PubMed Health⌕ Search

Biomedical subjects

J A Forrester

Publications and source records attributed to J A Forrester.

At least 19 recordsLinked to original sources
PubMed1990

Pharmacokinetics in the rat of a panel of immunotoxins made with abrin A chain, ricin A chain, gelonin, and momordin.

A panel of immunotoxins was constructed by chemically attaching the ribosome-inactivating proteins abrin A chain, ricin A chain, gelonin, and momordin to the monoclonal mouse IgG2a antibody Fib75 by means of a disulfide linkage. All the immunotoxins were toxic in tissue culture to the EJ human bladder carcinoma cell line expressing the antigen recognized by Fib75, inhibiting the incorporation of [3H]leucine by 50% at concentrations between 1 x 10(-10) M and 8 x 10(-10) M. The pharmacokinetics of the immunotoxins in the normal Wistar rat was determined following i.v. administration. The concentrations of intact immunotoxin in serum samples taken at various intervals after injection for up to 24 h were measured by solid-phase enzyme-linked immunosorbent assays specific for each of the four different ribosome-inactivating proteins. The Fib75 immunotoxins were cleared from the circulation with comparable, but not identical, biphasic kinetics best described by a two compartment open pharmacokinetic model. The alpha-phase half-lives of the panel, between 0.35 and 0.71 h, were similar. The beta-phase half-life of Fib75-abrin A chain, 13.3 h, was significantly longer than the beta-phase half-lives of Fib75-ricin A chain, Fib75-gelonin, and Fib75-momordin, between 7.5 and 8.6 h. Fib75-abrin A chain was found to be about 3- to 4-fold more resistant than the other immunotoxins to breakdown by reduction of the disulfide linkage between the A chain and the antibody with glutathione in vitro. This suggests that the longer serum half-life of Fib75-abrin A chain may have been due to greater stability against reduction in vivo. Analysis of serum samples obtained up to 24 h after injection of Fib75-abrin A chain revealed that the chemically intact immunotoxin present in the circulation retained full cytotoxic activity. An abrin A chain immunotoxin made with a different monoclonal mouse IgG2a antibody was also found to be more stable against reduction by glutathione in vitro than an analogous ricin A chain immunotoxin. Thus, abrin A chain may posses unique molecular properties that endow immunotoxins made with this A chain with greater stability in vivo than immunotoxins made with ricin A chain or other ribosome-inactivating proteins.

Abrin↗
PubMed1987

An ineffective monoclonal antibody-ricin A chain conjugate is converted to a tumouricidal agent in vivo by subsequent systemic administration of ricin B chain.

An immunotoxin comprising a tumour-specific monoclonal antibody (11/160) coupled to ricin A chain, although inactive in in vitro cytotoxicity assays against HSNtc sarcoma target cells, was found to be capable of significant tumouricidal activity in syngeneic rats if potentiated by ricin B chain. The 11/160-ricin A, when bound to tumour cells prior to their inoculation, led to a slight inhibition of tumour growth s.c. compared with untreated sarcoma cells or those coated with antibody alone. However, all tumours in these groups developed progressively (69/69), whereas in those rats receiving 15 micrograms or 150 micrograms ricin B chain i.v. 5 min after tumour cell inoculation, the 'take rate' was reduced to 75% and 30% respectively, and significantly longer latent periods were evident for those tumours which did develop. Ricin B chain similarly inhibited, in a dose-dependent manner, the lung colonisation potential of 11/160-ricin A coated HSNtc cells. No effects were obtained if the B chain treatment followed inoculation of untreated or antibody-coated cells, suggesting that systemically administered B chain is capable of gaining access to and activating antibody-ricin A chain conjugates bound to the surface of syngeneic sarcoma cells in lung or subcutaneous sites. Tumour inhibition was obtained in some instances with intervals of up to 24 h between inoculation of conjugate-coated tumour cells and B chain. Experiments are in progress to determine if such potentiation may be feasible in a therapeutic rather than a prophylactic setting using this syngeneic solid tumour system.

Animals↗
PubMed1987

Tissue staining properties of lectins from the seeds of the jack fruit (Artocarpus integrifolia) and the winged bean (Psophocarpus tetragonolobus).

N-acetyl-D-galactosamine binding lectins from winged bean (Psophocarpus tetragonolobus) and jack fruit (Artocarpus integrifolia) were isolated, purified and conjugated with horse radish peroxidase and their tissue staining properties studied. Despite having an apparently common inhibiting sugar, the lectins showed differences in their staining properties. The lectin from the winged bean stained none of the mouse and human tissues tried even after neuraminidase treatment whereas the jack fruit lectin stained most of the untreated cells. The staining was found to be improved by the prior treatment of the cells with neuraminidase and inhibited completely by the inhibiting sugar. The differences in the staining properties of the lectins are discussed.

Animals↗
PubMed1986

Fate of an antibody-ricin A chain conjugate administered to normal rats.

The pharmacokinetics and catabolism of ricin A chain, a mouse monoclonal antibody (LICR-LOND-Fib 75) and a disulphide linked conjugate of the two have been studied following their intravenous administration to normal rats. Results indicate that the conjugate was removed from the circulation much more rapidly than the antibody but less quickly than the free ricin A chain. Disappearance of the conjugate from the circulation appeared to be biphasic with an early rapid initial phase followed by a much more rapidly than the antibody but less quickly than the free ricin A chain. Disappearance of the conjugate from the circulation appeared to be biphasic with an early rapid initial phase followed by a much slower phase. The fate of a conjugate with a 125I iodide label in the antibody component was compared with that of a conjugate similarly labelled but in the ricin A chain component. The results indicate that breakdown of the conjugate involves both cleavage of the disulphide linkage and complete catabolism of the whole conjugate molecule with the release of 125I iodide. Rapid cleavage of the disulphide bond in the vasculature does not appear to be responsible for the initial rapid disappearance of the conjugate from the circulation.

Animals↗
PubMed1986

Studies on the reappearance of MHC class II antigens on cells of a variant human lymphoblastoid line.

EB4 lymphoblastoid cell line cells were cultured for 32 days with a ricin A chain-conjugated monoclonal antibody (McAb) to a beta chain determinant present on DP and DR antigens. A single colony of cells which survived this treatment was grown up and surface expression of MHC class II and B cell antigens measured. All class II antigens (DQ as well as DP and DR, alpha as well as beta chains) were initially greatly diminished, but substantial recovery of expression occurred within 20-100 days of culture (approx. 21-105 generations), although recovery was still incomplete. The CD19 (p95) B cell antigen was present in greater amount and the CD22 B cell antigen and surface immunoglobulin in lower amount on the variant line cells. It was confirmed that unconjugated anti-class II McAb binds to surface antigens but is unable to induce modulation even over an 8-day culture period. Evidence is presented that the gradual re-expression of class II antigens on the variant line cells is not due to the appearance of a mutant or to recovery from modulation. It is suggested that the variant line cells produce an excess of a regulatory molecule when grown in the conjugate.

Antibodies, Monoclonal↗
PubMed1986

Effect of linkage variation on pharmacokinetics of ricin A chain-antibody conjugates in normal rats.

We have investigated the pharmacokinetics of three ricin A chain-antibody conjugates having different bridging structures. Conjugate 1 has a disulphide linkage and was prepared with the N-succinimidyl-3-(2-pyridyldithio)propionate cross-linking reagent. Conjugate 2 has a protected disulphide linkage with a methyl group substituted on the carbon atom of the bridging structure adjacent to the disulphide linkage. Its preparation necessitated the synthesis of a new cross-linking reagent N-succinimidyl 3-(2-pyridyldithio)-butyrate. Conjugate 3 has a sulphide linkage and was prepared with the cross-linking reagent N-succinimidyl 4-(iodoacetylamino)benzoate which was synthesized by a novel route. Conjugate 1 is reducible, conjugate 2 less easily reducible and conjugate 3 nonreducible. On administration to animals all three conjugates displayed biphasic kinetics. The reducibility of the bond had no significant effect on the early disappearance of the conjugate from the circulation. However, at the later time points ease of reduction of the bond was associated with a more rapid disappearance of conjugate.

Animals↗
PubMed1986

In vitro and in vivo effects of a monoclonal antibody-toxin conjugate for use in autologous bone marrow transplantation for patients with breast cancer.

We have devised a method utilizing a monoclonal antibody-toxin conjugate (LICR-LON-Fib75/abrin A-chain) for ridding bone marrow of infiltrating breast cancer cells to rescue patients with autologous bone marrow following high dose therapy. Initially we examined the activity of this conjugate in vitro. Five of seven human breast cancer cell lines were killed following exposure at 10(-8) M for 2 h; this concentration only reduced bone marrow colony formation to 83% (range, 50-100%) of control bone marrow. We then examined the pattern of bone marrow recovery after high dose melphalan (200 mg/m2) in patients with advanced breast cancer who were in remission following combination chemotherapy. To do this we compared the time of recovery of the blood count in three patients who received treated marrow and seven who received untreated marrow. Mean time to recovery of the peripheral white count (greater than 1.5 X 10(9)/liter) was 16.7 days (treated) and 18.3 days (untreated), respectively. Mean time to recovery of peripheral platelet count (greater than 50 X 10(9)/liter) was 23.7 days (treated) and 18.9 days (untreated), respectively. Patients continued in remission for 1-greater than 14 mo after high dose melphalan, and remission duration was similar in patients who received treated (6.2 mo) and untreated (7.3 mo) bone marrow. These findings indicate that treatment of bone marrow with LICR-LON-Fib75/abrin A-chain conjugate does not significantly impair bone marrow recovery, and it is, therefore, possible to rescue breast cancer patients with bone marrow that has been cleansed of infiltrating cancer cells. This may have an application in patients with poor-risk primary breast cancer who have micrometastases and who may benefit from intensive therapy, but it has minimal application in patients with more advanced disease.

Abrin↗
PubMed1985

Modification of the carbohydrate in ricin with metaperiodate-cyanoborohydride mixtures. Effects on toxicity and in vivo distribution.

Attempts to target antibody-ricin conjugates (immunotoxins) to designated cell types in vivo may be thwarted by their rapid clearance by hepatic reticuloendothelial cells which have receptors that recognise oligosaccharide side chains on the toxin. The B-chain of ricin contains high mannose type oligosaccharides and the A-chain contains a complex unit (GlcNAc)2-Fuc-Xyl-(Man)4-6, all of which potentially could be recognised by the reticuloendothelial system. Treatment of ricin with a mixture of sodium metaperiodate and sodium cyanoborohydride at pH 3.5 resulted in oxidative cleavage of the carbohydrates and reduction of the aldehyde groups thus formed to primary alcohols. By conducting the modification procedure at acidic pH, both the possibility of Schiff's base formation between the aldehyde groups and amino groups in the protein and the possibility of non-specific oxidation of amino acids were minimised. The extent of the carbohydrate modification depended on the duration of treatment, resulting maximally in the destruction of 13 of the 18 mannose residues and of all xylose and fucose. The toxicity of the modified toxin to cells in culture declined by up to 90% as the carbohydrate was destroyed. This was not due to a reduced ability of the B-chain to bind to cells or of the A-chain to inactivate ribosomes. In contrast to the in vitro results, the toxicity of the modified toxin to mice and rats was elevated by up to fourfold. The modification greatly reduced the clearance of the toxin by non-parenchymal cells in the liver and prevented the damage to hepatic Kupffer and sinusoidal cells and to the red pulp of the spleen that is inflicted by the native toxin. The elevated toxicity to animals appears to be because the modified toxin evades the reticuloendothelial system and persists in the bloodstream for longer periods, thus resulting in lethal damage to vital tissues in the animal at lower dosage. The results suggest that immunotoxins prepared from modified ricin would not be readily cleared by the reticuloendothelial system and so be more effective at killing their target cells.

Amino Acids↗
PubMed1985

Variants of lymphoid lines produced with ricin A-chain monoclonal antibody conjugates.

Conjugates of ricin A-chain with monoclonal anti-light chain antibodies specifically killed cells hearing kappa or lambda immunoglobulin (Ig) light chains. Exposure of cells from B-lymphoblastoid cell lines (B-LCL) to conjugate for less than 30 h had only a slight effect on cell growth, but on 48 h exposure a marked killing effect was achieved. After recovery of growth, cells were re-exposed to conjugate for 9-14 days. Treatment of cells from the EB4 line (sIgG lambda) in this way yielded 4 variants which showed a marked reduction in levels of surface Ig lambda and secreted Ig lambda with slight, or no, reduction in MHC class II expression and similar growth rates to the parent line. Variant lines retained their phenotype over long periods of culture.

Antibodies, Monoclonal↗
PubMed1985

The carriage and delivery of substances to lymphatic tissues by recirculating lymphocytes. I. The concentration of ricin in lymphocyte traffic areas.

Thoracic duct lymphocytes (TDL) were loaded in vitro with ricin before intravenous injection into syngeneic rats. TDL that had been incubated at 10 micrograms of ricin/5 X 10(7) cells/ml migrated from the blood into the spleen and lymph nodes (LN) according to the physiological pattern, and TDL incubated at 10 times that concentration were only slightly impaired in their ability to enter LN. The transfer of cells to recipients with thoracic duct fistulae indicated that very few ricin-treated lymphocytes left the LN to recirculate back to lymph. Most of the ricin-loaded lymphocytes died within the lymphatic tissues, probably between 7 and 15 hr after injection. The ricin toxicity was transferred locally, causing selective damage to the cell population within the traffic areas of the lymphatic tissues without disrupting the tissue architecture. This pattern of intensive cell destruction was not seen after a lethal dose of free ricin, which caused more diffuse and less severe damage to the spleen and LN, proving that lymphocytes are effective carriers of ricin. The surviving host lymphocytes were distributed abnormally, presumably because of the obvious damage to small blood vessels in LN and elsewhere. Lymphocytes accumulated especially in the red pulp of the spleen. Although the method described has drawbacks, it might be developed in order to concentrate ricin in the vicinity of neoplastic cells in diffuse lymphomas and leukaemias.

Animals↗
PubMed1984

Flow cytometric analysis of the binding of eleven lectins to human T- and B-cells and to human T- and B-cell lines.

The relative surface binding of 11 lectins to human peripheral blood T- and B-lymphocytes, to Molt-4 and JM T-cell lines, and to 6410 and NC37 B-cell lines was determined by flow cytometry. The lectins from Lens culinaris (LCA), Ricinus communis (RCA), Arachis hypogaea (PNA), Abrus precatorius (APA), Ulex europaeus (UEA-F), Sarothamnus scoparius (SAS-F), Helix pomatia (HPA), Phaseolus coccineus (L-PHA), Glycine max (SBA), and Triticum vulgare (WGA) were fluoresceinated and incubated with living, formaldehyde-fixed, or neuraminidase-treated cells. Except LCA, which preferentially bound to the two B-cell lines tested in this study, none of the other lectins exhibited selective binding to the undifferentiated cells of the cell lines. The T-cell lines and, in part, the peripheral blood T-cells bound less WGA, APA, LCA, and L-PHA than the B-cell lines and the peripheral blood B-cells. Binding of PNA was found only after neuraminidase treatment of the cells; the binding of PNA, HPA, and UEA-F after neuraminidase treatment was higher for the T-cells than the B-cells from peripheral blood. No significant differences were detected between both cell types for RCA, ConA, SBA, and SAS-F.

B-Lymphocytes↗
PubMed1984

Delivery of ricin and abrin A-chains to human carcinoma cells in culture following covalent linkage to monoclonal antibody LICR-LOND-Fib 75.

With the object of generating specific cytotoxic agents, we have prepared covalent conjugates of the A-chains of ricin and of abrin with monoclonal antibody LICR-LOND-Fib 75 and investigated their toxicity toward a human tumor cell line in culture. Both conjugates proved to be potent cytotoxins toward cells carrying the appropriate antigen. The agent containing abrin A-chain was toxic at a significantly lower concentration and exerted its maximum effect more rapidly than the one containing ricin A-chain. Inclusion of chloroquine in the incubation medium significantly enhanced the toxic action of both conjugates without loss of immunospecificity. Because of the widespread occurrence on human tumor cell lines of the antigen recognized by Fib 75, these conjugates, particularly the one containing abrin A-chain, may find application in freeing human bone marrow ex vivo of infiltrated tumor cells prior to reinfusion as an autograft.

Abrin↗
PubMed1983

Ricin B chain converts a non-cytotoxic antibody-ricin A chain conjugate into a potent and specific cytotoxic agent.

We report the conversion of a non-cytotoxic antibody-ricin A chain conjugate to one displaying specific cytotoxic effects comparable with that of native ricin, by the addition of ricin B chain as a second stage reagent. The results suggest that this conversion is achieved by the association of the added B chain with the A chain of the conjugate, and not through a primary binding of B chain at the cell surface.

Animals↗
PubMed1983

The analysis of the red cell unsaturated fatty acid test for multiple sclerosis using laser cytopherometry.

Using a laser cytopherometer, the electrophoretic mobility of glutaraldehyde-fixed erythrocytes from patients with multiple sclerosis (MS) has been compared with that of cells from control subjects. The effect of incubating cells with different concentrations of linoleic acid (LA) has been tested. At a concentration of 20 micrograms LA per 2 x 10(7) cells, slower mobilities were observed, on average, than those of control subjects, but there was overlap between control and patient groups. At a higher concentration of LA (160 micrograms per 2 x 10(7) cells), many of the MS samples showed a slower mobility than the control samples, although overlap was still evident. The value of the application of laser cytopherometry compared with conventional cytopherometry to this type of test is discussed.

Adult↗
PubMed1983

Asthma in merchant seamen and laboratory workers caused by allergy to castor beans: analysis of allergens.

Three merchant seamen and two laboratory workers who developed allergic symptoms following exposure to castor beans have been investigated. Bronchial-provocation testing with castor beans in the merchant seamen demonstrated a late reaction in two. Specific IgE against whole castor-bean extract and ricin, ricinus agglutinin and dericinated extracts of castor bean were found in the patients' sera using radioallergosorbent tests (RAST). RAST inhibition, toxocological and haemagglutination tests suggest that the ricin and dericinated extracts contain distinct allergens.

Adult↗