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Gene therapy With Adeno -Associated Virus

Gene therapy With Adeno -Associated Virus. Noushin rajaeie. What is Gene Therapy. A technique for correcting defective genes that are responsible for disease development.There are four approaches : A normal gene inserted to compensate for a nonfunctional gene.

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Gene therapy With Adeno -Associated Virus

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  1. Gene therapyWith Adeno-Associated Virus Noushin rajaeie

  2. What is Gene Therapy • A technique for correcting defective genes that are responsible for disease development.Thereare four approaches: • A normal gene inserted to compensate for a nonfunctional gene. • An abnormal gene traded for a normal gene • An abnormal gene repaired through selective reverse mutation • Change the regulation of gene pairs

  3. Gene therapy requires three things: • the identification of thedefect at the molecular level • a correcting gene • a way tointroduce the gene into appropriate host cells (i.e., a vector). • Choices of Vectors For Gene therapy:

  4. The ideal vector system for gene therapy: (1) an adequate carrying capacity (2) to be undetectable by the immune system (3) to be non-inflammatory (4) to be safe to the patients with pre-existing lung inflammation. (5) to have an efficiency sufficient to correct the cystic fibrosis phenotype. (6) to have long duration of expression and/or the ability to be safely re-administered.

  5. The history of gene thropy: • In the 1980:Scientists began to look into gene therapy. • In the 1990:The first gene therapy was performed for treatment of SCID. • In the1993 : Trials using liposome-mediated CFTR gene transfer • In the1995:The first cystic fibrosis gene therapy clinical trials used an adenovirus vector • In the 1998:Trials using adeno-associated virus to deliver gene.

  6. How Gene Therapy With Virus Works: • A vector delivers the therapeutic gene into a patient’s target cell. • The target cells become infected with the viral vector. • The vector’s genetic material is inserted into the target cell. • The therapeutic gene causing the cell to return to a normal state.

  7. A virus insert its genes into the host cell's genome. This virus has three genes - A, B and C: 1)Gene A encodes a protein which allows this virus to insert itself into the host's genome. 2)Genes B and C actually cause the disease this virus is associated with.3)Replace B and C with a beneficial gene. Thus, the modified virus could introduce your 'good gene' into the host cell's genome without causing any disease.

  8. Adeno-associated virus (AAV) • A small viruswhich infects humans and some other primate species. • AAV dose not cause disease • AAV causes a very mild immune response. • AAV is a candidate for gene therapy. • AAV belongs to the genus Dependovirus,turnbelongs to the family Parvoviridae. • The virus is a small (20 nm). • AAV is a replication-defective, non envelopevirus.

  9. AAV life cycle: AAV undergoes productive infection in the presence of adenovirus co infection. characterized by: • genome replication • viral gene expression • virion production • In the absence of helper virus infection: AAV binds to its receptor, traffics to the nucleus, and integrates into the distal end of chromosome 19. • In the presence of an Ad coinfection:theAAV genome is replicated as replicative form monomers and dimers (RFM, RFD) yielding progeny virus.

  10. AAV’s life regulated by:1)complex interactions between the AAV genome and AAV 2) adenoviral 3)host protein

  11. (AAV) vectors: • Adeno-associated viral (AAV) vectors are based on a non-pathogenic, replication deficient member of the parvovirus family with a 4.7 kb single-stranded DNA genome. • AAV-mediated gene transfer is under investigation for treatment of a large number of diseases.

  12. Producing recombinant AAV vectors

  13. The advantages of (AAV)vectors: • AAV is non-pathogenic and safe for use as a vector. • All viral genes can be deleted from recombinant AAV (rAAV) vectors. • AAV can efficiently infect both dividing and nondividing cells in muscle liver, brain, retina , heart , and pancreas. • Vector administration does not elicit a strong cellular immune reaction.

  14. The disadvantages with AAV vectors: • limited tissue tropism for serotypes • targetedgene delivery to specific cell populations. • preexisting immunity due to prior exposure of the majority of the human population with multiple AAV serotypes and a limited transgene carrying capacity.

  15. AAV CLINICAL TRIALS: AAV vectors have been used in over 38clinical trials worldwide Including: • retinal diseases • Hemophilia • congestive heart failure • lipoprotein lipase deficiency • Parkinson's disease • Cystic fibrosis

  16. Gene Therapy for Cystic Fibrosis: • CF, a lethal, autosomal recessive disease • in CF the CF transmembrane regulator (CFTR) is inactivated by mutation • This mutation leads to the accumulation of thick secretions in the lung • CF is an autosomal recessive disease and is the most common lethal genetic disease among whites.

  17. Cystic fibrosis as an ideal candidate for gene therapy: • it is a single gene defect • it is a recessive condition, with heterozygotes being phenotypically normal • the main pathology is in the lung, which is accessible for treatment • it is a progressive disease with a virtually normal phenotype at birth

  18. Hemophilia • Two of the required enzymes are factors VIII and IX; a lack of the former results in hemophilia A, and a lack of the latter results in hemophilia B. • A factor IX AAV vector could be used to “cure” mice with hemophilia B.

  19. Parkinson’s disease • It is a chronic neurodegenerative disease • In Parkinson’s disease, a loss of dopaminergic neurons leads to the loss of inhibitory gamma aminobutyric acid-sensitive input to the subthalamic nucleus. • a study in which 12 patients with advanced Parkinson’s disease had an AAV vector carrying a transgene encoding glutamic acid decarboxylase injected into the subthalamic nucleus on one side

  20. References: • Berns,K.Daya,sh.(2008) Gene Therapy Using Adeno-Associated Virus Vectors, Clinical Microbiology Reviews, Vol. 21, No. 4:583–593 • Collaco,R.F.Tremp,J.P(2000) A Method for Helper Virus-Free Production of Adeno-Associated Virus Vectors. • Kenneth,H.Roland,W.Warrington,J.r (2006)Treatment of human disease by adeno-associated viral gene transfer, Hum Genet ,119: 571–603. • Kwon,I.Schaffer,D(2008) Designer Gene Delivery Vectors: Molecular Engineering and EvolutionofAdeno-Associated Viral Vectors for Enhanced Gene Transfer, Pharmaceutical Research, Vol. 25, No. 3

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