Glycocalyx of bodies versus tails of Schistosoma mansoni cercariae. Lectin-binding, size, charge, and electron microscopic characterization

Schiff bases complexed with iron and their relation with the life cycle and infection by Schistosoma mansoni

Introduction

The trematode Schistosoma mansoni causes schistosomiasis, and this parasite's life cycle depends on the mollusk Biomphalaria glabrata. The most effective treatment for infected people is administering a single dose of Praziquantel. However, there are naturally resistant to treatment. This work has developed, considering this parasite's complex life cycle.

Methods

The synthetics compound were evaluated: i) during the infection of B. glabrata, ii) during the infection of BALB/c mice, and iii) during the treatment of mice infected with S. mansoni.

Results and Discussion

For the first objective, snails infected with miracidia treated with compounds C1 and C3 at concentrations of 25% IC50 and 50% IC50, after 80 days of infection, released fewer cercariae than the infected group without treatment. For the second objective, compounds C1 and C3 did not show significant results in the infected group without treatment. For the third objective, the mice treated with C3 and C1 reduced the global and differential cell count. The results suggest that although the evaluated compounds do not present schistosomicidal properties when placed in cercariae suspension, they can stimulate an immune reaction in snails and decrease mice's inflammatory response. In general, we can conclude that compound C1 and C3 has an anti-schistosomicidal effect both in the larval phase (miracidia) and in the adult form of the parasite.

Toxic, cytotoxic and genotoxic effect of saline extract and fraction of Parkia pendula seeds in the developmental stages of Biomphalaria glabrata (Say 1818 - intermediate host) and cercaricide activity against the infectious agent of schistosomiasis

This study describes for the first time the effect of saline extract and Parkia pendula seed fraction on Biomphalaria glabrata adult embryos and molluscs well as the reproductive parameters (fecundity and fertility) and survival, in addition to cytotoxicity and genotoxicity through the profile of blood cells after exposure to sublethal concentrations. Furthermore, we analyzed the action of both preparations against the cercariae of Schistosoma mansoni and their environmental safety using the bioindicator Artemia salina. The saline extract and fraction showed toxic effects for embryos (CL₉₀ of 464.25, 479.62, 731.28, 643.28, 408.43 and 250.94, 318.03, 406.12, 635.64, 1.145 mg/mL, for blastula, gastrula, trocophore, veliger and hippo stage respectively), adult snails after 24 h of exposure (CL₉₀ of 9.50 and 10.92 mg/mL, respectively) with increased mortality after 7 days of observation and significant decrease (p <0.05; p < 0.01 and p < 0.001) in egg mass deposition. At sublethal concentrations, an increase in quantitative and morphological changes in hemocytes was observed, and in the genotoxicity/comet assay analysis, varying degrees of nuclear damage were detected. In addition, the saline extract showed changes in the motility of the cercariae, while the fraction howed toxicity from a concentration of 1.0 mg/mL. The saline extract showed toxicity to A. salina at the highest concentrations (3.0, 4.0 and 5.0 mg/mL), while the fraction did not show ecotoxicity. Thus, the saline extract and fraction was promising in combating schistosomiasis by eliminating the intermediate host and causing alterations and/or mortality to the infectious agent.

Deleterious Consequences of UDP-Galactopyranose Mutase Inhibition for Nematodes

Parasitic nematodes pose a serious threat to agriculture, livestock, and human health. Increasing resistance to antiparasitic agents underscores the need to replenish our anthelmintic arsenal. The nonpathogenic Caenorhabditis elegans, which serves as an effective model of parasitic helminths, has been used to search for new anthelmintic leads. We previously reported small-molecule inhibitors of the essential C. elegans protein UDP-galactopyranose mutase (UGM or Glf). This enzyme is required for the generation of galactofuranose (Galf)-containing glycans and is needed in nematodes for proper cuticle formation. Though our first-generation inhibitors were effective in vitro, they elicited no phenotypic effects. These findings are consistent with the known difficulty of targeting nematodes. C. elegans is recalcitrant to pharmacological modulation; typically, less than 0.02% of small molecules elicit a phenotypic effect, even at 40 μM. We postulated that the lack of activity of the UGM inhibitors was due to their carboxylic acid group, which can be exploited by nematodes for detoxification. We therefore tested whether replacement of the carboxylate with an N-acylsulfonamide surrogate would result in active compounds. UGM inhibitors with the carboxylate mimetic can phenocopy the deleterious consequences of UGM depletion in C. elegans. These findings support the use of UGM inhibitors as anthelmintic agents. They also outline a strategy to render small-molecule carboxylates more effective against nematodes.

Changes in surface glycosylation and glycocalyx shedding in Trichobilharzia regenti (Schistosomatidae) during the transformation of cercaria to schistosomulum

The invasive larvae (cercariae) of schistosomes penetrate the skin of their definitive hosts. During the invasion, they undergo dramatic ultrastructural and physiological transitions. These changes result in the development of the subsequent stage, schistosomulum, which migrates through host tissues in close contact with host's immune system. One of the striking changes in the transforming cercariae is the shedding of their thick tegumental glycocalyx, which represents an immunoattractive structure; therefore its removal helps cercariae to avoid immune attack. A set of commercial fluorescently labeled lectin probes, their saccharide inhibitors and monoclonal antibodies against the trisaccharide Lewis-X antigen (LeX, CD15) were used to characterize changes in the surface saccharide composition of the neuropathogenic avian schistosome Trichobilharzia regenti during the transformation of cercariae to schistosomula, both in vitro and in vivo. The effect of various lectins on glycocalyx shedding was evaluated microscopically. The involvement of peptidases and their inhibitors on the shedding of glycocalyx was investigated using T. regenti recombinant cathepsin B2 and a set of peptidase inhibitors. The surface glycocalyx of T. regenti cercariae was rich in fucose and mannose/glucose residues. After the transformation of cercariae in vitro or in vivo within their specific duck host, reduction and vanishing of these epitopes was observed, and galactose/N-acetylgalactosamine emerged. The presence of LeX was not observed on the cercariae, but the antigen was gradually expressed from the anterior part of the body in the developing schistosomula. Some lectins which bind to the cercarial surface also induced secretion from the acetabular penetration glands. Seven lectins induced the shedding of glycocalyx by cercariae, among which five bound strongly to cercarial surface; the effect could be blocked by saccharide inhibitors. Mannose-binding protein, part of the lectin pathway of the complement system, also bound to cercariae and schistosomula, but had little effect on glycocalyx shedding. Our study did not confirm the involvement of proteolysis in glycocalyx shedding.

The Tao survivorship of schistosomes: implications for schistosomiasis control

Schistosomiasis, caused by blood flukes of the genus Schistosoma, is a major public health problem which contributes substantially to the economic and financial burdens of many nations in the developing world. An array of survival strategies, such as the unique structure of the tegument which acts as a major host-parasite interface, immune modulation mechanisms, gene regulation, and apoptosis and self-renewal have been adopted by schistosome parasites over the course of long-term evolution with their mammalian definitive hosts. Recent generation of complete schistosome genomes together with numerous biological, immunological, high-throughput "-omics" and gene function studies have revealed the Tao or strategies that schistosomes employ not only to promote long-term survival, but also to ensure effective life cycle transmission. New scenarios for the future control of this important neglected tropical disease will present themselves as our understanding of these Tao increases.

New insights into the reaction of Schistosoma mansoni cercaria to the human complement system

Schistosomes are parasitic worms that have a complex life cycle. The larval stage cercaria, infectious to mammals, is described as highly susceptible to the complement system, largely due to the glycocalyx that covers the cercarial membrane. In an attempt to have a more complete understanding of cercaria reaction to the complement system, three different approaches were used. Live cercariae exposed to normal human serum (NHS) as source of complement factors were assessed for (i) membrane attack complex (MAC) deposition on the parasite surface, (ii) cercaria survival rate by Hoechst staining of parasite DNA, and (iii) transformation into schistosomula by detection of the glucose transporter protein 4 (SGTP4), a marker for new tegument formation. We found that 82-95% of cercariae directly exposed to NHS for 18 h were viable and retained their ability to shed the glycocalyx, suggesting minimal tegument damage. In contrast, inhibition of glycocalyx shedding using eserine caused significant MAC binding and parasite death. Culturing complement-exposed cercariae to measure long-term survival showed that more parasites died over time, reaching a survival rate of 18-31% by day 6 in culture. The reason for this slow death is unknown, but the surviving parasites were able to form a new tegument as shown by detection of SGTP4 on the parasite surface. Furthermore, we found that complement activation significantly damaged the acetabular gland ducts and lysed secretory vesicles released by transforming cercariae. These findings should contribute for future in vivo studies of the effects of the complement system in skin migrating cercariae.

In silico analysis of the fucosylation-associated genome of the human blood fluke Schistosoma mansoni: cloning and characterization of the fucosyltransferase multigene family

Fucosylated glycans of the parasitic flatworm Schistosoma mansoni play key roles in its development and immunobiology. In the present study we used a genome-wide homology-based bioinformatics approach to search for genes that contribute to fucosylated glycan expression in S. mansoni, specifically the α2-, α3-, and α6-fucosyltransferases (FucTs), which transfer L-fucose from a GDP-L-fucose donor to an oligosaccharide acceptor. We identified and in silico characterized several novel schistosome FucT homologs, including six α3-FucTs and six α6-FucTs, as well as two protein O-FucTs that catalyze the unrelated transfer of L-fucose to serine and threonine residues of epidermal growth factor- and thrombospondin-type repeats. No α2-FucTs were observed. Primary sequence analyses identified key conserved FucT motifs as well as characteristic transmembrane domains, consistent with their putative roles as fucosyltransferases. Most genes exhibit alternative splicing, with multiple transcript variants generated. A phylogenetic analysis demonstrated that schistosome α3- and α6-FucTs form monophyletic clades within their respective gene families, suggesting multiple gene duplications following the separation of the schistosome lineage from the main evolutionary tree. Quantitative decreases in steady-state transcript levels of some FucTs during early larval development suggest a possible mechanism for differential expression of fucosylated glycans in schistosomes. This study systematically identifies the complete repertoire of FucT homologs in S. mansoni and provides fundamental information regarding their genomic organization, genetic variation, developmental expression, and evolutionary history.

The Schistosoma mansoni tegumental-allergen-like (TAL) protein family: influence of developmental expression on human IgE responses

BACKGROUND

A human IgE response to Sm22.6 (a dominant IgE target in Schistosoma mansoni) is associated with the development of partial immunity. Located inside the tegument, the molecule belongs to a family of proteins from parasitic platyhelminths, the Tegument-Allergen-Like proteins (TALs). In addition to containing dynein-light-chain domains, these TALs also contain EF-hand domains similar to those found in numerous EF-hand allergens.

METHODOLOGY/PRINCIPAL FINDINGS

S. mansoni genome searches revealed 13 members (SmTAL1-13) within the species. Recent microarray data demonstrated they have a wide range of life-cycle transcriptional profiles. We expressed SmTAL1 (Sm22.6), SmTAL2, 3, 4, 5 and 13 as recombinant proteins and measured IgE and IgG4 in 200 infected males (7-60 years) from a schistosomiasis endemic region in Uganda. For SmTAL1 and 3 (transcribed in schistosomula through adult-worms and adult-worms, respectively) and SmTAL5 (transcribed in cercariae through adult-worms), detectable IgE responses were rare in 7-9 year olds, but increased with age. At all ages, IgE to SmTAL2 (expressed constitutively), was rare while anti-SmTAL2 IgG4 was common. Levels of IgE and IgG4 to SmTAL4 and 13 (transcribed predominantly in the cercariae/skin stage) were all low.

CONCLUSIONS

We have not measured SmTAL protein abundance or exposure in live parasites, but the antibody data suggests to us that, in endemic areas, there is priming and boosting of IgE to adult-worm SmTALs by occasional death of long-lived worms, desensitization to egg SmTALs through continuous exposure to dying eggs and low immunogenicity of larval SmTALs due to immunosuppression in the skin by the parasite. Of these, it is the gradual increase in IgE to the worm antigens that parallels age-dependent immunity seen in endemic areas.

Potential effects of Cramoll 1,4 lectin on murine Schistosomiasis mansoni

Cratylia mollis is a natural forage plant from the Northeast of Brazil. C. mollis seed lectin (Cramoll) containing molecular forms 1 and 4 (Cramoll 1,4) has shown anti-inflammatory and wound-healing activities. This work analyzed the effect of Cramoll 1,4 on experimental schistosomiasis in mice. Experimental groups (n=15/group) were composed of female albino Swiss mice, which were subcutaneously and caudally infected with Schistosoma mansoni (BH strain, 100 cercariae/mouse) and were treated with an intraperitoneal dose after infection as follows: (1) Cramoll 1,4 (50 mg kg(-1) single dose - after 40 days of infection), (2) Cramoll 1,4 (7 mg kg(-1) daily dose - for 7 days after infection) and control (untreated mice). Mice were sacrificed 8 weeks after infection and adult worms were recovered from the portal-hepatic system. Livers were fixed in 10% (v/v) formaldehyde/0.15M NaCl and tissue sections were processed for haematoxilin and Masson's trichrome stainings. Mice infected subcutaneously harboured no or very few worms and hence the effect of Cramoll 1,4 could not be assessed. Results (P≤0.05) were obtained with Cramoll 1,4 using the two treatments, with reduction of: egg excretion (79 and 80%), adult worm recovery (71 and 79%) and liver granulomas (40 and 73.5%) in relation to control. This study showed the potential anti-helminthic activity of Cramoll 1,4 when tested against Schistosomiasis mansoni infection in mice.

An atlas for Schistosoma mansoni organs and life-cycle stages using cell type-specific markers and confocal microscopy

Schistosomiasis (bilharzia) is a tropical disease caused by trematode parasites (Schistosoma) that affects hundreds of millions of people in the developing world. Currently only a single drug (praziquantel) is available to treat this disease, highlighting the importance of developing new techniques to study Schistosoma. While molecular advances, including RNA interference and the availability of complete genome sequences for two Schistosoma species, will help to revolutionize studies of these animals, an array of tools for visualizing the consequences of experimental perturbations on tissue integrity and development needs to be made widely available. To this end, we screened a battery of commercially available stains, antibodies and fluorescently labeled lectins, many of which have not been described previously for analyzing schistosomes, for their ability to label various cell and tissue types in the cercarial stage of S. mansoni. This analysis uncovered more than 20 new markers that label most cercarial tissues, including the tegument, the musculature, the protonephridia, the secretory system and the nervous system. Using these markers we present a high-resolution visual depiction of cercarial anatomy. Examining the effectiveness of a subset of these markers in S. mansoni adults and miracidia, we demonstrate the value of these tools for labeling tissues in a variety of life-cycle stages. The methodologies described here will facilitate functional analyses aimed at understanding fundamental biological processes in these parasites.

Schistosomes are parasitic flatworms that infect hundreds of millions of people worldwide. The development of genomic resources and recent application of functional genomic tools (e.g., global gene expression studies, inhibition of gene expression by RNA interference, and transgenesis) hold the promise of revolutionizing the study of schistosome biology. These advances necessitate the introduction of molecular markers for examining the consequences of manipulating schistosome genes. In this manuscript we report the use of several cell type-specific markers and confocal microscopy for visualizing various schistosome tissues in a variety of life-cycle stages. Our analysis provides an atlas of the major organ systems in three different life-cycle stages in these important parasites. The tools and methodologies reported here are widely available and can be readily adopted by researchers interested in more detailed studies of these organisms. We anticipate that these resources will be particularly useful for detailed phenotypic characterization following gene inhibition or over-expression studies.

Toxicity of cadmium and zinc mixtures to the decaudized cercarial life span ofDiplostomum spathaceum

The effects of cadmium and zinc mixtures at concentrations ranging from 0.1 to 10,000 μg l−1on the life-span of decaudized cercarial bodies (cercariae that have shed their tails) ofDiplostomum spathaceum(Trematoda: Diplostomatidae) was investigated. Cercariae were exposed to metal mixtures of equal and unequal concentrations, and a low-dose pre-treatment followed by a high-dose exposure mixtures. Metal mixtures demonstrated variable effects on decaudized cercariae either by increasing or reducing their life-span compared to single metal exposures dependent on concentration and the type of mixed metal treatment. Prolonged exposure to equal metal mixtures at low concentrations (0.1–100 μg l−1) resulted in a reduction in the life-span of decaudized cercariae at 0.1 and 100 μg l−1in those individuals decaudized during the initial 24 h exposure period compared with those decaudized during the final 24 h period of cercarial survival, whilst in controls there was no significant life-span change between the two time periods. Decaudized cercariae which were exposed to low concentrations (0.1–100 μg l−1) of equal metal mixtures were also evaluated for their role as an indicator of larval ‘fitness’ for migrating through the tissues of their target fish host for those individuals decaudized during the initial 24 h exposure period, and demonstrated only a limited change in their life-span compared to control and single metal exposures. The importance of metal mixtures in parasite establishment in the fish host is discussed.

Characterization of development-related genes for the cestode Bothriocephalus acheilognathi

Differential gene expression of mature and immature Bothriocephalus acheilognathi cestodes was analyzed using the suppression subtractive hybridization technique. Five mature-associated cDNAs were isolated and characterized. Virtual Northern blot and RT-PCR analyses confirmed that four of the five genes were upregulated in mature parasites. The sequence analysis revealed that one gene encoded the structural protein chorion precursor, and the three encoded functional proteins homologous to yolk ferritin, sodium/hydrogen exchanger and muscin-like protein. Another gene appeared to be specific to B. acheilognathi, encoding a putative metal-bound protein. Although results obtained in the present study are preliminary, the information about the five genes may provide clues for further investigation on the decline in parasite numbers during the maturation of B. acheilognathi.

Schistosoma mansoni and Schistosoma haematobium: identification and characterization of glycoconjugate antigens in the hemolymph of infected vector snails

Two carbohydrate epitopes were identified by monoclonal antibodies (KCS and E2) and characterized with respect to their immunoreactivity, monosaccharide structure, and location. Immunofluorescence demonstrated the presence of both epitopes on the surfaces of sporocysts, cercariae, and miracidia of Schistosoma mansoni, Schistosoma haematobium, and Schistosoma japonicum. However, spatial distribution and density of expression varied among species and developmental stages, and neither epitope was detectable on adult worm surfaces. Both glycans were found in the hemolymph of infected, but not uninfected, intermediate snail hosts. The presence of epitopes in hemolymph, as well as in schistosome eggs, is species-specific for KCS, recognizing only S. mansoni, and partly specific for E2, which reacted predominantly with S. haematobium. Immunoaffinity purification of target antigens for KCS and E2 from hemolymph of infected Biomphalaria and Bulinus, respectively, followed by carbohydrate composition analysis revealed a high content of fucose in both glycans. Methylation analysis demonstrated exclusively terminal fucose for the target antigen of KCS and terminal as well as internal fucose for the one of E2. Removal of terminal fucose abolished reactivity with both monoclonal antibodies. Both glycans are different from previously characterized schistosome carbohydrates. Their biological function(s) remain to be defined.

Glycoconjugates from Parasitic Helminths: Structure Diversity and Immunobiological Implications

We have provided an account of the progress we and others have made over the last decade on the structural characterization of glycans from parasitic helminths. We hope to have illustrated a few principles and patterns governing helminth glycosylation, as well as the experimental approaches adopted and their associated strengths and limitations. Schistosomes remain the best studied systems but are still punctuated with gaps of knowledge. An important theme developed here is the regulated developmental stage-specific expression of various glycan epitopes and their interplay with immediate host environments for successful parasitism. It is anticipated that more novel or unusual structures will continuously be uncovered in the future and that despite many difficulties, current analytical techniques should be well up to meet the challenge in at least elucidating the major or key glycoconjugates from each of the diverse range of worms. The bottle neck will in fact reside in finding suitable experimental models to test their putative immunobiological functions from which the intricate host-parasite interactions can be delineated and rational vaccine design be achieved. The glycobiology of parasitic helminths is an area waiting to be more fully explored and the rewards should be sweet.

Schistosoma mansoni: adhesion of mannan-binding lectin to surface glycoproteins of cercariae and adult worms

Schistosoma mansoni is a blood-dwelling trematode which can persist for several years in the vessels of the human host. The schistosomal surface has been extensively characterized by lectin binding studies, revealing the carbohydrate composition of the worm's tegument. Using fluorescent and scanning electron microscopy we demonstrate that the surface carbohydrates of cercariae and adult worms are the binding ligands for mannanbinding lectin (MBL), a serum protein that is part of the innate immune system. An in vitro complement activation assay with C1q-deficient complement suggests that MBL, in association with the serine proteases MASP-1 and MASP-2, is capable of fixing complement components on the schistosomal tegument and activating the complement cascade via the "MBL pathway." MBL is constitutively expressed by hepatocytes and present in the blood at a stable level. Since it is also a weak acute-phase protein and therefore upregulated in an acute-phase response we investigated the serum MBL levels in patients infected with Schistosoma sp. and in healthy control persons. An enzyme-linked immunosorbent assay indicated no differences between the two groups. Although our results suggest an involvement of MBL activated complement in vitro, its role in vivo remains to be clarified.

Characterization of an immunogenic glycocalyx on the surfaces of Cryptosporidium parvum oocysts and sporozoites

Ruthenium red staining of Cryptosporidium parvum oocysts revealed the presence of a carbohydrate matrix on their outer bilayers that is characteristic of a glycocalyx. Surface labeling of intact oocysts identified material of high molecular weight (>10(6)) that reacted positively with sera from cryptosporidium-infected patients and with immunoglobulin A monoclonal antibodies.

Ultrastructural analysis of the adult Schistosoma japonicum by lectin cytochemistry

Eight lectin probes were used to detect a range of carbohydrate residues in the tegument matrix of Schistosoma japonicum. In addition, other areas of the parasite, such as the gut, vitelline glands and flame cells, were examined for carbohydrate residues. Some minor differences in the carbohydrate residue composition between tegument orientations and between the sexes were identified. Differences between the distribution of carbohydrate residues of S. japonicum examined in this study and previous reports of Schistosoma mansoni were also noted. This study further illustrates the high level of complexity within the tegument of the adult S. japonicum and has demonstrated differences between this species and the widely studied S. mansoni.

Neutral glycolipids of Schistosoma mansoni as feasible antigens in the detection of schistosomiasis

The neutral glycolipid fraction from mouse-propagated, Schistosoma mansoni adult worms has been investigated as to its chromatographic and antigenic properties, and whether it fulfills the serodiagnostic antigen requirements of sensitivity and specificity in the detection of schistosomiasis. Serological analyses were performed by thin-layer chromatography immunostaining and ELISA. In the acute-phase form of mouse schistosomiasis, the kinetics of development of neutral glycolipid-specific antibody levels was correlated with the intensity of the initial infection and the response was dominated by IgG, as represented by the subclass IgG1. With the experimental animal helminthiases screened, glycolipid antigenicity fulfilled the fundamental traits for a serodiagnostic reagent. In the chronic-phase form of human schistosomiasis mansoni, neutral glycolipid-specific antibody levels were not correlated with the intensity of infection, as estimated from the faecal content of parasite eggs, whilst the isotypic response was dominated by IgM and IgG, the latter represented primarily by IgG1 and secondarily by IgG3. With other human helminthiases, glycolipid antigenicity was incomplete, in that, the specificity was only partially fulfilled. The reason for this incomplete specificity has been clarified, in part, by the detection of cryptic schistosomiasis infections in the cohorts of African patient sera examined.

A unique multifucosylated -3GalNAc beta 1-->4GlcNAc beta 1-->3Gal alpha 1- motif constitutes the repeating unit of the complex O-glycans derived from the cercarial glycocalyx of Schistosoma mansoni

The entire surface of the cercarial stage of the human blood fluke Schistosoma mansoni is covered by a 1-microns thick, highly immunogenic, fucose-rich glycocalyx (GCX). Using strategies based on enzymatic, chemical, and mass spectrometric analysis, we have defined the structures of the major glycans released by reductive elimination from GCX. They comprise a heterogeneous population of multifocosylated complex oligosaccharides with the following nonreducing terminal sequences: [formula: see text] Our structural data suggest that these tri- to pentafucosylated epitopes are carried on type 1, R-->Gal beta-1-->3GalNAc, and type 2, R-->Gal beta 1-->3(R-->GlcNAc beta-1-->6)GalNAc, core structures via repeat units of (3GalNAc beta 1-->4(Fuc alpha 1-->2Fuc alpha 1-->2Fuc alpha 1-->3)GlcNAc beta-1-->3Gal alpha-->)n, where n is mainly 0 and 1, and all sugars are in the pyranose form. The proposed structure represents the first instance where an alpha-galactosylated beta-GalNAc(1-->4)-beta-GlcNAc sequence occurs as a repeating unit in a glycoprotein. It is also unique in being substituted with oligofucosyl appendages. The unusual oligosaccharide structures described here, particularly the potentially immunodominant oligofucosyl moieties, are most likely responsible for the known potency of GCX in modulating various immune responses including complement activation, B cell mitogenesis, and delayed type hypersensitivity in schistosomiasis.

Effect of fetal bovine serum glycoproteins on the in vitro proliferation of the oyster parasite Perkinsus marinus: development of a fully defined medium

The oyster parasite Perkinsus marinus replicates in our medium consisting of Dulbecco modified Eagle's medium: Ham's F12 nutrient mixture (1:1) supplemented with 1-5% fetal bovine serum, with a doubling time of 24 hours during the exponential phase of the culture. Fetal bovine serum concentrations above 5% dramatically reduced parasite proliferation in a dose-dependent manner. We tested the individual effects of the three major protein components of fetal bovine serum (fetuin, transferrin and albumin) on the replication of the parasite in a serum-free medium. At the concentrations tested, fetuin enhanced parasite growth, whereas albumin had a modest positive effect and transferrin was inhibitory. Proteolytic digestion of fetuin, strongly diminished its growth-enhancing properties, indicating that the overall glycoprotein architecture may be required for activity. On the contrary, desialylation of fetuin slightly enhanced its growth-promoting activity. The addition of fetuin at 1.7 mg/ml to the serum-free DME:Ham's F12 medium yielded growth rates that are comparable to those obtained with our standard culture methodology. This has resulted in a fully defined culture medium that will allow for a rigorous characterization of excretory/secretory products involved in modulating or blocking the host's humoral and cellular defense mechanisms.

Schistosoma mansoni: immunolocalization of two different fucose-containing carbohydrate epitopes

We have used two monoclonal antibodies, 128C3/3 and 504B1, to immunolocalize their carbohydrate epitopes in different developmental stages of Schistosoma mansoni. Both epitopes contain fucose: mAb 128C3/3, as we have shown previously, recognizes fucose in a novel, possibly internal linkage (Levery et al. 1992) while mAb 504B1, as we show here, bound to the Le(x) epitope, which contains fucose alpha 1-->3 linked to N-acetyl-glucosamine. The tissue expression of these epitopes was strikingly different and both elicit an immune response in infected hosts. The mAb 128C3/3-defined epitope was exposed on the surface of all larval stages but not on adult worms; however, it was found in the excretory system of adult worms of both sexes. In contrast, surface expression of the Le(x) epitope was initiated after the transformation of cercariae to schistosomula and was maintained throughout the adult life in both sexes.

Characterization of novel fucosyl- and tyvelosyl-containing glycoconjugates from Trichinella spiralis muscle stage larvae

The monosaccharide composition of an affinity-purified family of antigenically-related Trichinella spiralis larval glycoproteins was determined by gas chromatography/mass spectrometry. This group of 6 major glycoproteins, designated TSL-1, originates in the muscle stage (L1) larval stichosome. They are present on the L1 surface and in excretory/secretory products of L1 larvae, are stage-specific, and are highly immunodominant. The glycosyl composition of the TSL-1 antigens was remarkable in 2 respects: (1) fucose accounted for 36 molar percent of the glycosyl residues; and (2) a 3,6-dideoxyhexose was identified, which accounted for at least 24 molar percent of the glycosyl residues. Previously, 3,6-dideoxyhexoses have been found only in certain Gram-negative bacterial lipopolysaccharides and in ascaroside alcohols (ascarylose) of Ascaris eggs. The 3,6-dideoxyhexose found in the TSL-1 antigens also was found in ES. This Trichinella sugar has been chemically identified as a 3,6-dideoxyarabinohexose, the same as found in Ascaris eggs. However, the absolute configuration of the TSL-1 sugar is D-(tyvelose), not L-(ascarylose) as is found in Ascaris eggs. Methylation analysis indicated that the TSL-1 3,6-dideoxy-D-arabinohexose was present entirely as non-reducing terminal residues. Approximately 83% of the fucose was also present as non-reducing terminal residues, with the remaining fucose found as 3,4-linked branched residues.

Effects of irradiation on surface carbohydrates of larvae of Schistosoma mansoni

Ultra-violet irradiated larvae of Schistosoma mansoni stimulate high levels of resistance to challenge infection in experimental animals. In the experiments presented here, the binding patterns of antisera specific for the cercarial glycocalyx, and of various lectins, demonstrate that u.v. irradiation causes a pronounced modification of the carbohydrate antigens expressed at the surface of cercariae and newly transformed schistosomula. These alterations were dependent on the irradiation dose, and on the batch of cercariae used in each experiment. Our results strongly suggest that the changes in carbohydrate antigens consequent upon u.v. irradiation may be important in generating the enhanced immunogenicity of irradiated cercariae.