Genes Flashcards
How many defective genes are there per person?
400
What are examples of genetic disorders?
Haemophilia A and B
Cystic fibrosis
Muscular dystrophy
Sickle cell disease
What are the three mechanisms of gene therapy?
Replace disease causing gene
Inactivate disease causing gene
Introduce new gene to help treat disease
What is GTMP?
Gene therapy medicinal products
Contains recombinant nucleic acids
Administered to regulate replace add or delete a genetic sequence
What is genotoxicity?
If integrated into host genome can disrupt tumour suppressor genes and enhance proto onco genes leading to cancer
What is gene inhibition?
Add blocking gene so cell functions normal
What is cytotoxic gene therapy?
Add suicide gene to diseased cell gene makes toxic products cell dies
What is immune system engineering?
T cell can’t recognise tumour so T cell gets receptor specific for tumour, targets tumour and tumour cell dies
What is humeral immune response?
B. Cells produce antibodies
What is cell mediated immune response?
Driven by T cells macrophages and cytokines
What viral vectors will integrate into the host genome?
Retrovirus
Lentivirus
What viral vectors won’t integrate into the host genome?
HSV-1
Adeno associated virus (AAV)
Adenovirus
What family of viruses are AAV a part of?
Parvo virus family
What is the disadvantage of AAV as a vector?
Is complex and expensive
What is an example of a disease that AAV vectors are used in gene delivery?
Lipoprotein lipase deficiency
Inherited genetic condition – rare
Defective LDL gene = increased fat in blood
AAV delivers functioning LDL gene to muscle cells (IM)
Muscle cells produce lipoprotein lipase
What is CAR – T cell therapy?
remove patient’s blood and get T cells
Insert CAR gene (Chimeric antigen receptor)
Grow millions of Car T cells
Car T cells bind to cancer cells and kill
What are limitations of Car T cell therapy?
Neurological toxicity leading to confusion and delirium
On target off tumour toxicity-bind to normal b cells
allergy to CAR
What is ADA – SKID?
Deficiency in ADA gene leading to unhealthy lymphocytes and severely impaired immune system
How is gene delivery used in ADA – SKID?
Bone marrow derived blood forming stem cells collected
Healthy ADA gene added to stem cells via gamma retrovirus
Modified stem cells are copied
Patient gets chemo to wipe out faulty stem cells
New stem cells are infused to the bone marrow
How does immunogenicity work?
Before treatment screen for antibodies against therapeutic AAV
After treatment antibody has been made and prevents subsequent administration of same AAV vector
Natural killer cells target transgene. Can damage host.
What are the limitations of viral vectors?
Cost
Genotoxicity
Immunogenicity
Packaging required
What are examples of non-viral gene delivery systems?
Impalefection- gene delivery using nano particles
Electroporation - large electrical pulse disturbs phospholipid bilayer
Micro injection - glass micropipettes/metal micro injection directly into nucleus. Very fast, no marker gene needed
Gene gun-Hi velocity micro projectiles- genes in gold micro carrier and loaded into cartridge
What are examples of chemical methods of gene delivery?
Liposomes
Polymers
An organic nano particles
What is an example of a polymer used in gene delivery?
Polyethylenimine (PEI)
What is an example of a lipid vector?
Lipofectin (cationic liposomes)
Positive liposome has negative DNA fused into it via membrane membrane fusion and endocytosis – electrostatic interactions
Forms stable overall positive lipoplex taken up by negative cell into nucleus
What can be added to liposomes to shield from immune system?
PEG
Increases particle circulation time in vivo
Reduces macrophage detection
