Muramyl dipeptide bound to poly-L-lysine substituted with mannose and gluconoyl residues as macrophage activators

Evidence for plasmid DNA exchange after polyplex mixing

The self-assembly of a plasmid DNA (pDNA) with cationic polymers or cationic liposomes forms nanosized supramolecular structures called lipoplexes, polyplexes and lipopolyplexes. Here, we report that when two polyplex preparations made using the same polymer and the same pDNA but labelled with two different fluorophores are mixed together, pDNA molecules are exchanged. Indeed, when Flu-pDNA complexed with histidinylated lPEI (Flu-pDNA/His-lPEI) polyplexes are mixed with Cy5-pDNA complexed with histidinylated lPEI (Cy5-pDNA/His-lPEI) polyplexes, a high quantity of polyplexes emitting dual fluorescence is observed and FRET indicates that one single polyplex contains two kinds of fluorescent pDNA molecules. This phenomenon depends on the polymer-type and the strength of the pDNA/polymer interaction. No exchange is observed with polylysine polyplexes, caged His-lPEI polyplexes, lipoplexes, lipopolyplexes or when His-lPEI polyplexes are mixed with lipoplexes. Our results suggest that aggregation or collapse of polyplexes occurs after their interaction leading to their unpackaging followed by the formation of new polyplexes with the exchange of pDNA.

Influence of mannosylation on immunostimulating activity of adamant-1-yl tripeptide

The mannosylated derivative of adamant-1-yl tripeptide (D-(Ad-1-yl)Gly-L-Ala-D-isoGln) was prepared to study the effects of mannosylation on adjuvant (immunostimulating) activity. Mannosylated adamant-1-yl tripeptide (Man-OCH(2) CH(Me)CO-D-(Ad-1-yl)Gly-L-Ala-D-isoGln) is a non-pyrogenic, H(2) O-soluble, and non-toxic compound. Adjuvant activity of mannosylated adamantyl tripeptide was tested in the mouse model with ovalbumin as an antigen and in comparison to the parent tripeptide and peptidoglycan monomer (PGM, β-D-GlcNAc-(1→4)-D-MurNAc-L-Ala-D-isoGln-mesoDAP(εNH(2) )-D-Ala-D-Ala), a well-known effective adjuvant. The mannosylation of adamantyl tripeptide caused the amplification of its immunostimulating activity in such a way that it was comparable to that of PGM.

Bi- and trivalent glycopeptide mannopyranosides as inhibitors of type 1 fimbriae-mediated bacterial adhesion: variation of valency, aglycon and scaffolding

In order to test relevant structural parameters for effective inhibition of mannose-specific bacterial adhesion, bi- and trivalent glycopeptide α-D-mannopyranosides were synthesized that differ in their conformational properties as well as in the spatial arrangement of attached mannosyl residues. They were tested in an inhibition adhesion assay with fluorescent Escherichia coli bacteria and testing results were referenced to the inhibitory potency of methyl α-D-mannopyranoside. It was shown, that besides the nature of the mannoside aglycon moiety, scaffolding of α-D-mannopyranosides on a peptide backbone was important for the performance of the synthesized glycopeptides as inhibitors of bacterial adhesion.

Global analysis of lysine ubiquitination by ubiquitin remnant immunoaffinity profiling

Protein ubiquitination is a post-translational modification (PTM) that regulates various aspects of protein function by different mechanisms. Characterization of ubiquitination has lagged behind that of smaller PTMs, such as phosphorylation, largely because of the difficulty of isolating and identifying peptides derived from the ubiquitinated portion of proteins. To address this issue, we generated a monoclonal antibody that enriches for peptides containing lysine residues modified by diglycine, an adduct left at sites of ubiquitination after trypsin digestion. We use mass spectrometry to identify 374 diglycine-modified lysines on 236 ubiquitinated proteins from HEK293 cells, including 80 proteins containing multiple sites of ubiquitination. Seventy-two percent of these proteins and 92% of the ubiquitination sites do not appear to have been reported previously. Ubiquitin remnant profiling of the multi-ubiquitinated proteins proliferating cell nuclear antigen (PCNA) and tubulin alpha-1A reveals differential regulation of ubiquitination at specific sites by microtubule inhibitors, demonstrating the effectiveness of our method to characterize the dynamics of lysine ubiquitination.

Synthesis of glycocluster-tumor antigenic peptide conjugates for dendritic cell targeting

The use of dendritic cells (DC) for the development of therapeutic cancer vaccines is attractive because of their unique ability to present tumor epitopes via the MHC class I pathway to induce cytotoxic CD8+ T lymphocyte responses. C-Type membrane lectins, DC-SIGN and the mannose receptor (MR), present on the DC surface, recognize oligosaccharides containing mannose and/or fucose and mediate sugar-specific endocytosis of synthetic oligolysine-based glycoclusters. We therefore asked whether a glycotargeting approach could be used to induce uptake and presentation of tumor antigens by DC. To this end, we designed and synthesized glycocluster conjugates containing a CD8+ epitope of the Melan-A/Mart-1 melanoma antigen. These glycocluster-Melan-A conjugates were obtained by coupling glycosynthons: oligosaccharyl-pyroglutamyl-beta-alanine derivatives containing either disaccharides, a dimannoside (Manalpha-6Man) or lactoside, or a Lewis oligosaccharide, to Melan-A 16-40 peptide comprising the 26-35 HLA-A2 restricted T cell epitope, extended with an oligolysine stretch at the C-terminal end. We showed by confocal microscopy and flow cytometry that fluorescent-labeled Melan-A glycoclusters containing either dimannoside or Lewis oligosaccharide were taken up by DC and concentrated in acidic vesicles; conversely lactoside glycopeptides were not at all taken up. Furthermore, using surface plasmon resonance, we showed that dimannoside and Lewis-Melan-A conjugates bind MR and DC-SIGN with high affinity. DC loaded with these conjugates, but not with the lactose-Melan-A conjugate, led to an efficient presentation of the Melan-A epitope eliciting a CD8+ T-lymphocyte response. These data suggest that synthetically designed glycocluster-tumor antigen conjugates may induce antigen cross-presentation by DC and represent a promising tool for the development of tumor vaccines.

Mannan-mediated gene delivery for cancer immunotherapy

Recent years have seen a resurgence in interest in the development of efficient non-viral delivery systems for DNA vaccines and gene therapy. We have previously used oxidized and reduced mannan as carriers for protein delivery to antigen-presenting cells by targeting the receptors that bind mannose, resulting in efficient induction of cellular responses. In the present study, oxidized mannan and reduced mannan were used as receptor-mediated gene transfer ligands for cancer immunotherapy. In vivo studies in C57BL/6 mice showed that injection of DNA encoding ovalbumin (OVA) complexed to oxidized or reduced mannan-poly-L-lysine induced CD8 and CD4 T-cell responses as well as antibody responses leading to protection of mice from OVA+ tumours. Both oxidized and reduced mannan delivery was superior to DNA alone or DNA-poly-L-lysine. These studies demonstrate the potential of oxidized and reduced mannan for efficient receptor-mediated gene delivery in vivo, particularly as DNA vaccines for cancer immunotherapy.

Potocytosis and cellular exit of complexes as cellular pathways for gene delivery by polycations

BACKGROUND

Although polycations are among the most efficient nonviral vectors for gene transfer, the gene expression they allow is still too low for in vivo applications. To engineer more potent polycationic vectors, the factors governing the intracellular trafficking of a plasmid complexed with current polycations need to be identified.

METHODS AND RESULTS

The trafficking of plasmid DNA complexed to glycosylated polylysines or polyethylenimine (PEI) derivatives was studied by electron microscopy of human airway epithelial cells. The cellular processing of complexes varied with their size and the polycation derivative used: large complexes (> 200 nm) made with all polycationic vectors studied were internalized by macropinocytosis. In contrast, intermediate (100-200 nm) ligand-coupled polylysine and PEI complexes primarily entered through clathrin-coated pits. Complexes were then found in endosomal vesicles, accumulated in lysosomes or vesicles near the nucleus and their nuclear entry was limited. For the population of small complexes (< or = 100 nm) obtained with PEI derivatives, they were internalized through caveolae and pursued a traffic pattern of potocytosis to the endoplasmic reticulum where their fate remains unclear. Finally, some complexes exited the cells either by regurgitation when PEI derivatives were used or through an exosome-like pathway for glycosylated-polylysine complexes.

CONCLUSIONS

The different pathways of complex trafficking observed in relation with complex size imply the development and study of vectors forming complexes with definite size. Moreover, the complex exit we describe may contribute to the well-established short-term efficiency of gene transfer based on synthetic vectors. It favors the engineering of vectors allowing repeated treatment.

Carrier-based strategies for targeting protein and peptide drugs to the lungs

With greater interest in delivery of protein and peptide-based drugs to the lungs for topical and systemic activity, a range of new devices and formulations are being investigated. While a great deal of recent research has focused on the development of novel devices, attention must now be paid to the formulation of these macromolecular drugs. The emphasis in this review will be on targeting of protein/peptide drugs by inhalation using carriers and ligands.

The role of galactose, lactose, and galactose valency in the biorecognition of N-(2-hydroxypropyl)methacrylamide copolymers by human colon adenocarcinoma cells

PURPOSE

To examine the beta-galactoside and beta-lactoside binding capacity of three human colon-adenocarcinoma cell lines and their sugar specificity, using N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugates of galactosamine, lactose, and triantennary galactose.

METHODS

Three types of HPMA copolymers containing the saccharide epitopes galactosamine (P-Gal), lactose (P-Lac), or triantennary galactose (P-TriGal) were synthesized. The relationship between the content of the saccharide moieties, the valency of the galactose residues, and their biorecognition by the cell lines (Colo-205, SW-480, and SW-620) was investigated using flow cytometry and confocal fluorescence microscopy analysis.

RESULTS

The binding of the glycoconjugates to the human colonadenocarcinoma cell lines was dependent on the type and the number of bound sugar residues per macromolecule. The higher the sugar contents in the HPMA copolymers, the higher the extent of binding. Although introduction of galactoside residues into the HPMA copolymer resulted in a significant increase in the binding of the copolymers to the cells, low biorecognition of the lactoside-containing HPMA copolymers by all cell lines used was observed. The trivalent galactoside-containing HPMA copolymers did not yield a notable glycoside cluster effect for the beta-galactoside-binding lectin expressed on human colon-adenocarcinoma cells. Among the various cell line little differences in the extent of binding of the glycopolymers to the cells were observed. The data on the internalization of HPMA copolymer conjugates obtained by confocal fluorescence microscopy correlated well with the flow cytometry analysis of their biorecognition by target cells.

CONCLUSIONS

The lectin-mediated endocytosis of the HPMA glycoconjugates in human colon cancer cell lines suggests their potential use as targeting tools of cytotoxic drugs to colon adenocarcinoma.

Uptake of plasmid/glycosylated polymer complexes and gene transfer efficiency in differentiated airway epithelial cells

BACKGROUND

We have studied gene transfer efficiency of glycosylated polylysines and glycosylated polyethylenimines as vectors in immortalized differentiated airway gland serous cells and primary cultures of human airway surface epithelial cells.

METHODS AND RESULTS

In both cell types, lactosylated PEI was more efficient for gene transfer than unsubstituted PEI and lactosylated polylysine which requires the presence of endosomolytic agents. However, for all the vectors tested, gene transfer efficiency was lower in differentiated cells as compared with poorly differentiated cells. The presence of membrane lectins, i.e. cell surface sugar-specific receptors, was evaluated using fluorescein-conjugated neoglycoproteins and microscopy or flow cytometry. In differentiated airway surface epithelial cells, membrane lectins were not expressed and plasmid DNA/fluorescein-conjugated glycosylated polymer complexes were not incorporated. This accounted in part for the lack of gene transfer efficiency in these cells. In contrast, in differentiated airway gland serous cells, expression of lectins and their endocytotic properties appeared to be similar to that observed in undifferentiated cells, and plasmid DNA/fluorescein-conjugated glycosylated polymer complexes were incorporated in similar amounts by cells in both differentiated states

CONCLUSIONS

Glycosylated PEI appears to be a promising gene delivery system since it is more efficient than the sugar-free polymer and does not require endosomolytic agents. However, in differentiated airway gland serous cells, a low gene transfer efficiency was observed that could not be attributed to low expression of membrane lectins or low uptake of glycosylated complexes. An impaired intracellular trafficking of glycosylated complexes in differentiated airway gland serous cells is suggested.

Intracellular rate-limiting steps of gene transfer using glycosylated polylysines in cystic fibrosis airway epithelial cells

To identify the intracellular barriers to efficient gene transfer, we studied the intracellular trafficking of biotinylated plasmid DNA complexed with either fluorescein-conjugated lactosylated or mannosylated polylysine by confocal microscopy. Both are known to be taken up by cystic fibrosis airway epithelial cells (SigmaCFTE29o- cells), but their gene transfer efficiencies differ markedly: lactosylated polylysine is the most efficient glycosylated polylysine while mannosylated polylysine is quite inefficient for gene transfer. Mannosylated complexes appeared to stay longer in endosomes labeled by anti-transferrin receptor antibody than lactosylated complexes (from 30 min to 3 h and from 10 min to 30 min, respectively). At 24 h, higher percentages of mannosylated than lactosylated complexes were localized inside lysosomes labeled by anti-LAMP-1 antibody (41.8 +/- 6.6% versus 19.8 +/- 5.2%, respectively, P < 0.05). Between 30 min and 8 h, complexes reached the nuclei labeled by anti-lamin A/C antibody and no difference was observed between the nuclear amounts of mannosylated and lactosylated complexes. However, as analyzed by a nuclease S1 transcription assay, initiation of transcription was prevented when plasmid DNA was complexed to mannosylated polylysine. Our results indicate that the major limiting steps for mannosylated versus lactosylated polylysine transfer of plasmid DNA are delayed exit from endosomes, high accumulation in lysosomes and limited transcription of the complexed plasmid DNA.

Intracellular processing and stability of DNA complexed with histidylated polylysine conjugates

BACKGROUND

Glycosylated polylysines and histidylated polylysines complexed with plasmid DNA (pDNA) were proposed to develop polymer-based gene delivery systems. The present work has been undertaken in two steps to study the uptake and the intracellular processing of pDNA, which are still poorly understood in the polyfection pathway.

METHODS AND RESULTS

The kinetics of the uptake and the intracellular processing of pDNA complexed with lactosylated polylysine, histidylated polylysine or histidylated polylysine bearing lactosyl residues (polyplexes) into a CF human airway epithelial cell line were assessed by flow cytometry and confocal microscopy. Complexes formed from histidylated polylysine, even though they were less taken up by cells, show better transfection efficiency with compared with lactosylated complexes. Lactosylated polymers segregated more rapidly when compared with non-lactosylated polymers into compartments different from those containing pDNA on internalization. Intracellular location and pH measurements indicated that polymers ended up in compartments of pH approximately 6.2 while pDNA reached less acidic compartments of pH approximately 6.6. These compartments did not contain the LAMP-1 lysosomal marker.

CONCLUSIONS

The present study exhibits that, upon internalization, pDNA and polylysine conjugates underwent segregation with a rate depending on the polylysine substitution and polymer degradation. The better transfection efficiency of polyplexes with histidylated polylysine can be ascribed to their prolonged stability inside the endocytic vesicles that likely favored the pDNA escape in the cytosol.

Poly[Lys-(AEDTP)]: a cationic polymer that allows dissociation of pDNA/cationic polymer complexes in a reductive medium and enhances polyfection

Polyplexes of high stability resulting from the condensation of a plasmid DNA by a cationic polymer are widely used to develop polymer-based gene delivery systems. However, the plasmid must be released from its vector once inside the cells for an efficient expression of the exogenous gene in the cell nucleus. We have designed a disulfide-containing cationic polymer termed poly[Lys-(AEDTP)] which allowed for the formation of polyplexes and the release of the plasmid in a reductive medium. The amino groups of polylysine were substituted with 3-(2-aminoethyldithio)propionyl residues in order to have each amino group of poly[Lys-(AEDTP)] interacting with a phosphate DNA linked to the polymer backbone via a disulfide bond. As evidenced by agarose gel electrophoresis and ethidium bromide/pDNA fluorescence restoration, poly[Lys-(AEDTP)] polyplexes were decondensed and the plasmid released upon treatment with either dithiothreitol, glutathione in the presence of glutathione reductase, or the thioredoxin reductase. Electron microscopy showed that polyplexes exhibiting spherical particles of a mean size at about 100 nm were decondensed in the presence of glutathione and exhibited filamentous aggregates. Finally, we found that the transfection of 293T7 and HepG2 cells was 10- and 50-fold more efficient with poly[Lys-(AEDTP)] polyplexes, respectively, than with poly[Lys] polyplexes. These results indicate that disulfide-containing cationic polymers must be borne in mind for developing polymer-base gene delivery systems.

Enhanced biorecognition and internalization of HPMA copolymers containing multiple or multivalent carbohydrate side-chains by human hepatocarcinoma cells

N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers containing pendant saccharide moieties (galactosamine, lactose, and triantennary galactose) were synthesized. The relationship between the content of saccharide moieties and three-dimensional arrangement of galactose residues and their biorecognition and internalization by human hepatocarcinoma HepG2 cells was investigated. The results obtained clearly indicated preferential binding of the trivalent galactose and the lactose-containing copolymers to these cells. The higher the saccharide moieties content in HPMA copolymers, the higher the levels of binding. The biorecognition of the glycosylated HPMA copolymers by HepG2 cells was inhibited by free lactose. The data on the internalization and subcellular trafficking of HPMA copolymer conjugates obtained by confocal fluorescence microscopy correlated well with the flow cytometric analysis of their biorecognition by target cells. Structural features of the glycosides responsible for the specific recognition of the HPMA copolymers have been identified. The results underline the potential of glycosylated HPMA copolymers for delivery of pharmaceutical agents to hepatocarcinoma cells.

Gene therapy of cystic fibrosis: the glycofection approach

Many cells express surface membrane lectins that selectively bind and carry glycoconjugates into intracellular endosomes; in addition, various intracellular membrane and soluble lectins act as shuttles between different compartments. On this basis, we developed glycosylated polycations, now called glycofectins (glycosylated polylysine and polyethyleneimine). Recently, we set up a simple way to transform oligosaccharides into glycosynthons suitable to substitute proteins or polymers. Glycofectins bind plasmid DNA leading to compact glycoplexes. Glycoplexes prepared with glycofectins were found to be much more active than naked plasmid to transfer genes to various types of cells including human airway epithelial and serous cells. The gene transfer efficiency was found to depend on the nature of the sugars borne by glycofectins. It appeared that the sugar-dependent efficiency was not only related to the uptake but also to the intracellular traffic of glycoplexes.

Synthesis of clustered glycoside-antigen conjugates by two one-pot, orthogonal, chemoselective ligation reactions: scope and limitations

Major histocompatibility class II antigens have been bound to clustered glycosides for selective targeting of the dendritic cell mannose receptor. Di-, tetra-, and octavalent glycoside-antigen conjugates have been obtained after two, orthogonal, hydrazone/thioether ligations, performed by using thio derivatives of D-mannose, D-galactose, or D(-)-quinic acid, glyoxylyl (or hydrazino)-N-chloroacetylated lysinyl trees, and N-terminal hydrazino (or glyoxylyl) peptide antigens. Successful one-pot condensations have been developed to account for the nature of the antigens and the valency of the trees.

Histidylated polylysine as DNA vector: elevation of the imidazole protonation and reduced cellular uptake without change in the polyfection efficiency of serum stabilized negative polyplexes

We have reported that polylysine substituted with histidyl residues (His) was suited to make complexes with plasmid DNA (pDNA) and to transfect cells in vitro in the presence of serum. The present study was performed to determine whether the acetylation of the alpha-amino group of histidyl residues (AcHis) had an influence on the size and the charge of polyplexes and on their transfection efficiency. We found that the presence of free alpha-amino groups allowed the formation of smaller polyplexes but did not modify the zeta potential of +17 mV. At a physiological salt concentration, the adsorption of many serum proteins on His- and AcHis-polyplexes reduced their size below 100 nm, inhibited their aggregation, and reversed their zeta potential to -25 mV. The acetylation of the alpha-amino groups reduced slightly the adsorption of serum proteins. The presence of the alpha-amino groups increased the pK of the imidazole protonation of histidine bound to polylysine from pH 5.8 to 6.9; in addition, the protonation was further elevated in the presence of pDNA. Serum stabilized negative histidylated polyplexes were less taken up by cells but their transfection efficiency did not decrease; depending on the cell line, His-polyplexes were more efficient than AcHis-polyplexes. The results indicate that (i) the alpha-amino groups of histidyl residues bound to polylysine favorably influence the size and the transfection efficiency of polyplexes, (ii) the alpha-amino groups also elevate the imidazole protonation of His-polyplexes, which is suited to destabilize the membrane of early endocytic vesicles in order to favor pDNA delivery in the cytosol, and (iii) the absorption of selective serum proteins on His-polyplexes could be a way for in vivo gene targeting.

Histidylated polylysine as a synthetic vector for gene transfer into immortalized cystic fibrosis airway surface and airway gland serous cells

BACKGROUND

We recently designed a cationic polymer called histidylated polylysine made of polylysine partially substituted with histidyl residues which become protonated at slightly acidic pH. This polymer is thought to induce the leakage of acidic vesicles containing plasmid/histidylated polylysine complexes.

METHODS

and results Here, we have analyzed the ability of histidylated polylysine to transfer reporter or CFTR genes into immortalized cystic fibrosis airway surface epithelial cells (sigmaCFTE29o- cells) and airway gland serous cells (CF-KM4 cells) which are both important targets for cystic fibrosis gene therapy. The luciferase reporter gene expression measured after gene transfer with histidylated polylysine into both cell lines was quite high and similar to that obtained with commercially available vectors. In addition, the level of expression was not dependent on the presence of a membrane disrupting agent such as chloroquine. Histidylated complexes were present in slightly acidic non-lysosomal cellular compartments as shown by a cytological approach using biotinylated plasmid, lysosome-specific antibodies and confocal microscopy. Histidylated complexes appeared to be of small size when prepared at low ionic strength and formed aggregates upon increasing the ionic strength. However, aggregate formation was prevented by the addition of 10% fetal bovine serum. Gene transfer efficiency varied with the size of the complexes and decreased when small particles were used.

CONCLUSIONS

These results suggest that histidylated polylysine may be an efficient non-viral vector for gene transfer into cystic fibrosis airway surface epithelial cells and airway gland serous cells.

Efficient gene transfer into human normal and cystic fibrosis tracheal gland serous cells with synthetic vectors

Submucosal gland serous cells are believed to play a major role in the physiopathology of cystic fibrosis (CF) and may represent an important target for CF gene therapy. We have studied the efficiency of reporter gene transfer into immortalized normal (MM-39) and CF (CF-KM4) human airway epithelial gland serous cells using various synthetic vectors: glycosylated polylysines (glycofectins), polyethylenimine (PEI) (25 and 800 kD), lipofectin, and lipofectAMINE. In both cell lines, a high luciferase activity was achieved with various glycofectins, with PEI 25 kD, and with lipofectAMINE. After three transfections applied daily using alpha-glycosylated polylysine, 20% of the cells were transfected. At 24 h after CF transmembrane conductance regulator (CFTR) gene transfer into CF-KM4 cells using alpha-glycosylated polylysine, the immunolocalization of CFTR was analyzed by laser scanning confocal microscopy and the transgenic CFTR was detected by an intense labeling of the plasma membrane. The presence of membrane lectins, i. e., cell surface receptors binding oligosaccharides, was also examined on MM-39 and CF-KM4 cells by assessing the binding and uptake of fluorescein-labeled neoglycoproteins and fluorescein-labeled glycoplexes (glycofectins complexed to plasmid DNA). Among all the neoglycoproteins and glycoplexes tested, those bearing alpha-mannosylated derivatives were most efficiently taken up by both normal and CF gland serous cells. However, alpha-mannosylated polylysine was quite inefficient for gene transfer, indicating that the efficiency of gene transfer is determined both by the uptake of the complexes and also by their intracellular trafficking. Moreover, our results show that an efficient in vitro gene transfer was achieved in human airway gland serous cells with the same synthetic vectors described to efficiently transfect human airway surface epithelial cells.

Histidylated oligolysines increase the transmembrane passage and the biological activity of antisense oligonucleotides

We have designed histidylated oligolysines which increase the uptake, the cytosolic delivery and the nuclear accumulation of antisense oligonucleotides (ODN). Flow cytometry analysis showed a 10-fold enhancement of the ODN uptake in the presence of histidylated oligolysines. The intracellular localizations of fluorescein-labeled ODN and of rhodamine-labeled histidylated oligolysines were investigated by confocal microscopy. Histidylated oligolysines favor the cyto-solic delivery of ODN from endosomes and increase their nuclear accumulation. In contrast, in their absence fluorescent ODN were not observed inside the nucleus but were distributed overwhelmingly within the vesicles in the cytosol. In addition, histidylated oligolysines yielded a more than 20-fold enhancement of the biological activity of antisense ODN towards the inhibition of transient as well as constitutive gene expression. Prevention of endosome lumen acidification using bafilomycin A(1)abolished the effect of histidylated oligolysines, suggesting that protonation of the histidyl residues was involved in the transmembrane passage of ODN.

Efficient gene transfer by histidylated polylysine/pDNA complexes

Plasmid/polylysine complexes, which are used to transfect mammalian cells, increase the uptake of DNA, but plasmid molecules are sequestered into vesicles where they cannot escape to reach the nuclear machinery. However, the transfection efficiency increases when membrane-disrupting reagents such as chloroquine or fusogenic peptides, are used to disrupt endosomal membranes and to favor the delivery of plasmid into the cytosol. We designed a cationic polymer that forms complexes with a plasmid DNA (pDNA) and mediates the transfection of various cell lines in the absence of chloroquine or fusogenic peptides. This polymer is a polylysine (average degree of polymerization of 190) partially substituted with histidyl residues which become cationic upon protonation of the imidazole groups at pH below 6.0. The transfection efficiency was optimal with a polylysine having 38 +/- 5% of the epsilon-amino groups substituted with histidyl residues; it was not significantly impaired in the presence of serum in the culture medium. The transfection was drastically inhibited in the presence of bafilomycin A1, indicating that the protonation of the imidazole groups in the endosome lumen might favor the delivery of pDNA into the cytosol.

Glycofection in the presence of anionic fusogenic peptides: a study of the parameters affecting the peptide-mediated enhancement of the transfection efficiency

Gene delivery mediated by polyplexes such as DNA complexed with polylysine conjugates is limited by the low efficiency of escape of DNA from the endosomes. One of the strategies which favors the transmembrane passage of polyplexes consists of adding anionic amphipathic peptides capable of destabilizing membranes in an acidic medium. Although less efficient than replication-defective adenoviruses, fusogenic peptides increase the expression of the reporter gene by a factor between 100 and 1000 depending on the cell line. However, the activity of a given peptide depends on the composition of the lipid bilayer. We were interested in developing a polyplex (glycoplex) formulation comprising a glycosylated polylysine, a fusogenic peptide and a plasmid which would be useful for efficient transfection (glycofection) of a large panel of cells, even in the presence of serum. We synthesized several peptides and tested their efficiency in combination with different glycoplex formulations. We found that glycofection with a quaternary complex (called one pot formulation) made of lactosylated-polylysine, polylysine, DNA, and the dimeric peptide (E5-WYGG)2-KA was less cell-type dependent than other peptide-based formulations. In addition, its efficiency was not affected by the presence of serum (up to 20%).

Sugar-mediated uptake of glycosylated polylysines and gene transfer into normal and cystic fibrosis airway epithelial cells

We have examined the membrane lectin expressed by immortalized normal and cystic fibrosis (CF) airway epithelial cells, using fluorescein-labeled neoglycoproteins; the uptake of plasmid DNA using fluoresceinylated glycoplexes (plasmid/glycosylated polylysine complexes); and the efficiency of gene transfer when glycosylated polylysines and glycosylated, partially gluconoylated polylysines were used as vectors. The most efficient uptake of neoglycoproteins by normal and CF cells was obtained with mannosylated BSA (bovine serum albumin). Similarly, the most efficient uptake of plasmid DNA was obtained with glycoplexes bearing alpha-D-Man residues. Surprisingly, glycoplexes bearing alpha-D-Man residues were poorly efficient for gene transfer into normal and CF cells. The highest luciferase activity was achieved with lactosylated polylysine- and beta-D-GlcNAc-substituted gluconoylated polylysine as vectors. Gene transfer efficiency obtained with gluconoylated polylysine bearing beta-D-GlcNAc residues was similar to that observed with polyethylenimine (PEI; 25 and 800 kDa) and 10-fold higher than that observed with lipofectin and LipofectAMINE. These results suggest that the transfection efficiency with glycoplexes is not determined only by the specificity of the lectin expressed at the cell surface membrane but also by intracellular trafficking of the glycoplexes, which could be mediated by lectins present inside the cells.

Novel glycosynthons for glycoconjugate preparation: oligosaccharylpyroglutamylanilide derivatives

The reducing sugar of an oligosaccharide reacting with the alpha-amino group of an amino acid is converted to an N-oligosaccharylamino acid which can then be stabilized by N-acylation. Oligosaccharides in solution in N,N-dimethylformamide reacted with alpha-glutamyl-p-nitroanilide at 50 degrees C for a few hours, leading to an N-oligosaccharylglutamyl-p-nitroanilide. Then, the gamma-carboxylic group of the glutamyl moiety, activated by adding (benzotriazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP), reacted with the substituted alpha-amino group of the glutamyl residue, leading to an N-oligosaccharylpyroglutamyl-p-nitroanilide within 0.5 h. Such a one-pot two-step reaction was shown to be very efficient in the case of a disaccharide such as lactose, or pentasaccharides such as lacto-N-fucopentaoses, Lewis(a) or Lewis(x). The glycosynthons were characterized by chromatography (HPAEC and HPLC); their molecular mass was determined by electrospray ionization mass spectrometry, and the glycosylamides were shown to have a beta-anomeric configuration on the basis of their proton NMR. The N-oligosaccharylpyroglutamyl-p-nitroanilides are quite stable at room temperature over a large pH range. They are easily converted to N-oligosaccharylpyroglutamyl-p-isothiocyanatoanilides which can be used to prepare glycoconjugates such as cationic glycosylated polylysines suitable for specifically delivering genes or oligonucleotides in a sugar-dependent manner.

Membrane permeabilization and efficient gene transfer by a peptide containing several histidines

We designed a peptide, H5WYG (GLFHAIAHFIHGGWHGLIHGWYG), that permeabilizes cell membrane at a slightly acidic pH but not at neutral pH. Absorbance, fluorescence, and circular dichroism spectra showed that H5WYG undergoes a dramatic conformational change between pH 7.0 and 6.0 that correlates with the protonation of the histidyl residues. Cell permeabilization studies monitored by flow cytometry on living cells showed that H5WYG permeabilizes the cell membrane with a great efficiency at pH 6.4 but was not active at neutral pH; at pH 6.8, the peptide permeabilized 50% of the cells at 20 degrees C within 10 min. H5WYG increased the expression of genes transferred to cells as glycosylated polylysine-DNA complexes, and the transfection efficiency was not impaired in the presence of serum. Therefore, this peptide containing several histidines that become positively charged when the pH decreased to less than 7.0 is a suitable helper for delivering molecules into the cytosol upon either permeabilization of the plasma membrane induced by lowering the extracellular medium to pH 6.4 or permeabilization of the endosomal membrane induced by acidification of endosomes.

The reduction of the positive charges of polylysine by partial gluconoylation increases the transfection efficiency of polylysine/DNA complexes

A polylysine partially substituted with polyhydroxyalkanoyl residues and specially with gluconoyl residues was developed in order to increase the transfection efficiency by decreasing the strength of the electrostatic interactions between the DNA and the cationic polymer. Partially gluconoylated polylysine/DNA complexes were more easily dissociated in solution and their transfection efficiency in the presence of chloroquine, evaluated with HepG2 cells, a human hepatocarcinoma line, was higher when 43 +/- 4% of the epsilon-amino groups of polylysine were blocked with gluconoyl residues. Partially gluconoylated polylysine/plasmid complexes were efficient in transfecting different adherent as well as non-adherent cell lines. Partially gluconoylated polylysine formed highly soluble (above 100 micrograms/ml in DNA) complexes with DNA plasmids. In addition, partially gluconoylated polylysine bearing few lactosyl residues increased the transfection efficiency of HepG2 cells which express a galactose-specific membrane lectin.

Lysine-based cluster mannosides that inhibit ligand binding to the human mannose receptor at nanomolar concentration

In search of synthetic high affinity ligands for the mannose receptor, we synthesized a series of lysine-based oligomannosides containing two (M2L) to six (M6L5) terminal alpha-D-mannose groups that are connected with the backbone by flexible elongated spacers (16 A). The synthesized cluster mannosides were all able to displace binding of biotinylated ribonuclease B and tissue-type plasminogen activator to isolated human mannose receptor. The affinity of these cluster mannosides for the mannose receptor was continuously enhanced from 18-23 microM to 0.5-2.6 nM, with mannose valencies increasing from two to six. On average, expansion of the cluster mannoside with an additional alpha-D-mannose group resulted in a 10-fold increase in its affinity for the mannose receptor. M3L2 to M6L5 displayed negative cooperative inhibition of ligand binding to the mannose receptor, suggesting that binding of these mannosides involves multiple binding sites. The nanomolar affinity of the most potent ligand, the hexamannoside M6L5 makes it the most potent synthetic cluster mannoside for the mannose receptor yet developed. As a result of its high affinity and accessible synthesis, M6L5 not only is a powerful tool to study the mechanism of ligand binding by the mannose receptor, but it is also a promising targeting device to accomplish cell-specific delivery of genes and drugs to liver endothelial cells or macrophages in bone marrow, lungs, spleen, and atherosclerotic plaques.

Gluconoylated and glycosylated polylysines as vectors for gene transfer into cystic fibrosis airway epithelial cells

To provide an alternative to viral vectors for the transfer of genes into airway epithelial cells in cystic fibrosis (CF), a novel set of substituted polylysines were employed. Polylysine was partially neutralized by blocking a number of positively charged residues with gluconoyl groups. In addition, polylysine was substituted with sugar residues on a specified number of amino groups. Using the gluconoylated polylysine as vector, the pCMVLuc plasmid gave high expression of the reporter gene luciferase in immortalized CF/T43 cells. The luciferase activity was 75-fold greater in the presence of 100 microM chloroquine. Luciferase gene expression persisted at high levels for up to at least 120 hr following transfection. Glycosylated polylysines/pCMVLuc complexes were compared to the gluconoylated polylysine/pCMVLuc complex and beta-Gal-, alpha-Glc-, and Lac-substituted polylysines gave 320%, 300%, and 290%, respectively, higher expression of the reporter gene luciferase. Luciferase expression ranged from 35 to 2 ng of luciferase per milligram of cell protein in the order: beta-Gal = alpha-Glc = Lac > alpha-Gal = Rha = Man > beta-GalNAc > alpha-GalNAc = alpha-Fuc, suggesting that the transfection efficiency is sugar dependent. Most importantly, in primary cultures of both CF and non-CF airway epithelial cells grown from tracheal tissue explants, lactosylated polylysine gave uniformly high expression of luciferase. The glycosylated polylysines provide an attractive nonviral approach for the transfer of genes into airway epithelial cells.

Gene transfer by DNA/glycosylated polylysine complexes into human blood monocyte-derived macrophages

Macrophages are putative target cells for expressing an exogenous gene with therapeutical effects. Knowing that macrophages express membrane lectins mediating endocytosis of their ligands, DNA/glycosylated polylysine complexes were used to transfect human blood monocyte-derived macrophages. Monocytes from human peripheral blood were matured in culture for 7 days to differentiate into macrophage-like cells in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF). Adherent cells, which displayed characteristic macrophage markers, CD 14, CD 11b, HLA-DR, and HLA-ABC antigens and mannose receptor, were transfected by DNA/glycosylated polylysine complexes in the presence of chloroquine. The luciferase reporter gene expression was maximal 24 hr after transfection with a DNA/mannosylated polylysine complex and by using plasmids in which the promoters (either the long terminal repeat of the human immunodeficiency virus or the human cytomegalovirus) drove the luciferase gene expression. Luciferase gene expression was lower when the promoter was the early region of the large T antigen of SV40 virus. Transfection mediated by DNA/mannosylated polylysine complexes was much more efficient than with DEAE-dextran or lipofectin. The possibility of transferring and expressing an exogenous gene into macrophage-like cells by using a nonimmunogenic synthetic vector as a DNA carrier opens new ways to develop nonviral gene therapy strategies.

Internalization of human macrophage surface antigens induced by monoclonal antibodies

Drugs intended to be endocytosed by macrophages may be transported by MAbs directed against these cells. Twenty MAbs were investigated for this purpose. The binding of these MAbs to macrophages obtained from a 7 day culture of blood monocytes showed that anti-CD11b and anti-CD14 recognized the highest number of cell surface antigen sites. Further assays determined that anti-CD63, Mo5 and anti-CD33 were the MAbs that induced the strongest modulation of the corresponding antigens, the highest rate being with anti-CD63. Endocytosis of antigen-antibody complexes was evidenced by the presence of MAbs in the cytoplasm. Anti-CD63 MAbs induced the highest internalization in this assay. For most MAbs, however, the density of antigen sites and the intensity of antigen modulation were not predictive of the amount of MAb detected in the cytoplasm.

Receptor mediated glycotargeting

Glycotargeting relies on carrier molecules possessing carbohydrates that are recognized and internalized by cell surface mammalian lectins. Numerous types of glycotargeting vehicles have been designed based on the covalent attachment of saccharides to proteins, polymers and other aglycones. These carriers have found their major applications in antiviral therapy, immunoactivation, enzyme replacement therapy and gene therapy. This review compared different types of glycotargeting agents and the lectins which have been successfully targeted to treat both model and human diseases. It may be concluded that the discovery of new mammalian lectins which endocytose their ligands will lead to the rapid development of new glycotargeting agents founded on the principles of carbohydrate-protein interactions.

A conjugate of lactosaminated poly-L-lysine with adenine arabinoside monophosphate, administered to mice by intramuscular route, accomplishes a selective delivery of the drug to the liver

A conjugate of the antiviral agent adenine arabinoside monophosphate (ara-AMP) with a low molecular mass lactosaminated poly-L-lysine, administered to mice by i.m. route, selectively delivers the drug to the liver. In mice the conjugate is devoid of acute toxicity even at high dose (1.3 mg/g) and injected i.m. for 20 days does not induce antibodies. Moreover it is highly soluble in water; this means that a pharmacologically active dose may be administered in a small volume compatible with the i.m. route. Compared to the similar ara-AMP complex with lactosaminated albumin which must be injected intravenously, the present conjugate might assure a better compliance of patients with hepatitis B virus infection for a long lasting, liver targeted antiviral treatment.

Purification of an alpha-L-fucoside-binding protein from Rhizobium lupini

Lectins associated with the bacterial cell surface of Rhizobium lupini strain LL13 were evidenced by erythrocyte agglutination, by aggregation of neoglycoprotein coated beads and by spectrofluorimetry using fluoresceinylated neoglycoproteins. At pH 5.0, a specific binding of the fluorescein-labelled neoglycoprotein bearing alpha-L-fucose was observed. The binding of this labelled neoglycoprotein is a saturable phenomenon and is inhibited by the same unlabelled neoglycoprotein. Extracts of R lupini obtained by disrupting a bacterial pellet through a French press were stabilized at pH 5.6 by gel filtration and purified to homogeneity by affinity chromatography on Agarose A4 substituted with alpha-L-fucose. A protein with a M(r) approximately 19,000 was specifically eluted from this affinity column with L-fucose. Isoelectric focusing of this sample yielded a single band with pI near 6.7. This protein specifically aggregated L-Fuc-BSA-coated microspheres. The results obtained in the present study indicate that we have purified from Rhizobium lupini strain LL13, a L-fucose binding protein as a lectin.

Dye-hydrophobic hapten conjugate/anti-dye antibody complex as immunogen: preparation of hydrophobic hapten-specific monoclonal antibodies

In order to induce the production of antibodies specific for small molecules, it is common to link them to a protein. However, when the small molecule is very hydrophobic it is extremely difficult to prepare such a conjugate. Here, we describe a simple way to obtain an antigenic conjugate under controlled conditions: in a first step a very hydrophobic hapten, cholanic acid, is linked to a dye, basilen blue, in organic solvent; in a second step the cholanic acid-basilen blue conjugate is dissolved in phosphate buffered saline and mixed with rabbit polyclonal anti-basilen blue antibodies previously raised in rabbits against basilen blue-key-hole limpet hemocyanin conjugate. Such a complex, which dissociates very slowly, appears to be a good immunogen in mice. Anti-cholanyl residue monoclonal antibodies were produced and characterized.

Sensitive, hydrosoluble, macromolecular fluorogenic substrates for human immunodeficiency virus 1 proteinase

Hydrosoluble macromolecular fluorogenic substrates specific for the human immunodeficiency virus 1 (HIV-1) proteinase have been prepared. The fluoresceinyl peptide Ftc-epsilon-Ahx-Ser-Phe-Asn-Phe-Pro-Gln-Ile-Thr-(Gly)n, corresponding to the first cleavage site of HIV-1 gag-pol native precursor was linked to a water-soluble neutral (Lys)n derivative. The epsilon-aminohexanoyl residue (epsilon-Ahx) and the glycyl sequence were added in order to improve the stability of the substrate and the accessibility of the cleavage site to the HIV-1 proteinase respectively. This macro-molecular peptidic-substrate conjugate is significantly more water-soluble than the free peptide itself on a substrate molar concentration basis. The assay is based on the quantitative precipitation of the polymeric material by adding propan-2-ol whereas the fluorescent peptide moiety released upon proteolysis remains soluble in the supernatant. The proteinase activity is assessed by measuring the fluorescence of the supernatant. This assay allows the detection of a few fmol of HIV-1 proteinase, even in the presence of cell culture media, plasma or cell lysate and it gives accurate results within a large proteinase concentration range. The hydrosoluble macromolecular substrate is also suitable for determining the HIV-1 proteinase activity using 96-well microplates, allowing us to test accurately and rapidly numerous enzyme samples and/or the potency of new proteinase inhibitors.

Specific gene transfer mediated by lactosylated poly-L-lysine into hepatoma cells

Plasmid DNA/glycosylated polylysine complexes were used to transfer in vitro a luciferase reporter gene into human hepatoma cells by a receptor-mediated endocytosis process. HepG2 cells which express a galactose specific membrane lectin were efficiently and selectively transfected with pSV2Luc/lactosylated polylysine complexes in a sugar dependent manner: i) HepG2 cells which do not express membrane lectin specific for mannose were quite poorly transfected with pSV2Luc/mannosylated polylysine complexes, ii) HeLa cells which do not express membrane lectin specific for galactose were not transfected with pSV2Luc/lactosylated polylysine complexes. The transfection efficiency of HepG2 cells with pSV2Luc/lactosylated polylysine complexes was greatly enhanced either in the presence of chloroquine or in the presence of a fusogenic peptide. A 22-residue peptide derived from the influenza virus hemagglutinin HA2 N-terminal polypeptide that mimics the fusogenic activity of the virus, was selected. In the presence of the fusogenic peptide, the luciferase activity in HepG2 cells was 10 fold larger than that of cells transfected with pSV2Luc/lactosylated polylysine complexes in the presence of chloroquine.

Antileishmanial drug targeting through glycosylated polymers specifically internalized by macrophage membrane lectins

Antileishmanial chemotherapy is hampered by the location of the parasite within the phagolysosome of the macrophage, which restricts the bioavailability of many potentially useful antileishmanial drugs. In this study, the possibility of using antileishmanial drugs targeted to the infected macrophages by means of a chemical linkage to a neutral mannose-substituted poly-L-lysine carrier molecule was explored. The study was performed in an in vitro model with Leishmania donovani-infected murine macrophages. The antileishmanial activities of various synthetic constructs were compared with those of the free drugs and the pentavalent antimonial Pentostam, which was used as the positive control. The 50% effective dose of allopurinol riboside linked to the mannosylated poly-L-lysine was below 7.5 x 10(-6) M, while it was up to 3 x 10(-4) M for the free drug, indicating that the drug bound to the polymer was 50 times more active than the free drug. Control experiments with other constructs (e.g., allopurinol riboside linked to the mannose-free polymer) confirmed that the enhancement of activity was indeed achieved by means of the mannose homing device.

Drug targeting: synthesis and endocytosis of oligonucleotide-neoglycoprotein conjugates

Inhibition of gene expression by antisense oligonucleotides is limited by their low ability to enter cells. Knowing that sugar binding receptors, also called membrane lectins, efficiently internalize neoglycoproteins bearing the relevant sugar, 6-phosphomannose, for instance, oligonucleotides--substituted on their 5'-end with either a fluorescent probe or a radioactive label on the one hand, and bearing a thiol function on their 3'-end, on the other hand,--were coupled onto 6-phosphomannosylated proteins via a disulfide bridge. The oligonucleotide bound to 6-phosphomannosylated serum albumin is much more efficiently internalized roughly 20 times than the free oligonucleotide. Although most of the oligonucleotides are associated with vesicular compartments, oligonucleotides after releasing from the carrier by reduction of the disulfide bridge may find their way to reach the cytosol and then lead to an increase in the efficiency of the oligonucleotides.

Water-soluble macromolecular fluorogenic substrates for assaying proteinases: determination of pancreatic elastase activity

Water-soluble macromolecular fluorogenic substrates were synthesized in order to develop an easy specific proteinase assay. The validity of this method was tested with porcine pancreatic elastase by using its specific peptidic substrate Ala-Ala-Pro-Ala linked to a hydrosoluble polymer. The octapeptidic sequence FTC-epsilon Aca-Ala-Ala-Pro-Ala-Gly-Gly-Gly was linked to a water-soluble and neutral poly-L-lysine derivative. The aminocaproyl residue and the triglycyl sequence were added in order to improve the stability of the substrate, and the accessibility of the specific sequence Ala-Ala-Pro-Ala to elastase, respectively. The assay is based on the quantitative precipitation of the polymeric substrate in isopropanol while the released soluble fluorescent peptidic moiety is fluorometrically titrated in the supernatant.

Drug targeting: anti-HSV-1 activity of mannosylated polymer-bound 9-(2-phosphonylmethoxyethyl)adenine

The antiviral drug, 9-(2-phosphonylmethoxyethyl) adenine (PMEA) was linked to a synthetic and neutral polymer bearing mannosyl residues to allow its internalization by macrophages via membrane lectins. PMEA bound to the mannosylated polymer was more efficient in vitro than free PMEA in preventing lysis of human macrophages by herpes virus.

Endocytosis mediated by monocyte and macrophage membrane lectins--application to antiviral drug targeting

Sugar receptors, or membrane lectins, have been evidenced at the surface of various normal and tumour cells using fluoresceinylated neoglycoproteins (glycosylated bovine serum albumin (BSA]. By flow cytometry we have shown that macrophages bind and internalize mannosylated and 6-phosphomannosylated ligands in acidic compartments. Freshly isolated monocytes and U937, a promonocytic cell line, lack a mannose-specific receptor, but express mannose-6-phosphate (Man-6P) membrane lectin. Neoglycoproteins are potent drug carriers: muramyl dipeptide (MDP), an immunoactivator, when bound to Man-BSA or Man-6P-BSA, is 100 times more efficient than free MDP in activating macrophages; in vivo, it enables eradication of lung metastases in mice. Recently, neutral glycosylated biodegradable and nonimmunogenic polymers, were synthesized and found to be as efficient as neoglycoproteins. Antiviral drug conjugates were more active than the free drug, inhibiting the multiplication of virus (herpes) in human macrophages in vitro.