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Biomedical subjects

R Arnon

Publications and source records attributed to R Arnon.

At least 145 records · Page 8Linked to original sources
PubMed1988

Synthetic peptides of Shiga toxin B subunit induce antibodies which neutralize its biological activity.

Shiga toxin B chain, the binding subunit of Shiga toxin, was recently purified; and the amino acid sequence of this 7,716-dalton polypeptide was determined (N.G. Seidah, A. Donohue-Rolfe, C. Lazure, F. Auclair, G. T. Keusch, and M. Chretien, J. Biol. Chem. 261:13928-13931, 1986). In the present study, synthetic peptides corresponding to three overlapping sequences from the N-terminal region of this subunit were prepared. The peptides synthesized consisted of residues 5 to 18, 13 to 26, and 7 to 26. This region coincides with the major peak of hydrophilicity and surface area residues predicted from a computer analysis. For the purpose of immunization, the peptides either were conjugated with a protein or synthetic carrier or were polymerized with glutaraldehyde. Antisera against these peptide derivatives raised in rabbits reacted not only with the respective homologous peptide but also to a comparable extent with the intact Shiga toxin. The anti-peptide antisera effectively neutralized the various biological activities of the Shiga toxin, namely, cytotoxicity to HeLa cells, enterotoxic activity (the fluid secretion into ligated ileal loops in rats), and neurotoxicity in mice. Furthermore, active immunization with the peptide conjugates was found to protect mice against the lethal effect of Shiga toxin.

Amino Acid Sequence↗
PubMed1988

Atrioventricular block complicating acute streptococcal tonsillitis.

A 38 year old woman presented with severe weakness, high fever, and sore throat. Physical examination showed follicular tonsillitis and bradycardia caused by a atrioventricular block. Within 24 hours a normal sinus rhythm was regained but slight transient ST-T changes compatible with myocarditis were evident. Throat culture grew Streptococcus haemolyticus group A.

Acute Disease↗
PubMed1988

Amiodarone pulmonary toxicity presenting as a solitary lung mass.

Following treatment with amiodarone, a patient developed weight loss, fatigue and severe myopathy, without respiratory symptoms. A solitary lung infiltrate, impaired thyroid and liver function tests, and leukocytosis were evident. Biopsies from the lung lesion, liver, and bone marrow revealed foam cells. All these signs and symptoms subsided following cessation of amiodarone therapy. It is demonstrated that amiodarone may induce a localized lung lesion rather than diffuse pulmonary disease.

Aged↗
PubMed1987

Increased therapeutic efficacy of cis-platinum complexes of poly-L-glutamic acid against a murine carcinoma.

Cis-diamminedichloroplatinum(II) (cis-DDP) and cis diamminediaquoplatinum(II) nitrate (cis-aq) were complexed to poly-L-glutamic acid (PG) of Mr 13,000 or 58,000. Soluble complexes were formed by mixing the platinum(II) compounds with the PG preparations in water at a molar ratio of one platinum(II) to 5 glutamyl residues of the PG. Compared to free cis-DDP, the complexes were about 2 to 6 times less cytotoxic to F9 embryonal carcinoma cells in vitro. In vivo studies with this tumor indicated that when administered i.p. one day after the tumor cells, the complexes were somewhat less active than cis-DDP. However, in comparison to the free drug which, due to its toxicity, was effective only within a very narrow dose range, the complexes were much less toxic, manifesting a wide therapeutic range in which no mortality occurred either from the tumor or as a result of the toxic effects of the drug. Cis-DDP and cis-aq complexes of PG Mr-58,000 were somewhat more toxic than the complexes of PG Mr, 13,000. The in vivo anti-tumor activity of most complexes was superior to that of free cis-DDP when tested in mice carrying high tumor loads. Due to their wide therapeutic range, the complexes could be given at high drug doses resulting in increased life span of the tumor-bearing mice. Moreover, 3 repeated injections of these high doses did not cause death from toxicity and resulted in partial or total eradication of advanced tumors.

Animals↗
PubMed1987

Role of cellular and humoral immunity and helper cell involvement in permissiveness to infection by Schistosoma mansoni.

Cellular and humoral parameters were studied in permissive (mouse) and nonpermissive (rat) animals during the first few weeks following infection by Schistosoma mansoni. Comparison was made between the antigen-induced proliferation of lymphocytes of the two species. Extract of cercaria, schistosomula and adult worms obtained from infected mice served as the test antigen in 3 and 6 days incubation in vitro thymidine uptake assay. Both spleen and thymus cells of mice and rats differed in their reactivity with the schistosome antigens, but the difference was much more pronounced in the thymocytes. In this case, whereas cells obtained form mice were not induced to proliferate by any of the antigens, thymocytes of the infected rat showed specific increasing proliferation rates as a function of time after infection. In the rat, a subset of T cell population, the T helper cell, appears to be involved in the immune response, as established by the use of anti-helper monoclonal antibody W3/25. In the presence of these antibodies the immune reactivity of the rat thymocytes with antigens from different stages of the parasite was markedly reduced. The effect of W3/25 antibodies was observed not only in vitro, in the lymphocyte proliferation assay, but also in vivo, by a significant increase in the extent of infection in the W3/25-treated rats, as compared to untreated controls. Differences between the two hosts were also observed in their humoral immune response against the schistosome antigens, as manifested by complement-dependent cytotoxicity. In these assays mouse sera were more effective than rat sera. When autologous complement was evaluated, mouse complement had a higher cytotoxic effect than rat complement in killing of the parasite. Both sources of complement were less effective than guinea pig complement in causing antibody-mediated cytotoxicity.

Animals↗
PubMed1987

Selective cytotoxicity against tumor cells by cisplatin complexed to antitumor antibodies via carboxymethyl dextran.

Cis-diamminedichloroplatinum (II) (cis-DDP) and its structural analogue cis-diamminediaquoplatinum(II) nitrate (cis-aq) were complexed via an intermediate dextran carrier to antibodies specifically reactive with B lymphoma cells (38C-13). The potential use of these drugs in site-directed immunotargeting was evaluated. The two platinum(II) compounds were previously shown to form pharmacologically active complexes with carboxymethyl dextran (CM-dex). For the purpose of preparing drug-antibody complexes, CM-dex was first conjugated to idiotypic antibodies that recognize a specific membrane IgM on the B lymphoma cells. The conjugates were prepared by a modified water-soluble carbodiimide method in which N-hydroxysuccinimide was used to enhance the coupling reaction. The conjugation was followed by separation of the CM-dex-IgG conjugates from unconjugated CM-dex or IgG. The platinum(II) compounds were then complexed to the CM-dex-IgG resulting in complexes carrying up to 50 mole drug/mole IgG. Both cis-DDP and cis-aq complexes of CM-dex-antibody conjugates maintained most of the original cell-binding activity of the antibodies. An in vitro assay was used to demonstrate selective binding to tumor cells in which the target cells were treated with specific immune complexes and washed before culture. In this assay the specific complexes showed preferential cytotoxicity for the B lymphoma cells in comparison to the free drugs, drug CM-dex, or nonspecific immune complexes.

Animals↗
PubMed1986

Anti-cholera response elicited by a completely synthetic antigen with built-in adjuvanticity administered in aqueous solution.

Some synthetic peptides derived from the B subunit of cholera toxin, conjugated to tetanus toxoid have been shown by us to be efficient when administered in complete Freund's adjuvant (CFA), in induction of anticholera toxin response with neutralizing capacity. When the peptide CTP3, corresponding to residues 50-64 within the sequence of the B subunit, was attached to the hardly immunogenic A-L (multichain poly-DL-alanine) the resulting conjugate did not lead to a significant anti-peptide response even when given in CFA. On the other hand, when CTP3 was coupled to the immunogenic (T,G)-A-L, the resulting CTP3-(T,G)-A-L led, in CFA, to protective anti-cholera antibodies. Moreover, covalent attachment of the synthetic adjuvant N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) to the latter immunogen led to MDP-CTP3-(T,G)-A-L which, when administered in aqueous solution, elicited in rabbits antibodies with neutralizing capacity.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1986

Ion fluxes changes during early stages of Schistosoma mansoni. Evaluation of complement effect.

The relationship between the average membrane potential (delta psi av) and sensitivity to complement action of the Schistosoma mansoni parasite was explored. The average membrane potential was estimated by measuring the uptake of [3H]tetraphenyl phosphonium ([3H]Ph4P+). The parasites take up Ph4P+ indicating the existence of a negative internal plasma potential which is in part dependent on the transmembrane K+ gradient, maintained by an active Na+/K+-ATPase. Values for Ph4P+ uptake could be corrected for mitochondrial accumulation by employing the protonophore carbonylcyanide m-chlorophenylhydrazone (CCCP), which collapses the mitochondrial potential. The plasma membrane potential derived by this technique was in the range of -60 mV. Transformation of this parasite, from its early cercaria stage to the adult worm, was associated with changes in the average membrane potential. The apparent hyperpolarization, which accompanies transformation, may be related to changes in ionic permeability and morphology which occur concomitantly. Complement acting through both the classical and alternative pathways was found to affect the potential of the parasite in its early development stages. The correlation between effects on delta psi av and sensitivity to complement action, indicates that the complement-induced changes in delta psi av are indeed tightly associated with its mode of action. Treatment of the parasite with complement resulted in net hyperpolarization of the membrane indicating that hyperpolarization rather than depolarization of the membrane is linked to the primary non-lethal action of complement.

Animals↗
PubMed1986

Synthetic peptides with antigenic specificity for bacterial toxins.

The attachment of a diphtheria toxin-specific synthetic antigenic determinant and a synthetic adjuvant to a synthetic polymeric carrier led to production of a totally synthetic macromolecule which provoked protective antibodies against diphtheria when administered in aqueous solution. When peptides related to the B subunit of cholera toxin were synthesized and attached to tetanus toxoid, antibodies produced against the conjugate reacted in some but not all cases with intact cholera toxin and (especially with peptide CTP 3, residues 50-64) neutralized toxin reactivity, as tested by permeability in rabbit skin, fluid accumulation in ligated small intestinal loops and adenylate cyclase activation. Polymerization of the peptide without any external carrier, or conjugation with the dipalmityl lysine group, had as good an effect in enhancing the immune response as its attachment to tetanus toxoid. Prior exposure to the carrier suppressed the immune response to the epitope attached to it, whereas prior exposure to the synthetic peptide had a good priming effect when the intact toxin was given; when two different peptides were attached to the same carrier, both were expressed. Antisera against peptide CTP 3 were highly cross-reactive with the heat-labile toxin of Escherichia coli and neutralized it to the same extent as cholera toxin, which is not surprising in view of the great homology between the two proteins. A synthetic oligonucleotide coding for CTP 3 has been used to express the peptide in a form suitable for immunization. It led to a priming effect against the intact cholera toxin.

Adjuvants, Immunologic↗
PubMed1986

Priming immune response to cholera toxin induced by synthetic peptides.

A systematic study has been conducted of the priming effect in the immunization against cholera toxin (CT). We demonstrate that a priming phenomenon can be achieved by synthetic peptides of the CT B subunit, leading (after a subsequent booster with a subimmunizing dose of the intact toxin) to an efficient anti-CT neutralizing antibody response. This effect is obtained even upon a single administration of a peptide conjugate and even by peptides that as such are not able to induce CT cross-reactive antibodies whatsoever. This effect is specific and dose dependent. A macromolecular carrier as well as an adjuvant are essential for the induction of anti-toxin response. In this respect, a totally synthetic priming agent, CTP3-poly(DL-alanyl)--poly(L-lysine), was adequate for an effective priming response. The specificity of the antibodies formed after the booster was mainly towards the whole CT molecule and only a small fraction of them were specific towards the peptide used for priming. The ability of synthetic peptides to prime the immune system towards a secondary stimulus with whole organism or native protein might be of general practical value, especially in endemic areas where the population is probably constantly exposed to a low level of a particular infectious agent. This exposure, which has no influence on the unprimed immune system, could serve as a booster in the case of individuals primed with an appropriate peptide, leading to a secondary immune response.

Adjuvants, Immunologic↗
PubMed1986

Acetylcholinesterase of Schistosoma mansoni: purification and characterization.

Larval acetylcholinesterase (acetylcholine acetylhydrolase) EC 3.1.3.7 of the trematode Schistosoma mansoni was characterized and purified by affinity chromatography. The enzyme was solubilized from sonicated cercarial tissue and showed a Km value of 1.83 mM and a Vmax value of 102 U/mg protein. It was characterized as a true AChE since it hydrolyses acetylthiocholine more than seven times faster than butyrylthiocholine, and since it was inhibited by high concentrations of substrate. The enzyme was purified by affinity chromatography on a Sepharose column of the inhibitor [N-(6-aminocaproyl-6-aminocaproyl)-m-aminophenyl] trimethyl ammonium. The purified enzyme eluted from the column by decamethonium bromide migrated as a single band of 500 kD on nondenaturing polyacrylamide gel electrophoresis (PAGE), whether stained for proteins or for enzymatic activity. Analysis by SDS-PAGE revealed two major polypeptide bands of 76 kD and 30 kD. By labeling the enzyme with 3H-DFP (di-isopropyl-fluorophosphate), the 30-kD polypeptide was shown to contain the active site of the enzyme, with an additional labeled band of 110 kD also being detected. On the basis of our data we suggest that the principal species of S. mansoni AChE is a tetramer of four subunit polypeptides each of MW ca. 110 kD which are not linked by disulfide bonds, and which are further cleaved into two fragments, one of MW 76,000 and one of MW 30,000, the latter bears the active site.

Acetylcholinesterase↗
PubMed1986

Schistosoma mansoni: killing of transformed schistosomula by the alternative pathway of human complement.

The interaction of mechanically transformed schistosomula of Schistosoma mansoni with the alternative pathway of human complement was studied in vitro. To detect early changes in transformation, the schistosomula were prepared at a low temperature and used immediately. As shown previously, freshly transformed schistosomula were highly susceptible to killing by normal human serum and by C4-depleted normal human serum. This serum activity was concentration dependent and was markedly reduced on a twofold serum dilution. Upon incubation at 37 C in defined synthetic medium, schistosomula rapidly became refractory to killing by the alternative pathway of complement. After 1 hr of incubation at 37 C, the percentage of schistosomula which were resistant to killing increased from 16 to 85. This conversion was accompanied by a fivefold decrease in deposition of C3b on schistosomula which had been exposed to 37 C for 1 hr and then further incubated with C4-depleted normal human serum. The following events occurred concomitantly during incubation of freshly transformed schistosomula at 37 C with a half-life of 30-60 min: (1) Decrease in activation and consumption of the alternative pathway of complement by schistosomula; (2) appearance of a strong complement consuming activity in the supernatant of incubating schistosomula; and (3) shedding of protein- and carbohydrate-containing substances from the surface of schistosomula into the supernatant. Isolated external membranes of freshly transformed schistosomula consumed the alternative pathway of complement to a greater extent than membranes of schistosomula preincubated in medium at 37 C. The results demonstrate that transformed schistosomula acquire resistance to complement killing via the alternative pathway by shedding complement-activating substances.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Antibodies to cholera toxin synthetic peptides of increasing size and their reactivity with related toxins.

The role of the size of synthetic peptides in their immunological cross-reactivity with the parent native protein, was investigated using the cholera toxin system. The results show that elongation of a peptide may affect the reactivity of the antibodies it elicits in either positive or negative directions. Thus, elongation by six amino acid residues of each of two peptides of cholera toxin that were incapable of inducing cross-reactive antibodies with the parent protein (CTP2a and CTP5) converted them into peptides with cross-reacting capacity (CTP2b and CTP4, respectively). On the other hand, a similar elongation of another peptide (CTP3) which as such leads to cross-reactive antibodies resulted in a peptide (CTP3a) which was less cross-reactive with a series of proteins related immunologically to the parent protein.

Amino Acid Sequence↗
PubMed1986

Monoclonal and polyclonal antibodies against acetaldehyde-containing epitopes in acetaldehyde-protein adducts.

Immunization of mice with acetaldehyde conjugated to human plasma proteins resulted in the production of polyclonal antibodies that reacted with erythrocyte protein-acetaldehyde conjugates, but not with control erythrocyte proteins. Such antibodies recognized erythrocyte protein-acetaldehyde conjugates prepared with 20-100 microM acetaldehyde, concentrations that exist in the blood of alcoholics. The antibodies also recognized acetaldehyde condensation products with synthetic poly-(L-lysine). Immunization with keyhole limpet hemocyanin-acetaldehyde conjugates resulted in antibodies against both plasma protein-acetaldehyde and erythrocyte protein-acetaldehyde conjugates, which did not cross-react with the respective unmodified carrier proteins. Immunization with human erythrocyte protein-acetaldehyde condensates led to the production of antibodies against both the protein moiety as well as the condensate. Monoclonal antibodies with affinities 50 times greater for the condensate than for the carrier protein were produced by hybridization of spleen cells from the immunized mice. Chronic alcohol administration to mice for 45-50 days led to the generation of antibodies that reacted against protein-acetaldehyde conjugates, suggesting that such adducts are formed in vivo and can act as neoantigens. Antibodies against acetaldehyde adducts should be of value in the identification of alcohol consumption and in the study of the biology of the adducts in relation to organ pathology.

Acetaldehyde↗
PubMed1986

Immunity to heat-labile enterotoxins of porcine and human Escherichia coli strains achieved with synthetic cholera toxin peptides.

Antiserum to a synthetic peptide, CTP3, consisting of residues 50 to 64 of the B subunit of cholera enterotoxin (CT), a sequence which is conserved in heat-labile enterotoxins from Escherichia coli strains of human (H-LT) or porcine (P-LT) origin, cross-reacted with and neutralized all three enterotoxins. It also cross-reacted with genetically engineered chimeric B subunit proteins in which H-LT amino acids had been substituted for the corresponding residues in P-LT. Antisera against another CT peptide, CTP1, consisting of residues 8 to 20, were weakly cross-reactive with H-LT but not with P-LT, whereas antisera against four other CT peptides were not cross-reactive with the heterologous enterotoxins. A single dose of CTP3-linked tetanus toxoid, by itself nonimmunogenic, primed rabbits to a vigorous immune response to subsequent administration of single, small, subimmunizing doses of any of the three enterotoxins.

Animals↗