GENE THERAPY Agustina Setiawati, M.Sc., Apt
DEFINITION
1. Gene therapy is a technique for correcting “defective” genes responsible for disease development.
CYSTIC FIBRIOSIS Cystic fibrosis (CF) is one of the most fatal heredity It is caused by more than 500 different mutations in the
cystic fibrosis transmembrane conductance regulator (CFTR) gene
A thick mucus which is a results of: Alignate produced by bacteria DNA from lysed cells Leucocytes which accumulate due to the infection
“ When genes are altered so that the encoded proteins are unable to carry out their normal functions, genetic disorders can result”
Several approaches of Gene Therapy
A normal gene may be inserted into a nonspecific location
An abnormal gene could be swapped The abnormal gene could be repaired through
selective reverse mutation
What is reverse mutation?
+-WT, active
+
+
Mutate - to + Mutant, inactive
+-
WT, activeSame site revertant
+-
Mutate + to -
WT ? activedifferent site revertant
1. Gene therapy studies, a "normal" gene is inserted into the genome to replace an "abnormal," disease-causing gene.
2. A carrier molecule called a vector must be used to deliver the therapeutic gene to the patient's target cells.
3. The most common vector is a virus that has been genetically altered to carry normal human DNA
How Does Gene Therapy Work?
1. Enabling people to have children where natural conception is impossible (a more effective treatment of infertility).
2. The potential for discovering cures for terrible diseases - leading to less pain and suffering.
3. Sex selection to prevent genetic diseases.
4. Increased availability of organs for transplant.
5. Increased procreative autonomy (choice over some of the genetic characteristics that one's future child will possess).
Advantages of Gene Therapy
Disadvantages Gene Therapy
Safety concerns - the risk of detrimental genetic effects (bad biological consequences)
Dangers associated with 'genetic reductionism' - reducing human difficulties to genetic causes and ignoring their social context (EG, disability)
Other potential harms - e.g., the perpetuation of present inequalities/ stereotypes/ power relations, both within countries and between countries, could result,
SOMATIC GENE THERAPY“ Transfer material genetic to the body cells
except germline”
GERMLINE GENE THERAPY“ Involve genetic modification of germ cells”
Ex vivo manipulation techniques Electroporation Liposomes Gold bullets (fired within helium pressurized gun) Retrotransposons (jumping genes – early days)
In vivo techniques usually utilize viral vectors Virus = carrier of desired gene Virus is usually “crippled” to disable its ability to cause
disease Viral methods have proved to be the most efficient to
date Many viral vectors can stable integrate the desired
gene into the target cell’s genome
Problem: Replication defective viruses adversely affect the virus’ normal ability to spread genes in the body
Reliant on diffusion and spread Hampered by small intercellular spaces for transport Restricted by viral-binding ligands on cell surface therefore
cannot advance far.
VECTOR
An adequate carrying capacity To be undetectable by immune system Safe to patient High efficiency
RETROVIRUS
RNA virus, so it need reverse transcription and integration when enter to the cell
Only divide in rapid proliferation cell (hair, intestine )
Insert their material genetic in the middle of important gene
Response is reduced by immune response
group-specific antigen (gag) codes for core and structural proteins of the viruspolymerase (pol) codes for reverse transcriptase, protease and integraseenvelope (env) codes for the retroviral coat proteins.
ADENOVIRUS DNA virus Can infect slow proliferating cell, ie: blood,
lung, skin Material genetic can not be integrated to host
DNA Response is reduced by immune response
ADENO-ASSOCIATE VIRUS (AAV)
Occur naturally in human body DNA virus Harmless, non pathogenic, do not cause
immune response Insert their material genetic into chromosome
19 (spesific site) Only 2 genes can be inserted to these vector Trial to treat muscle and eye disease
Non VIRAL VECTOR
Artificial liposome Human artificial chromosomes—introducing 47th
chromosome to the cell Chemical linking therapeutic DNA that can bind
to specific receptor of cell Cationic Liposome Naked DNA (electroporation, gene gun, DNA
injection)
Cationik liposome forms complex with DNA (negative charge)
Net charge of the complexes is positive so it can be interact to cell membrane
Human Artificial Chromosome
47th chromosome Microchromosome, has only 6- 10 Mb size Developed after bacterial and yeast artificial
chromosome Grown in HT1080 cell