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Biomedical subjects

A Capron

Publications and source records attributed to A Capron.

At least 19 recordsLinked to original sources
PubMed1992

Protection of mice and nude rats against toxoplasmosis by a multiple antigenic peptide construction derived from Toxoplasma gondii P30 antigen.

The first part of this work presents the sequence of the first 20 NH2 terminus residues obtained from P30, the major surface Ag of Toxoplasma gondii, purified by HPLC. A synthetic peptide (P30 48-67) has been prepared both in linear form and as a multiple antigenic peptide (MAP) construct. Immunization of mice and rats with the P30 48-67 MAP in the presence of IFA induces high levels of IgG antibodies that recognize both the linear peptide and the MAP construct in ELISA, and P30 in Western blots of NP-40-extracted tachyzoite Ag. Because these sera are negative in immunofluorescence assays with whole tachyzoites, it seems that IgG antibodies induced by P30 48-67 MAP, although recognizing the denatured structure, are unable to recognize the native protein. However, the protective effect of both constructs has then been studied in mice and nude rats. Whereas immunization of mice with the monomeric peptide does not confer any protection against oral infection with 1200 cysts of T. gondii 76K strain (mortality within 11 days), 40% of mice immunized with the MAP construct survived up to 75 days after infection. Nude rats were passively transferred with 5 x 10(4) T lymphocytes from P30 48-67 MAP-immunized Fischer rats before infection with 5 x 10(4) RH strain tachyzoites. They survived up to 40 days after infection and raised an intense IgG antibody response against P30, whereas nude rats transferred with control lymphocytes died within 21 days. This shows that immunization with P30 48-67 MAP also induces an efficient T cell immune response. The present work confirms the recently demonstrated role of P30 in protective immunity and shows the interest of peptide octameric constructions as inducers of partially protective immune responses in toxoplasmosis, as already demonstrated in schistosomiasis.

Amino Acid Sequence↗
PubMed1992

Decreased expression of eosinophil peroxidase and major basic protein messenger RNAs during eosinophil maturation.

We evaluated the levels of mRNAs encoding cationic proteins in peripheral blood eosinophils (PBE) purified from patients with eosinophilia and in eosinophils differentiated from cord blood cells (CBC) by culture with recombinant human interleukin-3 (rhIL-3), rhGM-CSF, and rhIL-5. Messenger RNAs encoding eosinophil peroxidase (EPO), major basic protein (MBP), eosinophil-derived neurotoxin (EDN), and eosinophil cationic protein (ECP) were detected by Northern blot hybridization with the respective specific oligonucleotide probes. In mature PBE, MBP mRNA appeared to be absent, whereas EPO mRNA was barely detectable in only 5 of the 19 patients. In contrast, EDN and ECP mRNAs were observed in the PBE of all patients. In CE, EPO, and MBP, mRNAs were abundant in immature eosinophils and their amounts decreased after differentiation toward eosinophils. ECP and EDN mRNAs followed the same patterns, but mRNAs were less abundant at all timepoints studied. Study of mRNA t1/2 during the time course of differentiation indicated that changes in the stability of the different mRNAs were not responsible for the variations observed in the steady-state levels. Together, these results suggest that regulation of expression differs among EPO, MBP, EDN, and ECP mRNAs during the time course of eosinophil differentiation.

Actins↗
PubMed1992

Productive human immunodeficiency virus-1 infection of megakaryocytic cells is enhanced by tumor necrosis factor-alpha.

Recent findings have indicated that megakaryocytes may be susceptible to human immunodeficiency virus (HIV) infection, suggesting a potential role for megakaryocytes as viral reservoirs in HIV-infected patients. We report that the megakaryocytic cell line Dami could be productively infected with the HTLV III-B strain of HIV-1, in 26 different experiments (results of 16 experiments are reported); productive infection lasted up to 30 weeks. Despite a lack of detectable surface expression of the CD4 molecule and very low levels of CD4 mRNA, between 40% and 60% of megakaryocytic cells produced viral proteins after contact with HIV-1. Neither cytopathogenic effects nor syncytial formation was observed. Production of high levels of functional viral particles was indicated by analysis of p24 protein levels, reverse transcriptase activity, ultrastructural studies, and the capacity of supernatants from infected Dami cells to infect the Molt-4 T-lymphocytic cell line. HIV-1 RNA and protein levels in infected Dami cells were enhanced by treatment with tumor necrosis factor-alpha (TNF-alpha), and decreased by treatment with interferon-alpha (IFN-alpha) and IFN-gamma. Transient transfection of the megakaryocytic cells with various constructs of the HIV-1 promoter (LTR) linked to the luciferase reporter gene suggested that the effect of TNF-alpha was related, as in monocytic and T-cell lines, to transactivation of the enhancer region of the HIV-1 LTR. These findings indicate that signals provided by the immune system may modulate HIV-1 expression in cells of the megakaryocytic lineage.

Cell Line↗
PubMed1992

Crystallization and preliminary X-ray diffraction studies of a protective cloned 28 kDa glutathione S-transferase from Schistosoma mansoni.

Crystals of the recombinant 28 kDa glutathione S-transferase from Schistosoma mansoni have been obtained by the hanging-drop method of vapor diffusion from ammonium sulfate solutions. The successful crystallization of this enzyme required the presence of a reducing agent and S-hexylglutathione. The crystals belong to the cubic space group P4(1)32 (or P4(3)32), with unit cell dimensions a = 122.6 A and contain one molecule in the asymmetric unit. The crystals diffract to at least 2.8 A resolution and are suitable for X-ray crystallographic structure analysis.

Animals↗
PubMed1992

Activation-induced death by apoptosis in CD4+ T cells from human immunodeficiency virus-infected asymptomatic individuals.

In immature thymocytes, T cell receptor for antigen (TCR) mobilization leads to an active T cell suicide process, apoptosis, which is involved in the selection of the T cell repertoire. We have proposed that inappropriate induction of such a cell death program in the mature CD4+ T cell population could account for both early qualitative and late quantitative CD4+ T lymphocyte defects of human immunodeficiency virus (HIV)-infected individuals (Ameisen, J.C., and A. Capron. 1991. Immunol. Today. 4:102). Here, we report that the selective failure of CD4+ T cells from 59 clinically asymptomatic HIV-infected individuals to proliferate in vitro to TCR mobilization by major histocompatibility complex class II-dependent superantigens and to pokeweed mitogen (PWM) is due to an active CD4+ T cell death process, with the biochemical and ultrastructural features of apoptosis. Activation-induced cell death occurred only in the CD4+ T cell population from HIV-infected asymptomatic individuals and was not observed in T cells from any of 58 HIV-seronegative controls, including nine patients with other acute or chronic infectious diseases. Activation-induced CD4+ T cell death was prevented by cycloheximide, cyclosporin A, and a CD28 monoclonal antibody (mAb). The CD28 mAb not only prevented apoptosis but also restored T cell proliferation to stimuli, including PWM, superantigens, and the tetanus and influenza recall antigens. These findings may have implications for the understanding of the pathogenesis of acquired immune deficiency syndrome and for the design of specific therapeutic strategies.

Antigens, CD↗
PubMed1992

Immunosuppression in the definitive and intermediate hosts of the human parasite Schistosoma mansoni by release of immunoactive neuropeptides.

Evidence supporting the concept that the parasitic trematode Schistosoma mansoni may escape immune reactions from its vertebrate (man) or invertebrate (the freshwater snail Biomphalaria glabrata) hosts by using signal molecules it has in common with these hosts was obtained by the following experiments. The presence of immunoactive proopiomelanocortin (POMC)-derived peptides [corticotropin (ACTH), beta-endorphin] in, and their release from, S. mansoni was demonstrated. Coincubation of adult worms with human polymorphonuclear leukocytes or B. glabrata immunocytes led to the appearance of alpha-melanotropin (MSH) in the medium. The conclusion that this alpha-MSH resulted from conversion of the parasite ACTH by neutral endopeptidase 24.11 (NEP) present on these cells was supported by the fact that the alpha-MSH level in the medium was markedly reduced by addition of the specific NEP inhibitor phosphoramidon. This interpretation is substantiated by the fact that no conversion was observed in comparable tests with human monocytes, which exhibit no NEP activity. alpha-MSH has the capacity to inactivate formerly active immunocytes not only from the definitive host (man, hamster) but also from the intermediate host (B. glabrata), as determined by microscopic computer-assisted examination of conformational changes. POMC-derived peptides have been detected in B. glabrata hemolymph 2, 10, and 24 days after infection by S. mansoni miracidia. Immunocytes from infected snails were found to be inactivated, and this inactivation was prevented by antibodies directed against ACTH and alpha-MSH. The immunoactive beta-endorphin released from S. mansoni does not appear to be subject to enzymatic conversion. Since it is active at lower concentrations, it may be used for distant signaling.

Adrenocorticotropic Hormone↗
PubMed1992

Cloning and expression of a cDNA encoding a non-classical MHC class I antigen (HLA-E) in eosinophils from hypereosinophilic patients.

A cDNA library, constructed from purified blood eosinophils, was screened with the B cell CD23 cDNA probe. A clone designated EO15 has been isolated and found to encode a non-classical HLA class I gene transcript. EO15 was compared with HLA-E and found to be 99.9% similar at the nucleotide level and to extend further in the 3' untranslated region. The presence of an additional polyadenylation signal in the EO15 3' end suggests that EO15 clone represents a copy of the 3.3-kb mRNA species detected in Northern blot analyses. HLA-E transcripts of 1.9 and 3.3 kb have been described in a variety of cell types. The two EO15 mRNA species, similar in size to the previously defined HLA-E mRNA, were present at high levels in blood leukocyte populations and at variable levels in different cell lines. The EO15 transcripts were found at abundant levels in hypodense and normodense eosinophils from hypereosinophilic patients. In situ hybridization confirmed the expression of EO15 mRNA in eosinophils. Neutrophils and lymphocytes from normal donors of from patients with hypereosinophilia also strongly expressed EO15 mRNA. Among the cell lines studied, the highest levels of EO15 transcripts were detected in B and monocytic cell lines, whereas intermediate and lower levels were found in eosinophilic, NK-like, megakaryocytic, and T cell lines, respectively. Similar to its effect on classical HLA class I transcripts, IFN-gamma increased the levels of EO15 mRNA in eosinophils and neutrophils from hypereosinophilic patients. These results suggest that purified blood eosinophils as well as neutrophils express EO15/HLA-E mRNA; however, further experiments are needed to investigate the localization and the function of EO15 protein products.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1992

Interleukin 5 messenger RNA expression by eosinophils in the intestinal mucosa of patients with coeliac disease.

Interleukin 5 (IL-5), the major factor involved in eosinophil differentiation, is produced by T cells or mast cells. In the present study, we found that eosinophils infiltrating the mucosa of four patients with active coeliac disease also express the IL-5 mRNA. No positive signal was obtained in normal duodenum tissues and in the cell infiltrate from patients submitted to gluten restriction. The identification of labeled mucosal cells as eosinophils relied on their typical morphology. Moreover, highly purified blood eosinophils from three out of four patients with eosinophilia were also strongly labeled with the IL-5 antisense but not with the corresponding sense probe. Together, these results suggest that eosinophils have the capacity to synthesize IL-5, which could contribute to paracrine interactions with T and B cells and, in autocrine fashion, locally participate, through binding to the IL-5 receptor, to eosinophil differentiation and activation. These data might have implications not only in the pathology of coeliac disease but also in other diseases associated with eosinophil infiltration.

Celiac Disease↗
PubMed1992

Antibodies in rheumatoid synovial fluids bind to a restricted series of protein antigens in rheumatoid synovial tissue.

OBJECTIVE: By searching the synovial fluid of patients with rheumatoid arthritis (RA) for antibodies that react to protein antigens in synovial tissue, we sought to identify putative antigens present in RA synovial tissue that might drive the pathologic immune response believed to be responsible for the joint inflammation. METHODS: Synovial tissue was homogenized in sodium dodecyl sulfate polyacrylamide gel buffer, electrophoresed, and analyzed by immunoblotting. RESULTS: Antibodies from synovial fluids of patients with RA bound to several proteins in rheumatoid synovial tissues, including a series of low (27.5-, 29-, and 30-kd), middle (43- and 53-kd), and high (140-, 164-, and 182-kd) molecular weight proteins. Most of these antigens were also detected in normal synovial tissue, and the high molecular weight proteins were also present in normal dermal, muscle, and liver tissues. The low and middle molecular weight proteins were detected in some, but not all, of the other normal tissues and in Jurkat cell lysates. Antibodies to the low and high series of proteins were present in all rheumatoid synovial fluids tested, but were generally absent from synovial fluids from patients with other arthritic diseases. CONCLUSION: These results show that antibodies in synovial fluids consistently react to several proteins in RA and normal synovial tissues. These antigens are possibly the same antigens provoking the T cell response in RA; therefore, understanding the mechanism of the immune response against these proteins will likely lead to important insight into the etiology of RA.

Antibodies↗
PubMed1992

Human endothelial cells transfected by SV40 T antigens: characterization and potential use as a source of normal endothelial factors.

A putative role for the vascular endothelium as target for autoantibodies has been suggested in several autoimmune disorders and connective-tissue diseases. However, there are some difficulties linked to the use of cultured endothelial cells (EC) that limit considerably the extensive studies on the nature of endothelial target antigens involved. To overcome this problem, human EC, derived from umbilical veins, were transfected with recombinant plasmid pSV1 which contained the early genes of simian virus SV40. These transfected cells, called EC-pSV1, are able to grow without EC growth supplement and demonstrate a population doubling time of about 50 h. Among the EC properties, EC-pSV1 retain intracellular content of angiotensin-converting enzyme activity, exhibit constitutive production of interleukin 6 and of a growth-promoting activity on early passage EV, express intercellular adhesion molecule 1 (ICAM-1) and its up-regulation by tumor necrosis factor alpha, but have lost the expression of factor VIII-related antigen. Moreover, EC-pSV1 express a 55-kDa antigen found on EC and human platelets, and presumably acting as an antibody target in some cases of non-allergic asthma. However, at the 50-55th generation, morphological changes and altered growth behavior were visible. This work demonstrates that transfection of EC with SV40 T antigens may be of interest, particularly in areas of research including the study of EC targets involved in different human diseases.

Antigens, Polyomavirus Transforming↗
PubMed1992

Immunity after treatment of human schistosomiasis: association between IgE antibodies to adult worm antigens and resistance to reinfection.

Previous studies in school children have demonstrated the slow development with age of resistance to reinfection after chemotherapy of Schistosoma mansoni infections, and have indicated that inappropriate ("blocking") antibody responses prevent the expression of immunity in young children. The present study was designed to investigate further the nature of the protective responses, by serological studies on a group of 151 S. mansoni-infected individuals resident in an endemic area in Machakos District, Kenya. Antibody levels against various antigens in blood samples before treatment were related to intensity of previous infections; antibodies in blood samples taken 6 months after treatment were related to cumulative reinfection rates over the following 30 months. IgE against an adult-worm antigen preparation correlated positively with age and negatively with reinfection. In contrast, IgE antibodies against other life-cycle stages showed either no relationship or the reverse correlation. Furthermore, antibodies of other isotypes against adult-worm antigens showed no correlations with reinfection. The correlation with IgE could be demonstrated for different preparations of adult worms, including a periodate-treated preparation presumptively depleted of carbohydrate epitopes. For both the intact and the periodate-treated preparations, multiple regression analysis of the results for children less than or equal to 16 years old demonstrated an IgE effect after allowing for age, although this effect was not observed in a previously studied group of school children. Western blot analysis of the adult-worm preparation revealed a limited set of antigens recognized by IgE, among which an antigen of 22 kDa was prominent. The qualitative presence of IgE against this antigen could also be shown to be related to a lack of subsequent reinfection.

Adolescent↗
PubMed1992

Separate induction of human blood platelet aggregation or cytotoxicity by different concentrations of PAF-acether and thrombin.

Using decreasing concentrations of PAF-acether or thrombin, it was possible to observe on human platelets, first, aggregation, classically associated to activation, then , below a threshold, cytotoxicity towards Schistosoma mansoni larvae, proposed here as stimulation. These two activities appeared as distinct and antithetic. However, their induction might be the consequence of triggering of the same receptors with different intensity, since PAF-induced, but not thrombin-induced, cytotoxicity could be inhibited with specific PAF-antagonists BN 52021 and BN 52024 also known to inhibit PAF-induced aggregation. These results give credit to the hypothesis that haemostatic and cytotoxic properties of platelets are two distinct functions of these blood elements.

Animals↗
PubMed1992

Eosinophil IgE receptor and CD23.

In the present review, eosinophil Fc epsilon RII was compared to CD23, a differentiation marker of B cells. Biochemical analysis revealed that molecules of similar molecular weight were immunoprecipitated from eosinophils and B cells by an anti-CD23 monoclonal antibody (mAb) or by BB10, and anti-eosinophil Fc epsilon RII. By flow cytometry, a correlation was found between the binding of anti-CD23 mAb and myeloma IgE. However, a low expression of different epitopes of CD23 was observed in various hypereosinophilic patients. Northern blot analysis of eosinophil RNA with the cDNA probe of CD23 revealed a weak message in only 3 of the 6 patients expressing membrane CD23. The inhibition by anti-CD23 mAbs of IgE-mediated cytotoxicity and IgE binding to eosinophils clearly indicated the participation of CD23 or a related molecule in IgE-dependent eosinophil functions. However, the differential effects of anti-CD23 mAbs on eosinophils and B cells suggest major differences in the characteristics of the molecule expressed by eosinophils and by B cells.

Antibodies, Monoclonal↗
PubMed1992

TNF-alpha production by U937 promonocytes is enhanced by factors released from HIV-infected T4 lymphocytes: TNF-alpha is one of the mediators causing lysis of HIV-infected T4 cells.

In the present study, we have shown that the addition of culture supernatants from HIV-infected SupT1 cells (T4) but not from noninfected cells markedly increased the production of TNF-alpha by U937 promonocytic cells after stimulation with phorbol 12-myristate 13-acetate (PMA). Pretreatment of supernatants with the antibodies to granulocyte/macrophage colony-stimulating factor (GM-CSF) or TNF-alpha, but not interferon-gamma, significantly diminished this enhancing effect. These results suggest that HIV may play an indirect role by producing cytokines from infected T4 cells that can lead to an increased production of TNF-alpha by monocytic cells. Further, TNF-alpha produced by U937 cells following stimulation with PMA plus lipopolysaccharide or with phytohemagglutinin induced lysis of HIV-infected T cells. TNF-alpha-induced cytotoxicity was markedly higher toward HIV-infected than toward noninfected T4 cells. Addition of antibody to TNF-alpha during the cytotoxic phase of response resulted in a reduction of about 50% in the percentage of cytotoxicity, indicating TNF-alpha as one of the lytic mediators.

Antibodies↗
PubMed1992

T helper cell epitopes of the human immunodeficiency virus (HIV-1) nef protein in rats and chimpanzees.

T helper cell antigenic and immunogenic determinants of the nef protein were investigated in the rat and chimpanzee models using recombinant nef protein and five synthetic peptides selected according to their amphipathic and alpha-helicity properties. The nef protein was shown to be immunogenic with both Freund's or aluminium hydroxide adjuvants. After immunization with the nef protein the 45-69 peptide was the most antigenic in rat and monkey models. In contrast, the 98-112 peptide, that required a carrier protein to induce in vitro rat T cell recall proliferation, was able to restimulate monkey T cells in the absence of a carrier. The amino acid sequence carrying the antigenic activity of the 45-69 peptide was further investigated by synthesizing short peptides overlapping this region. The antigenic sequence was precisely located in the middle of the peptide (region 50-59). This sequence was antigenic only when N alpha-acetylated. Circular dichroism analysis of the 45-69 peptide and the in vitro activity of the N-terminus group indicate in this case the involvement of the alpha-helical propensity for antigen presentation. However, the shorter sequence 50-64, able to induce a T cell reactivity, was determined as a beta-pleated sheet structure in aqueous solution. The 45-69 peptide was not only antigenic but also immunogenic and behaved in vivo as a functional T helper cell epitope. Indeed, the priming with the peptide or the transfer of peptide specific T cells to a naive recipient, followed by immunization with the nef protein, enhanced the subsequent antibody response to the nef protein. Together, these data indicate that the 45-69 peptide appears as a candidate for the in vivo elicitation of T cell immunity to the HIV-1 nef regulatory protein.

Amino Acid Sequence↗
PubMed1992

Determination of B-cell epitopes of nef HIV-I protein: immunogenicity related to their structure.

Determination of the B-cell epitopes of the nef molecule encoded by the human immunodeficiency virus type 1 (HIV-1) was undertaken using a set of six synthetic peptides. Sequences that were both antigenic and immunogenic and stimulated the production of antibodies recognizing the full length molecule, were considered as B-cell epitopes. Two peptidic sequences were antigenic both in rodents (mice and rats) and in non-human primates (chimpanzee). They were located in the regions 45-69 and 176-206 of the nef molecule. Two additional antigenic sequences were determined, one in chimpanzees, region 79-94, and the second in rodents, region 148-161. Immunogenicity was investigated in the rodents. Only the 45-69 and 176-206 sequences were immunogenic, and specific antibodies present in the sera of the immunized animals reacted with the nef protein. Therefore, each of these two sequences could be considered as containing at least one B-cell epitope. The fine epitopic specificity was determined using subfragments of these two sequences and it was shown that the antigenic determinants were contained in the C-terminal region of each sequence overlapping with the T-cell epitopes. These results raised the importance of vicinity of B- and T-cell determinants and their immunogenicity.

Amino Acid Sequence↗
PubMed1992

Amino acid sequence requirements for the epitope recognized by a monoclonal antibody reacting with the secreted antigen GP28.5 of Toxoplasma gondii.

We have characterized in detail, the epitope of the secreted antigen GP28.5 recognized by the mouse monoclonal antibody TG 17-179 using synthetic peptides and a truncated recombinant fusion protein. The screening of a T. gondii expression library with TG17-179 mAb led to the isolation of cDNAs clones, all encoding for the C-terminal region of GP28.5 and with one encoding for only the five last C-terminal residues. Competitive ELISA with longer peptides revealed that the immunoreactivity was retained for peptides of eight residues or longer, and lost when the peptide was reduced to the six last C-terminal residues or less. Experiments with the octapeptide lacking the carboxy-terminal glutamine residue showed it to be 64-fold less active. Moreover, neither addition of residues in the carboxy-end nor substitution of COOH function changed the immunoreactivity of the epitope. Competition experiments between TG17-179 mAb and sera from infected individuals demonstrates that the epitope defined by a mouse monoclonal probe is also a major epitope for human polyclonal antibodies. These results describe the sequence requirements within a probably linear epitope and give rise to some general question concerning experimental test for epitope mapping.

Amino Acid Sequence↗