Biomedical subjects

J T Wong

Publications and source records attributed to J T Wong.

At least 19 recordsLinked to original sources

PubMed1992

Intrahepatic cytotoxic T lymphocytes specific for hepatitis C virus in persons with chronic hepatitis.

Hepatitis C virus (HCV) is a major cause of post-transfusion and sporadic hepatitis worldwide, leading to chronic liver disease in at least 50% of infected individuals. The pathogenic mechanisms that result in chronic hepatitis are unknown. Lymphocytes are typically observed within the hepatic parenchyma, but the functional characteristics of these cells have not been defined. In this study, liver-infiltrating lymphocytes from two subjects with chronic HCV hepatitis were cloned at limiting dilution and tested for HCV-specific cytolytic activity using autologous target cells infected with vaccinia viruses expressing recombinant HCV Ag or sensitized with synthetic HCV peptides. In both subjects, HCV-specific, HLA class I-restricted CTL were identified that recognized epitopes in variable regions of either the envelope or nonstructural proteins. These results demonstrate the presence of HCV-specific CTL at the site of tissue damage in persons with chronic HCV hepatitis, and provide a means to evaluate the possible pathogenic role of these cells in HCV infection.

Amino Acid Sequence↗

PubMed1992

Mutational identification of an essential tryptophan in tryptophanyl-tRNA synthetase of Bacillus subtilis.

The strongly conserved single tryptophan residue, Trp92, in Bacillus subtilis tryptophanyl-tRNA synthetase has been mutagenized via site direction singly into Gln, Ala, and Phe. All three mutant enzymes were inactive toward the catalysis of tRNA tryptophanylation. The Trp92----Phe mutant has been subcloned into the high expression plasmid pKK223-3 to yield the recombinant plasmid pKSW-F92. Growth of bacteria carrying the latter plasmid made possible the purification of the mutant TrpRS-F92 enzyme to homogeneity. This mutant enzyme was deficient in ultraviolet absorbance and fluorescence relative to the wild type enzyme and inactive in the partial reaction of Trp-activation as well as the overall reaction of tRNA tryptophanylation. Furthermore, unlike the wild type B. subtilis trpS gene, the mutant trpS-F92 gene upon transformation into Escherichia coli trpS 10343 failed to complement the temperature sensitive trpS mutation of the host cells. Trp92 therefore represents an essential residue both in vitro and in vivo for the function of the tryptophanyl-tRNA synthetase.

Amino Acid Sequence↗

PubMed1992

Comparative studies of isolated CD3: CD8, CD3: CD3, and monovalent CD3 binding on CD8+ T-cell activation: model of progressive T-cell receptor aggregation synergism.

The TCR and CD8 complexes of CD8+ T cells bind to different regions of MHC class I molecules and both play important roles in the response of the CD8+ T cells to Ag/MHC on APCs. In this report, we mimicked common MHC binding with an anti-CD3:anti-CD8 (CD3,8) BSMAB to isolate the effect of CD3: CD8 pairing, compared this with the effect of CD3: CD3 pairing by the parental bivalent anti-CD3 MAB, and with monovalent anti-CD3 binding by an anti-CD3: anti-CD4 (CD3,4) BSMAB. CD3: CD8 pairing induced an increase in cytosolic free [Ca2+] 1.5 to 3.0-fold greater than the increase induced by CD3: CD3 pairing whereas monovalent CD3 binding induced only 20%-30% of the increase. Postbinding receptor migration studies suggested that microaggregation increased from monovalent CD3 binding to CD3: CD3 pairing to CD3: CD8 pairing. Further studies revealed that progressively higher concentrations of antibodies were needed from CD3,8 to CD3,3 to CD3,4 to initiate the same degree of DNA synthesis. These results demonstrated that Ti/CD3 and CD8 can indeed be bridged by a single molecule. A model of direct CD8: CD3 synergism was raised as a possible explanation for the enhanced activation induced by CD3: CD8 pairing. The observed parallel between all three parameters and the number of TCRs that can be directly linked by the Abs raised a nonmutually exclusive model whereby CD3 binding induces activated TCR intermediaries (aTCRi) that progressively synergize with other adjacent aTCRis. In this model, this dominant inter-aTCRi synergism may be enhanced by the di- and multimeric CD8 alpha chains serving as aTCRi-aggregation foci.

Antigen-Antibody Reactions↗

PubMed1992

T cell heterogeneity in patients with common variable immunodeficiency as assessed by abnormalities of T cell subpopulations and T cell receptor gene analysis.

T lymphocyte regulation of immunoglobulin production may be abnormal in some patients with common variable immunodeficiency (CVI). Phenotypic analysis of peripheral blood T lymphocytes from nine patients with CVI was conducted to examine whether an abnormal distribution could be detected in a functionally distinct T lymphocyte subpopulation. The percentage of CD8+ lymphocytes proved to be increased in some patients and decreased in others. In comparison with normal controls, many patients with CVI had reduced percentages of lymphocytes expressing both CD4 and CD45RA, a phenotype associate with naive CD4+ cells. There was no significant difference in CD4+ populations bearing CD29 or leucocyte adhesion molecule-1 (LAM-1) antigens. The pattern of gene rearrangement of the T cell antigen receptor (TCR) was studied using peripheral blood lymphocytes from these patients with CVI. Genomic DNA from freshly isolated lymphocytes as well as from selectively propagated CD4+ or CD8+ populations were examined using Southern blot analysis and a probe for the beta chain of the TCR. A polyclonal pattern of TCR gene rearrangement, without the appearance of dominant non-germline bands, was demonstrated in all patient samples. These data suggest that the T lymphocytes in patients with CVI have a polyclonal pattern of TCR rearrangement despite an abnormal distribution of T cell subpopulations in some patients.

Adult↗

PubMed1991

Origin of genetically encoded protein synthesis: a model based on selection for RNA peptidation.

The difficulty in explaining the origin of genetic coding centres on the need to identify selective advantages that could account for the synthesis of peptidyl-tRNA, the essential intermediate in genetically programmed translation. It is resolved by a recognition of the functional advantages derivable from the post-transcriptional addition of peptide cofactors to RNA apo-catalysts. This enables the formulation of a theory for the origin of the genetic encoding of protein synthesis by RNA.

Amino Acid Sequence↗

PubMed1991

Selective reduction and proliferation of the CD4+ and CD8+ T cell subsets with bispecific monoclonal antibodies: evidence for inter-T cell-mediated cytolysis.

CD3,4 (anti-CD3:anti-CD4) bispecific monoclonal antibodies (BSMAB) cause a profound decrease in CD4+ T cells and a marked proliferation of CD8+ T cells in peripheral blood mononuclear cells in vitro. CD3,8 (anti-CD3:anti-CD8) BSMAB causes a reciprocal decrease in CD8+ T cells and a proliferation of CD4+ T cells. The major effector of CD4+ T cell cytolysis in the presence of CD3,4 resides in the CD8+ T cell population. In contrast, both the CD4+ and CD8+ T cells are effective mediators of cytolysis of the CD8+ T cells in the presence of the CD3,8. The likely underlying mechanism in each case is bridging of the CD4 and CD8 of the target cells to the CD3 complexes of the effector cells by antibodies, mimicking the natural encounter between a cytolytic T cell and its target. Proliferation studies indicated that CD3,4 and CD3,8 each can induce proliferation of both CD4+ and CD8+ T cells in the presence of accessory cells. These results suggest that the major selection of the BSMABs occurs via selective destruction of one T cell subset with concurrent stimulation of the remaining CD3+ population. Potential applications of the selective destruction and proliferation include study and manipulation of the T cell subsets in HIV infections, tumor infiltrating lymphocytes, autoimmune diseases, and graft rejection.

Antibodies, Monoclonal↗

PubMed1991

Effects of the antidepressant phenelzine on brain levels of gamma-aminobutyric acid (GABA).

Time- and dose-response studies were carried out on the effects of the monoamine oxidase-inhibiting antidepressant and antipanic drug phenelzine on GABA levels in rat whole brain. At a dose of 15 mg/kg i.p., phenelzine significantly elevated GABA levels at all time intervals studied (1, 2, 4, 8, 16, and 24 h). A further investigation indicated that this was a dose-dependent effect. The possible importance of GABA in the etiology and pharmacotherapy of depression and panic disorder is discussed.

Animals↗

PubMed1991

An HLA-C-restricted CD8+ cytotoxic T-lymphocyte clone recognizes a highly conserved epitope on human immunodeficiency virus type 1 gag.

A unique epitope on the gag protein of human immunodeficiency virus type 1 (HIV-1), located at amino acid 145 to 150, has been mapped by using a CD8+ cytotoxic T-lymphocyte (CTL) clone. This epitope is highly conserved among 18 HIV-1 strains. The HIV-1 gag-specific human leukocyte antigen (HLA) class I-restricted CD8+ CTL clone was generated from fresh peripheral blood mononuclear cells of an HIV-seropositive donor by stimulation with gamma-irradiated allogeneic peripheral blood mononuclear cells in the presence of an anti-CD3 monoclonal antibody and recombinant interleukin-2. This gag-specific CTL clone killed autologous target cells infected with a recombinant vaccinia virus containing the gag gene of HIV-1 and target cells pulsed with an authentic p24gag construct expressed in Escherichia coli. Fine specificity was determined by using a panel of overlapping 30-amino-acid-long synthetic peptides and subsequently using smaller peptides to precisely map the CTL domain on p24. The epitope is on a highly conserved region, and it overlaps with a major B-cell epitope of gag. This CD8+ T-cell epitope is restricted by HLA-Cw3, which has not been previously identified as a restricting element for human CTL responses.

Amino Acid Sequence↗

PubMed1991

Behavioral and neurochemical interactions between cocaine and buprenorphine: implications for the pharmacotherapy of cocaine abuse.

Intravenous self-administration studies in nonhuman primates suggest that the opioid receptor agonist-antagonist buprenorphine may be useful in the pharmacotherapy of cocaine abuse. In the present studies, behavioral and neurochemical interactions between cocaine and buprenorphine were examined using a conditioned place preference (CPP) procedure and in vivo microdialysis. Cocaine-induced CPP was linearly related to the dose administered (0-5.0 mg/kg). Buprenorphine (0-0.9 mg/kg) also elicited CPP in a dose-related manner; an inverted U-shaped function was obtained. Subthreshold doses of cocaine (1.5 mg/kg) and buprenorphine (0.01 mg/kg), themselves incapable of eliciting CPP, produced a significant CPP when given together. Moderate doses of cocaine (5.0 mg/kg) and buprenorphine (0.075 mg/kg), which were individually capable of eliciting CPP, produced a significantly larger CPP when given in combination. In the in vivo microdialysis studies, a low dose of buprenorphine (0.01 mg/kg) produced a progressive increase in extracellular dopamine in the nucleus accumbens, reaching approximately 200% of basal levels after 5 hr. Cocaine (5.0 mg/kg) rapidly increased extracellular dopamine concentrations (180% of basal values within 20 min), which returned to baseline in 2 to 3 hr. This effect of cocaine was significantly potentiated by coadministering buprenorphine (0.01 mg/kg); under this condition the peak increase in extracellular dopamine reached 260% of baseline values. These neurochemical findings are consistent with the CPP results and indicate that buprenorphine can interact with cocaine in a synergistic manner. In contrast to previous speculations, these results suggest that buprenorphine may enhance rather than attenuate the rewarding properties of cocaine.

Animals↗

PubMed1990

A rapid procedure for the analysis of phenylalanine in brain tissue utilizing electron-capture gas chromatography.

A rapid procedure has been developed for the analysis of phenylalanine in brain tissue. Perchloric acid extracts of brain tissue were made basic, and benzoyl chloride was added to derivatize the amine function. The aqueous layer was retained and made slightly acidic. To derivatize the carboxylic acid group, a solution of pentafluorobenzyl alcohol was added in the presence of the coupling agent dicyclohexylcarbodiimide and chloroform. After shaking for 15 min, the organic phase was retained and taken to dryness. The residue was taken up in toluene, washed, and an aliquot used for analysis on a gas chromatograph equipped with an automatic injector, a capillary column and an electron-capture detector. The procedure has been utilized for analysis of phenylalanine in brains of rats treated with vehicle or phenylalanine.

Animals↗

PubMed1990

Plasma amino acids in attention deficit disorder.

This study examines plasma amino acids in a group of 28 patients meeting DSM-III criteria for attention deficit disorder (ADD) and 20 control subjects. Compared with controls, the ADD subjects had significantly lower levels of phenylalanine, tyrosine, tryptophan, histidine, and isoleucine. These data suggest a general deficit in amino acid transport, absorption, or both.

Amino Acids↗

PubMed1990

Long-lasting elevation of alanine in brain produced by the antidepressant phenelzine.

Time- and dose-response studies were conducted to determine the effects of the antidepressant and antipanic drug phenelzine (a monoamine oxidase inhibitor) on whole brain levels of the aliphatic amino acid alanine. At a dose of phenelzine of 15 mg/kg IP, there was a significant increase in brain levels of alanine up to 16 hr after drug administration. Dose studies at 4 hr indicated that the alanine elevation after phenelzine was a dose-dependent effect.

Alanine↗

PubMed1990

Immunogenic epitopes of the p55 chain of the IL-2 receptor. Relationships to high-affinity IL-2 binding and modulation of the p55 chain.

Monoclonal antibodies were used to determine the relationships between epitopes on the p55 chain of the IL-2 receptor and high-affinity IL-2 binding. Five monoclonal antibodies to the human P55 chain of the IL-2 receptor were induced by immunizing mice with murine L cells that were transfected with human p55 cDNA. Since the p55 chain is the only human antigen expressed on these cells, all antihuman MABs thus generated were directed against this molecule. These antibodies were used to map epitopes on the p55 chain and determine their relationship to high-affinity IL-2 binding. Extensive flow cytometric studies with these MABs and a large panel of other anti-p55 MABs revealed three major patterns of competition. Type I MABs compete with anti-Tac extensively but not with antibodies of other groups. Type II MABs do not block anti-Tac but do block 7E11. Type III MABs do not block either type I or type II antibodies. 125I-IL2 competition studies under high-affinity conditions revealed that types I and II MABs inhibit IL-2 binding. Type III MABs can be resolved into two subgroups, one that inhibits IL-2 binding and one that does not. Together these data suggest that there are at least four distinct immunogenic epitopes on the human p55 chain, with three epitopes related to IL-2 binding. The competitive component evident by a change in Kd on the Scatchard plots suggests that all three epitopes are close to or part of the IL-2-binding site of the p55 chain. The noncompetitive component, as evidenced by the lower number of high-affinity IL-2 receptors induced by these antibodies, suggests that the same epitopes are also close to the site(s) of interaction between the p55 and p70 chains to form the high-affinity receptor. These studies indicated that the IL-2-binding site and site of interaction between the p55 and p70 chains are close together or identical. Modulation studies revealed that one type II antibody (7E11) modulates the p55 chain in the absence of IL2 and the p70 chain, thus revealing that modulation of the p55 chain can occur by an active process, and not merely passively comodulate by the p70 chain upon IL-2 binding. Modulation of the p55 chain alone has no proliferative effect on IL-2-responsive T lymphoblasts. Potentially this antibody-dependent modulation may be used to deliver toxin to activated lymphocytes.

Antibodies, Monoclonal↗

PubMed1990

The mechanism of anti-CD3 monoclonal antibodies. Mediation of cytolysis by inter-T cell bridging.

OKT3, an anti-CD3 MAB, depletes T cells in vivo and is among the most potent inhibitors of acute allograft rejection. The mechanism of this inhibition is unknown. The present studies investigate whether anti-CD3 antibodies have the ability to crosslink CD3 on two different cells and induce TCR-dependent antibody-bridged cell-mediated cytolysis (TCR-ABCMC) between T cells. Two different anti-CD3 antibodies (OKT3 and CD3,3) and OKT3 F(ab')2 were all highly effective in inducing cytolysis of CD8+ and CD4+ T cells by CD8+ T cells, and CD8+ T cells by CD4+ T cells. Monovalent OKT3 Fab was 25-125-fold less potent than OKT3 F(ab')2. Monovalent CD3,X was totally ineffective. The necessity for intercellular bridging was evidenced by the observation that an anti-CD3:anti-CD4 (CD3,4) bispecific MAB (BSMAB) was effective in mediating lysis of CD4+ but not CD8+ T cells by CD8+ T cells. These studies indicate that neither FcR-mediated ADCC nor complement fixation is necessary for bivalent anti-CD3 MAB to lyse T cells. Inter-T cell TCR-ABCMC may be particularly effective in inflammatory tissues, such as rejecting allografts and autoimmune diseases, in which numerous cytolytic T lymphocytes are present in close association with other T cells.

Animals↗

PubMed1990

High-level expression of Bacillus subtilis tryptophanyl-tRNA synthetase in Escherichia coli.

The trpS gene encoding Bacillus subtilis tryptophanyl-tRNA synthetase (TrpRS) was prepared from the pUC8-derived pTSQ2 plasmid, mutagenized to introduce an EcoRI site immediately in front of the ATG start codon, and inserted into the pKK223-3 vector downstream to the tac promoter to yield the pKSW1 plasmid. Upon induction with isopropyl-beta-D-thiogalactopyranoside, Escherichia coli JM109[pKSW1] cells synthesized TrpRS to a level corresponding to 45% of total cell proteins. This high level of gene expression facilitates large scale preparation of TrpRS for physical studies, detection of in vivo degradation of mutant forms of TrpRS, and comparative assays of TrpRS by [3H]Trp-tRNA formation and by Trp-hydroxamate formation for the purpose of mutant characterization. Finally, since pKSW1 could complement the temperature-sensitive TrpRS mutation on E. coli trpS 10343 cells, defective mutations of the trpS gene on pKSW1 would be deductible on the basis of complementation testing.

Amino Acyl-tRNA Synthetases↗

PubMed1990

A rapid, sensitive assay for gamma-aminobutyric acid in brain using electron-capture gas chromatography.

A rapid, sensitive procedure has been developed for the assay of gamma-aminobutyric acid (GABA) in brain tissue. The method involves sequential reaction with isobutyl chloroformate and pentafluorophenol under aqueous conditions and subsequent separation and quantitation of the derivative on a gas chromatograph equipped with a capillary column and an electron-capture detector. The method produces a derivative with good stability and provides for simultaneous analysis of GABA and five other aliphaticamino acids in very small volumes of supernatant from brain homogenates.

Amino Acids↗

PubMed1989

Characterization of the CD4+ and CD8+ tumor infiltrating lymphocytes propagated with bispecific monoclonal antibodies.

To study the CD4+ and CD8+ tumor infiltrating lymphocytes (TIL) in the antitumor response, we propagated these subsets directly from tumor tissues with anti-CD3:anti-CD8 (CD3,8) and anti-CD3:anti-CD4 (CD3,4) bispecific mAb (BSMAB). CD3,8 BSMAB cause selective cytolysis of CD8+ lymphocytes by bridging the CD8 molecules of target lymphocytes to the CD3 molecular complex of cytolytic T lymphocytes with concurrent activation and proliferation of residual CD3+CD4+ T lymphocytes. Similarly, CD3,4 BSMAB cause selective lysis of CD4+ lymphocytes whereas concurrently activating the residual CD3+CD8+ T cells. Small tumor fragments from four malignant melanoma and three renal cell carcinoma patients were cultured in medium containing CD3,8 + IL-2, CD3,4 + IL-2, or IL-2 alone. CD3,8 led to selective propagation of the CD4+ TIL whereas CD3,4 led to selective propagation of the CD8+ TIL from each of the tumors. The phenotypes of the TIL subset cultures were generally stable when assayed over a 1 to 3 months period and after further expansion with anti-CD3 mAb or lectins. Specific 51Cr release of labeled target cells that were bridged to the CD3 molecular complexes of TIL suggested that both CD4+ and CD8+ TIL cultures have the capacity of mediating cytolysis via their Ti/CD3 TCR complexes. In addition, both CD4+ and CD8+ TIL cultures from most patients caused substantial (greater than 20%) lysis of the NK-sensitive K562 cell line. The majority of CD4+ but not CD8+ TIL cultures also produced substantial lysis of the NK-resistant Daudi cell line. Lysis of the autologous tumor by the TIL subsets was assessed in two patients with malignant melanoma. The CD8+ TIL from one tumor demonstrated cytotoxic activity against the autologous tumor but negligible lysis of allogeneic melanoma targets. In conclusion, immunocompetent CD4+ and CD8+ TIL subsets can be isolated and expanded directly from small tumor fragments of malignant melanoma and renal cell carcinoma using BSMAB. The resultant TIL subsets can be further expanded for detailed studies or for adoptive immunotherapy.

Antibodies, Monoclonal↗

PubMed1989

Tryptophanyl-tRNA synthetase from Bacillus subtilis. Characterization and role of hydrophobicity in substrate recognition.

The tryptophanyl-tRNA synthetase from Bacillus subtilis was purified to homogeneity and characterized. It has an alpha 2 subunit structure and a molecular weight of 77,000. Tryptophanyl-tRNA synthetase does not catalyze any significant proofreading. It activates tryptophan as well as the three fluorinated analogues, DL-4-fluoro-, DL-5-fluoro-, or DL-6-fluorotryptophan (4F-, 5F-, and 6F-Trp), in the ATP-pyrophosphate exchange reaction. In the aminoacylation reaction, the fluorotryptophans act as competitive inhibitors of Trp. Their relative activities follow the same order in both reactions: Trp greater than 4F-Trp greater than 6F-Trp greater than 5F-Trp. This order is the inverse of the order of relative hydrophobicities of these compounds, pointing to the importance of hydrophobic interactions in the selective recognition by tryptophanyl-tRNA synthetase among this group of substrates. To define the physical basis of the relative hydrophobicities, the crystallographic structure of 4F-Trp was determined and compared to that of trptophan. Charge distributions calculated for tryptophan and its different fluoroanalogues on the basis of molecular structures were supported by their carbon-13 NMR spectra. Correlations between charge distributions and relative hydrophobicities suggest that the polarity of the C-F bond represents an underlying factor determining the hydrophobicities of 4F-, 5F-, and 6F-Trp, thus relating tryptophanyl-tRNA synthetase selectivity toward tryptophan and its fluoroanalogues directly to their electronic configurations.

Adenosine Monophosphate↗