Vaccination of dogs against Echinococcus granulosus, the cause of cystic hydatid disease in humans

Dogs are pivotal in Echinococcus granulosus transmission to humans, and dog vaccination provides a very practical and cost-effective prevention strategy. We vaccinated dogs with soluble native proteins isolated from protoscoleces of E. granulosus and induced significant suppression of worm growth and egg production. Accordingly, we tested for vaccine efficacy using recombinant proteins derived from a developmentally regulated gene family (egM) specifically expressed in mature adult E. granulosus worms. Three egM genes--egM4, egM9, and egM123--were subcloned into an expression vector that expressed the molecules as soluble glutathione S-transferase (GST) fusion proteins in Escherichia coli. The 3 fusion proteins were purified for dog vaccination trials (3 doses of 80 microg/protein/dog) in which the dogs were challenged and then necropsied 45 days after infection. Compared with worms in the control dogs that received GST, the 3 recombinant proteins induced a very high level of protection (97%-100%) in terms of suppression of worm growth and, especially, of egg development and embryogenesis. We have thus shown that vaccination of the dog host against E. granulosus is feasible when recombinant proteins are used. Because the egg stage is crucial in the echinococcal life cycle, successful suppression of egg development by vaccination would halt transmission to intermediate hosts, thereby effecting long-term control.

Tetraspanins on the surface of Schistosoma mansoni are protective antigens against schistosomiasis

Schistosomes are blood-dwelling flukes that infect 200 million people worldwide and are responsible for hundreds of thousands of deaths annually. Using a signal sequence trap, we cloned from Schistosoma mansoni two cDNAs, Sm-tsp-1 and Sm-tsp-2, encoding the tetraspanin (TSP) integral membrane proteins TSP-1 and TSP-2. We raised antibodies to recombinant TSP fusion proteins and showed that both proteins are exposed on the surface of S. mansoni. Recombinant TSP-2, but not TSP-1, is strongly recognized by IgG1 and IgG3 (but not IgE) from naturally resistant individuals but is not recognized by IgG from chronically infected or unexposed individuals. Vaccination of mice with the recombinant proteins followed by challenge infection with S. mansoni resulted in reductions of 57% and 64% (TSP-2) and 34% and 52% (TSP-1) for mean adult worm burdens and liver egg burdens, respectively, over two independent trials. Fecal egg counts were reduced by 65-69% in both test groups. TSP-2 in particular provided protection in excess of the 40% benchmark set by the World Health Organization for progression of schistosome vaccine antigens into clinical trials. When coupled with its selective recognition by naturally resistant people, TSP-2 seems to be an effective vaccine antigen against S. mansoni.

A contributory role for activated hepatic stellate cells in the dynamics of Schistosoma japonicum egg-induced fibrosis

The disease manifestations of schistosomiasis arise from the mammalian host-mediated type 2 T-helper cell-induced (Th2) fibro-granulomatous inflammatory response to eggs trapped within host tissues. Activated hepatic stellate cells are well described as the effector cells of hepatic fibrosis in a variety of human diseases and rodent models. The aim of this study was to further understand the mechanism of fibrosis and the role of hepatic stellate cells in hepatic schistosomiasis progression. Groups of female CBA mice, which produce an intermediate degree of Schistosoma japonicum-induced liver fibrosis, were infected with S. japonicum, perfused at fortnightly time points and the liver tissue and contained egg granulomas examined by immunohistochemistry and cytokine and chemokine analysis using quantitative PCR. Immunohistochemistry demonstrated the presence of activated hepatic stellate cells in the periphery of egg granulomas, adjacent to fibrotic areas. Time course analysis demonstrated that the transcription of smooth muscle actin-alpha type 1 collagen, IL-4, IL-13, IL-13Ralpha2 and tissue inhibitor of metalloproteinase-1 mirrored the initial increase and subsequent down-modulation of granuloma diameter in mice. However, the transcription of monocyte chemo-attractant protein-1, Regulated upon Activation Normal T Cell Expressed and Secreted (RANTES), TNF-alpha, IFN-gamma and matrix metalloproteinase-9 paralleled the evolution of the total liver disease burden. Transforming growth factor-beta1 transcription did not appear to be of biological significance in this mouse model. Immunohistochemical analysis of human hepatic granulomas showed close association of smooth muscle actin-alpha-expressing cells with fibrosis in five available cases of end-stage (advanced) schistosomiasis japonica. We conclude that activated hepatic stellate cells play a contributory role in the granulomatous, fibrotic process induced by S. japonicum eggs, both in the murine model and in human disease.

A survey of the intestinal transcriptomes of the hookworms, Necator americanus and Ancylostoma caninum, using tissues isolated by laser microdissection microscopy

The gastrointestinal tracts of multi-cellular blood-feeding parasites are targets for vaccines and drugs. Recently, recombinant vaccines that interrupt the digestion of blood in the hookworm gut have shown efficacy, so we explored the intestinal transcriptomes of the human and canine hookworms, Necator americanus and Ancylostoma caninum, respectively. We used Laser Microdissection Microscopy to dissect gut tissue from the parasites, extracted the RNA and generated cDNA libraries. A total of 480 expressed sequence tags were sequenced from each library and assembled into contigs, accounting for 268 N. americanus genes and 276 A. caninum genes. Only 17% of N. americanus and 36% of A. caninum contigs were assigned Gene Ontology classifications. Twenty-six (9.8%) N. americanus and 18 (6.5%) A. caninum contigs did not have homologues in any databases including dbEST-of these novel clones, seven N. americanus and three A. caninum contigs had Open Reading Frames with predicted secretory signal peptides. The most abundant transcripts corresponded to mRNAs encoding cholesterol-and fatty acid-binding proteins, C-type lectins, Activation-Associated Secretory Proteins, and proteases of different mechanistic classes, particularly astacin-like metallopeptidases. Expressed sequence tags corresponding to known and potential recombinant vaccines were identified and these included homologues of proteases, anti-clotting factors, defensins and integral membrane proteins involved in cell adhesion.

Identification of membrane-bound and secreted proteins from Echinococcus granulosus by signal sequence trap

The signal sequence trap technique was applied to identify genes coding for secreted and membrane bound proteins from Echinococcus granulosus, the etiologic agent of cystic hydatid disease. An E. granulosus protoscolex cDNA library was constructed in the AP-PST vector such that randomly primed cDNAs were fused with a placental alkaline phosphatase reporter gene lacking its endogenous signal peptide. E. granulosus cDNAs encoding a functional signal peptide were selected by their ability to rescue secretion of alkaline phosphatase by COS-7 cells that had been transfected with the cDNA library. Eighteen positive clones were identified and sequenced. Their deduced amino acid sequences showed significant similarity with amino acid transporters, Krebs cycle intermediates transporters, presenilins and vacuolar protein sorter proteins. Other cDNAs encoded secreted proteins without homologues. Three sequences were transcribed antisense to E. granulosus expressed sequence tags. All the mRNAs were expressed in protoscoleces and adult worms, but some of them were not found in oncospheres. The putative E. granulosus secreted and membrane bound proteins identified are likely to play important roles in the metabolism, development and survival in the host and represent potential targets for diagnosis, drugs and vaccines against E. granulosus.

Brain metastasis of alveolar echinococcosis in a hyperendemic focus of Echinococcus multilocularis infection

An unusual female case, with alveolar echinococcosis (AE) disseminated from the primary hepatic lesion to the brain by metastasis formation, was retrospectively identified during a community survey in Ningxia Hui Autonomous Region, northwest China in 2003. Among possible metastases of hepatic AE, locations to the brain are rare and usually fatal; and they have especially been assigned to concomitant immune suppression. An enhancing role of pregnancy, which may be suspected in this case, the favourable outcome after surgery and chemotherapy, and also a mental disability in a child following long-term intrauterine exposure to mebendazole, make the report particularly unique.

Two isoforms of a divalent metal transporter (DMT1) in Schistosoma mansoni suggest a surface-associated pathway for iron absorption in schistosomes

We describe two homologues of the mammalian divalent metal transporter (DMT1) for Schistosoma mansoni, a pathogenic intravascular parasite of humans. Schistosomes have a high nutritional and metabolic demand for iron. Nucleotide sequences of the parasite homologues, designated SmDMT1A and -B, are identical in all but the 5'-regions. The predicted amino acid sequences share at least 60% identity with DMT1 (=Nramp2) of humans, mice, and rats, and at least 55% identity with Nramp1 from mice, humans and Caenorhabditis elegans. SmDMT1A is expressed in differentiating eggs, miracidia, cercariae, schistosomula, and adults, whereas SmDMT1B is expressed in all but the miracidium and occurs at lower levels than SmDMT1A in differentiating eggs and cercariae. An iron-responsive element, present at the 3'-untranslated region of many DMT1 molecules, is not present in schistosome mRNAs studied here. A Western blot analysis of adult worm preparations using a homologous rabbit serum raised against a schistosome DMT1 peptide and a heterologous serum raised against mammalian DMT1, revealed a band approximating 115 kDa. By immunofluorescence microscopy, the schistosome DMT1s localize primarily to the tegument. Iron uptake assays demonstrated that SmDMT1s were able to rescue yeast growth in ferrous iron-transport deficient yeast (fet3fet4). The results suggest that schistosomes express molecules for ferrous iron transport in their tegument, suggesting trans-tegumental transport as one means of iron acquisition for these parasites.

Recoil polarization for delta excitation in pion electroproduction

We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W = 1.23 GeV at Q(2) = 1.0 (GeV/c)(2), obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S(1+)/M(1+)) = -(6.84 +/- 0.15)% and Re (E(1+)/M(1+)) = -(2.91 +/- 0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ll(pi) < or = 1 truncation.

The cellular distribution and stage-specific expression of two dynein light chains from the human blood fluke Schistosoma japonicum

Schistosomes are pathogenic helminth parasites of human portal veins. Their body wall is a highly active syncytial tegument involved in an array of host interactions. The cytoskeletal organization and dynamics of this syncytium are poorly understood, but predominant motor components are the LC8 class of cytoplasmic dynein light chains (DLC). Four LC8 members occur in schistosomes, two of which are expressed in the tegument. Here, we describe the cytoplasmic distribution, stage-specific expression and cellular location of two diverse LC8 molecules of Schistosoma japonicum. SjDLC1 was detected in surface-membrane specific extracts of adult worms and was shown by quantitative immuno-electron microscopy to predominate along heptalaminate membranes of the worm surface. SjDLC3 also occurs in the tegument, but was shown to be present in basal layers of the tegument and did not preferentially co-localize with particular membrane components. SjDLC3 was also detected in the gastrodermis. SjDLC1 is expressed only in mammalian-parasitic stages, whereas SjDLC3 is expressed throughout the life-cycle. The data suggest that SjDLC1 is preferentially located to the host-interactive distal parasite membrane, and plays a role in surface membrane dynamics, while SjDLC3 is a ubiquitous motor component of schistosome epithelia of all stages.

Quasielastic 3He(e,e'p)2H reaction at Q2 = 1.5 GeV2 for recoil momenta up to 1 GeV/c

We have studied the quasielastic 3He(e,e(')p)2H reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The 3He(e,e(')p)2H cross section was measured for missing momenta up to 1000 MeV/c, while the A(TL) asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern 3He wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The A(TL) asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.

Echinococcus granulosus: pre-culture of protoscoleces in vitro significantly increases development and viability of secondary hydatid cysts in mice

We describe a method for obtaining improved secondary infections of Echinococcus granulosus that involves culturing protoscolex larvae in vitro prior to inoculation into mice. This approach provides a far superior method for obtaining secondary echinococcosis infections in mice compared with the traditional method of direct inoculation of protoscoleces (PSC) where the majority of parasites are killed by the host. We obtained a high rate of recovery both in terms of secondary cyst numbers and their viability. After 50 weeks post-infection (p.i.), brood capsules were formed and the first PSC developed in each of the capsules. After 56 weeks p.i., the fastest developing brood capsule contained four PSC. The approach will prove valuable for investigating parasite development and the host-parasite interaction in secondary echinococcosis.

Precision Rosenbluth measurement of the proton elastic form factors

We report the results of a new Rosenbluth measurement of the proton electromagnetic form factors at Q2 values of 2.64, 3.20, and 4.10 GeV2. Cross sections were determined by detecting the recoiling proton, in contrast to previous measurements which detected the scattered electron. Cross sections were determined to 3%, with relative uncertainties below 1%. The ratio mu(p)G(E)/G(M) was determined to 4%-8% and showed mu(p)G(E)/G(M) approximately 1. These results are consistent with, and much more precise than, previous Rosenbluth extractions. They are inconsistent with recent polarization transfer measurements of similar precision, implying a systematic difference between the techniques.

Measurement of the 3He(e,e'p)pn reaction at high missing energies and momenta

Results of the Jefferson Lab Hall A quasielastic 3He(e,e'p)pn measurements are presented. These measurements were performed at fixed transferred momentum and energy, q=1502 MeV/c and omega=840 MeV, respectively, for missing momenta p(m) up to 1 GeV/c and missing energies in the continuum region, up to pion threshold; this kinematic coverage is much more extensive than that of any previous experiment. The cross section data are presented along with the effective momentum density distribution and compared to theoretical models.

Terminology of the sucker-like organs of the scolex of trypanorhynch cestodes

The literature associated with descriptions and definitions of the sucker-like attachment organs in trypanorhynchs, termed either bothria or bothridia, is reviewed. There are descriptions of 14 trypanorhynch species representing 10 families. In none of these trypanorhynchs was a membrane separating the attachment organ from the scolex parenchyma described, one of the definitions used to distinguish bothria from bothridia. Transmission electron microscopy of the bothria of the trypanorhynch species Nybelinia queenslandensis Beveridge & Jones, 1998 (Tentaculariidae) and Otobothrium mugilis Hiscock, 1954 (Otobothriidae) also failed to show any membranous structure separating the surface of the attachment organ from the cestode parenchyma. The sucker-like attachment organs of trypanorhynchan cestodes appear, therefore, to be bothria rather than bothridia. As a result, changes in the terminology of related features of the scolex are proposed here. Henceforth, the pars bothridialis should be referred to as the pars bothrialis and the bothridial pits should be referred to bothrial pits.

Effect of cyclosporin A on the survival and ultrastructure of Echinococcus granulosus protoscoleces in vitro

Surgical treatment of human hydatidsosis involves the use of various scolicidal agents to kill infective Echinococcus granulosus protoscoleces that may disseminate into the peritoneal cavity during surgery and potentially re-infect the patient. Currently, no scolicidal agent is completely effective in killing intracystic protoscoleces in humans. Cyclosporin A (CsA) has previously been found to be lethal for E. granulosus protoscoleces in vitro. In this study, we further assessed the effectiveness of CsA as a scolicidal agent by testing the toxic effect of CsA at higher doses over various time-periods. Experiments were performed on activated and unactivated protoscoleces cultured in nutrient medium or sheep hydatid cyst fluid. All activated protoscoleces were killed following culture in 100 microg/ml of CsA for 3 days and 50 or 20 microg/ml for 5 days. The lethal effect of CsA on unactivated protoscoleces varied but reached 100% over 15 days in culture with 100 or 50 microg/ml of CsA. Pulse treatment of protoscoleces with 50, 20 or 10 microg/ml of CsA for 5 min or 72 h killed all parasites by day 10 and day 5 respectively. Untreated protoscoleces remained greater than 95 % viable for the duration of experiments. Changes in protoscolex ultrastructure induced by treatment with 10 microg/ml of CsA over 10 days in in vitro culture was assessed by TEM. Protoscolex alterations observed in treated parasites included an increase in cellular vacuolization, swelling of mitochondria, rounding of cells, damage to the tegument, decrease in glycogen, a breakdown of the extracellular matrix and an increase in lipid globules. The untreated protoscoleces, by comparison, had few changes during the 10-day culture period with the exception of large amounts of extracellular glycogen observed in the protoscoleces at culture days 7 and 10. From these results, CsA is clearly an effective scolicidal agent in vitro that may have potential application as a new therapeutic agent in the treatment of human hydatid disease.

Measurement of the generalized polarizabilities of the proton in virtual Compton scattering at Q2=0.92 and 1.76 GeV2

We report a virtual Compton scattering study of the proton at low c.m. energies. We have determined the structure functions P(LL)-P(TT)/epsilon and P(LT), and the electric and magnetic generalized polarizabilities (GPs) alpha(E)(Q2) and beta(M)(Q2) at momentum transfer Q(2)=0.92 and 1.76 GeV2. The electric GP shows a strong falloff with Q2, and its global behavior does not follow a simple dipole form. The magnetic GP shows a rise and then a falloff; this can be interpreted as the dominance of a long-distance diamagnetic pion cloud at low Q2, compensated at higher Q2 by a paramagnetic contribution from piN intermediate states.

The cytoskeleton and motor proteins of human schistosomes and their roles in surface maintenance and host-parasite interactions

Schistosomes are parasitic blood flukes, responsible for significant human disease in tropical and developing nations. Here we review information on the organization of the cytoskeleton and associated motor proteins of schistosomes, with particular reference to the organization of the syncytial tegument, a unique cellular adaptation of these and other neodermatan flatworms. Extensive EST databases show that the molecular constituents of the cytoskeleton and associated molecular systems are likely to be similar to those of other eukaryotes, although there are potentially some molecules unique to schistosomes and platyhelminths. The biology of some components, particular those contributing to host-parasite interactions as well as chemotherapy and immunotherapy are discussed. Unresolved questions in relation to the structure and function of the tegument relate to dynamic organization of the syncytial layer.

A pore-forming haemolysin from the hookworm, Ancylostoma caninum

Hookworms feed on blood, but the mechanism by which they lyse ingested erythrocytes is unknown. Here we show that Ancylostoma caninum, the common dog hookworm, expresses a detergent soluble, haemolytic factor. Activity was identified in both adult and larval stages, was heat-stable and unaffected by the addition of protease inhibitors, metal ions, chelators and reducing agents. Trypsin ablated lysis indicating that the haemolysin is a protein. A closely migrating doublet of hookworm proteins with apparent molecular weights of 60-65 kDa bound to the erythrocyte membrane after lysis of cells using both unlabeled and biotinylated detergent-solubilised hookworm extracts. In addition, separation of detergent-soluble parasite extracts using strong cation-exchange chromatography, resulted in purification of 60-65 kDa proteins with trypsin-sensitive haemolytic activity. Erythrocytes lysed with particulate, buffer-insoluble worm extracts were observed using scanning electron microscopy and appeared as red cell ghosts with approximately 100 nm diameter pores formed in the cell membranes. Red blood cell ghosts remained visible indicating that lysis was likely caused by pore formation and followed by osmotic disruption of the cell.

The ultrastructural architecture of the adult Schistosoma japonicum tegument

The tegument of the adult blood fluke Schistosoma japonicum is in direct contact with the host blood and immune systems. A comprehensive understanding of the ultrastructure of the tegument is crucial to the understanding of how the parasite maintains itself within the mammalian host. Important functions such as nutritional uptake and immune evasion are suspected functions of the tegument and this review discusses these aspects and presents some insights into some of these crucial functions. Transmission electron microscopy has allowed the identification of ultrastructural features of the adult S. japonicum, some of which differ from the reported features of other schistosome species. Morphological differences within the tegument of the adult S. japonicum are noted between sexes, among different regions of the worms and between aspects along the length of the parasite. Differences included variations in the ultrastructure, size and number of tegumental bodies and mitochondria within the matrix, and differences in the relative area of the apical surface of the tegument. Functions of the various components of the tegument matrix and specialised functions of different regions of the male and female parasites are discussed based on ultrastructural findings and previously reported biochemical and molecular data.

Human melanoblasts in culture: expression of BRN2 and synergistic regulation by fibroblast growth factor-2, stem cell factor, and endothelin-3

The BRN2 transcription factor (POU3F2, N-Oct-3) has been implicated in development of the melanocytic lineage and in melanoma. Using a low calcium medium supplemented with stem cell factor, fibroblast growth factor-2, endothelin-3 and cholera toxin, we have established and partially characterised human melanocyte precursor cells, which are unpigmented, contain immature melanosomes and lack L-dihydroxyphenylalanine reactivity. Melanoblast cultures expressed high levels of BRN2 compared to melanocytes, which decreased to a level similar to that of melanocytes when cultured in medium that contained phorbol ester but lacked endothelin-3, stem cell factor and fibroblast growth factor-2. This decrease in BRN2 accompanied a positive L-dihydroxyphenylalanine reaction and induction of melanosome maturation consistent with melanoblast differentiation seen during development. Culture of primary melanocytes in low calcium medium supplemented with stem cell factor, fibroblast growth factor-2 and endothelin-3 caused an increase in BRN2 protein levels with a concomitant change to a melanoblast-like morphology. Synergism between any two of these growth factors was required for BRN2 protein induction, whereas all three factors were required to alter melanocyte morphology and for maximal BRN2 protein expression. These finding implicate BRN2 as an early marker of melanoblasts that may contribute to the hierarchy of melanocytic gene control.

Measurements of GnE/GnM from the 2H(e-->,en-->)1H Reaction to Q2=1.45 (GeV/c)2

We report new measurements of the ratio of the electric form factor to the magnetic form factor of the neutron, G(n)(E)/G(n)(M), obtained via recoil polarimetry from the quasielastic 2H(e-->,e(')n-->)1H reaction at Q2 values of 0.45, 1.13, and 1.45 (GeV/c)(2) with relative statistical uncertainties of 7.6% and 8.4% at the two higher Q2 points, which points have never been achieved in polarization measurements.

Polarization transfer in the 4He(e-->,e'p-->)3H reaction up to Q2=2.6 (GeV/c)2

We have measured the proton recoil polarization in the 4He(e-->,e(')p-->)4H reaction at Q(2)=0.5, 1.0, 1.6, and 2.6 (GeV/c)(2). The measured ratio of polarization transfer coefficients differs from a fully relativistic calculation, favoring the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model. In addition, the measured induced polarizations agree reasonably well with the fully relativistic calculation indicating that the treatment of final-state interactions is under control.

2H(e,e(')p)n reaction at high recoil momenta

The 2H(e,e(')p)n cross section was measured in Hall A of the Thomas Jefferson National Accelerator Facility near the top of the quasielastic peak (x(Bj)=0.964) at a four-momentum transfer squared, Q(2)=0.665 (GeV/c) (2) (omega=0.368 GeV, W=2.057 GeV), and for recoil momenta up to 550 MeV/c. The measured cross section deviates by 1-2sigma from a state-of-the-art calculation at low recoil momenta. At high recoil momenta the cross section is well described by the same calculation; however, in this region, final-state interactions and interaction currents are predicted to be large, and alternative choices of nucleon-nucleon potential and nucleon current operator may result in significant spread in the calculations.