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D A Lappi

Publications and source records attributed to D A Lappi.

71 records · Page 4Linked to original sources
PubMed1989

Biological and chemical characterization of basic FGF-saporin mitotoxin.

Basic fibroblast growth factor (FGF) and saporin-6, a ribosome-inactivating protein, were chemically conjugated and characterized as a cytotoxin to cells expressing the basic FGF receptor. Structural and Western blot analysis of the conjugate showed that it contained saporin and basic FGF in equimolar amounts. The conjugate inhibited protein synthesis in a cell-free system and had potent cytotoxic activity (ID50 = 25pM) for cells expressing the basic FGF receptor. It is equipotent with basic FGF in radioreceptor assays and elutes from heparin Sepharose columns with 2M NaCl. The activity of the mitotoxin can be inhibited by competition with an excess of basic FGF but not nerve growth factor. The possibility that this mitotoxin can be used as an anti-angiogenic factor in paradigms that involve basic FGF is discussed.

Animals↗
PubMed1989

In vivo effects in mice of an anti-T cell immunotoxin.

We have evaluated both the proliferative response as well as the Thy-1 Ag expression of lymphocytes from mice treated in vivo with an anti-Thy-1 immunotoxin (IT). The IT was a rat IgG2c mAb recognizing the Thy-1 Ag, disulfide-linked to a ribosome-inactivating protein isolated from the seeds of the plant Saponaria officinalis (soapwort). Toxicity studies showed that a single i.v. injection of doses up to 20 micrograms IT/mouse was well tolerated and allowed indefinite survival. The Con A-induced proliferative response of spleen cells from mice killed 1 day after treatment with sublethal doses of IT was inhibited in a dose-dependent manner, with complete inhibition observed at doses of greater than or equal to 5 micrograms IT/mouse. Control experiments showed that the inhibition was due to the IT and not to its single components. Moreover, the IT effect was abolished by a large (100-fold) excess of anti-Thy-1 mAb alone given concurrently, but not by an unrelated, isotype-matched rat mAb. At all IT doses, the proliferative response to a B cell mitogen (LPS) was normal. Kinetic studies showed a time- and dose-dependent reconstitution of Con A responsiveness. In limiting dilution cultures of spleen cells from mice treated with 5 micrograms IT 1 or 4 days before death, a 97% depletion of T lymphocytes capable of proliferation was observed. Limiting dilution cultures showed that also the thymus of IT-treated mice was depleted by more than 90% of growth-competent T lymphocytes. Cytofluorographic studies of Thy-1+ cells from the spleens of IT-treated mice gave results which did not correlate with those obtained in functional assays. Thus, a dose-dependent reduction, followed by a time-dependent reconstitution of Thy-1+ cells was observed in this case too, but the depletion occurred at later time points and was less complete than that observed in functional assays. Moreover, the mean fluorescence intensity of the residual Thy-1+ cells decreased below normal levels.

Animals↗
PubMed1989

B-cell restricted saporin immunotoxins: activity against B-cell lines and chronic lymphocytic leukemia cells.

B cell-restricted immunotoxins were constructed by conjugating anti-B monoclonal antibodies to saporin, the major ribosome inactivating protein from the seeds of the plant Saponaria officinalis. HD37-SAP is directed against CD19, the broadest B cell-specific determinant. HD39-SAP and HD6-SAP recognize two different epitopes on the CD22 molecule, an antigen present on the cell surface of B cells at late stages of differentiation. All three immunotoxins inhibited DNA synthesis and protein synthesis in target B lymphoma cells with a dose-related effect, in short incubation times and in the absence of potentiators. A clonogenic assay demonstrated that all immunotoxins could eliminate more than two logs of clonogenic malignant B cells with a two-hour incubation at concentrations not toxic to cells not bearing target antigens. The immunotoxin activity was evaluated by DNA synthesis inhibition in fresh B-chronic lymphocytic leukemia cells (B-CLL) stimulated to proliferate by incubation with an antibody specific for the receptor of C3b complement component (CR1) plus B cell growth factor. B-CLL cell DNA synthesis was actively inhibited by treatment at low immunotoxin concentration without need of potentiators. Immunotoxins exerted their effect also in whole blood of CLL patients under conditions achievable in vivo. We conclude that B cell-restricted immunotoxins HD37-SAP, HD39-SAP, and HD6-SAP are good candidates for in vivo therapy of B-cell malignancies.

Antibodies, Monoclonal↗
PubMed1989

Selective killing of CD4+ and CD8+ cells with immunotoxins containing saporin.

Saporin, a ribosome-inactivating protein from the seeds of Saponaria officinalis, was covalently linked to an anti-CD4 monoclonal antibody. The resulting immunotoxin at 10(-9)M concentration was toxic to CD4+ lymphocytes without affecting other cells. Selective elimination of CD4+ and CD8+ cells was also obtained with murine monoclonal anti-CD4 and anti-CD8 antibodies and an immunotoxin consisting of saporin linked to an anti-mouse IgG antibody.

Antineoplastic Agents, Phytogenic↗
PubMed1988

Activity of a monoclonal antibody-saporin-6 conjugate against B-lymphoma cells.

A monoclonal antibody reactive with the immunoglobulin heavy chain (TEC IgM) has been conjugated to saporin-6 (SAP), which is the major ribosome-inactivating protein from the seeds of the plant Saponaria officinalis. Studies with Burkitt's lymphoma cell line Bjab 113 demonstrate that this immunotoxin is capable of killing 3 logs (99.9%) of clonogenic lymphoma cells after a 2-hour incubation. The presence of human bone marrow inhibits the activity of the conjugate. However, full potency of TEC IgM-SAP immunotoxin is restored by adding 1 mM amantadine to the incubation medium. The reaction is highly specific and is inhibited by the presence of excess anti-mu-antibody or human serum. Clonal growth of other Burkitt's lymphoma cell lines is inhibited to a lesser extent by the immunotoxin. The presence of surface IgM on the different cell lines is directly correlated to target cell killing by TEC IgM-SAP. Isolation of Bjab 113 clones surviving treatment demonstrates that only a minority are truly resistant and that the others randomly escape the treatment. The highly potent and specific activity of this conjugate in the presence of bone marrow buffy coat and its exceptionally rapid onset of action make this conjugate a good candidate for the ex vivo elimination of neoplastic cells from the bone marrow of non-Hodgkin's lymphoma patients.

Antibodies, Monoclonal↗
PubMed1988

Evaluation of antihuman T lymphocyte saporin immunotoxins potentially useful in human transplantation.

We have synthesized 3 immunotoxins (ITs) by covalently coupling the saporin-6 hemitoxin (SAP) to OKT11, SOT3, and SOT1a murine monoclonal antibodies that recognize human T lymphocyte CD2, CD3, and CD5 surface antigens, respectively. The resulting ITs, referred to as OKT11-SAP, SOT3-SAP, and SOT1a-SAP, are equally effective in inhibiting eukaryotic protein synthesis in a cell-free system, and all 3 ITs bind to human T lymphocytes in an almost comparable manner. However, these reagents differ markedly in their ability to kill target T lymphocytes as assessed by measuring the inhibition of DNA synthesis and growth of clonable T lymphocytes in response to mitogenic and allogeneic stimuli. Whereas the anti-CD2 IT, OKT11-SAP, shows moderate cytotoxicity against T lymphocytes, the anti-CD3 IT, SOT3-SAP, and the anti-CD5 IT, SOT1a-SAP, are highly effective in eliminating the same target cells. The concentrations inhibiting 50% (IC50) of T lymphocyte DNA synthesis are 60 nM, 4.5 nM, and 1.4 nM for OKT11-SAP, SOT3-SAP, and SOT1a-SAP, respectively. Among 3 tested lysosomotropic amines, i.e., ammonium chloride, chloroquine, and amantadine, the latter only moderately potentiates the cytotoxicity of SOT1a-SAP (IC50 0.36 nM). We show that the conditions under which T lymphocyte killing is accomplished require less than 10 min exposure of T lymphocytes to the ITs, in the absence of adjuvant molecules artificially added to the incubation medium and at physiologic culture pH. These experimental characteristics of unprecedented closeness to a physiologic in-vivo model are likely to reflect the biophysical properties of the SAP moiety of the ITs. We conclude that clinical studies are warranted to define the advantage of using SAP ITs over previously described immunoconjugates.

Amines↗
PubMed1988

Synthesis and characterization of an antihuman T-lymphocyte saporin immunotoxin (OKT1-SAP) with in vivo stability into nonhuman primates.

The authors conjugated, by a disulphide bond, the antihuman T-lymphocyte (CD5) monoclonal antibody (MoAb) OKT1 to the saporin-6 (SAP) ribosome-inactivating protein of the plant Saponaria officinalis. The resulting OKT1-SAP immunotoxin bound to CD5-expressing target cells and under standard culture conditions specifically suppressed mitogen-induced-T-lymphocyte DNA and protein synthesis in a dose-related manner. T-lymphocyte killing was achieved by five-minute exposure of the target cells to OKT1-SAP. The concentration inhibiting 50% (IC50) of T-lymphocyte DNA synthesis was 0.32 nmol/L. The potency of OKT1-SAP was moderately enhanced by amantadine (IC50 0.08 nmol/L) but not by ammonium chloride or chloroquine. Whole blood components did not interfere with the efficacy of OKT1-SAP, as in vitro treatment of fresh whole blood resulted in effective elimination of clonable peripheral blood T-lymphocytes assessed by a limiting dilution assay. Because these characteristics of T-lymphocyte killing by OKT1-SAP (ie, rapidity of action, potency also without potentiators) and lack of inhibition by whole blood components may be relevant for the use of an immunotoxin as a therapeutic agent in humans, the authors evaluated the stability in vivo and the circulatory clearance of OKT1-SAP in cynomolgus monkeys. Following a single intravenous (IV) injection of nontoxic dosages (0.16 to 1.3 mg/kg), an initial rapid decline (t1/2 alpha = 1.0 to 4.1 hours) was followed by a long-lasting slower decrease (t1/2 beta = 11.6 to 20.6 hours) of OKT1-SAP plasma concentrations as detected by double-antibody solid phase enzyme-linked immunosorbent assay (ELISA) assay. Not only did OKT1-SAP remain intact immunologically but it also retained its biological activity, as measured by the ability of plasma samples from monkeys given immunotoxin to inhibit DNA synthesis in human T-lymphocytes. Taken together the findings presented in this article indicate the feasibility of using OKT1-SAP as a therapeutic tool and provide information that will facilitate the rational use of immunotoxins as a treatment modality in humans.

Animals↗
PubMed1986

Expression of the human apolipoprotein AI gene fused to the E. coli gene for beta-galactosidase.

The human apoAI gene was expressed in E. coli by in-frame fusion to a modified beta-galactosidase gene present in plasmid pUR291. The fused beta-galactosidase-apoAI gene product was expressed at a high level and was recognized by an anti-human apoAI antiserum. Besides the fused protein, at least one degradation product having an Mr similar to that of beta-galactosidase was present in high amounts in bacterial extracts. These results and those of a pulse-chase experiment indicate that degradation took place only in the apoAI moiety of the chimeric protein.

Apolipoprotein A-I↗
PubMed1985

Characterization of a Saponaria officinalis seed ribosome-inactivating protein: immunoreactivity and sequence homologies.

A ribosome inactivating protein from Saponaria officinalis, SO-6, was purified and the N-terminus sequenced. The sequence shows extensive homology with Pokeweed antiviral protein, Pokeweed antiviral protein II, Pokeweed antiviral seed protein and dodecandrin. SDS gel electrophoresis in the Laemmli system revealed two bands of similar intensities with a smear between them, probably an artifact due to the high pI of the protein. Use of a harsher denaturing gel system resulted in one band in electrophoresis. Immune antisera was raised in rabbits against this protein and it cross reacted with other proteins (SO-5, SO-8 and SO-9) from seeds of Saponaria officinalis, but not with gelonin, Momordica charantia inhibitor and dianthin 32.

Amino Acid Sequence↗
PubMed1985

Plasmid pFCE4: a new system of Escherichia coli expression-modification vectors.

Two versatile expression-modification vectors were obtained by inserting the origin of replication (ori) of phage f1 into the expression vector pOTS. The resulting plasmids produce large amounts of coding or noncoding ssDNA (depending on ori orientation in pFCE4+ and pFCE4-) and excrete it into the medium as virus-like particles following infection with phage f1. These features make them suitable for dideoxy chain termination sequencing, oligonucleotide directed mutagenesis and gene expression without further manipulations. The human IFN alpha-2 gene, lacking the codon for the first amino acid, cysteine, was efficiently expressed by these vectors.

Base Sequence↗
PubMed1980

Reduced nicotinamide 8-(alkylamino)adenine dinucleotides: enzyme-coenzyme interactions with different adenyl glycosyl bond conformations.

Enzyme binding studies have been conducted on several reduced nicotinamide adenine dinucleotide analogues having different substitutions at the 8 position of the adenine. The following analogues were synthesized for this study: 8-bromo-, 8-(methylamino)-, 8-(dimethylamino)-, and 8-(ethylamino)-substituted NADH. The conformation of these analogues was also studied. 1H and 13C nuclear magnetic resonance analysis showed that there was rotation about the adenine glycosyl bond and that the rotational preference depended on the C8 substituent. The bromo and dimethylamino analogues were predominantly in the syn conformation, while the anti conformation prevailed in the other derivatives as it does in the native NADH. Use of these analogues as co-enzymes by Pseudomonas aeruginosa transhydrogenase, Beneckea harveyi FMN:NADH oxidoreductase, rabbit muscle lactate dehydrogenase, beef heart lactate dehydrogenase, horse liver alcohol dehydrogenase, and yeast alcohol dehydrogenase resulted in enzyme activity in all cases. The bromo and dimethylamino analogues were bound significantly tighter than the other analogues for at least two of the enzymes studied. The data are discussed with respect to the ability of these enzymes to bind nucleotides which are in the syn conformation.

Animals↗
PubMed1978

The disulfide bond connecting the chains of ricin.

Studies on the disulfide bond connecting the two polypeptide chains of ricin are reported. Reduction of this bond in the native protein requires approximately 50-fold more mercaptoethanol than the reduction of the bond in the protein denatured by sodium dodecyl sulfate. An improved procedure for the formation of this disulfide bond from recombined chains is reported. A and B chains spontaneously and rapidly reassociate into a stable complex with a sedimentation velocity similar to that of native oxidized ricin before the disulfide bond reforms. The mixture of both chains also behaves on Bio-Gel P-100 like native oxidized ricin. However, the complex formed by the two chains, assayed before the disulfide bond can reform, and reduced ricin, carboxymethylated to prevent reoxidation, shows a significant decrease in toxicity to mice and a decrease in ability to inhibit protein synthesis in HeLa cells in culture.

Disulfides↗
PubMed1977

Investigations into the relationship between structure and function of diphtheria toxin.

Studies on the structure-function relationship of diphtheria toxin are reported. New methods are described for the preparation of pure intact ("unnicked") toxin and for the preparation of the individual A and B chains. A biological assay method for the B chain is also presented, as well as a method for the labelling of "nicked" (one peptide bond broken) diphtheria toxin with 131I such that the label is confined to only one of the two polypeptide chains. Alterations of diphtheria toxin with specific reagents reveal that modifications of the tryptophan, methionine, and arginine residues did not result in a significant loss in toxicity, whereas treatment of the toxin with omicron-phthalaldehyde or by photooxidation with rose bengal results in a complete loss of the toxic activity. Modification of tyrosine by iodination results in active toxin, whereas modification by tetranitromethane causes a loss in activity. Preliminary results also indicate that the isolated A chain is about an order of magnitude more active in incorporating adenosine diphosphoribose into translocase (elongation factor 2) than whole or nicked toxin is under identical conditions. The observed structural properties are discussed in view of the functional activity of diphtheria toxin in cell-free systems as well as in cell cultures. Evidence is presented indicating that the B chain binds to membranes: it inhibits the action of nicked toxin on HeLa cells.

Biological Assay↗
PubMedDate not supplied

Immunotoxin mediated killing of clonable T-lymphocytes infiltrating an irreversibly rejected human renal allograft.

We isolated and treated in vitro with a novel CD5-specific saporin immunotoxin, referred to as OKT1-SAP, the cells infiltrating an irreversibly rejected renal allograft from a patient who rejected while on cyclosporine plus steroids and then failed to respond to multiple courses of high-dose steroids, intravenous OKT3 antibody, and local irradiation to the graft. We report here that under experimental conditions achievable in vivo the immunotoxin OKT1-SAP was capable of eliminating in vitro more than 95% of clonable T-lymphocytes infiltrating the rejected allograft of this patient despite their resistance to previous aggressive immunosuppression. To our knowledge, this is the first report of an immunotoxin-mediated suppression of the clonogenic growth of rejected renal allograft infiltrating T-lymphocytes.

Adult↗