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C Leclerc

Publications and source records attributed to C Leclerc.

At least 145 records · Page 8Linked to original sources
PubMed1992

Alloantigen-specific regulation of cytotoxic T cell responses is mediated through the induction of clonal anergy of CD8+ T cells.

Priming mice with an alloantigen before immunization with this same alloantigen presented in association with a second one on an F1 stimulator cell inhibits the induction of cytotoxic response directed against the second alloantigen. This inhibition is associated with the induction of a strong cytotoxic T lymphocyte (CTL) response against the first priming alloantigen. For example, a specific suppression of anti-H-2b CTL responses could be induced in C3H/He mice (H-2k) by priming them with H-2d spleen cells before immunization with F1 (H-2dxb) spleen cells. In the present study, we have analyzed the mechanisms underlying this specific suppression of CTL responses. We have demonstrated that the reduction of H-2b-specific CTL responses is reflected by a decrease in the frequency of effector cells specific for H-2b antigen. However, there was no difference in the frequencies of precursor CTL in control and suppressed mice excluding clonal deletion as the mechanism maintaining low responsiveness. Co-culture experiments have shown that the suppression of anti-H-2b CTL responses was not due to suppressor cells but to the failure of CD8+ T cells of suppressed mice to collaborate with normal helper CD4+ T cells. The suppression was therefore ascribed to a functional impairment (clonal anergy) of the CD8+ T cell subset.

Animals↗
PubMed1992

Molecular detection and in vivo analysis of the specific T cell response to a protein antigen.

We have analyzed in detail the repertoire of transcripts encoding the V beta chains of the T cell receptor and investigated the T cell response of B10.A mice to pigeon cytochrome c. We were thus able to follow the specific T cell response in vivo after immunization with this protein antigen. The response is first detectable in the draining lymph nodes, then in the spleen and in the blood. It is qualitatively similar in individual animals. It is dominated by a major category of specific T cells harboring a V beta 3-J beta 1.2 rearrangement, and a limited and well-defined set of nucleotide sequences, previously found in several specific T cell hybridomas and clones. This predominance is observed from the onset of the immune response strongly suggesting the notion that there is no variation and, therefore, no maturation of the T cell response in the course of immunization.

Animals↗
PubMed1992

Expression of Escherichia coli beta-galactosidase in Mycobacterium bovis BCG using an expression system isolated from Mycobacterium paratuberculosis which induced humoral and cellular immune responses.

A promoter sequence, PAN, was isolated from Mycobacterium paratuberculosis and characterized. This promoter lies adjacent to, and outside, the 3' end of an IS900 insertion element. IS900 contains an open reading frame, ORF2, on the complementary strand which codes for the putative transposase of this insertion sequence. A DNA fragment containing PAN and part of ORF2 was fused to the lacZ gene and inserted into the replicative shuttle vector pRR3. Mycobacterium smegmatis and Mycobacterium bovis BCG (BCG) transformed with this plasmid exhibited beta-galactosidase activity. However, lacZ was only expressed in Escherichia coli under the control of PAN, when ORF2 was deleted. Immunization of mice with the recombinant M. bovis BCG expressing lacZ resulted in the induction of a high humoral and cellular response directed against beta-galactosidase. The PAN-ORF2 expression system may prove to be particularly useful for cloning and expression of heterologous genes in the BCG vaccine strain.

Amino Acid Sequence↗
PubMed1991

Expression of heterologous genes in Mycobacterium bovis BCG: induction of a cellular response against HIV-1 Nef protein.

Mycobacterium bovis bacillus Calmette-Guérin (BCG) has been used as a live bacterial vaccine to immunize more than two billion people against tuberculosis. In an attempt to use this vaccinal strain as a vehicle for protective antigens, the human immunodeficiency virus type 1 gene encoding the Nef protein was cloned in a mycobacteria-Escherichia coli shuttle plasmid and transferred into BCG. The nef gene was expressed under the control of an expression cassette carrying the promoter of the groES/groEL1 operon from Streptomyces albus and a synthetic ribosome-binding site. Lymph node cells from mice immunized with BCG-nef proliferated vigorously in response to purified Nef protein. This first report of a proliferative response suggests that recombinant BCG strains may be used to immunize against pathogens for which T-cell-mediated responses are important for protection.

Gene Products, nef↗
PubMed1991

In vivo induction of cytotoxic T cell response by a free synthetic peptide requires CD4+ T cell help.

Most attempts to induce CTL responses by in vivo priming with free synthetic peptides have been unsuccessful so far. However, two separate studies have recently succeeded in inducing antiviral CTL responses by immunizing mice with unmodified free synthetic peptides derived from nucleoproteins from either lymphocytic choriomeningitis virus or Sendai virus. In the present study, we have analyzed the cellular mechanisms by which the lymphocytic choriomeningitis virus synthetic peptide induced CTL responses. We demonstrated that this peptide, which was previously shown to be recognized by CD8+ T cells, also contains a helper CD4+ T cell epitope. It stimulates in vivo both CD4+ T cell-mediated CTL response. The in vivo elimination of CD4+ T cells by treatment with a mAb was shown to strongly reduce the antipeptide CTL response. This study therefore demonstrates that to be able to induce CTL responses, a peptide has to stimulate both CD4+ and CD8+ T cell subset.

Animals↗
PubMed1991

The cellular location of a foreign B cell epitope expressed by recombinant bacteria determines its T cell-independent or T cell-dependent characteristics.

We have targeted two foreign B cell antigenic determinants to different locations in the Escherichia coli cell to examine what effect this had on antibody responses elicited by the recombinant bacteria. The two epitopes were the 132-145 peptide from the PreS2 region of hepatitis B virus and the C3 neutralization epitope of poliovirus type 1. They were each expressed in two forms either on the surface, as part of the outer-membrane protein LamB, or soluble in the periplasm, as part of the periplasmic protein MalE. When live bacteria expressing the foreign epitope at the cell surface were used for immunization of mice, they induced T cell-independent antibody responses characterized by a rapid induction of IgM and IgG antibodies. In contrast, when the same foreign epitope was inserted into the MalE protein, the antibody response was only detectable after 3 wk, belonged only to the IgG class and was strictly T cell dependent. This study has therefore identified two major pathways by which epitopes expressed by bacterial cells can stimulate specific antibody responses. The first pathway is mediated by direct activation of B cells by bacterial cell-surface Ag and does not require T cell help. The second pathway is T cell dependent and concerns Ag that can be released from the bacteria in a soluble form. We have also studied the effect of the exact position of the B cell antigenic determinant within the LamB protein and with respect to the outer membrane by comparing the immunogenicity of the PreS epitope inserted at three different permissive sites of LamB. The data indicated that to obtain an antibody response with intact bacteria, the epitope must be protruding sufficiently from the outside of the outer membrane. In contrast, when semipurified hybrid proteins were used as immunogen, the exact position of the B cell antigenic determinant within solubilized LamB protein does not influence its immunogenicity.

ATP-Binding Cassette Transporters↗
PubMed1991

Rabies-specific production of interleukin-2 by peripheral blood lymphocytes from human rabies vaccinees.

Cell-mediated immunity induced by rabies vaccination was studied in humans by the determination of specific interleukin-2 (IL-2) production in a large number of donors (postexposure immunized patients and pre-exposure immunized laboratory workers). Peripheral blood lymphocytes (PBL) from 35 donors were tested for IL-2 production after in vitro stimulation by different rabies and rabies-related viruses. IL-2 responses were compared to antibody recognition of these different virus serotypes by sera from the same individuals. IL-2 was produced by PBL from more than 85% of donors after stimulation with inactivated and purified rabies viruses (IPRV) prepared from either Pittman Moore (PM) or Pasteur Virus (PV) strains. IL-2 was also produced by 65 and 45% of donor PBL stimulated with IPRV from the European Bat Lyssavirus (EBL) and Mokola (Mok) rabies-related virus strains respectively. No correlation was found between the production of IL-2 by PBL and the levels of virus neutralizing antibody (VNAb). Moreover, 50, 25 and 35% of donors produced IL-2 after stimulation of their PBL with ribonucleoprotein (RNP) from PV-, EBL- and Mok-viruses, respectively. These results obtained with a large number of human rabies vaccinees and using an assay specific to T-cell activation confirm the significant cross-reactivity of T-cell responses directed against rabies and rabies-related viruses. This study shows that IL-2 production could be used for the study of cell-mediated immunity and T-cell memory induced in humans by rabies vaccination.

Adult↗
PubMed1991

Appraisal of rabies vaccine potency by determination of in vitro, specific interleukin-2 production.

The potency of different rabies vaccines was measured via cell mediated immunity (CMI) assessed by the production of interleukin-2 (IL-2) by CD4+CD8- lymphocytes. IL-2 production by splenocytes from mice immunized with various vaccines was measured following in vitro stimulation with antigens from different rabies and rabies-related strains. IL-2 production was specific, reproducible and correlated with the vaccine protective activity as determined by the pre-exposure NIH test. Our results suggest that measurement of IL-2 production could be used for the appraisal of rabies vaccine potency.

Animals↗
PubMed1991

A genetic system to elicit and monitor antipeptide antibodies without peptide synthesis.

We present a simple and flexible procedure to elicit and assay anti-peptide antibodies without peptide synthesis. It consists of expressing the peptide of interest in the form of a genetic insert within two different "recipient" bacterial proteins. One hybrid protein is used as immunogen for the induction of antibodies against the inserted peptide and the other as antigen for monitoring the anti-peptide antibodies raised. The two "recipient" proteins used are the MalE and the LamB proteins from E. coli. The MalE hybrid proteins can be affinity purified on an amylose column using mild nondenaturing conditions and can be crystalized for structural studies; LamB hybrid proteins express the inserted peptide on the cell surface so that intact bacteria can be used as a reagent. We chose, as a model peptide, a B-cell epitope from the pre-S(2) region of Hepatitis B virus. With both MalE and LamB hybrid proteins, high titres of anti-preS antibodies, able to react with native HBsAg particles, were induced in mice. The anti-peptide antibody titres recorded by ELISA were comparable to those obtained when either a synthetic peptide, or the hybrid proteins, were used as immobilized antigen.

Animals↗
PubMed1991

Cellular basis of the resistance of newborn mice to the pathogenic effects of anti-CD3 treatment.

We have analysed the mechanisms underlying the differences in the susceptibilities of adult and newborn mice to the pathogenic effects of anti-CD3 mAbs. Our data show that the thymus cell number in adults is reduced by 93% 48 h after one single injection of 5 mg/kg of Ab whereas the same dose in newborns induces only a 30% decrease. In the adult, this effect is associated with a marked depletion of CD4+ CD8+ double positive (DP) cells and with the appearance of important areas of cell necrosis in the thymic cortex. In newborns, the DP cells are less affected and the thymic cortex does not present any cell necrosis even after an injection of 45 mg/kg of mAbs. Pre-treatment of adults with anti-CD4 and anti-CD8 Abs, while completely abolishing the toxic side-effects induced by anti-CD3 mAbs, does not protect the thymus from the depletion of DP cells. In vitro, anti-CD3 mAbs induce the proliferation of thymocytes and spleen cells from adults but not from newborns. Tumour necrosis factor-alpha (TNF alpha) is found in the serum of adults 90 min after injection of anti-CD3 but is never detected in the serum of anti-CD3 treated newborns. Taken together our data support the view that anti-CD3 mAbs act by two different mechanisms. The first one results from the binding of anti-CD3 on the CD3+ thymocytes which induces a direct toxicity for only the CD4+ CD8+ cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1991

Identification of a T-cell epitope adjacent to neutralization antigenic site 1 of poliovirus type 1.

Proliferative T-cell responses to poliovirus in various strains of mice have been analyzed by using either killed purified virus or capsid protein VP1 synthetic peptides. Following immunization of mice with inactivated poliovirus type 1 (PV1), a specific proliferative response of their lymph node CD4+ T cells was obtained after in vitro stimulation with purified virus. In mice immunized with PV1, PV2, or PV3, a strong cross-reactivity of the T-cell responses was observed after in vitro stimulation with heterologous viruses. By using various strategies, a dominant T-cell epitope was identified in the amino acid 103 to 115 region of capsid polypeptide VP1, close by the C3 neutralization epitope. The T-cell response to VP1 amino acids 103 to 115 is H-2 restricted: H-2d mice are responders, whereas H-2k and H-2b mice do not respond to this T-cell epitope. Immunization of BALB/c (H-2d) mice with the uncoupled p86-115 peptide, which represents VP1 amino acids 86 to 115 and contains both the T-cell epitope and the C3 neutralization epitope, induced poliovirus-specific B- and T-cell responses. Moreover, these mice developed poliovirus neutralizing antibodies.

Amino Acid Sequence↗
PubMed1991

Bacterial vectors to target and/or purify polypeptides: their use in immunological studies.

The construction of recombinant proteins by genetic engineering has opened new avenues in basic research (studies on protein organization, protein folding, immunogenicity of proteins, ...) and many different applications. Recombinant proteins which keep properties of both parental proteins are especially interesting. For example, if one protein--the vector protein--is targeted to a given cellular compartment, the other protein--the passenger--may be identically targeted. Also, if the vector protein can be purified by a simple affinity chromatographic procedure, this property may be extended to the passenger. The authors have developed a genetic procedure to detect "permissive" sites within potential vector proteins so that genetic fusion to these sites keep most or all biological properties of the vector. When they used LamB, an outer membrane protein from E. coli, foreign sequences could be expressed at the bacterial cell surface. This may lead to several types of applications: live bacterial vaccines, simple diagnostic tests, selection procedures for peptides with biological activity. When they used the MalE protein, a periplasmic maltose binding protein from E. coli, the passengers could be exported and purified in one-step high affinity chromatography in mild non-denaturing conditions. This led us to a simple preparation and purification scheme for the soluble part of the CD4 receptor for the Human Immunodeficiency Virus (HIV).

Bacterial Outer Membrane Proteins↗
PubMed1990

The in vivo elimination of CD4+ T cells prevents the induction but not the expression of carrier-induced epitopic suppression.

Injection of mice with an immunogenic dose of carrier (keyhole limpet hemocyanin (KLH)) followed by immunization with hapten-carrier conjugate (TNP-KLH) selectively suppresses anti-hapten antibody response. In this study, the cellular basis of this epitopic suppression and also of the suppression induced by a high dose of carrier were analyzed by in vivo depletion of CD4+ or CD8+ T cell subsets by using mAb. The mAb treatments were performed either at the time of carrier priming or at the time of hapten-carrier immunization. The elimination of CD8+ T cells has not modified the anti-carrier antibody response, whether this treatment was performed at the time of KLH-priming or during TNP-KLH immunization. Moreover, the in vivo treatment with the anti-CD8 mAb did not modify the carrier-induced epitopic suppression induced either by a low immunogenic dose of KLH or by a high dose of this Ag. The elimination of CD4+ T cells at the time of KLH immunization has prevented the induction of a memory response to KLH, clearly establishing that CD4+ T cells are essential in memory B cell development to T-dependent Ag. Moreover, this treatment has totally abrogated the epitopic suppression induced either by low or high dosages of KLH. In contrast, the in vivo elimination of CD4+ T cells after carrier immunization did not abolish the secondary anti-carrier antibody response and did not prevent the expression of epitopic suppression. These data indicate that primed CD4+ T cells are required neither for memory B cell expression nor for the expression of suppression. Finally, once induced, the suppression can be evidenced after in vivo depletion of both primed CD4+ and CD8+ T cells. These data support the view that epitopic suppression is induced through the expansion of carrier-specific B cells and resulted from intramolecular antigenic competition between hapten and carrier epitopes.

Animals↗
PubMed1990

Critical role of neighbouring sequences on the immunogenicity of the C3 poliovirus neutralization epitope expressed at the surface of recombinant bacteria.

The C3 neutralization epitope of poliovirus type 1 (PV-1) is a continuous epitope comprised within residues 93-103 of capsid protein VP1. These residues form a loop at the surface of the virus particle. The authors compared the immunogenicity of two peptides which contain this epitope, when presented at the surface of Escherichia coli by genetic insertion in the outer membrane protein LamB. One peptide was 13 residues long (VP1:93-103) and the other one contained flanking sequences increasing its size to 35 residues (VP1:86-115). Mice and rabbits were immunized with recombinant bacteria expressing the corresponding LamB-VP1 hybrid proteins. Antibodies against synthetic peptides, against native and heat denatured viral particles, as well as neutralizing antibodies were monitored. In this mode of presentation the shortest form of the epitope was more immunogenic. We provide evidence that the conformation of the epitope is different in the two hybrid LamB proteins and discuss possible consequences for immunogenicity.

Amino Acid Sequence↗
PubMed1990

Painful shoulder in the hemiplegic and unilateral neglect.

Shoulder pain is a frequent and debilitating problem in hemiplegic patients, and its etiology remains poorly understood. The role played by hemineglect in the appearance of shoulder pain was studied. During two years, 94 hemiplegic subjects were involved in a rehabilitation program after cerebrovascular accidents. Their average age was 68 years; 45 (47.9%) subjects had shoulder pain, and 24 subjects (22.5%) had hemineglect. The subjects with shoulder pain were compared to those without pain (the control group) with respect to gender, age, diabetes, heart failure, cardiac ischemia, scapulohumeral arthritis, and calcified tendinitis of the rotator cuff. We were unable to demonstrate a relationship between hemineglect and shoulder pain in the hemiplegic (X2 (1) = 2.03, p = .15), although pain was significantly more frequent in subjects with right hemispheric cerebrovascular accident (X2 (1) = 5.0, p less than .025). The subjects with shoulder pain had significantly more spasticity of the affected limb (X2 (1) = 26.3, p less than .01), less sensitivity to pinprick of the upper paralyzed extremity (X2 (1) = 10.8, p less than .01), and a more severe subluxation of the affected shoulder (t(51) = 14.0, p less than .01).

Aged↗
PubMed1989

Alloantigen pretreatment induces a down-regulation of the in vivo subsequent development of cytotoxic T lymphocytes directed against linked alloantigens.

In the present study, we describe a new regulatory system that influences the in vivo development of cytotoxic T lymphocytes (CTL) and that could be related to epitopic suppression. Epitopic suppression has been previously shown to occur when carrier-primed mice are subsequently immunized with a "new" epitope coupled to the priming carrier. The suppression specifically inhibited the antibody response to the "new" epitope without affecting the secondary antibody response to the carrier. In this report, using a carrier/hapten-carrier type of immunization protocol, we have demonstrated that a similar regulatory system could also affect the induction of CTL directed against allogeneic cells. Priming mice with an alloantigen 1 (carrier) inhibits the induction of alloantigen 2 (hapten)-specific cytotoxic responses when the alloantigen 2 is presented in association with the alloantigen 1 on an F1 stimulator cell (hapten-carrier conjugate). This has been demonstrated by the specific decrease of anti-H-2b or anti-H-2d CTL responses generated in C3H/He mice (H-2k) previously primed with, respectively, H-2d or H-2b spleen cells before immunization with F1 (H-2d x b) spleen cells. This suppression of the CTL responses against the second immunizing alloantigen is associated with a strong CTL response against the first priming alloantigen. The induction of the suppression is dependent on the dose of H-2d spleen cells administered before immunization with F1 spleen cells and is not related to antigen elimination since a strong suppression of the CTL response against H-2b antigens is shown following immunization with a mixture of F1 cells and H-2b-bearing cells of H-2d-primed animals.

Animals↗
PubMed1989

Antibody response to a foreign epitope expressed at the surface of recombinant bacteria: importance of the route of immunization.

A genetic procedure has been previously established to expose a foreign epitope at the surface of Escherichia coli by using the outer membrane LamB protein as a carrier. A portion of the pre-S2 region of hepatitis B virus, residues 132-145, has been inserted at amino acid position 153 of the LamB protein, in a cell surface exposed loop. In the present study, we have analysed the antibody responses induced by these recombinant bacteria (live, heat-killed or sonicated) depending upon the route of immunization. The intravenous (i.v.) or intraperitoneal (i.p.) administration of the live recombinant bacteria to mice induced the synthesis of antibodies against both the inserted peptide and the native LamB protein. The antibodies raised recognized HBsAg particles. These mice also had high titres of antibodies against E. coli antigens (as determined using a crude bacterial sonicate). In contrast, mice immunized subcutaneously (s.c.) did not develop antibodies against the pre-S2 peptide nor against the HBsAg particles. Their anti-LamB responses were low compared with the response of mice immunized by the parenteral route. Interestingly, s.c. or i.v. immunizations induced comparable levels of anti-E. coli antibodies. Thus, the antibody response to the inserted peptide generally parallels the response to the LamB protein (and not to the bulk of E. coli antigens). However, this treatment corresponding to a 'pre-processing' of the recombinant bacteria was not sufficient to obtain an anti-peptide response following s.c. immunization.

Animals↗