Novel antitenascin antibody with increased tumour localisation for Pretargeted Antibody-Guided RadioImmunoTherapy (PAGRIT).

The Pretargeted Antibody-Guided RadioImmunoTherapy (PAGRIT) method is based on intravenous, sequential administration of a biotinylated antibody, avidin/streptavidin and (90)Y-labelled biotin. The hybridoma clone producing the monoclonal antitenascin antibody BC4, previously used for clinical applications, was found not suitable for further development because of the production of an additional, nonfunctional light chain. In order to solve this problem, the new cST2146 hybridoma clone was generated. The monoclonal antibody ST2146, produced by this hybridoma, having the same specificity as BC4 but lacking the nonfunctional light chain, was characterised. ST2146 was found able to bind human tenascin at an epitope strictly related, if not identical, to the antigenic epitope of BC4. It showed, compared to BC4, higher affinity and immunoreactivity and similar selectivity by immunohistochemistry. Biodistribution studies of biotinylated ST2146 and three other monoclonal antitenascin antibodies showed for ST2146 the highest and more specific tumour localisation in HT29-grafted nude mice. On the overall, ST2146 appears to be a good alternative to BC4 for further clinical development of PAGRIT.

Leukotriene D4-induced activation of smooth-muscle cells from human bronchi is partly Ca2+-independent.

Cysteine-containing leukotrienes (cysteinyl-LTs) are potent bronchoconstrictors and play a key role in asthma. We found that histamine and LTD4 markedly constrict strips of human bronchi (HB) with similar efficacy. However, in human airway smooth-muscle (HASM) cells, LTD4, at variance with histamine, elicited only a small, transient change in intracellular calcium ion concentration. HASM cells express both Ca2+-dependent and -independent isoforms of protein kinase C (PKC) (i.e., PKC-alpha and PKC-alpha ). Western blot analysis showed that PKC-alpha is activated by histamine and, to a lesser extent, by LTD4, whereas only LTD4 translocates PKC-alpha. This translocation was specifically inhibited by the LTD4 antagonist pobilukast. Phorbol-dibutyrate ester (PDBu) (a PKC activator) contracted HB strips to the same extent in the presence as in the absence of extra- and intracellular Ca2+. In the absence of Ca2+, LTD4 contracted HB strips to the same extent as did PDBu, suggesting the involvement of a Ca2+-independent PKC in LTD4-mediated signal transduction. PDBu-induced desensitization and the PKC inhibitor H7 abolished the slow and sustained LTD4-triggered contraction of HB strips in the absence of Ca2+, although H7 did not greatly affect the response in the presence of the ion. Thus, in human airways, we identified a novel LTD4 transduction mechanism linked to bronchial smooth-muscle contraction, which is partly independent of Ca2+ and involves the activation of PKC-alpha.

LPS-induced serum TNF production and lethality in mice: effect of L-carnitine and some acyl-derivatives.

The effect of L-carnitine and some of its acyl derivatives on serum TNF production and lethality in a murine experimental endotoxin shock model was investigated. In some instances, serum IL-6 production was also evaluated. In this experimental model, C57BL/6 mice received 30 mg/kg LPS (E. cell 055:B5) injected intraperitoneally, while L-carnitine and its derivatives were administered according to different schedules. Serum levels of TNF and IL-6 were evaluated 1 h following LPS injection. The treated animals were also monitored daily for differences in body temperature, feeding, and survival for 10 days after LPS injection. Although some derivatives were able to significantly affect TNF production, the marked decrease in serum TNF levels of LPS-treated mice was not paralleled by a substantial increase in survival.

In vitro activation of murine peritoneal exudate cells (PEC) and peritoneal macrophages by ST 789.

ST 789 is a new synthetic compound characterized by an amino acidic group joined to the N9 position of the hypoxanthine ring, which has been shown recently to have immunomodulating properties and minimal toxicity. The drug has been reported to protect immunosuppressed mice from microbial infections and tumour growth, and to restore the mitogen-induced proliferation of splenocytes from immunosuppressed young mice. In this study, we show that in vitro addition of ST 789 is able to markedly augment the sheep red blood cells (SRBC) phagocytosis by PEC, and to potentiate the cytotoxic activity of peritoneal exudate (PE) macrophages (M phi) vs the L-M tumour cell line. We also found that ST 789 enhanced the rIFN-gamma-induced NO2- release from cultured PE M phi. Similarly, in vitro addition of ST 789 to the latter cultures significantly increased the production of interleukin 1 (IL-1) and tumour necrosis factor (TNF) induced by lipopolysaccharide (LPS). These studies demonstrate that ST 789 is a potent phagocyte activator for the induction of cytokine release, phagocytosis and cytotoxic activity against tumour cells in vitro.

Modulation of splenic lymphocyte activities by a new hypoxanthine derivative (ST 789) in immunosuppressed mice.

Splenic lymphocytes of experimentally-immunosuppressed mice of different age (10 weeks and 6 months) were studied to evaluate their functional response following subcutaneous and intraperitoneal treatment with the hypoxanthine derivative N-alpha-5-(1,6-dihydro-6-oxo-9-purinyl)pentyloxy-carbonyl-L- arginine (ST 789). Experimental immunosuppression was carried out by injecting hybrid B6D2F1 mice with a single dose of cyclophosphamide (100 mg/kg, i.p.) 2 hours prior to treatment with ST 789. In the young, we found that ST 789 markedly restored the splenocyte proliferative response, assessed as total amount of 3H-thymidine incorporated by mitogen-stimulated cells. In the adult, however, the ST 789-induced recovery was less pronounced. Finally, the effects of ST 789 treatment on Con A-induced IL-2 production by splenocytes were studied in normal and immunosuppressed mice of 10 weeks.

New potential immunoenhancing compounds. Synthesis and pharmacological evaluation of new long-chain 2-amido-2-deoxy-D-glucose derivatives.

A series of long-chain fatty acids and the corresponding 2-hydroxy, 2-oxo, 3-hydroxy acid glucosamides were evaluated as immunomodulating compounds. In a preliminary screening, 2-[(2-ethoxycarbonyloxy)tetradecanoylamino]-2-deoxy-D-glucos e (2b) and 2-(3-hydroxydodecanoylamino)-2-deoxy-D-glucose (5a) resulted to be the most effective in enhancing the glucosamine activity. The findings of in vitro-ex vivo tests (unidirectional mixed lymphocyte culture reaction and primary antibody production) and in vivo tests (delayed type hypersensitivity, protection against bacterial or fungal infection and against Sarcoma 180 or Lewis lung carcinoma transplants) were very encouraging and allowed to assume for the two substances a protective activity, presumably through the ability of activating phagocytic and NK cells.