Biomedical subjects

Ellis L Reinherz

Publications and source records attributed to Ellis L Reinherz.

At least 37 records · Page 2Linked to original sources

PubMed2004

Peptide variants of viral CTL epitopes mediate positive selection and emigration of Ag-specific thymocytes in vivo.

During development, thymocytes carrying TCRs mediating low-affinity interactions with MHC-bound self-peptides are positively selected for export into the mature peripheral T lymphocyte pool. Thus, exogenous administration of certain altered peptide ligands (APL) with reduced TCR affinity relative to cognate Ags may provide a tool to elicit maturation of desired TCR specificities. To test this "thymic vaccination" concept, we designed APL of the viral CTL epitopes gp33-41 and vesicular stomatitis virus nucleoprotein octapeptide N52-59 relevant for the lymphocytic choriomeningitis virus-specific P14- and vesicular stomatitis virus-specific N15-TCRs, respectively, and examined their effects on thymocytes in vivo using irradiation chimeras. Injection of APL into irradiated congenic (Ly-5.1) mice, reconstituted with T cell progenitors from the bone marrow of P14 RAG2(-/-) (Ly-5.2) or N15 RAG2(-/-) (Ly-5.2) transgenic mice, resulted in positive selection of T cells expressing the relevant specificity. Moreover, the variants led to export of virus-specific T cells to lymph nodes, but without inducing T cell proliferation. These findings show that the mature T cell repertoire can be altered by in vivo peptide administration through manipulation of thymic selection.

Animals↗

PubMed2004

Biochemical and functional analysis of smallpox growth factor (SPGF) and anti-SPGF monoclonal antibodies.

Variola, the causative agent of smallpox, is a highly infectious double-stranded DNA virus of the orthopox genus that replicates within the cytoplasm of infected cells. For unknown reasons prominent skin manifestations, including "pox," mark the course of this systemic human disease. Here we characterized smallpox growth factor (SPGF), a protein containing an epidermal growth factor (EGF)-like domain that is conserved among orthopox viral genomes, and investigated its possible mechanistic link. We show that after recombinant expression, refolding, and purification, the EGF domain of SPGF binds exclusively to the broadly expressed cellular receptor, erb-B1 (EGF receptor), with subnanomolar affinity, stimulating the growth of primary human keratinocytes and fibroblasts. High affinity monoclonal antibodies specific for SPGF reveal in vivo immunoprotection in a murine vaccinia pneumonia model by a mechanism distinct from viral neutralization. These findings suggest that blockade of pathogenic factor actions, in general, may be advantageous to the infected host.

Amino Acid Sequence↗

PubMed2004

Phage-displayed libraries of peptide/major histocompatibility complexes.

Characterizing peptide epitopes targeted by major histocompatibility complex (MHC)-restricted T cells of unknown specificity would have broad implications. In this article we introduce and validate an original phage-displayed library of noncovalent complexes of peptide and MHC (P/MHC). We show that soluble MHC molecules associate with peptides presented by a phage, thereby resulting in the formation of multivalent P/MHC phages. Complex formation is stabilized by the interaction of the soluble partner (MHC) with two components, peptide and beta2-microglobulin, both of which are covalently linked to the phage. As proof of concept, we have used this strategy to express peptide libraries in the context of H-2K(b). Using monoclonal antibody 25D (specific for ovalbumin/H-2K(b)) as a template to screen the library, we were able to select a variant epitope functionally and structurally related to the wild-type peptide. Interaction studies between monoclonal antibody 25D and cells suggest that the variant peptide has been selected on the basis of a decreased dissociation rate between the peptide/H-2K(b) complex and its ligand. A weak agonist of the N15 TCR (vesicular stomatitis virus/H-2K(b)-specific) was also isolated from another P/MHC library. This strategy opens up new perspectives for antigen discovery and the manipulation of T cell responses.

Amino Acid Sequence↗

PubMed2004

A chimeric protein of simian immunodeficiency virus envelope glycoprotein gp140 and Escherichia coli aspartate transcarbamoylase.

The envelope glycoproteins of the human immunodeficiency virus and the related simian immunodeficiency virus (SIV) mediate viral entry into host cells by fusing viral and target cell membranes. We have reported expression, purification, and characterization of gp140 (also called gp160e), the soluble, trimeric ectodomain of the SIV envelope glycoprotein, gp160 (B. Chen et al., J. Biol. Chem. 275:34946-34953, 2000). We have now expressed and purified chimeric proteins of SIV gp140 and its variants with the catalytic subunit (C) of Escherichia coli aspartate transcarbamoylase (ATCase). The fusion proteins (SIV gp140-ATC) bind viral receptor CD4 and a number of monoclonal antibodies specific for SIV gp140. The chimeric molecule also has ATCase activity, which requires trimerization of the ATCase C chains. Thus, the fusion protein is trimeric. When ATCase regulatory subunit dimers (R(2)) are added, the fusion protein assembles into dimers of trimers as expected from the structure of C(6)R(6) ATCase. Negative-stain electron microscopy reveals spikey features of both SIV gp140 and SIV gp140-ATC. The production of the fusion proteins may enhance the possibilities for structure determination of the envelope glycoprotein either by electron cryomicroscopy or X-ray crystallography.

Amino Acid Sequence↗

PubMed2003

Genome-wide characterization of a viral cytotoxic T lymphocyte epitope repertoire.

A genome-wide search using major histocompatibility complex (MHC) class I binding and proteosome cleavage site algorithms identified 101 influenza A PR8 virus-derived peptides as potential epitopes for CD8+ T cell recognition in the H-2b mouse. Cytokine-based flow cytometry, ELISPOT, and cytotoxic T lymphocyte assays reveal that 16 are recognized by CD8+ T cells recovered directly ex vivo from infected animals, accounting for greater than 70% of CD8+ T cells recruited to lung after primary infection. Only six of the 22 highest affinity MHC class I binding peptides comprise cytotoxic T lymphocyte epitopes. The remaining non-immunogenic peptides have equivalent MHC affinity and MHC-peptide complex half-lives, eliciting T cell responses when given in adjuvant and with T cell receptor-ligand avidity comparable with their immunogenic counterparts. As revealed by a novel high sensitivity nanospray tandem mass spectrometry methodology, failure to process those predicted epitopes may contribute significantly to the absent response. These results have important implications for rationale design of CD8+ T cell vaccines.

Algorithms↗

PubMed2003

Sequence variability analysis of human class I and class II MHC molecules: functional and structural correlates of amino acid polymorphisms.

Major histocompatibility complex class I (MHCI) and class II (MHCII) molecules display peptides on antigen-presenting cell surfaces for subsequent T-cell recognition. Within the human population, allelic variation among the classical MHCI and II gene products is the basis for differential peptide binding, thymic repertoire bias and allograft rejection. While available 3D structural analysis suggests that polymorphisms are found primarily within the peptide-binding site, a broader informatic approach pinpointing functional polymorphisms relevant for immune recognition is currently lacking. To this end, we have now analyzed known human class I (774) and class II (485) alleles at each amino acid position using a variability metric (V). Polymorphisms (V>1) have been identified in residues that contact the peptide and/or T-cell receptor (TCR). Using sequence logos to investigate TCR contact sites on HLA molecules, we have identified conserved MHCI residues distinct from those of conserved MHCII residues. In addition, specific class II (HLA-DP, -DQ, -DR) and class I (HLA-A, -B, -C) contacts for TCR binding are revealed. We discuss these findings in the context of TCR restriction and alloreactivity.

Alleles↗

PubMed2003

Disparate peptide-dependent thymic selection outcomes in beta2M-deficient mice versus TAP-1-deficient mice: implications for repertoire formation.

Fetal thymic organ cultures of N15-transgenic RAG-2-/- H-2b mice on normal, beta-2 microglobulin (beta2M)-/- or transporter associated with antigen processing (rAP-1)-/- MHCl-deficient backgrounds were used to examine differentiation of thymocytes bearing a TCR specific for a viral peptide bound to H-2Kb. Strong agonists mediate negative selection in all mice whereas weak agonists are positively selecting in beta2MW-/- mice but negatively selecting on TAP-1-/- or normal backgrounds. Very weak agonists and very weak antagonists are generally without effect in beta2M-/- mice yet foster differentiation in TAP-1-/- animals. The 20-40-fold reduction in beta2M4-/- thymic H-2Kb surface expression suggests that the avidity of the TCR for peptide-MHCI accounts for these differences, consistent with effects of TCR density and individual thymic-peptide abundance in peptide-MHC complexes. TCR-self-MHC interaction dominates Kb-based selection, subtly modulated by peptides as revealed by X-ray crystallography.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2003

The crystal structure of a TL/CD8alphaalpha complex at 2.1 A resolution: implications for modulation of T cell activation and memory.

TL is a nonclassical MHC class I molecule that modulates T cell activation through relatively high-affinity interaction with CD8alphaalpha. To investigate how the TL/CD8alphaalpha interaction influences TCR signaling, we characterized the structure of the TL/CD8alphaalpha complex using X-ray crystallography. Unlike antigen-presenting molecules, the TL antigen-binding groove is occluded by specific conformational changes. This feature eliminates antigen presentation, severely hampers direct TCR recognition, and prevents TL from participating in the TCR activation complex. At the same time, the TL/CD8alphaalpha interaction is strengthened through subtle structure changes in the TL alpha3 domain. Thus, TL functions to sequester and redirect CD8alphaalpha away from the TCR, modifying lck-dependent signaling.

Amino Acid Sequence↗

PubMed2003

Structural investigations of a GYF domain covalently linked to a proline-rich peptide.

Protein structure determination of low affinity complexes of interacting macromolecules is often hampered by a lack of observable NOEs between the binding partners. Covalent linkage offers a way to shift the equilibrium of the interaction partners to the bound state. Here we show that a single-chain protein containing the GYF domain of CD2BP2 and the target peptide SHRPPPPGHRV from CD2 allows for the intramolecular association of the binding partners. We obtained NOEs between the GYF domain and the peptide that could define the principal orientation of the peptide in the complex. In conjunction with general recognition rules for proline-rich sequence recognition these NOEs allowed the accurate modeling of the protein-peptide complex.

Magnetic Resonance Spectroscopy↗

PubMed2003

CD2BP3, CIN85 and the structurally related adaptor protein CMS bind to the same CD2 cytoplasmic segment, but elicit divergent functional activities.

Interaction trap cloning was used to identify a CD2 cytoplasmic tail-binding protein termed CD2BP3. CD2BP3 is the major RNA splice variant of the CIN85 locus in human T lymphocytes, lacking SH3A, the first of three SH3 domains found in CIN85, but retaining SH3B, SH3C, a proline-rich domain and C-terminal coiled coil. CD2BP3 has 35% amino acid identity to CMS, a structurally related protein binding to the same highly conserved segment of the CD2 tail and known to be involved in T cell polarization/cytoskeletal interactions. Unlike CMS, however, CD2BP3 does not co-localize with F-actin and binds p130(Cas) weakly, if at all. Moreover, CIN85/CD2BP3 proteins are readily degraded by TCR cross-linking, consistent with the presence of a PEST sequence C-terminal to SH3C. CIN85 SH3A and CIN85/CD2BP3 SH3B bind to proline-rich segments within CIN85/CD2BP3 themselves as evidenced by mAb accessibility analysis and protein interaction studies including c-Cbl binding. This form of intramolecular regulation is not manifest by CMS. CMS and CIN85 activities are antagonistic, while the functions of CIN85 and CD2BP3 are also distinct. Thus, CD2-mediated adhesion, signaling and cell motility are regulated in a highly complex manner.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Gene expression analysis of thymocyte selection in vivo.

Self versus non-self discrimination is a key feature of immunorecognition. Through TCR-activated apoptotic mechanisms, autoreactive thymocytes are purged at the CD4(+)CD8(+) double-positive (DP) precursor stage prior to maturation to CD4(+) or CD8(+) single-positive (SP) thymocytes. To investigate this selection process in vivo, gene expression analysis by oligonucleotide array was performed in TCR transgenic mice. In total, 244 differentially expressed DP thymocyte genes induced or repressed by TCR triggering in vivo were identified. Genes involved in the biological processes of apoptosis, DNA recombination, antigen processing and adhesion are coordinately engaged. Moreover, analysis of gene expression in thymocyte subsets revealed that TCR ligand-induced expression profiles vary according to their developmental stage, with 48 genes showing DP preference and nine showing SP thymocyte preference. Finally, our data suggest that both the extrinsic and the intrinsic apoptosis pathways are operating in thymic selection.

Animals↗

PubMed2002

Sialic acid capping of CD8beta core 1-O-glycans controls thymocyte-major histocompatibility complex class I interaction.

Bidentate interaction of a T-cell receptor and CD8alphabeta heterodimer with a peptide-MHCI complex is required for the generation of cytotoxic T-lymphocytes. During thymic development, the modification of CD8beta glycans influences major histocompatibility complex class I binding to T-cell precursors called thymocytes. ES mass spectrometry (MS) and tandem MS/MS analysis were used to identify the changes occurring in the CD8beta-glycopeptides during T-cell development. Several threonine residues proximal to the CD8beta Ig headpiece are glycosylated with core-type 1 O-glycans. Non-sialylated glycoforms are present in immature thymocytes but are virtually absent in mature thymocytes. These results suggest how sialylation in a discrete segment of the CD8beta stalk by ST3Gal-1 sialyltransferase creates a molecular developmental switch that affects ligand binding.

Amino Acid Sequence↗

PubMed2002

Dynamic interaction of CD2 with the GYF and the SH3 domain of compartmentalized effector molecules.

Intracellular protein interaction domains are essential for eukaryotic signaling. In T cells, the CD2BP2 adaptor binds two membrane-proximal proline-rich motifs in the CD2 cytoplasmic tail via its GYF domain, thereby regulating interleukin-2 production. Here we present the structure of the GYF domain in complex with a CD2 tail peptide. Unlike SH3 domains, which use two surface pockets to accommodate proline residues of ligands, the GYF domain employs phylogenetically conserved hydrophobic residues to create a single interaction surface. NMR analysis shows that the Fyn but not the Lck tyrosine kinase SH3 domain competes with CD2BP2 GYF-domain binding to the same CD2 proline-rich sequence in vitro. To test the in vivo significance of this competition, we used co-immunoprecipitation experiments and found that CD2BP2 is the ligand of the membrane-proximal proline-rich tandem repeat of CD2 in detergent-soluble membrane compartments, but is replaced by Fyn SH3 after CD2 is translocated into lipid rafts upon CD2 ectodomain clustering. This unveils the mechanism of a switch of CD2 function due to an extracellular mitogenic signal.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Peptide-independent folding and CD8 alpha alpha binding by the nonclassical class I molecule, thymic leukemia antigen.

The nonclassical class I molecule, thymic leukemia (TL), has been shown to be expressed on intestinal epithelial cells and to interact with CD8(+) intraepithelial T lymphocytes. We generated recombinant soluble TL (T18(d)) H chains in bacteria as inclusion bodies and refolded them with beta(2)-microglobulin in the presence or absence of a random peptide library. Using a mAb, HD168, that recognizes a conformational epitope on native TL molecules, we observed that protein folds efficiently in the absence of peptide. Circular dichroism analysis demonstrated that TL molecules have structural features similar to classical class I molecules. Moreover, thermal denaturation experiments indicated that the melting temperature for peptide-free TL is similar to values reported previously for conventional class I-peptide complexes. Our results also show that CD8alphaalpha binding is not dependent on either TL-associated peptide or TL glycosylation.

Animals↗

PubMed2002

Involvement of the TCR Cbeta FG loop in thymic selection and T cell function.

The asymmetric disposition of T cell receptor (TCR) Cbeta and Calpha ectodomains creates a cavity with a side-wall formed by the rigid Cbeta FG loop. To investigate the significance of this conserved structure, we generated loop deletion (betaDeltaFG) and betawt transgenic (tg) mice using the TCR beta subunit of the N15 CTL. N15betawt and N15betaDeltaFG H-2(b) animals have comparable numbers of thymocytes in S phase and manifest developmental progression through the CD4(-)CD8(-) double-negative (DN) compartment. N15betaDeltaFG facilitates transition from DN to CD4(+)8(+) double-positive (DP) thymocytes in recombinase activating gene (RAG)-2(-/-) mice, showing that pre-TCR function remains. N15betaDeltaFG animals possess approximately twofold more CD8(+) single-positive (SP) thymocytes and lymph node T cells, consistent with enhanced positive selection. As an altered Valpha repertoire observed in N15betaDeltaFG mice may confound the deletion's effect, we crossed N15alphabeta TCR tg RAG-2(-/-) with N15betaDeltaFG tg RAG-2(-/-) H-2(b) mice to generate N15alphabeta RAG-2(-/-) and N15alphabeta.betaDeltaFG RAG-2(-/-) littermates. N15alphabeta.betaDeltaFG RAG-2(-/-) mice show an 8-10-fold increase in DP thymocytes due to reduced negative selection, as evidenced by diminished constitutive and cognate peptide-induced apoptosis. Compared with N15alphabeta, N15alphabeta.betaDeltaFG T cells respond poorly to cognate antigens and weak agonists. Thus, the Cbeta FG loop facilitates negative selection of thymocytes and activation of T cells.

Amino Acid Sequence↗

PubMed2002

CD2 molecules redistribute to the uropod during T cell scanning: implications for cellular activation and immune surveillance.

Dynamic binding between CD2 and CD58 counter-receptors on opposing cells optimizes immune recognition through stabilization of cell-cell contact and juxtaposition of surface membranes at a distance suitable for T cell receptor-ligand interaction. Digitized time-lapse differential interference contrast and immunofluorescence microscopy on living cells now show that this binding also induces T cell polarization. Moreover, CD2 can facilitate motility of T cells along antigen-presenting cells via a movement referred to as scanning. Both activated CD4 and CD8 T cells are able to scan antigen-presenting cells surfaces in the absence of cognate antigen. Scanning is critically dependent on T cell beta-integrin function, as well as myosin light chain kinase. More importantly, surface CD2 molecules rapidly redistribute on interaction with a cellular substratum, resulting in a 100-fold greater CD2 density in the uropod versus the leading edge. In contrast, no redistribution is observed for CD11a/CD18 or CD45. Molecular compartmentalization of CD2, T cell receptor, and lipid rafts within the uropod prearranges the cellular activation machinery for subsequent immune recognition. This "presynapse" formation on primed T cells will likely facilitate the antigen-dependent recognition capability required for efficient immune surveillance.

Antigens, CD↗

PubMed2002

CD2 facilitates differentiation of CD4 Th cells without affecting Th1/Th2 polarization.

The role of CD2 in murine CD4 helper T cell differentiation and polarization was examined using TCR-Cyt-5CC7-I transgenic recombination activating gene-2-/- H-2(a) mice on CD2+/+ or CD2-/- backgrounds. In the absence of CD2, thymic development was abnormal as judged by reduction in the steady state number of total, double-positive, and CD4 single-positive (SP) thymocytes, as well as a defect in their restorative dynamics after peptide-induced negative selection in vivo. In addition, in CD2-/- animals, lymph node CD4 SP T cells manifest a 10- to 100-fold attenuated activation response to cytochrome c (CytC) agonist peptides as judged by induction of CD25 and CD69 cell surface expression or [(3)H]TdR incorporation; differences in the magnitude of responsiveness and requisite molar peptide concentrations were even greater for altered peptide ligands. Although the presence or absence of CD2 did not impact the final Th1 or Th2 polarization outcome, CD2 expression reduced the CytC peptide concentration threshold necessary to facilitate both Th1 and Th2 differentiation. In vivo administration of CytC peptide to CD2-/- animals yielded an impaired CD4 SP T cell effector/memory phenotype compared with similarly treated CD2+/+ mice. Analysis of TCR-Cyt-5CC7-I human CD2 double-transgenic mice similarly failed to reveal a preferential Th1 vs Th2 polarization. Collectively, these results indicate that CD2 is important for the efficient development of CD4 SP thymocytes and TCR-dependent activation of mature CD4 lymph node T cells, but does not direct a particular helper T cell subset polarity.

Amino Acid Sequence↗

PubMed2002

Structural basis of T cell recognition of peptides bound to MHC molecules.

Helper T lymphocytes play a critical role in immune system activation following recognition of MHC class II-bound peptide ligands (pMHCII). These CD4 T cells stimulate B cell antibody production and cytolytic T cell generation. Until recently, the structural basis of coordinate T cell receptor (TCR) and CD4 co-receptor interaction with a given pMHCII was unknown. Here we review current structural data on specific pMHCII recognition by T cells and compare TCR and co-receptor docking to pMHCI versus pMHCII ligands. The implications of these findings for thymic selection, helper versus cytolytic T cell recognition and alloreactivity are discussed.

Amino Acid Sequence↗