Cysteine proteinases from Schistosoma haematobium adult worms.

To identify and characterize cysteine proteinases from Schistosoma haematobium, lyophilized adult worms were homogenized, and enzymes were isolated and purified. From extracts prepared in acidic buffer, 3 putative cysteine proteinases were identified either directly or indirectly. The first proteinase (ShCP1) was identified by labeling with a radioiodinated inhibitor, Z-Tyr-Ala-CHN2, as a 35-kDa protein. However, it could not be detected by silver staining, amino acid sequencing, or by a monoclonal antibody specific for a similar molecule from Schistosoma mansoni. A second cysteine proteinase, ShCP2, was purified by gel filtration and dialysis. This 32-kDa molecule was thiol-dependent and was labeled with Z-Tyr-Ala-CHN2. The amino terminal amino acid sequence of ShCP2 showed remarkable similarity (up to 77%) to that of S. mansoni cathepsin B (SmCP2) as well as to mammalian cysteine proteinases. Both ShCP1 and ShCP2 reacted with polyclonal antibodies against S. mansoni, suggesting the existence of shared antigenic epitopes. A third activity, ShCP3, was identified as possibly a distinct proteinase based on its similarities to a 28-kDa cysteine proteinase from S. mansoni. This preliminary investigation demonstrates that the overall profile of cysteine proteinases in S. haematobium is very similar to that of S. mansoni.     

Differential expression of LacdiNAc,fucosylated LacdiNAc,and Lewis x glycan antigens in intramolluscan stages of Schistosoma mansoni

We report the expression of 3 well-characterized adult Schistosoma mansoni glycan antigens among molluscan stages of the parasite. These antigens are LacdiNAc (LDN; GalNAcbeta1-4GlcNAc-R), fucosylated LacdiNAc (LDNF; GalNAc[Fucal-3]beta1-4GlcNAc-R), and Lewis x (Le(x); Gal[Fucalpha1-3]beta1-4GlcNAc-R). The presence of the glycans was determined by both immunoblot and immunohistological methods using monoclonal antibodies that specifically recognize each glycan epitope. Immunoblot analyses reveal that LDN and LDNF epitopes are expressed on many different glycoproteins, including eggs, mother sporocysts, daughter sporocysts, and cercariae, although LDN expression among daughter sporocysts is greatly reduced. LDN and LDNF epitopes are localized on the tegument and in the intrasporocyst cell masses of both in vitro-derived and in vivo-derived mother sporocysts and in the daughter sporocysts derived on day 16 after infection. Unexpectedly, high levels of LDN and LDNF glycans were detected in the infected, but not in the uninfected, snail hemolymph, suggesting that the infecting larvae secrete LDN and LDNF glycoconjugates into the snail hosts. In contrast, the expression of Le(x) antigen among the molluscan stages is highly restricted. Le(x) is present on a few high-molecular weight glycoproteins in eggs and cercariae but is undetectable in mother and daughter sporocysts. Taken together with our earlier studies on vertebrate stages of S. mansoni, these results show that LDN and LDNF glycans are conserved during schistosome development. The study further extends the evidence that Le(x) is a developmentally regulated antigen in schistosomes.     

Antibody responses to the fucosylated LacdiNAc glycan antigen in Schistosoma mansoni-infected mice and expression of the glycan among schistosomes

Infections of animals with parasitic worms, such as Schistosoma mansoni, induce humoral immune responses to carbohydrate antigens, raising the possibility that such antigens might be useful targets for the development of vaccines and new diagnostic approaches. Here we describe the identification of fucosylated LacdiNAc (LDNF) [GalNAc beta 1-4(Fuc alpha 1-3)GlcNAc-R] as a new carbohydrate antigen in S. mansoni that induces humoral immune responses in infected mice. The presence of antibodies was determined by ELISA using a neoglycoconjugate synthesized to express LDNF sequences. Sera from S. mansoni-infected, but not uninfected, mice contain IgM, IgG, IgA, and IgE antibodies to LDNF. The IgG antibodies are primarily of the IgG1 and IgG3 subclasses, with no detectable levels of the complement-fixing IgG2a and IgG2b isotypes. An IgM monoclonal antibody, designated SMLDNF1, was generated from the spleens of S. mansoni-infected mice, and the antibody exhibits specific recognition of LDNF sequences, but not other fucosylated glycans tested. Immunocytochemical analysis demonstrates that LDNF antigens are localized on the tegumental surface of adult S. mansoni. Western blot analysis indicates that LDNF sequences are expressed on numerous high-molecular-weight glycoproteins from the three major human schistosome species, as well as the bird schistosome Trichobilharzia ocellata. The identification of LDNF antigen on the tegumental glycoproteins of schistosomes and the ability to synthesize LDNF conjugates should aid in the development of glycan-based vaccines and immunodiagnostic tests for schistosomiasis and in determining the role(s) of the glycans in worm development and pathogenesis.     

Study of the distribution pattern of Schistosoma haematobium egg antigens recognised by six different monoclonal antibodies in the parasite and the host

Recently a new panel of monoclonal antibodies was developed against soluble egg antigens in the hatching fluid of Schistosoma mansoni. These antibodies have been used to develop an improved ELISA for the detection of circulating soluble egg antigens in serum and urine that would have a higher sensitivity in the immunodiagnosis of S. mansoni infections. Although these antibodies showed no improvement in the immunodiagnosis of S. mansoni infections compared with egg antigen-based ELISAs already described (Nourel Din et al., 1994a), they may have a potential role in the identification of S. haematobium infections. This study has looked into the immunolocalisation of S. haematobium egg antigens in both the parasite and the host as recognised by four newly developed monoclonal antibodies (290-2D9-A, 290-2E6-A, 290-2H12-A and 290-4A8-A) and two already described antibodies (114-5B1-A and 114-4D12-A). The antibodies 114-5B1-A and 114-4D12-A appeared to have in S. haematobium eggs a similar staining pattern when compared to S. mansoni eggs. The antibodies prepared against the hatching fluid showed a characteristic signal, especially 290-2E6-A. These antibodies recognised a component originating from the lateral glands of the miracidium. In the host a similar immunohistochemical tissue localisation pattern (mainly phagocytising reticulo-endothelial cells) was seen as previously described for S. mansoni infected hamsters.     

Characterization of developmentally regulated epitopes of Schistosoma mansoni egg glycoprotein antigens

The chemical and antigenic composition of a major group of concanavalin A-binding glycoprotein antigens of Schistosoma mansoni eggs was examined by the use of monoclonal antibodies. The individual glycoproteins of this group each displayed a very wide range of apparent m.w. and had isoelectric points of less than 5 when analyzed by two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis. These glycoproteins could be chemically labeled with 125Iodine by two different methods and biosynthetically labeled with 35S-methionine during in vitro synthesis by isolated eggs. By using five monoclonal antibodies, the individual egg glycoproteins were shown to share several antigenic determinants when analyzed by radioimmunoprecipitation and solid-phase binding assays. These epitopes were present in a high level, and the degree of expression appeared to be developmentally regulated. In addition, Schistosoma haematobium and Schistosoma japonicum eggs contained antigenically related glycoprotein antigens. Preliminary evidence suggests that the epitopes involve carbohydrate moieties.     

Structural characterization of N-glycans from the freshwater snail Biomphalaria glabrata cross-reacting with Schistosoma mansoni glycoconjugates

The human parasitic trematode Schistosoma mansoni has a complex life cycle that includes the freshwater snail Biomphalaria glabrata as intermediate host. Within each stage, the parasite synthesizes a wide array of glycoconjugates, exhibiting, in part, unique carbohydrate structures. In addition, the parasite expresses definitive host-like sugar epitopes, such as Lewis X determinants, supporting the concept of carbohydrate-mediated molecular mimicry as an invasion and survival strategy. In the present study, we investigated whether common carbohydrate determinants occur also at the level of the intermediate host. To this end, a structural characterization of hemolymph glycoprotein-N-glycans of B. glabrata was performed. N-glycans were released from tryptic glycopeptides and labeled with 2-aminopyridine. Sugar chains serologically cross-reacting with S. mansoni glycoconjugates were isolated by immunoaffinity chromatography using a polyclonal antiserum directed against schistosomal egg antigens and fractionated by Aleuria aurantia lectin affinity chromatography and high-performance liquid chromatography. Obtained glycans were analyzed by different mass spectrometric techniques as well as by monosaccharide constituent and linkage analysis. The results revealed a highly heterogeneous oligosaccharide pattern. Cross-reacting species represented about 5% of the total glycans and exhibited a terminal Fuc(alpha1-3)GalNAc unit, a (1-2)-linked xylosyl residue, or both types of structural motifs. In conclusion, our study demonstrates the presence of common carbohydrate epitopes also at the level of S. mansoni and its intermediate host.     

Mice infected with Schistosoma mansoni generate antibodies to LacdiNAc (GalNAc beta 1-->4GlcNAc) determinants.

Schistosoma mansoni is a parasitic trematode infecting humans and animals. We reported previously that adult S. mansoni synthesizes complex type biantennary N-glycans bearing the terminal sequence GalNAc beta 1-->4GlcNAc-R (lacdiNAc or LDN). We now report that mice infected with S. mansoni generate antibodies to LDN, as assessed by ELISA using a synthetic neoglycoconjugate containing LDN sequences. Sera of infected mice, but not uninfected mice, contained primarily IgM and low levels of IgG toward LDN. Interestingly, these antibodies also recognize bovine milk glycoproteins, which are known to express LDN sequences. The anti-LDN in sera of infected mice were affinity purified on immobilized bovine milk glycoproteins and shown to specifically bind LDN. An IgM monoclonal antibody (SMLDN1.1) was derived from the spleens of S. mansoni infected mice and shown to specifically bind LDN determinants. Immunoblots with affinity purified anti-LDN and SMLDN1.1 demonstrate that LDN sequences occur primarily on N-glycans of numerous glycoproteins of adult S. mansoni. LDN sequences are also expressed in many glycoproteins from S. japonicum and S. haematobium. The availability of antibody to LDN determinants should aid in defining the roles of these glycans in helminth and vertebrate biology.     

Fucosyltransferases in Schistosoma mansoni development

Glycoconjugate-bound fucose, abundant in the parasite Schistosoma mansoni, has been found in the form of Fucalpha1,3GlcNAc, Fucalpha1,2Fuc, Fucalpha1,6GlcNAc, and perhaps Fucalpha1,4GlcNAc linkages. Here we quantify fucosyltransferase activities in three developmental stages of S. mansoni. Assays were performed using fluorophore-assisted carbohydrate electrophoresis with detection of radioactive fucose incorporation from GDP-[(14)C]-fucose into structurally defined acceptors. The total fucosyltransferase-specific activity in egg extracts was 50-fold higher than that in the other life stages tested (cercaria and adult worms). A fucosyltransferase was detected that transferred fucose to type-2 oligosaccharides (Galbeta1,4GlcNAc-R), both sialylated (with the sialic acid attached to the terminal Gal by alpha2,3 or 2,6 linkage) and nonsialylated. Another fucosyltransferase was identified that transferred fucose to lactose-based and type-2 fucosylated oligosaccharides, such as LNFIII (Galbeta1,4(Fucalpha1,3)GlcNAcbeta1,3Galbeta1,4Glc). A low level of fucosyltransferase that transfers fucose to no-sialylated type-1 oligosaccharides (Galbeta1,3GlcNAc-R) was also detected. These studies revealed multifucosylated products of the reactions. In addition, the effects of fucose-type iminosugars inhibitors were tested on schistosome fucosyltransferases. A new fucose-type 1-N-iminosugar was four- to sixfold more potent as an inhibitor of schistosome fucosyltransferases in vitro than was deoxyfuconojirimycin. In vivo, this novel 1-iminosugar blocked the expression of a fucosylated epitope (mAb 128C3/3 antigen) that is associated with the pathogenesis of schistosomiasis.     

Identification of Schistosoma mansoni glycolipids that share immunogenic carbohydrate epitopes with glycoproteins

The immunoreactivity of sera of infected hosts against glycolipids derived from Schistosoma mansoni eggs, adult male worms, and cercariae was analyzed by immunostaining of glycolipids resolved by high-performance thin-layer chromatography. Eggs contained the greatest number of immunogenic glycolipids and bound the largest proportion of serum antibodies. Virtually all of the immunogenic egg glycolipids were neutrally charged and contained oligosaccharide chains larger in size than five sugar residues. The glycolipids of each developmental stage were shown by use of five monoclonal antibodies to share schistosome-specific carbohydrate epitopes that were also present on glycoproteins. Several of the carbohydrate epitopes were expressed throughout the life cycle, yet the overall structures of the glycolipids were not conserved. Quantitative analyses by solid-phase binding assays indicated that the carbohydrate epitopes were differentially expressed between the glycolipids and glycoproteins of developmental stages. Sera from infected humans and mice both contained very high levels of anti-carbohydrate antibodies that were reactive with the glycolipids, irrespective of the stage or intensity of disease. Mice harboring unisexual infections of either male or female worms also recognized the egg glycolipids in a pattern indistinguishable from that of patently infected mice. A greater proportion of the humoral response against egg antigens in infected humans was directed against protein determinants, as compared with infected mice.     

Echinostoma paraensei: hemocytes of Biomphalaria glabrata as targets of echinostome mediated interference with host snail resistance to Schistosoma mansoni

Earlier in vivo work by Lie et al. (1977) indicated that the innate resistance of the 10R2 strain of Biomphalaria glabrata to PR1 Schistosoma mansoni could be interfered with if the snails were infected previously with another trematode, Echinostoma paraensei. We have studied this interference phenomenon using in vitro methods in an attempt to understand its mechanistic basis. Hemolymph, derived from 10R2 snails infected with E. paraensei for 14-28 days, killed 25% of S. mansoni sporocysts in vitro, significantly less (P less than 0.001) than the 90% killing rate observed with hemolymph from uninfected, control 10R2 snails. Hemolymph from the infected 10R2 snails and from schistosome susceptible M line snails did not differ significantly (P greater than 0.1) in their relative inability to kill S. mansoni sporocysts in vitro. The defect in sporocyst killing exhibited by echinostome infected 10R2 snails was traced to the cellular, rather than the humoral, component of the hemolymph. Preparations containing uninfected 10R2 snail hemolymph and echinostome daughter rediae exhibited significantly less (P less than 0.001) killing of S. mansoni sporocysts than did controls containing only 10R2 hemolymph and S. mansoni sporocysts. Our results suggest that echinostome larvae release factors that interfere with the ability of B. glabrata hemocytes to kill S. mansoni sporocysts.     

IgM antibodies recognizing carbohydrate epitopes shared between schistosomula and miracidia of Schistosoma mansoni that block in vitro killing

A series of monoclonal antibodies (mAb) was raised in mice against Schistosoma mansoni, which recognized a carbohydrate determinant on a major Mr greater than 200,000 schistosomulum surface antigen. These mAb cross-reacted with the surface of cercariae and miracidia and with schistosomula of S. haematobium and S. bovis. Other mAb were generated that only recognized a Mr 20,000 schistosomulum surface antigen; they did not cross-react with eggs or miracidia and were species specific. The anti-Mr 20,000 mAb of the IgG1 isotype exhibited high levels of complement-dependent cytotoxicity to schistosomula in vitro. IgM mAb that recognized carbohydrate epitopes of the Mr greater than 200,000 surface antigen blocked the lethal activity of the anti-Mr 20,000 mAb. The IgM anti-Mr greater than 200,000 mAb also reduced complement-dependent cytotoxicity of serum from mice vaccinated with irradiated cercariae.     

Localization and identification of Schistosoma mansoni/KLH-crossreactive components in infected mice.

KLH (Keyhole limpet hemocyanin) is highly immunogenic, and crossreactive epitopes occur widely in nature. In schistosomiasis, infected hosts generate antibodies reactive with KLH. This is of diagnostic importance but we lack detailed information on the immunogen-carrying molecules and their distribution in the worm. We used anti-KLH antibodies to localize cross-reacting epitopes in the various developmental stages of the parasite in experimental Schistosoma mansoni infection. The staining results show KLH crossreactivity in the life stages of the parasite. By immunoblotting we show that KLH-crossreactive antigenic epitopes in the parasite eggs are carbohydrates, also recognized by antibodies against soluble schistosome egg antigens. The localizations in the larval stages and in adult worms suggest that crossreacting antigenic epitopes are secretory products.     

Epidemiology of mixed Schistosoma mansoni and Schistosoma haematobium infections in northern Senegal

Due to the large overlap of Schistosoma mansoni- and Schistosoma haematobium-endemic regions in Africa, many people are at risk of co-infection, with potential adverse effects on schistosomiasis morbidity and control. Nonetheless, studies on the distribution and determinants of mixed Schistosoma infections have to date been rare. We conducted a cross-sectional survey in two communities in northern Senegal (n=857) to obtain further insight into the epidemiology of mixed infections and ectopic egg elimination. Overall prevalences of S. mansoni and S. haematobium infection were 61% and 50%, respectively, in these communities. Among infected subjects, 53% had mixed infections and 8% demonstrated ectopic egg elimination. Risk factors for mixed infection - i.e. gender, community of residence and age - were not different from what is generally seen in Schistosoma-endemic areas. Similar to overall S. mansoni and S. haematobium infections, age-related patterns of mixed infections showed the characteristic convex-shaped curve for schistosomiasis, with a rapid increase in children, a peak in adolescents and a decline in adults. Looking at the data in more detail however, the decline in overall S. haematobium infection prevalences and intensities appeared to be steeper than for S. mansoni, resulting in a decrease in mixed infections and a relative increase in single S. mansoni infections with age. Moreover, individuals with mixed infections had higher infection intensities of both S. mansoni and S. haematobium than those with single infections, especially those with ectopic egg elimination (P<0.05). High infection intensities in mixed infections, as well as age-related differences in infection patterns between S. mansoni and S. haematobium, may influence disease epidemiology and control considerably, and merit further studies into the underlying mechanisms of Schistosoma infections in co-endemic areas.     

Identification of the Boudicca and Sinbad retrotransposons in the genome of the human blood fluke Schistosoma haematobium

Schistosomes have a comparatively large genome, estimated for Schistosoma mansoni to be about 270 megabase pairs (haploid genome). Recent findings have shown that mobile genetic elements constitute significant proportions of the genomes of S. mansoni and S. japonicum. Much less information is available on the genome of the third major human schistosome, S. haematobium. In order to investigate the possible evolutionary origins of the S. mansoni long terminal repeat retrotransposons Boudicca and Sinbad, several genomes were searched by Southern blot for the presence of these retrotransposons. These included three species of schistosomes, S. mansoni, S. japonicum, and S. haematobium, and three related platyhelminth genomes, the liver flukes Fasciola hepatica and Fascioloides magna and the planarian, Dugesia dorotocephala. In addition, Homo sapiens and three snail host genomes, Biomphalaria glabrata, Oncomelania hupensis, and Bulinus truncatus, were examined for possible indications of a horizontal origin for these retrotransposons. Southern hybridization analysis indicated that both Boudicca and Sinbad were present in the genome of S. haematobium. Furthermore, low stringency Southern hybridization analyses suggested that a Boudicca-like retrotransposon was present in the genome of B. truncatus, the snail host of S. haematobium.     

Localization of carbohydrate determinants common to Biomphalaria glabrata as well as to sporocysts and miracidia of Schistosoma mansoni

The presence of antigenic carbohydrate epitopes shared by Biomphalaria glabrata as well as by the sporocysts and miracidia representing snail-pathogenic larval stages of Schistosoma mansoni was assayed by immunohistochemical staining of paraformaldehyde-fixed tissues. To this end, both polyclonal rabbit antiserum raised against soluble egg antigens (SEA) of S. mansoni and monoclonal antibodies recognizing the carbohydrate epitopes LDN [GalNAc(beta1-4)GlcNAc(beta1-)], F-LDN [Fuc(alpha1-3)GalNAc(beta1-4)GlcNAc(beta1-)], LDN-F [GalNAc(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-)], LDN-DF [GalNAc(beta1-4)[Fuc(alpha1-2)Fuc(alpha1-3)]GlcNAc(beta1-)] and Lewis X [Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-)] were used. Intriguingly, anti-SEA serum as well as anti-F-LDN antibodies displayed significant binding in the foot region, anterior tissue and the hepatopancreas of uninfected snails, whereas the Lewis X epitope was only weakly detectable in the latter tissue. In contrast, increased binding of antibodies recognizing LDN, LDN-F and LDN-DF was observed in infected snail tissue, in particular in regions involved in sporocystogenesis, in addition to an enhanced binding of anti-SEA serum and antibodies reacting with F-LDN. A pronounced expression of most of these carbohydrate antigens was also observed at the surface of miracidia. Hence, the detection of shared carbohydrate determinants in uninfected snail tissue, sporocysts and miracidia may support the hypothesis of carbohydrate-based molecular mimicry as a survival strategy of S. mansoni.     

Schistosoma mansoni: control of hepatotoxicity and egg excretion by immune serum in infected immunosuppressed mice is schistosome species-specific, but not S. mansoni strain-specific.

Immunosuppressed mice infected with Schistosoma mansoni suffer from an acute hepatotoxicity reaction, and they fail to excrete as many parasite eggs as comparably infected immunologically intact control animals. The hepatotoxicity was shown here to be preventable, and egg excretion rates were enhanced, by transfer of serum from donors with chronic S. mansoni infections, but not by serum from donors with heterologous infections of Schistosoma haematobium, Schistosoma bovis, or Schistosoma japonicum. The effects of the transferred sera are considered to be due to specific antibody, but the possibility of cytokine involvement is discussed. A high degree of serological cross-reactivity was found between sera from mice infected with the different schistosome species and unfractionated egg homogenate (SEA) in ELISA. Cross-reactivity of the heterologous sera was, however, reduced against CEF6, a partially purified fraction of S. mansoni eggs that contains the putative hepatotoxin and has serodiagnostic potential. S. mansoni isolates from Puerto Rico, Brazil, Egypt, and Kenya shared similar characteristics with respect to the immune dependence of egg excretion and hepatotoxicity in immunosuppressed mice. The S. mansoni geographic isolates were also indistinguishable serologically, in terms of both the capacity of respective infection sera to neutralize hepatotoxicity and in their capacity to promote egg excretion of the other isolates in vivo. Complete immunological cross-reactivity of the geographically distinct isolates was also observed in ELISA with both CEF6 and SEA. Utilization of CEF6 for serodiagnosis of schistosomiasis mansoni is therefore unlikely to be restricted by geographical considerations.     

Evidence for the presence of active cytochrome P450 systems in Schistosoma mansoni and Schistosoma haematobium adult worms

Extracts of the adult worms of both Schistosoma mansoni and Schistosoma haematobium can metabolise some typical P450 substrates but to differing degrees. S. mansoni worm extracts displayed a approximately 12-fold higher specific activity for an aminopyrine substrate than rat liver microsomes. At 4 mM substrate concentration the demethylation reaction with N-nitrosodimethylamine (NDMA) (5 nmol HCHO/mg protein/min) was only half that of rat liver microsomes, whereas in extracts of S. haematobium, no detectable activity was found towards NDMA. Using ethylmorphine as substrate the demethylation activity of S. mansoni extracts (1.82 nmol HCHO/mg protein/min) was 5.5-fold lower than that of rat liver microsomes. Benzphetamine demethylase activity was also readily detectable in S. mansoni worm extracts at 6.79 nmol HCHO/mg protein/min compared with 10.20 nmol HCHO/mg protein/min in the case of rat liver microsomes. When aniline was used as substrate, surprisingly, no activity was found in worm extracts of either S. mansoni or S. haematobium, whereas rat liver microsomes showed high activity towards this amine. The anti-P450 2E1 and 2B1/2 cross-reacted with both worm homogenates and gave a specific band corresponding to a protein of molecular weight of approximately 50.0 kDa. A study with anti-P450 IVA antibody revealed that while this protein was strongly expressed in S. haematobium worm extracts, no immunoreactivity was observed with extracts of S. mansoni. Immunoblotting analyses with anti-P450 IIIA and P450 1A1 did not detect immunoreactive protein in either S. mansoni or S. haematobium.     

Identification and characterization of keyhole limpet hemocyanin N-glycans mediating cross-reactivity with Schistosoma mansoni

Keyhole limpet hemocyanin (KLH) of the mollusc Megathura crenulata is known to serologically cross-react with Schistosoma mansoni glycoconjugates in a carbohydrate-dependent manner. To elucidate the structural basis for this cross-reactivity, KLH glycans were released from tryptic glycopeptides and fluorescently labeled. Cross-reacting glycans were identified using a polyclonal antiserum reacting with soluble S. mansoni egg antigens, isolated by a three-dimensional fractionation scheme and analyzed by different mass spectrometric techniques as well as linkage analysis and exoglycosidase treatment. The results revealed that cross-reacting species comprise approximately 4.5% of released glycans. They all represent novel types of N-glycans with a Fuc(alpha1-3)GalNAc(beta1-4)[Fuc(alpha1-3)]GlcNAc motif, which is known to occur also in schistosomal glycoconjugates. The tetrasaccharide unit is attached to the 3-linked antenna of a trimannosyl core, which can be further decorated by galactosyl residues, a xylose residue in 2-position of the central mannose and/or a fucose at the innermost N-acetylglucosamine. This study provides for the first time detailed structural data on the KLH carbohydrate entities responsible for cross-reactivity with glycoconjugates from S. mansoni.     

Schistosome antigen gp50 is responsible for serological cross-reactivity with Trichinella spiralis.

The 50-kDa component (gp50) present in Schistosoma mansoni eggs and secretions of the various life stages of the parasite was recognized by experimentally infected mice and by humans with S. mansoni, Schistosoma haematobium, and Schistosoma japonicum infection. All sera reacting with crude S. mansoni-soluble egg antigens (SEA) also reacted strongly with gp50 in enzyme-linked immunosorbent assay. No reactivity against gp50 was seen with sera from individuals without schistosomiasis, with the exception of sera from patients with Trichinella spiralis infection. All of 10 sera from patients with trichinellosis also reacted with schistosomes by immunofluorescence essentially recognizing testes, ovaries, ootype epithelium and ducts of the reproductive system. Cross-reacting antigens were seen in T. spiralis hypodermis, stichocytes and possibly germinal primordia using anti-gp50 monoclonal antibodies and anti-gp50-positive schistosomiasis patient sera. The results suggest that the anti-gp50 antibody response constitutes a significant part of the anti-SEA antibody response in infected individuals and is a major reason for the previously recognized serological cross-reactivity between T. spiralis and schistosome species.     

Pattern of cercarial emergence of Schistosoma curassoni from Niger and comparison with three sympatric species of schistosomes.

The emergence pattern of Schistosoma curassoni cercariae from Bulinus umbilicatus, whose adult worms parasitize bovine, caprine, and ovine ungulates in Niger, is of a circadian type with a mean emission time at 0855 hr +/- 1 hr 6 min, characteristic of the schistosome species parasitizing domestic or wild cattle. The comparison of this cercarial emergence pattern with those of the other 3 sympatric species of schistosomes (Schistosoma haematobium, Schistosoma bovis, and Schistosoma mansoni) shows a significant difference between the chronobiology of the cercariae infective for human and those infective for bovine hosts. This difference may improve epidemiological surveys based on snail prevalences by allowing the distinction between bulinids infected with human and bovine parasites.