Targeting of poly(rI)-poly(rC) by fusogenic (F protein) immunoliposomes

Development of Drugs Based on High-Polymeric Double-Stranded RNA for Antiviral and Antitumor Therapy

Abstract-The review summarizes literature data on the development of drugs based on natural and synthetic high-polymeric double-stranded RNA (dsRNA), their antiviral, immunoadjuvant, and antitumor properties. Special attention is paid to cell receptors responding to exogenous dsRNA, pathways of dsRNA-dependent antiviral reaction, ability of dsRNA to inhibit growth and induce apoptosis of malignant cells. It has been shown that enhancing the innate immune response with dsRNA can be an effective component in improving methods for treating and preventing infectious and cancer diseases. The further use of dsRNA for the correction of pathological processes of different origin is discussed.

[Development of drugs on the basis of high-polymeric double-stranded RNA for antiviral and antitumor therapy]

The review summarizes literature data on the development of drugs based on natural and synthetic high-polymeric double-stranded RNA, and their antiviral, immunoadjuvant and antitumor properties. Special attention is paid to cell receptors responding to exogenous dsRNA, the paths of dsRNA-dependent antiviral reaction, ability of dsRNA to inhibit growth and induce apoptosis ofmalignant cells. It has been shown that enhancing the innate immune response with dsRNA can be an effective component in improving methods for treating and preventing infectious and cancer diseases. The further use of dsRNA for the correction of pathological processes of different origin is discussed.

Delivery systems for antisense oligonucleotides

In vitro, the efficacy of the antisense approach is strongly increased by systems delivering oligodeoxyribonucleotides (ODNs) to cells. Up to now, most of the developed vectors favor ODN entrance by a mechanism based on endocytosis. Such is the case for particulate systems, including liposomes (cationic or non-cationic), cationic polyelectrolytes, and delivery systems targeted to specific receptors. Under these conditions, endosomal compartments may represent a dead end for ODNs. Current research attempts to develop conditions for escaping from these compartments. A new class of vectors acts by passive permeabilization of the plasma membrane. It includes peptides, streptolysin O, and cationic derivatives of polyene antibiotics. In vivo, the interest of a delivery system, up to now, has appeared limited. Development of vectors insensitive to the presence of serum seems to be a prerequisite for future improvements.

A cationic derivative of amphotericin B as a novel delivery system for antisense oligonucleotides

A novel approach based on a plasma membrane permeability-disturbing agent was proposed as an antisense oligonucleotide delivery system. AMA, a derivative of the polyene antibiotic amphotericin B, formed a stable complex when mixed with phosphodiester oligodeoxynucleotides and enhanced the intracellular uptake of a 5' fluoresceinated anti-mdr1 20-mer into NIH-MDR-G185 cells. The nonlabeled phosphorothioate form of the oligodeoxynucleotide, complexed to AMA, inhibited P-glycoprotein expression with better efficiency and less nonspecific effects than when vectorized by Lipofectin. AMA may thus be a good agent for antisense strategy.

Liposomes as drug delivery system: a strategic approach for the treatment of HIV infection

As the number of individuals infected with human immunodeficiency virus (HIV) is growing dramatically throughout the world, it is important to develop strategies to improve the treatment of this deadly disease. It is now well established that macrophages play a central role in HIV pathogenesis, acting as reservoirs for dissemination of virus throughout the immune system. As liposomes are naturally taken up by cells of the mononuclear phagocytic system, liposome-based therapy represents a convenient approach to improve the delivery of anti-HIV agents into infected cells improving thereby the efficacy of drugs and reducing their adverse side-effects. A more specific targeting of HIV-infected cells could also be obtained by using liposomes bearing surface attached-antibodies. This review details the applications of liposomes as drug carriers for the treatment of AIDS. It also gives an overlook of the different strategies that could be explored to control the progression of the disease in infected individuals.

Recent advances in liposome technologies and their applications for systemic gene delivery

The recent clinical successes experienced by liposomal drug delivery systems stem from the ability to produce well-defined liposomes that can be composed of a wide variety of lipids, have high drug-trapping efficiencies and have a narrow size distribution, averaging less than 100 nm in diameter. Agents that prolong the circulation lifetime of liposomes, enhance the delivery of liposomal drugs to specific target cells, or enhance the ability of liposomes to deliver drugs intracellularly can be incorporated to further increase the therapeutic activity. The physical and chemical requirements for optimum liposome drug delivery systems will likely apply to lipid-based gene delivery systems. As a result, the development of liposomal delivery systems for systemic gene delivery should follow similar strategies.

Cellular delivery of oligonucleotides by synthetic import peptide carrier

PURPOSE

Inefficient cellular uptake and endosomal entrapment are among the obstacles impeding the therapeutic use of oligonucleotides (ONs). The objectives of this study are to investigate the feasibility of utilizing a synthetic import peptide as a drug carrier for cytoplasmic delivery of ONs and to study its transport mechanisms.

METHODS

A molecular conjugate consisting of a signal import peptide (IP) derived from Kaposi fibroblast growth factor (K-FGF) and a polycationic ON linker, polylysine (PL), was synthesized and complexed with 5' fluorescently-labeled ON. Complex formation was verified by spectral shift assay and cellular uptake of the ON complex was studied fluorometrically. Microscopic studies were performed to visualize the intracellular distribution of the ON.

RESULTS

Cells treated with the ON:IP-PL complex exhibited a dose-dependent increase in ON uptake over free ON-treated controls. The uptake of the complex was shown to occur via an energy-independent, non-endocytic, process since metabolic and endocytic inhibitors and low temperature did not prevent the uptake. Microscopic studies revealed a non-punctate fluorescence pattern, consistent with the non-endocytic transport process. Intense nuclear fluorescence was observed in cells treated with the complex but not with free ON, suggesting enhanced cytoplasmic delivery and nuclear accumulation of the ON by the conjugate. Efficient complex uptake was shown to require both the ON-binding moiety PL and the IP moiety. The delivery system was found to be non-toxic at the concentrations used.

CONCLUSIONS

The peptide carrier was effective in promoting the cellular uptake of ON. The mechanism by which the peptide facilitates ON uptake appears to involve a direct translocation of ON via a non-endocytic process. The peptide carrier has the potential to overcome the problem of ON endosomal entrapment and degradation.

Improved biological activity of antisense oligonucleotides conjugated to a fusogenic peptide

Recently several groups reported a dramatic improvement of reporter gene transfection efficiency using a fusogenic peptide, derived from the Influenza hemagglutinin envelop protein. This peptide changes conformation at acidic pH and destabilizes the endosomal membranes thus resulting in an increased cytoplasmic gene delivery. We describe the use of a similar fusogenic peptide in order to improve the antiviral potency of antisense oligodeoxynucleotides (anti TAT) and oligophosphorothioates (S-dC28) on de novo HIV infected CEM-SS lymphocytes in serum-free medium. We observed as 5 to 10 fold improvement of the anti HIV activities of the phosphodiester antisense oligonucleotides after chemical coupling to the peptide in a one to one ratio by a disulfide or thioether bond. No toxicities were observed at the effective doses (0.1-1 microM). No sequence specificity was obtained and the fusogenic peptide possessed some antiviral activities on its own (IC50: 6 microM). A S-dC28-peptide disulfide linked conjugate and a streptavidin-peptide-biotinylated S-dC28 adduct showed similar activities as the free S-dC28 oligonucleotide (IC50: 0.1-1 nM). As expected, all the compounds were less potent in the presence of serum but the relative contribution of peptide coupling was maintained.

Design of a short membrane-destabilizing peptide covalently bound to liposomes

We characterized the physical and biological properties of a 14-residue amphipathic sequence called SFP (for short fusogenic peptide). At acidic pH, this short synthetic peptide interacts with various phospholipidic monolayers. These interactions were correlated with a pH-dependent conformational transition of SFP resulting in a hydrophobic alpha-helical structure. The hemolysis assay showed a pH-dependent weak membrane destabilizing activity of SFP. However, membrane anchoring of SFP through a covalently bound myristic acid enhanced by 1000-fold its membrane-destabilizing power. Moreover, SFP covalently bound to fluorescent-labeled liposomes induced a pH-dependent mixing of both membranes. SFP, a small synthetic peptide, is thus able to mimick many aspects of viral protein-induced membrane fusion: conformational change, membrane destabilization, membrane anchoring and finally pH-dependent lipid mixing.