Gene therapy viral-based systems

Gene therapy is based on the concept that involves the treatment of defective gene in specific cell by either replacement or supplementing the genetic material in order to correct the defective one. Transfection efficacy covers many drawbacks in gene therapy. Viral or non-viral gene delivery systems are the two main types of vectors... 

Miller, A.D., The problem with cationic liposome/micelle-based non-viral vector systems for gene therapy, Current Medicinal Chemistry, 2003, 10, 1195-1211. 

DNA plasmid-based treatment ( gene therapy ) is considered an alternative to the one based on classical chemical drugs or proteins recovered from recombinant cells. Treatment of acquired and inherent genetic diseases as well as the use of DNA for the purpose of vaccination are potential applications of plasmid DNA (pDNA). The plasmid carries information that allows protein expression in the targeted human cells as well as eukaryotic regulatory elements and specific prokaryotic sequences that control replication in the host cell, see Fig. 10. Formulation is required for ex- or in-vivo administration. Selected systems for gene expression can be viral or non-viral. 

Successful gene therapy demands an effective system for therapeutic gene delivery into organs and tissues. Therefore gene delivery is based on the development of a non-viral delivery system. Such vector systems have the ability to introduce the alien genetic information into a cell. Carbon nanotubes can be used for creation of new vectors for gene transportation. 

There is a wide variety of vectors used to deliver DNA or oligonucleotides into mammalian cells, either in vitro or in vivo. The most common vector systems are based on viral [retroviruses (9, 10), adeno-associated virus (AAV) (11), adenovirus (12, 13), herpes simplex virus (HSV) (14)] andnonviral [cationic liposomes (15,16), polymers and receptor-mediated polylysine-DNA] complexes (17). Other viral vectors that are currently under development are based on lentiviruses (18), human cytomegalovirus (CMV) (19), Epstein-Barr virus (EBV) (20), poxviruses (21), negative-strand RNA viruses (influenza virus), alphaviruses and herpesvirus saimiri (22). Also a hybrid adenoviral/retroviral vector has successfully been used for in vivo gene transduction (23). A simplified schematic representation of basic human gene therapy methods is described in Figure 13.1. 

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