
Authors: Majiwa P. A. O. , Maina M. , Waitumbi J. N. , Mihok S. , Zweygarth E.
Published: June 2009

Trypanosoma (Nannomonas) congolense comprises morphologically identical but genetically heterogeneous parasites infective to livestock and other mammalian hosts; three different genotypes of this parasite have been described previously. Restriction enzyme fragment length polymorphisms (RFLPs) in both kinetoplast DNA minicircle and nuclear DNA sequences, and randomly amplified polymorphic deoxyribonucleic acid (RAPD) patterns have been used here to demonstrate the existence of another type of T. (N.) congolense that is genotypically distinct from those that have so far been characterized at the molecular level. A highly repetitive, tandemly arranged DNA sequence and oligonucleotide primers, for use in polymerase chain reaction (PCR) amplification are described, which can be used for specific identification of the trypanosome and its distinction from others within the Nannomonas subgenus.
Leishmaniasis epidemiology: the theory catches up
Authors: Dye C.
Published: June 2009

Until recently, almost all studies of leishmaniasis epidemiology were qualitative and descriptive. But now that the natural history of manyLeishmaniaparasites is quite well known, there is growing interest in quantitative analysis. In this paper I use mathematical models in conjunction with field data to try to answer a wider range of questions than has previously been possible with descriptive techniques, and to sharpen some of the outstanding questions for laboratory workers. This is done with reference to the persistence and resilience of canine leishmaniasis, the maintenance of virulence poly morphisms inLeishmaniapopulations, and the possible existence of cycles of human kala-azar. I conclude by posing a set of problems under three headings: diagnosis of infection (as distinct from disease), natural immunity toLeishmaniainfection in the vertebrate host, and genetic variation in the parasite population. Some solutions from the laboratory can be found in the companion paper by Black (1992).
Malaria-a neglected disease?
Authors: Marsh K.
Published: June 2009

In situations where malaria eradication is not an option in the foreseeable future the emphasis must be on the control of morbidity and mortality due to malaria. Under such circumstances drawing a distinction between malarial parasitization and malarial disease may be important for workers in both field and laboratory. This concept is explored from the points of view of the epidemiological picture of malaria in endemic populations, the factors which may influence progression to disease and the processes which mediate disease.
Intestinal nematode infections in children: the pathophysiological price paid
Authors: Cooper E. S. , Whyte-Alleng C. A. M. , Finzi-Smith J. S. , MacDonald T. T.
Published: June 2009

The mechanism by which small animals such as rodents resist or eliminate nematode parasites requires mucosal in flammation as the final effector of the immune response. The resulting freedom from chronic infection may be worth the price of short-term illness. Putative vaccines which attempt to enhance the natural effect will have to take into account the inflammatory cost to the host. Human helminthiases involve a more stable equilibrium between host and parasite. The medical literature on hookworm disease and clinical ascariasis describes, for the former, some chronic inflammatory effects correlated with worm burden, but for the latter a less quantified or predictable set of detrimental effects. We describe a current, systematic study of the inflammatory response to whipworm infection, in which anaemia, growth retardation and intestinal leakiness are viewed as predictable consequences related to infection intensity. There is evidence for the absence of cell-mediated immunopathology. However, a specific, IgE-mediated local anaphylaxis may, at least partly, mediate the deleterious effects. Increased numbers of mucosal macrophages may also contribute to the chronic, systemic effects through their output of cytokines. Similar attempts to show the mechanisms of pathogenesis and quantify the effects of hookworm disease should be undertaken.
Cyclosporin A: antiparasite drug, modulator of the host-parasite relationship and immunosuppressant
Authors: Chappell L. H. , Wastling J. M.
Published: June 2009

Cyclosporin A (CsA), a cyclic undecapeptide with powerful properties of immunosuppression, acts on parasitic infections in laboratory animals in various ways. The outcome of drug administrationin vivovaries with timing of treatment relative to infection, route of administration, dose and number of treatments applied. CsA is clearly antiparasitic against malaria, schistosomes, adult tapeworms, metacestodes and filarial nematodes. By contrast, it acts as an immunomodulator against trypanosomes andGiardia, by exacerbating infection; in the case ofLeishmaniaspp. the drug acts variously. In some other infections CsA acts both as an antiparasite drug and as an immunosuppressant (Toxoplasma, avian coccidiosis and gastrointestinal nematodes).
Immune-dependent chemotherapy of schistosomiasis
Authors: Fallon P. G. , Cooper R. O. , Probert A. J. , Doenhoff M. J.
Published: June 2009

Host immune responses have been shown to enhance the efficacy of several schistosomicidal drugs. The evidence derives mainly from experiments onSchistosoma mansoniinfections in the mouse with their immune status variously modulated; this review emphasises praziquantel (PZQ), which is now the main drug used for treatment of human schistosomiasis. Electron microscopy and indirect immunofluorescence indicate that PZQ disrupts the integrity of the surface membranes ofS. mansoni, particularly those covering the dorsal tubercles of adult male worms, and this causes antigens which are the targets of antibody attack to be revealed. We review the evidence that twoS. mansoniantigens in particular are implicated in the immune-dependent action of PZQ: a 200 kDa glycoprotein and a 27 kDa antigen with non-specific esterase activity.
Diethylcarbamazine (DEC): immunopharmacological interactions of an anti-filarial drug
Authors: Maizels R. M. , Denham D. A.
Published: June 2009

Anti-parasitic drugs may achieve their therapeutic effect either by direct activity against the pathogenic organism, or by altering host factors which lead to parasite killing. In this review, we discuss the evidence for an indirect mode of action for one major anti-filarial drug, diethylcarbamazine (DEC). The interpretation most consistent with existing data is that DEC alters arachidonic acid metabolism in microfilariae and in host endothelial cells. These changes may result in vasoconstriction and amplified endothelial adhesion leading to immobilization of microfilarial parasites, enhanced adherence and cytotoxic activity by host platelets and granulocytes. These events would represent activation of the innate, non-specific immune system, independent of the adaptive, antigen-specific, immune response. This model explains the paradox between rapid clearancein vivoand the lack of anin vitroeffect, as well as the efficacy of DEC in non-immune animals.
Interactions between immunity and chemotherapy in the treatment of the trypanosomiases and leishmaniases
Authors: Berger B. J. , Fairlamb A. H.
Published: June 2009

The immune status of a host infected withTrypanosomaspp. orLeishmaniaspp. can play an important role in successful chemotherapy. In animal models, treatment of African trypanosomiasis with difluoromethylornithine or melarsoprol requires an appropriate antibody-mediated immune response. An intact immune system is also necessary for rapid clearance of trypanosomes from the bloodstream following treatment with suramin or quinapyramine. Similarly, an efficient cell-mediated immune response is required for maximal efficacy of pentavalent antimonials in the treatment of leishmaniasis. However, the potential relationship between parasite-induced or acquired immunosuppression and effective chemotherapy has been poorly studied. Macrophages which have been activated by bacterial cell wall components or gamma-interferon are known to display increased activity againstLeishmania donovaniorTrypanosoma cruzi. In experimental and clinical visceral leishmaniasis, use of macrophage activators together with pentavalent antimonials has lowered the dose of antimony required to cure the infection.
Human nutrition needs and parasitic infections
Authors: Nesheim M. C.
Published: June 2009

The series of articles that follow in this volume deals with specific aspects of how parasites might influence nutrient utilization by their human hosts. To put these aspects of parasitic disease in context, this contribution is intended to provide an overview of human nutritional needs and to introduce concepts of how nutritional consequences of parasitic infection might be viewed. Although parasitic diseases are often considered to be those caused by protozoa and helminths, the principles considered here can be applied to any infectious agent, including bacteria and viruses.
Molecular mechanisms of sequestration in malaria
Authors: Berendt A. R. , Ferguson D. J. P. , Gardner J. , Turner G. , Rowe A. , McCormick C. , Roberts D. , Craig A. , Pinches R. , Elford B. C. , Newbold C. I.
Published: June 2009

Cell surface molecules have received intense attention in recent years because of the central roles they play at the interface between the external environment and the cellular interior. Their functions include adhesion to other cells or extracellular matrices, protection against hostile physical, chemical and biological agents and the transport of metabolites into and out of the cell. In addition, cell surface molecules transduce signals across the cell membrane, relaying information inwards and presenting altered characteristics to the exterior as the environment changes.
Maintenance of a microparasite infecting several host species: rabies in the Serengeti
Authors: Cleaveland S. , Dye C.
Published: June 2009

Whether and how microparasites such as rabies persist in their host populations are among the fundamental questions of infectious disease epidemiology. Rabies is a fatal disease of all mammalian species, but not all mammalian species can maintain the infection as reservoirs. The approach to control depends on which of the affected species do act as reservoirs. Bringing together old and new data, we examine here the role of wild and domestic animals in maintaining rabies in the Serengeti region of Tanzania, presenting our findings in two parts. In Part I, we argue that domestic dogs are the likely reservoirs because: (1) rabies has been continuously present in the dog population since its (re)introduction in 1977, whilst (2) wildlife cases have been very rare over this period, despite intensive study of Serengeti carnivores; (3) outbreaks of rabies in wild canids (jackals) elsewhere in Africa (Zimbabwe) have followed, rather than preceded, outbreaks in the dog population; (4) all viruses isolated from wild carnivores in the Serengeti ecosystem (including the Kenyan Masai Mara) are antigenically and genetically indistinguishable from the typical domestic dog Strain; (5) dog rabies control in the Serengeti between 1958–77 apparently eliminated the disease from both dogs and wildlife. Having identified dogs as reservoirs, Part II explores some possible mechanisms of maintenance in dog populations. In theory, infection is more likely to be maintained at higher dog densities, and we provide evidence that rabies is maintained in one district with a dog density > 5/km2, but not in two other districts with densities < 1/km2. Because 5 dogs/km2is much lower than the expected density required for persistence, we go on to investigate the role of atypical infections, showing: (1) from serology, that a substantial proportion of healthy dogs in the Serengeti have detectable serum levels of rabies-specific antibody; (2) from mathematical models that, whilst we cannot be sure what seropositivity means, persistence in low-density dog populations is more likely if seropositives are infectious carriers, rather than slow-incubators or immunes.
Modelling patterns of parasite aggregation in natural populations: trichostrongylid nematode–ruminant interactions as a case study
Authors: Grenfell B. T. , Wilson K. , Isham V. S. , Boyd H. E. G. , Dietz K.
Published: June 2009

The characteristically aggregated frequency distribution of macroparasites in their hosts is a key feature of host–parasite population biology. We begin with a brief review of the theoretical literature concerning parasite aggregation. Though this work has illustrated much about both the sources and impact of parasite aggregation, there is still no definitive analysis of both these aspects. We then go on to illustrate the use of one approach to this problem – the construction of Moment Closure Equations (MCEs), which can be used to represent both the mean and second moments (variances and covariances) of the distribution of different parasite stages and phenomenological measures of host immunity. We apply these models to one of the best documented interactions involving free-living animal hosts – the interaction between trichostrongylid nematodes and ruminants. The analysis compares patterns of variability in experimental infections ofTeladorsagia circumcinctain sheep with the equivalent wildlife situation – the epidemiology ofT. circumcinctain a feral population of Soay sheep on St Kilda, Outer Hebrides. We focus on the relationship between mean parasite load and aggregation (inversely measured by the negative binomial parameter,k) for cohorts of hosts. The analysis and empirical data indicate thatktracks the increase and subsequent decline in the mean burden with host age. We discuss this result in terms of the degree of heterogeneity in the impact of host immunity or parasite-induced mortality required to shorten the tail of the parasite distribution (and therefore increasek) in older animals. The model is also used to analyse the relationship between estimated worm and egg counts (since only the latter are often available for wildlife hosts). Finally, we use these results to review directions for future work on the nature and impact of parasite aggregation.
Infrapopulation dynamics of Gyrdicotylus gallieni (Monogenea: Gyrodactylidae)
Authors: Jackson J. A. , Tinsley R. C.
Published: June 2009

Gyrdicotylus gallieni is a viviparous gyrodactylid monogenean that infects the buccal cavity and pharynx oi Xenopus laevis laevis. Offspring directly recolonize the same host as their parent and transmission is carried out exclusively by adult worms which are capable of leech-like stepping locomotion. The infrapopulation dynamics (at 20 °C) of this species were studied by experimental exposure to single worms of previously uninfected hosts (which were dissected at various time intervals post-infection). Infrapopulations increased exponentially until 50 days post-infection (p.i.), during which time the intrinsic rate of increase was estimated by regression as 0·065/parasite/day. After this, infrapopulation sizes showed greater variability, with established infections becoming extinct 2–5 months p.i.: elimination was probably due to someform of host reaction, as parasite lineages were maintained for up to 10 months by transfers to successive uninfected hosts.The development of infrapopulations is similar to that reported for other viviparous gyrodactylids parasitic on the bodysurface of teleosts. However, the intrinsic rate of increase was comparatively slow in G. gallieni and the duration of infection in isolated hosts prolonged. Slow-growing infrapopulations may elicit a host response more slowly and extend the period during which dispersal to a new host or host population can occur. This might be important in G. gallieni for which the internal site of infection could limit the transmission rate, as worm migration from the oral cavity or accidental detachment and expulsion is necessary for host-host transfer to occur. Exposure of wild caught X. l. laevis of unknown infectionhistory to 1 (n = 33) or 10 (n = 10) worms produced only 2 established infrapopulations (in both cases hosts initially infected by single worms), compared with establishment of over 60% in naive hosts infected with single worms: this suggests that host resistance may be an important factor in the population dynamics of G. gallieni.
Magnesium deficiency protects againstBabesia hylomysciand mice become resistant to rechallenge with the parasite regardless of diet fed
Authors: Maurois P. , Delcourt P.H. , Gueux E. , Rayssiguier Y.
Published: June 2009

Mice were fed diets containing 960 mg (control), 100 mg (moderately Mg deficient) and 30 mg (severely Mg deficient) of Mg/kg. After 20 days, mice were inoculated withBabesia hylomysci(from Dr Wery, Anvers, Belgium). Significant increases in RBC Mg levels were observed following infection. All the control and moderately deficient mice died from infection, whereas the severely Mg-deficient diet protected mice against infection, as shown by a decrease in parasitaemia and mortality. The decrease in RBC Mg, modifications in membrane properties and increased oxidant stress are possible explanations for the protective effect of severe Mg deficiency. When mice were maintained for 2 months after inoculation on a severely Mg-deficient diet and were then switched to a control diet, all survived and had low parasitaemias. After 1 month, these mice were rechallenged withB. hylomysciand 89% survived.
Toxoplasma gondii-structure variations of the antigen P30
Authors: Bonhomme A. , Thirion C. , Boulanger F. , Charton F. , Burlet H. , Pinon J. M. , Alix A. J. P.
Published: June 2009

The major surface immunodominant antigen (P30) ofToxoplasma gondiiwas purified by two methods (i) SDS–PAGE and (ii) immunoaffinity chromatography. The secondary elements within this protein were assessed by circular dichroism and spectra obtained were compared to those proposed by Manavalan & Johnson (1983). The results allowed us to determine an all β protein status for this antigen. This experimental result was in agreement with the predicted secondary structures deduced from the P30 primary sequence. Modifications in conformation according to pH and temperature were recorded without any change in immunoactivity. The epitope, which was always recognized by a monoclonal antibody against P30, could be a linear epitope.
Intermembrane lipid transfer duringTrypanosoma cruzi-induced erythrocyte membrane destabilization
Authors: Luján H. D. , Bronia D. H.
Published: June 2009

The ability ofTrypanosoma cruzito induce erythrocyte membrane destabilizationin vitrowas studied. Epimastigote forms adhered to human erythrocytes and caused fusion or lysis of the red cells, depending on the conditions of the interaction. Red cells were fused in the presence of calcium, while haemolysis was induced in the absence of the cation. Dextran 60 C facilitated fusion but delayed lysis. Optimum pH and temperature for fusion were 7·4 and 37 °C, respectively. Lipid alterations were produced in the plasma membrane of the red cell during the interaction with the parasite. A Ca2+-independent increase of lysophospholipids and free fatty acids was common to both the lysis and fusion processes. A relative increase of 1, 2-diacylglycerides was unique to the fusion process and these changes were dependent on Ca2+. The transfer of free fatty acids and lysophospholipids fromT. cruzito erythrocyte membranes was demonstrated using parasites pre-labelled with radioactive phospholipids. Pre-treatment of parasites with exogenous phospholipase A2abolished the fusogenicity, while lysis was increased. Neither fusion nor haemolysis occurred when the parasites were pre-treated with fatty acid free albumin, phospholipase A2inhibitors or when these compounds were present in the medium during the parasite-erythrocyte interaction. Our results suggest thatT. cruziinduces erythrocyte membrane destabilizationin vitroby transfer of lipid material in a calcium independent manner and that this ion is necessary for other membrane alterations that lead to erythrocyte fusion.
Comparative analysis of full-length antigen II/3 fromEchinococcus multilocularisandE. granulosus
Authors: Felleisen R. , Gottstein B.
Published: June 2009

The recombinantEchinococcus multilocularisantigen ll/3–10 is one of the most promising tools for immunodiagnosis of alveolar echinococcosis in human patients. Its nucleic acid sequence represents a part of theE. multilocularisgene encoding the metacestode antigen II/3, the former being basically present and expressed in bothE. multilocularisandE. granulosus. Most (94%) patients with alveolar echinococcosis respond to infection with a marked anti-II/3–10 IgG synthesis; in contrast, most of the cystic echinococcosis patients do not, for some reason, recognize the recombinant antigen. We tackled this problem by generating cDNA derived from bothE. granulosusandE. multilocularisfull length II/3 genes, performed by reverse transcription and PCR amplification. Sequence analysis revealed a very high degree of conservation of the primary sequence of the antigen II/3 in bothEchinococcusspecies. cDNA fragments were subcloned and expressed inE. colias fusion proteins withSchistosoma japonicumglutathione S-transferase. Recombinant proteins were affinity purified and comparatively assessed by ELISA with respect to antibody-binding characteristics. Sera from patients suffering from cystic echinococcosis showed no significant differences in reactivity with the antigens derived from eitherE. multilocularisorE. granulosus. Therefore, parameters other than some minor differences in the primary sequence seem to be responsible for the lack of antigen II/3 recognition in cystic echinococcosis.

Note

Nucleotide sequence data reported in this paper have been submitted to the GenBank®data base with the accession numbers U05573 and U05574.
Characterization of peptidases of adultTrichuris muris
Authors: Drake L. J. , Bianco A. E. , Bundy D. A. P. , Ashall F.
Published: June 2009

Excretory/secretory (E/S) material ofTrichuris muriswas found to contain 2 major peptidases,Mr85 and 105 kDa, which degrade gelatin optimally at pH 6·0 in sodium dodecyl sulphate–polyacrylamide gels. The peptidases were inactivated diisopropylfluorophosphate, leupeptin and soybean trypsin inhibitor, but were unaffected by inhibitors of aspartic-, cysteine- and metallo-peptidases, indicating that they are serine peptidases. Both enzymes were detectable within 5 h after incubation of worms in culture medium and showed a time-dependent increase in levels. Neither peptidase was detected in worm extracts, suggesting that they are activated during or following secretion from worms. Live worms degraded radio-isotope labelled extracellular matrix protein substratum derived from mammalian cells. Aminopeptidase activities capable of catalysing hydrolysis of amino acyl aminomethylcoumarin (MCA) substrates and a Z-Phe-Arg-MCA-hydrolysing cysteine peptidase activity, were detected in extracts of adult worms but not in E/S material.
Characterization of the cysteine proteinases of the common liver flukeFasciola hepaticausing novel, active-site directed affinity labels
Authors: McGinty A. , Moore M. , Halton D. W. , Walker B.
Published: June 2009

The excreted/secreted proteinases of adult and juvenileFasciola hepaticamaintainedin vitrowere found to hydrolyse the fluorogenic substrates Cbz-Phe-Arg- and Cbz-Arg-Arg-NHMec. This activity was demonstrated to have a classical cysteine proteinase inhibitor profile, with turn-over of both substrates being blocked by pre-incubation with E64 and peptidyl diazomethanes. The Cbz-Arg-Arg-NHMec hydrolysing activity of the mature fluke exhibited an alkaline stability not characteristic of its mammalian lysosomal counterparts. Further, the biotinylated affinity reagents biotin-Phe-Ala- CHN2and biotin-Phe-Cys(SBzyl)-CHN2were used to label and characterize these cysteine proteinases in terms of apparent molecular weight and subsite specificity. Adult fluke media were found to contain four species of molecular weights 66, 58, 50 and 25–26 kDa; juvenile media contained three species of molecular weights 66, 54 and 25–26 kDa. The major 25–26 kDa cysteine proteinase common to both stages was shown to have a subsite specificity similar to that of mammalian cathepsin B.
Plasmodium falciparum lacks sialidase and trans-sialidase activity
Authors: Clough B. , Atilola F. A. , Healy N. , Pereira M. E. A. , Bethell R. C. , Penn C. R. , Pasvol G.
Published: June 2009

Sialic acid on the red cell surface plays a major role in invasion by the malaria parasite Plasmodium falciparum. The NeuAc(α2,3) Gal motif on the O-linked tetrasaccharides of the red cell glycophorins is a recognition site for the parasite erythrocyte-binding antigen (EBA-175). Consequently, the interaction of P. falciparum and the red cell might share homology with that of the influenza virus. The cellular interactions of P. falciparum were examined for their sensitivity to 4-guanidino-2,3-didehydro-D-N-acetyl neuraminic acid (4-guanidino Neu5Ac2en), a potent inhibitor of influenza virus sialidase. Parasite invasion and subsequent development was unaffected by the sialidase inhibitor. The inhibitor did not affect rosette formation of parasite-infected erythrocytes with uninfected cells nor their cytoadherence to C32 melanoma cells. Furthermore, we were unable to confirm the presence of a previously reported parasite sialidase using sensitive fluorometric or haemagglutination assays, neither was any malarial trans-sialidase identified. We conclude that P. falciparum possesses neither sialidase nor trans-sialidase activity and that an inhibitor of influenza virus sialidase has no effect on important cellular interactions of this parasite.
Characterization of the first European isolate ofNeospora caninum(Dubey, Carpenter, Speer, Topper and Uggla)
Authors: Barber J. S. , Holmdahl O. J. M. , Owen M. R. , Guy F. , Uggla A. , Trees A. J.
Published: June 2009

Neospora caninumis an apicomplexan, protozoan parasite, which causes severe disease in dogs and cattle. It has previously been isolated only in the United States. A 5-week-old Boxer pup with a progressive hindlimb paresis was diagnosed as suffering from neosporosis on the basis of clinical signs and the presence of anti-Neosporaantibodies in it, 2 litter-mates and its darn. Despite treatment with sulphonamides, the pup was euthanased 3 days later. The diagnosis of neosporosis was confirmed by immunohistochemical examination of muscle and CNS tissue sections from the pup. Parasites were isolated into Vero cell culture from the cerebrum, and confirmed asNeospora caninumby immunofluorescence with specific antibody, tachyzoite ultrastructure and 16S-like ribosomal RNA sequences. This isolate (designated NC-Liverpool) has been continuously passaged every 7–10 days. Its growth characteristics, ultrastructure and antigenic profile, as revealed by immunoblotting, have revealed no major differences from the American NC-1 isolate. Furthermore, no difference was seen when comparing the sequences of 16S-like ribosomal RNA and the ITS1 region of the two isolates.
Improved specificity ofTrypanosoma cruziidentification by polymerase chain reaction using an oligonucleotide derived from the amino-terminal sequence of a Tc24 protein
Authors: Taibi A. , Guevara-Espinoza A. , Schöneck R. , Yahiaoui B. , Ouaissi A.
Published: June 2009

In the present study, the diagnostic value ofTrypanosoma cruzirecombinant protein (Tc24) was examined. Although antibodies against Tc24 were detected during natural and experimentalT. cruziinfections, specificity studies revealed that sera fromT. rangeli-infected mice also recognized to some extent Tc24 protein. In addition, sera from Tc24-immunized mice reacted against a 21 kDa polypeptide inT. rangeliextracts. Detailed analysis of the antibody response against 20—40 peptide localized in the Tc24 amino-terminal domain suggests that this sequence is not expressed byT. rangeli21 kDa antigen. Therefore, the PCR reaction using oligonucleotides corresponding to a 20–26 peptide clearly demonstrated the specificity of the oligoprobes forT. cruziidentification. Positive signals were also found when using blood samples fromT. cruzi-infected mice. Taken together, these results suggest that the PCR-based 20–26 assay may be useful in the specific diagnosis of Chagas' disease.
Nuclear rDNA ITS sequence variation in the trematode genus Echinostoma: an aid to establishing relationships within the 37-collar-spine group
Authors: Morgan J. A. T. , Blair D.
Published: June 2009

The taxonomic history of members of the 37-collar-spine group within the genus Echinostoma has been very confused. We obtained DNA sequence data from the nuclear rDNA ITS1, 5·8S and ITS2 of 7 nominal species belonging to this group, Echinostoma trivolvis (Cort, 1914), E. revolution (Frölich, 1802), E. caproni Richard, 1964, E. liei Jeyarasasingam et al. 1972, E. paraensei Lie & Basch, 1967, two African isolates, E. sp.I and E. sp.II, and of one 28-collar-spined echinostome, E. hortense (Asada, 1926). Five of the eight species were clearly distinguishable using ITS data. Sequences from the remaining three taxa, E. caproni, E. sp.II and E. liei were identical to one another and the group containing these taxa was distant from other 37-collar-spine species on a phylogenetic tree. E. trivolvis and E. paraensei form a second, but less distinct group within the 37-collar-spine group. The resolution obtained using DNA sequencing will assist in the current reclassification of the group. It also provides a model for future work on sibling species.
Estimating the number of multiple-species geohelminth infections in human communities
Authors: Booth M. , Bundy D. A. P.
Published: June 2009

Infections with Ascaris lumbricoides, Triclmris trichiura and the hookworm species are often found in the same communities and individuals. Hosts infected by more than one species are potentially at risk of morbidity associated with each infection. This paper describes the use of a probabilistic model to predict the prevalence of multiple-species infections in communities for which only overall prevalence data exist. The model is tested against field data, using log-linear analysis, and is found to be more effective at estimating the numbers of multiple infections involving hookworms than those involving only A. lumbricoides and T. trichiura. This latter combination of infections is found, in half the communities examined, to be more common than expected by chance. An age-stratified analysis reveals that the degree of interaction between these two infections does not alter significantly with age in the child age classes of a Malaysian population.
Characterization and localization of Schistosoma mansoni calreticulin Sm58
Authors: Khalife J. , Liu J. L. , Pierce R. , Porchet E. , Godin C. , Capron A.
Published: June 2009

Recombinant Schistosoma mansoni calreticulin (SmCaR) was expressed in Escherichia coli, using the glutathione S-transferase fusion protein, and its Ca2+-binding capacity was determined. Results obtained by a 45Ca2+ overlay technique showed that Ca2+-binding site(s) were present in the recombinant CaR indicating that proper folding of the protein was obtained using this system. An antiserum raised against the recombinant SmCaR showed that the native protein (Sm58) was expressed in all stages of the life-cycle from cercariae to the adult worm and in the egg. However, SmCaR seems to be a developmentally regulated protein whose expression can be used to study the post-transformational differentiation of the schistosomulum. Localization of SmCaR demonstrated that the majority of SmCaR was expressed in the epithelia of the digestive duct and in the genital organs. These results suggest that SmCaR, by regulating the Ca2+ concentration, may play an important role during cell proliferation. Finally the presence of SmCaR in miracidia and in the genital organs suggests that the antibody response directed against this protein could interfere in egg production.
Molecular characterization of twoSchistosoma mansoniproteins sharing common motifs with the vif protein of HIV-1
Authors: Khalife J. , Pierce R. J. , Godin C. , Capron A.
Published: June 2009

We have previously described a rat mAb directed against a peptide derived from the vif protein of HIV-1 that recognized twoSchistosoma mansoni(Sm) antigens with a major band at 65 kDa. Epitope mapping of this mAb using overlapping hexapeptides derived from the vif peptide revealed that the motif recognized was PLPSVT. The screening of a Sm cDNA library led to the identification of two clones, Sm70 and Sm65. The two deduced protein sequences did not share any common structural features apart from the epitope recognized by the mAb (see below), and did not show significant identity to sequences present in the data bases. However, the N terminus of the deduced sequence of the Sm70 protein exhibits a consensus sequence known to be an ATP/GTP binding site. Furthermore, the C terminus of the deduced Sm65 protein sequence was found to contain a conserved hexapeptide with a consensus sequence LPETGE reported to be an important motif of the surface proteins of gram-positive cocci. Both proteins exhibit a peptide sequence (PLRSVT for Sm70 and PVGSVT for Sm65) similar to the epitope recognized by the mAb anti-vif. Western blotting experiments showed that the mAb anti-vif reacted with both proteins. However, only Sm65 was recognized by sera from HIV-1- seropositive individuals, whereas both proteins were recognized by S.mansoni-infectedpatients.
The kinetics of repeated low-level infections of Nippostrongylus brasiliensis in the laboratory rat
Authors: Jenkins D. Conwil , Phillipson R. F.
Published: June 2009

The kinetics of low-level repeated infections of Nippostrongylus brasiliensis in the laboratory rat were studied.

The administration of five infective larvae each weekday to the rats produced an infection which was cumulative over 16 weeks and which did not produce an acute host immune response.

The repeated administration of 50 larvae/weekday produced a primary immune response after 14 days. This caused partial worm expulsion and the suppression of egg output but the resistance of these rats to reinfection was not as pronounced as that seen in classical laboratory infections where heavier but less frequent larval exposures are used. The secondary worms that established in these rats did not elicit an acute host immune response even when the worm burden was as high as 756 worms.

It is suggested that the kinetics of this type of infection more closely approximate those found under natural conditions than do those of a ‘classical’ laboratory infection.

We wish to thank Misses G. Merchant, L. Cleaver and J. Cobb for able technical assistance, and Dr B. M. Ogilvie (National Institute for Medical Research, Mill Hill, London) for her helpful comments and discussions.
Aggregation in schistosomiasis: comparison of the relationships between prevalence and intensity in different endemic areas
Authors: Guyatt H. L. , Smith T. , Gryseels B. , Lengeler C. , Mshinda H. , Siziya S. , Salanave B. , Mohome N. , Makwala J. , Ngimbi K. P. , Tanner M.
Published: June 2009

Distributions of the intensities of helminth infections within their host populations are invariably aggregated. In the case of the intestinal nematodes, the degrees of aggregation have been shown to be species specific, and constant for any given species despite geographical variation in study sites. This species-specific aggregation can be quantified and used as a tool in planning control interventions. One practical application is that the prevalence of infection can be used to predict the prevalence of heavy infection and thus the risks of morbidity. This paper investigates the patterns of aggregation in schistosome egg counts in different endemic areas in Africa (data sets were obtained from Burundi, Cameroon, Tanzania, Zambia and Zaire). The analysis demonstrates that the degree of parasite aggregation, for bothSchistosoma mansoniandS. haematobium, differs amongst the different study localities. This is probably due to area-specific differences in host exposure and immunity. This implies that for these schistosome species, it is not possible to predict egg count distributions or morbidity levels from prevalence data alone.
A dipeptidylpeptidase secreted byFasciola hepatica
Authors: Carmona C. , McGonigle S. , Dowd A. J. , Smith A. M. , Coughlan S. , McGowran E. , Dalton J. P.
Published: June 2009

A dipeptidylpeptidase (DPP) was isolated fromFasciola hepaticaby gel-filtration and ion-exchange chromatography. The exoproteinase is secreted by newly excysted juveniles, immature and mature flukes. The liver fluke DPP is a serine proteinase of molecular weight > 200 kDa and differs from previously characterized mammalian DPPs in its substrate preference and susceptibility to inactivation by inhibitors. The parasite DPP may function in the latter stages of the proteolytic digestion of host macromolecules. In this manner, the enzyme may be important in providing the parasite with dipeptides that could be absorbed through the intestine as nutrient.
Evolution and overview of classical transmitter molecules and their receptors
Authors: Walker R. J. , Brooks H. L. , Holden-Dye L.
Published: June 2009

All the classical transmitter ligand molecules evolved at least 1000 million years ago. With the possible exception of the Porifera and coelenterates (Cnidaria), they occur in all the remaining phyla. All transmitters have evolved the ability to activate a range of ion channels, resulting in excitation, inhibition and biphasic or multiphasic responses. All transmitters can be synthesised in all three basic types of neurones, i.e. sensory, interneurone and motoneurone. However their relative importance as sensory, interneurone or motor transmitters varies widely between the phyla. It is likely that all neurons contain more than one type of releasable molecule, often a combination of a classical transmitter and a neuroactive peptide. Second messengers, i.e. G proteins and phospholipase C systems, appeared early in evolution and occur in all phyla that have been investigated. Although the evidence is incomplete, it is likely that all the classical transmitter receptor subtypes identified in mammals, also occur throughout the phyla. The invertebrate receptors so far cloned show some interesting homologies both between those from different invertebrate phyla and with mammalian receptors. This indicates that many of the basic receptor subtypes, including benzodiazepine subunits, evolved at an early period, probably at least 800 million years ago. Overall, the evidence stresses the similarity between the major phyla rather than their differences, supporting a common origin from primitive helminth stock.
Functional morphology of the platyhelminth nervous system
Authors: Halton D. W. , Gustafsson M. K. S.
Published: June 2009

As the most primitive metazoan phylum, the Platyhelminthes occupies a unique position in nervous system evolution. Centrally, their nervous system consists of an archaic brain from which emanate one or more pairs of longitudinal nerve cords connected by commissures; peripherally, a diverse arrangement of nerve plexuses of varying complexity innervate the subsurface epithelial and muscle layers, and in the parasitic taxa they are most prominent in the musculature of the attachment organs and egg-forming apparatus. There is a range of neuronal-cell types, the majority being multi- and bipolar. The flatworm neuron is highly secretory and contains a heterogeneity of vesicular inclusions, dominated by densecored vesicles, whose contents may be released synaptically or by paracrine secretion for presumed delivery to target cells via the extracellular matrix. A wide range of sense organ types is present in flatworms, irrespective of life-styles. The repertoire of neuronal substances identified cytochemically includes all of the major candidate transmitters known in vertebrates. Two groups of native flatworm neuropeptides have been sequenced, neuropeptide F and FMRFamide-related peptides (FaRPs), and immunoreactivities for these have been localised in dense-cored neuronal vesicles in representatives of all major fiatworm groups. There is evidence of co-localisation of peptidergic and cholinergic elements; serotoninergic components generally occupy a separate set of neurons. The actions of neuronal substances in flatworms are largely undetermined, but FaRPs and 5-HT are known to be myoactive in all of the major groups, and there is immuno-cytochemical evidence that they have a role in the mechanism of egg assembly.
Metabolism and inactivation of neurotransmitters in nematodes
Authors: Isaac R. E. , Macgregor D. , Coates D.
Published: June 2009

The nematode nervous system employs many of the same neurotransmitters as are found in higher animals. The inactivation of neurotransmitters is absolutely essential for the correct functioning of the nervous system, In this article we discuss the various mechanisms used generally in animal nervous systems for synaptic inactivation of neurotransmitters and review the evidence for similar mechanisms operating in parasitic and free-living nematodes. The sequencing of the entireCaenorhabditis elegansgenome means that the sequence of nematode genes can be accessed from theC. elegansdatabase (ACeDB) and this wealth of information together with the increasing knowledge of the genetics of this free-living nematode will have great impact on all aspects of nematode neurobiology. The review will provide an insight into how this information may be exploited to identify and characterize target proteins for the development of novel anti-nematode drugs.
Cell relationships in Hymenolepis diminuta
Authors: Threadgold L. T. , Read C. P.
Published: June 2009

The intimate cell relationships of Hymenolepis diminuta are described and occur between cells of the parenchyma, excretory system, muscle and tegument. The cell relationships are of three types: (a) a tight junction or zonula occludens; (b) a desmosome-like structure without tonofibrils or intercellular dense line; (c) a junctional complex with modified unit membranes and an intercellular region of dense granules and fibres.

This research was begun while one of us (L.T.T.) was a Visiting Lecturer in the Biology Department, Rice University, and completed in the Zoology Department, Queen's University, Belfast. We should like to thank Dr C. W. Philpott for allowing us the full use of the facilities of his electron-microscope unit and Mr W. Ferguson for photographic assistance.