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.

N-terminal myristylation of HBV preS1 domain enhances receptor recognition

The N-terminal portion of the large envelope protein of the human hepatitis B virus (HBV), the preS1 domain, plays a fundamental role in cell attachment and infectivity. Recent investigations have suggested that myristylation of preS1 Gly2 residue is essential for viral infectivity, but the importance of this post-translational modification on HBV-receptor interaction has not been elucidated completely. In this study we produced, using stepwise solid-phase chemical synthesis, the entire preS1[1-119] domain (adw2 subtype), and compared its receptor binding activity with the myristylated form, myristyl-preS1[2-119] in order to define the importance of fatty acid modification. Both synthetic proteins were fully characterized in terms of structural identity using TOF-MALDI mass spectrometry and analysis of tryptic fragments. Circular dichroism measurements indicated a low content of ordered structure in the preS1 protein, while the propensity of the myristylated derivative to assume a conformationally defined structure was more evident. HBV-receptor binding assays performed with plasma membranes preparations from the hepatocyte carcinoma cell line HepG2 clearly showed that the preS1[1-119] domain recognizes the HBV receptor, and confirmed that binding is occurring through the 21-47 region. The myristylated derivative recognized HBV receptor preparations with higher affinity than the preS1 domain, suggesting that the conformational transitions induced in the preS1 moiety by fatty acid post-translational modification are important for efficient attachment of viral particles to HBV receptors.

Novel ligands for the affinity-chromatographic purification of antibodies

Affinity chromatography represents one of the most powerful fractionation techniques for the large-scale purification of biotechnological products. Despite its potential, the use of this methodology is limited by the availability of specific ligands for each target. Combinatorial chemistry and molecular modeling, often combined, have become interesting and innovative methods for generating novel ligands, tailored to specific biotechnological needs. One of the greatest area of application has been the discovery of novel ligands for the purification of antibodies, which represent an emerging but very important class of innovative therapeutic agents for the treatment of a vast array of diseases. Naturally available affinity ligands, such as Protein A or G for IgG purification or lectins for IgA and IgM purification, which are obtained from microorganisms or genetically modified bacteria through complex and expensive procedures, are not well suited for large-scale purification and require moreover time-consuming analytical controls to check for the presence of contaminants which may affect the safety of the purified antibody for clinical purposes. Recent results suggest that the application of combinatorial technologies and molecular modeling for the discovery of synthetic ligands may open new avenues for the development of more efficient, less expensive and--more importantly--safer procedures for antibody purification at the industrial level.

Cloning and expression of a novel hepatitis B virus-binding protein from HepG2 cells

A direct involvement of the hepatitis B virus (HBV) preS1-(21-47) sequence in virus attachment to cell membrane receptor(s) and the presence on the plasma membranes of HepG2 cells of protein(s) with receptor activity for HBV have been suggested by many previous experiments. In this study, by using a tetravalent derivative of the preS1-(21-47) sequence, we have isolated by affinity chromatography from detergent-solubilized HepG2 plasma membranes a 44-kDa protein (HBV-binding protein; HBV-BP), which was found to closely correspond to the human squamous cell carcinoma antigen 1 (SCCA1), a member of the ovalbumin family of serine protease inhibitors. Comparison of SCCA1 sequence with the sequence of the corresponding HBV-BP cDNA, cloned by polymerase chain reaction starting from RNA poly(A)(+) fractions extracted from HepG2 cells, indicated the presence of only four nucleotide substitutions in the coding region, leading to three amino acid changes. Intact recombinant HBV-BP lacked inhibitory activity for serine proteases such as alpha-chymotrypsin and trypsin but inhibited with high potency cysteine proteases such as papain and cathepsin L. Direct binding experiments confirmed the interaction of recombinant HBV-BP with the HBV preS1 domain. HepG2 cells overexpressing HBV-BP after transfection of corresponding cDNA showed a virus binding capacity increased by 2 orders of magnitude compared with untransfected cells, while Chinese hamster ovary cells, which normally do not bind to HBV, acquired susceptibility to HBV binding after transfection. Native HBV particle entry was enhanced in transfected cells. Both recombinant HBV-BP and antibodies to recombinant HBV-BP blocked virus binding and internalization in transfected cells as well as in primary human hepatocytes in a dose-dependent manner. Our findings suggest that this protein plays a major role in HBV infection.

Affinity purification of immunoglobulins from chicken egg yolk using a new synthetic ligand

Due to the peculiar composition of the egg yolk and the lack of specific affinity ligands, Y immunoglobulins are normally purified using complex and time consuming procedures involving a combination of precipitation and chromatographic steps first to extract and capture and then to polish IgY. In this study, we have examined the applicability for IgY affinity purification of TG19318, a synthetic ligand for immunoglobulin, obtained from the screening of combinatorial libraries, and already characterized for its capability to purify immunoglobulins of class G, M, E and A. Soluble proteins were separated from the lipidic fraction of egg yolk by the water dilution method and loaded on to TG19318 affinity columns prepared by immobilizing the ligand on the commercially available support Emphaze. In a single chromatographic step TG19318 affinity columns led to an efficient capture of IgY directly from crude samples, and with a purity degree higher than 90%, as determined by densitometric scanning of SDS-PAGE analysis of bound fractions, and with full recovery of antibody activity, as determined by ELISA assay. Higher recovery and purity of IgY was obtained by using loading buffers at pH close to 6.5. Column capacity, determined by applying 4x excess IgY to 1 ml bed volume column, and eluting the retained immunoglobulins, was close to 65 mg of IgY per ml of resin. Chemical and chromatographic stability of TG19318/Emphaze was tested before and after various treatments. The derivatized matrix was found to be very stable, in terms of ligand leakage and maintenance of IgY binding capacity, under conditions of normal column usage, cleaning and storage.

Immunoglobulin specificity of TG19318: a novel synthetic ligand for antibody affinity purification

A synthetic ligand [TG19318], able to mimic protein A in the recognition of the immunoglobulin Fc portion, has been previously identified in our laboratory through the synthesis and screening of multimeric combinatorial peptide libraries. In this study we have fully characterized its applicability in affinity chromatography for the downstream processing of antibodies, examining the specificity and selectivity for polyclonal and monoclonal immunoglobulins derived from different sources. Ligand specificity was broader than protein A, since IgG deriving from human, cow, horse, pig, mouse, rat, rabbit, goat and sheep sera, IgY obtained from egg yolk, and IgM, IgA and IgE were efficiently purified on TG19318 affinity columns. Adsorbed antibodies were conveniently eluted by a buffer change to 0.1 M acetic acid or 0.1 M sodium bicarbonate pH 9, with full retention of immunological properties. Monoclonal antibodies deriving from cell culture supernatants or ascitic fluids were also conveniently purified on TG19318 affinity columns, even from very diluted samples. The affinity constant for the TG19318-IgG interaction was 0.3 microM, as determined by optical biosensor measurements. Under optimized conditions, antibody purity after affinity purification was close to 95%, as determined by densitometric scanning of SDS-PAGE gels of purified fractions, and maximal column capacity reached 25 mg Ig/ml support. In vivo toxicity studies in mice indicated a ligand oral toxicity greater than 2000 mg kg-1 while intravenous toxicity was close to 150 mg kg-1. Validation of antibody affinity purification processes for therapeutic use, a very complex, laborious and costly procedure, is going to be simplified by the use of TG19318, which could reduce considerably the presence of biological contaminants in the purified preparation, a very recurrent problem when using recombinant or extractive biomolecules as affinity ligands.

Affinity purification of immunoglobulin M using a novel synthetic ligand

While monoclonal antibodies of the G class can be conveniently purified by affinity chromatography using immobilized protein A or G, even on a large scale, scaling up IgM purification still presents several problems, since specific and cost-effective ligands for IgM are not available. A synthetic peptide (TG19318), deduced from the screening of a combinatorial peptide library, was characterized previously by our group for its binding properties for immunoglobulins of the G class and its applicability as a synthetic ligand for polyclonal and monoclonal IgG purification, from sera or cell culture supernatants. In this study, we have examined the ligand recognition properties for IgM, immobilizing the synthetic peptide on different affinity supports and examining its ability to purify IgMs from serum, ascitic fluid and cell culture supernatants. TG19318 affinity columns proved useful for a very convenient one-step purification of monoclonal IgMs directly from crude sources, loading the samples on the columns equilibrated with saline buffers at pH values ranging from 5 to 7, and eluting adsorbed IgM by a buffer change to 0.1 M acetic acid or 0.05-0.1 M sodium bicarbonate, pH 9.0. Antibody purity after affinity purification was very high, close to 85-95%, as determined by densitometric scanning of sodium dodecyl sulfate-polyacrylamide gels of purified fractions, and by gel permeation analysis. Antibody activity was fully recovered after purification, as determined by immunoassays. Column capacity was related to the type of support used for ligand immobilization, and ranged from 2 to 8 mg of IgM/ml of support.

Protein A mimetic peptide ligand for affinity purification of antibodies

A peptide mimicking protein A for its ability to recognize the Fc immunoglobulin portion has been identified through screening of a synthetic multimeric peptide library. Screening of the multimeric library, composed of randomized synthetic tripeptide tetramers, has been carried out using a very simple assay, measuring the library ability to interfere with the interaction between protein A and biotinylated immunoglobulins, monitored on solid phase using an enzyme-linked immunosorbent assay format. The tetrameric tripeptide identified after three screening cycles was produced in larger amounts and then immobilized in high yield on preactivated solid support for the preparation of affinity columns, which proved useful for a very convenient one-step purification of antibodies directly from crude sera. Antibody purity after affinity purification was close to 95 per cent, as determined by densitometric scanning of sodium dodecyl sulphate-polyacrylamide gel electrophoresis gels of purified fractions, and up to 2 mg of antibody could be purified from 1 ml of peptide-derivatized affinity support. The ligand was stable to treatment with a vast array of sanitation agents, such as ethanol and 0.1 M sodium hydroxide, and to repeated use, thus making the ligand applicability extremely attractive for the purification of monoclonal antibodies for therapeutic use. Column binding selectivity was similar to that of protein A-affinity columns, since immunoglobulin G from several sources (rabbit, goat, sheep, mouse) was conveniently purified, with no detection of leaked ligand fragments in the purified preparations.

An expression system for the single-step production of recombinant human amidated calcitonin

Amidating mouse pituitary cells (AtT-20) have been engineered to secrete human calcitonin (hCT) in the fully active amidated form, without the need of additional enzymatic or chemical modifications. The 141-residue human calcitonin precursor has first been cloned in the eucaryotic expression vector pRc/RSV, and the resulting plasmid pRc/RSV/hCT introduced in AtT-20 cells. After transfection, 122 independent clones resistant to G-418 were selected and screened for calcitonin production using a competitive ELISA specifically designed to detect the amidated form of calcitonin. One of these clones was amplified and showed expression of 17 ng/ml of hCT, with a 70% increase in productivity after cAMP treatment. Calcitonin was partially purified from culture medium by two sequential steps of reverse-phase chromatography and characterized in terms of immunoreactivity and molecular weight by TOF-MALDI mass spectroscopy, which confirmed the intended chemical nature and the presence of the C-terminal amidated residue.

Topological mimicry of cross-reacting enantiomeric peptide antigens

Rabbit polyclonal antibodies against multimeric peptide antigens were found to cross-react to a significant extent with topologically related variants of the parent antigen, where the chirality of each amino acid residue (inverso derivatives), or the peptide sequence orientation (retro derivatives), was inverted or where both modifications were simultaneously introduced (retro-inverso derivatives). All peptide variants displayed similar recognition properties for antibodies and similar dose-dependent inhibitory effects on the interaction between immobilized parent antigen and corresponding antibodies. Importance of peptide side chain topology on antigenicity was evaluated analyzing the recognition properties of two sequence-simplified parent peptide variants, one lacking of the side chains in the sequence odd position and the other in even position. These two variants, prepared introducing glycine residues alternatively in the parent peptide sequence, were found to cross-react to a significant extent with the original antibody raised against the parent peptide. Analysis of molecular models of peptide enantiomeric variants in the elongated all-trans configuration suggested that the topological equivalence of alternating side chains could lead to the formation of similar recognition surfaces, thus mimicking the parent peptide antigenic structure.

Antigenicity of topochemically related peptides

Antibodies raised in rabbits against multimeric all-L peptides (MAP's) were first made monospecific by affinity chromatography on immobilized antigen columns and then tested for their ability to cross-react with topologically related variants of the parent antigen, where the chirality of each amino-acid residue (inverso derivatives), or the peptide sequence orientation (retro derivatives), was inverted, or where both modifications were simultaneously introduced (retro-inverso derivatives). Retro, inverso, and retro-inverso forms of the parent peptide were prepared, both in the linear as well as in the BSA-conjugated form, and found to cross-react to a significant extent with affinity purified polyclonal antibodies raised against the parent peptide. Peptide variants displayed similar dose-dependent inhibitory effects on the interaction between immobilized parent antigen and affinity purified antibodies. Analysis of molecular models of the peptide variants in the trans-configuration suggested that the topological equivalence of alternating side chains in the series of related peptides may be responsible for the observed cross-recognition, leading to the formation of similar recognition surfaces which could mimic the parent peptide antigenic structure.

Affinity purification of polyclonal antibodies using immobilized multimeric peptides

The possibility of using multiple antigenic peptides (MAP) not only for the production and characterisation of antibodies but also for their purification by affinity chromatography, has been explored with two different tetrameric MAPs synthesised starting from a tetradentate lysine core. Recognition selectivity and specificity of the multimeric antigens were retained after immobilization on preactivated affinity supports, allowing convenient antibody purification directly from crude sera in a single chromatographic step. Since antibodies raised against MAPs recognise very frequently the N-terminal portion of the peptide antigen, results suggest that only a limited number of peptide chains remains covalently linked to the solid phase, leaving the others uncoupled and free to interact fully with the antibody. Recovery of antibody immunoreactivity from affinity purifications on MAP-columns was much higher than that obtained from columns prepared by immobilizing at the same density the corresponding linear peptide antigen. The purity of thus obtained antibodies is also far superior, as detected by SDS-PAGE analysis. Retention of the multimeric peptide recognition properties for the corresponding antibodies after immobilization on solid supports suggests that production, characterization, and even the affinity purification of anti-peptide antibodies, could be carried out simply and conveniently via the synthesis of a single multimeric antigen, without additional steps.

Binding of type I IL-1 beta receptor fragment 151-162 to interleukin-1 beta

The relevance of hydropathically complementary sequences in ligand receptor interactions has been evaluated in the interleukin-1 beta/receptor type I case. Computer assisted comparison of the hydropathic profiles of IL-1 beta and its receptor (type I) identified residues 88-99 in IL-1 beta and 151-162 in the receptor as the sequences pair characterized by the highest level of hydropathic complementarity. These fragments, once produced by chemical synthesis and derivatized with biotin, displayed specific recognition properties for each other, as detected by solid phase binding assays. Binding between the two fragments occurred independently from the assay format, was saturable and specifically inhibited by unlabeled peptides. Receptor fragment (151-162) derivatized with biotin recognized also full length recombinant IL-1 beta, and binding was inhibited to 50% in the presence of 3 microM IL-1 beta (88-99) peptide. Interaction specificity was further confirmed by the non competitive effect on the interaction of a sequence scrambled IL-1 beta (88-99) peptide. In a similar way, full length biotinylated IL-1 beta recognized immobilized IL-1 beta receptor fragment (151-162), and this interaction was diminished in the presence of unlabeled receptor fragment or IL-1 beta Results indicate that IL-1 beta receptor fragment (151-162) binds IL-1 beta recognizing the IL-1 beta (88-99) sequence, thus suggesting a possible role of these fragments in the protein/receptor recognition surface.

Effect of anaesthesia on serum levels of LH and FSH in man with and without GnRH test

The effect of anaesthesia with atropine and pentobarbital (PB) in three groups of volunteers has been tested. The dose used for the anaesthesia was 20 mg/kg body weight of PB. The experiment was performed with and without stimulation test with GnRH. Anaesthesia was shown to increase serum levels of LH and to increase the response to stimulation with GnRH. Atropine and mental stress seem to have no effect on the hormones. No variation in serum levels of FSH in the anaesthesized volunteers was noted. The data obtained have been statistically controlled.

[Clinico-functional observations on the use of guacetisal in the treatment of chronic obstructive bronchopneumopathy]

The results of an approximately 14-day treatment with 500 mg broncaspin capsules in 25 patients with recrudescent chronic bronchitis are presented. There was a marked, constant improvement in the subjective and objective symptomatology, and in respiratory function indices. The expectoration cell parameters displayed changes consonant with the therapeutic effect. Local and general tolerance were good overall.

[Effects of pentobarbital on serum PRL and TSH in the basal condition and under TRH stimulation in man: preliminary note]

The Authors have tested serum levels of PRL and TSH in six healthy males, anaesthesized with 20 mg./Kg. body weight of pentobarbital with and without stimultion with TRH. PB has no effect on serum levels of TSH but there is an inhibition of PRL release 180', 240' and 360' after the administration of the drug. The AA. have found no effects of PB on the stimulation test with TRH. All the data obtained have been examined with Student's "T" test.

[Effect of atropine on hypophyseal gonadotropins in the basal condition and under GnRH stimulation]

The Authors have tested serum levels of LH and FSH in 10 healthy males after stimulation test with GnRH preceded by administration i.m. of 1 mg. of atropine 10' and 1 hour before the test, to examine some interferences of the drug on ipophisary gonadotropins. Atropine has no effect on LH and FSH release because there are no differences between mean values of the hormones during the test with and without atropine, at any time it is administered. All the data obtained have been controlled with Student's "t" test.