Reduced T regulatory cell response during acute Plasmodium falciparum infection in Malian children co-infected with Schistosoma haematobium

Background

Regulatory T cells (Tregs) suppress host immune responses and participate in immune homeostasis. In co-infection, secondary parasite infections may disrupt the immunologic responses induced by a pre-existing parasitic infection. We previously demonstrated that schistosomiasis-positive (SP) Malian children, aged 4–8 years, are protected against the acquisition of malaria compared to matched schistosomiasis-negative (SN) children.

Methods and Findings

To determine if Tregs contribute to this protection, we performed immunologic and Treg depletion in vitro studies using PBMC acquired from children with and without S. haematobium infection followed longitudinally for the acquisition of malaria. Levels of Tregs were lower in children with dual infections compared to children with malaria alone (0.49 versus 1.37%, respectively, P = 0.004) but were similar months later, during a period with negligible malaria transmission. The increased levels of Tregs in SN subjects were associated with suppressed serum Th1 cytokine levels, as well as elevated parasitemia compared to co-infected counterparts.

Conclusions

These results suggest that lower levels of Tregs in helminth-infected children correlate with altered circulating cytokine and parasitologic results which may play a partial role in mediating protection against falciparum malaria.     

Circulating soluble antigens and antibody in schistosomiasis.

Some patients with Schistosoma mansoni and S. haematobium infections were shown to have soluble schistosomal antigen in their plasma. Antibody to this antigen and to other antigens of adult worms were also present. These findings may be relevant to schistosomal-related immune-complex disease, especially the nephrotic syndrome.     

Relationship between Malaria Incidence and IgG Levels to Plasmodium falciparum Merozoite Antigens in Malian Children: Impact of Hemoglobins S and C

Heterozygous hemoglobin (Hb) AS (sickle-cell trait) and HbAC are hypothesized to protect against Plasmodium falciparum malaria in part by enhancing naturally-acquired immunity to this disease. To investigate this hypothesis, we compared antibody levels to four merozoite antigens from the P. falciparum 3D7 clone (apical membrane antigen 1, AMA1-3D7; merozoite surface protein 1, MSP1-3D7; 175 kDa erythrocyte-binding antigen, EBA175-3D7; and merozoite surface protein 2, MSP2-3D7) in a cohort of 103 HbAA, 73 HbAS and 30 HbAC children aged 3 to 11 years in a malaria-endemic area of Mali. In the 2009 transmission season we found that HbAS, but not HbAC, significantly reduced the risk of malaria compared to HbAA. IgG levels to MSP1 and MSP2 at the start of this transmission season inversely correlated with malaria incidence after adjusting for age and Hb type. However, HbAS children had significantly lower IgG levels to EBA175 and MSP2 compared to HbAA children. On the other hand, HbAC children had similar IgG levels to all four antigens. The parasite growth-inhibitory activity of purified IgG samples did not differ significantly by Hb type. Changes in antigen-specific IgG levels during the 2009 transmission and 2010 dry seasons also did not differ by Hb type, and none of these IgG levels dropped significantly during the dry season. These data suggest that sickle-cell trait does not reduce the risk of malaria by enhancing the acquisition of IgG responses to merozoite antigens.     

Impact of Acute Malaria on Pre-Existing Antibodies to Viral and Vaccine Antigens in Mice and Humans

Vaccine-induced immunity depends on long-lived plasma cells (LLPCs) that maintain antibody levels. A recent mouse study showed that Plasmodium chaubaudi infection reduced pre-existing influenza-specific antibodies—raising concerns that malaria may compromise pre-existing vaccine responses. We extended these findings to P. yoelii infection, observing decreases in antibodies to model antigens in inbred mice and to influenza in outbred mice, associated with LLPC depletion and increased susceptibility to influenza rechallenge. We investigated the implications of these findings in Malian children by measuring vaccine-specific IgG (tetanus, measles, hepatitis B) before and after the malaria-free 6-month dry season, 10 days after the first malaria episode of the malaria season, and after the subsequent dry season. On average, vaccine-specific IgG did not decrease following acute malaria. However, in some children malaria was associated with an accelerated decline in vaccine-specific IgG, underscoring the need to further investigate the impact of malaria on pre-existing vaccine-specific antibodies.     

The breadth, but not the magnitude, of circulating memory B cell responses to P. falciparum increases with age/exposure in an area of low transmission

Background

Malaria caused by Plasmodium falciparum remains a major cause of death in sub-Saharan Africa. Immunity against symptoms of malaria requires repeated exposure, suggesting either that the parasite is poorly immunogenic or that the development of effective immune responses to malaria may be impaired.

Methods

We carried out two age-stratified cross-sectional surveys of anti-malarial humoral immune responses in a Gambian village where P. falciparum malaria transmission is low and sporadic. Circulating antibodies and memory B cells (MBC) to four malarial antigens were measured using ELISA and cultured B cell ELISpot.

Findings and Conclusions

The proportion of individuals with malaria-specific MBC and antibodies, and the average number of antigens recognised by each individual, increased with age but the magnitude of these responses did not. Malaria-specific antibody levels did not correlate with either the prevalence or median number of MBC, indicating that these two assays are measuring different aspects of the humoral immune response. Among those with immunological evidence of malaria exposure (defined as a positive response to at least one malarial antigen either by ELISA or ELISPOT), the median number of malaria-specific MBC was similar to median numbers of diphtheria-specific MBC, suggesting that the circulating memory cell pool for malaria antigens is of similar size to that for other antigens.     

Effects of Age,Hemoglobin Type and Parasite Strain on IgG Recognition of Plasmodium falciparum–Infected Erythrocytes in Malian Children

Background

Naturally-acquired antibody responses to antigens on the surface of Plasmodium falciparum-infected red blood cells (iRBCs) have been implicated in antimalarial immunity. To profile the development of this immunity, we have been studying a cohort of Malian children living in an area with intense seasonal malaria transmission.

Methodology/Principal Findings

We collected plasma from a sub-cohort of 176 Malian children aged 3-11 years, before (May) and after (December) the 2009 transmission season. To measure the effect of hemoglobin (Hb) type on antibody responses, we enrolled age-matched HbAA, HbAS and HbAC children. To quantify antibody recognition of iRBCs, we designed a high-throughput flow cytometry assay to rapidly test numerous plasma samples against multiple parasite strains. We evaluated antibody reactivity of each plasma sample to 3 laboratory-adapted parasite lines (FCR3, D10, PC26) and 4 short-term-cultured parasite isolates (2 Malian and 2 Cambodian). 97% of children recognized ≥1 parasite strain and the proportion of IgG responders increased significantly during the transmission season for most parasite strains. Both strain-specific and strain-transcending IgG responses were detected, and varied by age, Hb type and parasite strain. In addition, the breadth of IgG responses to parasite strains increased with age in HbAA, but not in HbAS or HbAC, children.

Conclusions/Significance

Our assay detects both strain-specific and strain-transcending IgG responses to iRBCs. The magnitude and breadth of these responses varied not only by age, but also by Hb type and parasite strain used. These findings indicate that studies of acquired humoral immunity should account for Hb type and test large numbers of diverse parasite strains.     

Western blot diagnosis of vivax malaria with multiple stage-specific antigens of the parasite.

Western blot analysis was performed to diagnose vivax malaria using stage-specific recombinant antigens. Genomic DNA from the whole blood of a malaria patient was used as templates to amplify the coding regions for the antigenic domains of circumsporozoite protein (CSP-1), merozoite surface protein (MSP-1), apical merozoite antigen (AMA-1), serine repeat antigen (SERA), and exported antigen (EXP-1) of Plasmodium vivax. Each amplified DNA fragment was inserted into a pGEX-4T plasmid to induce the expression of GST fusion protein in Escherichia coli by IPTG. The bacterial cell extracts were separated on 10% SDS-PAGE followed by western blot analysis with patient sera which was confirmed by blood smear examination. When applied with patient sera, 147 (91.9%) out of 160 vivax malaria, 12 (92.3%) out of 13 falciparum malaria, and all 9 vivax/falciparum mixed malaria reacted with at least one antigen, while no reactions occurred with 20 normal uninfected sera. In the case of vivax malaria, CSP-1 reacted with 128 (80.0%) sera, MSP-1 with 102 (63.8%), AMA-1 with 128 (80.0%), SERA with 115 (71.9%), and EXP-1 with 89 (55.6%), respectively. We obtained higher detection rates when using 5 antigens (91.9%) rather than using each antigen solely (55.6-80%), a combination of 2 (76.3-87.5%), 3 (85.6-90.6%), or 4 antigens (89.4-91.3%). This method can be applied to serological diagnosis, mass screening in endemic regions, or safety test in transfusion of prevalent vivax malaria.     

Anti-malaria humoral responses in children exposed to Plasmodium falciparum and Schistosoma haematobium

Antibody responses directed against the Plasmodium falciparum antigens, total extract, anti-merozoite surface protein-3 (MSP3b) and glutamate-rich protein (Glurp-R0) were studied in 42 children exposed to both Schistosoma haematobium and P. falciparum infections. The association between levels of the anti-malaria IgG subclasses and IgM with host age, sex, schistosome infection intensity and schistosome specific antibodies was studied before chemotherapeutic treatment of schistosome infections. This showed a significant negative association between schistosome infection intensity and levels of IgG1, IgG3, and IgG4 directed against malaria total extract antigen, and a positive association between levels of anti-schistosome soluble egg antigen IgG2, IgG3, and IgG4 and levels of the same subclasses directed against malaria total extract antigens. The effect of treating schistosome infections with praziquantel on malaria specific responses was also studied. This treatment resulted in increases in significant IgG4 levels against MSP3b and IgM against Glurp R0. Treatment also resulted in a significant decrease in IgG4 levels against Glurp R0. Host age, sex or pre-treatment infection intensity was not associated with the magnitude of change in the two IgG4 responses while males showed a significantly higher increase in levels of IgM. The results suggest cross reactivity between schistosome and malaria antigens in this population.     

B cell activation: role of dendritic and T cell factors in the response to thymic-independent and -dependent antigens

We described a cloned dendritic cell, clone Den-1, that is a potent accessory cell for some B cell responses. Clone Den-1 produces a novel lymphokine that is distinct from previously described factors produced by T cells. In the present study, we compare the role of nonspecific helper factors produced by Den-1 (Den-1 SN) or the T cell thymoma EL4 (EL4-SN) in promotion of B cell plaque-forming cell (PFC) responses to a variety of antigens. We find that the antigen in culture determines the B cell requirement for dendritic and/or T cell factors. B cell PFC responses to TNP-Brucella abortus (BA) and TNP-lipopolysaccharide (LPS) are greatly increased by EL4-SN but show little, if any, enhancement with Den-1 SN. Responses to TNP-polyacrylamide are reconstituted by either Den-1 SN or EL4-SN, whereas responses to TNP-Ficoll, TNP-dextran and TNP-levan are reconstituted by Den-1 SN and are much less sensitive to factors present in EL4-SN. Responses to SRBC require the presence of both Den-1 SN and EL4-SN. We also show that the time at which Den-1 SN must be provided to the B cell is dependent on the antigen in culture. Our findings are discussed in terms of present classification of antigens based on their ability to stimulate various B cell subpopulations.     

Novel vaccine strategies to T-independent antigens

T cell independent antigens do not require T cell help to induce an immune response, and are characterized by a lack of immunologic memory. These antigens can be divided into two classes, TI-1 or TI-2. TI-1 antigens, such as bacterial lipopolysaccharide, are potent B-cell mitogens, capable of non-specific, polyclonal activation of B cells. In contrast, TI-2 antigens can only activate mature B cells and consist of highly repetitive structures, such as capsular polysaccharides (CPS) from bacteria. Many vaccines currently in use consist of purified capsular polysaccharides from pathogenic bacteria such as Streptococcus pneumoniae and Neisseria meningitidis. These vaccines are efficacious in immune-competent adults, however, due to their TI-2 nature, are not effective in children <2 years of age. Converting polysaccharides into T cell dependent (TD) antigens, allows children, <2, to produce an effective immune response. This review focuses on various strategies used to convert the immune response to polysaccharide antigens from TI-2 to a TD response. Conjugate vaccines, anti-idiotypic antibodies, phage display library technology and DNA vaccines are discussed.     

Schistosoma mansoni, S. haematobium, and S. japonicum: identification of genus- and species-specific antigenic egg glycoproteins

Immunoreactive egg glycoproteins of Schistosoma mansoni, S. haematobium, and S. japonicum which are genus- and species-specific, or react with sera of patients infected with other parasites, have been identified. Egg proteins were labeled with Iodine-125, and the concanavalin A-binding glycoproteins were immunoprecipitated with sera of patients infected with one of four species of Schistosoma or Trichinella spiralis, Taenia solium, Echinococcus granulosus, Entamoeba histolytica, or Wuchereria bancrofti. These immunoprecipitates were analyzed by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Despite the strikingly different patterns of glycoproteins of the African species, the antibody immune responses of patients infected with S. mansoni and S. haematobium were found to be so similar that differentiation could not be established. In contrast, sera of patients infected with S. japonicum, S. mekongi, or parasites not of the genus Schistosoma, immunoprecipitated fewer of the major S. mansoni or S. haematobium glycoproteins. Likewise, antibody immune responses of patients infected with the Oriental schistosomes (S. japonicum and S. mekongi) could not be differentiated. Only a few quantitative differences were noted between our S. mansoni egg glycoprotein extract and a standardized soluble egg antigen extract. This study provides an explanation for the extensive cross-reactivity observed in diagnostic assays which utilize various fractions of schistosomal egg extracts as the antigen.     

Impact of the RTS,S malaria vaccine candidate on naturally acquired antibody responses to multiple asexual blood stage antigens

Background

Partial protective efficacy lasting up to 43 months after vaccination with the RTS,S malaria vaccine has been reported in one cohort (C1) of a Phase IIb trial in Mozambique, but waning efficacy was observed in a smaller contemporaneous cohort (C2). We hypothesized that low dose exposure to asexual stage parasites resulting from partial pre-erythrocytic protection afforded by RTS,S may contribute to long-term vaccine efficacy to clinical disease, which was not observed in C2 due to intense active detection of infection and treatment.

Methodology/Principal Findings

Serum collected 6 months post-vaccination was screened for antibodies to asexual blood stage antigens AMA-1, MSP-1₄₂, EBA-175, DBL-α and variant surface antigens of the R29 laboratory strain (VSA_R29). Effect of IgG on the prospective hazard of clinical malaria was estimated. No difference was observed in antibody levels between RTS,S and control vaccine when all children aged 1–4 years at enrollment in both C1 and C2 were analyzed together, and no effects were observed between cohort and vaccine group. RTS,S-vaccinated children <2 years of age at enrollment had lower levels of IgG for AMA-1 and MSP-1₄₂ (p<0.01, all antigens), while no differences were observed in children ≥2 years. Lower risk of clinical malaria was associated with high IgG to EBA-175 and VSA_R29 in C2 only (Hazard Ratio [HR]: 0.76, 95% CI 0.66–0.88; HR: 0.75, 95% CI 0.62–0.92, respectively).

Conclusions

Vaccination with RTS,S modestly reduces anti-AMA-1 and anti-MSP-1 antibodies in very young children. However, for antigens associated with lower risk of clinical malaria, there were no vaccine group or cohort-specific effects, and age did not influence antibody levels between treatment groups for these antigens. The antigens tested do not explain the difference in protective efficacy in C1 and C2. Other less-characterized antigens or VSA may be important to protection.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00197041","term_id":"NCT00197041"}}NCT00197041     

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.     

Intermediate host antigens associated with the cercariae of Schistosoma haematobium.

Bulinus (Physopsis) africanus antigens were shown to be associated with the cercarial glycocalyx of Schistosoma haematobium using immunofluorescence and the Cercarienhüllen Reaktion. It is proposed that this snail antigen may sensitise the definitive host and that resistance to further invasion by cercariae could be induced in this manner.     

Methyl-beta-Cyclodextrin treatment and filipin staining reveal the role of cholesterol in surface membrane antigen sequestration of Schistosoma mansoni and S. haematobium lung-stage larvae

Ex vivo lung-stage larvae of Schistosoma mansoni and S. haematobium do not bind specific antibodies in the indirect membrane immunofluorescence test (IF), probably as a result of confinement of the surface membrane antigens in immobile, lipid-rich sites. Treatment with the membrane-impermeable, cholesterol-extracting drug methyl-beta-cyclodextrin (MBCD) and staining with filipin III (filipin), a fluorescent polyene antibiotic widely used for the detection and quantitation of cholesterol in biomembranes, allowed us to examine the role of cholesterol in surface membrane antigen sequestration of S. mansoni and S. haematobium ex vivo lung-stage larvae. Treatment of S. mansoni larvae with MBCD elicited appreciable cholesterol depletion as judged by filipin-cholesterol fluorescence diminution, which was accompanied by a considerable increase in specific antibody binding in IF, thus suggesting that cholesterol plays a predominant role in sequestration of the surface membrane antigens of S. mansoni lung-stage schistosomula. Despite that, MBCD induced an almost complete depletion of cholesterol from the outer membrane of S. haematobium larvae; no increase in specific antibody binding in IF was evident, implying that cholesterol is not responsible for masking surface membrane antigens of S. haematobium lung-stage larvae.     

Isolation and characterization of surface antigens from Schistosoma mansoni. II. Antigenicity of radiolabeled proteins from adult worms.

Adult Schistosoma mansoni were radiolabeled in vitro with 125I Bolton-Hunter reagent. Surface membrane antigens were solubilized with non-ionic detergent, then reacted with infection or normal serum. The antigen-antibody complexes were then precipitated with staphylococcal protein A immunoadsorbent, eluted with urea and SDS, and fractionated by SDS-PAGE. The results indicated the presence of 6 to 8 tegument antigens, depending on the type of antisera used. Human antisera to S. japonicum and S. haematobium reacted with some but not all of the antigens identified with human S. mansoni infection serum; this implies the presence of species-specific tegument antigens. The molecular weights of the radiolabeled antigens ranged from 10,000 to 100,000. A large (greater than 100,000) molecular weight glycoprotein and an uncharacterized lipid fraction appeared to be precipitated nonspecifically. Immunoprecipitation methods with anti-mouse IgG and anti-mouse whole serum failed to detect the presence of hostlike antigens in the labeled extracts. Several of the labeled proteins from S. mansoni were found to react with serum from patients infected with either S. haematobium or with S. japonicum.     

ELISA detection of vivax malaria with recombinant multiple stage-specific antigens and its application to survey of residents in endemic areas

An ELISA was developed for the diagnosis of vivax malaria using multiple stage-specific recombinant antigens of Plasmodium vivax. The DNA from the whole blood of a malaria patient was used as template to amplify the coding regions for the antigenic domains of circumsporozoite protein (CSP-1), merozoite surface protein (MSP-1), apical merozoite antigen (AMA-1), serine repeat antigen (SERA), and exported antigen (EXP-1). Each amplified DNA fragment was inserted into pQE30 plasmid to induce the expression of His-tagged protein in Escherichia coli (M15 strain) by IPTG. His-tagged proteins were purified by Ni-NTA metal-affinity chromatography and used as antigens for ELISA with patient sera that were confirmed previously by blood smear examinations. When applied to patient sera, 122 (80.3%) out of 152 vivax malaria cases reacted to at least one antigen, while no reactions were observed with 128 uninfected serum samples. We applied this ELISA to the screening of 3,262 civilian residents in endemic regions near the DMZ, which resulted in 236 positively detected (7.2%) cases. This method can be applied to serological diagnosis and mass screening in endemic regions, or can be used as a safety test for transfusion blood in endemic areas.     

A malaria vaccine based on the polymorphic block 2 region of MSP-1 that elicits a broad serotype-spanning immune response

Polymorphic parasite antigens are known targets of protective immunity to malaria, but this antigenic variation poses challenges to vaccine development. A synthetic MSP-1 Block 2 construct, based on all polymorphic variants found in natural Plasmodium falciparum isolates has been designed, combined with the relatively conserved Block 1 sequence of MSP-1 and expressed in E.coli. The MSP-1 Hybrid antigen has been produced with high yield by fed-batch fermentation and purified without the aid of affinity tags resulting in a pure and extremely thermostable antigen preparation. MSP-1 hybrid is immunogenic in experimental animals using adjuvants suitable for human use, eliciting antibodies against epitopes from all three Block 2 serotypes. Human serum antibodies from Africans naturally exposed to malaria reacted to the MSP-1 hybrid as strongly as, or better than the same serum reactivities to individual MSP-1 Block 2 antigens, and these antibody responses showed clear associations with reduced incidence of malaria episodes. The MSP-1 hybrid is designed to induce a protective antibody response to the highly polymorphic Block 2 region of MSP-1, enhancing the repertoire of MSP-1 Block 2 antibody responses found among immune and semi-immune individuals in malaria endemic areas. The target population for such a vaccine is young children and vulnerable adults, to accelerate the acquisition of a full range of malaria protective antibodies against this polymorphic parasite antigen.     

Early diagnosis of Schistosoma mansoni in mice using assays directed against cercarial antigens isolated by hydrophobic chromatography

Two diagnostic assays are described for the early diagnosis of acute schistosomiasis, using a defined cercarial antigen preparation obtained by hydrophobic chromatography. Circulating IgM antibodies against this antigen fraction could be detected by ELISA as early as 1 wk after exposure in experimentally infected mice; IgM levels against other antigens and IgG levels against all the preparations examined were not significantly elevated until approximately 4-5 wk postinfection. Circulating antigen was detected as early as 3 days after exposure by a competitive inhibition ELISA using rabbit serum prepared against the cercarial antigen; antigen levels in the serum of mice with a 100-worm infection were found to exceed 100 ng/ml. Studies using sera from infected humans indicate that the assay can also recognize chronic S. mansoni, S. haematobium or S. japonicum infections. In a very limited field study, the specificity of the circulating antigen assay with regard to other helminthic infections was found to be 85%; sensitivity 100%. Preliminary characterization of the relevant antigen indicates that it is a relatively hydrophobic polypeptide with a molecular weight of approximately 41,000 daltons. The implications of these findings with regard to the treatment of travelers or the conduct of seroepidemiological studies in endemic areas are discussed.     

Expression of Lex antigen in Schistosoma japonicum and S.haematobium and immune responses to Lex in infected animals: lack of Lex expression in other trematodes and nematodes

Adults of the human parasitic trematode Schistosoma mansoni, which causes hepatosplenic/intestinal complications in humans, synthesize glycoconjugates containing the Lewis x (Lex) Galbeta1-->4(Fucalpha1-- >3)GlcNAcbeta1-->R, but not sialyl Lewis x (sLex), antigen. We now report on our analyses of Lexand sLexexpression in S.haematobium and S.japonicum, which are two other major species of human schistosomes that cause disease, and the possible autoimmunity to these antigens in infected individuals. Antigen expression was evaluated by both ELISA and Western blot analyses of detergent extracts of parasites using monoclonal antibodies. Several high molecular weight glycoproteins in both S. haematobium and S. japonicum contain the Lexantigen, but no sialyl Lexantigen was detected. In addition, sera from humans and rodents infected with S.haematobium and S.japonicum contain antibodies reactive with Lex. These results led us to investigate whether Lexantigens are expressed in other helminths, including the parasitic trematode Fasciola hepatica , the parasitic nematode Dirofilaria immitis (dog heartworm), the ruminant nematode Haemonchus contortus , and the free-living nematode Caenorhabditis elegans . Neither Lexnor sialyl-Lexis detectable in these other helminths. Furthermore, none of the helminths, including schistosomes, express Lea, Leb, Ley, or the H- type 1 antigen. However, several glycoproteins from all helminths analyzed are bound by Lotus tetragonolobus agglutinin , which binds Fucalpha1-->3GlcNAc, and Wisteria floribunda agglutinin, which binds GalNAcbeta1-->4GlcNAc (lacdiNAc or LDN). Thus, schistosomes may be unique among helminths in expressing the Lexantigen, whereas many different helminths may express alpha1,3-fucosylated glycans and the LDN motif.