Novel molecular approaches to cystic fibrosis gene therapy

Abstract

Gene therapy holds promise for the treatment of a range of inherited diseases, such as cystic fibrosis. However, efficient delivery and expression of the therapeutic transgene at levels sufficient to result in phenotypic correction of cystic fibrosis pulmonary disease has proved elusive. There are many reasons for this lack of progress, both macroscopically in terms of airway defence mechanisms and at the molecular level with regard to effective cDNA delivery. This review of approaches to cystic fibrosis gene therapy covers these areas in detail and highlights recent progress in the field. For gene therapy to be effective in patients with cystic fibrosis, the cDNA encoding the cystic fibrosis transmembrane conductance regulator protein must be delivered effectively to the nucleus of the epithelial cells lining the bronchial tree within the lungs. Expression of the transgene must be maintained at adequate levels for the lifetime of the patient, either by repeat dosage of the vector or by targeting airway stem cells. Clinical trials of gene therapy for cystic fibrosis have demonstrated proof of principle, but gene expression has been limited to 30 days at best. Results suggest that viral vectors such as adenovirus and adeno-associated virus are unsuited to repeat dosing, as the immune response reduces the effectiveness of each subsequent dose. Nonviral approaches, such as cationic liposomes, appear more suited to repeat dosing, but have been less effective. Current work regarding non-viral gene delivery is now focused on understanding the mechanisms involved in cell entry, endosomal escape and nuclear import of the transgene. There is now increasing evidence to suggest that additional ligands that facilitate endosomal escape or contain a nuclear localization signal may enhance liposome-mediated gene delivery. Much progress in this area has been informed by advances in our understanding of the mechanisms by which viruses deliver their genomes to the nuclei of host cells.

RNA Interference with Special Reference to Combating Viruses of Crustacea

“…A helper virus (commonly adenovirus and HSV) provides AAV with the additional genes it requires for replication. The virus can infect a variety of dividing and non-dividing cell types and remains infectious after heating or freezedrying [42,79,98,192].…”

“…Polymer complexes offer an alternative to liposomes and are believed to protect DNA from degradation by condensing DNA molecules [98,183]. Polymer complexes can be naturally or synthetically derived.…”

“…However, the efficiency of transfection using liposomes is often less than that achieved using viral vectors. Hence, liposomes can be conjugated to defective viral particles, viral protein, or virally derived peptides that are able to disrupt the lysosome and/or increase DNA transport to the nucleus [47,75,98,156].…”

Augmentation of adenovirus 5 vector-mediated gene transduction under physiological pH conditions by a chitosan/NaHCO3 solution

“…Highdosage rAdv has been applied in gene therapies involving CARdeficient cells owing to the low efficiency of AMGT. 36,37 However, high dosage rAdv leads to liver toxicity and thus raises safety concerns. 38 Our study shows that chitosan/NaHCO 3 can greatly improve the efficiency of AMGT, which may allow us to lower the rAdv dosage in gene therapy.…”

In VivoEvaluation of Adeno-Associated Virus Gene Transfer in Airways of Mice with Acute or Chronic Respiratory Infection

“…As a disease caused by a single defective gene, CF airway disease is ideal for treatment with gene therapy (Lee et al, 2005). However, over 20 years have elapsed since the discovery of the CF transmembrane conductance regulator and the associated CFTR gene, and still, no viable gene therapy option exists for curing or alleviating airway disease (Birault et al, 2013).…”