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Biomedical subjects

A Capron

Publications and source records attributed to A Capron.

At least 91 records · Page 5Linked to original sources
PubMed1996

Synthesis of type 1 (IFN gamma) and type 2 (IL-4, IL-5, and IL-10) cytokines by human eosinophils.

Eosinophils are not only the source of cytotoxic and proinflammatory mediators but they can also generate cytokines and growth factors, including their own factors of differentiation, namely IL-3, GM-CSF, and IL-5. Synthesis of IL-5 by eosinophils was demonstrated by in situ hybridization and immunostaining in a variety of diseases, such as coeliac disease, asthma, hypereosinophilic syndrome, or skin diseases. However, IL-5 synthesis by eosinophils was not shown in Crohn's disease, whereas in other diseases, it was restricted to a subpopulation of eosinophils, suggesting some heterogeneity in cytokine-producing eosinophils. Here, we report that human eosinophils, in addition to the synthesis of IL-5, and Th2 cytokine, can synthesize IFN gamma, a Th1 cytokine, as well as IL-10 and IL-4, known to be mainly produced by Th2 cells. Double immunostaining procedures reveal the coexpression of IL-5, IL-4, and IL-10 by the same eosinophil populations, different from IFN gamma-producing eosinophils. We propose that distinct subpopulations of human eosinophils express Th2 or Th1 cytokines. These results point to the importance of cytokines derived from non T cells in the regulation of the immune response.

Eosinophils↗
PubMed1996

Induction of mucosal immune responses against a heterologous antigen fused to filamentous hemagglutinin after intranasal immunization with recombinant Bordetella pertussis.

Live vaccine vectors are usually very effective and generally elicit immune responses of higher magnitude and longer duration than nonliving vectors. Consequently, much attention has been turned to the engineering of oral pathogens for the delivery of foreign antigens to the gut-associated lymphoid tissues. However, no bacterial vector has yet been designed to specifically take advantage of the nasal route of mucosal vaccination. Herein we describe a genetic system for the expression of heterologous antigens fused to the filamentous hemagglutinin (FHA) in Bordetella pertussis. The Schistosoma mansoni glutathione S-transferase (Sm28GST) fused to FHA was detected at the cell surface and in the culture supernatants of recombinant B. pertussis. The mouse colonization capacity and autoagglutination of the recombinant microorganism were indistinguishable from those of the wild-type strain. In addition, and in contrast to the wild-type strain, a single intranasal administration of the recombinant strain induced both IgA and IgG antibodies against Sm28GST and against FHA in the bronchoalveolar lavage fluids. No anti-Sm28GST antibodies were detected in the serum, strongly suggesting that the observed immune response was of mucosal origin. This demonstrates, to our knowledge, for the first time that recombinant respiratory pathogens can induce mucosal immune responses against heterologous antigens, and this may constitute a first step toward the development of combined live vaccines administrable via the respiratory route.

Adhesins, Bacterial↗
PubMed1996

Neutralizing antibody responses elicited in mice immunized with recombinant bacillus Calmette-Guérin producing the Schistosoma mansoni glutathione S-transferase.

Schistosomiasis is a group of severe parasitic diseases, in humans and domestic animals, that are especially of importance in the developing world. No efficacious vaccine is currently available. However, Ab-mediated immune responses against the 28-kDa glutathione S-transferase of Schistosoma mansoni (Sm28GST) appear to be involved in protection. This Ag was produced in recombinant Mycobacterium bovis bacillus Calmette-Guérin (BCG). The recombinant protein bound glutathione and expressed enzymatic activity, indicating that the active site of Sm28GST was folded properly. Single i.v., i.p., s.c., or intranasal immunizations with rBCG in BALB/c mice resulted in significant anti-SM28GST Ab responses, which were enhanced by a booster dose. The Ab responses remained high for at least 1 yr after immunization. Analyses of the isotype profiles indicated that i.v. immunized mice produced high titers of anti-Sm28GST IgG2a, and less IgG2b and IgG1. Mice immunized by the s.c. route initially also produced high levels of IgG2a and low titers of IgG1 and IgG2b, but the titers of the latter two isotypes increased gradually thereafter, tending toward a mixed profile. Intraperitoneal immunization provided a mixed profile directly after the first administration. High titers of anti-Sm28GST Abs also corresponded to high levels of neutralization of the enzymatic activity. These results indicate that rBCG induces strong IgG1, IgG2a, and IgG2b, and neutralizing Ab responses against Sm28GST, which has been found to correlate with protection against S. mansoni in humans.

Animals↗
PubMed1996

Eosinophils express a functional receptor for interferon alpha: inhibitory role of interferon alpha on the release of mediators.

Recent reports describe the beneficial use of alpha interferon (IFNalpha) for the treatment of idiopathic hypereosinophilic syndrome (HES) unresponsive to conventional therapy. A clinical improvement associated with a rapid decrease of peripheral blood eosinophilia suggested possible direct effects of IFNalpha on eosinophils through the presence of IFNalpha receptors (IFNalphaR). Reverse transcriptase-polymerase chain reaction (RT-PCR) and cytochemistry were used respectively to detect the presence and define the distribution of IFNalphaR on enriched eosinophil preparations purified from blood cells. IFNalphaR was found on eosinophils collected from patients with various eosinophilic disorders. In addition, IFNalpha inhibited the release of eosinophil granule proteins such as eosinophil cationic protein (ECP), neurotoxin (EDN, or interleukin-5 (IL-5). Moreover, antiparasite cytotoxicity was also strongly reduced in a dose-dependent manner by IFNalpha. These results provide the first evidence that human eosinophils express a functional receptor for IFNalpha and represent a potential basis for the beneficial effects of IFNalpha in patients with hypereosinophilic syndromes.

Animals↗
PubMed1996

Tissue localization and stage-specific expression of the phospholipid hydroperoxide glutathione peroxidase of Schistosoma mansoni.

The tissue localization and the stage-specific expression of the phospholipid hydroperoxide glutathione peroxidase of Schistosoma mansoni (SmPHGSHpx) have been determined. An antiserum raised against the C-terminal region of the predicted protein sequence was used for immunocytochemical investigations. The native protein is expressed only in female and egg vitelline cells and is practically absent from male worm tissue. Western blot data confirmed these results and showed the complete absence of SmPHGSHpx from cercariae. However, Northern blotting indicated the presence of the corresponding mRNA at all life-cycle stages investigated. The sequence determination of the 5' flanking region of the SmPHGSHpx gene revealed the presence of an extended TATA box (5'-TAAATA-3') at -32, a possible CAAT box at -75 and a putative monomeric estrogen response element 5'-GGTCAA-3' at position -486. In addition, direct and inverted repeat elements are present.

Amino Acid Sequence↗
PubMed1996

Cloning of Schistosoma mansoni transcription factor NF-YA subunit: phylogenic conservation of the HAP-2 homology domain.

The CCAAT-binding factor NF-Y (CBF/CP1) is a heteromeric transcription factor involved in the regulation of a variety of eukaryotic genes. We identified NF-Y as the CCAAT activity binding to the promoter region of the gene coding for the 28-kDa glutathione S-transferase of the human parasite Schistosoma mansoni (Sm28GST). We isolated the NF-YA cDNA from S. mansoni (SmNF-YA): the complete 268 amino acid sequence harbors a region in its C-terminal part that shows homology with the subunit interaction and DNA-binding domains of the mammalian NF-YA; the N-terminal region has an amino acid composition reminiscent of the mammalian and echinoderm counterparts, rich in glutamine and hydrophobic residues, but shows no sequence similarity at the primary level. In vitro synthesized SMNF-YA is able to associate with mammalian NF-YB/C subunits in the absence of DNA and to bind to the Sm28GST CCAAT box. Surprisingly, a monoclonal antibody directed against the non-conserved Q-rich activation domain of mammalian NF-YA supershifts and immunoprecipitates SMNF-YA, strongly suggesting structure conservation in the activation domain between divergent species.

Amino Acid Sequence↗
PubMed1996

Mucosal vaccination against schistosomiasis using liposome-associated Sm 28 kDa glutathione S-transferase.

A variety of experimental models have shown that immunization using the glutathione S-transferase from Schistosoma mansoni (Sm28GST) can induce protective immunity against this parasite. This immunity has been related to the production of Th2 type antibodies against the antigen in both mice and humans. The work presented in this paper describes the development of a mucosal immunization protocol using liposomes which is designed to promote production of specific antibodies of isotypes related to a Th2 immune response. The liposomes were multilamellar and composed of various synthetic phospholipid mixtures. The liposome vector was used to convey the Sm28GST antigen to gut associated lymphoid tissue. The association of the Sm28GST antigen with liposomes containing different lipid mixtures was initially studied. The degree of interaction of the antigen was found to increase with the hydrocarbon chain length of the lipids used. It was demonstrated that the protein was present on both the inner and the outer membranes of the liposome vesicles. It was also shown that the major epitopes of Sm28GST were accessible to specific antibodies, confirming a conservation of its main antigenic features. Additionally, enzymatic activity of the protein/liposome complex was also demonstrated, indicating a conservation of the tertiary structure of the protein. An optimal Sm28GST/ liposome complex was established and administered orally to mice. This treatment resulted in both a mucosal and systemic immune response to the antigen Sm28GST. This was demonstrated by the detection of specific IgA in gut washes and specific IgG1, IgG2b in sera. Immunization by Sm28GST/liposome complex followed by challenge with parasite showed that Sm28GST given orally in these conditions bore protective activity. This last result opens the possibility of mucosal vaccination against schistosomiasis.

Administration, Oral↗
PubMed1996

Ultrastructural localization of Sm28 GST protective antigen in Schistosoma mansoni adult worms.

The localization of the 28 kDa Schistosoma mansoni glutathione S-transferase (Sm28 GST) has been investigated using immunohistochemistry and electron microscopy and the results compared with previously published data. This study confirms the wide distribution of this antigen in the parasite. In male and female worms, Sm28 GST is localized in the tegument, the parenchyma, the oesophageal epithelium and in genital organs. Sm28 GST was clearly detected in germinal and sustentacular cells. The decrease of staining intensity during the differentiation of germinal cells suggests a down-regulated expression of the molecule. At the ultrastructural level, this antigen was abundant in nuclei and less present in the cytoplasm. The marked heterogeneity observed in the staining of individual worms indicates that Sm28 GST seems to be closely associated with the parasite's metabolism. The results are discussed in relation to the biological and protective functions of the protein.

Animals↗
PubMed1996

Schistosoma mansoni elastase: an immune target regulated during the parasite life-cycle.

Recombinant Schistosoma mansoni elastase was expressed in Escherichia coli and an antiserum raised against the recombinant protein was used to investigate stage-specific control of elastase in the parasite, and to determine whether the enzyme could form the basis of a strategy to prevent larval invasion of the host. Results showed that the expression of elastase is developmentally regulated, even if the basal promoter activity does not seem to be stage specific. The analysis of mRNA expression showed the presence of elastase transcript in adult worms although we could not detect the protein at this stage, suggesting that S. mansoni employs a form of translational control. The measurement of elastase levels in supernatants of culture schistosomula combined with the localization of elastase in cercarieae invading mouse skin showed that the enzyme is heavily released during penetration. Finally, we studied the cytotoxic activity of rat anti-elastase sera, and the analysis of the isotypic profile suggested that IgG2a anti-elastase may be responsible for the cytotoxic effect.

Animals↗
PubMed1996

Expression of NF-Y nuclear factor in Schistosoma mansoni.

The A subunit of NF-Y nuclear factor from Schistosoma mansoni was expressed in E. coli fused to a histidine tag and purified by affinity chromatography using a Ni(2+)-Agarose matrix. Antibodies against the recombinant protein were prepared and used for Western blot and immunolocalization. The presence of SMNF-YA in all stages of the parasite life-cycle was determined by RT-PCR and Western blot analysis. The immunolocalization of SMNF-YA showed the presence of this factor in a parenchymal cell population of cercariae and adult worms and in embryos within eggs. The expression of SMNF-YA was demonstrated to decrease in maturating spermatozoites whereas an accumulation of this factor was observed in the nucleus from oocytes during their maturation processes.

Animals↗
PubMed1996

Selective CD4+ T cell deletion after specific activation in HIV-infected individuals; protection by anti-CD28 monoclonal antibodies.

AIDS is characterized by a progressive decline in the number of CD4+ T cells. This is preceded by an early selective defect in the proliferation of these cells to recall antigens [1-3], pokeweed mitogen (PWM) [4-6] and to superantigens (SAg) [4,7]. In contrast, the proliferative response to phytohaemagglutinin (PHA) remains intact [1,2,5]. We and others have shown that the proliferative defect in response to some stimuli was in fact due to the induction of cell death [4,7]. The activation-induced cell death mechanism that explains the proliferative defects observed in vitro might also account for the progressive in vivo deletion of CD4+ T cells. Indeed, studies performed on different models of primates have shown that induction of cell death in CD4+ T cells was detected only when T cells were isolated from animals infected with a type of retrovirus that induces an AIDS-like disease [8]. This correlation prompted us to analyse further the mechanism of HIV-induced activation cell death to determine the specificity and rate of induction of cell death. T cells from HIV-infected individuals were activated with superantigens and the V beta T cell receptor (TCR) expression analysed. Data presented here show that cell death is restricted to activated CD4+ T cells, and does not affect bystander cells. More importantly, addition of anti-CD28 MoAb specifically inhibited the induction of apoptosis, raising possibilities for therapy.

Antibodies, Monoclonal↗
PubMed1996

Common cis-acting elements critical for the expression of several genes of Toxoplasma gondii.

Transient transformation of Toxoplasma using the CAT (chloramphenicol acetyl transferase) reporter gene has been used to map promoter elements of four genes encoding dense granule proteins (GRA1, GRA2, GRA5 and GRA6). Intense CAT activities (GRA1 > GRA5 > GRA2 > GRA6) are detected for constructs containing 379bp, 276bp, 209bp and 265bp upstream of the transcription start site of the GRA1, GRA2, GRA5 and GRA6 genes, respectively. Deletion analysis shows that optimal promoter activity of each gene is contained in the proximal region of the transcription start site: -129 to -47 for GRA1, -87 to -37 for GRA2, -156 to -30 for GRA5 and -146 to -27 for GRA6. Quantitative CAT assay and mutation analysis show that repeated motifs (A/TGAGACG) found in either orientation with respect to transcription are critical elements of these defined promoter regions. We have found such sequence elements in the upstream region of other Toxoplasma genes such as Tub1 and within the stretch of 27bp repeats of the SAG1 promoter.

Animals↗
PubMed1996

Induction of cytotoxic T-cell activity by the protective antigen of Schistosoma mansoni Sm28GST or its derived C-terminal lipopeptide.

In a previous work the authors demonstrated that immunization with Schistosoma mansoni 28-kDa glutathione-S-transferase (Sm28GST) was able to reduce hepatic damage in infected mice and that the adoptive transfer of Sm28GST-specific T cells reproduced the protective effect obtained with the recombinant molecule. In the present paper, the authors show that Sm28GST is also able to stimulate an antigen-specific, cytotoxic T-cell response against Sm28GST-pulsed P815 target cells in normal mice and that effector cells induced in vivo were classical Class I MHC-restricted CD8+ lymphocytes. The authors found no spontaneous CTL activity against Sm28GST-pulsed target cells during the course of the infection by S. mansoni although Sm28GST is expressed at different developmental stages of the parasite. It was observed, however, that immunization with Sm28GST is sufficient to elicit a significant level of CTL response for 6 weeks in infected mice. The role of these Class I MHC-restricted CD8+ lymphocytes in the protection observed precisely at the same period in immunized mice remains to be elucidated. The authors also observe that immunization with the lipopeptide form of the C-terminal peptide of the molecule (190-211 peptide) led to a CTL activation comparable to that observed after immunization with the whole molecule demonstrating the feasibility of using a synthetic lipopeptide as immunogen for a CTL response against Sm28GST epitopes. Moreover, like Sm28GST-specific CTLs, 190-211 lipopeptide-specific cells were also Class I MHC-restricted lymphocytes.

Amino Acid Sequence↗
PubMed1996

Immunoglobulin A response in murine schistosomiasis: stimulatory role of egg antigens.

The immunoglobulin G (IgG) and IgA antibody responses to different Schistosoma mansoni antigens have been determined in chronically infected mice as well as in unisexually infected animals. With a panel of enzyme-linked immunosorbent assays (ELISAs), soluble antigens from furcocercariae, adult worms, and eggs were probed with sera collected at 3-week intervals. Bisexually infected animals developed significant IgG and IgA antibody responses to the antigens tested, which increased after egg deposition. In unisexual infections no significant differences were recorded in the IgG antibody profile for furocercaria and adult worm antigens, whereas the IgA antibody response was impaired. Both the IgA and IgG antibody responses toward egg antigens were reduced compared with those in a bisexual infection. Furthermore, a specific mucosal IgA antibody response was observed only in the bisexually infected animals. Histological analysis performed on bisexually infected mice led to the observation of eggs and granulomatous lesions within the Peyer's patch follicles, which are essential sites for the induction of mucosal immunity in the intestine. These data suggest a relationship between egg deposition and the induction of the IgA antibody response toward schistosomes.

Animals↗
PubMed1996

Induction by interferons of human eosinophil apoptosis and regulation by interleukin-3, granulocyte/macrophage-colony stimulating factor and interleukin-5.

The effects of recombinant human interferon alpha (rhIFN-alpha) and interferon gamma (rhIFN-gamma) were examined on the apoptosis of human cord blood derived eosinophils, obtained after 4 weeks of culture with recombinant human interleukin-3 (rhIL-3), granulocyte-macrophage-colony stimulating factor (rhGM-CSF) and interleukin-5 (rhIL-5). Eosinophil viability decreased remarkably after 1 week culture with rhIFN-alpha and rhIFN-gamma. Recombinant rhIFN-alpha also decreased the viability of co-existing monocytes/macrophages, whereas in contrast, rhIFN-gamma increased the percentage of viable monocytes/macrophages. There was no synergistic or additional effect of rhIFN-alpha and rhIFN-gamma on eosinophil viability. Apoptotic eosinophils, detected by their morphological characteristics, or by DNA nick end labeling in situ, increased remarkably after incubation with rhIFN-alpha and increased to a lesser extent with rhIFN-gamma. The numbers of eosinophil-phagocytosing macrophages increased after culture with rhIFN-alpha and also with rhIFN-gamma. In contrast, eosinophilopoietic cytokines such as rhIL-3, rhIL-5 and specially rhGM-CSF, significantly increased eosinophil viability, and partially rescued the effects of rhIFNs. They also decreased apoptotic eosinophil numbers and eosinophil-phagocytosing macrophage numbers. These results indicate that eosinophil viability, at least in vitro, can be differentially regulated by cytokines produced during the immune response.

Apoptosis↗
PubMed1996

[Value of hepatosplenic ultrasonography in the surveillance of Schistosoma mansoni endemics (a study conducted in the Richard Toll region of Senegal)].

Abdominal ultrasound is a reliable and reproducible technique for monitoring the progression of hepatosplenic schistomiasis. It was used in the framework of the @Hope" program against endemic Schistosoma mansoni in the Senegal River region. A total of 166 patients presenting Schistosoma mansoni eggs in stools were divided into age groups with a sex ratio of 1. All patients underwent the same ultrasound examination including measurement of the liver and assessment of the branches of the portal vein system. Our findings indicated that highly sensitive hypertrophy of the left lobe of the liver occurs early since this feature was observed in all patients over the age of 15 years. Alterations of the portal system were observed in 73% of patients but were moderate, stage 1, in the zone where incidence of positive stools is over 90%. Grade III lesions were only found in patients over 23 years of age. Although these lesions accounted for 4% of the cases, this finding underscores the need for surveillance in a region where infestation became endemic less then ten years ago raising fears that severe schistosomal portal hypertension would become widespread. A mobile ultrasonographic surveillance unit would be useful in the region.

Adolescent↗