Gene therapy for the treatment of sensory neuropathy

Viruses and Virus-Like Particles in Biotechnology: Fundamentals and Applications

Although viruses are simple biological systems, they are capable of evolving highly efficient techniques for infecting cells, expressing their genomes, and generating new copies of themselves. It is possible to genetically manipulate most of the different classes of known viruses in order to produce recombinant viruses that express foreign proteins. Recombinant viruses have been used in gene therapy to deliver selected genes into higher organisms, in vaccinology and immunotherapy, and as important research tools to study the structure and function of these proteins.

Virus-like particles (VLPs) are multiprotein structures that mimic the organization and conformation of authentic native viruses but lack the viral genome. They have been applied not only as prophylactic and therapeutic vaccines but also as vehicles in drug and gene delivery and, more recently, as tools in nanobiotechnology.

In this chapter, basic and advanced features of viruses and VLPs are presented and their major applications are discussed. The different production platforms based on animal cell technology are explained, and their main challenges and future perspectives are explored. The implications of large-scale production of viruses and VLPs are discussed in the context of process control, monitoring, and optimization. The main upstream and downstream technical challenges are identified and discussed accordingly.

Viruses and Virus-Like Particles in Biotechnology

Although viruses are simple biological systems, they are capable of evolving highly efficient techniques for infecting cells, expressing their genomes, and generating new copies of themselves. It is possible to genetically manipulate most of the different classes of known viruses in order to produce recombinant viruses that express foreign proteins. Recombinant viruses have been used in gene therapy to deliver selected genes into higher organisms, in vaccinology and immunotherapy, and as important research tools to study the structure and function of these proteins.

Virus-like particles (VLPs) are multiprotein structures that mimic the organization and conformation of authentic native viruses but lack the viral genome. They have been applied not only as prophylactic and therapeutic vaccines but also as vehicles in drug and gene delivery and, more recently, as tools in nanobiotechnology.

In this article, basic and advanced features of viruses and VLPs are presented and their major applications are discussed. The different production platforms based on animal cell technology are explained, and their main challenges and future perspectives are explored. The implications of large-scale production of viruses and VLPs are discussed in the context of process control, monitorization, and optimization. The main upstream and downstream technical challenges are identified and discussed accordingly.

Invited review: festschrift edition of neurosurgery peripheral nervous system as a conduit for delivering therapies for diabetic neuropathy, amyotrophic lateral sclerosis, and nerve regeneration

In this review, we describe how therapies that promote axonal regeneration and neuronal protection can complement surgery for a successful functional restoration in peripheral nerve disorders. We discuss the advantages of peripheral drug delivery and the role of the neurosurgeon in the precise delivery of molecular therapies to surgically inaccessible structures. Strategies for enhancing uptake and retrograde transport of therapeutics, including gene therapy, are emphasized as conduits for delivery of therapeutics. Finally, candidate therapeutic proteins and genes are discussed in the context of application to degenerative disorders of the nervous system, including nerve injury, peripheral neuropathy, and amyotrophic lateral sclerosis.

Gene therapy and informed consent decision making: nursing research directions

Recent gene therapy clinical trials have demonstrated significant promise for treating a number of genetic neuromuscular disorders. Although nurses are experienced in educating patients and families about the benefits and risks of conventional therapeutics, there are significant challenges for guiding patients through the decision-making phase of gene therapy clinical trial participation. The first part of this review provides an overview and update on neuromuscular gene therapy, including viral delivery principles and historical progress. The second part discusses risk/benefit perception of gene therapy and factors affecting the decision making for patients interested in participating in a trial. Future challenges for gene therapy are targeted high-efficiency delivery, and additional research on developing patient-centered decision support interventions.

In vitro and in vivo gene therapy with CMV vector-mediated presumed dog beta-nerve growth factor in pyridoxine-induced neuropathy dogs

Due to the therapeutic potential of gene therapy for neuronal injury, many studies of neurotrophic factors, vectors, and animal models have been performed. The presumed dog β-nerve growth factor (pdβ-NGF) was generated and cloned and its expression was confirmed in CHO cells. The recombinant pdβ-NGF protein reacted with a human β-NGF antibody and showed bioactivity in PC12 cells. The pdβ-NGF was shown to have similar bioactivity to the dog β-NGF. The recombinant pdβ-NGF plasmid was administrated into the intrathecal space in the gene therapy group. Twenty-four hours after the vector inoculation, the gene therapy group and the positive control group were intoxicated with excess pyridoxine for seven days. Each morning throughout the test period, the dogs' body weight was taken and postural reaction assessments were made. Electrophysiological recordings were performed twice, once before the experiment and once after the test period. After the experimental period, histological analysis was performed. Dogs in the gene therapy group had no weight change and were normal in postural reaction assessments. Electrophysiological recordings were also normal for the gene therapy group. Histological analysis showed that neither the axons nor the myelin of the dorsal funiculus of L₄ were severely damaged in the gene therapy group. In addition, the dorsal root ganglia of L₄ and the peripheral nerves (sciatic nerve) did not experience severe degenerative changes in the gene therapy group. This study is the first to show the protective effect of NGF gene therapy in a dog model.

Isolation of specific peptides that home to dorsal root ganglion neurons in mice

We isolated peptides that home to mouse dorsal root ganglion (DRG) from a phage library expressing random 7-mer peptides fused to a minor coat protein (pIII) of the M13 phage. An in vitro biopanning procedure yielded 113 phage plaques after five cycles of enrichment by incubation with isolated DRG neurons and two cycles of subtraction by exposure to irrelevant cell lines. Analyses of the sequences of this collection identified three peptide clones that occurred repeatedly during the biopanning procedure. Phage-antibody staining revealed that the three peptides bound to DRG neurons of different sizes. To determine if the peptides would recognize neuronal cells in vivo, we injected individual GST-peptide-fusion proteins into the subarachnoid space of mice and observed the appearance of immunoreactive GST in the cytosol of DRG neurons with a similar size distribution as that observed in vitro, indicating that the GST-peptide-fusion proteins were recognized and taken up by different DRG neurons in vivo. The identification of homing peptide sequences provides a powerful tool for future studies on DRG neuronal function in vitro and in vivo, and opens up the possibility of neuron-specific drug and gene delivery in the treatment of diseases affecting DRG neurons.

Diabetic neuropathy: new strategies for treatment

Current therapeutic possibilities can be divided into two groups: the pathogenetically oriented and the symptomatic therapy. One of the most important component of etiology-based treatment is the stabilization of glycemic control. Based on efficacy and safety data benfotiamine and alpha-lipoic acid should be considered as first choices among pathogenetically oriented treatments of diabetic neuropathy. Promising data were published about the aldose reductase inhibitor ranirestat. The symptomatic effect of antiepileptic drugs in diabetic painful neuropathy (DPN) is originated from several possible pharmacological properties. Pregabalin and gabapentin have the highest efficacy and the lowest frequency of adverse events among these drugs. Antidepressants also extensively used for symptomatic treatment in DPN. In the last years several studies were published about the benefial effect of duloxetine. Most likely combination therapy will be frequently applied in the future for the treatment of DPN, the optimal choice could be to combine pathogenetically oriented and symptomatic treatment.

Gene therapy: the first two decades and the current state-of-the-art

The concept of gene therapy was envisioned soon after the emergence of restriction endonucleases and subcloning of mammalian genes in phage and plasmids. Over the ensuing decades, vectors were developed, including nonviral methods, integrating virus vectors (gammaretrovirus and lentivirus), and non-integrating virus vectors (adenovirus, adeno-associated virus, and herpes simplex virus vectors). Preclinical data demonstrated potential efficacy in a broad range of animal models of human diseases, but clinical efficacy in humans remained elusive in most cases, even after decades of experience in over 1000 trials. Adverse effects from gene therapy have been observed in some cases, often because of viral vectors retaining some of the pathogenic potential of the viruses upon which they are based. Later generation vectors have been developed in which the safety and/or the efficiency of gene transfer has been improved. Most recently this work has involved alterations of vector envelope or capsid proteins either by insertion of ligands to target specific receptors or by directed evolution. The disease targets for gene therapy are multiple, but the most promising data have come from monogenic disorders. As the number of potential targets for gene therapy continues to increase, and a substantial number of trials continue with both the standard and the later generation vector systems, it is hoped that a therapeutic niche for gene therapy will emerge in the coming decades.

The therapeutic potential of gene transfer for the treatment of peripheral neuropathies

Peripheral neuropathy is a common medical problem with numerous aetiologies. Unfortunately, for the majority of cases there is no available medical solution for the underlying cause, and the only option is to try to treat the resulting symptoms. Treatment options exist when neuropathy results in positive symptoms such as pain, but there is a significant lack of treatments for negative symptoms such as numbness and weakness. Systemic application of growth factor peptides has shown promise in protecting nerves from neuropathic insults in preclinical animal studies, but translation into human trials has been problematic and disappointing. Significant advancements have been made in the past few years in utilising gene therapy approaches to treat peripheral neuropathy by expressing neuroprotective gene products either systemically or in specific nervous tissues. For example, plasmids expressing vascular endothelial growth factor injected into muscle, or herpes-simplex-virus-based vectors expressing neurotrophin gene products delivered to dorsal root ganglion neurons, have been used to protect peripheral nerve function in animal models of diabetes-associated peripheral neuropathy. Many published studies support the feasibility of this approach, although several questions still need to be addressed as gene therapy to treat peripheral neuropathy moves out of the laboratory and into the clinic.