T cell-specific siRNA delivery suppresses HIV-1 infection in humanized mice

RNA Interference as a Prospective Tool for the Control of Human Viral Infections

RNA interference (RNAi), which is mediated by small interfering RNAs (siRNAs) derived from viral genome or its replicative intermediates, is a natural antiviral defense in plants, fungi, and invertebrates. Whether RNAi naturally protects humans from viral invasion is still a matter of debate. Nevertheless, exogenous siRNAs are able to halt viral infection in mammals. The current review critically evaluates the production of antiviral siRNAs, delivery techniques to the infection sites, as well as provides an overview of antiviral siRNAs in clinical trials.

Regulation of T Follicular Helper Cells in Islet Autoimmunity

T follicular helper (TFH) cells are an integral part of humoral immunity by providing help to B cells to produce high-affinity antibodies. The TFH precursor compartment circulates in the blood and TFH cell dysregulation is implied in various autoimmune diseases including type 1 diabetes (T1D). Symptomatic T1D is preceded by a preclinical phase (indicated by the presence of islet autoantibodies) with a highly variable progression time to the symptomatic disease. This heterogeneity points toward differences in immune activation in children with a fast versus slow progressor phenotype. In the context of T1D, previous studies on TFH cells have mainly focused on the clinically active state of the disease. In this review article, we aim to specifically discuss recent insights on TFH cells in human islet autoimmunity before the onset of symptomatic T1D. Furthermore, we will highlight advances in the field of TFH differentiation and function during human islet autoimmunity. Specifically, we will focus on the regulation of TFH cells by microRNAs (miRNAs), as well as on the potential use of miRNAs as biomarkers to predict disease progression time and as future drug targets to interfere with autoimmune activation.

Cell-penetrating peptides for siRNA delivery to glioblastomas

Delivery of small interfering RNA (siRNA) to suppress glioblastoma growth is a hurdle due to the critical obstacles of the blood-brain barrier and the siRNA properties of such as high negative charges and instability in serum. Therefore, the passage of siRNA to targeted cells is limited. Several siRNA carriers have been constructed using cell-penetrating peptides (CPPs) since the CPPs have shown a high potential for oligonucleotide delivery into the cells. In this study, two CPPs, PepFect 14 (PF14) and the amphipathic peptide PepFect 28 (PF28), were modified with targeting peptides by covalent conjugation and non-covalent complex formation to improve glioma-targeted specificity and gene-silencing efficiency. In conclusion, we have established an efficient non-covalently complexed carrier (PF14:TG1) for siRNA delivery to human glioblastoma cells (U87), showing a significant two-fold increase in gene-silencing efficiency compared to the parent peptide PF14 and also improved specificity to U87 cells compared to non-glioma targeted cells.

The efficiency of lipid nanoparticles with an original cationic lipid as a siRNA delivery system for macrophages and dendritic cells

Small interfering of RNA (siRNA) technology has the potential to be a next-generation therapy. However, naked siRNA does not have high transfection efficiency and is rapidly degraded after systemic injection, so an appropriate drug delivery system (DDS) is required for clinical use. Several potential systems have been assessed, clinically focusing on hepatocyte or cancer tissue using siRNA. However, targeting immune cells using siRNA is still challenging, and a new DDS is required. In this study, we prepared lipid nanoparticles (LNP) composed of original cationic lipid, neutral lipid of DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) and PEG2000-DMPE (N-(carbonyl-methoxypolyethyleneglycol 2000)-1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine, sodium salt). Our LNP encapsulating siRNA (LNP/siRNA) exerted a knock-down (KD) effect on mouse inflammatory peritoneal macrophages in vitro. In addition, an in vivo KD effect by systemic administration of LNP/siRNA was observed in macrophages and dendritic cells (DCs) in mice. Furthermore, our LNP/siRNA showed in vitro KD effects not only on murine cells but also on human cells like monocyte-derived macrophages (MDMs) and monocyte-derived DCs (MDDCs). These results indicate the potential utility of our LNP for siRNA-based therapy targeting macrophages and DCs. Because these cells are known to have a significant role in several kinds of diseases, and siRNA can specifically suppress target genes that are closely associated with disease states and are untreatable by small molecules or antibodies. Therefore, delivering siRNA by our LNP to macrophages and DCs could provide novel therapies.

Cell-Penetrating Peptides to Enhance Delivery of Oligonucleotide-Based Therapeutics

The promise of nucleic acid based oligonucleotides as effective genetic therapies has been held back by their low bioavailability and poor cellular uptake to target tissues upon systemic administration. One such strategy to improve upon delivery is the use of short cell-penetrating peptides (CPPs) that can be either directly attached to their cargo through covalent linkages or through the formation of noncovalent nanoparticle complexes that can facilitate cellular uptake. In this review, we will highlight recent proof-of-principle studies that have utilized both of these strategies to improve nucleic acid delivery and discuss the prospects for translation of this approach for clinical application.

One-Pot Parallel Synthesis of Lipid Library via Thiolactone Ring Opening and Screening for Gene Delivery

Efficient delivery of nucleic acids into cells is of great interest in the field of cell biology and gene therapy. Despite a lot of research, transfection efficiency and structural diversity of gene-delivery vectors are still limited. A better understanding of the structure-function relationship of gene delivery vectors is also essential for the design of novel and intelligent delivery vectors, efficient in "difficult-to-transfect" cells and in vivo clinical applications. Most of the existing strategies for the synthesis of gene-delivery vectors require multiple steps and lengthy procedures. Here, we demonstrate a facile, three-component one-pot synthesis of a combinatorial library of 288 structurally diverse lipid-like molecules termed "lipidoids" via a thiolactone ring opening reaction. This strategy introduces the possibility to synthesize lipidoids with hydrophobic tails containing both unsaturated bonds and reducible disulfide groups. The whole synthesis and purification are convenient, extremely fast, and can be accomplished within a few hours. Screening of the produced lipidoids using HEK293T cells without addition of helper lipids resulted in identification of highly stable liposomes demonstrating ∼95% transfection efficiency with low toxicity.

Humanized Mice as Unique Tools for Human-Specific Studies

With an increasing human population, medical research is pushed to progress into an era of precision therapy. Humanized mice are at the very heart of this new forefront where it is acutely required to decipher human-specific disease pathogenesis and test an array of novel therapeutics. In this review, “humanized” mice are defined as immunodeficient mouse engrafted with functional human biological systems. Over the past decade, researchers have been conscientiously making improvements on the development of humanized mice as a model to closely recapitulate disease pathogenesis and drug mechanisms in humans. Currently, literature is rife with descriptions of novel and innovative humanized mouse models that hold a significant promise to become a panacea for drug innovations to treat and control conditions such as infectious disease and cancer. This review will focus on the background of humanized mice, diseases, and human-specific therapeutics tested on this platform as well as solutions to improve humanized mice for future clinical use.

Multi-Functional Peptide-MicroRNA Nanocomplex for Targeted MicroRNA Delivery and Function Imaging

Targeted delivery of microRNA (miRNA) mimics into specific cells/tissues and real-time monitoring on the biological function of delivered miRNA mimics at molecular level represent two major challenges in the development of miRNA-based therapeutics. Here we report a highly efficient method to address these two challenges simultaneously by using the self-assembled nanocomplex formed by miRNA mimics with a multi-functional peptide conjugate. Using the nanocomplex formed by tumor-suppressive miR-34a and the multi-functional peptide conjugate FA-R9-FP_cas3 , we demonstrated the highly efficient and target-selective delivery of miR-34a into HeLa cells and tumors. With the activatable fluorescence probe integrated in the peptide conjugate FA-R9-FP_cas3 , the intracellular function of miR-34a delivered by the nanocomplex to upregulate active Caspase-3 was imaged in real-time. The nanocomplex also showed significant therapeutic effects to induce apoptosis in HeLa cells and to suppress tumor growth upon tail vein injection into living mice bearing subcutaneous HeLa tumors.

Chemical modifications of nucleic acid drugs and their delivery systems for gene-based therapy

Gene-based therapy is one of essential therapeutic strategies for precision medicine through targeting specific genes in specific cells of target tissues. However, there still exist many problems that need to be solved, such as safety, stability, selectivity, delivery, as well as immunity. Currently, the key challenges of gene-based therapy for clinical potential applications are the safe and effective nucleic acid drugs as well as their safe and efficient gene delivery systems. In this review, we first focus on current nucleic acid drugs and their formulation in clinical trials and on the market, including antisense oligonucleotide, siRNA, aptamer, and plasmid nucleic acid drugs. Subsequently, we summarize different chemical modifications of nucleic acid drugs as well as their delivery systems for gene-based therapeutics in vivo based on nucleic acid chemistry and nanotechnology methods.

Improved method for synthesis of low molecular weight protamine-siRNA conjugate

RNAi technology has aroused wide public interest due to its high efficiency and specificity to treat multiple types of diseases. However, the effective delivery of siRNA remains a challenge due to its large molecular weight and strong anionic charge. Considering their remarkable functions in vivo and features that are often desired in drug delivery carriers, biomimetic systems for siRNA delivery become an effective and promising strategy. Based on this, covalent attachment of synthetic cell penetrating peptides (CPP) to siRNA has become of great interest. We developed a monomeric covalent conjugate of low molecular weight protamine (LMWP, a well-established CPP) and siRNA via a cytosol-cleavable disulfide linkage using PEG as a crosslinker. Results showed that the conjugates didn't generate coagulation, and exhibited much better RNAi potency and intracellular delivery compared with the conventional charge-complexed CPP/siRNA aggregates. Three different synthetic and purification methods were compared in order to optimize synthesis efficiency and product yield. The methodology using hetero-bifunctional NHS–PEG–OPSS as a crosslinker to synthesize LMWP–siRNA simplified the synthesis and purification process and produced the highest yield. These results pave the way towards siRNA biomimetic delivery and future clinical translation.

From in silico hit to long-acting late-stage preclinical candidate to combat HIV-1 infection

The HIV-1 pandemic affecting over 37 million people worldwide continues, with nearly one-half of the infected population on highly active antiretroviral therapy (HAART). Major therapeutic challenges remain because of the emergence of drug-resistant HIV-1 strains, limitations because of safety and toxicity with current HIV-1 drugs, and patient compliance for lifelong, daily treatment regimens. Nonnucleoside reverse transcriptase inhibitors (NNRTIs) that target the viral polymerase have been a key component of the current HIV-1 combination drug regimens; however, these issues hamper them. Thus, the development of novel more effective NNRTIs as anti-HIV-1 agents with fewer long-term liabilities, efficacy on new drug-resistant HIV-1 strains, and less frequent dosing is crucial. Using a computational and structure-based design strategy to guide lead optimization, a 5 µM virtual screening hit was transformed to a series of very potent nanomolar to picomolar catechol diethers. One representative, compound I, was shown to have nanomolar activity in HIV-1-infected T cells, potency on clinically relevant HIV-1 drug-resistant strains, lack of cytotoxicity and off-target effects, and excellent in vivo pharmacokinetic behavior. In this report, we show the feasibility of compound I as a late-stage preclinical candidate by establishing synergistic antiviral activity with existing HIV-1 drugs and clinical candidates and efficacy in HIV-1-infected humanized [human peripheral blood lymphocyte (Hu-PBL)] mice by completely suppressing viral loads and preventing human CD4⁺ T-cell loss. Moreover, a long-acting nanoformulation of compound I [compound I nanoparticle (compound I-NP)] in poly(lactide-coglycolide) (PLGA) was developed that shows sustained maintenance of plasma drug concentrations and drug efficacy for almost 3 weeks after a single dose.

Targeted inhibition of hantavirus replication and intracranial pathogenesis by a chimeric protein-delivered siRNA

Hantavirus (HV) infection, which underlies hantavirus hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome, remains to be a severe clinical challenge. Here, we synthesized small interfering RNAs (siRNAs) that target the encoding sequences of HV strain 76-118, and validated their inhibitory role in virus replication in HV-infected monkey kidney Vero E6 cells. A chimeric protein, 3G1-Cκ-tP, consisting of a single-chain antibody fragment (3G1) against the HV surface envelop glycoprotein, the constant region of human immunoglobulin κ chain (Cκ), and truncated protamine (amino acids 8-29, tP), was further generated. The fusion protein showed high affinity to HV antigen on the infected cell membrane, and internalized through clathrin-mediated endocytosis; it bound to siRNAs via the basic nucleic acid-rich protamine fragment, leading to their specific delivery into HV-infected cells and efficient inhibition of virus replication. An encephalitis mouse model was established via intracranial HV administration. Intraperitoneal injection of siRNAs complexed with 3G1-Cκ-tP achieved specific distribution of siRNAs in HV-infected brain cells, significantly reduced HV antigen levels, and effective protection from HV infection-derived animal death. These results provide a compelling rationale for novel therapeutic protocols designed for HV infection and related disorders.

Cytosolic delivery of siRNA by ultra-high affinity dsRNA binding proteins

Protein-based methods of siRNA delivery are capable of uniquely specific targeting, but are limited by technical challenges such as low potency or poor biophysical properties. Here, we engineered a series of ultra-high affinity siRNA binders based on the viral protein p19 and developed them into siRNA carriers targeted to the epidermal growth factor receptor (EGFR). Combined in trans with a previously described endosome-disrupting agent composed of the pore-forming protein Perfringolysin O (PFO), potent silencing was achieved in vitro with no detectable cytotoxicity. Despite concerns that excessively strong siRNA binding could prevent the discharge of siRNA from its carrier, higher affinity continually led to stronger silencing. We found that this improvement was due to both increased uptake of siRNA into the cell and improved pharmacodynamics inside the cell. Mathematical modeling predicted the existence of an affinity optimum that maximizes silencing, after which siRNA sequestration decreases potency. Our study characterizing the affinity dependence of silencing suggests that siRNA-carrier affinity can significantly affect the intracellular fate of siRNA and may serve as a handle for improving the efficiency of delivery. The two-agent delivery system presented here possesses notable biophysical properties and potency, and provide a platform for the cytosolic delivery of nucleic acids.

Elaboration on the Distribution of Hydrophobic Segments in the Chains of Amphiphilic Cationic Polymers for Small Interfering RNA Delivery

Hydrophobization of cationic polymers, as an efficient strategy, had been widely developed in the structure of cationic polymer micelles to improve the delivery efficiency of nucleic acids. However, the distribution of hydrophobic segments in the polymer chains is rarely considered. Here, we have elaborated three types of hydrophobized polyethylene glycol (PEG)-blocked cationic polymers with different distributions of the hydrophobic segments in the polymer chains PEG-PAM-PDP (E-A-D), PEG-PDP-PAM (E-D-A), and PEG-P(AM/DP) (E-(A/D)), which were synthesized by reversible addition-fragmentation chain transfer polymerization of methoxy PEG, cationic monomer aminoethyl methacrylate, and pH-sensitive hydrophobic monomer 2-diisopropylaminoethyl methacrylate, respectively. In aqueous solution, all of the three copolymers, E-A-D, E-D-A, and E-(A/D), were able to spontaneously form nanosized micelles (100-150 nm) (M_E-A-D, M_E-D-A, and M_E-(A/D)) and well-incorporated small interfering RNA (siRNA) into complex micelles (CMs). The effect of distributions of the hydrophobic segments on siRNA delivery had been evaluated in vitro and in vivo. Compared with M_E-D-A and M_E-(A/D), M_E-A-D showed the best siRNA binding capacity to form stable M_E-A-D/siRNA CMs less than 100 nm, mediated the best gene-silencing efficiency and inhibition effect of tumor cell growth in vitro, and showed better liver gene-silencing effect in vivo. In the case of M_E-(A/D) with a random distribution of cationic and hydrophobic segments, a gene-silencing efficiency higher than Lipo2000 but lesser than M_E-A-D and M_E-D-A was obtained. As the mole ratio of positive and negative charges increased, M_E-D-A/siRNA and M_E-A-D/siRNA showed similar performances in size, zeta potential, cell uptake, and gene silencing, but M_E-(A/D)/siRNA showed reversed performances. In addition, M_E-A-D as the best siRNA carrier was evaluated in the tumor tissue in the xenograft murine model and showed good anticancer capacity. Obviously, the distribution of the hydrophobic segments in the amphiphilic cationic polymer chains should be seriously considered in the design of siRNA vectors.

Targeting of CDK9 with indirubin 3'-monoxime safely and durably reduces HIV viremia in chronically infected humanized mice

Successful propagation of HIV in the human host requires entry into a permissive cell, reverse transcription of viral RNA, integration into the human genome, transcription of the integrated provirus, and assembly/release of new virus particles. Currently, there are antiretrovirals against each of these viral steps, except for provirus transcription. An inhibitor of HIV transcription could both increase potency of treatment and suppress drug-resistant strains. Cellular cyclin-dependent kinase 9 (CDK9) serves as a cofactor for the HIV Tat protein and is required for effective transcription of the provirus. Previous studies have shown that the CDK9 inhibitor Indirubin 3’-monoxime (IM) inhibits HIV transcription in vitro and in short-term in vivo studies of HIV acute infection in humanized mice (PBMC-NSG model), suggesting a therapeutic potential. The objective of this study is to evaluate the toxicity, pharmacokinetics and long-term antiviral activity of IM during chronic HIV infection in humanized mice (HSC-NSG model). We show that IM concentrations above EC₅₀ values are rapidly achieved and sustained for > 3 h in plasma, and that non-toxic concentrations durably reduce HIV RNA levels. In addition, IM enhanced the antiviral activity of antiretrovirals from the reverse transcriptase, protease and integrase inhibitor classes in in vitro infectivity assays. In summary, IM may enhance current antiretroviral treatments and could help achieve a “functional cure” in HIV patients by preventing expression of proviruses.

Engineering hematopoietic stem cells toward a functional cure of human immunodeficiency virus infection

The battle with human immunodeficiency virus (HIV) has been ongoing for more than 30 years, and although progress has been made, there are still significant challenges remaining. A few unique features render HIV to be one of the toughest viruses to conquer in the modern medicine era, such as the ability to target the host immune system, persist by integrating into the host genome and adapt to a hostile environment such as a single anti-HIV medication by continuously evolving. The finding of combination anti-retroviral therapy (cART) about 2 decades ago has transformed the treatment options for HIV-infected patients and significantly improved patient outcomes. However, finding an HIV cure has proven to be extremely challenging with the only known exception being the so-called "Berlin patient," whose immune system was replaced by stem cell transplants from a donor missing one of HIV's key co-receptors (CCR5). The broad application of this approach is limited by the requirement of an HLA-matched donor who is also homozygous for the rare CCR5 delta32 deletion. On the other hand, the Berlin patient provided the proof of concept of a potential cure for HIV using HIV-resistant hematopoietic stem cells (HSCs), revitalizing the hope to find an HIV cure that is broadly applicable. Here we will review strategies and recent attempts to engineer HIV-resistant HSCs as a path to an HIV cure.

Progress in HIV-1 antibody research using humanized mice

PURPOSE OF REVIEW

Recent discoveries of highly potent broadly HIV-1 neutralizing antibodies provide new opportunities to successfully prevent, treat, and potentially cure HIV-1 infection. To test their activity in vivo, humanized mice have been shown to be a powerful model and were used to investigate antibody-mediated prevention and therapy approaches. In this review, we will summarize recent findings in humanized mice that have informed on the potential use of broadly neutralizing antibodies targeting HIV-1 in humans.

RECENT FINDINGS

Humanized mouse models have been used to demonstrate the antiviral efficacy of HIV-1 neutralizing antibodies in vivo. It has been shown that a combination of antibodies can suppress viremia below the limit of detection and targets the HIV-1 reservoir. Moreover, passively administered antibodies and vector-mediated antibody production protect humanized mice from HIV-1 infection. Finally, immunization studies in knock-in/transgenic mice carrying human antibody gene segments have informed on potential vaccination strategies to induce broad and potent HIV-1 neutralizing antibodies.

SUMMARY

Humanized mouse models are of great value for HIV-1 research. They represent a highly versatile in vivo system to investigate novel approaches for HIV-1 prevention and therapy and expedite the critical translation from basic findings to clinical application.

A Poly(Propyleneimine) Dendrimer-Based Polyplex-System for Single-Chain Antibody-Mediated Targeted Delivery and Cellular Uptake of SiRNA

Therapeutics based on small interfering RNAs (siRNAs) offer a great potential to treat so far incurable diseases or metastatic cancer. However, the broad application of siRNAs using various nonviral carrier systems is hampered by unspecific toxic side effects, poor pharmacokinetics due to unwanted delivery of siRNA-loaded nanoparticles into nontarget organs, or rapid renal excretion. In order to overcome these obstacles, several targeting strategies using chemically linked antibodies and ligands have emerged. This study reports a new modular polyplex carrier system for targeted delivery of siRNA, which is based on transfection-disabled maltose-modified poly(propyleneimine)-dendrimers (mal-PPI) bioconjugated to single chain fragment variables (scFvs). To achieve targeted delivery into tumor cells expressing the epidermal growth factor receptor variant III (EGFRvIII), monobiotinylated anti-EGFRvIII scFv fused to a Propionibacterium shermanii transcarboxylase-derived biotinylation acceptor (P-BAP) is bioconjugated to mal-PPI through a novel coupling strategy solely based on biotin-neutravidin bridging. In contrast to polyplexes containing an unspecific control scFv-P-BAP, the generated EGFRvIII-specific polyplexes are able to exclusively deliver siRNA to tumor cells and tumors by receptor-mediated endocytosis. These results suggest that receptor-mediated uptake of otherwise noninternalized mal-PPI-based polyplexes is a promising avenue to improve siRNA therapy of cancer, and introduce a novel strategy for modular bioconjugation of protein ligands to nanoparticles.

Molecular Mechanisms and Biological Functions of siRNA

One of the most important advances in biology has been the discovery that siRNA (small interfering RNA) is able to regulate the expression of genes, by a phenomenon known as RNAi (RNA interference). The discovery of RNAi, first in plants and Caenorhabditis elegans and later in mammalian cells, led to the emergence of a transformative view in biomedical research. siRNA has gained attention as a potential therapeutic reagent due to its ability to inhibit specific genes in many genetic diseases. siRNAs can be used as tools to study single gene function both in vivo and in-vitro and are an attractive new class of therapeutics, especially against undruggable targets for the treatment of cancer and other diseases. The siRNA delivery systems are categorized as non-viral and viral delivery systems. The non-viral delivery system includes polymers; Lipids; peptides etc. are the widely studied delivery systems for siRNA. Effective pharmacological use of siRNA requires 'carriers' that can deliver the siRNA to its intended site of action. The carriers assemble the siRNA into supramolecular complexes that display functional properties during the delivery process.

Responsive Nanocarriers as an Emerging Platform for Cascaded Delivery of Nucleic Acids to Cancer

Cascades of systemic and intracellular obstacles, including low stability in blood, little tumor accumulation, weak tumor penetration, poor cellular uptake, inefficient endosomal escape and deficient disassembly in the cytoplasm, must be overcome in order to deliver nucleic acid drugs for cancer therapy. Nanocarriers that are sensitive to a variety of physiological stimuli, such as pH, redox status, and cell enzymes, are substantially changing the landscape of nucleic acid drug delivery by helping to overcome cascaded systemic and intracellular barriers. This review discusses nucleic acid-based therapeutics, systemic and intracellular barriers to efficient nucleic acid delivery, and nanocarriers responsive to extracellular and intracellular biological stimuli to overcome individual barriers. In particular, responsive nanocarriers for the cascaded delivery of nucleic acids in vivo are highlighted. Developing novel cascaded nanocarriers that transform their physicochemical properties in response to various stimuli in a timely and spatially controlled manner for nucleic acid drug delivery holds great potential for translating the promise of nucleic acid drugs and achieving clinically successful cancer therapy.

Fluorinated PEG-Polypeptide Polyplex Micelles Have Good Serum-Resistance and Low Cytotoxicity for Gene Delivery

A novel PEGylation polypeptide, poly(ethylene glycol)-b-poly(l-lysine)-b-poly(l-cysteine) (PEG-PLL-PCys) triblock copolymer is synthesized via the sequential ring-opening polymerization of amino acid N-carboxyanhydrides initiated by methoxypolyethylene glycol amine (mPEG-NH₂ , M_w is 2 kDa). Subsequently, the obtained polypeptide is partially conjugated with fluorocarbon chains via disulfide exchange reaction. PLL segment can condense plasmid DNA through an electrostatic force to form a complex core, PEG segment surrounding the complex like a corona can prevent the complex from precipitation and reduce the adsorption of serum, while PCys segment with fluorocarbon can enhance the cellular uptake and the stability of the formed polyplex micelles in physiological conditions. Experiment results exhibit that the fluorinated polypeptides have low cytotoxicity and good gene transfection efficiency even in the presence of 50% fetal bovine serum.

Intranasal drug delivery of small interfering RNA targeting Beclin1 encapsulated with polyethylenimine (PEI) in mouse brain to achieve HIV attenuation

We previously reported that activation of the host autophagic protein, Beclin1, by HIV-1 infection represents an essential mechanism in controlling HIV replication and viral-induced inflammatory responses in microglial cells. Existing antiretroviral therapeutic approaches have been limited in their ability to cross the blood-brain barrier effectively and recognize and selectively eliminate persistent HIV-infected brain reservoirs. In the present study and for the first time, the bio-distribution and efficacy of noninvasive intranasal delivery of small interfering RNA (siRNA) against the Beclin1 gene using the cationic linear polyethylenimines (PEI) as a gene carrier was investigated in adult mouse brain. Fluorescein isothiocyanate (FITC)-labeled control siRNA delivered intranasally was found in the cytoplasm of neurons and glial cells of the prefrontal cortex at 4 and 24 hours post-delivery, with no major adverse immune reaction encountered. Intranasal delivery of the siRNA targeting Beclin1 significantly depleted the target protein expression levels in brain tissues with no evidence of toxicity. Binding of siRNA to PEI-polymer was characterized and confirmed by Raman spectroscopy. These results indicate that the intranasal drug delivery allows for the direct delivery of the PEI-siRNA nano-complex to the central nervous system, which could potentially offer an efficient means of gene silencing-mediated therapy in the HIV-infected brain.

Polyethylene glycol-poly(ε-benzyloxycarbonyl-l-lysine)-conjugated VEGF siRNA for antiangiogenic gene therapy in hepatocellular carcinoma

A polyethylene glycol-poly(ε-benzyloxycarbonyl-l-lysine) (PEG-SS-PLL) block copolymer based on a disulfide-linked, novel biodegradable catiomer bearing a PEG-sheddable shell was developed to avoid "PEG dilemma" in nanoparticle intracellular tracking of PEG-PLL where PEG was nondegradable. However, PEG-SS-PLL catiomers have not been used to deliver small interfering VEGF RNA (siVEGF) in antiangiogenesis gene therapy. In this study, we aimed to investigate whether this novel biodegradable catiomer can deliver siVEGF into cancer cells and at the same time have an antitumor effect in a xenograft mouse model. It was found that PEG-SS-PLL efficiently delivered siVEGF with negligible cytotoxicity, and significantly decreased the expression of VEGF at both the messenger-RNA and protein levels both in vitro and in vivo, and thus tumor growth was inhibited. Our findings demonstrated that PEG-SS-PLL/siVEGF could potentially be applied to antiangiogenesis gene therapy for hepatocellular carcinoma.

Noninvasive imaging of c(RGD)2 -9R as a potential delivery carrier for transfection of siRNA in malignant tumors

The purpose of our study was to develop and evaluate a novel integrin α_v β₃ -specific delivery carrier for transfection of siRNA in malignant tumors. We adopted arginine-glycine-aspartate (RGD) motif as a tissue target for specific recognition of integrin α_ν β₃ . A chimaeric peptide was synthesized by adding nonamer arginine residues (9-arginine [9R]) at the carboxy terminus of cyclic-RGD dimer, designated as c(RGD)₂ -9R, to enable small interfering RNA (siRNA) binding. To test the applicability of the delivery carrier in vivo, c(RGD)₂ -9R was labeled with radionuclide of technetium-99m. Biodistribution and γ-camera imaging studies were performed in HepG2 xenograft-bearing nude mice. As results, an optimal 10:1 molar ratio of ^99m Tc-c(RGD)₂ -9R to siRNA was indicated by the electrophoresis on agarose gels. ^99m Tc-c(RGD)₂ -9R/siRNA remained stable under a set of conditions in vitro. For in vivo study, tumor radioactivity uptake of ^99m Tc-c(RGD)₂ -9R/siRNA in nude mice bearing HepG2 xenografts was significantly higher than that of control probe (P < .05). The xenografts were clearly visualized at 4 hours till 6 hours noninvasively after intravenous injection of ^99m Tc-c(RGD)₂ -9R/siRNA, while the xenografts were not visualized at any time after injection of control probe. It was concluded that c(RGD)₂ -9R could be an effective siRNA delivery carrier. Technetium-99m radiolabeled-delivery carrier represents a potential imaging strategy for RNAi-based therapy.

Current Progress in Non-viral RNAi-Based Delivery Strategies to Lymphocytes

RNAi-based therapy holds great promise, as it can be utilized for the treatment of multiple conditions in an accurate manner via sequence-specific manipulation of gene expression. To date, RNAi therapeutics have advanced into clinical trials for liver diseases and solid tumors; however, delivery of RNAi to leukocytes in general and to lymphocytes in particular remains a challenge. Lymphocytes are notoriously hard to transduce with RNAi payloads and are disseminated throughout the body, often located in deep tissues; therefore, developing an efficient systemic delivery system directed to lymphocytes is not a trivial task. Successful manipulation of lymphocyte function with RNAi possesses immense therapeutic potential, as it will enable researchers to resolve lymphocyte-implicated diseases such as inflammation, autoimmunity, transplant rejection, viral infections, and blood cancers. This potential has propelled the development of novel targeted delivery systems relying on the accumulating research knowledge from multiple disciplines, including materials science and engineering, immunology, and genetics. Here, we will discuss the recent progress in non-viral delivery strategies of RNAi payloads to lymphocytes. Special emphasis will be made on the challenges and potential opportunities in manipulating lymphocyte function with RNAi. These approaches might ultimately become a novel therapeutic modality to treat leukocyte-related diseases.

Targeted deletion of Traf2 allows immunosuppression-free islet allograft survival in mice

AIMS/HYPOTHESIS

Administration of anti-CD40 ligand (CD40L) antibodies has been reported to allow long-term islet allograft survival in non-human primates without the need for exogenous immunosuppression. However, the use of anti-CD40L antibodies was associated with thromboembolic complications. Targeting downstream intracellular components shared between CD40 and other TNF family co-stimulatory molecules could bypass these complications. TNF receptor associated factor 2 (TRAF2) integrates multiple TNF receptor family signalling pathways that are critical for T cell activation and may be a central node of alloimmune responses.

METHODS

T cell-specific Traf2-deficient mice (Traf2TKO) were generated to define the role of TRAF2 in CD4⁺ T cell effector responses that mediate islet allograft rejection in vivo. In vitro allograft responses were tested using mixed lymphocyte reactions and analysis of IFN-γ and granzyme B effector molecule expression. T cell function was assessed using anti-CD3/CD28-mediated proliferation and T cell polarisation studies.

RESULTS

Traf2TKO mice exhibited permanent survival of full MHC-mismatched pancreatic islet allografts without exogenous immunosuppression. Traf2TKO CD4⁺ T cells exhibited reduced proliferation, activation and acquisition of effector function following T cell receptor stimulation; however, both Traf2TKO CD4⁺ and CD8⁺ T cells exhibited impaired alloantigen-mediated proliferation and acquisition of effector function. In polarisation studies, Traf2TKO CD4⁺ T cells preferentially converted to a T helper (Th)2 phenotype, but exhibited impaired Th17 differentiation. Without TRAF2, thymocytes exhibited dysregulated TNF-mediated induction of c-Jun N-terminal kinase (JNK) and canonical NFκB pathways. Critically, targeting TRAF2 in T cells did not impair the acute phase of CD8-dependent viral immunity. These data highlight a specific requirement for a TRAF2-NFκB and TRAF2-JNK signalling cascade in T cell activation and effector function in rejecting islet allografts.

CONCLUSION/INTERPRETATION

Targeting TRAF2 may be useful as a therapeutic approach for immunosuppression-free islet allograft survival that avoids the thromboembolic complications associated with the use of anti-CD40L antibodies.

Longitudinal imaging of HIV-1 spread in humanized mice with parallel 3D immunofluorescence and electron tomography

Dissemination of HIV-1 throughout lymphoid tissues leads to systemic virus spread following infection. We combined tissue clearing, 3D-immunofluorescence, and electron tomography (ET) to longitudinally assess early HIV-1 spread in lymphoid tissues in humanized mice. Immunofluorescence revealed peak infection density in gut at 10–12 days post-infection when blood viral loads were low. Human CD4+ T-cells and HIV-1–infected cells localized predominantly to crypts and the lower third of intestinal villi. Free virions and infected cells were not readily detectable by ET at 5-days post-infection, whereas HIV-1–infected cells surrounded by pools of free virions were present in ~10% of intestinal crypts by 10–12 days. ET of spleen revealed thousands of virions released by individual cells and discreet cytoplasmic densities near sites of prolific virus production. These studies highlight the importance of multiscale imaging of HIV-1–infected tissues and are adaptable to other animal models and human patient samples.

DOI:http://dx.doi.org/10.7554/eLife.23282.001

Human CD64-targeted non-viral siRNA delivery system for blood monocyte gene modulation

A subset of phagocytes including inflammatory monocytes in blood migrate and give rise to macrophages in inflammatory tissues which generated the idea that blood monocytes are the therapeutic targets for drug delivery. Fc gamma receptor I (CD64) is a membrane receptor for the Fc region of immunoglobulin G, primarily expressed on monocyte-lineage, and H22 a monoclonal antibody for human CD64 had shown rapid blood monocyte binding and occupation in clinical studies. Small interfering RNA-mediated gene silencing as a therapeutic has been proposed and is a promising strategy in terms of its "knock-down" ability on the target gene prior to translation. However, its instability and off-targeting effect must be overcome for success in clinical studies. In this study, we developed a non-viral delivery system composed of oligo-nona-arginine (9R) and anti-human CD64 single chain antibodies (H22) for human monocyte-specific siRNA delivery. A targeted and efficient siRNA delivery mediated by anti-CD64 scFv-9R was observed in CD64 positive human leukemia cells, THP-1. With primary human blood cells, anti-CD64 scFv-9R mediated gene silencing was quantitatively confirmed representing blood monocyte selective gene delivery. These results demonstrate the potential of anti-CD64 scFv-9R mediated siRNA delivery for the treatment of human inflammatory diseases via blood monocytes gene delivery.

Construction and Biological Evaluation of a Novel Integrin ανβ₃-Specific Carrier for Targeted siRNA Delivery In Vitro

(1) Background: The great potential of RNA interference (RNAi)-based gene therapy is premised on the effective delivery of small interfering RNAs (siRNAs) to target tissues and cells. Hence, we aimed at developing and examining a novel integrin αvβ₃-specific delivery carrier for targeted transfection of siRNA to malignant tumor cells; (2) Methods: Arginine-glycine-aspartate motif (RGD) was adopted as a tissue target for specific recognition of integrin αvβ₃. To enable siRNA binding, a chimeric peptide was synthesized by adding nonamer arginine residues (9R) at the carboxy terminus of cyclic-RGD dimer, designated as c(RGD)₂-9R. The efficiency of 9R peptide transferring siRNA was biologically evaluated in vitro by flow cytometry, confocal microscopy, and Western blot; (3) Results: An optimal 10:1 molar ratio of c(RGD)₂-9R to siRNA was confirmed by the electrophoresis on agarose gels. Both the flow cytometry and confocal microscopy results testified that transfection of c(RGD)₂-9R as an siRNA delivery carrier was obviously higher than the naked-siRNA group. The results of Western blot demonstrated that these 9R peptides were able to transduce siRNA to HepG2 cells in vitro, resulting in efficient gene silencing; and (4) Conclusion: The chimeric peptide of c(RGD)₂-9R can be developed as an effective siRNA delivery carrier and shows potential as a new strategy for RNAi-based gene therapy.

Functional peptides for siRNA delivery

siRNA is considered as a potent therapeutic agent because of its high specificity and efficiency in suppressing genes that are overexpressed during disease development. For nearly two decades, a significant amount of efforts has been dedicated to bringing the siRNA technology into clinical uses. However, only limited success has been achieved to date, largely due to the lack of a cell type-specific, safe, and efficient delivery technology to carry siRNA into the target cells' cytosol where RNA interference takes place. Among the emerging candidate nanocarriers for siRNA delivery, peptides have gained popularity because of their structural and functional diversity. A variety of peptides have been discovered for their ability to translocate siRNA into living cells via different mechanisms such as direct penetration through the cellular membrane, endocytosis-mediated cell entry followed by endosomolysis, and receptor-mediated uptake. This review is focused on the multiple roles played by peptides in siRNA delivery, such as membrane penetration, endosome disruption, targeting, as well as the combination of these functionalities.

Leukocyte-mediated Delivery of Nanotherapeutics in Inflammatory and Tumor Sites

Nanotechnology has become a powerful tool to potentially translate nanomedicine from bench to bedside. Nanotherapeutics are nanoparticles (NPs) loaded with drugs and possess the property of tissue targeting after surfaces of NPs are bio-functionalized. Designing smaller size of nanotherapeutics is presumed to increase tumor targeting based on the EPR (enhanced permeability and retention) effect. Since the immune systems possess a defence mechanism to fight diseases, there is an emerging concept that NPs selectively target immune cells to mediate the active delivery of drugs into sites of disease. In this review, we will focus on a key question of how nanotherapeutics specifically target immune cells and hijack them as a delivery vehicle to transport nanotherapeutics into disease tissues, thus possibly improving current therapies in inflammation, immune disorders and cancers. We will also discuss the challenges and opportunities for this new strategy of leukocyte-mediated delivery of nanotherapeutics.

The Application of Humanized Mouse Models for the Study of Human Exclusive Viruses

The symbiosis between humans and viruses has allowed human tropic pathogens to evolve intricate means of modulating the human immune response to ensure its survival among the human population. In doing so, these viruses have developed profound mechanisms that mesh closely with our human biology. The establishment of this intimate relationship has created a species-specific barrier to infection, restricting the virus-associated pathologies to humans. This specificity diminishes the utility of traditional animal models. Humanized mice offer a model unique to all other means of study, providing an in vivo platform for the careful examination of human tropic viruses and their interaction with human cells and tissues. These types of animal models have provided a reliable medium for the study of human-virus interactions, a relationship that could otherwise not be investigated without questionable relevance to humans.

Trileucine residues in a ligand-CPP-based siRNA delivery platform improve endosomal escape of siRNA

siRNA entrapment within endosomes is a significant problem encountered with siRNA delivery platforms that co-opt receptor-mediated entry pathways. Attachment of a cell-penetrating peptide (CPP), such as nona-arginine (9R) to a cell receptor-binding ligand like the Rabies virus glycoprotein, RVG, allows effective siRNA delivery to the cytoplasm by non-endocytic pathways, but a significant amount of siRNA complexes also enters the cell by ligand-induced receptor endocytosis and remain localized in endosomes. Here, we report that the incorporation of trileucine (3 Leu) residues as an endo-osmolytic moiety in the peptide improves endosomal escape and intracellular delivery of siRNA. The trileucine motif did not affect early non-endosomal mechanism of cytoplasmic siRNA delivery but enhanced target gene silencing by >20% only beyond 24 h of transfection when siRNA delivery is mostly through the endocytic route and siRNA trapped in the endosomes at later stages were subject to release into cytoplasm. The mechanism may involve endosomal membrane disruption as trileucine residues lysed RBCs selectively under endosomal pH conditions. Interestingly <3 Leu or >3 Leu residues were not as effective, suggesting that 3 Leu residues are useful for enhancing cytoplasmic delivery of siRNA routed through endosomes.

Peptides for nucleic acid delivery

Nucleic acids and their synthetic oligonucleotide (ON) analogs are a group of gene therapeutic compounds which hold enormous clinical potential. Despite their undoubted potential, clinical translation of these molecules, however, has been largely held back by their limited bioavailability in the target tissues/cells. To overcome this, many different drug delivery systems have been devised. Among others, short delivery peptides, called cell-penetrating peptides (CPPs), have been demonstrated to allow for efficient delivery of nucleic acids and their ON analogs, in both cell culture and animal models. In this review, we provide brief overview of the latest advances in nucleic acid delivery with CPPs, covering the two main vectorization strategies, covalent conjugation and nanoparticle formation-based approach. In conclusion, CPP-based drug delivery systems have the capacity to overcome the hurdle of delivery and thus have the potential to facilitate the clinical translation of nucleic acid-based therapeutics.

Humanized mouse as an appropriate model for accelerated global HIV research and vaccine development: current trend

Humanized mouse models currently have seen improved development and have received wide applications. Its usefulness is observed in cell and tissue transplant involving basic and applied human disease research. In this article, the development of a new generation of humanized mice was discussed as well as their relevant application in HIV disease. Furthermore, current techniques employed to overcome the initial limitations of mouse model were reviewed. Highly immunodeficient mice which support cell and tissue differentiation and do not reject xenografts are indispensable for generating additional appropriate models useful in disease study, this phenomenom deserves emphases, scientific highlight and a definitive research focus. Since the early 2000s, a series of immunodeficient mice appropriate for generating humanized mice has been successively developed by introducing the IL-2Rγ^null gene (e.g. NOD/SCID/γc^null and Rag2^nullγc^null mice) through various genomic approaches. These mice were generated by genetically introducing human cytokine genes into NOD/SCID/γc^null and Rag2^nullγc^null mouse backgrounds. The application of these techniques serves as a quick and appropriate mechanistic model for basic and therapeutic investigations of known and emerging infections.

Evaluation and modeling of HIV based on communication theory in biological systems

Some forms of communication are used in biological systems such as HIV transmission in human beings. In this paper, we plan to get a unique insight into biological communication systems generally through the analogy between HIV infection and electrical communication system. The model established in this paper can be used to test and simulate various communication systems since it provides researchers with an opportunity. We interpret biological communication systems by using telecommunications exemplification from a layered communication protocol developed before and use the model to indicate HIV spreading. We also implement a simulation of HIV infection based on the layered communication protocol to predict the development of this disease and the results prove the validity of the model.

Cationic cell-penetrating peptides as vehicles for siRNA delivery

RNA interference mediated gene silencing has tremendous applicability in fields ranging from basic biological research to clinical therapy. However, delivery of siRNA across the cell membrane into the cytoplasm, where the RNA silencing machinery is located, is a significant hurdle in most primary cells. Cell-penetrating peptides (CPPs), peptides that possess an intrinsic ability to translocate across cell membranes, have been explored as a means to achieve cellular delivery of siRNA. Approaches using CPPs by themselves or through incorporation into other siRNA delivery platforms have been investigated with the intent of improving cytoplasmic delivery. Here, we review the utilization of CPPs for siRNA delivery with a focus on strategies developed to enhance cellular uptake, endosomal escape and cytoplasmic localization of CPP/siRNA complexes.

Oligonucleotide conjugates - Candidates for gene silencing therapeutics

The potential therapeutic and diagnostic applications of oligonucleotides (ONs) have attracted great attention in recent years. The capability of ONs to selectively inhibit target genes through antisense and RNA interference mechanisms, without causing un-intended sideeffects has led them to be investigated for various biomedical applications, especially for the treatment of viral diseases and cancer. In recent years, many researchers have focused on enhancing the stability and target specificity of ONs by encapsulating/complexing them with polymers or lipid chains to formulate nanoparticles/nanocomplexes/micelles. Also, chemical modification of nucleic acids has emerged as an alternative to impart stability to ONs against nucleases and other degrading enzymes and proteins found in blood. In addition to chemically modifying the nucleic acids directly, another strategy that has emerged, involves conjugating polymers/peptide/aptamers/antibodies/proteins, preferably to the sense strand (3'end) of siRNAs. Conjugation to the siRNA not only enhances the stability and targeting specificity of the siRNA, but also allows for the development of self-administering siRNA formulations, with a much smaller size than what is usually observed for nanoparticle (∼200nm). This review concentrates mainly on approaches and studies involving ON-conjugates for biomedical applications.

Recent advances in RNAi-based strategies for therapy and prevention of HIV-1/AIDS

RNA interference (RNAi) provides a powerful tool to silence specific gene expression and has been widely used to suppress host factors such as CCR5 and/or viral genes involved in HIV-1 replication. Newer nuclease-based gene-editing technologies, such as zinc finger nucleases (ZFN), transcription activator-like effector nucleases (TALEN) and the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system, also provide powerful tools to ablate specific genes. Because of differences in co-receptor usage and the high mutability of the HIV-1 genome, a combination of host factors and viral genes needs to be suppressed for effective prevention and treatment of HIV-1 infection. Whereas the continued presence of small interfering/short hairpin RNA (si/shRNA) mediators is needed for RNAi to be effective, the continued expression of nucleases in the gene-editing systems is undesirable. Thus, RNAi provides the only practical way for expression of multiple silencers in infected and uninfected cells, which is needed for effective prevention/treatment of infection. There have been several advances in the RNAi field in terms of si/shRNA design, targeted delivery to HIV-1 susceptible cells, and testing for efficacy in preclinical humanized mouse models. Here, we comprehensively review the latest advances in RNAi technology towards prevention and treatment of HIV-1.

The Exosome - A Naturally Secreted Nanoparticle and its Application to Wound Healing

Wound healing is a complex process and often delayed in patients with underlying chronic conditions. The cost of wound care is a significant burden to the society, warranting new techniques to prompt wound healing. Several studies have reported on the beneficial effects of mesenchymal stem cells (MSCs) function in recruiting host cells, releasing secretory factors and matrix proteins thereby increasing wound heal. These secrete bioactive trophic factors from MSCs also includes extracellular vesicles (EVs) or exosomes. Recent studies have shown that EVs are one of the key secretory products of MSCs mediating cell-to-cell communication to enhance wound healing. Current knowledge related to the potential use of EVs in wound healing is reviewed and the promising future for EVs - a naturally secreted nanoparticle - as an alternative to cell-based therapy is discussed.

Electro-Magnetic Nano-Particle Bound Beclin1 siRNA Crosses the Blood-Brain Barrier to Attenuate the Inflammatory Effects of HIV-1 Infection in Vitro

The purpose of this study was to evaluate a novel drug delivery system comprised of ferric-cobalt electro-magnetic nano-material (CoFe2O4@ BaTiO3; MENP) bound to siRNA targeting Beclin1 (MENP-siBeclin1) to cross the blood-brain barrier (BBB) and attenuate the neurotoxic effects of HIV-1 infection in the central nervous system following on-demand release of siRNA using an in vitro primary human BBB model. Beclin1 is a key protein in the regulation of the autophagy pathway and we have recently demonstrated the importance of Beclin1 in regulating viral replication and viral-induced inflammation in HIV-1-infected microglia. The MENP-siBeclin1 nano-formulation did not compromise the physiological function or integrity of the BBB model. Furthermore, the in vitro BBB data revealed that MENP-siBeclin1 could efficiently attenuate viral replication and viral-induced inflammation, likely due to STAT1/ NF-κB signaling pathways. MENP-siBeclin1 also silenced Beclin1 protein expression in HIV-1-infected microglial cells within the model system. In addition, the cytotoxic effects of direct treatment with siBeclin1 and MENP alone or in nano-formulation on primary human neuronal cells showed a minimal amount of cell death. Overall, the data shows that the nano-formulation can silence the BECN1 gene as an effective mechanism to attenuate HIV-1 replication and viral-induced inflammation in the context of the BBB.

Functional Delivery of siRNA by Disulfide-Constrained Cyclic Amphipathic Peptides

The promise of oligonucleotide therapeutic agents to perturb expression of disease-related genes remains unrealized, in part due to challenges with functional cellular delivery of these agents. Herein, we describe disulfide-constrained cyclic amphipathic peptides that complex with short-interfering RNA (siRNA) and affect functional cytosolic delivery and knockdown of target gene products in cell culture and in vivo to mouse lung. Reduction of the constraining disulfide bond and subsequent proteolytic clearance of the peptide are key design features that allow unmasking of the siRNA cargo and presentation to the RNA interference machinery.

TREX1 Knockdown Induces an Interferon Response to HIV that Delays Viral Infection in Humanized Mice

Despite their antiviral effect, the in vivo effect of interferons on HIV transmission is difficult to predict, because interferons also activate and recruit HIV-susceptible cells to sites of infection. HIV does not normally induce type I interferons in infected cells, but does if TREX1 is knocked down. Here, we investigated the effect of topical TREX1 knockdown and local interferon production on HIV transmission in human cervicovaginal explants and humanized mice. In explants in which TREX1 was knocked down, HIV induced interferons, which blocked infection. In humanized mice, even though TREX1 knockdown increased infiltrating immune cells, it delayed viral replication for 3-4 weeks. Similarly intravaginal application of type I interferons the day before HIV infection induced interferon responsive genes, reduced inflammation, and decreased viral replication. However, intravenous interferon enhanced inflammation and infection. Thus, in models of human sexual transmission, a localized interferon response inhibits HIV transmission but systemic interferons do not.

Targeted delivery of siRNA to activated T cells via transferrin-polyethylenimine (Tf-PEI) as a potential therapy of asthma

Asthma is a worldwide health problem. Activated T cells (ATCs) in the lung, particularly T helper 2 cells (Th2), are strongly associated with inducing airway inflammatory responses and chemoattraction of inflammatory cells in asthma. Small interfering RNA (siRNA) as a promising anti-sense molecule can specifically silence inflammation related genes in ATCs, however, lack of safe and efficient siRNA delivery systems limits the application of siRNA as a therapeutic molecule in asthma. Here, we designed a novel pulmonary delivery system of siRNA, transferrin-polyethylenimine (Tf-PEI), to selectively deliver siRNA to ATCs in the lung. Tf-PEI polyplexes demonstrated optimal physicochemical properties such as size, distribution, zeta-potential, and siRNA condensation efficiency. Moreover, in vitro studies showed significantly enhanced cellular uptake and gene knockdown mediated by Tf-PEI polyplexes in human primary ATCs. Biodistribution of polyplexes in a murine asthmatic model confirmed that Tf-PEI polyplexes can efficiently and selectively deliver siRNA to ATCs. In conclusion, the present work proves the feasibility to target ATCs in asthma via Tf receptor. This strategy could potentially be used to design an efficient siRNA delivery system for asthma therapy.

Advances in RNAi therapeutic delivery to leukocytes using lipid nanoparticles

Small interfering RNAs (siRNAs) therapeutics has advanced into clinical trials for liver diseases and solid tumors, but remain a challenge for manipulating leukocytes fate due to lack of specificity and safety issues. Leukocytes ingest pathogens and defend the body through a complex network. They are also involved in the pathogeneses of inflammation, viral infection, autoimmunity and cancers. Modulating gene expression in leukocytes using siRNAs holds great promise to treat leukocyte-mediated diseases. Leukocytes are notoriously hard to transduce with siRNAs and are spread throughout the body often located deep in tissues, therefore developing an efficient systemic delivery strategy is still a challenge. Here, we discuss recent advances in siRNA delivery to leukocyte subsets such as macrophages, monocytes, dendritic cells and lymphocytes. We focus mainly on lipid-based nanoparticles (LNPs) comprised of new generation of ionizable lipids and their ability to deliver siRNA to primary or malignant leukocytes in a targeted manner. Special emphasis is made on LNPs targeted to subsets of leukocytes and we detail a novel microfluidic mixing technology that could aid in changing the landscape of process development of LNPs from a lab tool to a potential novel therapeutic modality.