Reactivity of an anti-(human gastric carcinoma) monoclonal antibody with core-related peptides of gastrointestinal mucin

Summary A murine anti-(human gastric carcinoma) monoclonal antibody, GL-013 (IgG1), which reacts with a high-molecular-mass glycoprotein from colorectal tumour tissue [Yang and Price (1989) Anticancer Res 9: 1707], was examined for reactivity against a panel of purified and partially purified antigens associated with tumours of the gastrointestinal tract. These included carcinoembryonic antigen (CEA), normal cross-reacting antigen, Y-hapten glycoproteins, and perchloric acid extracts and glycolipid preparations from colorectal tumours. While the GL-013 antibody failed to bind to these antigens, it was found to react strongly with synthetic peptides with sequences based upon that reported for the protein core of a human gastrointestinal mucin [Barnd et al. (1989) Proc Natl Acad Sci USA 86: 7159; Gum et al. (1989) J Biol Chem 264: 6480]. In control tests, a series of other anti-(colorectal tumour) antibodies (IgG1 and IgG3), with broad reactivity towards gastrointestinal carcinomas, as well as an anti-CEA antibody, (IgG1) failed to react with the synthetic peptides. It is concluded that the anti-(gastric carcinoma) monoclonal antibody GL-013 binds to a threonine-rich peptide epitope expressed within the protein core of gastrointestinal mucins. Present address: Cancer Research Institute, China Medical University, Shenyang, Liaoning, People's Republic of China     

Differences between the catabolism and tumour distribution of intact monoclonal antibody (791T/36) and its Fab/c fragment in mice with tumour xenografts revealed by the use of a residualizing radiolabel (dilactitol-125I-tyramine) and autoradiography

Summary Radioiodine-labelled 791T/36 monoclonal antibody (mAb) and its Fab/c fragment, consisting of one Fab arm and the Fc portion, have identical whole-body survival curves in BALB/c mice (t1/2 = 3.75 days). Therefore, these two forms of this antibody provide a suitable model for studying the role of valency in the targeting efficiency of antibodies to tumours in vivo. 791/T36 antibody and its Fab/c fragment were labelled either by direct iodination using the iodogen method (¹²⁵I) or by dilactitol-¹²⁵I-tyramine (¹²⁵I-DLT), a residualizing label, which accumulates in the cells involved in degradation of the carrier protein. In tumour-bearing nude mice, the percentage of injected dose of mAb or Fab/c fragment reaching the specific 791T tumour was similar, and these proteins appeared to be catabolized at a similar rate in this tissue. mAb, but not the Fab/c fragment, was found to be very actively catabolized by the liver and spleen of tumour-bearing mice compared to control nude mice, this probably resulting from clearance of immune complexes. This effect was most pronounced when the mAb was labelled with¹²⁵I-DLT, the percentage of injected dose of mAb reaching the spleen and liver being higher than the percentage of injected dose reaching the tumour. This effect was not seen with the Fab/c fragment. Autoradiographic studies on tumour sections, which exhibit antigenic sites throughout the tumour mass, showed that the Fab/c fragment was already homogeneously distributed in the tumour 12 h after injection whereas the whole antibody was mainly localized at the periphery of the tumour. Those results suggest a binding site barrier effect. Overall, these results indicate that the highest valency and affinity may not be the optimal choice for mAb to be used for therapeutic purposes.     

Regression of human melanoma xenografts in nude mice injected with methotrexate linked to monoclonal antibody 225.28 to human high molecular weight-melanoma associated antigen

Summary Intravenous injections into nude mice of 5 mg/kg methotrexate (MTX) linked to the antibody to human high molecular weight-melanoma associated antigen (HMW-MAA), monoclonal antibody (mAb) 225.28, an IgG_2a, on days 1, 4, 7, 10 and 14, starting 24 h after subcutaneous inoculation of 2 × 10⁶ cultured human M21 melanoma cells inhibited mean tumor volume by 90% on day 14 and by 65% on day 50 after the beginning of the treatment. Injections of equimolar amounts of free MTX and MTX linked to normal mouse IgG or to an isotypematched myeloma protein did not inhibit tumor growth significantly. MTX linked to mAb 225.28 did not inhibit the xenograft of a subline of human melanoma cell line M21 without detectable expression of HMW-MAA. In a clonogenic assay, the MTX-225.28 conjugate was three times more potent in inhibiting the growth of M21 melanoma cells than free MTX, but did not inhibit the growth of kidney carcinoma cells Caki-1, which do not express high-M _r MAA. In contrast, MTX linked to the mAb DAL K29, reacting with kidney carcinoma cells Caki-1, inhibited their growth but did not affect that of melanoma cells. M21 melanoma cells isolated from the residual tumor of a mouse treated with the MTX-225.28 conjugate did not differ in their reactivity with mAb 225.28 and in their sensitivity to MTX when compared with M21 cells from an untreated mouse.     

Inhibition of cell proliferation with antibody-targeted liposomes containing methotrexate-γ-dimyristoylphosphatidylethanolamine

We have prepared liposomes containing methotrexate-γ-dimyristoylphosphatidylethanolamine (MTX-DMPE liposomes), to which protein A was covalently coupled, permitting specific association of these liposomes in vitro with murine cells preincubated with relevant protein A-binding monoclonal antibodies. In the absence of antibody the presence of externally-oriented methotrexate (MTX) in MTX-DMPE liposomes did not result in greater binding to cells than liposomes made without MTX-γ-DMPE. Derivation of methotrexate with phospholipid permits enhanced drug-liposome association. These liposomes are more resistant than conventional liposomes to repeated cycles of freezing and thawing. MTX-DMPE liposomes are comparable to antibody-targeted liposomes made with encapsulated water-soluble methotrexate both with respect to specific binding to target cells and drug effect. The inhibitory effects off MTX-liposomes, as well as free MTX, were reversible by either thiamin pyrophosphate (Tpp) or N⁵-formyltetrahydrofolate (F-THF), while the effects of MTX-DMPE liposomes were reversed only by N⁵-formyltetrahydrofolate. This suggests that the toxicity of non-targeted MTX-liposomes may be due to leakage of the encapsulated MTX. The absence of an effect of thiamin pyrophosphate on non-targeted MTX-DMPE liposomes indicates that they do not enter into the cell via the normal folate transport system.     

Virulence genes are carried by a megaplasmid of the plant pathogen Pseudomonas solanacearum

Summary A class of avirulent mutants of the plant pathogenic bacterium Pseudomonas solanacearum, strain GMI1000, resistant to acridine orange (Acr^r), harbour a deletion of over 85 kb in their genome. This deletion affects, a1,000 kb megaplasmid which has previously been shown to be present in most of the strains of this species. In addition at least 11 out of 13 independent Tn5 insertions, leading to loss of virulence, are located on the megaplasmid. Nine of them are present in the region which is deleted from the Acr^r mutants. These results suggest that the majority of virulence genes identified so far are plasmid borne.     

Survival ofPseudomonas syringae pv.lachrymans with cucumber roots

Summary Survival ofPseudomonas syringae pv.lachrymans with seedling cucumber roots, root washings, rhizosphere soil, and nonrhizosphere soil was determined 7–8 days after the soil surface was watered with a cell suspension of the bacterium. Plants were in pots in the green-house and soil was not sterilized. Survival was best with roots and root washings, next best in rhizosphere soil, and poor in nonrhizosphere soil.     

利用单克隆抗体鉴定人甲胎蛋白(HAFP)抗原结构可分性

本文利用两株针对HAFP分子不同抗原决定簇的单克隆抗体,鉴定HAFP酶解片断的抗原抗体反应性质,并同完整HAFP分子进行比较。结果表明,酶解片断上失去了一株单克隆抗体所对应的分子部份,完整保留着另一株单克隆抗体所识别的抗原决定簇,从而证实HAFP分子某些抗原结构之间具有可分割性。     

A rat oocyte differentiation antigen (OA-1) detected by a monoclonal antibody

Cell surface antigenic changes associated with differentiation of the rat oocyte and early embryo have been demonstrated with a monoclonal antibody (anti-OA-1). Antigen is first detectable coincident with initiation of oocyte growth, is a constant feature of all growing oocytes and displays a redistribution during meiotic maturation. Following fertilization, antigen is detectable on the surface of the embryo through the four-cell stage. This first monospecific marker for the rat oocyte and embryo should prove useful in probing structure/function relationships in oocyte growth, meiotic maturation fertilization, and/or early embryonic development.     

The effect of fifteen biocides on formaldehyde-resistant strains ofPseudomonas aeruginosa

Summary Evaluation of formaldehyde and fifteen biocides in formaldehyde sensitive (S) and resistant (R) strains ofPseudomonas aeruginosa revealed a pattern of response that allowed a comparison of the mode of action of these biocides. The response of these strains to the various biocides, as well as the induction of transient resistance or cross-resistance in the (S) strain, allowed a grouping of biocides based on this pattern of response. Group 1 biocides acted in a manner indistinguishable from formaldehyde for both the (S) and (R) strains. Group 2 biocides were not effective against either the (S) or (R) strains at concentrations calculated to release equimolar concentrations of formaldehyde. However, treatment of the (S) strain with formaldehyde or Group 2 biocides resulted in the development of cross-resistance. Group 3 biocides were equally effective against the (S) and (R) strain, but the (S) strain survivors of treatment with Group 3 biocides were resistant to formaldehyde. Group 4 biocides (controls) had no presumed connection to formaldehyde mode of action. These four groupings, based on pattern of response, also resulted in groupings of biocides based on chemical structure.