[Effects of autologous plasma and gentamicin on immunophenotype and viability of cytokine-induced killer cells]

OBJECTIVE

To investigate the effects of treatment with different volumes of autologous plasma and gentamicin on immunophenotype and viability of cytokine-induced killer (CIK) cells in vitro.

METHODS

Flow cytometry (FCM) was used to analyze the effects of autologous plasma and gentamicin on different immunocyte subtypes of CIK cells. The cell count method and MTT assay were used to detect the cytotoxicity of such pretreated CIK cells on HeLa cells.

RESULTS

No significance was found in the relative amount of immunocyte subtypes CD3(+), CD56(+), CD3(+)CD4(+), CD3(+)CD8(+), CD3(+)CD56(+), CD4(+)CD25(+) between autologous plasma and control groups. Compared with control group, CD3(+), CD56(+), CD3(+)CD8(+), CD3(+)CD56(+) cells of gentamicin group were significantly down-regulated by 1.4, 1.7, 1.4 and 2.5 folds (P<0.05), respectively. Furthermore, the cytotoxicity of CIK cells in gentamicin and control groups on HeLa cells were 43.0% and 90.0%, respectively, with a statistically significant difference (P<0.05).

CONCLUSION

Autologous plasma has little effect on different subtypes of CIK cells. On the contrary, gentamicin can cause a decrease in the number of CD3(+), CD56(+), CD3(+)CD8(+), CD3(+)CD56(+) cells with some cytotoxicity.

A nonradioactive, cell-free method for measuring protein synthesis inhibition by Pseudomonas exotoxin

Pseudomonas exotoxin A (PE) inhibits protein synthesis by NAD-dependent ADP-ribosylation of eukaryotic elongation factor 2. Traditionally, toxin activity has been characterized, either in living cells or cell-free systems, using radioactive compounds for quantification. The increased costs of radioactive waste disposal together with heightened security concerns have made the use of radioactive isotopes less attractive for routine laboratory assays. We therefore adapted a cell-free rabbit reticulocyte in vitro transcription-translation system that utilizes a reporter (beta-galactosidase) to measure toxin activity. The assay for PE is rapid, scalable, log-linear, NAD dependent and can be used to assess the neutralizing activity of anti-PE antibody preparations.

Production and characterization of a noncytotoxic deletion variant of the Aspergillus fumigatus allergen Aspf1 displaying reduced IgE binding

Aspergillus fumigatus is responsible for many allergic respiratory diseases, the most notable of which - due to its severity - is allergic bronchopulmonary aspergillosis. Aspf1 is a major allergen of this fungus: this 149-amino acid protein belongs to the ribotoxin family, whose best characterized member is alpha-sarcin (EC 3.1.27.10). The proteins of this group are cytotoxic ribonucleases that degrade a unique bond in ribosomal RNA impairing protein biosynthesis. Aspf1 and its deletion mutant Aspf1Delta(7-22) have been produced as recombinant proteins; the deleted region corresponds to an exposed beta-hairpin. The conformation of these two proteins has been studied by CD and fluorescence spectroscopy. Their enzymatic activity and cytotoxicity against human rhabdomyosarcoma cells was also measured and their allergenic properties have been studied by using 58 individual sera of patients sensitized to Aspergillus. Aspf1Delta(7-22) lacks cytotoxicity and shows a remarkably reduced IgE reactivity. From these studies it can be concluded that the deleted beta-hairpin is involved in ribosome recognition and is a significant allergenic region.

Bioactivities of ricin retained and its immunoreactivity to anti-ricin polyclonal antibodies alleviated through pegylation

Ricin has long been employed to construct immunotoxins, whose efficacy was often undermined by immunogenicity. Pegylation (modification of proteins with polyethylene glycol, PEG) was one of those recently developed approaches to circumvent immunogenicity of legions of drugs. Herein, pegylation of ricin was found to have barely changed the RNA N-glycosidase activity and protein synthesis inhibiting activity of ricin, but remarkably altered the cytotoxicity of ricin on hepatoma cell line (BEL7404) or the immunoreactivity with polyclonal anti-ricin antibodies. This result suggested that the attached PEG or monomethyloxyl polyethylene glycol (mPEG) groups did not hinder ricin from hydrolyzing ribosomal RNA, but indeed covered some areas on the surface of ricin molecule, including those involved in the interaction with cellular receptors and epitopes recognized by polyclonal antibodies. Pegylation, masking certain epitopes of ricin, might contribute to alleviate the immunogenicity of the toxin. Approach in this work, if applied to thereby constructed immunotoxins, would help improve the prospective efficacy of these toxins.

Nitric oxide-dependent ribosomal RNA cleavage is associated with inhibition of ribosomal peptidyl transferase activity in ANA-1 murine macrophages

NO can regulate specific cellular functions by altering transcriptional programs and protein reactivity. With respect to global cellular processes, NO has also been demonstrated to inhibit total protein synthesis and cell proliferation. The underlying mechanisms are unknown. In a system of ANA-1 murine macrophages, iNOS expression and NO production were induced by exposure to endotoxin (LPS). In selected instances, cells were exposed to an exogenous NO donor, S-nitroso-N-acetylpenicillamine or a substrate inhibitor of NO synthesis. Cellular exposure to NO, from both endogenous and exogenous sources, was associated with a significant time-dependent decrease in total protein synthesis and cell proliferation. Gene transcription was unaltered. In parallel with decreased protein synthesis, cells exhibited a distinctive cleavage pattern of 28S and 18S rRNA that were the result of two distinct cuts in both 28S and 18S rRNA. Total levels of intact 28S rRNA, 18S rRNA, and the composite 60S ribosome were significantly decreased in the setting of cell exposure to NO. Finally, 60S ribosome-associated peptidyl transferase activity, a key enzyme for peptide chain elongation, was also significantly decreased. Our data suggest that NO-mediated cleavage of 28S and 18S rRNA results in decreased 60S ribosome associated peptidyl transferase activity and inhibition of total protein synthesis.

Expression and cellular distribution of perchloric acid-soluble protein is dependent on the cell-proliferating states of NRK-52E cells

To clarify the biological role of kidney perchloric acid-soluble protein 1 (K-PSP1), its expression and intracellular distribution were examined in normal rat kidney epithelial NRK-52E cells. K-PSP1 expression was low during the proliferating phase and high in the stationary phase, and shown to have a negative relationship with the protein-synthesizing activity of the cells. Immunocytochemical studies revealed that K-PSP1 is predominantly located in the cytosol, especially in endoplasmic reticulum and Golgi apparatus of proliferating cells. In the stationary phase, K-PSP1 was not detected immunologically even though protein and mRNA expression were high. This disappearance of reactivity with anti-serum seems to be due to a conformational change in K-PSP1 induced by unknown factors. These results suggest that the role of K-PSP1 is to regulate cell proliferation, and this may be related to a previously reported ability to inhibit protein synthesis.

CpG oligodeoxynucleotides down-regulate macrophage class II MHC antigen processing

Unmethylated CpG motifs in bacterial DNA or short oligodeoxynucleotides (ODN) stimulate cells of the immune system and provide adjuvant activity. CpG DNA directly activates macrophages to secrete IL-12 and TNF-alpha and increases transcription of various genes, but its effects on macrophage Ag processing remain uncertain. The effects of CpG ODN on class II MHC (MHC-II) Ag processing and presentation were examined using peritoneal macrophages that were cultured for 18 h with CpG ODN and then pulsed with protein Ags. T cell hybridomas were used to detect presentation of specific peptide:MHC-II complexes. Both CpG ODN and LPS inhibited processing of bovine RNase and hen egg lysozyme. Presentation of exogenous peptides was inhibited to a lesser degree. Treatment of macrophages for 18 h with CpG ODN decreased surface MHC-II expression, as measured by flow cytometry. Furthermore, Northern blot analysis revealed that treatment with CpG ODN decreased I-Ak mRNA. Endocytosis by macrophages, as measured by uptake of fluorescent dextran, was not altered by treatment with CpG ODN. The inhibitory effect of CpG ODN on Ag processing was seen after prolonged (18 h) treatment of macrophages, but not after short treatment (e.g., 2 h) with CpG ODN and protein Ag. Enhancement of macrophage Ag processing was not seen at any time point of CpG ODN exposure, in contrast to data from other studies with dendritic cells. In summary, exposure of macrophages to CpG ODN results in a decrease in macrophage Ag processing and presentation, which is largely mediated by a decrease in synthesis of MHC-II molecules.

Lowering of trichosanthin immunogenicity by site-specific coupling to dextran

Trichosanthin is a type I ribosome-inactivating protein possessing a broad spectrum of biological and pharmacological activities. Therapeutic use of this compound is hampered by its immunogenicity. It was shown earlier that coupling of dextran to trichosanthin can increase plasma half-life and reduce antigenicity. However, the site where dextran attaches to trichosanthin cannot be controlled; ideally, it should be at or near the antigenic determinant. The present study attempted to couple dextran to trichosanthin at a potential antigenic site. By site-directed mutagenesis, two sites, R29 and K173, were replaced by cysteine, and dextran was coupled to the newly created cysteine residues. The dextran-trichosanthin complex retained 50% of abortifacient activity and had a mean residence time in rats 27-fold longer than natural trichosanthin. Acute hypersensitivity reaction in guinea pigs was reduced greatly after coupling of K173C (a trichosanthin mutant with lysine-173 replaced by cysteine) to dextran. Compared with natural trichosanthin, dextran-K173C had a decrease in IgG and IgE response, whereas the coupling of R29C (a trichosanthin mutant with arginine-29 replaced by cysteine) to dextran did not show significant reduction of immunogenicity. This suggests that K173 but not R29 is located at or near an antigenic determinant. This study has demonstrated an alternative approach for mapping of antigenic determinants. The information obtained is also useful in producing an improved trichosanthin derivative for therapeutic use.

Saccharomyces boulardii protease inhibits the effects of Clostridium difficile toxins A and B in human colonic mucosa

Saccharomyces boulardii is a nonpathogenic yeast used in the treatment of Clostridium difficile diarrhea and colitis. We have reported that S. boulardii inhibits C. difficile toxin A enteritis in rats by releasing a 54-kDa protease which digests the toxin A molecule and its brush border membrane (BBM) receptor (I. Castagliuolo, J. T. LaMont, S. T. Nikulasson, and C. Pothoulakis, Infect. Immun. 64:5225-5232, 1996). The aim of this study was to further evaluate the role of S. boulardii protease in preventing C. difficile toxin A enteritis in rat ileum and determine whether it protects human colonic mucosa from C. difficile toxins. A polyclonal rabbit antiserum raised against purified S. boulardii serine protease inhibited by 73% the proteolytic activity present in S. boulardii conditioned medium in vitro. The anti-protease immunoglobulin G (IgG) prevented the action of S. boulardii on toxin A-induced intestinal secretion and mucosal permeability to [3H]mannitol in rat ileal loops, while control rabbit IgG had no effect. The anti-protease IgG also prevented the effects of S. boulardii protease on digestion of toxins A and B and on binding of [3H]toxin A and [3H]toxin B to purified human colonic BBM. Purified S. boulardii protease reversed toxin A- and toxin B-induced inhibition of protein synthesis in human colonic (HT-29) cells. Furthermore, toxin A- and B-induced drops in transepithelial resistance in human colonic mucosa mounted in Ussing chambers were reversed by 60 and 68%, respectively, by preexposing the toxins to S. boulardii protease. We conclude that the protective effects of S. boulardii on C. difficile-induced inflammatory diarrhea in humans are due, at least in part, to proteolytic digestion of toxin A and B molecules by a secreted protease.

Ribonuclease activity dependent cytotoxicity of Asp fl, a major allergen of A. fumigatus

A major allergen/antigen, Asp fl, secreted by Aspergillus fumigatus exhibits cytotoxicity towards eukaryotic cell lines. Asp fl inhibited protein synthesis in RAW cells with an IC50 of 4.5 nM and also degraded ribosomal RNA of RAW cells at a similar concentration. Ribosomal inactivation by Asp fl may be the probable mechanism for protein synthesis inhibition. Specific ribonuclease activity of Asp fl was observed to be 100,000 U/mg. Presence of strong RNase activity in Asp fl was further confirmed by agar gels containing yeast RNA. Electrophoretic run on agarose gels showed that Asp fl degrades all species of naked RNA. Modification of histidine residues of Asp fl with diethyl pyrocarbonate and alkylation of cysteines with iodoacetamide resulted in loss of ribonuclease activity and cytotoxicity of Asp fl. The current study establishes the ribonuclease activity of a purified major allergen of A. fumigatus that inhibits protein synthesis and kills the eukaryotic cells.

Production and characterization of monoclonal antibodies against the ribosome-inactivating protein PAP from Phytolacca americana

Monoclonal antibodies specific to pokeweed antiviral protein (PAP), a ribosome-inactivating protein (RIP), were obtained after six unsuccessful fusions. A special procedure including injections of low doses of purified PAP from spring leaves in a short period was adopted. Some clones highly specific to PAP react with recombinant PAP. One clone cross-reacts with PAP-S isolated from seeds but none cross-reacts with the isoform PAP II isolated from summer leaves. These antibodies represent a useful tool to investigate the mechanisms of PAP biosynthesis and plant protection involving RIPs.

A new approach in the synthesis of immunotoxins: ribosome inactivating protein noncovalently bound to monoclonal antibody

This study describes the synthesis of a new generation of immunotoxins made by a noncovalent interaction between a monoclonal antibody derivatized with a dichlorotriazinic dye and the ribosomal inhibitor protein gelonin. The scheme of preparation has several advantages with respect to the traditional methods, which used heterobifunctional cross-linkers, such as a higher overall yield of production and the homogeneity of the obtained conjugate. Moreover, because no chemical derivatization of the gelonin was required, the unconjugated ribosome inactivating protein was recovered unaltered and therefore can be reused in other synthetic processes. This immunoconjugate was stable when tested in mouse serum and showed an interesting slow elimination rate when administered intravenously in mice. Although a high dye derivatization degree induced a modification of the specificity of the monoclonal antibody, the native specificity was restored after conjugation with gelonin. Furthermore the noncovalent linkage did not affect the gelonin inhibitory activity; in fact, the specific cytotoxic activity seemed to be similar to that of other disulfide-linked immunotoxins previously prepared in our laboratories.

Enhancement of eosinophil-mediated cytotoxicity to schistosomula of Schistosoma mansoni by autologous mononuclear cells from patients

Adherent mononuclear cells (monolayer), when co-cultured with autologous peripheral blood eosinophils isolated from patients treated for Schistosoma mansoni infections, enhanced the eosinophil-mediated killing of antibody coated schistosomula. The monolayer increased the activity of the eosinophils by 225%, and was observed in 80% of the patients studied. Heat labile factors other than complement, present in immune serum, further enhanced the ability of eosinophils to kill schistosomula in the presence of the monolayer. On their own the adherent cells did not mediate obvious damage to the parasite. Eosinophils that had been pre-incubated with the monolayer (100 mins) and tested separately, killed equal numbers of schistosomula as in the co-culture assay; this excludes the possibility of concurrent schistosomula cytotoxicity by the two cell populations. The ability of the monolayer to activate eosinophils was not altered by inhibitors of protein synthesis. The monolayer was largely consistent of monocytes as demonstrated by an over 96% positive staining for non-specific esterases.

The ribosome-inactivating, antiproliferative and teratogenic activities and immunoreactivities of a protein from seeds of Luffa aegyptiaca (Cucurbitaceae)

1. The protein isolated from Luffa aegyptiaca seeds was capable of inhibiting protein synthesis in a rabbit reticulocyte lysate system and [3H]thymidine uptake by mouse melanoma (B16) cells. 2. It also adversely affected the development of mouse embryos in culture. 3. In enzyme-linked immunosorbent assay it reacted with antisera raised against other ribosome-inactivating proteins.

A new 'solid phase' procedure to synthesize immunotoxins (antibody-ribosome inactivating protein conjugates)

A method to produce immunotoxins (conjugates comprising of a monoclonal antibody and toxin) using ribosome inactivating protein anchored on an affinity gel derivatized with triazinic dye is described. The adsorbed toxins were activated with 2-imino-thiolane and then conjugated to monoclonal antibody activated by SPDP. The "heterogeneous phase" system offered several advantages, reducing the usually required purification steps and opening a way to automatize the conjugation procedure.

Production and characterization of a monoclonal antibody against the ribosome inactivating protein alpha sarcin

In order to improve the purification of immunoconjugates containing alpha sarcin, a ribosome-inactivating protein, and in the attempt to define the enzymic region of the toxin, MAbs against alpha sarcin were produced. From 5 fusions, by adopting a short period of immunization and very low doses of the immunogen, 10 anti-toxin-producing clones were obtained. One of them, named MAsg2 (IgG2b), due to its specific reactivity and secreting properties, was selected for further characterization. MAsg2 was found to recognize an epitope which is common to two, i.e. alpha sarcin and clavatin, of the three different aspergillins tested, but is not involved in the active site of the toxins.

Design of liposome to improve encapsulation efficiency of gelonin and its effect on immunoreactivity and ribosome inactivating property

Gelonin, purified from the seeds of Gelonium multiflorum, using cation-exchange and gel-filtration chromatography was characterised for its purity, homogeneity and molecular weight by reverse-phase HPLC (RP-HPLC) and SDS-PAGE analysis. The HPLC purified gelonin was used for entrapment studies in the liposomes. Liposomes were prepared by reverse phase evaporation (REV) technique using three different types of lipid composition in the same molar ratio. The method resulted in 75-80% entrapment efficiency of gelonin in the liposomes. Entrapped and unentrapped gelonin was characterized for physico-chemical, immunochemical and biological properties. The immunoreactivity of entrapped gelonin was fully preserved but the ribosome-inactivating property was slightly inhibited. The method involved mild conditions, highly reproducible and the liposomes produced appeared to be stable for several months. It has important implications in the development of cell type specific cytotoxic agents where a chemical cross-linking is involved which significantly inhibits both immunoreactivity and ribosome-inactivating ability of the toxin.

Properties of a ribosome-inactivating protein, gelonin, purified using three different methods

Ribosome-inactivating protein, gelonin, isolated from an Indian plant Gelonium multiflorum of Euphorbiaceae family has been used to design and synthesize immunotoxins and hormonotoxins for selective targeting purposes. Since gelonin isolated by aqueous extraction, cation-exchange chromatography and gel-filtration chromatography (Method I), contains non-proteinous material absorbing at 280 nm, the ammonium sulphate precipitation method (Method II) and Cibacron blue affinity chromatography method. (Method III) have been used to purify gelonin from the dry seeds. Three batches of gelonin purified by each method were prepared and subjected to extensive physico-chemical and immunochemical characterization. The molecular weight was determined by gel-filtration chromatography on a pre-calibrated Sephadex G-100, TSK-G4000 TW on HPLC or Superose-12 on fast protein liquid chromatography. In all cases, the molecular weight was approximately 30,000Da. The SDS-PAGE also revealed a homogeneous protein of 30kDa molecular weight. In Method II, the non-proteinous material which binds to CMC-gel in association of gelonin was substantially removed during ammonium sulphate fractionation. A careful analysis clearly revealed that Method II, although yielded low protein, gave gelonin devoid of the non-proteinous material. The SPDP modification of epsilon-NH2 groups of gelonin obtained from Methods I, II, and III was also carried out and its effect on immunoreactivity was studied.

Immobilized cibacron blue--leachables, support stability and toxicity on cultured cells

Although immobilized dyes are widely used on the laboratory scale and have good potential for industrial applications, they are still subject to some reservations. Little information is available about dye leakage and toxicity, which seriously hinders the use of such supports in the production of pure proteins. Investigations of the leakage mechanism and the in vitro toxicity of the native dye and of that leached from the column are reported. The possible presence of traces of dye in the purified biological materials necessitates the availability of sensitive analytical tests. The preparation and preliminary isolation of dye antibodies as a first step in the development of an immunohistochemical assay of leached dyes are also described.

Characterization of a translation inhibitory protein from Luffa aegyptiaca

A protein with a molecular weight of about 30,000 was purified from the seeds of Luffa aegyptiaca. This protein inhibited cell free translation at pM concentrations. In spite of functional similarity to other ribosomal inhibitory proteins, the NH2-terminal analysis did not show any significant homology. Competitive inhibition studies indicate no immunological crossreactivity between the inhibitory protein from Luffa aegyptiaca, pokeweed antiviral protein (PAP) and recombinant ricin A chain. Chemical linkage of the protein to a monoclonal antibody reactive to transferrin receptor resulted in a highly cytotoxic conjugate.

Inhibition of natural killer cytotoxicity by extracellular ppp(A2'p5')nA oligonucleotides

The effect of purified 2'-5' linked polyadenylated oligomers on the human natural killer (NK) activity has been investigated. Permeabilization of NK cells to ppp(A2'p5')2A did not enhance their NK activity at any concentration tested. Furthermore, concentrations higher than 0.1 mM inhibited their NK activity. Similar results were obtained by pre-incubating non-permeabilized intact cells, indicating an extracellular effect of these compounds on cell membranes, which was further investigated. This inhibition by the oligomers was greater (50% inhibition was obtained with 50 micron), when they were added directly to the NK assay, than when the NK cells were pre-incubated. Similar inhibitory effects were observed with ppp(A2'p5')A and ppp(A2'p5')3A oligomers but not with the dephosphorylated "core" molecules or other nucleotides. The inhibition was completely or partially reversed by phorbol esters and by interferon (IFN), respectively. The inhibition was temperature and extracellular Ca2+ dependent. The oligomers did not inhibit the binding of the effector cells to the target cells. The programming for lysis was the step of the lytic mechanism affected, possibly due to the alteration of the Ca2+ influx into the NK cells observed in presence of the ppp(A2'p5')nA.