ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
A modified VIRUS used to introduce genes into cells or tissues. Viral vectors are usually altered so that they are defective in their capacity to replicate, while still able to infect cells and induce the CELL to manufacture PROTEINS encoded by the viral genes (see GENE). Novel genes, inserted into the viral GENOME, are also expressed. Some viral vectors are constructed in viruses which do not need CELL DIVISION in order for their genetic material to be incorporated into the cell genome, such as adenovirus, or herpes simplex virus. Others require cell division in order to be expressed. Viral vectors are useful because a gene which is normally absent may be expressed in a localized manner, and the functional consequences of expression of the protein product, for example a RECEPTOR or a GROWTH FACTOR, may be observed. Viral vectors may prove useful in treating diseases, in a method called GENE THERAPY. For example, viral vectors may provide genes in disorders characterized by lack of a functional gene, such as cystic fibrosis. Such a virus would be required to be non-toxic to the target cell. Viral vectors may also be useful in treating some tumours (see TUMOUR), in which cells are rapidly and abnormally dividing to produce new tissue. In this case, viruses which require cell division to replicate may be useful, and may be targeted against the tumour, inferring toxicity only against those cells which are actively dividing.
In-Vivo Imaging of Transgene Expression Using the Herpesviral Thymidine Kinase Reporter Gene
Robert J. Gropler, David K. Glover, Albert J. Sinusas, Heinrich Taegtmeyer in Cardiovascular Molecular Imaging, 2007
Several key issues concerning cardiac gene therapy remain unresolved at present (Table 1). This starts with the basic methodologic question about which technique for gene transfer should be applied in which situation. Successful cardiac gene therapy requires a suitable technique for local delivery to the heart, and an appropriate vector for delivering and expressing gene(s) in the desired cell type (15). Viral vectors include retrovirus, adenovirus, adeno-associated virus, and lentivirus. Most frequently applied non-viral gene therapy methods include the use of liposomes and injection of vector-free DNA (naked DNA). Vector delivery techniques include direct epi- or endocardial intramyocardial injection, pericardial application, and arterial or retrovenous perfusion. Consensus on the best approach for a given situation has not yet been obtained.
Application of Bioresponsive Polymers in Gene Delivery
Deepa H. Patel in Bioresponsive Polymers, 2020
To achieve it, two major systems have been used for a while; viral and non-viral mediated systems. Viral mediated system is based on the uses of various viruses as carriers to insert genetic sequence into the host cell. The viruses have the ability to cross cell barriers and insert their genetic material inside the host cell. Some examples of viruses used include retroviral vectors as human immunodeficiency virus (HIV), adeno-associated virus (AAV), herpes simplex virus (HSV), Epstein Barr virus (EBV), adeno-viruses (AV), hepatitis B virus (HBV), Moloney murine leukemia virus (MoMLV). Creating a viral vector involves producing a recombinant virus lacking replication but maintaining its ability to infect cells [2]. These viral vectors are generally efficient tools of transfection but they possess some disadvantages like high production cost, difficulty in targeting to certain cells, size limitation of DNA constructs safety concerns, immunogenic reactions, toxic side effects, and possibility of triggering oncogenes, possibility to revert back or to retain an infectious form. The tentative to overcome such drawbacks has opened the gates to exploration of alternatives methods, which are non-viral mediated systems. In the recent past, non-viral mediated gene transfer has gained much more interest as potentially safe and effective methods to transfer genes in a wide range of genetic disease.
Versatility of cell-penetrating peptides for intracellular delivery of siRNA
Published in Drug Delivery, 2018
Tejinder Singh, Akula S. N. Murthy, Hye-Jin Yang, Jungkyun Im
Small interfering RNAs (siRNAs) lead to downregulation of target mRNAs and thus provide a promising pharmaceutical target in gene therapy (Vaissière et al., 2017; Xiang et al., 2017). However, due to their high molecular weight and the negative charge of the phosphate backbone, they cannot readily cross the cell membrane. Therefore, the clinical and therapeutic value of siRNAs is currently limited. Continuous research has been pursued to deliver siRNAs through the cell membrane into the cytoplasm, and various strategies have been developed to overcome this permeability issue (Nakase et al., 2013). Among them, viral and non-viral approaches have been the primary delivery strategies. Viral vectors are primitive vectors that have been utilized for gene therapy. These vectors have unique features that allow delivery of genetic material across the cell membrane with high efficacy. However, their success has been limited due to several challenges, for instance, limited cargo-carrying capacity, low delivery efficiency, the risk of mutation, high cytotoxicity, and lack of target specificity. In addition, viral vectors are not compatible with all kinds of nucleic acid-based molecules (e.g., short synthetic oligonucleotides) (Lehto et al., 2016). However, opportunities still exist to improve ways the process of viral vectorization (Lehto et al. 2012; Nakase et al. 2012).
Targeting central nervous system pathologies with nanomedicines
Published in Journal of Drug Targeting, 2019
Shoshy Mizrahy, Anna Gutkin, Paolo Decuzzi, Dan Peer
In order to overcome the obstacles mentioned above, many attempts to develop therapeutic agents have been made. This includes viral vectors, nanoparticles (NP), cell penetrating peptides (CPPs) and many more. Viral vectors have become a valuable tool for therapeutic gene delivery to a specific site. A number of different viruses have been studied as vectors for gene CNS delivery. These include lentivirus [45], retrovirus [46], recombinant adeno-associated virus [47] and herpes simplex virus [48]. Although the use of viral vectors demonstrated satisfactory efficiency for CNS delivery, there are several disadvantages that should be considered when approaching this delivery method. These limitations include unwanted immune response, changes in the properties of the delivered virus due to endogenous recombination and mutagenic behaviour leading to oncogenesis.
Innovative therapies for neovascular age-related macular degeneration
Published in Expert Opinion on Pharmacotherapy, 2019
Hasenin Al-Khersan, Rehan M. Hussain, Thomas A. Ciulla, Pravin U. Dugel
Recently, the eye has become a target for investigational gene therapy due to the monogenic nature of many inherited retinal diseases (IRDs), its accessibility, tight blood-ocular barrier, the ability to non-invasively monitor for functional and anatomic outcomes, as well as its relative immune-privileged state. Gene therapy for nAMD offers the promise of long-term continuous expression of anti-VEGF-A protein with a single administration. Viral vectors are conduits for transferring desired genetic information to host cells. Vectors currently used in ocular gene therapy clinical trials include adeno-associated virus (AAV), small single-stranded DNA viruses of the parvovirus family, and lentivirus, RNA viruses of the retrovirus family. After successful transduction, the target cells transcribe and translate the viral genetic material into therapeutic protein, which then modulates the pathogenesis of the targeted disease process.
Related Knowledge Centers
- Cell Culture
- Genome
- In Vitro
- In Vivo
- Molecular Biology
- Transduction
- Virus
- Gene Delivery
- Cell
- Gene