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Biomedical subjects

T W Chang

Publications and source records attributed to T W Chang.

At least 37 records · Page 2Linked to original sources
PubMed1995

Human IgA monoclonal antibodies specific for a major ragweed pollen antigen.

Human hybridoma cell lines secreting IgG specific for the major allergen in the pollen of short ragweed, Amb a I, were established from patients who had been receiving antigen injections for immunotherapy. Recombinant Ig genes were then constructed by cloning the heavy and light chain variable region genes of the human hybridoma cell line and joining them to the human alpha or kappa constant region genes in mammalian expression vectors. Amb a I-specific IgA was expressed in two mouse myeloma cell lines, NS0 and Sp2/0. In both systems, transfected alpha and kappa chains were assembled into IgA monomers or into dimers covalently linked by the endogenous murine J chains. We propose that recombinant IgA monoclonal antibodies specific for airborne allergens may be applied to the mucosal surface of the nasal linings or of the lower airway of sensitized individuals to inhibit the entry of allergenic molecules across the mucosal epithelium and, therefore, to prevent the development of allergic responses.

Allergens↗
PubMed1994

Pulsatile flow through a bifurcation with a cerebrovascular aneurysm.

Laser-Doppler velocimetry measurements and flow visualization were complementarily made in pulsatile and steady flow in a cerebrovascular aneurysm model with bifurcation angles of 60, 90, and 140 deg, and volume-flow rate ratios between the branches of 1 to 1 and 3 to 1. The mean, peak, and minimal Reynolds numbers based on the bulk average velocity and diameter of the parent vessel were 600, 800, and 280, respectively. For uneven branch flow, it is found that the flow activity inside the aneurysm and the stresses acting on the aneurysmal wall increase with increasing bifurcation angle. More importantly, the present angle suggests the presence of a critical bifurcation angle below which the aneurysm is prone to thrombosis, whereas above which the aneurysm is susceptible to progression or rupture. For evenly distributed branch flow, the intra-aneurysmal flow is sluggish and therefore prone to thrombosis for all studied bifurcation angles.

Aneurysm, Ruptured↗
PubMed1994

Construction and characterization of chimeric and humanized forms of a broadly neutralizing monoclonal antibody to HIV-1.

Murine monoclonal antibody (MAb) G3-519 has been shown to recognize a conserved neutralizing epitope in the fourth constant (C4) region of the external glycoprotein gp120 of HIV-1. Inasmuch as this antibody effectively neutralized the infectivity of diverse HIV-1 isolates, it has been selected to be developed for passive immunization against HIV-1 infection in humans. In order to minimize the problem of immunogenicity of murine antibodies and to confer additional accessory immune functions, we have constructed mouse/human chimeric and humanized forms of the antibody. The chimeric antibody was constructed by cloning the murine variable regions and replacing the mouse constant regions with those from human Ig gamma 1,kappa. The humanized antibody was constructed using the human KAS variable region framework sequences as template. Engineering was guided by a three dimensional model of the murine variable region. The murine, chimeric and humanized forms of the antibody exhibited similar reactivity with the peptidic antigen in ELISA, and comparably neutralized the infectivity of HIV-1 in vitro. Taken together, our results show that the chimeric and humanized forms of G3-519 essentially retain the binding activity of the mouse parental antibody. Clinical development is planned to assess the prophylactic and therapeutic usefulness of these reshaped antibodies in humans.

Amino Acid Sequence↗
PubMed1993

Can anti-IgE be used to treat allergy?

A summary of the properties of CGP 51901 is shown in Table 3. On the basis of its binding to IgE and IgE-secreting cells and its activity in vitro and in vivo, CGP 51901 is expected to be able to decrease serum IgE by direct clearance of IgE and by reduction of the numbers and productivity of IgE-secreting cells. The end result of reduction of IgE in the circulation and on mast cells is expected to be the attenuation of IgE-mediated reactions and the improvement in allergy symptoms. The effective serum concentration of CGP 51901 is expected to be in the range 1-10 micrograms/ml. Because CGP 51901 is an antibody specific for IgE, it is expected to be highly selective in its activity. Because IgE does not appear to be essential and because CGP 51901 has been rigorously tested to confirm its non-anaphylactic nature, this treatment is not expected to have any adverse effects. Therefore, CGP 51901 is expected to be safe and to have a good probability of being effective when it is tested in human clinical trials.

Animals↗
PubMed1993

Pharmacokinetics of an HIV-1 gp120-specific chimeric antibody in patients with HIV-1 disease.

The pharmacokinetics of mouse V/human C (gamma 1, kappa) chimeric monoclonal antibody CGP 47 439 specific for the principal neutralizing determinant of human immunodeficiency virus type 1 (HIV-1) was studied in patients with stage IV HIV-1 disease in an open-labeled phase I/IIA trial. Twelve male patients were enrolled and nine completed the study. Patients were divided into three groups according to the extent of CGP 47 439 to bind to gp120 from their viral isolates: undetectable for group 1, modestly reactive for group 2, and strongly reactive for group 3. A first dose of 1, 10, or 25 mg was administered by intravenous infusion to group 1, group 2 and group 3 patients, respectively. The patients then received seven doses of 50, 100, or 200 mg, respectively, every three weeks. CGP 47 439 serum concentrations were determined by an ELISA using monoclonal antibody AB19-4 specific for the idiotope of CGP 47 439. Half an hour after infusion only 25.5-36.1% of the administered antibody was found in the serum, reflecting its rapid distribution in the extravascular space and possibly binding to gp120 antigen in some of the patients. The terminal elimination half-life (T1/2) was 16.2 days in group 1 patients, 9.7 days in group 2 and in group 3 patients 7.5 days and 9.1 days. An antibody response to CGP 47 439 was not a factor in determining elimination rates, because only very low and transient responses were found in three patients. These results suggest that the reactivity of CGP 47 439 with HIV-1 gp120 contributed to its elimination in HIV-1 infected patients.

Adult↗
PubMed1993

Immune enhancers composed of polyvalent binding sites of anti-CD3 antibodies.

Anti-CD3 antibodies of some IgG subclasses are very potent T lymphocyte mitogens in vitro and, seemingly contradictorily, very effective immunosuppressive agents in vivo. Using hamster anti-murine CD3 monoclonal antibody, 2C11, as a model, we have found that 2C11.IgG, or its F(ab')2 fragment, coupled to microbeads can provide short-term and vigorous activation of T cells and expansion of the lymphoid system in vivo. In contrast to free 2C11.IgG, these conjugates do not kill mice and cause T cell depletion, and can enhance immune responses. This study suggests that properly modified anti-CD3 antibodies can serve as in vivo immune system enhancers potentially useful in the treatment of cancer and chronic infectious diseases.

Animals↗
PubMed1993

Analysis of the Drosophila gene for the laminin B1 chain.

We have isolated and sequenced a Drosophila genomic DNA that encodes the entire coding region of the laminin B1 chain. The genomic DNA sequenced spans 11,787 bp, including a 1.1-kb 5'-flanking region, 5 exons, 4 introns, and a 1.4-kb 3'-flanking region. The open reading frame is within the two largest exons, the exons 3 and 4, while the first two and the last exons are much smaller and are untranslated. The structure of the Drosophila laminin B1 gene is similar to the Drosophila laminin B2 gene. Their exon-intron lengths and Eco RI, Pst I restriction maps are quite conserved. Both of their open reading frames are very compact, and their first introns are much larger than all of the rest of the introns. These results are consistent with the suggestion that the B1 and B2 genes could be derived from an ancestral gene. The similarity of the proximal 5'-flanking regions of the Drosophila B1 and B2 genes is 46.6%. Also, similar sequences of transcriptional regulatory elements, even though not site conserved, are found in both proximal 5'-flanking regions of the B1 and B2 genes. When transfected into Drosophila SL-2 cells, pCAT plasmid containing 1,048 bp of 5'-flanking region shows a strong expression of chloramphenicol acetyltransferase (CAT) activity. The deletion clones that contain sequences between nucleotides -462 to +150, and -282 to +150 all show strong CAT activity. These results suggest that this 5'-flanking promoter region may contain DNA sequences that can promote the expression of the laminin B1 gene.

Amino Acid Sequence↗
PubMed1993

hu-PBL-SCID mice can be protected from HIV-1 infection by passive transfer of monoclonal antibody to the principal neutralizing determinant of envelope gp120.

OBJECTIVE: To determine whether passive transfer of a monoclonal antibody specific for the principal neutralizing determinant in the V3 region of HIV-1IIIB gp120 can protect mice with severe combined immunodeficiency (SCID) transplanted with normal human peripheral blood leukocytes (hu-PBL), designated hu-PBL-SCID mice, from subsequent challenge with the homologous viral strain. DESIGN AND METHODS: hu-PBL-SCID mice were given intraperitoneal injections of an anti-HIV-1 neutralizing murine monoclonal antibody (BAT123), its mouse-human chimeric form (CGP 47 439), or a control murine antibody (PNTU), at a dose of 40 mg/kg. The mice were then challenged intraperitoneally with 10 mouse infectious doses of HIV-1IIIB. Three weeks later the mice were killed, and spleen cells and peritoneal lavage collected for determination of infection by coculture for viral isolation and by detection of HIV-1 DNA using polymerase chain reaction (PCR). RESULTS: All three antibodies had similar serum half-lives of 9-12 days. No toxicity was observed in the animals. HIV-1 was recovered by coculture from five out of the six mice given PNTU, and by PCR from two out of the six mice given PNTU, but was not recovered by either technique from any of the 12 mice given BAT123 or CGP 47 439. CONCLUSION: BAT123 and CGP 47 439, which are specific for the principal neutralizing determinant of HIV-1IIIB, protect hu-PBL-SCID mice from infection by this viral strain. Our findings support the use of the hu-PBL-SCID mouse as an in vivo model for studying protection against HIV-1 infection by passive immunization with anti-HIV-1 neutralizing antibodies.

Animals↗
PubMed1993

Comparison of two different trauma assessment scores in predicting trauma outcome.

We reviewed 1,455 trauma cases admitted through the Emergency Department of National Cheng Kung University Hospital from June 1988 to December 1991. Of these, 1,251 patients had Revised Trauma Scores (RTS) and 1,452 cases had Injury Severity Scores (ISS) available for analysis of final trauma outcome. Several statistical methods such as simple logistic regression, the contingency table approach, and stepwise logistic regression were adopted to obtain the critical regions of major trauma which satisfied the requirements for sensitivity and specificity with the largest probability of a correct classification. We found that RTS < or = 5.7 and ISS > or = 17 were the best critical regions for defining major trauma. These patients deserve more attention during prehospital and interhospital disposition. Moreover, RTS contributes more to the prediction of patient outcome than ISS, indicating the power of RTS at the time of field evaluation in predicting patients' survival probability. The ISS is calculated retrospectively and is of limited value in acute settings. Therefore, based on our trauma database, we recommended that the RTS be used as a triage tool to select severely ill patients. We also urge that a generalized trauma registry be established in order to validate its usefulness.

Humans↗
PubMed1992

Human mb-1 gene: complete cDNA sequence and its expression in B cells bearing membrane Ig of various isotypes.

The transmembrane protein, IgM-alpha, a product of mb-1 gene, has been shown to be specifically associated with membrane-bound IgM on the plasma membrane of B lymphocytes. Recent studies have suggested that IgM-alpha may play a role in transducing signals from the Ag receptors during the activation of B cells. A large amount of information has been obtained in the mouse system regarding IgM-alpha and other components of the newly conceived B cell Ag receptor complex. Here we report the cloning and the nucleotide sequencing of cDNA clones of human mb-1, covering the entire length of the mRNA. At the amino acid sequence level, human and murine mb-1 share a high homology in their transmembrane and intracytoplasmic segments, suggesting an important biologic function for these regions of mb-1. A major difference, mainly in the 3' untranslated part, exists between our cDNA sequence and the published partial human mb-1 cDNA sequence. It has also been observed that human mb-1 is expressed not only by B cell lines expressing membrane-bound Ig of mu and delta isotypes but also those expressing membrane-bound Ig of alpha and gamma isotypes.

Amino Acid Sequence↗
PubMed1992

A new isoform of human membrane-bound IgE.

The epsilon-chain of membrane-bound IgE on the surface of B lymphocytes is known to contain a membrane-anchoring peptide segment that is encoded by two membrane exons, me.1 and me.2. In analyzing pertinent segments in mRNA from human IgE-expressing B cells by using PCR methods and Northern blotting analyses, we have identified three species of mRNA of epsilon-chain with variations in the splicing of the membrane exons. The conventional species (m/s) contains the predicted me.1 and me.2; species m/1 harbors 156 extra nucleotides 5' of me.1 with unaltered reading frame; species s/t lacks me.1 and hence the segment encoding the hydrophobic transmembrane stretch and contains a shifted me.2 reading frame. Rabbit antibodies, which were prepared by immunization using a peptide of 36 amino acid residues representing an encoded segment unique to mRNA species m/l, could specifically bind to human IgE-expressing B cell lines and react with an epsilon-chain on Western immunoblots. These results indicate that there exists a previously unidentified isoform of human membrane-bound IgE.

Amino Acid Sequence↗
PubMed1992

Mouse/human chimeric anti-HIV-1 gp120 antibody to the principal neutralizing determinant: tolerability and pharmacokinetics in cynomolgus monkeys, Macaca fascicularis.

In preparing for testing a pharmaceutical grade preparation of chimeric (mouse/human) antibody CGP 47,439 in HIV-1 infected individuals, it was administered to Macaca fascicularis (cynomolgus) monkeys to study tolerability, immunogenicity and pharmacokinetics. Four groups of monkeys, three males and three females per group, received respectively four infusions of 0, 1.43, 4.3, and 14.3 mg of CGP 47,439/kg body weight at one-week intervals. The chimeric antibody induced no fever, was tolerated well throughout the 50-day observation period, elicited no tissue damage and no anti-antibody response. The pharmacokinetic profile was similar at all dose levels with a mean T1/2 alpha of 14.2 h (range 11.8-19.3 h) and a mean T1/2 beta of 172.6 h (range 137.2-220.5h). Following four successive antibody infusions serum concentrations of CGP 47,439 increased without reaching a steady state, and its measured concentrations were comparable to the simulated values. Collectively the study has provided safety and pharmacokinetic data that would allow human studies with this antibody in AIDS patients.

Animals↗
PubMed1992

Potential use of immunoconjugates for AIDS therapy.

More than a dozen of hybrid proteins possessing reactivity with human immunodeficiency virus-type 1-(HIV-1) infected cells and cytotoxicity have been produced and studied by several groups. These proteins are prepared either by chemical cross-linking of a toxin and a carrier molecule or by expressing fused genes of the two moieties. These cytotoxic agents have been investigated to eliminate HIV-1-infected cells in vitro. The ID50 of these agents range from pM to nM. This article compares the results of the various approaches and discusses the limits and potential of immunoconjugates for AIDS therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Identification and characterization of a neutralization site within the second variable region of human immunodeficiency virus type 1 gp120.

Two monoclonal antibodies designated BAT085 and G3-136 were raised by immunizing BALB/c mice with gp120 purified from human immunodeficiency virus type 1 (HIV-1) IIIB-infected H9 cell extracts. Among three HIV-1 laboratory isolates (IIIB, MN, and RF), BAT085 neutralized only IIIB infection of CEM-SS cells, whereas G3-136 neutralized both IIIB and RF. These antibodies also neutralized a few primary HIV-1 isolates in the infection of activated human peripheral blood mononuclear cells. In indirect immunofluorescence assays, BAT085 bound to H9 cells infected with IIIB or MN, while G3-136 bound to H9 cells infected with IIIB or RF, but not MN. Using sequence-overlapping synthetic peptides of HIV-1 IIIB gp120, the binding site of BAT085 and G3-136 was mapped to a peptidic segment in the V2 region (amino acid residues 169 to 183). The binding of these antibodies to immobilized gp120 was not inhibited by the antibodies directed to the principal neutralization determinant in the V3 region or to the CD4-binding domain of gp120. In a competition enzyme-linked immunosorbent assay, soluble CD4 inhibited G3-136 but not BAT085 from binding to gp120. Deglycosylation of gp120 by endo-beta-N-acetylglucosaminidase H or reduction of gp120 by dithiothreitol diminished its reactivity with G3-136 but not with BAT085. These results indicate that the V2 region of gp120 contains multiple neutralization determinants recognized by antibodies in both a conformation-dependent and -independent manner.

Amino Acid Sequence↗
PubMed1992

Blood levels of platelet-activating factor in endotoxin-sensitive and endotoxin-resistant mice during endotoxemia.

Platelet-activating factor (PAF) is a phosphoglyceride secreted by a variety of cells and has been implicated in endotoxin toxicities. To further confirm its role in endotoxin-induced tissue injuries and death, we conducted an experiment on endotoxin-resistant (C3H/HeJ strain) and endotoxin-sensitive (C3H/HeN strain) mice. The experiment consisted of three parts: 1) the LD50 of endotoxin from E. coli 0127:B8 cells was quantitated in C3H/HeN mice; 2) the lethality of PAF in C3H/HeJ mice at a dose lethal to C3H/HeN mice was determined; and 3) the blood levels of PAF in C3H/HeJ and C3H/HeN mice were measured after a dose of endotoxin lethal to the C3H/HeN strain was injected. PAF contained in the blood samples was extracted by a solid phase procedure and assayed by a radioimmunoassay method. The results showed that endotoxin-resistant and endotoxin-sensitive mice were equally susceptible to death induced by the same lethal dose of PAF. After injection with endotoxin, the blood PAF levels in C3H/HeN mice increased significantly (p < 0.01) at 60 minutes and 90 minutes, with a peak level three times that of the control group. The blood PAF levels in C3H/HeJ mice, however, remained unelevated throughout the experiment. The timing of the occurrence of the peak blood PAF level in the C3H/HeN mice corresponded with the emergence of their illness from the endotoxin injection. These findings shed new light on our understanding of the resistant mechanisms of C3H/HeJ mice to bacterial endotoxin and affirm the possible role of PAF in mediating endotoxin toxicities.

Animals↗