Novel viral vector systems for gene therapy

Corneal gene therapy: Structural and mechanistic understanding

Cornea, a dome-shaped and transparent front part of the eye, affords 2/3rd refraction and barrier functions. Globally, corneal diseases are the leading cause of vision impairment. Loss of corneal function including opacification involve the complex crosstalk and perturbation between a variety of cytokines, chemokines and growth factors generated by corneal keratocytes, epithelial cells, lacrimal tissues, nerves, and immune cells. Conventional small-molecule drugs can treat mild-to-moderate traumatic corneal pathology but requires frequent application and often fails to treat severe pathologies. The corneal transplant surgery is a standard of care to restore vision in patients. However, declining availability and rising demand of donor corneas are major concerns to maintain ophthalmic care. Thus, the development of efficient and safe nonsurgical methods to cure corneal disorders and restore vision in vivo is highly desired. Gene-based therapy has huge potential to cure corneal blindness. To achieve a nonimmunogenic, safe and sustained therapeutic response, the selection of a relevant genes, gene editing methods and suitable delivery vectors are vital. This article describes corneal structural and functional features, mechanistic understanding of gene therapy vectors, gene editing methods, gene delivery tools, and status of gene therapy for treating corneal disorders, diseases, and genetic dystrophies.

DDC-Promoter-Driven Chemogenetic Activation of SNpc Dopaminergic Neurons Alleviates Parkinsonian Motor Symptoms

Parkinson's disease (PD) is a neurodegenerative disorder with typical motor symptoms. Recent studies have suggested that excessive GABA from reactive astrocytes tonically inhibits dopaminergic neurons and reduces the expression of tyrosine hydroxylase (TH), the key dopamine-synthesizing enzyme, in the substantia nigra pars compacta (SNpc). However, the expression of DOPA decarboxylase (DDC), another dopamine-synthesizing enzyme, is relatively spared, raising a possibility that the live but non-functional TH-negative/DDC-positive neurons could be the therapeutic target for rescuing PD motor symptoms. However, due to the absence of a validated DDC-specific promoter, manipulating DDC-positive neuronal activity has not been tested as a therapeutic strategy for PD. Here, we developed an AAV vector expressing mCherry under rat DDC promoter (AAV-rDDC-mCherry) and validated the specificity in the rat SNpc. Modifying this vector, we expressed hM3Dq (Gq-DREADD) under DDC promoter in the SNpc and ex vivo electrophysiologically validated the functionality. In the A53T-mutated alpha-synuclein overexpression model of PD, the chemogenetic activation of DDC-positive neurons in the SNpc significantly alleviated the parkinsonian motor symptoms and rescued the nigrostriatal TH expression. Altogether, our DDC-promoter will allow dopaminergic neuron-specific gene delivery in rodents. Furthermore, we propose that the activation of dormant dopaminergic neurons could be a potential therapeutic strategy for PD.

The pathophysiology of immunoporosis: innovative therapeutic targets

BACKGROUND

The physiological balance between bone resorption and bone formation is now known to be mediated by a cascade of events parallel to the classic osteoblast-osteoclast interaction. Thus, osteoimmunology now encompasses the role played by other cell types, such as cytokines, lymphocytes and chemokines, in immunological responses and how they help modulate bone metabolism. All these factors have an impact on the RANK/RANKL/OPG pathway, which is the major pathway for the maturation and resorption activity of osteoclast precursor cells, responsible for osteoporosis development. Recently, immunoporosis has emerged as a new research area in osteoimmunology dedicated to the immune system's role in osteoporosis.

METHODS

The first part of this review presents theoretical concepts on the factors involved in the skeletal system and osteoimmunology. Secondly, existing treatments and novel therapeutic approaches to treat osteoporosis are summarized. These were selected from to the most recent studies published on PubMed containing the term osteoporosis. All data relate to the results of in vitro and in vivo studies on the osteoimmunological system of humans, mice and rats.

FINDINGS

Treatments for osteoporosis can be classified into two categories. They either target osteoclastogenesis inhibition (denosumab, bisphosphonates), or they aim to restore the number and function of osteoblasts (romozumab, abaloparatide). Even novel therapies, such as resolvins, gene therapy, and mesenchymal stem cell transplantation, fall within this classification system.

CONCLUSION

This review presents alternative pathways in the pathophysiology of osteoporosis, along with some recent therapeutic breakthroughs to restore bone homeostasis.

Why the Orientational Mobility in Arginine and Lysine Spacers of Peptide Dendrimers Designed for Gene Delivery Is Different?

New peptide dendrimer with Lys-2Arg repeating units was recently studied experimentally by NMR (RSC Advances, 2019, 9, 18018) and tested as gene carrier successfully (Int. J. Mol. Sci., 2020, 21, 3138). The unusual slowing down of the orientational mobility of 2Arg spacers in this dendrimer was revealed. It has been suggested that this unexpected behavior is caused by the Arg-Arg pairing effect in water, which leads to entanglements between dendrimer branches. In this paper, we determine the reason for this slowing down using atomistic molecular dynamics simulation of this dendrimer. We present that the structural properties of Lys-2Arg dendrimer are close to those of the Lys-2Lys dendrimer at all temperatures (Polymers, 2020, 12, 1657). However, the orientational mobility of the H-H vector in CH2-N groups of 2Arg spacers in Lys-2Arg dendrimer is significantly slower than the mobility of the same vector in the Lys-2Lys dendrimer. This result is in agreement with the recent NMR experiments for the same systems. We revealed that this difference is not due to the arginine-arginine pairing, but is due to the semiflexibility effect associated with the different contour length from CH2-N group to the end of the side arginine or lysine segment in spacers.

Safety profile of the transcription factor EB (TFEB)-based gene therapy through intracranial injection in mice

Transcription factor EB (TFEB)-based gene therapy is a promising therapeutic strategy in treating neurodegenerative diseases by promoting autophagy/lysosome-mediated degradation and clearance of misfolded proteins that contribute to the pathogenesis of these diseases. However, recent findings have shown that TFEB has proinflammatory properties, raising the safety concerns about its clinical application. To investigate whether TFEB induces significant inflammatory responses in the brain, male C57BL/6 mice were injected with phosphate-buffered saline (PBS), adeno-associated virus serotype 8 (AAV8) vectors overexpressing mouse TFEB (pAAV8-CMV-mTFEB), or AAV8 vectors expressing green fluorescent proteins (GFPs) in the barrel cortex. The brain tissue samples were collected at 2 months after injection. Western blotting and immunofluorescence staining showed that mTFEB protein levels were significantly increased in the brain tissue samples of mice injected with mTFEB-overexpressing vectors compared with those injected with PBS or GFP-overexpressing vectors. pAAV8-CMV-mTFEB injection resulted in significant elevations in the mRNA and protein levels of lysosomal biogenesis indicators in the brain tissue samples. No significant changes were observed in the expressions of GFAP, Iba1, and proinflammation mediators in the pAAV8-CMV-mTFEB-injected brain compared with those in the control groups. Collectively, our results suggest that AAV8 successfully mediates mTFEB overexpression in the mouse brain without inducing apparent local inflammation, supporting the safety of TFEB-based gene therapy in treating neurodegenerative diseases.

Viral Vector-Based Melanoma Gene Therapy

Gene therapy applications of oncolytic viruses represent an attractive alternative for cancer treatment. A broad range of oncolytic viruses, including adenoviruses, adeno-associated viruses, alphaviruses, herpes simplex viruses, retroviruses, lentiviruses, rhabdoviruses, reoviruses, measles virus, Newcastle disease virus, picornaviruses and poxviruses, have been used in diverse preclinical and clinical studies for the treatment of various diseases, including colon, head-and-neck, prostate and breast cancer as well as squamous cell carcinoma and glioma. The majority of studies have focused on immunotherapy and several drugs based on viral vectors have been approved. However, gene therapy for malignant melanoma based on viral vectors has not been utilized to its full potential yet. This review represents a summary of the achievements of preclinical and clinical studies using viral vectors, with the focus on malignant melanoma.

Anti-ageing gene therapy: Not so far away?

Improving healthspan is the main objective of anti-ageing research. Currently, innovative gene therapy-based approaches seem to be among the most promising for preventing and treating chronic polygenic pathologies, including age-related ones. The gene-based therapy allows to modulate the genome architecture using both direct (e.g., by gene editing) and indirect (e.g., by viral or non-viral vectors) approaches. Nevertheless, considering the extraordinary complexity of processes involved in ageing and ageing-related diseases, the effectiveness of these therapeutic options is often unsatisfactory and limited by their side-effects. Thus, clinical implementation of such applications is certainly a long-time process that will require many translation phases for addressing challenges. However, after overcoming these issues, their implementation in clinical practice may obviously provide new possibilities in anti-ageing medicine. Here, we review and discuss recent advances in this rapidly developing research field.

Recent Advances in the Development of Bio-Reducible Polymers for Efficient Cancer Gene Delivery Systems

Gene therapy is the unique method for the use of genetic materials such as Messenger ribonucleic acid (mRNA), plasmid deoxyribonucleic acid (pDNA), and small interfering ribonucleic acid (siRNA) into specific host-cells for the treatment of inherited disorders in any diseases. The successful way to utilize the gene therapy is to develop the efficient cancer gene delivery systems. In this paper, the successful and efficient gene delivery systems are briefly reviewed on the basis of bio-reducible polymeric systems for cancer therapy. The viral gene delivery systems such as RNA-based viral and DNA-based viral vectors are also discussed. The development of bio-reducible polymer for gene delivery system has briefly discussed for the efficient cancer gene delivery of viral vectors and non-viral vectors.

Recent advances in the development of gene delivery systems

Background

Gene delivery systems are essentially necessary for the gene therapy of human genetic diseases. Gene therapy is the unique way that is able to use the adjustable gene to cure any disease. The gene therapy is one of promising therapies for a number of diseases such as inherited disorders, viral infection and cancers. The useful results of gene delivery systems depend open the adjustable targeting gene delivery systems. Some of successful gene delivery systems have recently reported for the practical application of gene therapy.

Main body

The recent developments of viral gene delivery systems and non-viral gene delivery systems for gene therapy have briefly reviewed. The viral gene delivery systems have discussed for the viral vectors based on DNA, RNA and oncolytic viral vectors. The non-viral gene delivery systems have also treated for the physicochemical approaches such as physical methods and chemical methods. Several kinds of successful gene delivery systems have briefly discussed on the bases of the gene delivery systems such as cationic polymers, poly(L-lysine), polysaccharides, and poly(ethylenimine)s.

Conclusion

The goal of the research for gene delivery system is to develop the clinically relevant vectors such as viral and non-viral vectors that use to combat elusive diseases such as AIDS, cancer, Alzheimer, etc. Next step research will focus on advancing DNA and RNA molecular technologies to become the standard treatment options in the clinical area of biomedical application.

Liver-specific Gene Delivery Using Engineered Virus-Like Particles of Hepatitis E Virus

Virus-like particles (VLPs) possess great potential for organ-specific transport of therapeutic agents due to their central cavity surrounded by viral capsid proteins and similar tropism to their original viruses. The N-terminal truncated second open reading frame (Nt-ORF2) of the hepatotropic hepatitis E virus (HEV) forms VLPs via self-assembly. In the present study, we investigated whether HEV-LPs could deliver foreign genes specifically to the liver. HEV-LPs were obtained from Nt-ORF2 expression in Huh7 cells that were transduced with recombinant baculoviruses and purified by continuous density gradient centrifugation. The purified HEV-LPs efficiently penetrated liver-derived cell lines and the liver tissues. To evaluate HEV-LPs as gene delivery tools, we encapsulated foreign plasmids in HEV-LPs with disassembly/reassembly systems. Green fluorescence was detected at higher frequency in liver-derived Huh7 cells treated with HEV-LPs bearing GFP-encoding plasmids than in control cells. Additionally, HEV-LPs bearing Bax-encoding plasmids induced apoptotic signatures in Huh7 cells. In conclusion, HEV-LPs produced in mammalian cells can encapsulate foreign genes in their central cavity and specifically transport these genes to liver-derived cells, where they are expressed. The present study could contribute to advances in liver-targeted gene therapy.

The influence of gradient and statistical arrangements of guanidinium or primary amine groups in poly(methacrylate) copolymers on their DNA binding affinity

Herein, we report the first gradient guanidinium containing cationic copolymers and investigate their binding ability to plasmid DNA (pDNA).

Design of PEI-conjugated bio-reducible polymer for efficient gene delivery

The poly(cystaminebis(acrylamide)-diaminohexane) (poly(CBA-DAH)) was designed previously as a bio-reducible efficient gene delivery carrier. However, the high weight ratio required to form the polyplexes between poly(CBA-DAH) with pDNA is still a problem that needs to be addressed. To solve this problem and increase the transfection efficiency, poly(ethylenimine) (PEI, 1.8 kDa) was conjugated to poly(CBA-DAH) via disulfide bond. The PEI conjugated poly(CBA-DAH) (PCDP) can bind with pDNA at a very low weight ratio of 0.5 and above, like PEI 25 kDa, and form the polyplexes with nano-size (102-128 nm) and positive surface charge (27-34 mV). PCDP and PCDP polyplexes had negligible cytotoxicity and indicated similar or better cellular uptake than the comparison groups such as PEI 25 kDa and Lipofectamine® polyplexes. To confirm the transfection efficiency, the plasmid DNA (pDNA) encoded with the luciferase reporter gene (gWiz-Luc) and green fluorescent protein reporter gene (GFP) were used and treated with PCDP into the A549, Huh-7, and Mia PaCa-2 cells. PCDP/pDNA polyplexes showed highest transfection efficiency in all tested cell lines. In the luciferase assay, PCDP polyplexes showed 10.2 times higher gene transfection efficiency than Lipofectamine® polyplexes in mimic in vivo conditions (30% FBS, A549 cells). The VEGF siRNA expressing plasmid (pshVEGF), which is constructed as a therapeutic gene by our previous work, was delivered by PCDP into the cancer cells. The VEGF gene expression of PCDP/pshVEGF polyplexes was dramatically lower than control and the VEGF gene silencing efficiencies of PCDP/pshVEGF (w/w; 10/1) polyplexes were 54% (A549 cells), 77% (Huh-7 cells), and 66% (Mia PaCa-2 cells). In addition, PCDP/pshVEGF had reduced cell viability rates of about 31% (A549 cells), 39% (Huh-7 cells), and 42% (Mia PaCa-2 cells) and showed better results than all comparison groups. In the transfection efficiency and VEGF silencing assay, PCDP polyplexes showed better results than poly(CBA-DAH) at 4-fold lower weight ratio. The data of all experiments demonstrate that the synthesized PCDP could be used for efficient gene delivery and could be widely applied.

Plant virus nanoparticles: Novel and robust nanocarriers for drug delivery and imaging

Nanoparticles have been gained much attention for biomedical applications. A promising type of nanocarriers is viral nanoparticles (VNPs) which are natural bio-nanomaterials derived from different type of viruses. Amongst VNPs, plant VNPs present several pros over general nanoparticles such as liposomes, dendrimers or quantum dots. Some of these advantages include: degradability, safety for human, known structures to atomic level, possibility of attaching ligand with vigorous control on structure, availability for genetic and chemical manipulations and very flexible methods to prepare them. Variety of plant viruses have been modified by chemical and genetic modification of their inner cavities and their outer-surfaces. These modifications provide suitable sites for attachment of markers and drug molecules for vascular imaging and tumor targeting. In this review a brief description of plant virus nanoparticles and their biomedical applications especially in drug delivery is provided. The methods of loading cargos in these VNPs and their final biofate are also reviewed.

Cancer terminator viruses (CTV): A better solution for viral-based therapy of cancer

In principle, viral gene therapy holds significant potential for the therapy of solid cancers. However, this promise has not been fully realized and systemic administration of viruses has not proven as successful as envisioned in the clinical arena. Our research is focused on developing the next generation of efficacious viruses to specifically treat both primary cancers and a major cause of cancer lethality, metastatic tumors (that have spread from a primary site of origin to other areas in the body and are responsible for an estimated 90% of cancer deaths). We have generated a chimeric tropism-modified type 5 and 3 adenovirus that selectively replicates in cancer cells and simultaneously produces a secreted anti-cancer toxic cytokine, melanoma differentiation associated gene-7/Interleukin-24 (mda-7/IL-24), referred to as a Cancer Terminator Virus (CTV) (Ad.5/3-CTV). In preclinical animal models, injection into a primary tumor causes selective cell death and therapeutic activity is also observed in non-injected distant tumors, that is, "bystander anti-tumor activity." To enhance the impact and therapeutic utility of the CTV, we have pioneered an elegant approach in which viruses are encapsulated in microbubbles allowing "stealth delivery" to tumor cells that when treated with focused ultrasound causes viral release killing tumor cells through viral replication, and producing and secreting MDA-7/IL-24, which stimulates the immune system to attack distant cancers, inhibits tumor angiogenesis and directly promotes apoptosis in distant cancer cells. This strategy is called UTMD (ultrasound-targeted microbubble-destruction). This novel CTV and UTMD approach hold significant promise for the effective therapy of primary and disseminated tumors.

Poly(l-lysine)-Coated Liquid Crystal Droplets for Sensitive Detection of DNA and Their Applications in Controlled Release of Drug Molecules

Interactions between DNA and adsorbed poly(l-lysine) (PLL) on liquid crystal (LC) droplets were investigated using polarizing optical microcopy and epi-fluorescence microscopy. Earlier, we demonstrated that adsorption of PLL to the LC/aqueous interface resulted in homeotropic orientation of the LC and thus exhibited a radial configuration of the LC confined within the droplets. Subsequent adsorption of DNA (single-stranded DNA/double-stranded DNA) at PLL-coated LC droplets was found to trigger an LC reorientation within the droplets, leading to preradial/bipolar configuration of those droplets. To our surprise, subsequent exposure of complementary ssDNA to ssDNA/adsorbed PLL-modified LC droplets did not cause the LC reorientation. This is likely due to the formation of polyplexes (DNA-PLL complex) as confirmed by fluorescence microscopy and atomic force microscopy. In addition, dsDNA-adsorbed PLL droplets have been found to be effectively useful to displace (controlled release) propidium iodide (a model drug) encapsulated within dsDNA over time. These observations suggest the potential for a label-free droplet-based LC detection system that can respond to DNA and may provide a simple method to develop DNA-based drug nanocarriers.

HIF1A overexpression using cell-penetrating DNA-binding protein induces angiogenesis in vitro and in vivo

Hypoxia-inducible factor-1 alpha (HIF1A) is an important transcription factor for angiogenesis. Recent studies have used the protein transduction domain (PTD) to deliver genes, but the PTD has not been used to induce the expression of HIF1A. This study aimed at using a novel PTD (Hph-1-GAL4; ARVRRRGPRR) to overexpress the HIF1A and identify the effects on angiogenesis in vitro and in vivo. Overexpression of HIF1A was induced using Hph-1-GAL4 in human umbilical vein/vascular endothelium cells (HUVEC). The expression levels of genes were analyzed by the quantitative real-time polymerase chain reaction (qPCR) after 2 and 4 days, respectively. An in vitro tube formation was performed using Diff-Quik staining. HIF1A and Hph-1-GAL4 were injected subcutaneously into the ventral area of each 5-week-old mouse. All of the plugs were retrieved after 1 week, and the gene expression levels were evaluated by qPCR. Each Matrigel plug was evaluated using the hemoglobin assay and hematoxylin and eosin (HE) staining. The expression levels of HIF1A and HIF1A target genes were significantly higher in HIF1A-transfected HUVEC than in control HUVEC in vitro. In the in vivo Matrigel plug assay, the amount of hemoglobin was significantly higher in the HIF1A-treatment group than in the PBS-treatment group. Blood vessels were identified in the HIF1A-treatment group. The expression levels of HIF1A, vascular endothelial growth factor (Vegf), and Cd31 were significantly higher in the HIF1A-treatment group than in the PBS-treatment group. These findings suggest that using Hph-1-G4D to overexpress HIF1A might be useful for transferring genes and regenerating tissues.

Puromycin-resistant lentiviral control shRNA vector, pLKO.1 induces unexpected cellular differentiation of P19 embryonic stem cells

RNA silencing is used as a common method for investigating loss-of-function effects of genes of interest. In mammalian cells, RNA interference (RNAi) or RNA silencing can be achieved by transient siRNA (small or short interfering RNA) transfection or by stable shRNA (short hairpin RNA) systems. Various vectors are used for efficient delivery of shRNA. Lentiviral vectors offer an efficient delivery system for stable and long-term expression of the shRNA in mammalian cells. The widely used lentiviral pLKO.1 plasmid vector is very popular in RNAi studies. A large RNAi database, a TRC (the RNAi Consortium) library, was established based on the pLKO.1-TRC plasmid vector. This plasmid (also called pLKO.1-puro) has a puromycin-resistant gene for selection in mammalian cells along with designs for generating lentiviral particles as well for RNA silencing. While using the pLKO.1-puro TRC control shRNA plasmid for transfection in murine P19 embryonic stem (ES) cells, it was unexpectedly discovered that this plasmid vector induced robust endodermal differentiation. Since P19 ES cells are pluripotent and respond to external stimuli that have the potential to alter the phenotype and thus its stemness, other cell types used in RNA silencing studies do not display the obvious effect and therefore, may affect experiments in subtle ways that would go undetected. This study for the first time provides evidence that raises concern and warrants extreme caution while using the pLKO.1-puro control shRNA vector because of its unexpected non-specific effects on cellular integrity.

Insulin-Like Growth Factor I (IGF-I) Expressed from an AAV1 Vector Leads to a Complete Reversion of Liver Cirrhosis in Rats

IGF-I modulates liver tissue homeostasis. It is produced by hepatocytes and signals within the liver through IGF-I receptor expressed on hepatic stellate cells (HSCs). Liver cirrhosis is characterized by marked IGF-I deficiency. Here we compared the effect of two different gene therapy vectors encoding IGF-I as a potential treatment for cirrhotic patients. Rats with carbon tetrachloride-induced liver cirrhosis were treated with controls or with adeno-associated virus 1 (AAV) or simian virus 40 (SV40) vectors expressing IGF-I (AAVIGF-I or SVIGF-I) and molecular and histological studies were performed at 4 days, 8 weeks and 16 weeks. Increased levels of IGF-I were observed in the liver as soon as 4 days after vector administration. Control cirrhotic rats showed increased hepatic expression of pro-inflammatory and pro-fibrogenic factors including transforming growth factor beta (TGFβ), tumor necrosis factor-alpha (TNFα), connective tissue growth factor (CTGF), and vascular endothelial growth factor (VEGF) together with upregulation of α-smooth muscle actin (αSMA), a marker of HSC activation. In IGF-I-treated rats the levels of all these molecules were similar to those of healthy controls by week 8 post-therapy. Of note, the decline of TGFβ, CTGF, VEGF and αSMA expression was more rapid in AAVIGF-I treated animals reaching statistical significance by day 4 post-therapy. IGF-I-treated rats showed similar improvement of liver function tests in parallel with upregulation of hepatocyte nuclear factor 4α (HNF4α), a factor that promotes hepatocellular differentiation. A significant decrease of liver fibrosis, accompanied by upregulation of the hepatoprotective and anti-fibrogenic hepatocyte growth factor (HGF), occurred in all IGF-I-treated rats but complete reversal of liver cirrhosis took place only in AAVIGF-I group. Therefore, AAVIGF-I reverts liver cirrhosis in rats, a capability which deserves clinical testing.

Pharmacodynamics of anti-HIV gene therapy using viral vectors and targeted endonucleases

OBJECTIVES

A promising curative approach for HIV is to use designer endonucleases that bind and cleave specific target sequences within latent genomes, resulting in mutations that render the virus replication incompetent. We developed a mathematical model to describe the expression and activity of endonucleases delivered to HIV-infected cells using engineered viral vectors in order to guide dose selection and predict therapeutic outcomes.

METHODS

We developed a mechanistic model that predicts the number of transgene copies expressed at a given dose in individual target cells from fluorescence of a reporter gene. We fitted the model to flow cytometry datasets to determine the optimal vector serotype, promoter and dose required to achieve maximum expression.

RESULTS

We showed that our model provides a more accurate measure of transduction efficiency compared with gating-based methods, which underestimate the percentage of cells expressing reporter genes. We identified that gene expression follows a sigmoid dose-response relationship and that the level of gene expression saturation depends on vector serotype and promoter. We also demonstrated that significant bottlenecks exist at the level of viral uptake and gene expression: only ∼1 in 220 added vectors enter a cell and, of these, depending on the dose and promoter used, between 1 in 15 and 1 in 1500 express transgene.

CONCLUSIONS

Our model provides a quantitative method of dose selection and optimization that can be readily applied to a wide range of other gene therapy applications. Reducing bottlenecks in delivery will be key to reducing the number of doses required for a functional cure.

Solid Lipid Nanoparticles and Nanostructured Lipid Carriers: Structure, Preparation and Application

Lipid nanoparticles (LNPs) have attracted special interest during last few decades. Solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) are two major types of Lipid-based nanoparticles. SLNs were developed to overcome the limitations of other colloidal carriers, such as emulsions, liposomes and polymeric nanoparticles because they have advantages like good release profile and targeted drug delivery with excellent physical stability. In the next generation of the lipid nanoparticle, NLCs are modified SLNs which improve the stability and capacity loading. Three structural models of NLCs have been proposed. These LNPs have potential applications in drug delivery field, research, cosmetics, clinical medicine, etc. This article focuses on features, structure and innovation of LNPs and presents a wide discussion about preparation methods, advantages, disadvantages and applications of LNPs by focusing on SLNs and NLCs.

Predictors of hepatitis B cure using gene therapy to deliver DNA cleavage enzymes: a mathematical modeling approach

Most chronic viral infections are managed with small molecule therapies that inhibit replication but are not curative because non-replicating viral forms can persist despite decades of suppressive treatment. There are therefore numerous strategies in development to eradicate all non-replicating viruses from the body. We are currently engineering DNA cleavage enzymes that specifically target hepatitis B virus covalently closed circular DNA (HBV cccDNA), the episomal form of the virus that persists despite potent antiviral therapies. DNA cleavage enzymes, including homing endonucleases or meganucleases, zinc-finger nucleases (ZFNs), TAL effector nucleases (TALENs), and CRISPR-associated system 9 (Cas9) proteins, can disrupt specific regions of viral DNA. Because DNA repair is error prone, the virus can be neutralized after repeated cleavage events when a target sequence becomes mutated. DNA cleavage enzymes will be delivered as genes within viral vectors that enter hepatocytes. Here we develop mathematical models that describe the delivery and intracellular activity of DNA cleavage enzymes. Model simulations predict that high vector to target cell ratio, limited removal of delivery vectors by humoral immunity, and avid binding between enzyme and its DNA target will promote the highest level of cccDNA disruption. Development of de novo resistance to cleavage enzymes may occur if DNA cleavage and error prone repair does not render the viral episome replication incompetent: our model predicts that concurrent delivery of multiple enzymes which target different vital cccDNA regions, or sequential delivery of different enzymes, are both potentially useful strategies for avoiding multi-enzyme resistance. The underlying dynamics of cccDNA persistence are unlikely to impact the probability of cure provided that antiviral therapy is given concurrently during eradication trials. We conclude by describing experiments that can be used to validate the model, which will in turn provide vital information for dose selection for potential curative trials in animals and ultimately humans.

Innovative new approaches are being developed to eradicate viral infections that until recently were considered incurable. We are interested in engineering DNA cleavage enzymes that can cut and incapacitate persistent viruses. One hurdle is that these enzymes must be delivered to infected cells as genes within viral vectors that are not harmful to humans. In this paper, we developed a series of equations that describe the delivery of these enzymes to their intended targets, as well the activity of DNA cutting within the cell. While our mathematical model is catered towards hepatitis B virus infection, it is widely applicable to other infections such as HIV, as well as oncologic and metabolic diseases characterized by aberrant gene expression. Certain enzymes may bind DNA more avidly than others, while different enzymes may also bind cooperatively if targeted to different regions of viral DNA. We predict that such enzymes, if delivered efficiently to a high proportion of infected cells, will be critical to increase the probability of cure. We also demonstrate that our equations will serve as a useful tool for identifying the most important features of a curative regimen, and ultimately for guiding clinical trial dosing schedules to ensure hepatitis B eradication with the smallest number of possible doses.

Homologous recombination-based adenovirus vector system for tumor cell-specific gene delivery

Cancer gene therapy requires tumor-specific delivery and expression of a transgene to maximize antitumor efficacy and minimize side effects. In this study, we developed a new tumor-targeting, homologous recombination-based adenovirus vector system, HRAVS. HRAVS is composed of two adenovirus vectors, Ad.CMV.IR containing reverse sequence (IR) and a CMV promoter and Ad.IR.EGFP comprising the report gene EGFP and IR. For improved viral DNA replication and transgene expression, the E1a gene was added to HRAVS to generate the enhanced HRAVS, EHRAVS, which consists of Ad.CMV.IR and Ad.IR.EGFP/E1a. The optimal vector composition ratio of Ad.CMV.IR to Ad.IR.EGFP or Ad.IR.EGFP/E1a was identified as 30:70 based on EGFP expression efficiency in tumor cells. The transgene expression of HRAVS and EHRAVS was efficiently and specifically activated in tumor cells only and not in normal cells. Moreover, compared with HRAVS, EHRAVS infection led to higher virus yields and transgene expression and higher toxicity to tumor cells, and these results could be related to the involvement of E1a genes. The results in present study suggest the need for in vivo antitumor study using these new dual-Ad vector systems based on the homologous recombination.

Viral and nonviral delivery systems for gene delivery

Gene therapy is the process of introducing foreign genomic materials into host cells to elicit a therapeutic benefit. Although initially the main focus of gene therapy was on special genetic disorders, now diverse diseases with different patterns of inheritance and acquired diseases are targets of gene therapy. There are 2 major categories of gene therapy, including germline gene therapy and somatic gene therapy. Although germline gene therapy may have great potential, because it is currently ethically forbidden, it cannot be used; however, to date human gene therapy has been limited to somatic cells. Although numerous viral and nonviral gene delivery systems have been developed in the last 3 decades, no delivery system has been designed that can be applied in gene therapy of all kinds of cell types in vitro and in vivo with no limitation and side effects. In this review we explain about the history of gene therapy, all types of gene delivery systems for germline (nuclei, egg cells, embryonic stem cells, pronuclear, microinjection, sperm cells) and somatic cells by viral [retroviral, adenoviral, adeno association, helper-dependent adenoviral systems, hybrid adenoviral systems, herpes simplex, pox virus, lentivirus, Epstein-Barr virus)] and nonviral systems (physical: Naked DNA, DNA bombardant, electroporation, hydrodynamic, ultrasound, magnetofection) and (chemical: Cationic lipids, different cationic polymers, lipid polymers). In addition to the above-mentioned, advantages, disadvantages, and practical use of each system are discussed.