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M Zouali

Publications and source records attributed to M Zouali.

At least 55 records · Page 3Linked to original sources
PubMed1994

Clonotypic dominance and variable gene elements of pathogenic anti-DNA autoantibodies from a single patient with lupus.

This study explores the usage and diversity of the variable gene elements expressed by human lupus antibodies to DNA bearing the 0-81 idiotype, a marker of pathogenic anti-DNA autoantibodies. Rather than studying DNA-specific clonotypes from different patients, a panel of idiotype positive anti-DNA autoantibody-secreting clones from a single individual were analysed. By cloning and nucleotide-sequencing the heavy-chain variable gene segments, evidence was found for dominance of clonotypic patterns. Also noted was a high rate of diversification among the variable (VH), diversity (DH) and junctional (JH) gene segments utilized, with a pattern of mutations indicative of antigenic selection. These features suggest that the clones secreting the lupus pathogenic autoantibodies have been selected over multiple generations through an affinity-maturation process that is reminiscent of antigen-driven immune responses.

Adult↗
PubMed1993

Autoimmune diseases--at the molecular level.

Autoimmunity and autoimmune diseases are the focus of intensive research using the concepts and tools of immunology, molecular genetics and cell biology. A group of scientists recently gathered to discuss recent developments in organ-specific and systemic autoimmune diseases in both human and animal models. In this article, we hope to convey some of the excitement and enthusiasm evident at the meeting which placed emphasis on work at the molecular level.

Animals↗
PubMed1992

Molecular events in the development of the lymphocyte repertoire.

Last autumn, an international cast of molecular geneticists and immunologists coalesced around the comfortable Bishenberg Centre in the hills of Alsace to assess various aspects of the expression and development of the lymphocyte repertoire*. Here, progress in the understanding of control of genomic rearrangements and development of the lymphocyte repertoire are described.

Animals↗
PubMed1992

Antibodies of HIV-1 positive subjects and experimentally immunized primates and rodents bind to sequence divergent regions of the third variable domain (V3) of gp120.

Several motifs have been found to be the target of the neutralizing antibody response to HIV, the human immunodeficiency virus. One of the well characterized motifs maps to a loop within the third hypervariable region (V3) of the exterior envelope glycoprotein gp120 at amino acid positions 308-331 and is referred to as the principal neutralizing determinant (PND). The sequence of this V3 loop raises the question of the immunogenicity and the degree of diversity of the antibody response to the PND. We show here that this neutralization-related motif is highly immunogenic in HIV-positive subjects and in experimentally immunized primates and rodents submitted to various anti-HIV immunization regimens. In probing the diversity of the antibody response to PNDs corresponding to 11 HIV sequence-divergent isolates in serum samples of 101 HIV-positive individuals we found that human antibodies exhibit binding affinity to up to nine PND synthetic peptides. This antibody binding was in all cases tested inhibitable by the homologous PND synthetic peptide. We additionally demonstrate that this antibody cross-reactivity towards sequence-divergent PNDs is detectable in the sera of mice and chimpanzees experimentally immunized against a single HIV-1 isolate. Finally, we noticed that there is a hierarchy of reactivity among the various PNDs wherein the synthetic peptide corresponding to the MN isolate was generally the most prominently recognized by antibodies of human, non-human primate, and rodent origins. Based on these findings and on features of the sequences analyzed we suggest that, despite its overall sequence variability, the PND encompasses conserved amino acid positions or epitopes that are the targets of antibodies recognizing sequence-divergent isolates. We also propose that the high positive charge density of the most frequently recognized PNDs and the high antigenicity value of some of their residues are critical to the broad immunoreactivity of this neutralization-related motif.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Idiotypic expression of anti-gp120 antibodies in unrelated human immunodeficiency virus-infected individuals.

Although it is recognized that human immunodeficiency virus (HIV) env genes exhibit a high degree of variability, little is known about the molecular heterogeneity of gp120-specific antibodies in infected individuals. As a first step to approach this issue, we investigated the idiotypic relatedness of anti-gp120 antibodies present in the serum of HIV-infected individuals. Idiotypic determinants (idiotopes) are fingerprints of the variable region of the antibody molecule and, as such, they represent unique probes with which to explore the diversity of the immune response. We isolated IgG anti-gp120 antibodies from the serum of a seropositive asymptomatic individual by affinity chromatography. The purified antibodies were shown to bind gp120 and gp160 by ELISA, Western blotting and radio-immunoprecipitation. They also recognized HIV-infected human T cells as detected by immunofluorescence. Anti-idiotypic reagents were generated against this gp120 idiotype, and one of them was used to study anti-gp120 idiotypic diversity in a panel of 65 sera drawn from AIDS and AIDS-related complex patients, and from HIV seropositive asymptomatic individuals. Sixty normal human sera were used as negative controls. We found no evidence for common idiotopes on anti-gp120 antibodies of unrelated individuals. In contrast, we also noticed that the idiotypic profile expressed sequentially at two different intervals in a persistently infected individual showed little variation. Finally, when the diversity of murine anti-gp120 antibodies with a monoclonal anti-idiotype was analysed, no evidence of cross-reactive idiotopes in the murine system was found.

Adult↗
PubMed1992

Monomorphic organization of human diversity (DH) heavy chain variable genes.

While recent evidence indicates that human immunoglobulin heavy chain variable (VH) genes exhibit a high degree of heterogeneity, little is known concerning the polymorphism of the diversity (DH) gene complex. This locus comprises two clusters, major and minor, which are physically linked with the VH locus. In assessing the variability of the human major and minor DH clusters, we found no evidence for a substantial restriction site polymorphism. We also noted that, in contrast to what was found in the Japanese population, the DH1 gene is not deleted in an appreciable proportion of the European population. We propose that, because DH genes impart the critical functions associated with the third complementarity-determining region, the genomic organization of the human DH locus has been evolutionarily conserved through selection pressure mechanisms.

Antibody Diversity↗
PubMed1991

UV-treated polystyrene microtitre plates for use in an ELISA to measure antibodies against synthetic peptides.

Detection of peptide-specific antibodies by the conventional ELISA technique is sometimes hampered by the difficulties encountered in immobilizing stretches of amino acids on the solid support. To improve the attachment of synthetic peptides to the solid phase, we have developed a sensitive and rapid immunoassay based on the irradiation of polystyrene plates with UV light prior to coating the target peptide. This pretreatment increases the specific signal in a dose-dependent manner without augmenting the background or altering the specificity of the assay. This simple method was shown to be suitable for the quantitation of murine monoclonal antibodies as well as human and rabbit polyclonal antibodies. It should be applicable to a variety of synthetic peptides and polystyrene ELISA plates. Using this technique, we were able to localize the antigenic motifs recognized by neutralizing monoclonal antibodies generated against the envelope protein gp120 of the human immunodeficiency virus.

Amino Acid Sequence↗
PubMed1991

Cloning of a gene encoding a lupus-associated human autoantibody VK region using the polymerase chain reaction and degenerate primers.

The variable light-chain-encoding gene of a human autoantibody secreted by a B-cell hybridoma derived from a patient with systemic lupus erythematosus was amplified using the polymerase chain reaction and degenerate primers. After cloning, the nucleotide sequence of the EcoRI-HindIII region was determined. It is highly homologous to a previously described gene expressed by a human lymphoid cell line.

Autoantibodies↗
PubMed1991

Probing VH gene-family utilization in human peripheral B cells by in situ hybridization.

Recent studies on the genomic organization of the human Ig VH locus have revealed the presence of an important proportion of VH pseudogenes and a high degree of interspersion among VH gene-family members. The mechanisms of selection of VH genes expressed by differentiating B cells remain to be elucidated. We have made use of RNA-RNA in situ hybridization to probe the repertoire of VH gene-families assembled in peripheral B cells of normal adults. Cells were in vitro activated with mitogens and then hybridized to [35S]-labeled anti-sense RNA probes specific for C mu and C gamma genes, and for the six known human VH gene-families. We found that the numbers of cells expressing C mu and C gamma mRNA were similar to the total numbers of cells expressing members of the six VH gene-families. Therefore, the six known VH gene-families represent essentially the human VH locus. We also found that expression of VH gene-families does not closely correlate with their relative genomic complexity. This apparently biased expression may suggest that in some VH gene-families the ratio of pseudogenes/functional genes is particularly high, and/or that regulatory mechanisms play a major role in shaping the available VH gene repertoire in differentiating B cells.

Antibody Specificity↗
PubMed1991

Anti-idiotypic antibodies to human anti-gp120 antibodies bind recombinant and cellular human CD4.

The presence of anti-CD4 antibodies in sera of human immunodeficiency virus (HIV)-seropositive individuals has been recently documented, but its origin remains unknown. To test the hypothesis that anti-idiotypic antibodies to gp120, the HIV envelope glycoprotein with high affinity for CD4, mimic the configuration of gp120 and bind CD4, we performed two sets of experiments. First, we tested the possibility that anti-CD4 antibodies present in sera of a proportion of HIV-positive individuals exhibit variable region complementarity to autologous anti-gp120 antibodies. We show here that affinity-purified human anti-gp160 antibodies recognize specifically autologous affinity-purified anti-CD4 antibodies. We also demonstrate that antibodies to CD4 competitively inhibit anti-gp160 autologous antibodies binding to gp160. This implies that at least some anti-CD4 antibodies are directed towards idiotypic motifs located on anti-gp120 antibodies and that they may result from an anti-idiotypic response to anti-gp120 antibodies. In a second set of experiments, we examined the effect of anti-idiotypic immunization of experimental animals against human anti-gp120 antibodies. We found that anti-idiotypic antibodies produced in a rabbit immunized against affinity-purified human anti-gp120 antibodies specifically recognize recombinant and cellular human CD4, and that this interaction is competitively inhibited by soluble CD4. The data support the concept of idiotypic mimicry whereby anti-idiotypic antibodies produced against anti-gp120 antibodies recognize CD4, the cellular receptor of HIV.

Antibodies, Anti-Idiotypic↗
PubMed1991

Quantitative clonal analysis of the B cell repertoire in human lupus.

To gain further insight into the origin of autoantibody hyperproduction in human lupus, we quantitated the B cell repertoire toward exogenous and self-antigens. Using the Spot-ELISA method and two panels of nine exogenous and 10 self-antigens, we found that the normal human immune repertoire comprises a high frequency of B cell precursors secreting IgM antibodies to self- and exogenous determinants. This repertoire was markedly deficient in precursors producing IgG able to bind self-antigens. In lupus patients, the absolute numbers of clone precursors of the immune repertoire expressing IgM receptors whose paratopes impart affinity to self- and exogenous determinants were higher than in control individuals. Additionally, IgG antibody-forming cell precursors with binding specificity for lupus-associated antigens were detectable in the repertoire of these patients. Based on these results, we propose that hyperproduction of human lupus-associated autoantibodies arises in a two-stage mechanism whereby a general activation of the multireactive immune B cell repertoire precedes an oligospecific expansion of selected B cell clonotypes.

Antibodies, Antinuclear↗
PubMed1989

Restriction fragment length polymorphism analysis of the V kappa locus in human lupus.

To evaluate the degree of genetic polymorphism of the V kappa repertoire in systemic lupus erythematosus (SLE), we performed Southern blot hybridizations with human gene probes corresponding to the four human V kappa gene families. In a comparative analysis, non-lymphoid cell DNA samples from three patients with idiopathic SLE, eight subjects with susceptibility to drug-induced lupus and seven control individuals were digested with the restriction endonucleases Bam HI, Bg 1 II, Eco RI and Hind III, and hybridized sequentially to the four V kappa family-specific probes. The restriction patterns on Southern blots revealed a low degree of polymorphism of the human V kappa gene repertoires of SLE patients and control individuals. This analysis, together with previous parallel studies of the V kappa locus in lupus-prone mice, implies that autoantibody hyperproduction in lupus is not associated with major modifications in the structure or genomic organization of immunoglobulin light chain genes.

Antipsychotic Agents↗