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S Rodda

Publications and source records attributed to S Rodda.

16 recordsLinked to original sources
PubMed2000

CRTR-1, a developmentally regulated transcriptional repressor related to the CP2 family of transcription factors.

CP2-related proteins comprise a family of DNA-binding transcription factors that are generally activators of transcription and expressed ubiquitously. We reported a differential display polymerase chain reaction fragment, Psc2, which was expressed in a regulated fashion in mouse pluripotent cells in vitro and in vivo. Here, we report further characterization of the Psc2 cDNA and function. The Psc2 cDNA contained an open reading frame homologous to CP2 family proteins. Regions implicated in DNA binding and oligomeric complex formation, but not transcription activation, were conserved. Psc2 expression in vivo during embryogenesis and in the adult mouse demonstrated tight spatial and temporal regulation, with the highest levels of expression in the epithelial lining of distal convoluted tubules in embryonic and adult kidneys. Functional analysis demonstrated that PSC2 repressed transcription 2.5-15-fold when bound to a heterologous promoter in ES, 293T, and COS-1 cells. The N-terminal 52 amino acids of PSC2 were shown to be necessary and sufficient for this activity and did not share obvious homology with reported repressor motifs. These results represent the first report of a CP2 family member that is expressed in a developmentally regulated fashion in vivo and that acts as a direct repressor of transcription. Accordingly, the protein has been named CP2-Related Transcriptional Repressor-1 (CRTR-1).

Amino Acid Sequence↗
PubMed1997

Determinants of T cell reactivity to the Mycobacterium leprae GroES homologue.

The 10-kDa protein Ag of Mycobacterium leprae, a human GroES hsp10 cognate, is a major T cell Ag in human leprosy infection. We investigated the mechanism for T cell responsiveness to this Ag according to the trimolecular interaction between T cell, peptide, and Ag-presenting element. This research was accomplished by mapping T cell epitopes in leprosy patients and correlating these responses with peptide-MHC binding affinities. We found that the majority of tuberculoid leprosy patients responded to peptides corresponding to residues 25-39 and 28-42. Truncation analysis of these peptides mapped the exact epitope to be within the overlapping region comprising residues 28-39. Responsiveness was correlated with the HLA-DRB5*0101 allele, which bound the peptides with moderate affinity. This allele is linked to HLA-DR2, which is associated with the resistant form of leprosy. Therefore, T cell responsiveness in tuberculoid leprosy may be mediated by the ability of HLA-DRB5*0101 to bind and present peptides of the immunodominant 10-kDa Ag.

Alleles↗
PubMed1997

Human T-cell clones to the 70-kilodalton heat shock protein of Mycobacterium leprae define mycobacterium-specific epitopes rather than shared epitopes.

The mycobacterial 70-kDa heat shock protein (Hsp70) is a dominant antigen during the human T-cell response to mycobacterial infection despite the conserved sequence with the human homolog. To determine whether this response is pathogen specific, CD4+ T-cell clones were isolated from Mycobacterium leprae Hsp70-reactive individuals. The cytokine profile of the clones was mixed, with all of the clones releasing interferon gamma and half releasing interleukin-4 on stimulation, while six demonstrated cytolytic activity. Five clones reacted with the N-terminal half of the molecule, and the epitopes identified were mycobacterium specific. Residues 241 to 260 were identified by three clones, one of which was restricted by HLA-DR7 (DR7), while a DR1-restricted clone identified residues 71 to 90 and residues 261 to 280 were recognized in the context of DR3. The remaining five T-cell clones reacted with the C-terminal half of the molecule, and the precise position of these epitopes was mapped with 12-mer peptides overlapping by 11 residues. Two of these clones identified overlapping epitopes from residues 411 to 425 and 412 to 428, the latter restricted by DR3. Further epitopes were mapped to residues 298 to 313 restricted by DRw53, residues 388 to 406 restricted by DRw52 or DQ2, and residues 471 to 486 restricted by DR1. The sequences of three epitopes, residues 411 to 425, 412 to 428, and 471 to 486, showed significant identity with the equivalent regions of the prototype human Hsp70. However, when amino acid substitutions that made the sequence more like the human sequence were introduced, the changes were tolerated poorly as measured by proliferation, cytokine production, and cytotoxic potential. Therefore, T-cell recognition of the M. leprae Hsp70 antigen occurs in the context of multiple HLA-DR phenotypes and is exquisitely species specific.

Amino Acid Sequence↗
PubMed1994

Immunodominant epitopes of glutamic acid decarboxylase 65 and 67 in insulin-dependent diabetes mellitus.

To find the dominant epitopes of a major autoantigen in insulin-dependent diabetes mellitus (IDDM), glutamic acid decarboxylase (GAD), we studied the reactivity of peripheral blood T lymphocytes with peptides covering both major isoforms. A significant response to GAD 65 or GAD 67 peptides was detected in 13 of 15 IDDM patients and in 9 of 10 normal controls. Controls most frequently recognised the central region of GAD 65 (residues 161-243). IDDM patients preferentially recognised residues 473-555 (p < 0.03). T-cell responses to GAD 67 peptides were similar in IDDM patients and controls. T lymphocytes from IDDM patients recognise a distinct dominant epitope of GAD, which may be an important target for the disease process.

Adolescent↗
PubMed1994

Mapping of T cell epitopes of the major fraction of rye grass using peripheral blood mononuclear cells from atopics and non-atopics. II. Isoallergen clone 5A of Lolium perenne group I (Lol p I).

Rye grass is the major cause of hay fever which currently affects 20% of the population. Lolium perenne group I (Lol p I) is a glycoprotein of 240 amino acid residues, representing the main allergen of rye grass. We have used peripheral blood mononuclear cells (PBMC) from controls and subjects allergic to rye grass and cultured them with L. perenne extract (LPE) and Lol p I and measured lymphocyte activation using thymidine incorporation. Patients were further studied against the 115 overlapping peptides of the iso-allergen clone 5A of Lol p I to see whether the 4 amino acid residue differences between clone 1A and clone 5A affect the T cell epitope and thus, lymphocyte activation. There are 24 peptide differences between isoallergen clone 1A and clone 5A occurring in pools 4, 13, 16 and 19 each one of which could be an immunodominant epitope. The PBMC from all allergic patients studied showed a strong proliferative response to LPE and Lol p I. Five immunogenic peptide pools, pool 6, 15, 16, 17 and 19 of the isoallergen clone 5A were also identified. Most of these pools are in the C-terminal region of Lol p I. Out of 20 pools tested in vitro 1 pool (pool-17) induced PBMC proliferation in five out of six patients who were not restricted to an HLA class II DR gene product. However, three out of the six subjects responded to various other peptide pools in addition to the immunodominant pool. In spite of the amino acid differences between the two clones, pool 17 still remains the immunodominant T cell epitope. Control subjects showed only weak responses to LPE and no detectable response to either Lol p I or peptide pools. From within the most active pool we have defined two peptides of the isoallergen clone 5A (identical in sequence with clone 1A) which stimulate lymphocytes from rye grass-sensitive patients in vitro. Previous studies with the two continuous sequences (193WGAVWRIDTPDK204 and 195AVWRIDTPDKLT206) tested in vivo by intradermal skin testing have shown typical delayed-type hypersensitivity reactions after 24-48 h in one patient. Comparison of amino acid sequences of Lol p I, Lol p II and Lol p III proteins revealed a significant level of structural similarity among them. Interestingly, 50% of the residues of the second peptide sequence are also present in Lol p II and Lol p III.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

Peptide antagonists that promote positive selection are inefficient at T cell activation and thymocyte deletion.

We set out to determine whether thymocytes from T cell receptor (TCR) transgenic animals specific for a class I-restricted determinant from ovalbumin (OVA) showed the same fine specificity for antigen-driven deletion in single-cell suspension culture as required for mature T cell activation. The transgenic TCR is specific for the Kb-restricted peptide OVA257-264 (SIINFEKL) which is known to have four TCR contact residues at position 1, 4, 6, and 7 from the crystal structure of this fragment in complex with Kb. OVA257-264 analogs systematically substituted at each of these positions were assayed for their ability to promote immature double-positive thymocyte deletion or mature T cell activation of a cytotoxic T lymphocyte line derived from this transgenic mouse. In the absence of additional antigen-presenting cells, single-cell thymocyte suspensions showed that the specificity for double-positive thymocyte deletion and mature T cell activation was virtually identical, demonstrating a limited cross-reactivity with a number of variants having conservative substitutions at these exposed residues. These peptides were considerably more efficient at both thymic deletion and mature T cell activation than a number of non-conservative substitution analogs known to act as antagonists of OVA257-264 and capable of selecting transgenic T cells in thymic organ culture. Therefore, both peripheral T cell activation and thymic deletion have an overall similar pattern of peptide specificity which differs from that required for positive selection. This suggests that a subset of major histocompatibility complex-presented peptides could promote positive selection without causing either thymic deletion or peripheral activation of those selected T cells.

Amino Acid Sequence↗
PubMed1994

Comprehensive T-cell epitope mapping of HIV-1 env antigens reveals many areas recognized by HIV-1-seropositive and by low-risk HIV-1-seronegative individuals.

Peripheral blood mononuclear cells from 12 asymptomatic human immunodeficiency virus (HIV)-1-seropositive and nine HIV-1-seronegative donors were screened for proliferative T-lymphocyte responses to peptides derived from a consensus sequence of the HIV-1 env gene products from 25 HIV-1 isolates. Two hundred seventy-eight overlapping 17mer peptides, incremented by three residues each, were pooled into groups, each containing eight sequential peptides, for use in proliferation tests. Thirty-eight additional peptides containing variant amino acid residues also were tested. Proliferation data were analyzed using an algorithm that reduced subjective bias and estimated the responding cell frequencies. Peripheral blood mononuclear cells from a majority of donors, regardless of HIV-1 status, recognized peptides within two pools derived from the gp120 sequence and peptides from one pool in gp41. Pool 25 peptides from gp41 (centered around residue 600 of the gp160 consensus sequence) were recognized most frequently. The observed inability to differentiate between responses of HIV-1-seropositive and HIV-1-seronegative individuals implies either a lack of HIV-1 disease-related immunodominant env epitopes or functional abrogation of HIV-1 env-specific T-helper lymphocyte responses soon after infection. The observed proliferation of T lymphocytes from noninfected, low-risk individuals questions the origin of the responses to HIV-1 env-derived peptides and suggest that preexisting, cross-reactive immunity could influence responses to HIV-1.

Adult↗
PubMed1993

Changes at peptide residues buried in the major histocompatibility complex (MHC) class I binding cleft influence T cell recognition: a possible role for indirect conformational alterations in the MHC class I or bound peptide in determining T cell recognition.

Recent crystallographic studies on two peptide complexes with the mouse Kb molecule have shown that peptide binding appears to alter the conformation of the class I alpha-helical regions that flank the antigen binding cleft. Given that this study also showed that much of the foreign peptide is buried within the class I binding cleft with only a small portion accessible for direct interaction with the components of the T cell receptor, this finding suggests that at least some component of T cell specificity may arise as a consequence of peptide-induced conformational changes in the class I structure. To assess this possibility, we have made systematic substitutions at residues within the Kb-restricted determinant from ovalbumin (OVA257-264) that are thought to be buried on binding to the class I molecule. We have found that changes in this determinant at the completely buried second residue (P2) can influence T cell recognition without affecting binding to Kb, suggesting that the substitutions may indirectly determine T cell recognition by altering the conformation of the class I molecule or the bound peptide.

Amino Acids↗
PubMed1993

Identification of conserved T cell receptor CDR3 residues contacting known exposed peptide side chains from a major histocompatibility complex class I-bound determinant.

We have analyzed the T cell receptor (TCR) repertoire found in the major histocompatibility complex class I-restricted cytotoxic T lymphocyte (CTL) response to the protein ovalbumin (OVA). Despite skewing towards the expression of V beta 5.2+TCR by OVA-specific CTL from C57BL/6 mice, we found a relatively high degree of diversity in V(D)J usage in both TCR alpha- and beta-chains. Closer examination showed that the majority of these sequences encoded negatively and positively charged residues at their respective TCR alpha- and beta-chain VJ or VDJ junctions. These junctions form the third complementarity-determining regions (CDR3) of the TCR polypeptides involved in the direct interaction with the class I-bound peptide. Crystallographic analyses of Kb-peptide complexes predict that the major determinant from OVA, peptide OVA257-264 (SIINFEKL), contains two exposed charged side chains which can contact the TCR. These are the negatively charged glutamic acid at determinant position 6 (P6) and the positively charged lysine at P7. To examine whether the TCR alpha-chain makes contact with P7 lysine, we established a single chain TCR transgenic C57BL/6 mouse line where all T cells express a TCR beta-chain derived from the V beta 5.2+ clone B3. OVA-specific T cells derived from in vivo primed transgenic mice preferentially expressed TCR alpha-chains that also contained negatively charged junctional residues despite some further variation in V alpha and J alpha sequences. Stimulation of naive TCR beta-chain transgenic T cells with a P7 substitution peptide analogue induced a T cell response that was no longer cross-reactive with the wild-type OVA257-264 determinant, suggesting that the TCR alpha-chain from the T cell clone B3 can determine the specificity for this residue. Consequently, these results reveal the existence of conserved residues in the CDR3 of TCR alpha- and beta-chains specific for OVA257-264 and identify their possible orientation over the peptide-class I complex.

Amino Acid Sequence↗
PubMed1993

T cell epitopes of the major fraction of rye grass Lolium perenne (Lol p I) defined using overlapping peptides in vitro and in vivo. I. Isoallergen clone1A.

One hundred and fifteen overlapping synthetic peptides spanning the entire sequence of the iso-allergen clone1A of Lol p I from rye grass Lolium perenne were synthesized by the multi-pin technique. The peptides were overlapping 12mers, offset by two residues and overlapping by 10 residues. Sets of six adjacent overlapping peptides (except pool-1, 15, 20) were pooled and were used in vitro and in vivo to map the T cell epitopes on Lol p I. Six atopics who were skin test and RAST positive to rye grass showed T cell responses to L. perenne extract (LPE) and its major fraction (Lol p I). Five out of six showed T cell responses in vitro to peptide pool-17, while five non-atopics did not respond to any of the peptide pools. By testing the individual peptides of pool-17, we have located the T cell epitope on Lol p I. Interestingly, when we tested pool-17 and its single peptides in vivo by intradermal skin testing we found in one patient a typical DTH after 24-48 h to pool-17 and its peptides (peptides 3 and 4) which exactly matched the in vitro responses. By defining the T cell epitopes in this way a greater understanding of the allergic response to pollen will be obtained, and a more effective and less dangerous vaccine may be possible for treating patients with hay fever.

Adult↗
PubMed1992

T cell receptor alpha-chain pairing determines the specificity of residue 262 within the Kb-restricted, ovalbumin257-264 determinant.

Ovalbumin-specific, Kb-restricted T cells recognize the minimal fully active synthetic peptide ovalbumin (OVA)257-264. This sequence coincides with the eight residue, allele-specific peptide binding motif previously predicted from direct sequencing of naturally occurring Kb-associated peptides (Falk, K., Rotzscke, O., Stevanovic, S., Jung, G., and Rammensee, H.-G., Nature 351:290, 1990). T cell recognition of a panel of analogs with single residue substitutions between the two putative Kb anchor residues at OVA261 and OVA264 suggested that at least one residue, Glu at position 262, is involved in TCR interaction. OVA-specific cytotoxic T lymphocytes (CTL) derived from TCR beta-chain transgenic mice, where the beta-chain originates from an OVA-specific, Kb-restricted CTL B3, showed that differences in TCR alpha-chain pairing determined the specificity for OVA residue 262. These data support the notion that residue 262 of the OVA T cell determinant, corresponding to position 6 within the Kb-binding motif, represents a contact site for TCR. This residue interacts directly with the TCR alpha-chain or with a site on the TCR beta-chain whose conformation is affected by TCR alpha-chain pairing.

Amino Acid Sequence↗
PubMedDate not supplied

Pin peptide synthesis.

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Indicators and Reagents↗
PubMedDate not supplied

Modification of the carboxyl terminal group affects replacement set analysis of a cytotoxic T cell epitope.

An Epstein-Barr virus-specific cytotoxic T cell (CTL) clone was previously shown to recognize the epitope FLRGRAYGL. The ability of substituted peptides to sensitize target cells for lysis by this clone was investigated using two peptide replacement sets, one synthesized with free carboxyl termini and another made with a carboxyl terminal beta-alanine-diketopiperazine (beta A-DKP) group. Curiously, the effect of certain substitutions differed for the two peptide sets. For example, NH2-FLRGRAYGL-beta A-DKP was 15-fold more active than NH2-FLRGRAYGI-beta A-DKR, but NH2-FLRGRAY-GL-COOH had the same activity as NH2-FLRGRAYGI-COOH. Evidence presented here illustrates that the activity of beta A-DKP peptide preparations was entirely due to contaminating peptides with free-COOH termini. The amount of active-COOH contaminants within a -beta A-DKP preparation thus appeared to vary depending on the substitution, resulting in some anomalous results from replacement set analysis using -beta A-DKP peptides.

Amino Acid Sequence↗