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Possible Future Treatments

Possible Future Treatments

 

Gene therapy:

  • The genotype (therefore the phenotype of target cells) is altered:
  1. Normal alleles of the gene are inserted into the target cells using a genetically modified virus or using liposomes (spherical phospholipid bilayers)
  2. The normal form of the gene is transcribed and translated
  3. A functioning protein is produced in the target cells

 

Virsuses:

  • Virus; DNA sequence that allows it to replicate is removed and replaced with the normal allele of the desired gene (and a promoter sequence which initiates tanscription and translation)
  • When infected with some viruses; the viral DNA becomes incorporated into our cells’ own DNA
  • Others the viral DNA remains independent within the nucleus of our cells (this is used into the CFTR trials)
  • Potentially efficient form of gene transfer however it produces an inflammatory response (symptoms – headache, fatigue, fever, raised heart rate)

 

 

Liposomes:

  • A copy of the normal allele is inserted into a loop of DNA (plasmid)
  • The plasmid is then combined with liposomes (spherical phospholipid bilayers)
  • Positively charged head groups of the phospholipids combine with the DNA to form a liposome-DNA complex
  • CF patient breathes in an aerosol containing these complexes using a nebuliser; the liposomes fuse with epithelial cell membranes and carry the DNA into the cells

 

Progress:

  • CFTR protein allele has been successfully transferred to lung epithelial cells of CF patients
  • Presence of functionaing ion channels indicated by reduction in potential difference across the membranes in the nose and lungs and increased chloride secretions
  • Temporary fixture; longest trial lasted 15 days

 

  • First condition sucessfully treated using gene therapy was rare disorder severe combined immunodeficiency (SCID)
  • Could not make enzyme needed for immune system to wor
  • Ashanti DeSilva; white blood cells removed, alleles for functioning gene inserted into white blood cells using a virus
  • Cells replaced; now has regular transfusions

 

  • These treatments all work to alter specific somatic (body) cells and are permitted under UK legislation
  • Alternatively germ line therapy could be used, on egg and sperm cells, is not permitted (every cell in the body contains the new gene) ethical issues