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Biomedical subjects

F A Lemonnier

Publications and source records attributed to F A Lemonnier.

At least 37 records · Page 2Linked to original sources
PubMed1999

Phenotypical and functional characterization of the CD8+ T cell repertoire of HLA-A2.1 transgenic, H-2KbnullDbnull double knockout mice.

Homozygous HLA-A2.1 transgenic H-2KbnullDbnull double knockout (KO) mice were created. Their potential to develop HLA-A2. 1-restricted cytolytic responses was compared with that of their classical transgenic counterparts, which still express H-2Kb, Db molecules. On cell surfaces, both strains express similar amounts of chimeric (alpha 1 alpha 2 domains of human, alpha 3 cytoplasmic domains of mouse) HLA-A2.1 molecules in noncovalent association with mouse beta 2-microglobulin. Compared with mice that are totally deprived of histocompatibility class Ia molecules (H-2KbnullDbnull double KO), the expression of HLA-A2.1 in transgenic/double KO mice resulted in sizeable increase in the periphery of CD8+ T cells with a normally diversified TCR repertoire. A biased education in favor of HLA-A2.1, ascribable to the absence of H-2 class Ia molecules, was evidenced in these transgenic/double KO mice by their improved capacity to mount HLA-restricted cytolytic responses, regardless of whether they were virally infected or injected with synthetic epitopic peptide. HLA class I transgenic, H-2 class Ia KO mice should represent useful animal models for the preclinical evaluation of vaccine formulations aiming at the induction of HLA class I-restricted CTL responses.

Animals↗
PubMed1999

Cutting edge: expression of functional CD94/NKG2A inhibitory receptors on fetal NK1.1+Ly-49- cells: a possible mechanism of tolerance during NK cell development.

Fetal liver- and thymus-derived NK1.1+ cells do not express known Ly-49 receptors. Despite the absence of Ly-49 inhibitory receptors, fetal and neonatal NK1.1+Ly-49- cells can distinguish between class Ihigh and class Ilow target cells, suggesting the existence of other class I-specific inhibitory receptors. We demonstrate that fetal NK1. 1+Ly-49- cell lysates contain CD94 protein and that a significant proportion of fetal NK cells are bound by Qa1b tetramers. Fetal and adult NK cells efficiently lyse lymphoblasts from Kb-/-Db-/- mice. Qa1b-specific peptides Qdm and HLA-CW4 leader peptide specifically inhibited the lysis of these blasts by adult and fetal NK cells. Qdm peptide also inhibited the lysis of Qa1b-transfected human 721.221 cells by fetal NK cells. Taken together, these results suggest that the CD94/NKG2A receptor complex is the major known inhibitory receptor for class I (Qa1b) molecules on developing fetal NK cells.

Aging↗
PubMed1999

Response to Listeria monocytogenes in mice lacking MHC class Ia molecules.

MHC class Ia-deficient mice (H2 Kb-/- Db-/-) inoculated with the intracellular pathogen Listeria monocytogenes (LM) displayed a three- to fourfold expansion of splenic CD8+ T cells 6 days following infection. Culture of these spleen cells in vitro gave rise to CTL that recognized LM-infected target cells and were restricted by the class Ib molecules, Qa1b and M3. Exposure of target cells to heat-killed LM (HKLM) rather than live bacteria did not result in CTL-mediated lysis. Target cells pulsed with three LM peptides known to bind M3, f-MIGWII, f-MIVTLF, and f-MIVIL, were recognized by effector cells from both B6 and Kb-/- Db-/- animals. In vivo analysis showed that B6 and Kb-/- Db-/- mice clear LM from the spleen and liver rapidly with similar kinetics, whereas TAP.1-/- mice, which are deficient in class Ia and Ib molecules, clear LM slowly upon infection. To establish the in vivo role of CD8+ T cells in Kb-/- Db-/- animals, we showed that depletion of such cells from the spleens of immune mice prevented the adoptive transfer of protective immunity to syngeneic recipients. Spleen cells from Kb-/- Db-/- mice were also capable of generating responses directed against syngeneic as well as allogeneic class Ia molecules in vitro. Thus, class Ia-deficient animals have a CD8+ T cell repertoire capable of recognizing both class Ia and class Ib molecules and can generate protective immunity to LM.

Animals↗
PubMed1999

Single H2Kb, H2Db and double H2KbDb knockout mice: peripheral CD8+ T cell repertoire and anti-lymphocytic choriomeningitis virus cytolytic responses.

Single H2Kb, H2Db and double H2KbDb homozygous knockout (KO) mice were generated and their peripheral CD8+ T cell repertoires compared to that of C57BL/6 (B6) mice. Limited (10-20%, H2Db), substantial (30-50%, H2Kb) and profound (90%, H2KbDb) reduction of peripheral CD8+ T cells was observed in KO mice, without Vbeta diversity alteration. Classical class Ia molecules therefore ensure most but not all of the peripheral CD8+ T cell repertoire education. As expected, H2Kb but also H2Db KO mice developed choriomeningitis following intracranial infection by lymphocytic choriomeningitis virus with the same kinetics, lethality and CD8+ cell implication as wild-type B6 mice. By contrast, H2KbDb (class Ia-Ib+) KO mice survived. Choriomeningitis of H2Db KO mice was linked to the development of a subdominant (in normal B6 mice) H2Kb-restricted cytotoxic T lymphocyte response. Mice expressing a restricted set of histocompatibility class I molecules should represent useful tools to evaluate the immunological potentials of individual MHC class I molecules.

Animals↗
PubMed1999

H-2 class I knockout, HLA-A2.1-transgenic mice: a versatile animal model for preclinical evaluation of antitumor immunotherapeutic strategies.

H-2 class I-negative, HLA-A2.1-transgenic HHD mice were used for a comparative evaluation of the immunogenicity of HLA-A2.1-restricted human tumor-associated cytotoxic T lymphocyte (CTL) epitopes. A hierarchy was established among these peptides injected into mice in incomplete Freund's adjuvant which correlates globally with their capacity to bind and stabilize HLA-A2.1 molecules. Co-injection of a helper peptide enhanced most CTL responses. In contrast, classical HLA class I-transgenic mice which still express their own class I molecules did not, in most cases, develop HLA-A2.1-restricted CTL responses under the same experimental conditions. Different monoepitope immunization strategies of acceptable clinical usage were compared in HHD mice. Recombinant Ty-virus-like particles, or DNA encoding epitopes fused to the hepatitis B virus middle envelope protein gave the best results. Using this latter approach and a melanoma-based polyepitope construct, CTL responses against five distinct epitopes could be elicited simultaneously in a single animal. Thus, HHD mice provide a versatile animal model for preclinical evaluation of peptide-based cancer immunotherapy.

Amino Acid Sequence↗
PubMed1999

MHC class Ia molecules alone control NK-mediated bone marrow graft rejection.

Mice with functionally deleted genes encoding MHC class I heavy (H-2K(b), H-2D(b)) and light (beta2-microglobulin) chains were used in bone marrow cell transfer experiments to study the role of class Ia and Ib molecules in NK cell function. Absence of H-2K(b) and absence of H-2D(b) on bone marrow cells resulted in complete and in almost complete NK-mediated rejection, respectively. Absence of either H-2 class Ib (at least when expressed in H-2 class Ia-deficient mice) or cell surface class Ia free heavy chains did not result in bone marrow rejection. Thus, in C57BL/6 adult mice, the inactivation of NK cells required for bone marrow cell engraftment relies entirely upon-H-2 class Ia molecules. These results imply the existence of an inhibitory receptor which recognizes either directly or indirectly H-2D(b) molecules and further suggest that in C57BL/6 mice the NK cells which do not express a H-2K(b) specific inhibitory receptor necessarily express an H-2D(b)-specific one.

Animals↗
PubMed1999

Direct assessment of MHC class I binding by seven Ly49 inhibitory NK cell receptors.

Mouse NK cells express at least seven inhibitory Ly49 receptors. Here we employ a semiquantitative cell-cell adhesion assay as well as class I/peptide tetramers to provide a comprehensive analysis of specificities of Ly49 receptors for class I MHC molecules in eight MHC haplotypes. Different Ly49 receptors exhibited diverse binding properties. The degree of class I binding was related to the extent of functional inhibition. The tetramer studies demonstrated that neither glycosylation nor coreceptors were necessary for class I binding to Ly49 receptors and uncovered peptide-specific recognition by a Ly49 receptor. The results provide a foundation for interpreting and integrating many existing functional studies as well as for designing tests of NK cell development and self-tolerance.

Alleles↗
PubMed1999

Immunogenicity of a human immunodeficiency virus (HIV) polytope vaccine containing multiple HLA A2 HIV CD8(+) cytotoxic T-cell epitopes.

Compelling evidence now suggests that alphabeta CD8 cytotoxic T lymphocytes (CTL) have an important role in preventing human immunodeficiency virus (HIV) infection and/or slowing progression to AIDS. Here, we describe an HIV type 1 CTL polyepitope, or polytope, vaccine comprising seven contiguous minimal HLA A2-restricted CD8 CTL epitopes conjoined in a single artificial construct. Epitope-specific CTL lines derived from HIV-infected individuals were able to recognize every epitope within the construct, and HLA A2-transgenic mice immunized with a recombinant virus vaccine coding for the HIV polytope also generated CTL specific for different epitopes. Each epitope in the polytope construct was therefore processed and presented, illustrating the feasibility of the polytope approach for HIV vaccine design. By simultaneously inducing CTL specific for different epitopes, an HIV polytope vaccine might generate activity against multiple challenge isolates and/or preempt the formation of CTL escape mutants.

AIDS Vaccines↗
PubMed1998

Major histocompatibility complex (MHC) class I KbDb -/- deficient mice possess functional CD8+ T cells and natural killer cells.

We obtained mice deficient for major histocompatibility complex (MHC) molecules encoded by the H-2K and H-2D genes. H-2 KbDb -/- mice express no detectable classical MHC class I-region associated (Ia) heavy chains, although beta2-microglobulin and the nonclassical class Ib proteins examined are expressed normally. KbDb -/- mice have greatly reduced numbers of mature CD8+ T cells, indicating that selection of the vast majority (>90%) of CD8+ T cells cannot be compensated for by beta2-microglobulin-associated molecules other than classical H-2K and D locus products. In accord with the greatly reduced number of CD8+ T cells, spleen cells from KbDb -/- mice do not generate cytotoxic responses in primary mixed-lymphocyte cultures against MHC-disparate (allogeneic) cells. However, in vivo priming of KbDb -/- mice with allogeneic cells resulted in strong CD8+ MHC class Ia-specific allogeneic responses. Thus, a minor population of functionally competent peripheral CD8+ T cells capable of strong cytotoxic activity arises in the complete absence of classical MHC class Ia molecules. KbDb -/- animals also have natural killer cells that retain their cytotoxic potential.

Animals↗
PubMed1998

Modulation of thymic selection by expression of an immediate-early gene, early growth response 1 (Egr-1).

The potential involvement of early growth response (Egr)-1, a zinc-finger transcription factor belonging to the immediate-early genes, in positive/negative selection of thymocytes has been implicated by its expression in the population of CD4(+)CD8(+) double positive (DP) cells undergoing selection. To further investigate this possibility, transgenic mice overexpressing Egr-1 in thymocytes were bred with a transgenic mouse line expressing a T cell receptor (TCR) recognizing the H-Y male antigen in the context of H-2(b) class I major histocompatibility complex (MHC) molecules. In Egr-1/TCR H-Y double-transgenic mice, efficient positive selection of H-Y CD8(+) T cells occurred, even in mice on either a nonselecting H-2(d) background or a beta2-microglobulin (beta2m)-deficient background in which the expression of class I MHC heavy chains is extremely low; no positive selection was observed on a Kb-/-Db-/-beta2m-/- background where class I MHC expression is entirely absent. Similarly, when the Egr-1 transgene was introduced into a class II MHC-restricted TCR transgenic mouse line, Egr-1/TCR double-transgenic mice revealed increased numbers of CD4(+) T cells selected by class II MHC, as well as significant numbers of CD8(+) T cells selected by class I MHC (for which the transgenic TCR might have weak affinity). Thus, Egr-1 overexpression allows positive selection of thymocytes via TCR-MHC interactions of unusually low avidity, possibly by lowering the threshold of avidity required for positive selection. Supporting this possibility, increased numbers of alloreactive T cells were positively selected in Egr-1 transgenic mice, resulting in a strikingly enhanced response against allo-MHC. These results suggest that expression of Egr-1 and/or its target gene(s) may directly influence the thresholds required for thymocyte selection.

Animals↗
PubMed1998

Cytotoxic T cell response against the chimeric p210 BCR-ABL protein in patients with chronic myelogenous leukemia.

Human chronic myelogenous leukemia (CML) is characterized by a translocation between chromosomes 9 and 22 that results in a BCR-ABL fusion gene coding for chimeric proteins. The junctional region of the BCR-ABLb3a2 molecule represents a potential leukemia-specific antigen which could be recognized by cytotoxic T lymphocytes (CTL). In fact, we identified a junctional nonapeptide (SSKALQRPV) which binds to HLA-A2.1 molecules. This peptide, as well as those binding to HLA-A3, -A11, and -B8 molecules (previously identified by others), elicits primary CTL responses in vitro from PBLs of both healthy donors and CML patients. Such CTL recognize HLA-matched, BCR-ABL-positive leukemic cells, implying efficient natural processing and presentation of these junctional peptides. Specific CTL were found at high frequency in 5 of 21 CML patients, suggesting that these epitopes are, to some extent, immunogenic in vivo during the course of the disease. These peptides could be useful for the development of specific immunotherapy in CML patients.

Binding, Competitive↗
PubMed1997

Differential requirements for survival and proliferation of CD8 naïve or memory T cells.

The requisite molecular interactions for CD8 T cell memory were determined by comparison of monoclonal naïve and memory CD8(+) T cells bearing the T cell receptor (TCR) for the HY antigen. Naïve T cells required only the right major histocompatibility complex (MHC) class I-restricting molecule to survive; to expand, they also needed antigen. In contrast, for survival, memory cells did not require the restricting MHC allele, but needed only a nonspecific class I; for expansion the correct class I, but not antigen, was required. Thus, maintenance of CD8 T cell memory still required TCR-MHC class I interactions, but memory T cells may have a lower functional activation threshold that facilitates secondary responses.

Adoptive Transfer↗
PubMed1997

HLA-A2.1-restricted education and cytolytic activity of CD8(+) T lymphocytes from beta2 microglobulin (beta2m) HLA-A2.1 monochain transgenic H-2Db beta2m double knockout mice.

Three different HLA-A2.1 monochains were engineered in which either the human or mouse beta2-microglobulin (beta2m) is covalently linked to the NH2 terminus of the heavy chain by a 15- amino acid long peptide: HHH, entirely human, HHD, with the mouse H-2Db alpha3, transmembrane, and cytoplasmic domains, and MHD, homologous to HHD but linked to the mouse beta2mb. The cell surface expression and immunological capacities of the three monochains were compared with transfected cells, and the selected HHD construct was introduced by transgenesis in H-2Db-/- beta2m-/- double knockout mice. Expression of this monochain restores a sizable peripheral CD8(+) T cell repertoire essentially educated on the transgenic human molecule. Consequently, infected HHD, H-2Db-/- beta2m-/- mice generate only HLA-A2.1-restricted CD8(+) CTL responses against influenza A and vaccinia viruses. Interestingly, the CTL response to influenza A virus is mostly, if not exclusively, directed to the 58-66 matrix peptide which is the HLA-A2.1-restricted immunodominant epitope in humans. Such mice might constitute a versatile animal model for the study of HLA-A2.1-restricted CTL responses of vaccine interest.

Animals↗
PubMed1997

The diversity of antigen-specific TCR repertoires reflects the relative complexity of epitopes recognized.

Antigen-selected T cell receptor (TCR) repertoires vary in complexity from very limited to extremely diverse. We have previously characterized two different CD8 T cell responses, which are restricted by the same mouse major histocompatibility complex (MHC) class I molecule, H-2 Kd. The TCR repertoire in the response against a determinant from Plasmodium berghei circumsporozoite protein (PbCS; region 252-260) is very diverse, whereas TCRs expressed by clones specific for a determinant in region 170-179 of HLA-CW3 (human) MHC class I molecule show relatively limited structural diversity. We had already demonstrated that cytolytic T lymphocyte (CTL) clones specific for the PbCS peptide display diverse patterns of antigen recognition when tested with a series of single Ala-substituted PbCS peptides or mutant. H-2 Kd molecules. We now show that CW3-specific CTL clones display much less diverse patterns of recognition. Our earlier functional studies with synthetic peptide variants suggested that the optimal peptides recognized were 9 (or 8) residues long for PbCS and 10 residues long for CW3. We now present more direct evidence that the natural CW3 ligand is indeed a 10-mer. Our functional data together with molecular modeling suggest that the limited TCR repertoire selected during the CW3 response is not due to a paucity of available epitopes displayed at the surface of the CW3 peptide/Kd complex. We discuss other factors, such as the expression of similar self MHC peptide sequences, that might be involved in trimming this TCR repertoire.

Animals↗
PubMed1996

Introduction of exogenous antigens into the MHC class I processing and presentation pathway by Drosophila antennapedia homeodomain primes cytotoxic T cells in vivo.

The homeodomain of the Antennapedia molecule (AntpHD) spontaneously crosses cellular membranes and can be used to deliver up to 50 additional amino acids to the cytoplasm. We exploited this approach to deliver antigenic peptides to the MHC class I processing and presentation pathway. AntpHD-based fusion peptides expressing the 170-179 HLA-Cw3 CTL epitope (pCw3) were produced in bacteria. Incubation of these fusion peptides with H-2d target cells resulted in efficient delivery to the cytosol as indicated by protease resistance and confocal microscopy. Moreover, this introduction of an exogenous Ag resulted in sensitization of the cell to lysis by a CTL clone specific for the 170-179 HLA-Cw3-derived peptide. Sensitivity of the Ag processing to brefeldin A but not to chloroquine is consistent with the delivery of AntpHD fusion peptides to the conventional class I-associated processing pathway. Immunization of DBA/2 (H-2d) mice with AntpHD pCw3 fusion peptide in the presence of SDS primed H-2Kd-restricted HLA-Cw3-specific CTL. Similar results were obtained with AntpHD fusion peptides expressing the 147-156 influenza nucleoprotein peptide. The strategy outlined in this paper provides a new approach for introducing molecules into the MHC class I Ag-presenting pathway. This approach has clear relevance to the design of synthetic peptide-based vaccines.

Amino Acid Sequence↗
PubMed1995

Restriction of self-antigen presentation to cytolytic T lymphocytes by mouse peptide pumps.

Transport of an immunogenic self-peptide from the second domain of the mouse major histocompatibility complex (MHC) H-2Kd class I molecule is blocked at the TAP1-TAP2 peptide pump level due to its amino acid sequence and is not presented to cytolytic T lymphocytes (CTL). We demonstrate that first, TAP1-TAP2 pumps can restrict antigen presentation by selecting against internal peptide motifs which are not involved in peptide binding to MHC class I molecules. Second, some molecules targeted to the endoplasmic reticulum are processed for MHC class I presentation in the cytosol. Third, some abundantly expressed immunogenic self-peptides are cytosolically sequestered. The advantage for the host, in terms of the peripheral T cell repertoire is that the spared CTL can be used to recognize foreign antigens. It is, however, anticipated that this advantage will be exploited by pathogens to evade immune surveillance by similar strategies.

ATP-Binding Cassette Transporters↗
PubMed1993

Abrogation of H-2-restricted CTL responses and efficient recognition of HLA-A3 molecules in DBA/2 HLA/A24 responder mice.

DBA/2 (H-2d) HLA-B7 x human beta 2-microglobulin transgenic and DBA/2 nontransgenic mice stimulated by DBA/2 HLA-A3 x human beta 2-microglobulin transgenic mouse spleen cells developed potent H-2Kd restricted cytolytic responses with recognition of a peptide from the second domain of the HLA-A3 H chain. These H-2Kd-restricted responses obliterated, as a rule, cytolytic responses with direct recognition of the HLA-A3 molecules, even in HLA-B7 transgenic mice. These immunodominant H-2Kd-restricted responses could be abrogated in DBA/2 HLA-A24 mice because of cross-tolerance, the HLA-A3 derived-H-2Kd presented peptide being shared by several (including A24) HLA class I H chain allelic variants. Under such experimental circumstances, strong CTL responses with exclusive direct recognition of HLA-A3 molecules constantly developed. Further analysis of these responses in six DBA/2 HLA-A24 responder mice indicated that a large fraction of the mouse V beta and V alpha genes could be used to mount such CTL responses. Thus, by combining classical HLA class I transgenesis and selective destruction of H-2K and H-2D genes, it should be possible to derive useful strains of mice for the study of HLA class I-restricted CTL responses.

Animals↗