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PubMed2002

Sulfadoxine-pyrimethamine monotherapy in Tanzanian children gives rapid parasite clearance but slow fever clearance that is improved by chloroquine in combination therapy.

Following widespread chloroquine (CQ) resistance, sulfadoxine plus pyrimethamine (SP) is now the first line antimalarial drug in a number of African countries including Tanzania. Unlike CQ, SP has no antipyretic effects, a feature that might delay fever clearance, and by acting on late stage parasites, SP could theoretical be slow in parasite clearance. We therefore assessed the antipyretic effects of CQ in therapeutic combination with SP, and the speed of parasite clearance by SP in an open-labelled, randomized trial of CQ alone (n=39), SP alone (n=39), SP plus CQ (n=37) and SP plus paracetamol (PCM) (n=38) in children with uncomplicated malaria. Over 72 h, there were eight (20.5%) treatment failures in the CQ group but none in the other groups. Although not significant (P > 0.1), irrespective of resistance CQ alone had a shorter median survival time to fever clearance than SP alone (54 vs. 60 h). SP plus CQ had a highly significantly shorter median survival time to fever clearance than SP alone (48 vs. 60 h) (P < 0.001). Although borderline (P=0.038), the median survival time to parasite clearance was significantly longer in SP plus PCM (72 h) than SP alone (48 h). Irrespective of resistance, CQ alone had a median survival time to parasite clearance equal to that of SP alone (48 h). Parasite clearance by SP was rapid and at the end of 72 h, most (77.3%, 95% confidence interval: 69.6, 85.0) of the children on SP (as a group) had become aparasitaemic. The findings rule out concerns on possible delayed parasitological and clinical responses to SP that could result from its action on late stage parasites. Despite its diminishing antimalarial activity, CQ has beneficial in vivo antipyretic effects in therapeutic combination with SP.

Acetaminophen↗
PubMed2003

Multiple parasites are driving major histocompatibility complex polymorphism in the wild.

Parasite mediated selection may result in arms races between host defence and parasite virulence. In particular, simultaneous infections from multiple parasite species should cause diversification (i.e. balancing selection) in resistance genes both at the population and the individual level. Here, we tested these ideas in highly polymorphic major histocompatibility complex (MHC) genes from three-spined sticklebacks (Gasterosteus aculeatus L.). In eight natural populations, parasite diversity (15 different species), and MHC class IIB diversity varied strongly between habitat types (lakes vs. rivers vs. estuaries) with lowest values in rivers. Partial correlation analysis revealed an influence of parasite diversity on MHC class IIB variation whereas general genetic diversity assessed at seven microsatellite loci was not significantly correlated with parasite diversity. Within individual fish, intermediate, rather than maximal allele numbers were associated with minimal parasite load, supporting theoretical models of self-reactive T-cell elimination. The optimal individual diversity matched those values female fish try to achieve in their offspring by mate choice. We thus present correlative evidence supporting the 'allele counting' strategy for optimizing the immunocompetence in stickleback offspring.

Animals↗
PubMed2002

Abattoir condemnation due to parasitic infections and its economic implications in the region of Trikala, Greece.

The prevalence of parasitic infections responsible for the condemnation of carcasses and viscera during meat inspection, and their economic implication, was estimated in a year long abattoir survey of 10 277 slaughtered farm animals in the region of Trikala, Greece. The organs examined for the presence of parasitic lesions during meat inspection were: liver and lungs of all animals, rumen of cattle, small intestine of lambs and kids, and muscles of cattle and swine. The parasitic lesions observed in the lungs of cattle, sheep and goats were caused only by hydatid cysts. No hydatid cysts were observed in the lungs of swine. The parasitic lesions observed in the liver of cattle, sheep and goats were as a result of hydatid cysts and flukes of Fasciola hepatica and Dicrocoelium dendriticum, while those of swine were due to milk spots only. Moniezia sp. proglottids were found in the small intestine of lambs only. The prevalence of parasites responsible for the condemnation of marketable organs was low (0.26%). Parasites were responsible for 22% of the total of condemned organs, and their annual cost was 99, 00 GDR (approximately 292 Euros). The parasites most contributing to marketable organ condemnation were hydatid cysts (26%) and D. dendriticum flukes (26%).

Abattoirs↗
PubMed2000

Isolation and characterization of a major allergen from the fish parasite Anisakis simplex.

BACKGROUND: Ingestion of raw or undercooked fish can lead to infection of human subjects by the fish parasite Anisakis simplex, a disease known as anisakiasis or anisakidosis. Patients sensitized to this fish parasite show high levels of total and specific IgE. Cross-reactions seem to explain the fact that specific IgE antibodies are also found in a high number of normal subjects, as reported in other parasitoses. OBJECTIVE: We sought to purify and characterize a major IgE-binding protein from the parasite. METHODS: A protein was purified from the crude parasite extract by means of ethanol precipitation and reversed-phase HPLC. Its clinical relevance was tested on 20 parasite-positive sera by using IgE and IgG4 immunoblotting. A monospecific human serum was used to study its localization in the parasite body. RESULTS: A 24-kd protein was purified, to which only 45% of the sera had specific IgG4, but 85% of sera had specific IgE. The protein was present only in the excretory gland, as shown by immunohistochemistry. N-terminal amino acid sequence (17 residues) showed no homology to previously described proteins. CONCLUSION: A simplex contains a potent allergen in the excretory gland. This major parasite allergen, named Ani s 1, could have important clinical relevance, as shown by the high number of positive sera in the specific IgE immunoblotting.

Allergens↗
PubMed2005

Murine malaria parasite sequestration: CD36 is the major receptor, but cerebral pathology is unlinked to sequestration.

Sequestration of malaria-parasite-infected erythrocytes in the microvasculature of organs is thought to be a significant cause of pathology. Cerebral malaria (CM) is a major complication of Plasmodium falciparum infections, and PfEMP1-mediated sequestration of infected red blood cells has been considered to be the major feature leading to CM-related pathology. We report a system for the real-time in vivo imaging of sequestration using transgenic luciferase-expressing parasites of the rodent malaria parasite Plasmodium berghei. These studies revealed that: (i) as expected, lung tissue is a major site, but, unexpectedly, adipose tissue contributes significantly to sequestration, and (ii) the class II scavenger-receptor CD36 to which PfEMP1 can bind is also the major receptor for P. berghei sequestration, indicating a role for alternative parasite ligands, because orthologues of PfEMP1 are absent from rodent malaria parasites, and, importantly, (iii) cerebral complications still develop in the absence of CD36-mediated sequestration, dissociating parasite sequestration from CM-associated pathology. Real-time in vivo imaging of parasitic processes may be used to evaluate the molecular basis of pathology and develop strategies to prevent pathology.

Adipose Tissue↗
PubMed1983

Isolation and characterization of the plasma membrane of human erythrocytes infected with the malarial parasite Plasmodium falciparum.

Human erythrocytes infected with the malarial parasite Plasmodium falciparum were labeled metabolically with a mixture of 15 radioactive amino acids. When synchronously growing parasites were at the schizont stage of development infected cells were concentrated and purified by using a Percoll-Hypaque gradient. The plasma membrane of the infected erythrocyte, isolated by binding cells to a solid support (Affi-Gel 731, Bio-Rad), was less than 1% contaminated with parasite membranes. Erythrocyte membrane proteins were analyzed by polyacrylamide gel electrophoresis and autoradiography. Despite the high sensitivity of the procedure, there was no evidence for the insertion of parasite proteins into the infected host cell membrane. One possible exception is a Mr 230,000 parasite protein present maximally as 9,000 copies per infected erythrocyte membrane. Moreover, no differences in the membrane proteins were observed between a highly knobby clone and a knobless clone of the same strain of P. falciparum. These findings appear to rule out the presence of parasite protein(s) playing a structural role in the formation of knobs on the erythrocyte surface and question whether the antigenic determinants on the P. falciparum-infected erythrocyte are of parasite origin or whether such antigens represent newly exposed or chemically modified erythrocyte determinants.

Erythrocyte Membrane↗
PubMed1995

Parasite abundance and diversity in mammals: correlates with host ecology.

Fecally dispersed parasites of 12 wild mammal species in Mudumalai Sanctuary, southern India, were studied. Fecal propagule densities and parasite diversity measures were correlated with host ecological variables. Host species with higher predatory pressure had lower parasite loads and parasite diversity. Host body weight, home range, population density, gregariousness, and diet did not show predicted effects on parasite loads. Measures of alpha diversity were positively correlated with parasite abundance and were negatively correlated with beta diversity. Based on these data, hypotheses regarding determinants of parasite community are discussed.

Animals↗
PubMed1995

Selective labeling of intracellular parasite proteins by using ricin.

Studies focused on the synthesis by intracellular parasites of developmentally regulated proteins have been limited due to the lack of a simple method for selectively labeling proteins produced by the parasite. A method has now been developed in which ricin is employed to selectively inhibit host-cell protein synthesis. Ricin is a heterodimer composed of two subunits, a lectin and a glycosidase, and it binds to terminal galactose residues on the cell surface via the lectin. Following endocytosis of the intact molecule, a disulfide bond linking the two subunits is cleaved, and only the glycosidase subunit enters the cytoplasm, where it inhibits cytoplasmic protein synthesis by catalyzing the cleavage of the 28S rRNA. Due to the loss of the receptor-binding lectin subunit, ricin cannot permeate host-cell mitochondria or intracellular parasites, and, therefore, protein synthesis within these compartments continues uninterrupted. This system has been used to selectively label parasite proteins from Eimeria tenella and Toxoplasma gondii by using the avian cell line DU-24. In these cells, mitochondrial protein synthesis was inhibited by using chloramphenicol. The use of the avian rho0 cell line DUS-3 provided an additional advantage, because these cells lack mitochondrial DNA. Therefore, those proteins radiolabeled with [35S]methionine/cysteine in ricin-treated, parasite-infected rho0 cells are exclusively those of the intracellular parasite. This technique should be applicable for studying protein synthesis by other intracellular parasites.

Animals↗
PubMed1997

Parasite-mediated nuclear factor kappaB regulation in lymphoproliferation caused by Theileria parva infection.

Infection of cattle with the protozoan Theileria parva results in uncontrolled T lymphocyte proliferation resulting in lesions resembling multicentric lymphoma. Parasitized cells exhibit autocrine growth characterized by persistent translocation of the transcriptional regulatory factor nuclear factor kappaB (NFkappaB) to the nucleus and consequent enhanced expression of interleukin 2 and the interleukin 2 receptor. How T. parva induces persistent NFkappaB activation, required for T cell activation and proliferation, is unknown. We hypothesized that the parasite induces degradation of the IkappaB molecules which normally sequester NFkappaB in the cytoplasm and that continuous degradation requires viable parasites. Using T. parva-infected T cells, we showed that the parasite mediates continuous phosphorylation and proteolysis of IkappaBalpha. However, IkappaBalpha reaccumulated to high levels in parasitized cells, which indicated that T. parva did not alter the normal NFkappaB-mediated positive feedback loop which restores cytoplasmic IkappaBalpha. In contrast, T. parva mediated continuous degradation of IkappaBbeta resulting in persistently low cytoplasmic IkappaBbeta levels. Normal IkappaBbeta levels were only restored following T. parva killing, indicating that viable parasites are required for IkappaBbeta degradation. Treatment of T. parva-infected cells with pyrrolidine dithiocarbamate, a metal chelator, blocked both IkappaB degradation and consequent enhanced expression of NFkappaB dependent genes. However treatment using the antioxidant N-acetylcysteine had no effect on either IkappaB levels or NFkappaB activation, indicating that the parasite subverts the normal IkappaB regulatory pathway downstream of the requirement for reactive oxygen intermediates. Identification of the critical points regulated by T. parva may provide new approaches for disease control as well as increase our understanding of normal T cell function.

Animals↗
PubMed1998

Deletion of Plasmodium berghei-specific CD4+ T cells adoptively transferred into recipient mice after challenge with homologous parasite.

The immune response to malaria parasites includes T cell responses that reduce parasites by effector T cell responses and by providing help for antibody responses. Some parasites are more sensitive to antibody and others are more sensitive to cell-mediated immunity. We demonstrate that cultured CD4(+) T cells that produce interferon gamma and interleukin 2, but not interleukin 4, in response to stimulation with the rodent parasite Plasmodium berghei can reduce but not eliminate parasites in vivo after adoptive transfer. Although cells can persist in vivo for up to 9 months in uninfected mice, infection results in elimination of up to 99% of specific T cells in different tissues, as judged by tracking T cells labeled with the fluorescent dye 5-(and -6)-carboxyfluorescein diacetate succinimidyl ester. T cells specific for ovalbumin are unaffected. In vivo activation and division of transferred T cells per se are not responsible for deletion because T cells positive for 5-(and -6)-carboxyfluorescein diacetate succinimidyl ester divide up to six times within 7 days in uninfected mice and are not deleted. Understanding the factors responsible for parasite-mediated specific deletion of T cells would enhance our knowledge of parasite immunity.

Adoptive Transfer↗
PubMed1999

The intracellular parasite Theileria parva protects infected T cells from apoptosis.

Parasites have evolved a plethora of strategies to ensure their survival. The intracellular parasite Theileria parva secures its propagation and spreads through the infected animal by infecting and transforming T cells, inducing their continuous proliferation and rendering them metastatic. In previous work, we have shown that the parasite induces constitutive activation of the transcription factor NF-kappaB, by inducing the constitutive degradation of its cytoplasmic inhibitors. The biological significance of NF-kappaB activation in T. parva-infected cells, however, has not yet been defined. Cells that have been transformed by viruses or oncogenes can persist only if they manage to avoid destruction by the apoptotic mechanisms that are activated on transformation and that contribute to maintain cellular homeostasis. We now demonstrate that parasite-induced NF-kappaB activation plays a crucial role in the survival of T. parva-transformed T cells by conveying protection against an apoptotic signal that accompanies parasite-mediated transformation. Consequently, inhibition of NF-kappaB nuclear translocation and the expression of dominant negative mutant forms of components of the NF-kappaB activation pathway, such as IkappaBalpha or p65, prompt rapid apoptosis of T. parva-transformed T cells. Our findings offer important insights into parasite survival strategies and demonstrate that parasite-induced constitutive NF-kappaB activation is an essential step in maintaining the transformed phenotype of the infected cells.

Animals↗
PubMed1999

Transient expression of DNA and RNA in parasitic helminths by using particle bombardment.

Parasitic helminths (worms belonging to several metazoan phyla) cause considerable morbidity and mortality in humans. They are an important veterinary problem, and they result in significant economic losses in animal grazing and agriculture. Experimental studies on parasitic helminths have been limited by a lack of parasite cell lines and methods for molecular genetic analyses. We evaluated particle bombardment (biolistics) as a strategy to introduce and express nucleic acids in these multicellular parasites. By using embryos of the parasitic nematode Ascaris as a model, we developed methods to introduce and express both DNA and RNA during several stages of Ascaris embryogenesis. Biolistic transfection will facilitate experimental strategies in Ascaris embryos complementing other biochemical tools available (e.g., in vitro whole-cell embryo extracts for transcription, RNA processing, and translation). Transfection experiments with adult schistosomes further suggest that the biolistic strategy should be applicable to a variety of other parasitic helminths. The development of these methods provides molecular genetic tools to study gene expression and the biology of a variety of types and developmental stages of important helminth parasites.

Animals↗
PubMed1998

Transport and metabolism of the essential vitamin pantothenic acid in human erythrocytes infected with the malaria parasite Plasmodium falciparum.

The growth of the human malaria parasite, Plasmodium falciparum, within its host erythrocyte is reliant on the uptake of a number of essential nutrients from the extracellular medium. One of these is pantothenic acid, a water-soluble vitamin that is a precursor of coenzyme A. In this study we show that normal uninfected erythrocytes are impermeable to pantothenate but that the vitamin is taken up rapidly into malaria-infected cells via a transport pathway that has the characteristics (furosemide sensitivity, nonsaturability) of previously characterized, broad specificity permeation pathways induced by the intracellular parasite in the host cell membrane. The transport of pantothenate therefore constitutes a critical physiological role for these pathways. Inside the parasitized cell pantothenate undergoes phosphorylation, the first step in its conversion to coenzyme A. Parasites within saponin-permeabilized erythrocytes were shown to take up and phosphorylate pantothenate, consistent with the intracellular parasite having both a pantothenate transporter and a pantothenate kinase. Comparisons of the rate of phosphorylation of pantothenate by lysates prepared from uninfected and infected erythrocytes revealed that the pantothenate kinase activity of the P. falciparum trophozoite is some 10-fold higher than that of its host cell and that most, if not all, of the phosphorylation of pantothenate within the malaria-infected cell occurs within the intracellular parasite. These results contrast with those of previous studies in which it was proposed that the avian malaria parasite Plasmodium lophurae lacks pantothenate kinase (as well as the other enzymes for the synthesis of coenzyme A) and is reliant upon the uptake of preformed coenzyme A from the host cell cytosol.

Animals↗
PubMed2001

A homologue of N-ethylmaleimide-sensitive factor in the malaria parasite Plasmodium falciparum is exported and localized in vesicular structures in the cytoplasm of infected erythrocytes in the brefeldin A-sensitive pathway.

N-Ethylmaleimide-sensitive factor (NSF) and its homologues play a central role in vesicular trafficking in eukaryotic cells. We have identified a NSF homologue in Plasmodium falciparum (PfNSF). The reported PfNSF gene sequence (GenBank accession number CAB10575) indicated that PfNSF comprises 783 amino acids with a calculated molecular weight of 89,133. The overall identities of its gene and amino acid sequences with those of rat NSF are 50.9 and 48.8%, respectively. Reverse transcription-polymerase chain reaction analysis and Northern blotting with total P. falciparum RNA indicated expression of the PfNSF gene. Polyclonal antibodies against a conserved region of NSF specifically recognized an 89-kDa polypeptide in the parasite cells. After homogenization of the parasite cells, approximately 90% of an 89-kDa polypeptide is associated with particulate fraction, suggesting membrane-bound nature of PfNSF. PfNSF was present within both the parasite cells and the vesicular structure outside of the parasite cells. The export of PfNSF outside of the parasite cells appears to occur at the early trophozoite stage and to terminate at the merozoite stage. The export of PfNSF is inhibited by brefeldin A, with 9 microM causing 50% inhibition. Immunoelectromicroscopy indicated that intracellular PfNSF was associated with organelles such as food vacuoles and that extracellular PfNSF was associated with vesicular structures in the erythrocyte cytoplasm. These results indicate that PfNSF expressed in the malaria parasite is exported to the extracellular space and then localized in intraerythrocytic vesicles in a brefeldin A-sensitive manner. It is suggested that a vesicular transport mechanism is involved in protein export targeted to erythrocyte membranes during intraerythrocytic development of the malaria parasite.

Amino Acid Sequence↗
PubMed2003

The digestive food vacuole of the malaria parasite is a dynamic intracellular Ca2+ store.

The acidic food vacuole of Plasmodium falciparum has been the subject of intense scientific investigation in the 40 years since its role in the digestion of host hemoglobin was first suggested. This proposed role has important implications for the complex host-parasite inter-relationship and also for the mode of action of several of the most effective antimalarial drugs. In addition, adaptive changes in the physiology of this organelle are implicated in drug resistance. Here we show that in addition to these functions, the digestive food vacuole of the malaria parasite is a dynamic internal store for free Ca2+, a role hitherto unsuspected. With the aid of live-cell laser scanning confocal imaging, spatiotemporal studies revealed that maintenance of elevated free Ca2+ in the digestive food vacuole (relative to cytosolic levels) is achieved by a thapsigargin (and cyclopiazonic acid)-sensitive Ca2+-pump in cooperation with a H+-dependent Ca2+ transporter. Redistribution of free cytosolic and vacuolar Ca2+ during parasite growth also suggests that vacuolar Ca2+ plays an essential role in parasite morphogenesis. These data imply that the digestive food vacuole of the malaria parasite is functionally akin to the vacuole of plants (tonoplast) and the small electron-dense granules of some parasites (acidocalcisomes) whereby H+-coupled Ca2+ transport is involved in ion transport, Ca2+ homeostasis, and signal transduction. These findings have significant implications for parasite development, antimalarial drug action, and mechanisms of drug resistance.

Animals↗
PubMed2004

Selection of cysteine protease inhibitor-resistant malaria parasites is accompanied by amplification of falcipain genes and alteration in inhibitor transport.

Cysteine protease inhibitors are being studied as possible new antimalarial agents. To evaluate the potential for resistance to these compounds, we subjected chloroquine-resistant (W2 strain) Plasmodium falciparum to increasing concentrations of a vinyl sulfone cysteine protease inhibitor. After incubation with 1-200 nm morpholine urea-leucine-homophenylalanine-phenyl vinyl sulfone over approximately 8 months, highly resistant parasites ( approximately 100-fold increases in IC(50)) were selected. The vinyl sulfone-resistant parasites were also resistant to related peptidyl inhibitors, but had only modest ( approximately 2-fold) decreases in sensitivity to other cysteine protease inhibitors. Compared with the parental strain, resistant parasites showed no changes in multiplication rates, but elevations in cysteine protease activity, falcipain-2 and falcipain-3 copy numbers, transcription of falcipain genes, and levels of these target proteases in trophozoites. Resistant parasites grown in the absence of the vinyl sulfone for 12 weeks showed partial reversion, with increased inhibitor sensitivity and apparent decreases in copy numbers of falcipain-2 and falcipain-3. The sequences of falcipain-1, falcipain-2, and falcipain-3 were identical in sensitive and resistant parasites. The accumulation of a vinyl sulfone inhibitor was decreased approximately 9-fold in resistant parasites. In summary, parasites resistant to a cysteine protease inhibitor were selected, although the acquisition of high level resistance required extended exposure to the inhibitor and this resistance was somewhat unstable. Resistance was specific for the type of protease inhibitor used for the selection and appeared to be mediated both by alterations in inhibitor transport and by a previously unidentified mechanism in P. falciparum, the amplification of genes encoding targets of enzyme inhibitors.

Animals↗
PubMed2003

Proteome mapping of the protozoan parasite Leishmania and application to the study of drug targets and resistance mechanisms.

Leishmania is a protozoan parasite responsible for significant morbidity and mortality worldwide. Few parasites have been subjected to proteomic analysis to date, but a genome sequencing project for Leishmania major is currently underway, making these studies possible. Here we present a high resolution proteome for L. major comprising almost 3700 spots, making it the most complete two-dimensional gel representation of a parasite proteome generated to date. We have identified a number of landmark proteins by mass spectrometry and show that several of these are valid for the related species Leishmania donovani infantum. We have also observed several forms and fragments of alpha- and beta-tubulins and show that the number and amount of these fragments increase with the age of the parasite culture. Trypanothione reductase (TRYR), which replaces glutathione reductase in trypanosomatid parasites, is an essential protein specific to these parasites and as such is under considerable scrutiny as a drug target. Two-dimensional gel analysis of a L. major strain overexpressing TRYR revealed increased amounts of five spots, all at the predicted molecular weight for TRYR and differing by 0.08 pH units in pI. Mass spectrometry identified four of these as TRYR, leading to the novel suggestion that it could be post-translationally modified. Finally quantitative comparative analysis of a methotrexate-resistant mutant of L. major generated in vitro found that a known primary resistance mediator, the pteridine reductase PTR1, was overexpressed. This constitutes the first proteomic analysis of drug resistance in a parasite and also the clearest identification of a primary drug resistance mechanism using this approach. Together these results provide a framework for further proteomic studies of Leishmania species and demonstrate that these tools are valuable for the essential study of potential drug targets and drug resistance mechanisms.

Animals↗
PubMed1985

Human erythrocytes adhering to schistosomula of Schistosoma mansoni lyse and fail to transfer membrane components to the parasite.

We studied the adherence of human erythrocytes to larvae of the intravascular parasite Schistosoma mansoni by transmission microscopy, freeze fracture, and fluorescence techniques. In addition, we used the adherent cells to investigate the problem of host antigen acquisition. Schistosomula were cultured for from 24 to 48 h after transformation in order to clear the remnants of the cercarial glycocalyx. In some cases, the worms were preincubated with wheat germ agglutinin to promote adherence of the erythrocytes. The results were similar with and without the lectin except that more cells attached to the lectin-coated parasites. Erythrocytes adhered within a few hours and, unlike neutrophils, did not fuse with the parasite. A layer of 10-20-nm electron dense material separated the outer leaflets of the tegumental and plasma membranes. In addition, many deformed and lysed cells were seen on the parasite surface. The ability of the worm to acquire erythrocyte membrane constituents was tested with carbocyanine dyes, fluorescein covalently conjugated to glycophorin, monoclonal antibodies against B and H blood group glycolipids, and rabbit alpha-human erythrocyte IgG. In summary, glycophorin, erythrocyte proteins, and glycolipids were not transferred to the parasite membrane within 48 h. Carbocyanine dyes were rapidly transferred to the parasite with or without lectin preincubation. Thus, the dye in the worm membrane came from both adherent and nonadherent cells. These studies suggest that, in the absence of membrane fusion, the parasite may acquire some lipid molecules similar in structure to host membrane glycolipids by simple transfer through the medium but that B and H glycolipids and erythrocyte membrane proteins are not transferred from adhering cells to the worm.

ABO Blood-Group System↗