Targeted transduction patterns in the mouse brain by lentivirus vectors pseudotyped with VSV, Ebola, Mokola, LCMV, or MuLV envelope proteins

Pseudotyped Viruses for Lyssavirus

Lyssaviruses, which belong to the family Rhabdoviridae, are enveloped and bullet-shaped ssRNA viruses with genetic diversity. All members of Lyssavirus genus are known to infect warm-blooded animals and cause the fatal disease rabies. The rabies virus (RABV) in lyssavirus is the major pathogen to cause fatal rabies. The pseudotyped RABV is constructed to study the biological functions of G protein and evaluation of anti-RABV products including vaccine-induced antisera, rabies immunoglobulins (RIG), neutralizing mAbs, and other antiviral inhibitors. In this chapter, we focus on RABV as a representative and describe the construction of RABV G protein bearing pseudotyped virus and its applications. Other non-RABV lyssaviruses are also included.

Stem Cell-based and Advanced Therapeutic Modalities for Parkinson's Disease: A Risk-effectiveness Patient-centered Analysis

Treatment of Parkinson's disease (PD), the second most prevalent neurodegenerative disorder, is currently considered a challenging issue since it causes substantial disability, poor quality of life, and mortality. Despite remarkable progress in advanced conventional therapeutic interventions, the global burden of the disease has nearly doubled, prompting us to assess the riskeffectiveness of different treatment modalities. Each protocol could be considered as the best alternative treatment depending on the patient's situation. Prescription of levodopa, the most effective available medicine for this disorder, has been associated with many complications, i.e., multiple episodes of "off-time" and treatment resistance. Other medications, which are typically used in combination with levodopa, may have several adverse effects as well. As a result, the therapies that are more in line with human physiology and make the least interference with other pathways are worth investigating. On the other hand, remaining and persistent symptoms after therapy and the lack of effective response to the conventional approaches have raised expectations towards innovative alternative approaches, such as stem cell-based therapy. It is critical to not overlook the unexplored side effects of innovative approaches due to the limited number of research. In this review, we aimed to compare the efficacy and risk of advanced therapies with innovative cell-based and stemcell- based modalities in PD patients. This paper recapitulated the underlying factors/conditions, which could lead us to more practical and established therapeutic outcomes with more advantages and few complications. It could be an initial step to reconsider the therapeutic blueprint for patients with Parkinson's disease.

Pseudotyped lentiviral vectors: Ready for translation into targeted cancer gene therapy?

Gene therapy holds great promise for curing cancer by editing the deleterious genes of tumor cells, but the lack of vector systems for efficient delivery of genetic material into specific tumor sites in vivo has limited its full therapeutic potential in cancer gene therapy. Over the past two decades, increasing studies have shown that lentiviral vectors (LVs) modified with different glycoproteins from a donating virus, a process referred to as pseudotyping, have altered tropism and display cell-type specificity in transduction, leading to selective tumor cell killing. This feature of LVs together with their ability to enable high efficient gene delivery in dividing and non-dividing mammalian cells in vivo make them to be attractive tools in future cancer gene therapy. This review is intended to summarize the status quo of some typical pseudotypings of LVs and their applications in basic anti-cancer studies across many malignancies. The opportunities of translating pseudotyped LVs into clinic use in cancer therapy have also been discussed.

Boosting antitumor response with PSMA-targeted immunomodulatory VLPs, harboring costimulatory TNFSF ligands and GM-CSF cytokine

Therapeutic strategies based on immunomodulation have improved cancer therapy. Most approaches target co-stimulatory pathways or the inhibition of immunosuppressive mechanisms, to enhance immune response and overcome the immune tolerance of tumors. Here, we propose a novel platform to deliver targeted immunomodulatory signaling, enhancing antitumor response. The platform is based on virus-like particles derived from lentiviral capsids. These particles may be engineered to harbor multifunctional ligands on the surface that drive tropism to the tumor site and deliver immunomodulatory signaling, boosting the antitumor response. We generated virus-like particles harboring a PSMA-ligand, TNFSF co-stimulatory ligands 4-1BBL or OX40L, and a membrane-anchored GM-CSF cytokine. The virus-like particles are driven to PSMA-expressing tumors and deliver immunomodulatory signaling from the TNFSF surface ligands and the anchored GM-CSF, inducing T cell proliferation, inhibition of regulatory T cells, and potentiating elimination of tumor cells. The PSMA-targeted particles harboring immunomodulators enhanced antitumor activity in immunocompetent challenged mice and may be explored as a potential tool for cancer immunotherapy.

Direct neuronal reprogramming: Fast forward from new concepts toward therapeutic approaches

Differentiated cells have long been considered fixed in their identity. However, about 20 years ago, the first direct conversion of glial cells into neurons in vitro opened the field of "direct neuronal reprogramming." Since then, neuronal reprogramming has achieved the generation of fully functional, mature neurons with remarkable efficiency, even in diseased brain environments. Beyond their clinical implications, these discoveries provided basic insights into crucial mechanisms underlying conversion of specific cell types into neurons and maintenance of neuronal identity. Here we discuss such principles, including the importance of the starter cell for shaping the outcome of neuronal reprogramming. We further highlight technical concerns for in vivo reprogramming and propose a code of conduct to avoid artifacts and pitfalls. We end by pointing out next challenges for development of less invasive cell replacement therapies for humans.

Hyperspectral image processing for the identification and quantification of lentiviral particles in fluid samples

Optical spectroscopic techniques have been commonly used to detect the presence of biofilm-forming pathogens (bacteria and fungi) in the agro-food industry. Recently, near-infrared (NIR) spectroscopy revealed that it is also possible to detect the presence of viruses in animal and vegetal tissues. Here we report a platform based on visible and NIR (VNIR) hyperspectral imaging for non-contact, reagent free detection and quantification of laboratory-engineered viral particles in fluid samples (liquid droplets and dry residue) using both partial least square-discriminant analysis and artificial feed-forward neural networks. The detection was successfully achieved in preparations of phosphate buffered solution and artificial saliva, with an equivalent pixel volume of 4 nL and lowest concentration of 800 TU·\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu$$\end{document}μL⁻¹. This method constitutes an innovative approach that could be potentially used at point of care for rapid mass screening of viral infectious diseases and monitoring of the SARS-CoV-2 pandemic.

Lentiviral Vector Bioprocessing

Lentiviral vectors (LVs) are potent tools for the delivery of genes of interest into mammalian cells and are now commonly utilised within the growing field of cell and gene therapy for the treatment of monogenic diseases and adoptive therapies such as chimeric antigen T-cell (CAR-T) therapy. This is a comprehensive review of the individual bioprocess operations employed in LV production. We highlight the role of envelope proteins in vector design as well as their impact on the bioprocessing of lentiviral vectors. An overview of the current state of these operations provides opportunities for bioprocess discovery and improvement with emphasis on the considerations for optimal and scalable processing of LV during development and clinical production. Upstream culture for LV generation is described with comparisons on the different transfection methods and various bioreactors for suspension and adherent producer cell cultivation. The purification of LV is examined, evaluating different sequences of downstream process operations for both small- and large-scale production requirements. For scalable operations, a key focus is the development in chromatographic purification in addition to an in-depth examination of the application of tangential flow filtration. A summary of vector quantification and characterisation assays is also presented. Finally, the assessment of the whole bioprocess for LV production is discussed to benefit from the broader understanding of potential interactions of the different process options. This review is aimed to assist in the achievement of high quality, high concentration lentiviral vectors from robust and scalable processes.

Development and Applications of Viral Vectored Vaccines to Combat Zoonotic and Emerging Public Health Threats

Vaccination is arguably the most cost-effective preventative measure against infectious diseases. While vaccines have been successfully developed against certain viruses (e.g., yellow fever virus, polio virus, and human papilloma virus HPV), those against a number of other important public health threats, such as HIV-1, hepatitis C, and respiratory syncytial virus (RSV), have so far had very limited success. The global pandemic of COVID-19, caused by the SARS-CoV-2 virus, highlights the urgency of vaccine development against this and other constant threats of zoonotic infection. While some traditional methods of producing vaccines have proven to be successful, new concepts have emerged in recent years to produce more cost-effective and less time-consuming vaccines that rely on viral vectors to deliver the desired immunogens. This review discusses the advantages and disadvantages of different viral vaccine vectors and their general strategies and applications in both human and veterinary medicines. A careful review of these issues is necessary as they can provide important insights into how some of these viral vaccine vectors can induce robust and long-lasting immune responses in order to provide protective efficacy against a variety of infectious disease threats to humans and animals, including those with zoonotic potential to cause global pandemics.

Gene and Cell-Based Therapies for Parkinson's Disease: Where Are We?

Parkinson's disease (PD) is a neurodegenerative disorder that carries large health and socioeconomic burdens. Current therapies for PD are ultimately inadequate, both in terms of symptom control and in modification of disease progression. Deep brain stimulation and infusion therapies are the current mainstay for treatment of motor complications of advanced disease, but these have very significant drawbacks and offer no element of disease modification. In fact, there are currently no agents that are established to modify the course of the disease in clinical use for PD. Gene and cell therapies for PD are now being trialled in the clinic. These treatments are diverse and may have a range of niches in the management of PD. They hold great promise for improved treatment of symptoms as well as possibly slowing progression of the disease in the right patient group. Here, we review the current state of the art for these therapies and look to future strategies in this fast-moving field.

The stability of envelope-pseudotyped lentiviral vectors

Lentiviral vectors have become popular tools for stable genetic modification of mammalian cells. In some applications of lentiviral vector-transduced cells, infectious-lentiviral particles should be absent. Quantification of the free-vector particles that remain from the inoculum can be difficult. Therefore a formula was established that yields an estimation of the ‘Reduction Ratio.’ This ratio represents the loss of titer based on a number of vector-inactivating effects. In this study, we evaluated several parameters and assumptions that were used in the current formula. We generated new data on the stability and trypsin sensitivity of lentiviral vectors pseudotyped with eight heterologous envelope proteins and the loss of vectors by washing or passaging the cell cultures. Our data demonstrate that the loss of virus titer under the influence of trypsin as well as the half-life of the particles in tissue culture medium is dependent on the vector’s envelope protein. While VSV-G-envelope-pseudotyped particles were unsensitive to trypsin, the titer of vectors pseudotyped with other envelope proteins decreased 2–110-fold. The half-life in culture medium ranged from 8 to 40 h for the different envelope-pseudotyped vectors, with 35 h for VSV-G-envelope-pseudotyped vector particles. Additionally, we found that removal of the culture medium from Ø35 mm to Ø10 cm dishes reduces the amount of vector particles in the culture by 50-fold and 20-fold, respectively. Together these data can be used to more precisely estimate the maximum number of free lentiviral vector particles in cell cultures.

Optimized Pre-Clinical Grade Production of Two Novel Lentiviral Vector Pseudotypes for Lung Gene Delivery

Lung gene therapy requires efficient transduction of slow-replicating epithelia and stable expression of delivered transgenes in the respiratory tract. Lentiviral (LV) vectors have the ideal coding, expression, and transducing capacity required for gene therapy. A modified envelope glycoprotein from the Jaagsiekte Sheep Retrovirus, termed Jenv, is well suited for LV-mediated lung gene therapy due to its inherent lung tropism. Here, two novel Jenv-pseudotyped LVs that effectively transduce lung tissue and yield titers similar to the gold standard, vesicular stomatitis virus glycoprotein (VSVg)-pseudotyped LVs, were generated. As the concentration efficiency of LVs was found to depend on envelope pseudotype, a large-scale production method tailored for Jenv-pseudotyped LVs was developed and the most appropriate method of concentration was determined. In contrast to VSVg and Ebola virus glycoprotein-pseudotyped LVs, ultracentrifugation through a sucrose cushion drastically reduced the yield of Jenv LVs, whereas polyethylene glycol precipitation and tangential flow filtration (TFF) proved to be more suitable methods for concentrating Jenv LVs. Importantly, pressure during TFF was found to be crucial for increasing LV recovery. Finally, a unique mouse model was developed to test the suitability of these novel Jenv-pseudotyped LVs for use in lung gene therapy applications.

Emerging gene therapies for cystic fibrosis

Introduction: Cystic fibrosis (CF) remains a life-threatening genetic disease, with few clinically effective treatment options. Gene therapy and gene editing strategies offer the potential for a one-time CF cure, irrespective of the CFTR mutation class. Areas covered: We review emerging gene therapies and gene delivery strategies for the treatment of CF particularly viral and non-viral approaches with potential to treat CF. Expert opinion: It was initially anticipated that the challenge of developing a gene therapy for CF lung disease would be met relatively easily. Following early proof-of-concept clinical studies, CF gene therapy has entered a new era with innovative vector designs, approaches to subvert the humoral immune system and increase gene delivery and gene correction efficiencies. Developments include integrating adenoviral vectors, rapamycin-loaded nanoparticles, and lung-tropic lentiviral vectors. The characterization of novel cell types in the lung epithelium, including pulmonary ionocytes, may also encourage cell type-specific targeting for CF correction. We anticipate preclinical studies to further validate these strategies, which should pave the way for clinical trials. We also expect gene editing efficiencies to improve to clinically translatable levels, given advancements in viral and non-viral vectors. Overall, gene delivery technologies look more convincing in producing an effective CF gene therapy.

High-efficiency transduction of spinal cord motor neurons by intrauterine delivery of integration-deficient lentiviral vectors

Integration-deficient lentiviral vectors (IDLVs) are promising gene delivery tools that retain the high transduction efficiency of standard lentiviral vectors, yet fail to integrate as proviruses and are instead converted into episomal circles. These episomes are metabolically stable and support long-term expression of transgenes in non-dividing cells, exhibiting a decreased risk of insertional mutagenesis. We have embarked on an extensive study to compare the transduction efficiency of IDLVs pseudotyped with different envelopes (vesicular stomatitis, Rabies, Mokola and Ross River viral envelopes) and self-complementary adeno-associated viral vectors, serotype-9 (scAAV-9) in spinal cord tissues after intraspinal injection of mouse embryos (E16). Our results indicate that IDLVs can transduce motor neurons (MNs) at extremely high efficiency regardless of the envelope pseudotype while scAAV9 mediates gene delivery to ~ 40% of spinal cord motor neurons, with other non-neuronal cells also transduced. Long-term expression studies revealed stable gene expression at 7 months post-injection. Taken together, the results of this study indicate that IDLVs may be efficient tools for in utero cord transduction in therapeutic strategies such as for treatment of inherited early childhood neurodegenerative diseases.

How have retrovirus pseudotypes contributed to our understanding of viral entry?

Study of virus entry into host cells is important for understanding viral tropism and pathogenesis. Studying the entry of in vitro cultured viruses is not always practicable. Study of highly pathogenic viruses, viruses that do not grow in culture, and viruses that rapidly change phenotype in vitro can all benefit from alternative models of entry. Retrovirus particles can be engineered to display the envelope proteins of heterologous enveloped viruses. This approach, broadly termed ‘pseudotyping’, is an important technique for interrogating virus entry. In this perspective we consider how retrovirus pseudotypes have addressed these challenges and improved our understanding of the entry pathways of diverse virus species, including Ebolavirus, human immunodeficiency virus and hepatitis C virus.

CRISPR Epigenome Editing of AKAP150 in DRG Neurons Abolishes Degenerative IVD-Induced Neuronal Activation

Back pain is a major contributor to disability and has significant socioeconomic impacts worldwide. The degenerative intervertebral disc (IVD) has been hypothesized to contribute to back pain, but a better understanding of the interactions between the degenerative IVD and nociceptive neurons innervating the disc and treatment strategies that directly target these interactions is needed to improve our understanding and treatment of back pain. We investigated degenerative IVD-induced changes to dorsal root ganglion (DRG) neuron activity and utilized CRISPR epigenome editing as a neuromodulation strategy. By exposing DRG neurons to degenerative IVD-conditioned media under both normal and pathological IVD pH levels, we demonstrate that degenerative IVDs trigger interleukin (IL)-6-induced increases in neuron activity to thermal stimuli, which is directly mediated by AKAP and enhanced by acidic pH. Utilizing this novel information on AKAP-mediated increases in nociceptive neuron activity, we developed lentiviral CRISPR epigenome editing vectors that modulate endogenous expression of AKAP150 by targeted promoter histone methylation. When delivered to DRG neurons, these epigenome-modifying vectors abolished degenerative IVD-induced DRG-elevated neuron activity while preserving non-pathologic neuron activity. This work elucidates the potential for CRISPR epigenome editing as a targeted gene-based pain neuromodulation strategy.

Destination Brain: the Past, Present, and Future of Therapeutic Gene Delivery

Neurological diseases and disorders (NDDs) present a significant societal burden and currently available drug- and biological-based therapeutic strategies have proven inadequate to alleviate it. Gene therapy is a suitable alternative to treat NDDs compared to conventional systems since it can be tailored to specifically alter select gene expression, reverse disease phenotype and restore normal function. The scope of gene therapy has broadened over the years with the advent of RNA interference and genome editing technologies. Consequently, encouraging results from central nervous system (CNS)-targeted gene delivery studies have led to their transition from preclinical to clinical trials. As we shift to an exciting gene therapy era, a retrospective of available literature on CNS-associated gene delivery is in order. This review is timely in this regard, since it analyzes key challenges and major findings from the last two decades and evaluates future prospects of brain gene delivery. We emphasize major areas consisting of physiological and pharmacological challenges in gene therapy, function-based selection of a ideal cellular target(s), available therapy modalities, and diversity of viral vectors and nanoparticles as vehicle systems. Further, we present plausible answers to key questions such as strategies to circumvent low blood-brain barrier permeability and most suitable CNS cell types for targeting. We compare and contrast pros and cons of the tested viral vectors in the context of delivery systems used in past and current clinical trials. Gene vector design challenges are also evaluated in the context of cell-specific promoters. Key challenges and findings reported for recent gene therapy clinical trials, assessing viral vectors and nanoparticles are discussed from the perspective of bench to bedside gene therapy translation. We conclude this review by tying together gene delivery challenges, available vehicle systems and comprehensive analyses of neuropathogenesis to outline future prospects of CNS-targeted gene therapies.

A broadly protective therapeutic antibody against influenza B virus with two mechanisms of action

Influenza B virus (IBV) causes annual influenza epidemics around the world. Here we use an in vivo plasmablast enrichment technique to isolate a human monoclonal antibody, 46B8 that neutralizes all IBVs tested in vitro and protects mice against lethal challenge of all IBVs tested when administered 72 h post infection. 46B8 demonstrates a superior therapeutic benefit over Tamiflu and has an additive antiviral effect in combination with Tamiflu. 46B8 binds to a conserved epitope in the vestigial esterase domain of hemagglutinin (HA) and blocks HA-mediated membrane fusion. After passage of the B/Brisbane/60/2008 virus in the presence of 46B8, we isolated three resistant clones, all harbouring the same mutation (Ser301Phe) in HA that abolishes 46B8 binding to HA at low pH. Interestingly, 46B8 is still able to protect mice against lethal challenge of the mutant viruses, possibly owing to its ability to mediate antibody-dependent cellular cytotoxicity (ADCC).

Influenza B virus (IBV) co-circulates with influenza A virus to cause annual epidemics. Here, Chai et al. isolate a human monoclonal antibody that binds to a conserved epitope in the viral HA protein, neutralizes IBV strains in vitro, and protects mice against IBV infection.

Lentiviral Vectors Pseudotyped with Filoviral Glycoproteins

Pseudotyping lentivirus-based vectors is a strategy used to study conferred vector tropism and mechanisms of envelope glycoprotein function. Lentiviruses and filoviruses both assemble at the plasma membrane and have homotrimeric structural envelope glycoproteins that mediate both receptor binding and fusion. Such similarities help foster efficient pseudotyping. Importantly, filovirus glycoprotein pseudotyping of lentiviral vectors allows investigators to study virus entry at substantially less restrictive levels of biosafety containment than that required for wild-type filovirus work (biosafety level-2 vs. biosafety level-4, respectively). Standard lentiviral vector production involves transient transfection of viral component expression plasmids into producer cells, supernatant collection, and centrifuge concentration. Because the envelope glycoprotein expression plasmid is provided in trans, wild type or variant filoviral glycoproteins from marburgvirus or ebolavirus species may be used for pseudotyping and compared side-by-side. In this chapter we discuss the manufacture of pseudotyped lentiviral vector with an emphasis on small-scale laboratory grade production.

Pseudo-typed Semliki Forest virus delivers EGFP into neurons

Semliki Forest virus (SFV), a neurotropic virus, has been used to deliver heterologous genes into cells in vitro and in vivo. In this study, we constructed a reporter SFV4-FL-EGFP and found that it can deliver EGFP into neurons located at the injection site without disseminating throughout the brain. Lacking of the capsid gene of SFV4-FL-EGFP does not block its life cycle, while forming replication-competent virus-like particles (VLPs). These VLPs hold subviral genome by using the packaging sequence (PS) located within the nsP2 gene, and can transfer their genome into cells. In addition, we found that the G protein of vesicular stomatitis virus (VSVG) can package SFV subviral genome, which is consistent with the previous reports. The G protein of rabies virus (RVG) could also package SFV subviral genome. These pseudo-typed SFV can deliver EGFP gene into neurons. Taken together, these findings may be used to construct various SFV-based delivery systems for virological studies, gene therapy, and neural circuit labeling.

Introduction to Viral Vectors and Other Delivery Methods for Gene Therapy of the Nervous System

The use of gene therapy in neuroscience research has become common place in many laboratories across the world. However, contrary to common belief, the practical application of viral or non-viral gene therapy is not as straightforward as it may seem. All too often investigators see their experiments fail due to low-quality third-party vectors or due to a lack of knowledge regarding the proper use of these tools. For example, researchers often find themselves performing experiments using the wrong methodology (e.g., using the wrong type of vector or mishandling the vector to the point where the efficacy is significantly reduced) resulting in experiments that potentially fail to accurately answer a hypothesis, or the generation of irreproducible data. Thus, it is important for investigators that seek to utilize gene therapy approaches to gain a basic understanding of how to apply this technology. This includes understanding how to appropriately design and execute an experiment, understanding various delivery vehicles (e.g., what virus to use), delivery methods (e.g., systemic versus intracranial injections), what expression system to use, and the time course involved with a particular expression system. This chapter is intended to present an overview of this fundamental knowledge, providing the researcher with a decision tree upon which to build their gene therapy experiment.

Altering Entry Site Preference of Lentiviral Vectors into Neuronal Cells by Pseudotyping with Envelope Glycoproteins

A lentiviral vector system provides a powerful strategy for gene therapy trials against a variety of neurological and neurodegenerative disorders. Pseudotyping of lentiviral vectors with different envelope glycoproteins not only confers the neurotropism to the vectors, but also alters the preference of sites of vector entry into neuronal cells. One major group of lentiviral vectors is a pseudotype with vesicular stomatitis virus glycoprotein (VSV-G) that enters preferentially cell body areas (somata/dendrites) of neurons and transduces them. Another group contains lentiviral vectors pseudotyped with fusion envelope glycoproteins composed of different sets of rabies virus glycoprotein and VSV-G segments that enter predominantly axon terminals of neurons and are transported through axons retrogradely to their cell bodies, resulting in enhanced retrograde gene transfer. This retrograde gene transfer takes a considerable advantage of delivering the transgene into neuronal cell bodies situated in regions distant from the injection site of the vectors. The rational use of these two vector groups characterized by different entry mechanisms will further extend the strategy for gene therapy of neurological and neurodegenerative disorders.

Role of Enhanced Central Leptin Activity in a Scoliosis Model Created in Bipedal Amputated Mice

STUDY DESIGN

An experimental study to investigate the role of enhanced central leptin activity in a bipedal mouse scoliosis model.

OBJECTIVE

To investigate the influence of enhanced central leptin activity on the development of scoliosis in mice, and to support Burwell's hypothesis that central leptin dysfunction is involved in the etiopathogenesis of idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Significantly lower level of circulating leptin and higher level of soluble leptin receptor have been reported in adolescent idiopathic scoliosis compared with healthy adolescents, suggesting possible association between abnormal central leptin level and dysfunction.

METHODS

Amputation of forelimbs and tail was performed on 50 male C3H/HeJ mice at the age of 3 weeks. Then, the mice were randomly divided into 2 groups: Group A consisted of 25 mice treated with injection into the hypothalamus with lentivirus vectors that overexpressed leptin; and Group B involved the remaining 25 mice receiving intracerebral injection with the control vectors. Radiographs were obtained at 20th week to determine the presence of spinal deformity. The incidence of scoliosis and curve magnitude were compared between groups.

RESULTS

The body weight was initially found to be slightly lower in mice of Group A when compared with Group B. Significantly higher peripheral serum leptin level was found in leptin-overexpressing mice than control mice. Scoliosis developed in 23 mice of Group A (92%), with an average Cobb angle of 30.2°, and in 13 of Group B (52%), with an average Cobb angle of 18.4°, respectively. A higher incidence (P = 0.002) and more severe curve (P <0.001) were observed in Group A.

CONCLUSION

In this bipedal mouse scoliosis model, enhanced central leptin activity might not only increase the risk of developing a scoliosis, but also contribute to the progression of scoliosis.

LEVEL OF EVIDENCE

N/A.

Viral vaccines and their manufacturing cell substrates: New trends and designs in modern vaccinology

Vaccination is one of the most effective interventions in global health. The worldwide vaccination programs significantly reduced the number of deaths caused by infectious agents. A successful example was the eradication of smallpox in 1979 after two centuries of vaccination campaigns. Since the first variolation administrations until today, the knowledge on immunology has increased substantially. This knowledge combined with the introduction of cell culture and DNA recombinant technologies revolutionized vaccine design. This review will focus on vaccines against human viral pathogens, recent developments on vaccine design and cell substrates used for their manufacture. While the production of attenuated and inactivated vaccines requires the use of the respective permissible cell substrates, the production of recombinant antigens, virus‐like particles, vectored vaccines and chimeric vaccines requires the use – and often the development – of specific cell lines. Indeed, the development of novel modern viral vaccine designs combined with, the stringent safety requirements for manufacture, and the better understanding on animal cell metabolism and physiology are increasing the awareness on the importance of cell line development and engineering areas. A new era of modern vaccinology is arriving, offering an extensive toolbox to materialize novel and creative ideas in vaccine design and its manufacture.

CCN1, a Pro-Inflammatory Factor, Aggravates Psoriasis Skin Lesions by Promoting Keratinocyte Activation

Psoriasis is a common chronic skin disease characterized by epidermal hyperplasia and inflammation. The pathogenesis of psoriasis is multifactorial and is not fully understood. Here we demonstrate that CCN1 (also called Cyr61, which is short for cysteine-rich 61), an extracellular matrix protein that is also considered a pro-inflammatory factor, is highly expressed in the lesional skin of psoriasis patients, as well as in that of imiquimod (IMQ)- and IL-23-treated psoriasis-like mice. Then we show that blocking CCN1 function in vivo attenuates epidermal hyperplasia and inflammation in psoriasis-like mice. Further, in primary cultured normal human keratinocytes and HaCaT (human keratinocyte cell line) cells, CCN1 promotes keratinocyte activation, including the proliferation and expression of immune-related molecules. Finally, we observe that integrin α6β1 is the receptor of CCN1 in keratinocytes, and CCN1 stimulation activates the downstream phosphoinositide-3 kinase/Akt/NF-κB signaling pathway. Taken together, our findings reveal that CCN1 has a critical role in psoriasis pathogenesis. Moreover, as CCN1 is a secreted extracellular matrix (ECM) protein, our study also provides evidence that ECM, which is involved in psoriatic pathogenesis, could be a potent target for psoriasis treatment.

Gene transfer engineering for astrocyte-specific silencing in the CNS

Cell-type-specific gene silencing is critical to understand cell functions in normal and pathological conditions, in particular in the brain where strong cellular heterogeneity exists. Molecular engineering of lentiviral vectors has been widely used to express genes of interest specifically in neurons or astrocytes. However, we show that these strategies are not suitable for astrocyte-specific gene silencing due to the processing of small hairpin RNA (shRNA) in a cell. Here we develop an indirect method based on a tetracycline-regulated system to fully restrict shRNA expression to astrocytes. The combination of Mokola-G envelope pseudotyping, glutamine synthetase promoter and two distinct microRNA target sequences provides a powerful tool for efficient and cell-type-specific gene silencing in the central nervous system. We anticipate our vector will be a potent and versatile system to improve the targeting of cell populations for fundamental as well as therapeutic applications.

Lentiviral vectors as tools to understand central nervous system biology in mammalian model organisms

Lentiviruses have been extensively used as gene delivery vectors since the mid-1990s. Usually derived from the human immunodeficiency virus genome, they mediate efficient gene transfer to non-dividing cells, including neurons and glia in the adult mammalian brain. In addition, integration of the recombinant lentiviral construct into the host genome provides permanent expression, including the progeny of dividing neural precursors. In this review, we describe targeted vectors with modified envelope glycoproteins and expression of transgenes under the regulation of cell-selective and inducible promoters. This technology has broad utility to address fundamental questions in neuroscience and we outline how this has been used in rodents and primates. Combining viral tract tracing with immunohistochemistry and confocal or electron microscopy, lentiviral vectors provide a tool to selectively label and trace specific neuronal populations at gross or ultrastructural levels. Additionally, new generation optogenetic technologies can be readily utilized to analyze neuronal circuit and gene functions in the mature mammalian brain. Examples of these applications, limitations of current systems and prospects for future developments to enhance neuroscience knowledge will be reviewed. Finally, we will discuss how these vectors may be translated from gene therapy trials into the clinical setting.

Lassa-vesicular stomatitis chimeric virus safely destroys brain tumors

High-grade tumors in the brain are among the deadliest of cancers. Here, we took a promising oncolytic virus, vesicular stomatitis virus (VSV), and tested the hypothesis that the neurotoxicity associated with the virus could be eliminated without blocking its oncolytic potential in the brain by replacing the neurotropic VSV glycoprotein with the glycoprotein from one of five different viruses, including Ebola virus, Marburg virus, lymphocytic choriomeningitis virus (LCMV), rabies virus, and Lassa virus. Based on in vitro infections of normal and tumor cells, we selected two viruses to test in vivo. Wild-type VSV was lethal when injected directly into the brain. In contrast, a novel chimeric virus (VSV-LASV-GPC) containing genes from both the Lassa virus glycoprotein precursor (GPC) and VSV showed no adverse actions within or outside the brain and targeted and completely destroyed brain cancer, including high-grade glioblastoma and melanoma, even in metastatic cancer models. When mice had two brain tumors, intratumoral VSV-LASV-GPC injection in one tumor (glioma or melanoma) led to complete tumor destruction; importantly, the virus moved contralaterally within the brain to selectively infect the second noninjected tumor. A chimeric virus combining VSV genes with the gene coding for the Ebola virus glycoprotein was safe in the brain and also selectively targeted brain tumors but was substantially less effective in destroying brain tumors and prolonging survival of tumor-bearing mice. A tropism for multiple cancer types combined with an exquisite tumor specificity opens a new door to widespread application of VSV-LASV-GPC as a safe and efficacious oncolytic chimeric virus within the brain.

IMPORTANCE

Many viruses have been tested for their ability to target and kill cancer cells. Vesicular stomatitis virus (VSV) has shown substantial promise, but a key problem is that if it enters the brain, it can generate adverse neurologic consequences, including death. We tested a series of chimeric viruses containing genes coding for VSV, together with a gene coding for the glycoprotein from other viruses, including Ebola virus, Lassa virus, LCMV, rabies virus, and Marburg virus, which was substituted for the VSV glycoprotein gene. Ebola and Lassa chimeric viruses were safe in the brain and targeted brain tumors. Lassa-VSV was particularly effective, showed no adverse side effects even when injected directly into the brain, and targeted and destroyed two different types of deadly brain cancer, including glioblastoma and melanoma.

Ex vivo gene therapy using patient iPSC-derived NSCs reverses pathology in the brain of a homologous mouse model

Neural stem cell (NSC) transplantation is a promising strategy for delivering therapeutic proteins in the brain. We evaluated a complete process of ex vivo gene therapy using human induced pluripotent stem cell (iPSC)-derived NSC transplants in a well-characterized mouse model of a human lysosomal storage disease, Sly disease. Human Sly disease fibroblasts were reprogrammed into iPSCs, differentiated into a stable and expandable population of NSCs, genetically corrected with a transposon vector, and assessed for engraftment in NOD/SCID mice. Following neonatal intraventricular transplantation, the NSCs engraft along the rostrocaudal axis of the CNS primarily within white matter tracts and survive for at least 4 months. Genetically corrected iPSC-NSCs transplanted post-symptomatically into the striatum of adult Sly disease mice reversed neuropathology in a zone surrounding the grafts, while control mock-corrected grafts did not. The results demonstrate the potential for ex vivo gene therapy in the brain using human NSCs from autologous, non-neural tissues.

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Sly disease patient fibroblasts converted to iPSCs yield transplantable NSCs

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A PiggyBac transposon-based approach corrects the lysosomal enzyme deficiency

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Widespread migration of transplanted NSCs occurs in neonates, but not in adults

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Reversal of microglial pathology in a zone surrounding corrected grafts

The production of viral vectors designed to express large and difficult to express transgenes within neurons

BACKGROUND

Viral vectors are frequently used to deliver and direct expression of transgenes in a spatially and temporally restricted manner within the nervous system of numerous model organisms. Despite the common use of viral vectors to direct ectopic expression of transgenes within the nervous system, creating high titer viral vectors that are capable of expressing very large transgenes or difficult to express transgenes imposes unique challenges. Here we describe the development of adeno-associated viruses (AAV) and lentiviruses designed to express the large and difficult to express GluN2A or GluN2B subunits of the N-methyl-D-aspartate receptor (NMDA) receptor, specifically within neurons.

RESULTS

We created a number of custom designed AAV and lentiviral vectors that were optimized for large transgenes, by minimizing DNA sequences that were not essential, utilizing short promoter sequences of 8 widely used promoters (RSV, EFS, TRE3G, 0.4αCaMKII, 1.3αCaMKII, 0.5Synapsin, 1.1Synapsin and CMV) and utilizing a very short (~75 bps) 3' untranslated sequence. Not surprisingly these promoters differed in their ability to express the GluN2 subunits, however surprisingly we found that the neuron specific synapsin and αCaMKII, promoters were incapable of conferring detectable expression of full length GluN2 subunits and detectable expression could only be achieved from these promoters if the transgene included an intron or if the GluN2 subunit transgenes were truncated to only include the coding regions of the GluN2 transmembrane domains.

CONCLUSIONS

We determined that viral packaging limit, transgene promoter and the presence of an intron within the transgene were all important factors that contributed to being able to successfully develop viral vectors designed to deliver and express GluN2 transgenes in a neuron specific manner. Because these vectors have been optimized to accommodate large open reading frames and in some cases contain an intron to facilitate expression of difficult to express transgenes, these viral vectors likely could be useful for delivering and expressing many large or difficult to express transgenes in a neuron specific manner.

Gene therapy for hemophilia

Hemophilia is an X-linked inherited bleeding disorder consisting of two classifications, hemophilia A and hemophilia B, depending on the underlying mutation. Although the disease is currently treatable with intravenous delivery of replacement recombinant clotting factor, this approach represents a significant cost both monetarily and in terms of quality of life. Gene therapy is an attractive alternative approach to the treatment of hemophilia that would ideally provide life-long correction of clotting activity with a single injection. In this review, we will discuss the multitude of approaches that have been explored for the treatment of both hemophilia A and B, including both in vivo and ex vivo approaches with viral and nonviral delivery vectors.

Developments in Viral Vector-Based Vaccines

Viral vectors are promising tools for gene therapy and vaccines. Viral vector-based vaccines can enhance immunogenicity without an adjuvant and induce a robust cytotoxic T lymphocyte (CTL) response to eliminate virus-infected cells. During the last several decades, many types of viruses have been developed as vaccine vectors. Each has unique features and parental virus-related risks. In addition, genetically altered vectors have been developed to improve efficacy and safety, reduce administration dose, and enable large-scale manufacturing. To date, both successful and unsuccessful results have been reported in clinical trials. These trials provide important information on factors such as toxicity, administration dose tolerated, and optimized vaccination strategy. This review highlights major viral vectors that are the best candidates for clinical use.

Lentivirus vector-mediated Rho guanine nucleotide dissociation inhibitor 2 induces beta-2 adrenergic receptor desensitization in β2AR desensitization mice model

BACKGROUND

It is well-known that chronic administration of β2AR agonists can induce β2AR desensitization. Our previous study showed that Rho guanine nucleotide dissociation inhibitor 2 (RhoGDI2) overexpression induced beta-2 adrenergic receptor (β2AR) desensitization in airway smooth muscle cells. The purpose of this study was to further study the function of RhoGDI2 in β2AR desensitization by β2AR desensitization mouse model.

METHODS

Studies were performed using a β2AR desensitization mice model induced by salbutamol. The mice were randomly divided into five groups (n=45): RhoGDI2 overexpression group (n=10); RhoGDI2 siRNA group (n=10); empty viral vector group (n=10); experimental control group (n=10); blank control group-without any drug treatment (n=5). The first four groups were used the same methods and the same dose to establish β2AR desensitization mice model by salbutamol. The first three groups that salbutamol-treated were used for intratracheal delivery of lentiviral vectors. Airway hyperreactivity was measured through a whole-body plethysmograph system. RhoGDI2, β2AR, GRK2 mRNA and protein expression levels were then detected by RT-PCR and western blot analyses in fresh lung tissues. As well as the activity of GRK was assessed by light-dependent phosphorylation of rhodopsin.

RESULTS

We successfully constructed β2AR desensitization mouse model. As expected, airway responsiveness after inhaling acetylcholine chloride (Ach) was markedly increased in the RhoGDI2 overexpression group compared to experimental control group and blank control group when concentrations of Ach was 45 mg/mL (all P<0.05), while, it was markedly decreased in the RhoGDI2 siRNA group compared to experimental control group (P<0.05). RhoGDI2, GRK2 expressions and GRK enzymatic activity were significantly increased in RhoGDI2 overexpression group compared to experimental control group and blank control group (all P<0.05). RhoGDI2, GRK2 expressions and GRK enzymatic activity were significantly decreased in RhoGDI2 siRNA group compared to experimental control group and blank control group (all P<0.05). Conversely, β2AR expression were significantly lower in RhoGDI2 overexpression group compared to experimental control group and blank control group (all P<0.05), exhibiting an inverse correlation with RhoGDI2 expression.

CONCLUSIONS

To sum up, our present studies found that RhoGDI2 might induce β2AR desensitization and GRK2 might take part in RhoGDI2-mediated β2AR desensitization.

Filovirus-like particles as vaccines and discovery tools

Ebola and Marburg viruses are members of the family Filoviridae, which cause severe hemorrhagic fevers in humans. Filovirus outbreaks have been sporadic, with mortality rates currently ranging from 30 to 90%. Unfortunately, there is no efficacious human therapy or vaccine available to treat disease caused by either Ebola or Marburg virus infection. Expression of the filovirus matrix protein, VP40, is sufficient to drive spontaneous production and release of virus-like particles (VLPs) that resemble the distinctively filamentous infectious virions. The addition of other filovirus proteins, including virion proteins (VP)24, 30 and 35 and glycoprotein, increases the efficiency of VLP production and results in particles containing multiple filovirus antigens. Vaccination with Ebola or Marburg VLPs containing glycoprotein and VP40 completely protects rodents from lethal challenge with the homologous virus. These candidate vaccines are currently being tested for immunogenicity and efficacy in nonhuman primates. Furthermore, the Ebola and Marburg VLPs are being used as a surrogate model to further understand the filovirus life cycle, with the goal of developing rationally designed vaccines and therapeutics. Thus, in addition to their use as a vaccine, VLPs are currently being used as tools to learn lessons about filovirus pathogenesis, immunology, replication and assembly requirements.

Methods for gene transfer to the central nervous system

Gene transfer is an increasingly utilized approach for research and clinical applications involving the central nervous system (CNS). Vectors for gene transfer can be as simple as an unmodified plasmid, but more commonly involve complex modifications to viruses to make them suitable gene delivery vehicles. This chapter will explain how tools for CNS gene transfer have been derived from naturally occurring viruses. The current capabilities of plasmid, retroviral, adeno-associated virus, adenovirus, and herpes simplex virus vectors for CNS gene delivery will be described. These include both focal and global CNS gene transfer strategies, with short- or long-term gene expression. As is described in this chapter, an important aspect of any vector is the cis-acting regulatory elements incorporated into the vector genome that control when, where, and how the transgene is expressed.

Lentiviral vector-mediated RNA silencing in the central nervous system

RNA silencing is an established method for investigating gene function and has attracted particular interest because of the potential for generating RNA-based therapeutics. Using lentiviral vectors as an efficient delivery system that offers stable, long-term expression in postmitotic cells further enhances the applicability of an RNA-based gene therapy for the CNS. In this review we provide an overview of both lentiviral vectors and RNA silencing along with design considerations for generating lentiviral vectors capable of RNA silencing. We go on to describe the current preclinical data regarding lentiviral vector-mediated RNA silencing for CNS disorders and discuss the concerns of side effects associated with lentiviral vectors and small interfering RNAs and how these might be mitigated.

Alanine scanning mutagenesis of hepatitis C virus E2 cysteine residues: Insights into E2 biogenesis and antigenicity

Envelope glycoprotein 2 (E2) of hepatitis C virus contains 18 conserved cysteine (Cys) residues in its ectodomain. By cysteine-alanine mutagenesis and function analysis, six Cys in H77 E2 (C494, C508, C552, C564, C607 and C644) were found to be indispensable for recognition by conformation-dependent mAb H53. Removal of any of these Cys residues did not affect E2 heterodimerization with E1, but notably reduced E1E2 transmembrane transportation. These Cys together with C429 and C503 were required for conformation-dependent mAb H48 recognition. All of the above Cys except C607 were required for H77 and Con1 E2 binding to CD81. None of individual mutation of above Cys affected the ability of E2 to induce neutralizing antibodies in mice. Mouse antibodies mainly recognize E2 linear epitopes and are unrelated to epitopes recognized by human E2 antibodies. The findings provide new insights for understanding the biogenesis of functional HCV envelope proteins and HCV neutralizing immunity.

Improved lentiviral transduction of ALS motoneurons in vivo via dual targeting

Treatment of amyotrophic lateral sclerosis (ALS), a progressive neurodegenerative disease, is hampered by its complex etiology and lack of efficient means for targeted transfer of therapeutics into motoneurons. The objective of this research was engineering of a versatile motoneuron targeting adapter--a full-length atoxic tetanus toxin fused to core-streptavidin (CS-TeTIM)--for retro-axonal transduction of viral vectors; validation of the targeting efficiency of CS-TeTIM in vivo, by expression of green fluorescence protein (GFP) reporter in motoneurons of presymptomatic and symptomatic ALS-like SOD1(G93A) mice, and comparison with age-matched controls; and appraisal of lentiviral transduction with CS-TeTIM relative to (1) a HC binding fragment of tetanus toxin CS-TeTx(HC), (2) rabies glycoprotein (RG), and (3) a CS-TeTIM-RG dual targeting approach. CS-TeTIM and CS-TeTx(HC) were engineered using recombinant technology and site-directed mutagenesis. Biotinylated vectors, pseudotyped with vesicular stomatitis virus glycoprotein (VSV-G) or RG, were linked to these adaptors and injected intraperitoneally (ip) into presymptomatic (12 weeks old), symptomatic SOD1(G93A) (22 weeks old) or wild type control mice, followed by monitoring of GFP expression in the spinal cord and supraspinal motor structures with quantitative PCR and immuno-histochemistry. Transcripts were detected in the spinal cord and supraspinal motor structures of all mice 2 weeks after receiving a single ip injection, although in symptomatic SOD1(G93A) animals reporter RNA levels were lower compared to presymptomatic and wild-type controls irrespective of the targeting approach. GFP transduction with CS-TeTIM proved more efficient than CS-TeTx(HC) across all groups while CS-TeTIM-RG dual-targeted vectors yielded the highest transcript numbers. Importantly, in both wild-type and presymptomatic SOD1(G93A) mice strong colabeling of choline-acetyltransferase (ChAT) and GFP was visualized in neurons of the brain stem and spinal cord. CS-TeTIM, a versatile adaptor protein for targeted lentiviral transduction of motoneurons, has been engineered and its competence assessed relative to CS-TeTx(HC) and RG. Evidence has been provided that highlights the potential usefulness of this novel recombinant tool for basic research with implications for improved transfer of therapeutic candidates into motoneurons for the amelioration of ALS and related diseases.

Preferential lentiviral targeting of astrocytes in the central nervous system

The ability to visualize and genetically manipulate specific cell populations of the central nervous system (CNS) is fundamental to a better understanding of brain functions at the cellular and molecular levels. Tools to selectively target cells of the CNS include molecular genetics, imaging, and use of transgenic animals. However, these approaches are technically challenging, time consuming, and difficult to control. Viral-mediated targeting of cells in the CNS can be highly beneficial for studying and treating neurodegenerative diseases. Yet, despite specific marking of numerous cell types in the CNS, in vivo selective targeting of astrocytes has not been optimized. In this study, preferential targeting of astrocytes in the CNS was demonstrated using engineered lentiviruses that were pseudotyped with a modified Sindbis envelope and displayed anti-GLAST IgG on their surfaces as an attachment moiety. Viral tropism for astrocytes was initially verified in vitro in primary mixed glia cultures. When injected into the brains of mice, lentiviruses that displayed GLAST IgG on their surface, exhibited preferential astrocyte targeting, compared to pseudotyped lentiviruses that did not incorporate any IgG or that expressed a control isotype IgG. Overall, this approach is highly flexible and can be exploited to selectively target astrocytes or other cell types of the CNS. As such, it can open a window to visualize and genetically manipulate astrocytes or other cells of the CNS as means of research and treatment.

Efficient gene delivery and selective transduction of astrocytes in the mammalian brain using viral vectors

Astrocytes are now considered as key players in brain information processing because of their newly discovered roles in synapse formation and plasticity, energy metabolism and blood flow regulation. However, our understanding of astrocyte function is still fragmented compared to other brain cell types. A better appreciation of the biology of astrocytes requires the development of tools to generate animal models in which astrocyte-specific proteins and pathways can be manipulated. In addition, it is becoming increasingly evident that astrocytes are also important players in many neurological disorders. Targeted modulation of protein expression in astrocytes would be critical for the development of new therapeutic strategies. Gene transfer is valuable to target a subpopulation of cells and explore their function in experimental models. In particular, viral-mediated gene transfer provides a rapid, highly flexible and cost-effective, in vivo paradigm to study the impact of genes of interest during central nervous system development or in adult animals. We will review the different strategies that led to the recent development of efficient viral vectors that can be successfully used to selectively transduce astrocytes in the mammalian brain.

Gene delivery to pancreatic exocrine cells in vivo and in vitro

BACKGROUND

Effective gene transfer to the pancreas or to pancreatic cells has remained elusive although it is essential for studies of genetic lineage tracing and modulation of gene expression. Different transduction methods and viral vectors were tested in vitro and in vivo, in rat and mouse pancreas.

RESULTS

For in vitro transfection/transduction of rat exocrine cells lipofection reagents, adenoviral vectors, and Mokola- and VSV-G pseudotyped lentiviral vectors were used. For in vivo transduction of mouse and rat pancreas adenoviral vectors and VSV-G lentiviral vectors were injected into the parenchymal tissue. Both lipofection of rat exocrine cell cultures and transduction with Mokola pseudotyped lentiviral vectors were inefficient and resulted in less than 4% EGFP expressing cells. Adenoviral transduction was highly efficient but its usefulness for gene delivery to rat exocrine cells in vitro was hampered by a drastic increase in cell death. In vitro transduction of rat exocrine cells was most optimal with VSV-G pseudotyped lentiviral vectors, with stable transgene expression, no significant effect on cell survival and about 40% transduced cells. In vivo, pancreatic cells could not be transduced by intra-parenchymal administration of lentiviral vectors in mouse and rat pancreas. However, a high efficiency could be obtained by adenoviral vectors, resulting in transient transduction of mainly exocrine acinar cells. Injection in immune-deficient animals diminished leukocyte infiltration and prolonged transgene expression.

CONCLUSIONS

In summary, our study remarkably demonstrates that transduction of pancreatic exocrine cells requires lentiviral vectors in vitro but adenoviral vectors in vivo.

Restricted transgene expression in the brain with cell-type specific neuronal promoters

Tissue-targeted expression is of major interest for studying the contribution of cellular subpopulations to neurodegenerative diseases. However, in vivo methods to investigate this issue are limited. Here, we report an analysis of the cell specificity of expression of fluorescent reporter genes driven by six neuronal promoters, with the ubiquitous phosphoglycerate kinase 1 (PGK) promoter used as a reference. Quantitative analysis of AcGFPnuc expression in the striatum and hippocampus of rodents showed that all lentiviral vectors (LV) exhibited a neuronal tropism; however, there was substantial diversity of transcriptional activity and cell-type specificity of expression. The promoters with the highest activity were those of the 67 kDa glutamic acid decarboxylase (GAD67), homeobox Dlx5/6, glutamate receptor 1 (GluR1), and preprotachykinin 1 (Tac1) genes. Neuron-specific enolase (NSE) and dopaminergic receptor 1 (Drd1a) promoters showed weak activity, but the integration of an amplification system into the LV overcame this limitation. In the striatum, the expression profiles of Tac1 and Drd1a were not limited to the striatonigral pathway, whereas in the hippocampus, Drd1a and Dlx5/6 showed the expected restricted pattern of expression. Regulation of the Dlx5/6 promoter was observed in a disease condition, whereas Tac1 activity was unaffected. These vectors provide safe tools that are more selective than others available, for the administration of therapeutic molecules in the central nervous system (CNS). Nevertheless, additional characterization of regulatory elements in neuronal promoters is still required.

The endogenous protease inhibitor TIMP-1 mediates protection and recovery from cutaneous photodamage

UVB exposure is well known to induce skin photodamage and photoaging that correlates with qualitative and quantitative deterioration of the dermal extracellular matrix (ECM) because of the upregulation of matrix metalloproteinases (MMPs). Although inhibitory effects of tissue inhibitor of metalloproteinases (TIMPs) on most MMPs have been reported, the protective role of TIMP-1 against photodamage is poorly understood. To address this, TIMP-1 function was augmented or abolished in a human skin xenograft photodamage model after the confirmation of significantly diminished TIMP-1 expression both in photoaged and intrinsically aged skins. During a chronic UVB exposure regimen, pre-treatment with a lentiviral vector overexpressing TIMP-1 or concomitant administration of an anti-TIMP-1-neutralizing antibody (NAB) led to photoprotection or more severe photodamage, respectively. Overexpression of TIMP-1 resulted in significant inhibition of UVB-induced ECM degradation, as well as suppression of decreased skin elasticity and roughness, whereas the NAB-mediated inhibition of TIMP-1 had opposite effects. Furthermore, UVB-induced production of the pro-inflammatory cytokine, tumor necrosis factor α, was inhibited by TIMP-1 treatment of human keratinocytes. Taken together, these data shed light on the important role of TIMP-1 in protection and recovery from cutaneous photodamage because of its suppression of ECM degradation and inflammation.

Lentiviral vectors: basic to translational

More than two decades have passed since genetically modified HIV was used for gene delivery. Through continuous improvements these early marker gene-carrying HIVs have evolved into safer and more effective lentiviral vectors. Lentiviral vectors offer several attractive properties as gene-delivery vehicles, including: (i) sustained gene delivery through stable vector integration into host genome; (ii) the capability of infecting both dividing and non-dividing cells; (iii) broad tissue tropisms, including important gene- and cell-therapy-target cell types; (iv) no expression of viral proteins after vector transduction; (v) the ability to deliver complex genetic elements, such as polycistronic or intron-containing sequences; (vi) potentially safer integration site profile; and (vii) a relatively easy system for vector manipulation and production. Accordingly, lentivector technologies now have widespread use in basic biology and translational studies for stable transgene overexpression, persistent gene silencing, immunization, in vivo imaging, generating transgenic animals, induction of pluripotent cells, stem cell modification and lineage tracking, or site-directed gene editing. Moreover, in the present high-throughput '-omics' era, the commercial availability of premade lentiviral vectors, which are engineered to express or silence genome-wide genes, accelerates the rapid expansion of this vector technology. In the present review, we assess the advances in lentiviral vector technology, including basic lentivirology, vector designs for improved efficiency and biosafety, protocols for vector production and infection, targeted gene delivery, advanced lentiviral applications and issues associated with the vector system.

Lentiviral vectors carrying enhancer elements of Hb9 promoter drive selective transgene expression in mouse spinal cord motor neurons

Recombinant lentiviral vectors (rLVs) have emerged as versatile tools for gene delivery applications due to a number of favorable features, such as the possibility to maintain long-term transgene expression, the flexibility in the design of the expression cassettes and recent improvements in their biosafety profile. Since rLVs are able to infect multiple cell types including post-mitotic cells such as neurons and skeletal muscle cells, several studies have been exploring their application for the study and cure of neurodegenerative diseases. In particular, the introduction of rLVs carrying cell-type specific promoters could restrict the transgene expression either to neuronal or glial cells, thus helping to better dissect in vivo the role played by these cell populations in several neurodegenerative processes. In this study we developed rLVs carrying motor neuron specific regulatory sequences derived from the promoter of homeobox gene Hb9, and demonstrated that these constructs can represent a suitable platform for selective gene-targeting of murine spinal cord motor neurons, in vivo. This tool could be instrumental in the dissection of the molecular mechanisms involved in the selective degeneration of motor neurons occurring in Motor Neuron Diseases.