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A Capron

Publications and source records attributed to A Capron.

At least 145 records · Page 8Linked to original sources
PubMed1994

Analysis of the V beta specificity of superantigen activation with a rapid and sensitive method using RT PCR and an automatic DNA analyser.

Polymerase chain reaction (PCR) by the specific amplification of a DNA target sequence has been shown to permit analysis of T cell receptor usage. The complete repertoire is amplified using oligonucleotide primers specific for each of the known V alpha or V beta regions of the T cell receptor. One of the methods currently used to appreciate the relative quantity of different V chains of the TCR is by coamplifying in the same reaction tube the variable region of one chain together with the constant region of the other chain. We have optimised PCR conditions and analysed PCR products on an automatic DNA analyser facilitating the quantification of the amplified products, avoiding the use of radioisotopes, and allowing the determination of the sizes of CDR3 regions, thus giving new information on the modification of the T cell repertoire. This method was used to analyse the precise V beta specificity of the T cell activation with the superantigen SEB.

Autoanalysis↗
PubMed1994

Interleukin 5 synthesis by eosinophils: association with granules and immunoglobulin-dependent secretion.

Interleukin 5 (IL-5) is the main factor that promotes the terminal differentiation of eosinophil progenitors (as indicated by colony formation assays), and enhances the effector capacity of mature eosinophils. IL-5 is produced by T lymphocytes, CD4-/CD8- and mast cells and recently, messenger (m)RNA of this cytokine has been identified in eosinophils from patients with coeliac disease, asthma, or eosinophilic heart diseases. In this study, IL-5 mRNA and immunoreactive IL-5 protein were detected in tissue and blood eosinophils from patients with eosinophilic cystitis or hypereosinophilic syndromes but not in Crohn's disease. By electron microscopy associated to immunogold staining, immunoreactive IL-5 was identified in eosinophilic granules. After stimulation with IgA-, IgE-, or IgG-immune complexes, blood eosinophils were shown, by immunocytochemistry and by enzyme-linked immunosorbent assay, to secrete IL-5. These observations demonstrate that eosinophils, under physiological stimulation, can release significant amounts of IL-5, which may contribute to local eosinophil recruitment and activation.

Cytoplasmic Granules↗
PubMed1994

Cloning and characterization of the gene encoding Schistosoma mansoni glutathione peroxidase.

Antioxidant enzymes are thought to play a crucial role in the survival of the parasite, Schistosoma mansoni, during its migration through the tissues of the definitive host. We recently cloned the cDNA encoding one such enzyme, glutathione peroxidase (Gpx). In order to elucidate the regulation of expression of this gene, we describe the cloning and characterization of a Gpx gene of S. mansoni. An initial screen of a lambda EMBL4 genomic library using the corresponding cDNA sequence as a probe yielded 14 positive clones, two of which have so far been analyzed in detail. The complete Gpx gene contains five introns, four of which, located at the 5' end, are extremely short (30-51 bp) and the last of which is approximately 6 kb long. We present the sequence of the gene including 73 bp at the 5' end, the complete sequence to 137 bp downstream from the penultimate exon, 164 bp upstream and 131 bp downstream from the last 3' exon. The potential mRNA cap site is situated 219 bp upstream from the ATG start codon. All intron/exon junctions correspond to the conventional eukaryotic splice signal. Analysis of the 5' flanking region revealed the presence of a potential TATA box at--26 bp from the cap site, but no CAAT-like element is present. Southern blot analysis showed a unique Gpx gene organisation in the S. mansoni genome.

Amino Acid Sequence↗
PubMed1994

High-affinity IgE receptor on eosinophils is involved in defence against parasites.

Parasitic infections are often associated with eosinophilia and high levels of immunoglobulin E (IgE). This observation has led to speculation that eosinophils and IgE may act together in the immune response against parasites. In support of this hypothesis, IgE and eosinophils participate in cytotoxic reactions directed against Schistosoma mansoni larvae in vitro. Furthermore, epidemiological studies have shown an inverse correlation between levels of specific IgE and rates of infection with Schistosoma. The low-affinity IgE receptor (Fc epsilon RII/CD23) was first incriminated in eosinophil activation. The fact that the high-affinity IgE receptor (Fc epsilon RI) is not only expressed on mast cells and basophils but also on Langerhans cells led us to investigate the presence of Fc epsilon RI on eosinophils. Here we show that Fc epsilon RI is expressed on eosinophils from hypereosinophilic patients, is involved in eosinophil degranulation, and participates in eosinophil-mediated cytotoxicity against S. mansoni. Our results indicate that Fc epsilon RI may play a major part in immune defence against parasites.

Animals↗
PubMed1994

The mixotope: a combinatorial peptide library as a T cell and B cell immunogen.

We report a new approach in peptide vaccine strategy based on combinatorial synthesis. A library of 7.5 x 10(5) related peptides, termed mixotope, was derived from the sequence of the third hypervariable domain (V3 loop) of the human immunodeficiency virus (HIV) envelope protein. This preparation induced a strong immune response in all syngeneic and outbred rodents tested. The response directed against the mixotope included antibodies, CD4+ T helper cells (TH1 and TH2) and CD8+ T cells. In rodents immunized with the mixotope, the T cell response directed against individual V3 peptide sequences (BRU, MN, RF, SF2, and ELI) as measured by T cell proliferation and interleukin (IL)-2 production, was found to be major histocompatibility complex haplotype-dependent. However, additional experiments performed in mice indicated that selectivity was less restrictive when using IL-3 secretion to explore T cell activation. This combinatorial antigen could be considered as a series of agretopic motifs framing a multiplicity of closely related epitopes for T cell recognition and able to elicit a T cell and B cell repertoire. This new construct may therefore provide a basis for the design of future vaccine strategies.

AIDS Vaccines↗
PubMed1994

Antigenicity and immunogenicity of P30-derived peptides in experimental models of toxoplasmosis.

P30, also referred to as SAG-1, is now recognized as a major Toxoplasma gondii antigen potentially important for both diagnosis and immunoprophylaxis of toxoplasmosis. By using predictive algorithms, five synthetic peptides (48-67, 82-102, 213-230, 238-256 and 279-285) derived from P30, were investigated for B- and T-cell determinants in mouse and rat experimental models. Antibody recognition appeared more broadly distributed along the P30 sequence, whereas T-cell recognition was mainly targeted on the 238-256 peptide. In the absence of any carrier protein, this peptide induced a B- and T-cell immune response independent of the route of immunization (oral route or subcutaneous injection). This peptide (238-256) induced multiple antibody isotypes. In contrast with the 238-256 peptide, the 48-67 peptide, either free or in the form of a multiple antigenic peptide (MAP) construct or the 279-295 peptide, elicited antibodies associated with a TH2 response. This study reports for the first time the analysis of the antigenic and immunogenic properties of P30-derived peptides and are potentially useful for vaccinal strategies incorporating the P30 Toxoplasma gondii antigen.

Administration, Oral↗
PubMed1994

Evaluation of the effect of Sm28GST-derived peptides in murine hepatosplenic schistosomiasis: interest of the lipopeptidic form of the C-terminal peptide.

Among the synthetic peptides derived from the 28-kDa Schistosoma mansoni glutathione S-transferase (Sm28GST), immunization with the C-terminal peptide comprising amino acid residues 190-211 induced a reduction in splenomegaly, in the number of hepatic eggs and in hepatic fibrosis in mice infected by Schistosoma mansoni. The absence of antibodies specific for the Sm28GST or for the 190-211 peptide observed in our conditions of immunization with this peptide argued in favour of the involvement of cellular-dependent mechanisms in the reduction in hepatic pathology. This was confirmed by the passive transfer of 190-211 peptide-specific T-cell enriched spleen cells which reproduced the protective effect conferred by immunization with the 190-211 peptide. These 190-211 peptide-specific cells produced little IL4 and high levels of IFN-gamma, a potent inhibitor of collagen synthesis. Furthermore, the use of a lipopeptidic form of the 190-211 peptide significantly improved the reduction in hepatic pathology obtained with the uncoupled peptide and induced a durable protective response. These results provide encouraging information for the possible use of synthetic peptides in the immunoprophylaxis of Schistosomiasis.

Amino Acid Sequence↗
PubMed1994

Trypanosoma cruzi cDNA encodes a tandemly repeated domain structure characteristic of small stress proteins and glutathione S-transferases.

The isolation, characterization, and expression of a novel cDNA encoding a Trypanosoma cruzi polypeptide (TcAc2), homologous to various small stress proteins and glutathione S-transferases, are described. The deduced amino-acid sequence revealed two domains sharing 27% identity and an additional 27% similarity to each other suggesting that the molecule may have evolved from a single domain by a process of gene duplication and fusion. The TcAc2 cDNA was subcloned into the pGEX-2T vector for expression in E coli. In vitro translation products of epimastigote mRNA, immunoprecipitated with anti-TXepi serum, showed a major radioactive band of 52 kDa. Immunoprecipitation of [35S]methionine labelled epimastigote and trypomastigote antigens after pulse chase experiments, using anti-TcAc2 fusion protein antibodies, showed that the protein is released into the culture medium. Moreover, Western blot analysis revealed a single band of 52 kDa with epimastigote, trypomastigote and amastigote antigens. Primary structure homology searches revealed that each TcAc2 domain contained within its N-terminus significant homology to Solanum tuberosum pathogenesis-related protein PR1, soybean heat shock protein 26-A, auxin regulated clone pCNT103 from Nicotiana tabacum and Drosophila melanogaster glutathione S-transferase 27 (GST27). This finding was supported by a comparison of hydrophobicity profiles of TcAc2 and these proteins. Most of them play a central role in protection mechanisms against stress. Based on the homology between TcAc2, glutathione S-transferases (GST) and small stress proteins, it is likely that the TcAc2 gene product may play a crucial role in parasite's adaptation to its microenvironment. These molecules could be considered as members of the GST superfamily, where the T cruzi protein may take a particular place because of its internal gene duplication.

Amino Acid Sequence↗
PubMed1994

Molecular and immunological characterization of a Trypanosoma cruzi protein homologous to mammalian elongation factor 1 gamma.

In previous studies, we reported the characterization of three Trypanosoma cruzi proteins with molecular masses of 45, 30 and 25 kDa eluted from a glutathione agarose column (these proteins were named TcGBP). Using antibodies against TcGBP native proteins we could isolate from a lambda ZAPII epimastigote cDNA library cDNA clones encoding the 30 and 25 kDa proteins. Comparison of the two sequences with amino acid sequences in several data banks revealed that both protein sequences were highly homologous to human and Artemia salina elongation factor 1 beta. Thus, the proteins were named TcEF-1 beta 25 and TcEF-1 beta 30. In the present study we used a double immunoscreening strategy that allowed us to isolate a cDNA clone corresponding to the 45 kDa protein. The protein sequence revealed 31% identity and 61% homology with human and Artemia salina EF1 gamma and therefore was named TcEF-1 gamma. Moreover, three putative phosphorylation sites at position 51 (CSPC), at position 90 (RTPL) and at position 265 (PSPF) were found in the TcEF-1 gamma sequence. These sites are compatible with the notion that TcEF-1 gamma could be the target of phosphorylation by protein kinase(s). Random primed cDNA hybridized with a single 1.4 kb mRNA found in epimastigote, trypomastigote and amastigote forms. In addition, Southern blot analysis of genomic DNA suggested that the protein is encoded by a single gene. The TcEF-1 gamma cDNA was subcloned into the pGEX-4T-3 vector for expression in Escherichia coli.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Effect of a lipopeptidic formulation on macrophage activation and peptide presentation to T cells.

We studied a 45-69 lipopeptide obtained by N-terminal modification with a N epsilon-palmitoyl lysine residue of the 45-69 peptide derived from the nef protein of HIV. T cells from animals immunized intraperitoneally with 45-69 lipopeptide proliferated in vitro in the presence of 45-69 peptide while no response was obtained after intraperitoneal immunization with 45-69 peptide. The efficiency of the 45-69 lipopeptide is supported by the covalent association to the N epsilon-palmitoyl lysine moiety. The immunogenicity of the 45-69 lipopeptide or of the unmodified peptide is dependent on the route of immunization but is not related to a mitogenic effect on cells or to an increase of the peptide antigenicity. Moreover, only 45-69 lipopeptide induces the secretion of cytokines such as IL-1, IL-6 and TNF-alpha by peritoneal macrophages. Finally, the use of 45-69 lipopeptide permits the activation of highly purified T cells without the addition of antigen-presenting cells. These results have implications for the formulation of synthetic vaccines.

Amino Acid Sequence↗
PubMed1994

Pathology of Toxoplasma gondii infection in the nude rat. An experimental model of toxoplasmosis in the immunocompromised host?

Genetically athymic nu/nu (nude) rats, deficient in T cells, die from infection with various Toxoplasma gondii strains, including RH and Prugniaud strains. In contrast, these strains cause chronic infections without apparent symptoms in immunocompetent non-nude rats. We show here that nude rats die in two to three weeks after RH infection and three to four weeks after Prugniaud infection. Histological examination of brains from nude rats at different time points after infection, revealed an absence of lesions after RH strain infection and cysts with usually no inflammation after Prugniaud infection. Lungs from nude rats developed a fibrin alveolitis using either strain, whereas myocarditis with focal areas of necrosis were observed only after Prugniaud infection. Cysts and, in some cases, tachyzoites in the necrotic lesions were easily identifiable. The two strains of T. gondii elicited in nude rats a granulomatous hepatitis that only differed in intensity. Spleen and mesenteric lymph nodes appeared totally non reactive in both cases. This model allows immunological and parasitological studies by comparison with immunocompetent rat infection. Published data concerning toxoplasma pathology in AIDS, therefore, suggest that acute toxoplasma infection in nude rats may be a useful model for studying disseminated forms of toxoplasma infection found in AIDS patients.

Animals↗
PubMed1994

Tissue expression of the Schistosoma mansoni 28 kDa glutathione S-transferase.

The expression of the Schistosoma mansoni 28 kDa glutathione S-transferase (Sm28) was studied using molecular (PCR, in situ hybridization), and immunocytochemical techniques. The presence of Sm28 was demonstrated in all developmental stages of the parasite except the intra-uterine immature egg. In the parenchyma of male and female adult worms the distribution of Sm28 was limited to a subpopulation of parenchymal cells and to the dorsal tubercles of the male. The tegument, the muscles, the digestive tract, the neural mass, the vitelline glands, and mature gametes were not immunoreactive. Immature germinal cells in both sexes, and the ootype in the female genital system, were found to express Sm28. Deposits of immunoreactive material on host skin following cercarial penetration, exfoliation from the male tubercles, and especially emission of Sm28 from eggs in hepatic granulomas are suspected to be a source of antigen during the parasite infection. The reduction in worm fecundity previously observed in immunization experiments may result from an antibody response directed against Sm28 present in the ootype. There was no cross-reactivity observed, under the experimental conditions used, between the anti-Sm28 sera and either vertebrate or invertebrate host tissue.

Animals↗
PubMed1994

Characterization and localization of Schistosoma mansoni calreticulin Sm58.

Recombinant Schistosoma mansoni calreticulin (SmCaR) was expressed in Escherichia coli, using the glutathione S-transferase fusion protein, and its Ca(2+)-binding capacity was determined. Results obtained by a 45Ca2+ overlay technique showed that Ca(2+)-binding site(s) were present in the recombinant CaR indicating that proper folding of the protein was obtained using this system. An antiserum raised against the recombinant SmCaR showed that the native protein (Sm58) was expressed in all stages of the life-cycle from cercariae to the adult worm and in the egg. However, SmCaR seems to be a developmentally regulated protein whose expression can be used to study the post-transformational differentiation of the schistosomulum. Localization of SmCaR demonstrated that the majority of SmCaR was expressed in the epithelia of the digestive duct and in the genital organs. These results suggest that SmCaR, by regulating the Ca2+ concentration, may play an important role during cell proliferation. Finally the presence of SmCaR in miracidia and in the genital organs suggests that the antibody response directed against this protein could interfere in egg production.

Amino Acid Sequence↗