Modular branched neurotensin peptides for tumor target tracing and receptor-mediated therapy: a proof-of-concept.

The aim of this study was to demonstrate that oligo-branched peptides can be effective either for spotlighting tumor cells that overexpress peptide receptors, or for killing them, simply by exchanging the functional moiety coupled to the conserved receptor-targeting core. Tetra-branched peptides containing neurotensin (NT) sequence are described here as selective targeting agents for human colon, pancreas and prostate cancer. Fluorophore-conjugated peptides were used to measure tumor versus healthy tissue binding in human surgical samples, resulting in validation of neurotensin receptors as highly promising tumor-biomarkers. Drug-armed branched peptides were synthesized with different conjugation methods, resulting in uncleavable adducts or drug-releasing molecules. Cytotoxicity on human cell lines from colon (HT-29), pancreas (PANC-1) or prostate (PC-3) carcinoma indicated branched NT conjugated with MTX and 5-FdU as the most active agents on PANC-1 (EC(50) 4.4e-007 M) and HT-29 (1.1e-007 M), respectively. Tetra-branched NT armed with 5-FdU was used for in vivo experiments in HT-29-xenografted mice and produced a 50% reduction in tumor growth with respect to animals treated with the free drug. An unrelated branched peptide carrying the same drug was completely ineffective. In vitro and in vivo results indicated that branched peptides are valuable tools for tumor selective targeting.

Barriers to effective tuberculosis control: a qualitative study.

SETTING: Emilia Romagna region, Italy. OBJECTIVE: To explore chest and infectious disease physicians' views of barriers to effective tuberculosis (TB) control and possible solutions. DESIGN: A series of nine focus groups including a total of 49 physicians. RESULTS: Three categories of barriers to effective TB control were identified: 1) uncertainty about appropriate clinical practice in the treatment of specific sub-groups of patients, such as the elderly or immigrants; 2) organisational factors, such as the availability of diagnostic services and of sufficient resources; and 3) multiple barriers to a viable and effective TB control programme in a country with a low prevalence of TB. CONCLUSIONS: The lack of integration and coordination of health services, as well as the scarcity of dedicated TB nurses, were perceived by the participants as crucial barriers to effective TB control. As a result of this study, a regional programme was started with the goals of quantifying the need for TB nurses and developing a better network for required health services. Qualitative studies such as this can be useful in improving TB control in a low-prevalence TB country, to identify problems and increase the participation of key professionals.

Mimicking the nicotinic receptor binding site by a single chain Fv selected by competitive panning from a synthetic phage library.

We have developed a novel competitive method to select from a phage display library a single chain Fv which is able to mimic the alpha-bungarotoxin binding site of the muscle nicotinic receptor. The single chain Fv was selected from a large synthetic library using alpha-bungarotoxin-coated magnetic beads. Toxin-bound phages were then eluted by competition with affinity purified nicotinic receptor. Recognition of the toxin by the anti-alpha-bungarotoxin single chain Fv was very similar to that of the receptor, such as indicated by the epitope mapping of alpha-bungarotoxin through overlapping synthetic peptides. Moreover, several positively charged residues located in the toxin second loop and in the C-terminal region were found to be critical, to a similar extent, for toxin recognition by the single chain Fv and the receptor. However, although the anti-alpha-bungarotoxin single chain Fv seems to mimic the toxin binding site of the nicotinic receptor, it does not bind other nicotinic agonists or antagonists. Our results suggest that competitive selection of anti-ligand antibody phages can allow the production of receptor-mimicking molecules directly and exclusively targeted at one specific ligand. Since physiologically and pharmacologically different ligands can produce opposite effects on receptor functions, such selective ligand decoys can have important therapeutic applications.

Mimotopes of the nicotinic receptor binding site selected by a combinatorial peptide library.

Peptide libraries allow selecting new molecules, defined as mimotopes, which are able to mimic the structural and functional features of a native protein. This technology can be applied for the development of new reagents, which can interfere with the action of specific ligands on their target receptors. In the present study we used a combinatorial library approach to produce synthetic peptides mimicking the snake neurotoxin binding site of nicotinic receptors. On the basis of amino acid sequence comparison of different alpha-bungarotoxin binding receptors, we designed a 14 amino acid combinatorial synthetic peptide library with five invariant, four partially variant, and five totally variant positions. Peptides were synthesized using SPOT synthesis on cellulose membranes, and binding sequences were selected using biotinylated alpha-bungarotoxin. Each variant position was systematically identified, and all possible combinations of the best reacting amino acids in each variant position were tested. The best reactive sequences were identified, produced in soluble form, and tested in BIACORE to compare their kinetic constants. We identified several different peptides that can inhibit the binding of alpha-bungarotoxin to both muscle and neuronal nicotinic receptors. Peptide mimotopes have a toxin-binding affinity that is considerably higher than peptides reproducing native receptor sequences.