Therapeutic Gene Transfer

Gene therapy is a long-established concept, described in 1970 as the use of recombinant DNA for the treatment or cure of inherited disease in man (1). In effect, the pathology of an inherited disorder can be alleviated by the expression of an introduced gene to compensate for the defective gene product. 

The potential use of gene therapy has since expanded as conditions such as cancer, atherosclerosis, transplant operations, and infectious disease are now viewed as suitable targets for intervention. For example, HTV and parasitic infection (2-5). Furthermore, the ability to transfer genes into cell in vitro is also an important tool in the research of gene expression. 

Genes can be introduced by the application of naked DNA alone however, better efficiency is achieved when the DNA is incorporated into a delivery vector. These delivery vectors consist of viral, those utilizing modified virus particles for DNA delivery, and nonviral, for which various chemicals are used to aid DNA packaging and delivery. Viral vectors confer significantly better transfection efficiency than nonviral vectors however, recently the toxicity and oncogenic side effects of viral vectors have become a major concern (6). Nonviral vectors do not have such serious side effects but lack the efficiency (7). 

One of the principal forms of nonviral delivery is liposome-mediated gene transfer, in which the DNA is enveloped in a cationic lipid that acts as a shield against the degradation or inactivation of the DNA during the process of gene transfer. 

Peptides have many desirable properties as components of synthetic vectors. Peptide synthetic chemistry is well established, with the convenience of automated synthesis resulting in a well-defined, high-purity product of low toxicity and immunogenicity for in vivo use. Furthermore, even short peptides of 7 to 30 amino acids can accommodate enormous structural diversity, functionality, and combinations of properties. 

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Guibinga G H, Lochmuller H, Massie B, et al. (1998). Combinatorial blockade of calcineurin and CD28 signaling facilitates primary and secondary therapeutic gene transfer by adenovirus vectors in dystrophic (mdx) mouse muscles. /. Virol. 72 4601-4609. 

Bartoli M, Poupiot J, Goyenvalle A, et al. (2006). Noninvasive monitoring of therapeutic gene transfer in animal models of muscular dystrophies. Gene Ther. 13 20-28. 

The main drawback of nonviral systems is that they normally only lead to the transient expression of the therapeutic gene as it is not permanently integrated into the host genome. In consequence, the therapeutic gene transfer must be regularly repeated, possibly over a long period of time, further disadvantages are insufficient cell- or tissue specificity and... 

A promising alternative to viral gene transfer is lipofection, the transfer of the negatively charged DNA material by cationic lipids (13-18). There is no restriction on the size of the therapeutic gene and no risk of immunogeni-city or infection (19). Thus, lipofection in vivo can be principally performed several times (20). Furthermore, cationic lipids can be synthesized in large quantities with relatively little effort. 

L Severe combined immunodeficiency (SCID) syndromes are excellent models for gene therapy because of the genetic basis of these disorders and significant advances in the technology to transfer therapeutic genes into hematopoietic precursor cells. For all these reasons, which of the following syndromes represents an ideal candidate for gene therapy ... 

The therapeutic efficacy of either systemic or local pulmonary delivery of the IFN-y gene was evaluated in a murine allergen-induced airway hyperresponsiveness (AHR) model (Dow et al. 1999) and it was found that a high efficiency of gene transfer could be achieved. Intratracheal administered cationic liposomes were prepared from a mixture of l,2-diacylglycero-3-ethylphosphocholine (EDMPC) and cholesterol. Intravenous injections were prepared from l,2-dioleyl-3-trimethylammo-ninm propane (DOTAP) and cholesterol and compared with pulmonary administered... 

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