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C Verwaerde

Publications and source records attributed to C Verwaerde.

36 records · Page 2Linked to original sources
PubMed1989

Protective effects of anti-antiidiotypic IgE antibodies obtained from an IgE monoclonal antibody specific for a 26-kilodalton Schistosoma mansoni antigen.

A rat IgE mAb specific for larval Ag (26 kDa, 56 kDa) has been shown to protect rats against Schistosoma mansoni infection. Immunizations of Lou/M rats performed with this IgE (Ab1) induced the production of antiidiotypic antibodies (Ab2). Moreover, after this Ab2 production, anti-antiidiotypic antibodies (Ab3) were revealed. The screening of Ab3 isotypes showed the presence of IgG Ab3 and more interestingly of IgE Ab3, i.e., the same isotype as Ab1. These IgE and IgG antibodies recognized predominantly the 26-kDa Ag and were cytotoxic for schistosomula in the presence of platelets for IgE Ab3 and eosinophils for IgG Ab3. Both IgE and IgG Ab3 conferred by passive transfer protective immunity to infected rats (up to 50%). Thus the immunization with an IgE mAb led in part to the production of Ab3 of the same isotype as Ab1. In conclusion, these results suggest that the isotype selection of the antibodies of the third generation (Ab3) might be influenced by the Ab1. The respective role of the idiotope and isotype of Ab1 in isotype regulation is discussed.

Animals↗
PubMed1988

Properties of serine proteases of Schistosoma mansoni schistosomula involved in the regulation of IgE synthesis.

The regulation of IgE synthesis in vitro and in vivo by schistosomula-released products (SRP) has been shown to be dependent on the presence of serine proteases. The present paper concerns the characterization of the enzymes involved. The labelling of SRP with [3H]diisopropyl phosphofluoridate revealed two molecules, one major with an MW of 27,500 and one minor with an MW of 29,000. The same pattern was obtained by labelling of schistosomula or cercariae surfaces as well as of the total schistosomulum homogenate. The properties of these enzymes were studied by means of various specific substrates or inhibitors of serine proteases. The specificity was relatively narrow, but had some similarity with trypsin. When added to lymphoid rat cells in culture, SRP induced an increased expression of receptors for the Fc fragment of IgE (Fc epsilon RII). This suggests that the IgE-enhancing property of SRP was due to serine protease activity which may act by enhancing the lymphocyte Fc epsilon RII.

Animals↗
PubMed1987

Functional properties of a rat monoclonal IgE antibody specific for Schistosoma mansoni.

A rat monoclonal antibody of IgE isotype (B48-14) raised against Schistosoma mansoni has been generated by the fusion of mesenteric lymph node cells from LOU/M rats immunized with a preparation of adult schistosome worms and IR973F nonsecreting rat myeloma cells. Investigation of the in vitro effector functions of this IgE antibody showed a high level of cytotoxicity against S. mansoni schistosomula in the presence of eosinophils, macrophages, and platelets. A significant level of protection (40 to 60%) against a challenge infection with S. mansoni cercariae was achieved by passive transfer experiment of B48-14 IgE to naive recipient rats. By immunoprecipitation, B48-14 IgE antibodies were shown to react with an antigen of 26 kDa present in excretion-secretion products of schistosomula, previously described as a potential immunogen eliciting a protective IgE response against schistosomiasis.

Animals↗
PubMed1987

Generation and functional analysis of T cell lines and clones specific for schistosomula released products (SRP-A).

Antigens present in the products released by the larval stage of schistosome (SRP-A) were shown to induce a strong cytotoxic and protective IgE response both in the rat and the monkey. T cell lines and clones specific for SRP-A or 26 kD antigens which are the main target of the cytotoxic IgE have been derived. The passive transfer of SRP-A specific T lymphocytes into infected rats led to an increase of the IgE response, conferring a significant level of protection to the rats. In coculture assays in vitro, these cell lines significantly enhanced the production of IgE by SRP-A sensitized rat spleen cells. This helper effect on the IgE response was confirmed with 26 kD T cell clone supernatants. Moreover, supernatants obtained after stimulation with phorbol myristate acetate were able to enhance the IgE production of a hybridoma B cell line (B48-14) producing a monoclonal IgE antibody, cytotoxic for the schistosomula.

Animals↗
PubMed1986

Role of serine proteases of Schistosoma mansoni in the regulation of IgE synthesis.

The regulation of the IgE response by schistosomula-released products (SRP) was studied either in vitro with rat and human cell cultures or in vivo by injection into rats of SRP with an unrelated allergen at primary or secondary immunization. The results obtained in vitro showed that non-dialysable factors present in SRP potentiate the IgE synthesis by rat and human cells. This enhancing effect was supported by molecules with serine protease activities. On the other hand, the inhibition or depletion of SRP in serine proteases induced a weak synthesis of IgM by rat cells in vitro. The injection of SRP into rats on day 0 with an unrelated allergen led to a potentiation of total IgE production, but an inhibition of specific IgE response. In contrast, a marked elevation of specific IgE response was obtained when SRP was injected upon secondary immunization. Serine proteases of SRP were partly responsible for this potentiative effect.

Animals↗
PubMed1986

Induction of a protective immune IgE response in rats by injection of defined antigens of schistosomulum-released products: immunochemical properties of the target antigens.

Brown Norway rats were injected without adjuvant with the soluble products liberated in a 16-hour culture by schistosomula (schistosomula-released products, SRP-A). A strong cytotoxic and protective IgE response was elicited, mainly directed against 22- and 26-kilodalton (kDa) SRP-A molecules. In the present study, we have attempted to characterize further those molecules. Metaperiodate denaturing treatment of the SRP-A glycans before injection into rats did not modify the immunogenicity of the SRP-A antigens. Results obtained by lectin affinity suggested that the 22- and 26-kDa molecules were glycoconjugates binding to ConA. Preparative sodium dodecylsulfate electrophoresis has allowed the separation of enriched fractions of 22- and 26-kDa molecules which have been injected separately into rats. The corresponding sera were tested in antibody-dependent cell cytotoxicity and displayed a significant cytotoxic IgE response (65 and 53%, respectively) towards the larvae. These results lend further support to the view that the 22- and 26-kDa antigens are the major targets of the protective IgE response and thus appear as potentially protective antigens.

Animals↗
PubMed1986

Protection against experimental Schistosoma mansoni schistosomiasis achieved by immunization with schistosomula released products antigens (SRP-A): role of IgE antibodies.

Schistosomula-released products (SRP-A) have been shown to induce preferentially a significant IgE response against Schistosoma mansoni schistosomula when injected into rats, in the absence of adjuvant. The present work provides additional evidence of the in vivo relevance of the anti-SRP-A target antigens. Two strains of rat (Brown Norway and Fischer) were immunized with SRP-A and infected percutaneously. A significant level of protection (up to 83% reduction in worm burden) was observed. Passive transfer experiments carried out with anti-SRP-A or IgE-depleted anti-SRP-A sera suggested the preponderant role of antibodies and particularly of IgE in the protective immunity developed by Fischer rats. Platelets and macrophages recovered from such immunized rats had surface IgE as demonstrated by immunofluorescence analysis with FITC anti-IgE, and have been shown to be directly cytotoxic for schistosomula. The chemiluminescence observed when the macrophages were incubated with anti-IgE suggested the presence of IgE on the surface of these cells.

Animals↗
PubMed1985

Defined antigens secreted by the larvae of schistosomes protect against schistosomiasis: induction of cytotoxic antibodies in the rat and the monkey.

The study of the immunology of schistosomiasis has allowed a clear understanding of the basic mechanisms of resistance, emphasizing the important role played by cellular and humoral factors. Whereas the production of polyclonal or monoclonal antibodies and the precise inventory of immune effector mechanisms in the rat and in man have led to the identification of potentially protective antigens, immunization with soluble schistosome components has not allowed a successful control of the destruction of schistosomula after infection. The experiments reported here show that schistosomulum-released products (SRP) were able to induce the production of antibodies, in the rat and the monkey, highly cytotoxic in antibody-dependent cellular cytotoxicity, using monocyte monolayers, platelets or eosinophils as effector cells. The immunization of rats with either total SRP or 25-30-kDa molecules purified from schistosomula conferred a significant protection towards a challenge infection by the parasite. IgE and to a lesser extent IgG antibodies represented the major humoral factors of cell activation leading to the schistosomulum killing when anti-SRP antisera, obtained after immunization of the monkey, were incubated with human effector cells.

Animals↗
PubMed1985

Translation of Schistosoma mansoni antigens in Xenopus oocytes microinjected with mRNA from adult worms.

Oocytes from Xenopus laevis microinjected with RNA isolated from Schistosoma mansoni adult worms translated antigens recognized by sera from infected rats, humans, and from immunized rabbits. The pattern of immunoprecipitated proteins analysed by SDS-polyacrylamide gel electrophoresis was species specific in rats. Serum from infected Fischer rats recognized antigens of 20, 27 and several bands in the 50-60 kDa range whereas serum from infected Brown Norway rats also immunoprecipitated major bands at 29, 43 and 100 kDa. Human infection sera gave a very variable pattern of immunoprecipitation not apparently dependent on the patients' age. At least 20 different antigenic species could be identified ranging from 14 to 150 kDa. Some S. mansoni antigenic proteins could be isolated from the membrane fraction of the oocytes whereas notably the 29 kDa band was present mainly in the soluble fraction. N-Glycosylation of S. mansoni antigens occurred as evidenced by the effects of tunicamycin treatment and concanavalin A binding. A multiple series of bands between 50 and 60 kDa, present in the membrane fraction, were glycosylated and secreted from the oocytes. Monoclonal antibodies to larval stage surface antigens failed to immunoprecipitate oocyte translation products, but sera absorbed with live schistosomula identified at least three putative surface antigens of 100, 43 and 29 kDa. However, the 29 kDa molecule was neither synthesized into membranes, nor secreted from oocytes.

Animals↗
PubMed1985

IgG response of rats and humans to the released products of schistosomula of Schistosoma mansoni.

The participation of products released from Schistosoma mansoni schistosomula (SRP-A) in the IgG antibody response of infected Brown-Norway rats and infected humans has been studied using immunoprecipitation with various antigenic preparations and in in vitro cytotoxicity assays. A large number of SRP-A molecules with a wide range of molecular weights was recognized by infected rat and human sera. Anti-SRP-A antibodies appeared in rat sera from day 28 after infection. In infected humans, a variable pattern of SRP-A recognition was observed between individuals. IgG antibodies obtained by immunization of rats with SRP-A without addition of adjuvants reacted with 3 major schistosomula surface proteins with molecular weights of 38, 32 and 21 kDa. These latter molecules were also revealed strongly by infected rat sera. Moreover, these antibodies were able to kill schistosomula in vitro in the presence of complement or eosinophils.

Animals↗
PubMed1984

Rat IgE directed against schistosomula-released products is cytotoxic for Schistosoma mansoni schistosomula in vitro.

The immunogenicity of molecules shed by schistosomula into culture medium (antigens present in schistosomula-released products, SRP-A) has been studied. The results obtained show that SRP-A preferentially induce an IgE response when injected into rats, without the need for adjuvants. Moreover, anti-SRP-A IgE is cytotoxic in vitro for the larvae in the presence of macrophages, eosinophils or platelets, which have previously been demonstrated as being the three efficient killer cells for schistosomula in the presence of specific IgE. Immunofluorescence analysis locates the target antigens at the schistosomulum surface. Among the antigens recognized by anti-SRP-A IgE, two molecules of 26 and 22 kDa have been identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by western blotting.

Animals↗
PubMed1984

Allergens of Schistosoma mansoni. II. Fractionation and characterization of S. mansoni egg allergens.

The interaction of Schistosoma mansoni crude soluble egg antigen (SEA) with IgE antibodies in sera from S. mansoni-infected mice, rats and humans has been studied by the radioallergosorbent test (RAST) and the Prausnitz-Küstner (PK) technique. IgE antibodies recognizing egg antigens were present as early as day 21 after the infection in the mouse sera and day 28 in rat sera. IgE in sera of infected humans reacted with antigenic components in the Mr range 70,000-150,000 and focusing as a broad peak in the pH range 4.5-6.5 as measured by RAST. SDS-PAGE followed by western blotting showed the presence of major components at molecular weights of 117,000 and 35,000-43,000. In the PK test, using mouse sera, components focusing in the alkaline pH range also gave a positive reaction. Most of the allergenic activity was bound by concanavalin A-Sepharose and by wheat germ agglutinin-Ultrogel. IgE in serum from an infected non-permissive host (the Fischer rat) apparently recognized egg-stage-specific allergen as indicated by differences in the time course of the IgE response to egg allergens compared to the adult material. When analyzed by SDS-PAGE and western blotting with day 45-infected rat serum, SEA showed some qualitative and quantitative differences to adult worm antigen. Molecules at molecular weights between 25,000 and 30,000 and at about 43,000 in SEA reacted with rat serum IgE and were absent from adult worm antigen. The allergenic similarities between egg and adult worm are discussed.

Allergens↗
PubMed1983

Allergens of Schistosoma mansoni. I. Comparison of the IgE response in human and experimental infections towards characterized allergens from adult worm products.

The reaction of adult worm products of Schistosoma mansoni with IgE antibodies in infected human and Fischer rat sera has been studied using the Prausnitz-Küstner test and the radioallergosorbent test. Incubation of worms in water released most of the soluble material reacting with both rat and human sera in the radioallergosorbent test. Sera from infected Fischer rats recognized a fraction with pI 4.9-5.2 separated by preparative isoelectric focusing throughout the time course of infection, whereas human sera reacted with material focusing between pI 4.4 and 6.0. A peak of allergenic activity with an apparent molecular weight between 70,000 and 150,000 was obtained by gel filtration. Human bilharzian sera also reacted with material in the molecular weight range 12,000-25,000. Allergenic material bound specifically to concanavalin A-Sepharose, Lens culinaris agglutinin-Ultrogel, and wheat germ agglutinin-Ultrogel, but substantial allergenic activity was also present in unbound fractions.

Allergens↗
PubMed1979

[Production of monoclonal anti-Schistosoma mansoni antibodies. Preliminary study of their biological activities].

Monoclonal antibodies against Schistosoma mansoni have been produced by fusion of splenic lymphocytes from S. mansoni infected Rats and P3-X63-Ag8 BALB/c cells. In vitro and in vivo studies of the biological activities of these antibodies have led to the identification of IgE antibodies with a high reaginic activity and antibodies which in a complement dependent or eosinophil dependent system were shown to have a marked cytotoxicity for schistosomula in vitro. This methodology seems to open new perspectives for the study of antibody function in immunity against parasites as well as for the isolation of the corresponding target antigens.

Animals↗
PubMed1978

Free and membrane-bound polysomes from rat liver. 1. Improvements of subcellular fractionation.

Substantial improvements of cellular fractionation in ionic conditions allowing preservation of polysome structure and polysome-membrane interactions are reported. They consist primarily in minimizing the lysosomal content of fractions containing endoplasmic reticulum by isolating a lysosome-rich fraction with little loss (6%) of RNA. Endoplasmic reticulum membranes were recovered in high yield, mainly in association with mitochondria, the remainder being found in the post-lysosomal supernatant. The latter also contained practically all the free polysomes, as judged by metrizamide gradient analyses. The distributions of various constituents (RNA, DNA, protein and marker enzymes) among cell fractions is presented.

Animals↗
PubMed1978

Free and membrane-bound polysomes from rat liver. 2. Recovery of large free and membrane-bound polysomes.

Techniques allowing the recovery of large free and membrane-bound polysomes in high yield are reported. Subcellular fractions were prepared from rat liver homogenates as described in the preceding paper. Purified microsomal membranes (obtained from the post-lysosomal supernatant) were adjusted to 50 mM Mg(CH3COO)2 and treated with 2% Triton X-100 and 0.3% sodium deoxycholate in the presence of yeast RNA and cell sap, and polysomes were purified by overnight centrifugation through low-ionic-strength discontinuous sucrose gradients containing 2 mg/ml of cell sap proteins. Polysomes were isolated from the mitochondria/endoplasmic reticulum complex (fraction C) by treatment with 2% Triton X-100 and 0.5% sodium deoxycholate in the presence of 50 mM Tris-HCl, pH 7.6, 0.1 M KCl, 0.15 M NH4Cl and 50 mM Mg(CH3COO)2 and purified through sucrose layers of decreasing ionic strength containing 2 mg/ml of cell sap proteins. Analyses of polysomes in isokinetic sucrose gradients showed that the free polysome fraction and both membrane-bound polysome fractions had 14-15 ribosomes per mRNA at the maximum of absorbance. Experiments from which these methods were derived are described.

Animals↗
PubMed1976

The use of metrizamide as a density-gradient medium in studies of rat-liver polysomes.

The behaviour of rat liver cytoplasmic ribonucleoproteins in metrizamide has been studied to determine whether the iodinated compound would offer any advantage over other centrifugation media for studies of polysome structure and function. 1. Polysomes had a density of 1.295--1.300 g/cm3 in metrizamide gradients which was also the density of glycogen. However, the polysaccharide reached its equilibrium more rapidly than the polysomes. Thus a short centrifugation of a polysome suspension from non-starved rats over a 40% metrizamide cushion was sufficient to eliminate more than 85% of the glycogen with a polysome yield of about 75%. 2. Ribosomal subunits had neighbouring densities (1.23 and 1.20 g/cm3 for large and small EDTA-derived subunits; 1.23 and 1.21 g/cm3 for large and small KCl/puromycin-derived subunits, respectively). Polysomal messenger ribonucleoproteins were heterogeneously distributed (phi = 1.12 to 1.23 g/cm3) and overlapped with subunits in a similar manner as in sucrose gradients. 3. Analysis of a post-mitochondrial supernatant in metrizamide showed a clear separation of free polysomes, rough membranes and the soluble phase.

Animals↗