Toshihiro Nakanishi

Metastatic potential of human colorectal carcinoma SW1222 cells transfected with cDNA encoding carcinoembryonic antigen

In order to examine a role of carcinoembryonic antigen (CEA) in metastasis, cDNA encoding CEA was introduced into a clone of human colorectal carcinoma SW1222 cells. Western blot analysis revealed that all transfectants express CEA of 180 kDa while the parent clone does not. In the transfectants, the level of CEA expression in clone 3 was higher than that of clone 1. Clone 3 formed aggregates rapidly after suspended by trypsinization while clone 1 did not. In experimental metastasis assay where tumor cells were injected intrasplenically, clone 3 exhibited a higher liver-metastatic activity than clone 1. Fab fragment of anti-CEA antibody significantly inhibited both the cell aggregation and the liver metastases caused by clone 3. These findings suggested that CEA expressed on the cell surface may play an important role in hepatic metastasis from colorectal carcinoma, possibly through its cell adhesion activity.

Effect of human plasma-type platelet-activating factor acetylhydrolase in two anaphylactic shock models.

The effect of human recombinant plasma-type platelet-activating factor (PAF) acetylhydrolase was examined in two murine models, PAF-induced death and active anaphylactic models. In the PAF-induced death model where mice were injected intravenously with 40 microg/kg of PAF, the administration of PAF acetylhydrolase reduced mortality in a dose-dependent manner, showing complete prevention of mortality at 1.0 mg/kg. Myeloperoxidase activity, the marker for neutrophils, was increased in the lung by PAF injection, and the PAF acetylhydrolase treatment significantly reversed the increase in myeloperoxidase activity. As in the PAF-induced model, PAF acetylhydrolase also decreased mortality in the active anaphylactic shock model where bovine serum albumin was injected intravenously to mice previously immunized with bovine serum albumin. The protective effect of PAF acetylhydrolase on mortality in this model was significant at 1.0 mg/kg. These results suggest that PAF is an important mediator in the lethality of systemic anaphylaxis, and that PAF acetylhydrolase may be beneficial for treatment of anaphylactic shock.

Humanization of a mouse neutralizing monoclonal antibody against tumor necrosis factor-α (TNF-α)

An anti-human tumor necrosis factor-α (TNF-α) monoclonal antibody, designated as 3B10, inhibits the biological activity of human TNF-α. In the present study, we constructed humanized version of the antibody by grafting its complementarity-determining regions (CDRs) onto a human antibody, HBS-1. Using a molecular model of mouse 3B10, framework residues affecting the CDR conformation were identified. Thus, these residues were also introduced into the framework together with the CDRs in a stepwise manner, depending on the degree of the possible importance of the residues. As a result, one humanized version (h3B10-9) which possesses nine mouse framework residues showed the same binding activity as that of the chimeric version. This humanized anti-TNF-α antibody is expected to be less immunogenic and thus more suitable for possible clinical use.

Fucoidin, a potent inhibitor of l-selectin function, reduces contact hypersensitivity reaction in mice

In order to investigate the role of L-selectin (CD62L) in delayed-type hypersensitivity (DTH) reaction, effect of fucoidin, a potent inhibitor of CD62L function, was examined in a model of mouse contact hypersensitivity reaction. Intravenous injection of fucoidin to sensitized mice just before hapten challenge resulted in a significant and dose-dependent reduction of the ear swelling in contact hypersensitivity. The ear swelling caused by the hapten challenge was also inhibited when fucoidin was administered at the sensitization phase. Histological analyses of the ear sections revealed that the fucoidin-induced suppression of contact hypersensitivity reflected a marked inhibition of the ear edema and the leukocyte infiltration. The activity of fucoidin was specific in that its related saccharides exerted little effect on the reaction. These results suggest that CD62L may play an important role in both afferent and efferent phases of cutaneous DTH reaction. Since DTH response is one of the most significant features of several chronic inflammatory diseases, our data also show that blocking of CD62L function may be beneficial for the treatment of these diseases in humans.

A sandwich enzyme-linked immunosorbent assay for human interleukin-5

A sandwich enzyme-linked immunosorbent assay (ELISA) was developed for human interleukin-5 (hIL-5) using a combination of monoclonal anti-recombinant(r)-hIL-5 antibody and rabbit anti-r-hIL-5 IgG. Detection limit of this assay was estimated to be 7.8 pg/ml, which was about 10,000 times more sensitive than that of the bioassay using BCL1 cells of murine origin. This ELiSA was specific for hIL-5, showing no crossreactivity to recombinant human GM-CSF, IL-4, TNF-alpha, IFN-gamma and mouse IL-5 (mIL-5). The presence of 10% fetal calf serum did not interfere with the measurement of r-hIL-5. Coefficients of variation in intra-assay and interassay were 1.1-4.6% and 2.3-11.3%, respectively. These results indicate that this assay system can be quite useful in quantifying hIL-5 in various biological fluids.

Selective in vitro toxicity of purothionin conjugated to the monoclonal antibody 225.28S to a human high-molecular-weight melanoma-associated antigen

SummaryThe toxic agent purothionin was conjugated to the monoclonal antibody 225.28S to a human high-molecular-weight melanoma-accociated antigen. The toxic conjugate displayed in vitro toxicity to cultured human Colo 38 melanoma cells as indicated by reduced uptake of 3H-thymidine following a 24-h incubation and loss of cell viability following a 7-day incubation. The effect is dose-dependent and is specific since addition of the toxic conjugate to a cultured Raji B lymphoid cells did not affect their 3H-thymidine uptake or their viability.

Epitope mapping of monoclonal antibodies to tumor necrosis factor-α by synthetic peptide approach

A monoclonal antibody (mAb) against human tumor necrosis factor-alpha (TNF-alpha), designated 3B10, neutralizes biological activity of TNF-alpha, while another anti-TNF-alpha mAb 10F10 does not. In Western blot analysis, both mAbs bound to SDS-denatured TNF-alpha, indicating that the epitopes recognized by the mAbs are sequential but not conformational. To map precisely the epitopes of the mAbs, 76 overlapping octapeptides corresponding to an entire sequence of TNF-alpha were synthesized and their abilities to react with the mAbs were examined by enzyme-linked immunosorbent assay (ELISA). 3B10 bound to only one peptide at position 81-88 of TNF-alpha, SRIAVSYQ, whereas 10F10 was reactive with three overlapping peptides, ANALLANG (33-40), ALLANGVE (35-42), and LANGVELR (37-44). These results demonstrate that the 81-88 and 37-40 regions are important for the recognition of TNF-alpha by 3B10 and by 10F10, respectively. In solid-phase ELISA, 3B10 inhibited the binding of TNF-alpha to soluble TNF receptors, sTNF-RI and sTNF-RII. In contrast, 10F10 exerted little effect on the binding. TNF-alpha was detected by sandwich-type ELISA where 3B10 alone was used for both capture and detection, suggesting that 3B10 did not interfere with the trimer formation of TNF-alpha. The results obtained in this study suggest that the 81-88 region of TNF-alpha may participate in the receptor binding and that 3B10 neutralizes the activities of TNF-alpha by blocking the region.

Production and characterization of monoclonal antibodies against human natriuretic peptide receptor-A or -B

Monoclonal antibodies (mAbs) against human natriuretic peptide receptor-A (NPR-A) or NPR-B were produced using NPR-expressing Chinese hamster ovary (CHO) cells and soluble chimeric NPRs consisting of the extracellular domain of each receptor fused to Fc region of human IgG. Three anti-NPR-A mAbs, designated as A144, A397 and A416, bound to human NPR-A but not to NPR-B, while an anti-NPR-B mAb B136 reacted with human NPR-B but not with NPR-A. Competition analysis with the anti-NPR-A mAbs revealed that two mAbs, A144 and A416, recognize an identical or the adjacent site of the receptor and that A397 is directed against another epitope. No anti-NPR-A mAb affected binding of atrial natriuretic peptide (ANP) to NPR-A, while the anti-NPR-B mAb B136 inhibited binding of C-type natriuretic peptide (CNP) to NPR-B. Inhibition of the ligand-binding by B136 is specific in that the mAb showed no effect on the binding of ANP to NPR-A. B136 also blocked CNP-mediated intracellular cGMP accumulation in NPR-B-expressing cells. These results suggest that the region recognized by B136 may be related to the ligand-binding region of NPR-B. NPR-A- and NPR-B-expressing cells were selectively detected by immunostaining using the mAbs. These findings demonstrate that the mAbs will be useful to elucidate the role of the natriuretic peptides and their receptors in normal and disease states in humans [correction of human].

Two new quassinoid glycosides, yadanziosides N and O isolated from seeds of Brucea javanica (L.) merr

Two new quassinoid glycosides, yadanziosides N and O (1 and 2), were isolated from “Ya-dan-zi”, seeds of Brucea javanica (L.) MERR and the aglycone (4) of 2 was found to exhibit an antitumor activity against the murine P388 lymphocytic leukemia.

Construction and expression of a mouse-human chimeric antibody against human tumor necrosis factor-α

A mouse anti-human tumor necrosis factor-alpha (TNF-alpha) monoclonal antibody (MoAb), designated as 3B10, has previously been produced and characterized by our laboratory. We report here the construction and the expression of mouse-human chimeric antibody derived from the MoAb. cDNAs encoding variable regions of heavy and light chains were prepared from 3B10 cells by polymerase chain reaction, and introduced to mammalian expression vectors containing cDNA for human gamma1 and kappa constant regions, respectively. Cotransfection of the vectors into CHO cells resulted in production of antibody reacting with human TNF-alpha. In SDS-PAGE analysis, the chimeric antibody, c3B10, migrated at 170 kDa under a nonreducing condition, whereas two bands with 58 and 28 kDa appeared following treatment with 2-mercaptoethanol. Both c3B10 and mouse 3B10 neutralized the cytotoxic activity of human TNF-alpha to the same level, indicating that c3B10 holds the binding activity of its original MoAb. These findings suggest that the introduced genes for chimeric heavy and light chains are transcribed and translated to produce the chimeric heavy and light chain peptides, and that the peptides are assembled to form native IgG molecule. The chimeric anti-TNF-alpha antibody described in this study is expected to be less immunogenic and thus more suitable for possible clinical use.