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Biomedical subjects

A Capron

Publications and source records attributed to A Capron.

At least 163 records · Page 9Linked to original sources
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↗
PubMed1994

Molecular characterization of two Schistosoma mansoni proteins sharing common motifs with the vif protein of HIV-1.

We have previously described a rat mAb directed against a peptide derived from the vif protein of HIV-1 that recognized two Schistosoma mansoni (Sm) antigens with a major band at 65 kDa. Epitope mapping of this mAb using overlapping hexapeptides derived from the vif peptide revealed that the motif recognized was PLPSVT. The screening of a Sm cDNA library led to the identification of two clones, Sm70 and Sm65. The two deduced protein sequences did not share any common structural features apart from the epitope recognized by the mAb (see below), and did not show significant identity to sequences present in the data bases. However, the N terminus of the deduced sequence of the Sm70 protein exhibits a consensus sequence known to be an ATP/GTP binding site. Furthermore, the C terminus of the deduced Sm65 protein sequence was found to contain a conserved hexapeptide with a consensus sequence LPETGE reported to be an important motif of the surface proteins of gram-positive cocci. Both proteins exhibit a peptide sequence (PLRSVT for Sm70 and PVGSVT for Sm65) similar to the epitope recognized by the mAb anti-vif. Western blotting experiments showed that the mAb anti-vif reacted with both proteins. However, only Sm65 was recognized by sera from HIV-1-seropositive individuals, whereas both proteins were recognized by S. mansoni-infected patients.

Amino Acid Sequence↗
PubMed1994

Role of HIV-1 Nef expression in activation pathways in CD4+ T cells.

The role of the human immunodeficiency virus (HIV-1) Nef protein in T cell activation pathways was investigated using a Jurkat CD4+ cell line stably transfected with a Nef expression vector. Secretion of IL-2 and TNF-alpha, surface expression of IL-2R, and DNA-binding activity of NF-kappa B and AP-1 (Fos/Jun) complex in response to phorbol myristate acetate, TNF-alpha, or immobilized antibodies to CD3 were monitored. These parameters were not modified by Nef expression in Jurkat cells, whereas stimulation with the same stimuli resulted in partial inhibition of LTR activation in Nef+ Jurkat cells. This inhibition was not mediated through Nef phosphorylation on Thr-15 or GTP-binding activity because mutations in critical sites did not alter this inhibition. Analysis of truncated LTRs confirmed that inhibition of LTR activation was not mediated through NF-kappa B-binding activity but through the region containing the negative responding elements (NREs). These results suggest that Nef downmodulates LTR activation without significantly inhibiting the capacity of T cells to respond to immunological activations.

Base Sequence↗
PubMed1994

Interleukin-5 messenger RNA and immunoreactive protein expression by activated eosinophils in lesional atopic dermatitis skin.

The main cellular sources of interleukin-5 (IL-5) are T lymphocytes and mast cells. Recently, IL-5 mRNA has been identified in eosinophils from patients with celiac disease, eosinophilic heart diseases, and asthma. In an attempt to determine whether IL-5 is generated by eosinophils in atopic dermatitis we have used i) in situ hybridization with 35S-labeled IL-5 RNA probe combined with immunohistochemistry using a monoclonal antibody (MoAb) (EG2) directed against the activated form of Eosinophil Cationic Protein (ECP) and ii) double-immunostaining with anti-IL-5 MoAb and polyclonal anti-ECP antibody. We found that dermal eosinophils from lesional atopic dermatitis skin express IL-5 mRNA and protein. Moreover, highly purified blood eosinophils were also labeled with anti-IL-5 antibodies. The expression of IL-5 by eosinophils in atopic dermatitis might suggest an autocrine pathway of eosinophil differentiation and activation.

Cytoplasm↗
PubMed1994

Protective effect of rSm28GST-specific T cells in schistosomiasis: role of gamma interferon.

Immunization with a single dose of 50 micrograms of recombinant Schistosoma mansoni 28-kDa glutathione-S-transferase (rSm28GST) was able to induce a reduction in the worm burden, the number of eggs, and the degree of hepatic fibrosis as quantified by the measurement of collagen content in the liver of S. mansoni-infected mice. No relationship was found between anti-Sm28GST immunoglobulin G and immunoglobulin A titers and the levels of protection obtained. Adoptive transfers of Sm28GST-specific total, CD4+, or CD8+ T cells reproduced the protective effect obtained with the recombinant molecule. Moreover, experiments studying in vivo T-cell depletion demonstrated that anti-CD4- or anti-CD8-treated mice showed a significant decrease in the protective effect conferred, suggesting a role of the two T-cell subpopulations in the expression of Sm28GST-mediated protection against hepatic damage. Sm28GST-specific cells produced little interleukin-4 and high levels of gamma interferon. Treatment of immunized mice with anti-gamma interferon antibody totally suppressed the Sm28GST-induced protective effect and led to the rapid death of infected animals, suggesting a role for this cytokine in the expression of the protective immunity obtained after immunization with rSm28GST.

Animals↗
PubMed1994

Elevation of soluble CD23 in serum from patients with blood eosinophilia.

The levels of soluble CD23 (sCD23) were evaluated by a two-site immunoradiometric assay in the sera of 41 patients with eosinophilia-associated disorders and 20 normal subjects. We observed that, in the absence of treatment, sCD23 levels were elevated in patients with eosinophilia-associated Gleich's syndrome, IgA deficiency, T lymphoma or hypereosinophilic syndrome (HES), but not in patients with a parasitic infection. A significant reduction in the sCD23 levels was found after treatment, with a parallel decrease in eosinophil counts and in sCD25 levels, a marker of disease activity in HES. The lack of increase in membrane CD23+ B cells in eosinophilic patients together with the detection of sCD23 in eosinophil supernatants suggest that activated eosinophils present in eosinophilia-associated disorders can release soluble molecules cross-reacting with CD23. In conclusion, our results suggest that eosinophils themselves can represent one cellular source of sCD23. These findings are not only basic but also of clinical interest.

Adrenal Cortex Hormones↗
PubMed1994

Development of a vaccine strategy against human and bovine schistosomiasis. Background and update.

Two specific characteristics of schistosome infection are of primordial importance to the development of a vaccine: schistosomes do not multiply within the tissues of their definitive hosts (unlike protozoan parasites) and a partial non-sterilizing immunity can have a marked effect on the incidence of pathology and on disease transmission. Since viable eggs are the cause of disease pathology, a reduction in worm fecundity whether or not accompanied by a reduction in parasite burden is a sufficient goal for vaccine induced immunity. We originally showed that IgE antibodies played in experimental models a pivotal role for the development of protective immunity. These laboratory findings have now been confirmed in human populations. Following the molecular cloning and expression of a 28 kDa protein of Schistosoma mansoni and its identification as a glutathione-S-transferase, immunization experiments have been undertaken in several animal species (rats, mice, baboons). Together with a significant reduction in parasite burden, vaccination with Sm28 GST was recently shown to reduce significantly parasite fecundity and egg viability leading to a decrease in liver pathology. Whereas IgE antibodies were shown to be correlated with protection against infection, IgA antibodies have been identified as one of the factors affecting egg laying and viability. In human populations, a close association was found between IgA antibody production to Sm28 GST and the decrease of egg output. The use of appropriate monoclonal antibody probes made it possible to demonstrate that the inhibition of parasite fecundity following immunization was related to the inhibition of enzymatic activity of the molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

SCID-Hu mouse as a model for human lung HIV-1 infection.

HIV induces a multi-organ infection with a dual tropism for both lymphocytes and monocytes/macrophages. The lung is a target both for HIV infection and HIV-related opportunistic infections. The SCID mouse has provided the opportunity to develop a small animal model for HIV infection. However, HIV-1 infection of the human fetal thymus and liver (SCID Liv/Thy) implanted in these mice occurred only after direct intraimplant injection of HIV-1 and the resultant HIV-1 infection was restricted to the human thymus. Here we report that human foetal lung can develop in SCID Liv/Thy mice resulting in the development of normal human alveolar and bronchiolar lung compartments which can be productively infected with cell-free HIV-1 virus, leading to a systemic and bifocal infection. This SCID-Hu model should be useful for studying AIDS physiopathology, human viruses with lung tropism and for helping to define gene therapy protocols in lung human cells in vivo.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Synovial fibroblast-like cell transfection with the SV40 large T antigen induces a transformed phenotype and permits transient tumor formation in immunodeficient mice.

OBJECTIVE: To understand the intracellular signals leading to transformed-like growth of synovial fibroblast-like cells from patients with rheumatoid arthritis (RA). METHODS: Cell lines stably transfected with one or both of 2 complementary oncogenes, the SV40 large T antigen and the ras oncogene, were studied for phenotypic changes. RESULTS: Synovial fibroblast-like cells stably transfected with the SV40 large T antigen, but not the ras oncogene, showed high levels of growth factor independent proliferation, grew under anchorage independent conditions, expressed cathepsin L mRNA, and formed transient tumors in immunodeficient mice. Synovial fibroblast-like cells stably transfected with both oncogenes appeared phenotypically similar to synovial fibroblast-like cells transfected with the large T antigen alone. CONCLUSION: The SV40 large T antigen confers a phenotype on synovial fibroblast-like cells similar to that stimulated by growth factors, suggesting that it stimulates the same intracellular signalling pathway leading to cytokine induced, transformed synovial fibroblast-like cell growth. When injected into immunodeficient mice these transfected cells formed tumors characterized by rapid, transient growth, central necrosis, and neutrophil infiltration.

Animals↗
PubMed1994

[Eosinophil, beneficial or harmful: a cell entirely part of immune response].

The demonstration that human eosinophils could express various membrane receptors (for IgG, IgE, IgA; for complement; for cytokines; for chemotactic factors), for adhesion molecules (VLA4, LFAI, OKM1), as well as CD4 and class II MHC, has allowed to reconsider the role of eosinophils in immune response. Indeed, eosinophils can function as antigen presenting cells and can be infected by HIV. Studies on eosinophil mediators have revealed that eosinophils are not only the source of cytotoxic and proinflammatory mediators but can also release various cytokines and growth factors, including their own factors of differentiation (IL-3, GM-CSF and IL-5). The recent observation that eosinophils expressed IgE binding molecules belonging to different gene superfamilies (CD23, Mac2/epsilon BP and FceRI), as well as two different IgA receptors (Fc alpha R, and secretory component binding site), participating both in antiparasite immune defence and in inflammatory processes, reinforces the concept of the functional duality of eosinophils, specially in tissues.

Antibody Formation↗
PubMed1993

Synthesis of interleukin-5 by activated eosinophils in patients with eosinophilic heart diseases.

Eosinophilic endomyocardial disease represents a major evolutive risk in chronic eosinophilia-associated disorders. Eosinophil granule proteins appear to be involved in cardiac injury, but the mechanisms leading to eosinophil infiltration and degranulation are not clear. Interleukin-5 (IL-5) has been recently shown to be produced by eosinophils and might play a role in both chemoattraction and degranulation of eosinophils. In four cases of eosinophilic diseases with severe cardiac failure, we evaluated the proportion of eosinophil phenotypes and the serum levels of eosinophil cationic protein (ECP) and soluble IL-2 receptor (sIL-2R), markers of disease activity in the hypereosinophilic syndromes. All four patients showed a markedly increased proportion of hypodense eosinophils with elevated serum ECP and sIL-2R levels. In all four patients, extracellular deposition of eosinophil granule proteins and features of eosinophil activation were observed in cardiac tissues. The synthesis of IL-5 by eosinophils was detected in myocardial sections and blood cells by in situ hybridization and by immunostaining with a monoclonal antibody against human IL-5. Sixty percent to 90% of tissue eosinophils expressed IL-5 mRNA and IL-5 protein. These data suggest that IL-5 can be produced by eosinophils at the sites of myocardial tissue damage and might participate in local eosinophil activation.

Biopsy↗
PubMed1993

Cloning and characterisation of the gene encoding the 28-kDa glutathione S-transferase of Schistosoma mansoni.

The 28-kDa glutathione S-transferase (GST) of Schistosoma mansoni is considered a possible vaccine candidate for use against this medically important parasite. The gene encoding this molecule has been isolated from a lambda EMBL4 library by using the corresponding cDNA sequence as a probe. The gene contains four exons and is approximately 5.5 kb in length. Analysis of the 5' flanking region revealed the presence of a consensus AP-1 recognition site, 5'-TGACTCA, between nucleotides -231 and -225. Southern blot analysis suggested the presence of a single gene encoding the 28-kDa GST in the S. mansoni genome.

Amino Acid Sequence↗
PubMed1993

[Vaccine against bilharziasis. Strategies and perspectives].

Due to the determination of immunity acquisition mechanisms, a number of studies on experimental models and human populations has made it possible to devise a strategy of vaccination against schistosomiasis, a major worldwide parasitic disease affecting 200 million people. A schistosomial protein, identified as glutathione-S-transferase (SM28GST) has been cloned and expressed in various vectors. Immunization with the recumbent protein results in a significant reduction of the parasitic load, while the fertility of schistosoma and the viability of its eggs are markedly inhibited. Recent experiments performed in primates and bovines have shown that a more than 90% inhibition of the schistosoma's transmission potential can be induced by this vaccine. The important role played by IgA antibodies in the inhibition of the parasite's fertility has led to the development of an oral immunization strategy. In view of the results obtained, the availability, in the near future, of a vaccine protecting human beings against this scourge can be considered realistic.

Animals↗
PubMed1993

Schistosoma mansoni 28-kDa glutathione S-transferase and immunity against parasite fecundity and egg viability. Role of the amino- and carboxyl-terminal domains.

We have previously shown that a mAb that inhibits the enzymatic activity of the Schistosoma mansoni 28-kDa glutathione S-transferase (Sm28 GST) also reduces female worm fecundity and egg viability in vivo and in vitro. By peptidic epitope mapping and an activity reconstitution assay, the carboxyl terminus (CT) amino acid residues 190-211 and to a lesser extent the truncated amino terminus (NT) residues 10-43 of the enzyme were identified as mAb recognition sites. Sera from rats immunized with the NT (10-43) and CT (190-211) peptides showed a partial inhibitory effect on Sm28 GST activity in a late phase (6 to 7 wk) but not in an early phase (2 to 4 wk) after immunization. Passive transfer of Sm28 GST-inhibiting anti-N- and C-terminal sera, but not of the noninhibitory sera, protected the infected mice by reducing tissue egg deposition and the ability of eggs to hatch. In active immunization experiments, the CT peptide significantly decreased the worm burden (37 to 40%) in mice as did the rSm28 GST (28 to 52%). In terms of tissue egg deposition and egg-hatching ability, immunization with both the NT and CT peptides reproduced the reduction observed after immunization with rSm28 GST. A constant reduction in egg numbers was noted in the small intestines and the livers of the immunized mice. A clear reduction in the ability of intestinal or hepatic eggs to hatch was observed. The results are discussed in terms of the conformational participation of the NT and CT of Sm28 in the expression of GST activity.

Amino Acid Sequence↗
PubMed1993

IgA antibodies to a protective antigen in human Schistosomiasis mansoni.

The specific IgA antibody responses to the protective recombinant Schistosoma mansoni 28-kDa glutathione-S-transferase (Sm28GST) Ag and to derived synthetic peptides have been evaluated before and 6 mo after chemotherapy in S. mansoni-infected patients from Kenya. These studies revealed a parallelism between the age-dependent evolution of IgA antibody levels to Sm28GST and to one synthetic peptide (115-131) and the acquisition of resistance to reinfection. Functional analysis revealed that IgA antibodies to Sm28GST displayed a potent neutralizing effect on the enzymatic properties of the molecule, and also markedly impaired schistosome fecundity, by limiting both the egg laying of mature worms and the hatching capacity of schistosome eggs into viable miracidia. These results suggest that, in addition to IgE, IgA antibodies might participate in the protective immune response against schistosomiasis.

Adolescent↗