Reduced immunogenicity and improved pharmacokinetics of humanized anti-Tac in cynomolgus monkeys

The anti-Tac mAb has been shown to bind to the p55 chain of the IL-2R, block IL-2 binding and inhibit T cell proliferation. A humanized form of anti-Tac (HAT) has been constructed that retains the binding properties of murine anti-Tac (MAT). These two mAb were evaluated in cynomolgus monkeys to compare relative immunogenicity and pharmacokinetic properties. Monkeys treated with HAT daily for 14 days exhibited anti-HAT antibody titers which were 5- to 10-fold lower than their MAT-treated counterparts and these antibodies developed later than in the MAT-treated monkeys. Two of four monkeys receiving a single injection of MAT developed anti-MAT antibodies, whereas none of four monkeys developed antibodies after a single treatment with HAT. In monkeys injected with either HAT or MAT daily for 14 days, the anti-antibody titers induced were inversely related to the amount of anti-Tac administered. Antibodies that developed against MAT were both anti-isotypic and anti-idiotypic, whereas those developed against HAT appeared to be predominantly anti-idiotypic. The pharmacokinetic properties, that is the half-life and area under the curve values, of HAT were also significantly different from those of MAT. The area under the curve values for HAT in naive monkeys were approximately twofold more than those for MAT, and the mean serum half-life of HAT was 214 h, approximately four- to fivefold more than MAT. These pharmacokinetic values were reduced in monkeys previously sensitized with HAT or MAT suggesting that the presence of anti-antibodies altered these parameters.

Reduced immunogenicity and improved pharmacokinetics of humanized anti-Tac in cynomolgus monkeys

The anti-Tac mAb has been shown to bind to the p55 chain of the IL-2R, block IL-2 binding and inhibit T cell proliferation. A humanized form of anti-Tac (HAT) has been constructed that retains the binding properties of murine anti-Tac (MAT). These two mAb were evaluated in cynomolgus monkeys to compare relative immunogenicity and pharmacokinetic properties. Monkeys treated with HAT daily for 14 days exhibited anti-HAT antibody titers which were 5- to 10-fold lower than their MAT-treated counterparts and these antibodies developed later than in the MAT-treated monkeys. Two of four monkeys receiving a single injection of MAT developed anti-MAT antibodies, whereas none of four monkeys developed antibodies after a single treatment with HAT. In monkeys injected with either HAT or MAT daily for 14 days, the anti-antibody titers induced were inversely related to the amount of anti-Tac administered. Antibodies that developed against MAT were both anti-isotypic and anti-idiotypic, whereas those developed against HAT appeared to be predominantly anti-idiotypic. The pharmacokinetic properties, that is the half-life and area under the curve values, of HAT were also significantly different from those of MAT. The area under the curve values for HAT in naive monkeys were approximately twofold more than those for MAT, and the mean serum half-life of HAT was 214 h, approximately four- to fivefold more than MAT. These pharmacokinetic values were reduced in monkeys previously sensitized with HAT or MAT suggesting that the presence of anti-antibodies altered these parameters.

High affinity human IgE receptor (Fc epsilon RI). Analysis of functional domains of the alpha-subunit with monoclonal antibodies

The binding of IgE to the high affinity Fc epsilon receptor (Fc epsilon RI) on mast cells and basophils is mediated by the alpha-subunit of the tetrameric receptor complex. Based on sequence homologies, the 50-kDa alpha-subunit is a member of the immunoglobulin superfamily of proteins and has two predicted disulfide-bonded loops. Monoclonal antibodies specific for the human alpha-subunit have been identified and separated into two major classes: inhibitory and noninhibitory antibodies. Inhibitory antibodies (i.e. 15A5) block 125I-IgE binding to a recombinant chimeric alpha-subunit (ch-alpha-protein) expressed on Chinese hamster ovary cells and immunoprecipitate 125I-labeled purified ch-alpha-protein. Noninhibitory antibodies (i.e. 22E7) immunoprecipitate both 125I-labeled ch-alpha-protein and the soluble complex of 125I-IgE cross-linked to ch-alpha-protein but do not block 125I-IgE binding to the ch-alpha-protein expressed on Chinese hamster ovary cells. Both classes of antibodies bind to natural Fc epsilon RI present on human basophils and induce histamine release from these cells. Inhibitory antibody 15A5 specifically binds to a peptide corresponding to amino acids 125-140 of the putative second domain of the alpha-subunit sequence. All the inhibitory antibodies compete with 125I-15A5 for binding to the ch-alpha-protein, indicating that these antibodies recognize inhibitory epitopes that are either identical or sterically overlapping. Noninhibitory antibodies (i.e. 22E7) do not block 125I-15A5 binding to the ch-alpha-protein. These data suggest that antibodies binding to the predicted second domain of the alpha-subunit can inhibit IgE binding to the alpha-subunit, while antibodies binding at a distance from this site do not inhibit IgE binding. These inhibitory antibodies may block IgE binding to the ch-alpha-protein by direct overlap, steric inhibition, or induced conformational changes of the receptor contact points for IgE.

[Medicamentous inhibitory therapy of precancerous lesions of the esophagus--3 and 5 year inhibitory effect of antitumor B, retinamide and riboflavin]

9633 subjects aged 40 to 65 were sampled from high-risk areas for esophageal cancer and examined by esophageal exfoliative cytology. 2531 and 3393 cases of markedly and mildly dysplastic patients were screened out respectively. Those with marked dysplasia were randomized into 3 groups and given respective medications: antitumor B (Chinese herbs), 4-ethoxycarbophenylretinamide (retinamide) and placebo. The subjects with mild dysplasia were randomly divided into 2 groups for riboflavin and placebo treatment. After medication for 3 or 5 years the subjects were reexamined by esophageal exfoliative cytology. The incidence of esophageal cancer in the antitumor B group after taking medication for 3 and 5 years was reduced by 52.2% and 47.3% respectively as compared with the placebo group. These differences were statistically significant (chi 2 = 8.9115, P less than 0.01; chi 2 = 10.9573, P less than 0.01). The incidence of esophageal cancer in the retinamide group after 3 years of medication was reduced by 37.3% as compared with control, while the incidence among patients treated for 5 years dropped by 43.2% relative to control. This difference was statistically significant (chi 2 = 9.2836, P less than 0.01). The incidence of esophageal cancer in the riboflavin group was reduced by 22.2% and 34.8% respectively. The above results indicate that secondary prevention of esophageal cancer is possible and that inhibitory therapy of precancerous lesions of the esophagus is effective in preventing esophageal cancer. This method needs further trial and study in high risk areas of esophageal cancer. The reliability of the experimental results is critically discussed.

[Effects of Apocynum hendersonii (Hook. f.) Woodson on cardiac electric and mechanical activity]

Calcium antagonist-like effect of Apocynum hendersonii on myocardiac preparations was observed in the present experiments. The action potential duration and contractility were decreased. Automatic or exciting activity in partially depolarized fibers was considerably inhibited or concealed. Observation in vivo showed that pacemaking in SA node and conducting in AV node area were inhibited.

Regulation of conductive Cl- transport in human fibroblasts

Under normal growth conditions, approximately 20% of the efflux of Cl- from human fibroblasts occurs via an electrically conductive pathway or Cl- channel. This basal Cl- conductance is insensitive to the Cl- -anion exchange inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and to the Cl- -cation cotransport inhibitor bumetanide. Exposure of the cells to dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP) for 15 min increases the electrically conductive component of Cl- efflux by approximately 20%. Unlike the basal Cl- conductance, the cAMP-activated channel is DIDS sensitive, indicating that cAMP activates a different Cl- pathway from the one responsible for the basal Cl- conductance. Elevation of intracellular Ca2+ by addition of the ionophore A23187 also stimulates Cl- efflux via a DIDS inhibitable, electrically conductive Cl- pathway. That the cAMP- and Ca2+-stimulated pathways are different is suggested by the observation that simultaneous exposure of cells to optimal levels of dibutyryl cAMP and A23187 results in an increased Cl- efflux equal to the sum of the two factors acting independently. Prostaglandin E1, a known activator of adenylate cyclase, also elevates the levels of intracellular free Ca2+ in these cells and concomitantly activates both the cAMP- and the Ca2+-stimulated Cl- channels. Although regulated, Cl- channels are known to function in the modulation of nerve and muscle excitability, their role in fibroblast function is not clear.

Pathways of Cl- transport in human fibroblasts

Three pathways of Cl- efflux were identified in normal human fibroblasts. Twenty percent of the total Cl- efflux is via an electrically conductive pathway with an efflux constant of 0.016 min-1. This pathway is insensitive to 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and bumetanide but is partially inhibited by anthracene-9-carboxylic acid. Twenty-five percent of the Cl- efflux occurs via Cl- with cation cotransport having an efflux constant of 0.020 min-1. This pathway is inhibited by bumetanide and is dependent on the simultaneous presence of Na+, K+, and Cl-. Under basal conditions, the energetics of this pathway indicate that it is operating close to equilibrium. Fifty percent of the Cl- efflux occurs via an anion exchange pathway having an efflux constant of 0.040 min-1 that is inhibited by DIDS or by removal of Cl- from the extracellular medium. Together these pathways account for 95% of the total Cl- efflux.

Biochemical and functional analysis of soluble human interleukin-2 receptor produced in rodent cells. Solid-phase reconstitution of a receptor-ligand binding reaction

The binding of interleukin-2 (IL-2) to the IL-2 receptor (IL-2R) on human T-cells is a key regulatory event which is absolutely required for T-cell-mediated immune responses. To understand further this binding event, we modified the human IL-2R gene to encode a secreted form of IL-2R. Secreted IL-2R was then expressed at very high levels (approximately 11 micrograms/10(6) cells/48 h) in rodent cells using gene-linked co-amplification. The soluble forms of IL-2R were shown to retain IL-2 affinity shown by cell-surface IL-2R (Kd approximately 18 nM) and were purified to homogeneity using IL-2 affinity chromatography. Purified, recombinant IL-2R and biotinylated IL-2 were used to establish a solid-phase receptor binding assay. Binding of IL-2-biotin was demonstrated to be dose-dependent at concentrations ranging from 10 to 1000 ng/ml, and the specificity of receptor-ligand binding was demonstrated by competition with non-biotinylated IL-2 and with anti-receptor antibodies known to block IL-2 binding in vivo. This immunosorbent receptor assay offers a simple and rapid method for studying the binding of IL-2 to human IL-2R.

Inhibition of proliferation of cultured rat liver epithelial cells at specific cell cycle stages by transforming growth factor-beta

Proliferation of early-passage propagable cultured rat liver epithelial cells derived from normal adult rats is markedly inhibited by transforming growth factor-beta (TGF-beta). Inhibition, which is completely reversible, is effected at two distinct points of the cell cycle, the G1/S border and the G0 or early G1 phase. With increasing passages in culture, hepatic epithelial cells progressively become less sensitive to the inhibitory effect of TGF-beta.

New synthetic cluster ligands for galactose/N-acetylgalactosamine-specific lectin of mammalian liver

Synthetic ligands containing up to six residues of nonreducing terminal galactose were prepared. The synthesis involved coupling of carboxyl groups of N-benzyloxy-carbonylaspartic acid or of N-benzyloxycarbonyltyrosyl-gamma-glutamylglutamic acid to the omega-amino group of the aglycon of a glycoside that contained up to three lactosyl residues. The benzyloxycarbonyl group was removed by hydrogenolysis before these ligands were tested as inhibitors to the binding of 125I-asialoorosomucoid to the galactose/N-acetylgalactosamine lectin, both soluble and on the surface of freshly isolated mammalian hepatocytes. Each addition of a galactosyl residue to an existing ligand structure invariably increased the binding affinity of such a ligand. However, at each level of galactose valency, the binding constant varied as much as 1000-fold depending on the structure of the ligand. At a given level of valency, the binding strength of a cluster ligand depended mainly on two factors: (1) the maximum spatial inter-galactose distances and (2) the flexibility of the arm connecting galactosyl residues and the branch points. It has been postulated that the three galactose-combining sites of the lectin are arranged in space at the vertexes of a triangle whose sides are 15, 22, and 25 A [Lee, Y. C., Townsend, R. R., Hardy, M. R., Lönngren, J., & Bock, K. (1984) in Biochemical and Biophysical Studies of Proteins and Nucleic Acids (Lo, T. B., Liu, T. Y., & Li, C. H., Eds.) pp 349-360, Elsevier, New York]. Ligands having inter-galactose distances shorter than these lengths were invariably poor ligands at their respective level of valency.(ABSTRACT TRUNCATED AT 250 WORDS)

Immobilization of proteins on partially hydrolyzed agarose beads

Treatment of agarose beads with mild acid (0.2 M HCl, 55 degrees C, several hours) hydrolyzes some of the glycosidic bonds between D-galactosyl residues and 3,6-anhydro-L-galactosyl residues, and thus produces aldehydo-groups useful for immobilization of amino compounds by reductive amination with NaCNBH3. More than 20 mg (0.3 mumol) of bovine serum albumin could be coupled per gram of partially hydrolyzed agarose beads. Arthrobacter neuraminidase immobilized by this method was useful for desialylation of sialyl glycoconjugates, and was found not to leach from the gel and to be much more thermostable than the free enzyme.

Recent research on the etiology of esophageal cancer in China

China could be expected to offer good opportunities for the investigation of esophageal cancer since it has both high and low incidence areas. However, it seems impossible to attribute the induction of esophageal cancer to one particular substance--it rather seems to be caused by a variety of factors. To the authors' opinion, esophageal cancer may originate from exposure to N-nitroso compounds or mycotoxins. Lack of certain trace elements or essential vitamins may also play a role. Contrary to France, which also has high incidence areas of esophageal cancer, excessive alcohol consumption is of no importance in China. It is not clear whether genetic factors can be discussed.