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B Betschart

Publications and source records attributed to B Betschart.

At least 19 recordsLinked to original sources
PubMed2004

Prospect for anthelminthic plants in the Ivory Coast using ethnobotanical criteria.

Sixty plant species were collected in the Ivory Coast on the basis of an ethnobotanical literature using the following three criteria: activity against worms, diarrhoea and/or abdominal pain. Eighty six plant extracts were prepared using 90% ethanol and tested for potential anthelminthic activities with a larvicidal test of Haemonchus contortus. 25.6% of the extracts showed a high activity, 12.8% were active or marginally active and the remaining 61.6% were inactive. The fact that a relatively high percentage of the plants species (50%) had an activity can be explained by the initial preselection of the plants on the basis of ethnobotanical indications.

Animals↗
PubMed2003

Prophylaxis failure due to probable mefloquine resistant P falciparum from Tanzania.

Failures of mefloquine prophylaxis in travellers returning from Africa have been reported repeatedly. Non-compliance to chemoprophylaxis is considered to be a major factor for failure. Only few reports on mefloquine prophylaxis failure in sub-Saharan Africa were able to report blood levels of the drug that were sufficient for prophylactic effectiveness. We report the case of a 44-year-old German female who travelled to Tanzania for 3 weeks. The patient reported that she never missed a dose of mefloquine during her weekly prophylaxis schedule. Four weeks after returning from Tanzania, the patient presented with fever, headache and myalgia. Only a few trophozoites of Plasmodium falciparum were found in a thick film. Blood levels of mefloquine at that stage were at 1400 ng/ml, thus largely excluding non-compliance and malabsorption. To our knowledge, this is the first case of confirmed prophylaxis failure due to mefloquine resistance in East Africa.

Adult↗
PubMed2002

Seasonal epidemiology of ticks and aspects of cowdriosis in N'Dama village cattle in the Central Guinea savannah of Côte d'Ivoire.

In the Central Guinea savannah of Côte d'Ivoire, cattle breeding started only approximately 30 years ago. The impact of parasitism on the overall health status and productivity of the trypanotolerant N'Dama cattle in this area is unknown. In close collaboration with national veterinary institutions and local farmers, we studied spectrum, burden and seasonal dynamics of ticks (including aspects of cowdriosis) on N'Dama village cattle. In a longitudinal study, three randomly selected cattle herds (traditional farming type) of one village were examined repeatedly for ticks. Spectrum, burden, seasonal epidemiology of ticks were assessed. In these traditional herds (which lack (ecto)parasite management), all animals were infested by ticks at monthly counts. Five different tick species were identified; the four genera in order of frequency were: Amblyomma (overall prevalence 96%), Boophilus (47%), Hyalomma (<1%) and Rhipicephalus (<1%). Amblyomma variegatum was the most-abundant tick on cattle in all seasons. Seroprevalence of Cowdria ruminantium was 31% (95% CI: 26, 36%). Most of the animals typically carried low tick burdens. N'Dama cattle seem well adapted to their environment and can resist the tick burdens under this traditional farming system.

Animals↗
PubMed2001

Isolation, characterisation and organisation of histone H1 genes in African trypanosomes.

A tandemly arranged gene family coding for histone H1 in African trypanosomes is described. Many variants, differing by some substitutions and/or deletions in their monotone and repetitive amino acid sequences, are found. The different variants can be sorted into three subtypes using their N-terminal region. PCR amplification experiments with primers specific to these three H1 subtypes suggest that the genes may be separated into two transcriptional units. Heterogeneity among species, subspecies and even strains was found. The transcripts are polyadenylated and the trans-splicing site is located very closely to the start codon. The intergenic regions are typical when compared to other polycistronic clusters described in trypanosomes. Amino acid sequence motifs may explain differences seen in chromatin compaction patterns between African and American trypanosomes.

Amino Acid Sequence↗
PubMed2000

The synthetic, oxidized C-terminal fragment of the Plasmodium berghei circumsporozoite protein elicits a high protective response.

A polypeptide of 69 amino acids (PbCS 242-310) encompassing the C-terminal region of the circumsporozoite protein of Plasmodium berghei (PbCS) was generated using solid-phase peptide synthesis. The immunological and protective properties of peptide PbCS 242-310 were studied in BALB/c mice (H-2d). Two subcutaneous injections, in the presence of IFA at the base of the tail, generated (i) high titers of anti-peptide antibodies which also recognized the native P. berghei CS protein, (ii) cytolytic T cells specific for the Kd-restricted peptide PbCS 245-253 and (iii) partial CD8+-dependent protection against sporozoite-induced malaria. The same frequencies of peptide PbCS 245-253 specific CD8+ T cells were found by IFN-gamma ELISPOT in the draining lymph nodes of animals immunized with the short optimal CTL peptide 245-253 or with the polypeptide 242-310, indicating that the longer polypeptide can be processed and presented in vivo in the context of MHC class I as efficiently as the short CTL peptide. Interestingly, higher levels of IFN-gamma producing CD8 T cells and protection were observed when the four cysteine residues present in the C-terminal peptide were fully oxidized. These findings underline the potential importance of the chemical nature of the C-terminal fragment on the activation of the immune system and concomitant protection.

Animals↗
PubMed1998

DNA extraction from Ascaris suum muscle tissue.

A new method for the extraction of DNA from Ascaris suum muscle has been developed. It combines a standard SDS-based extraction with a plant DNA extraction procedure. The use of SDS and proteinase K allows the elimination of proteins, while CTAB and polyclar AT eliminate glycogen and polyphenols. The DNA thus obtained can easily be digested by endonucleases and amplified by PCR.

Animals↗
PubMed1997

Elimination of P. berghei liver stages is independent of Fas (CD95/Apo-I) or perforin-mediated cytotoxicity.

Immunization of mammals with irradiated malaria sporozoites protects from a subsequent contact with the parasite. Protective immunity is directed against the pre-erythrocytic stages of the parasite, sporozoites and liver stages. Specific antibodies neutralize part of the infectious sporozoites infected by the mosquito vector, while liver stages are the target of a cellular immune response which is mediated by T cells. In this study, we evaluated the T-cell dependent protection induced by the infection of P. berghei irradiated sporozoites and the contribution of perforin and of the receptor/ligand system CD95/CD95L, two T cell-dependent mechanisms known to mediate elimination of target cells. Wild type, perforin deficient, CD95 mutant, CD95L mutant and perforin deficient/CD95L mutant mice were immunized with P. berghei irradiated sporozoites and submitted to a challenge with infectious sporozoites. All mice immunized with P. berghei irradiated sporozoites were protected against a sporozoite challenge, including perforin deficient/CD95L mutant animals. These results indicate that T cells do not kill malaria-infected hepatocytes via one of the known pathways, but rather that activated parasite-specific T cells produce cytokines which activate in cascade other mechanisms responsible for the intracellular elimination of the parasite.

Animals↗
PubMed1996

Repetitive peptide motifs in the cuticlin of Ascaris suum.

The cuticle of parasitic nematodes is composed of extracellular structural proteins. Over 90% of these proteins are collagenous molecules in the basal and median layers of the cuticle. The outermost layers of the cuticle, the epicuticle, is composed of non-collagenous proteins, that represent the structural surface of nematodes. In Ascaris these proteins have been termed 'cuticlins'. While cuticular collagens have been well studied by both biochemical and genetic means, knowledge of the molecular structure of cuticlin components of parasitic nematodes is scarce. In the present paper we report on the production of monoclonal antibody 8.1, which is specific for cuticlin, but does not recognize collagen epitopes. We have screened a cDNA library derived from adult Ascaris suum mRNA of the hypodermal tissue underlying and synthesizing the cuticle. One positive cDNA clone encodes alanine-rich repetitive motifs, which are part of the insoluble cuticlin of the outermost layers of the epicuticle of Ascaris suum. This was shown in immunocytochemical experiments using specific polyclonal antisera raised against these motifs, expressed as fusion protein with glutathione S-transferase of the helminth Schistosoma japonicum. Comparison of the repetitive amino acid sequence with structural proteins of the nematode Caenorhabditis elegans and the insects Locusta migratoria and Ceratitis capitata revealed a minimal consensus motif.

Amino Acid Sequence↗
PubMed1996

Identification and sequence comparison of a cuticular collagen of Brugia pahangi.

The cuticle of filarial nematodes is a specialized extracellular matrix that covers the parasite and protects it from adverse conditions of the environment. As a surface structure it is in direct contact with the host defence mechanisms and therefore plays an important role in the molecular host-parasite relationship. Using polyclonal antisera raised against the insoluble components of the cuticle of the adult filarial parasite Brugia pahangi, we have isolated cDNA clones encoding collagen molecules of the cuticle. The protein domain structure of cDNA clone Bpcol-1 was compared with the known structures of cuticular collagens of the nematodes Brugia malayi, Caenorhabditis elegans, Ascaris suum and Haemonchus contortus, confirming interspecies similarities. Using affinity-purified anti-Bpcol-1 antibodies we identified Bpcol-1 antigenic determinants in different nematode extracts, and determined the localization of such epitopes within the cuticle of B. pahangi.

Amino Acid Sequence↗
PubMed1996

Ascaris suum: molecular cloning of an intermediate filament.

It has been proposed that intermediate filament proteins are involved in force transduction from the muscle cells through the hypodermis to the cuticle of nematodes. An additional role of intermediate filaments as excretory/secretory components of parasitic nematodes is under discussion. We report on the molecular characterization of the cDNA clone AsIF of the intestinal nematode parasite Ascaris suum, encoding a member of the intermediate filament protein family by sequence comparison with intermediate filaments of other nematodes. We also show the precise location of the product encoded by AsIF within the organism by immunoelectron microscopy.

Amino Acid Sequence↗
PubMed1995

Developmental changes in the circumsporozoite proteins of Plasmodium berghei and P. gallinaceum in their mosquito vectors.

The circumsporozoite (CS) protein covers the surface of the sporozoite of plasmodia. Its role in the development of the malaria parasite in mosquito vectors remains unknown. CS-epitope-containing proteins appear on undifferentiated oocysts on day 7 in Plasmodium berghei and on day 5 in P. gallinaceum as demonstrated by indirect fluorescence antibody tests using monoclonal antibodies directed against the CS-protein repeats. The three-dimensional distribution of the CS-epitope-containing proteins on oocysts was analyzed by confocal scanning laser microscopy. A strong antibody binding was found in patches around the oocysts of P. berghei and P. gallinaceum, and an accumulation of labeled proteins was found at the base of the oocysts of both species. In Western blots of infected midguts and salivary glands the antibodies recognized two peptides in the salivary glands but up to ten peptides in midgut extracts. The larger number of peptides recognized in midgut preparations might indicate breakdown products during the escape of the sporozoites from the oocyst and their migration on the midgut in the mosquito vector. The data indicate a possible involvement of the CS protein in an active migration process of the sporozoites in the mosquito vector.

Aedes↗
PubMed1995

Properties of the histones and functional aspects of the soluble chromatin of epimastigote Trypanosoma cruzi.

The amino acid composition of all histones of Trypanosoma cruzi was analyzed, and the terminology of the histones of higher eukaryotes adopted. One chromatin associated protein, previously considered to be a variant of histone H1, could not be clearly identified, and shows features of core histones as well as of histone H1. An improved method for the isolation of intact nuclei and the production of soluble chromatin in T. cruzi was established. The chromatin of T. cruzi is relatively instable and histone H1 is easily lost during experimental manipulations. Histone H1 dissociates completely at a relatively low NaCl concentration of 380 mM, leading to an open nucleosome filament which does not condense. The influence of histone H1 of T. cruzi and of rat liver on the compaction pattern of the chromatin was investigated by homologous and heterologous reconstitution experiments, and analysed by electron microscopy. It could be shown that histone H1 of T. cruzi induces nucleosome filaments of T. cruzi as well as those of rat liver to condense. The same is true for histone H1 of rats. It can be concluded that T. cruzi has a functional histone H1.

Amino Acids↗
PubMed1995

CD8+ T-cell protective immunity induced by immunization with Plasmodium berghei CS protein-derived synthetic peptides: evidence that localization of peptide-specific CTLs is crucial for protection against malaria.

Immunization of BALB/c mice (H-2d) with a mixture of major histocompatibility complex (MHC) class I- and MHC class II-restricted synthetic peptides emulsified in incomplete Freund's adjuvant (IFA) induced a high level of specific cytotoxic T lymphocyte (CTL) activity. Peptides 249-260 or 252-260, derived from the circumsporozoite protein of Plasmodium berghei and representing a H-2Kd-restricted CTL epitope, were injected twice subcutaneously or intraperitoneally in BALB/c mice in combination with the tetanus toxin-derived universal T-helper peptide P30 in IFA. No protection was observed after exposure of immunized mice to infected mosquitoes. In contrast, when peptide 252-260-specific CTLs were expanded in vitro and adoptively transferred into naive recipient, mice were partially protected (64%) against a subsequent sporozoite challenge. Furthermore, direct transfer of lymph nodes or spleen cells from mice immunized with the peptide PbCS 252-260 also conferred protection to recipient mice. This protection was long-lasting and similar to that obtained with irradiated sporozoites.

Amino Acid Sequence↗
PubMed1995

Trypanosoma brucei brucei and high-density lipoproteins: old and new thoughts on the identity and mechanism of the trypanocidal factor in human serum.

Nature has provided humans with a surprising means of protection against the African trypanosome Trypanosoma brucei brucei There is consensus, in that this singular trypanocidal factor is serum high-density lipoproteins (HDL). which the trypanosomes engulf through a physiological, receptor-mediated pathway for delivery to acidic intracellular vesicles. There is also controversy, however, in that the active particles and their essential cytotoxic elements are disputed, in part reflecting the ill-defined mechanism by which the parasites are finally killed. Here Patrick Lorenz, Bruno Betschart and Jim Owen discuss the possibilities for resolving these discrepancies and speculate on the prospects of exploiting this unexpected property of human HDL for protecting livestock.

Journal Article↗
PubMed1995

Partial amino acid sequence and functional aspects of histone H1 proteins in Trypanosoma brucei brucei.

Trypanosoma brucei brucei, a protozoan parasite of wild and domestic animals in Africa, is related to the pathogenic agent of human sleeping sickness. Four H1 histone proteins were isolated from nuclei of procyclic culture forms and cleaved with proteases. Amino acid sequence analysis of purified fragments indicated the presence of variants which displayed sequence identities as compared to the C-terminal domain of human H1. Substitutions of amino acids and posttranslational modifications of the histones in T b brucei H1 may influence protein conformation and histone-histone as well as histone-DNA interactions in the chromatin of the parasite. Digestion of soluble chromatin with immobilized trypsin at low and high ionic strengths indicated an internal localization of H1 in the condensed chromatin. The influence of histone H1 of T b brucei on the compaction pattern of the chromatin was investigated by dissociation and reconstitution experiments. Electron microscopy revealed that trypanosome H1 was able to induce condensation of the chromatin of the parasite and of rat liver into dense tangles. After dephosphorylation of H1, 30 nm fibers were induced in rat liver chromatin, while the resulting fibers were distinctly thinner in T b brucei. It can be concluded that the absence of 30 nm fibers in T b brucei chromatin cannot be explained by the divergent variants and posttranslational phosphorylations of H1 only but rather by the influence of both, the divergent core histones, previously described, and H1 properties.

Amino Acid Sequence↗
PubMed1995

The antimalarial drug halofantrine is bound mainly to low and high density lipoproteins in human serum.

1. The major serum proteins which bind halofantrine were identified by size exclusion chromatography. In addition, the binding affinity of halofantrine to human erythrocytes and serum proteins was measured by an erythrocyte partitioning technique. The influence of serum-drug binding on the distribution of halofantrine in whole blood was estimated by simulating several disease-related changes in the levels of the most important binding proteins. 2. The chromatographic resolution of serum preincubated with halofantrine allowed a quantitative analysis of binding to low density lipoproteins, high density lipoproteins, alpha 1-acid glycoprotein and albumin using the erythrocyte partitioning technique. Very low density lipoproteins did not bind halofantrine to a significant extent. 3. In whole blood halofantrine is bound to serum proteins (83%) and to erythrocytes (17%). Low density lipoproteins (affinity constant nKP = 44.4 l g-1) and high density lipoproteins (nKP = 14.4 l g-1) were the most important binding proteins in serum. alpha 1-acid glycoprotein (nKP = 4.39 l g-1) and albumin (nKP = 0.27 l g-1) had relatively low binding affinities. 4. The concentration of serum proteins influences both the fraction of unbound drug and the fraction of drug associated with the erythrocytes. Changes in serum protein concentrations often encountered in malaria are likely to increase both the unbound fraction and the fraction bound to the erythrocytes.

Animals↗
PubMed1994

Characterization of the histones of Trypanosoma brucei brucei bloodstream forms.

Five groups of histones were shown in Trypanosoma brucei brucei, displaying qualitative and quantitative differences between two stages of the parasite's life-cycle. The influence of the histones of T. b. brucei bloodstream forms on the compaction pattern of the chromatin was investigated and their extractability in diluted acids and their amino acid composition were analysed. While nonhistone proteins barely influenced the formation of higher-order chromatin structures, the histone H1-like proteins were essential for the regular spacing of the nucleosomes and the salt-dependent condensation of the nucleosome filament. Differences were seen in the amino-acid composition of histones of bloodstream forms as compared to procyclic culture forms and higher eukaryotes which may explain the disparities seen in the condensation of the chromatin between the two stages of the life cycle as well as the lack of a salt-dependent condensation into a 30 nm fiber. They point to an alternative method of organizing and processing the genetic information in the nucleus of the trypanosome as compared to higher eukaryotes, the possible hosts of the parasite.

Amino Acids↗