Rumiko Moriguchi

Reprint of: Nanoparticles for ex vivo siRNA delivery to dendritic cells for cancer vaccines: Programmed endosomal escape and dissociation

We previously developed octaarginine (R8)-modified lipid envelope-type nanoparticles for siRNA delivery (R8-MEND). Herein, we report on their ex vivo siRNA delivery to primary mouse bone marrow-derived dendritic cells (BMDCs) for potential use as a cancer vaccine. Quantitative imaging analysis of the intracellular trafficking of siRNA revealed that the dissociation process, as well as the rate of endosomal escape limits the siRNA efficiency of the prototype R8-MEND, prepared by the hydration method (R8-MEND(hydo)). Successful endosomal escape was achieved by using a pH-dependent fusogenic peptide (GALA) modified on a lipid mixture that was optimized for endosomal fusion. Furthermore, a modified protocol for the preparation of nanoparticles, mixing the siRNA/STR-R8 complex and small unilamellar vesicles (R8/GALA-MEND(SUV)), results in a more homogenous, smaller particle size, and results in a more efficient intracellular dissociation. Gene knockdown of the suppressor of cytokine signaling 1 (SOCS1), a negative-feedback regulator of the immune response in BMDCs resulted in an enhanced phosphorylation of STAT1, and the production of proinflammatory cytokines. Moreover, SOCS1-silenced BMDCs were more potent in suppressing tumor growth. Collectively, these results show that siRNA loaded in R8/GALA-MEND(SUV) efficiently suppresses endogenous gene expression and consequently enhances dendritic cell-based vaccine potency in vivo.

Multi-layered nanoparticles for penetrating the endosome and nuclear membrane via a step-wise membrane fusion process.

Efficient targeting of DNA to the nucleus is a prerequisite for effective gene therapy. The gene-delivery vehicle must penetrate through the plasma membrane, and the DNA-impermeable double-membraned nuclear envelope, and deposit its DNA cargo in a form ready for transcription. Here we introduce a concept for overcoming intracellular membrane barriers that involves step-wise membrane fusion. To achieve this, a nanotechnology was developed that creates a multi-layered nanoparticle, which we refer to as a Tetra-lamellar Multi-functional Envelope-type Nano Device (T-MEND). The critical structural elements of the T-MEND are a DNA-polycation condensed core coated with two nuclear membrane-fusogenic inner envelopes and two endosome-fusogenic outer envelopes, which are shed in stepwise fashion. A double-lamellar membrane structure is required for nuclear delivery via the stepwise fusion of double layered nuclear membrane structure. Intracellular membrane fusions to endosomes and nuclear membranes were verified by spectral imaging of fluorescence resonance energy transfer (FRET) between donor and acceptor fluorophores that had been dually labeled on the liposome surface. Coating the core with the minimum number of nucleus-fusogenic lipid envelopes (i.e., 2) is essential to facilitate transcription. As a result, the T-MEND achieves dramatic levels of transgene expression in non-dividing cells.

An artificial virus-like nano carrier system: enhanced endosomal escape of nanoparticles via synergistic action of pH-sensitive fusogenic peptide derivatives

We previously reported that transferrin (Tf)-modified liposomes (Tf-L) additionally modified with a cholesterylated pH-sensitive fusogenic peptide (Chol-GALA) can release an encapsulated aqueous phase marker to cytosol via endosomal membrane fusion. However, further obstacles need to be overcome to bring the Tf-L to the level of a viral-like gene delivery system. In this study, we developed a novel packaging method to encapsulate condensed plasmid DNA into PEgylated Tf-L (Tf-PEG-L) to form a core–shell-type nanoparticle. The most difficult challenge was to provide a mechanism of escape for the condensed core from endosome to cytosol in the presence of polyethylene glycol (PEG). We hypothesized that a membrane-introduced Chol-GALA and a PEgylated GALA would interact synergistically to induce membrane fusion between liposome and endosome. By simultaneously incorporating Chol-GALA into the membrane of Tf-PEG-L and GALA at tips of PEG chains, a condensed core was released into cytosol, and transfection acitivty increased 100-fold. We concluded that topological control was responsible for the synergistic effect of GALA derivatives introduced on Tf-PEG-L.

Efficient MHC Class I Presentation by Controlled Intracellular Trafficking of Antigens in Octaarginine-modified Liposomes

Recently, much attention has been paid to cell-penetrating peptides (CPPs) as an antigen-delivery tool for presentation through the major histocompatibility complex class I (MHC-I) pathway. However, escape of CPPs from the endosome is inefficient and therefore a bottleneck for antigen delivery. Previously, we showed the importance of topological control of octaarginine (R8) peptides on the liposome surface for regulating cellular uptake as well as intracellular trafficking, especially endosomal escape. In this study, we hypothesized that efficient MHC-I presentation could be achieved by controlled intracellular trafficking of antigen encapsulated in R8-modified liposomes (R8-Lip). The mechanism of uptake of both R8-Lip and cationic liposomes was shown to be by macropinocytosis in dendritic cells. However, confocal laser scanning microscopy (CLSM) revealed that R8-Lip are able to release significantly more antigen to the cytosol than are cationic liposomes. Processing of the antigens delivered by R8-Lip was shown to be proteasome-dependent, which is consistent with selective antigen presentation by R8-Lip via MHC-I. According to antigen-presentation analysis, R8-Lip can induce significantly higher MHC-I presentation at lower doses than either soluble ovalbumin (OVA) or OVA in pH-sensitive or cationic liposomes. Moreover, R8-Lip showed an efficient antitumor effect in vivo. Therefore, R8-Lip is a promising new carrier for MHC-I-specific antigen presentation.

Incorporation of polyinosine-polycytidylic acid enhances cytotoxic T cell activity and antitumor effects by octaarginine-modified liposomes encapsulating antigen, but not by octaarginine-modified antigen complex.

In a previous study, we reported on the efficient delivery of an antigen to the cytosol and a specific-antigen presentation on MHC class I in dendritic cells by rationally controlling the intracellular trafficking of ovalbumin (OVA), a model antigen, with stearylated octaarginine-modified liposomes (R8-Lip/OVA). However, no significant difference in antitumor effects against E.G7-OVA, OVA expressed lymphoma, was observed between R8-Lip/OVA and an electrostatic complex of R8 and OVA (R8/OVA-Com). In this study, we hypothesized that use of adjuvants clarified the difference in immune responses between R8-Lip/OVA and R8/OVA-Com, and selected polyinosine-polycytidylic acid (polyI:C) as an adjuvant. Cytotoxic T lymphocyte (CTL) activity of the polyI:C and OVA encapsulated R8-Lip (R8-Lip/PIC/OVA) was drastically enhanced compared to R8-Lip/OVA and complete Freunds adjuvant with OVA. Moreover, the incorporation of polyI:C clearly was critical for the difference in antitumor effects and CTL activities between R8-Lip/OVA and R8/OVA-Com. These findings suggest that the carriers that are incorporated polyI:C has a great influence on the induction of cellular immunity in vivo.

Octaarginine-modified liposomes enhance cross-presentation by promoting the C-terminal trimming of antigen peptide.

Exogenous antigen proteolysis by proteasomes and amino peptidases is essential for the production of mature major histocompatibility complex class I (MHC-I) peptides to induce cross-presentation. We report here that when liposomes are modified with octaarginine (R8-Lip), a type of cell-penetrating peptide, the production of the mature MHC-I peptide is enhanced by promoting the C-terminal trimming of the antigen peptide. The efficiency of cross-presentation of ovalbumin (OVA) using the R8-Lip was dramatically higher than that by octalysine modified liposomes (K8-Lip) in mouse bone-marrow derived dendritic cells (BMDCs), although the physical characters of both liposomes were comparable. In this study, we investigated the mechanism responsible for the enhancement in cross-presentation by R8-Lip. Although the efficiencies of cellular uptake, endosomal escape, proteolysis of OVA and DC maturation between the two systems were essentially the same, an analysis of peptide trimming to SIINFEKL (mature MHC-I peptide of OVA) by using R8-Lip and K8-Lip encapsulating peptides of various length clearly indicates that the use of R8-Lip enhances the efficiency of the C-terminal cleavage of antigen-derived peptides. This finding provides a new strategy for achieving efficient cross-presentation by using R8 peptide and arginine-rich peptides. Moreover, this result may contribute to the development of a new paradigm regarding the machinery associated with antigen peptide production.

Non-linear pharmacodynamics in the transfection efficiency of a non-viral gene delivery system

Transfection efficiencies using LipofectAMINE varied by more than three orders of magnitude depending on the concentrations of lipid and plasmid DNA (pDNA) used to prepare the lipoplexes. When lipoplexes were formed at lower concentrations a striking positive but non-linear relationship was found between dose and transfection efficiency, while at higher (i.e., normally used) concentrations a linear relationship was maintained. To determine the contribution of intracellular pharmacokinetics (PK) and pharmacodynamics (PD) to the observed nonlinearity, we quantified pDNA in whole cells and nuclei by real-time PCR and compared the results with the transfection efficiencies. There was no significant difference in the efficiency of intracellular PK; however, a remarkable difference was observed in the efficiency of PD. Analysis of individual cells by confocal laser scanning microscopy (CLSM) revealed that the amount of nuclear-delivered pDNA was higher for lipoplexes prepared at the normal concentration (NCL) compared to those of lipoplexes prepared at low concentration (LCL). Moreover, the size of the NCL was larger than that of the LCL. Both the size of the lipoplex particle and the dose appear to contribute to the non-linear efficiency of PD. These results emphasize the need to control not only intracellular PK, but also PD for the rational development of non-viral gene delivery systems.

581. Development of a Non-Viral DNA Vector Multifunctional Envelop-type Nano Device Modified with Octaarginine Peptide

For efficient gene delivery to the nucleus, non-viral vectors need to overcome several barriers such as the plasma membrane, the endosomal membrane and the nuclear membrane. To overcome these obstacles, it is necessary to equip the delivery system with various functional devices [Kamiya H., et al., Drug Discov. Today 21 (2003) 990]. However, it is difficult to package all these functional devices into a single system to exert each of their functions at the appropriate time and at the correct location. Thus, we proposed a new packaging concept, |[ldquo]|Programmed Packaging|[rdquo]|. This concept consists of three components: (1) A program to overcome all barriers. (2) Development of functional devices and their three dimensional assignment. (3) Nano-technology for assembling all devices into a nano-size structure.