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D Couez

Publications and source records attributed to D Couez.

At least 19 recordsLinked to original sources
PubMed1992

Role of CD3 delta in surface expression of the TCR/CD3 complex and in activation for killing analyzed with a CD3 delta-negative cytotoxic T lymphocyte variant.

The TCR is composed of two chains (alpha/beta) containing variable regions associated at the cell surface with invariant chains (CD3 gamma-, delta-, epsilon-, and zeta/eta chains). The latter control assembly and surface expression of the TCR/CD3 complex, as well as its cytoplasmic association with signal transduction relays. In differentiated CTL, stimulation through the TCR leads to the transcriptional activation of genes coding secreted cytokines such as gamma-IFN as well as transcription-independent activation of the lytic machinery. It is not known which of the CD3 components is necessary to transduce the required signals. CD3 gamma- and delta-chains have high sequence homology, in particular in their cytoplasmic domain, and it has been proposed that alpha beta gamma epsilon zeta and alpha beta delta, epsilon zeta may be expressed and function in signal transduction independently. Here, we characterize a CTL clone that has selectively lost expression of the CD3 delta mRNA. This results in expression of partial CD3 complexes devoid of TCR alpha beta chains at the surface of the clone, which are not functional for activation of cytolysis or for gamma-IFN production. Transfection of the clone with either the native or a cytoplasmic exon-deleted CD3 delta gene restores full TCR/CD3 surface expression as well as Ag- or CD3-mediated activation for killing and for gamma-IFN production, indicating that the CD3 delta chain is essential for surface expression of the TCR alpha beta, but that the CD3 delta cytoplasmic portion is not required either for complex assembly or for signal transduction involved in the functions studied.

Amino Acid Sequence↗
PubMed1992

The interferon- and virus-inducible IFI-56K and IFI-54K genes are located on human chromosome 10 at bands q23-q24.

IFI-56K and IFI-54K are two human genes that are strongly induced by interferon and viruses. These genes are closely related at the protein, RNA, and promoter levels. By means of the somatic cell hybrid technique, the two genes have been previously located on chromosome 10. Using in situ hybridization, we show here that both IFI-54K and IFI-56K genes map to 10q23-q24. This result does not confirm the previous localization of the IFI-56K gene at the junction of the 10q25 and 10q26 bands.

Chromosome Banding↗
PubMed1991

Each of the two productive T cell receptor alpha-gene rearrangements found in both the A10 and BM 3.3 T cell clones give rise to an alpha chain which can contribute to the constitution of a surface-expressed alpha beta dimer.

The H-2 Kb specific cytotoxic T cell clone BM3.3 carries two productive TCR alpha gene rearrangements but expresses a single detectable TCR alpha beta chain combination on its surface. However, when separately analyzed by gene transfer, both productive alpha gene rearrangements are translated into alpha chains capable of pairing with the BM3.3 beta chain and of cell surface expression. Similar observations have been made with the products of the two productive alpha gene rearrangements previously identified in the A10 T cell clone. These observations contrast with those made for the two TCR alpha chains expressed in the MS202 T cell clone. In the latter instance, when analyzed by gene transfer, one of the alpha chains was unable to make a pair with the beta chain. Consequently, when considered with respect to the mechanisms of TCR allelic exclusion, our data suggest that the mere expression of a TCR alpha beta dimer on the surface of immature CD4+ CD8+ thymocytes may be necessary but not sufficient to shutdown further alpha gene rearrangements. Rather, the ability of a TCR alpha beta dimer to be positively selected may be needed to trigger the maturation of thymocytes to a stage devoid of recombinase activity. Alternatively, if non-dividing CD4+ CD8+ CD3+ small thymocytes do not experience secondary alpha-gene rearrangement, our data suggest that TCR alpha gene rearrangements are attempted quasi-simultaneously on both alpha alleles.

Alleles↗
PubMed1990

A novel type of aberrant T cell receptor alpha-chain gene rearrangement. Implications for allelic exclusion and the V-J recombination process.

In the process of analyzing the contribution of nonproductive alpha- and beta-chain gene rearrangements to the allelic exclusion of TCR gene expression, we have found a novel type of aberrant alpha-gene rearrangement. In one alpha-allele of the mouse KB5-C20 T cell clone, a J alpha gene segment has been abutted precisely to a sequence that does not display any homology to known V and D gene segment. The appended sequence originates from within the V alpha locus and is located, in the germ-line, 1 kb upstream of a member of the V alpha 2-gene segment subfamily. No recombination signal sequences have been found contiguous to the recombination point. These observations indicate that in normal T lymphocytes, TCR alpha-genes may be affected by aberrant rearrangements similar to those that predominate in human T cell tumors containing chromosome 14 inversion or translocation. Furthermore, compilation of published data and cloning and sequencing of three additional alpha-alleles has allowed us to examine the status of alpha-loci in nine mouse T cell clones expressing functional alpha beta-heterodimers. Interestingly, in contrast to the situation observed at the beta-locus, only 1 of 18 analyzed alpha-alleles has retained a germ-line unrearranged configuration. In addition, in each T cell clone, alpha-rearrangements on homologous chromosomes were unevenly distributed over the J alpha region and shown to generally involve neighboring J alpha gene segments.

Alleles↗
PubMed1990

Human CD28 and CTLA-4 Ig superfamily genes are located on chromosome 2 at bands q33-q34.

CD28 is a cell surface molecule present on most peripheral T cells which has been implied in the amplification of the T-cell response in vitro. Using in situ hybridization on human prometaphase cells, we have found that the human CD28 gene maps to chromosome 2 at bands q33-q34, as shown previously for the CTLA-4 gene. CD28 and CTLA-4 are both members of the Ig superfamily, where they define a subgroup of membrane-bound single V domains. Their chromosomal proximity and their close structural relationship suggest that these two genes could be the result of the duplication of a common evolutionary precursor and may share some functional properties.

Antigens, CD↗
PubMed1990

Sequence variability of bovine leukemia virus env gene and its relevance to the structure and antigenicity of the glycoproteins.

The nucleotide sequences of the env genes of seven bovine leukemia viruses and the encoded peptide sequence were compared, with the objective of (i) determining the genetic distance separating bovine leukemia virus isolates from different geographical regions, (ii) identifying particular amino acids that contribute to the sequential and conformational epitopes, and (iii) relating such epitopes to their projected position in a three-dimensional model of the structure of the gp51 surface glycoprotein. Two bovine leukemia virus subgroups were clearly identified, a Japanese-American subgroup represented by strains lambda BLV-1, VdM, and FLK-BLV and a European subgroup by strains T15-2, LB285, and LB59. It was possible to identify amino acids that were important in determining three of the epitopes (F, G, and H) recognized by neutralizing monoclonal and polyclonal antibodies. On the model, these epitopes were adjacent and located on the exposed region of the molecule. Amino acid sequences contributing to a fourth cryptic epitope were identified; as predicted by the model, they lay on the opposite side to the neutralizable epitopes in a region involved in glycoprotein subunit association. The fact that this region is not normally exposed on the virion surface provides further evidence for the validity of the model.

Amino Acid Sequence↗
PubMed1989

Visualizing interleukin 2 gene expression at the single cell level.

To analyze the expression of the interleukin (IL)2 gene at the single cell level, we have constructed a chimeric gene in which the regulatory sequences from the mouse IL2 gene were fused 5' proximal to the coding region of the Escherichia coli beta-galactosidase (lacZ) gene. Once stably introduced into a T cell hybridoma, the IL 2-lacZ reporter gene was shown to display a pattern of induction similar to the one observed for the resident IL 2 gene. Two points emerged from monitoring IL 2 expression for the resident IL2 gene. Two points emerged from monitoring IL 2 expression at the single cell level. First, upon activation the expression of the IL2-lacZ gene appears asynchronous. Second, at the peak of induction the percentage of beta-galactosidase+ cells never reached 100% and the level of beta-galactosidase reached among positive cells was highly heterogeneous within a cloned population of T cells. In combination with the possibility to sort viable lymphocytes according to lacZ expression, the IL2-lacZ reporter gene described herein should provide a way to isolate somatic cell mutants deficient in signal transduction by the T cell antigen receptor complex.

Animals↗
PubMed1989

Complexity, polymorphism, and recombination of mouse T-cell receptor alpha gene families.

Genomic DNA from a large panel of inbred strains of mice were hybridized sequentially with 15 V alpha, 2 V delta, 1 C alpha, and 1 C delta probes. Most of the V alpha probes detected a high degree of polymorphism and have allowed the definition of five mouse T-cell receptor alpha (Tcr alpha) haplotypes. One of these haplotypes (Tcre alpha) appears to arise from a recombination between the Tcrb alpha and Tcra alpha haplotypes, the latter being the most frequently found in the conventional inbred strains. This recombination event clearly indicates that the members of at least 11 V alpha sub-families are not closely linked but highly interspersed with one another on chromosome 14.

Animals↗
PubMed1989

Antigenic variants of bovine leukemia virus (BLV) are defined by amino acid substitutions in the NH2 part of the envelope glycoprotein gp51.

Previous studies with monoclonal antibodies of the antigenic structure of bovine leukemia virus (BLV) envelope glycoprotein (gp51) have identified three epitopes (F, G, H) directly involved in the infectivity of BLV, F, G, and H lost their reactivity with the respective monoclonal antibodies after treatment with a reducing agent, indicating that these epitopes were conformational. Sequence comparisons between BLV mutants and differential reactivities of urokinase or proteinase K gp51 fragments with monoclonal antibodies indicated that the NH2 moiety of the env protein harbored the three architectural determinants F, G, and H. ELISA tests demonstrated that anti-F, -G, and -H monoclonal antibodies were maximally reactive toward intact virions whereas they showed much poorer affinities for their respective epitopes when presented on a purified protein. Accordingly, an efficient vaccine against BLV infection will include at least the identified gp51 region presented in its native architectural configuration.

Amino Acid Sequence↗
PubMed1985

Bovine leukemia virus, a versatile agent with various pathogenic effects in various animal species.

The bovine leukemia virus is the etiological agent of a chronic lymphatic leukemia in cows, sheep, and goats. The same virus seems to induce a kind of wasting disease in experimentally infected rabbits. Antibodies to highly purified bovine leukemia viral Mr 51,000 glycoprotein and Mr 24,000 protein cross-react with human T-lymphotropic virus III/lymphadenopathy-associated virus antigens present in cultured lymphocytes of African patients suffering from acquired immune deficiency syndrome. Bovine leukemia virus has many structural and functional characteristics in common with the human T-lymphotropic viruses. The most striking feature of these retroviruses is the existence of a long open reading frame located at the 3' side of the provirus between the right end of the 3' side of env gene and the left end of the long terminal repeat. It is believed that the long open reading frame protein product acts in trans upon a number of genes to account for the biological effects of the virus.

Animals↗
PubMed1985

Bovine leukaemia virus and enzootic bovine leukosis.

Infection of bovines with bovine leukaemia virus (BLV) manifests itself in either of two ways: 30-70% of carriers develop persistent lymphocytosis (PL), with the viral genome integrated at a large number of different sites in the DNA of the affected B-lymphocytes, without causing any chromosomal abnormalities. Only 0,1-10% of carriers develop lymphoid tumours, which also consist of B-lymphocytes. In contrast to PL, however, they are of mono- or oligoclonal origin in terms of the integration site, which is characteristic for each tumour. All cells contain one or more copies of the viral genome, chromosomal aberrations are common and if deletions are present they are invariably found in the 5'-half of the virus DNA sequence. In both types of affected cells transcription is repressed in vivo, but transient virus production can be induced in vitro and detected by means of syncytia induction or haemagglutination. In vivo production of virus in some unknown cell is suggested by the presence of high antibody titres in infected animals, especially against the envelope glycoprotein gp51. This can be detected by various techniques such as immunodiffusion, radioimmune assay or ELISA. Monoclonal antibodies against gp51 have revealed 8 epitopes, 3 of which are recognized by neutralizing antibodies and one by a cytolytic antibody. The BLV genome, about 9 kb in size, have been cloned, and some of the information obtained on its molecular structure and function is discussed. It codes for at least 4 non-glycosylated and 2 glycoproteins. Of special interest is the recently discovered serological relationship between some of the non-glycosylated proteins and those of the human T-cell leukaemia virus. The functional role of BLV in leukaemogenesis is largely unknown. The presence of the viral genome seems to be necessary for the maintenance of the transformed state, but not its continuous expression nor an LTR-mediated promotion of transcription of cellular genes. No oncogene is carried by the virus. Although bovine leukosis is not of major economic importance, its eradication is desirable and feasible in countries with a relatively low incidence, by means of testing and elimination. For endemic situations vaccination would be preferable, and distinct possibilities exist for the development of gp51 based vaccines.

Animals↗
PubMed1984

The nucleotide sequence of the env gene and post-env region of bovine leukemia virus.

The env gene of a bovine leukemia virus (BLV) tumor-derived proviral DNA clone has been located by comparison of the translated DNA sequence with amino acid sequence data on purified gp60 and p30env (A. M. Schultz, T. D. Copeland, and S. Oroszlan (1984) Virology 135, 417-427). There is a continuous open reading frame from the N terminus of gp60 for 1446 nucleotides; gp60 is predicted to contain 268 amino acids and p30env, 214. The predicted p30env shows structural features typical of type C viral transmembrane proteins. It is also clearly related to that of the human T-cell leukemia virus (HTLV), as predicted from the DNA sequence of Seiki et al. (M. Seiki, S. Hattori, Y. Hirayama, and M. Yoshida (1983) Proc. Natl. Acad. Sci. USA 80, 3618-3622) The two proteins show 36% identities in their amino acid sequence, in an alignment requiring six gaps. More distant relatedness is also seen between BLV p30env and both murine leukemia virus p15E and Rous sarcoma virus gp36. The gp60s of BLV and HTLV are more distantly related than their p30envs, but their homology is nonetheless statistically significant. Between the presumptive terminator of the env gene and the beginning of the 3'-long terminal repeat is a region of 1817 base pairs of unknown function. Just as in the HTLV post-envelope sequence, there are at least two reading frames which are open for a significant fraction of this region. In neither the tumor-derived clone nor a clone from a virus-producing cell line, however, is there a continuous open reading frame throughout the region. Comparison of the BLV and HTLV sequences within the post-envelope region revealed a very limited but possibly significant similarity.

Amino Acid Sequence↗
PubMed1984

Nucleotide sequence analysis of the long terminal repeat of integrated bovine leukemia provirus DNA and of adjacent viral and host sequences.

The nucleotide sequence of the 3' long terminal repeat and adjacent viral and host sequences was determined for a bovine leukemia provirus cloned from a bovine tumor. The long terminal repeat was found to comprise 535 nucleotides and to harbor at both ends an imperfect inverted repeat of 7 bases. Promoter-like sequences (Hogness box and CAT box), an mRNA capping site, and a core enhancer-related sequence were tentatively located. No kinship was detected between this bovine leukemia proviral fragment and other retroviral long terminal repeats, including that of human T-cell leukemia virus.

Animals↗
PubMed1984

Different bovine leukemia virus-induced tumors harbor the provirus in different chromosomes.

DNAs from 25 independent hamster X bovine somatic cell hybrids were submitted to the Southern blot analysis with probes made of unique cellular fragments adjacent to single-copy proviruses from three different bovine tumors. It appeared that these cellular sequences, and thus the respective proviruses, belonged to three different chromosomes in the three different tumors examined.

Animals↗
PubMed1984

Bovine leukemia virus, a distinguished member of the human T-lymphotropic virus family.

Bovine leukemia virus (BLV) has many structural and functional characteristics in common with the human T-lymphotropic viruses (HTLVs). The most striking feature of these retroviruses is the existence of a long open reading frame (LOR) located at the 3' side of the provirus between the right end of the 3' side of env gene and the left end of the long terminal repeat (LTR). It is believed that the LOR protein product is of critical importance in the induction process of the tumor phase of bovine leukemia. Prevention of BLV infection will be attempted by vaccination. To that aim, careful study of BLV envelope glycoprotein epitopes has shown that epitopes F, G, and H play a major role in biological activities of the virus. Their native structure depends upon glycosylation of the peptide backbone.

Animals↗
PubMed1984

[Oncogenes].

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Animals↗