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1、viral vector,韩晓,Methods of gene delivery,Viral Vectors:AdenovirusRetrovirusLentivirusAdeno-associated virus(AAV)Herpes simplex virus(HSV)Non-viral vector basedNaked DNA(plasmid DNA):injection or genegunLiposomes(cationic lipids):mix with genesEx-vivoIn vivo,Why use viral vectors,Virus are obligate i
2、ntracellular parasitesVery efficient at transferring viral DNA into host cellsSpecific target cells:depending on the viral attachment proteins(capsid or glycoproteins)Gene replacement:non-essential genes of virus are deleted and exogenous genes are inserted,Generation of viral vector for gene therap
3、y,Replication-competent virus Replication-defective virus Amplicon:doesnt encode structural proteinsCant replicate beyond the first cycle of infectionElements needed to generate amplicon Transfer Vector:plasmid(promoter,gene of interest,ori,packaging signal)Packaging vector(cosmid or cell lines):pro
4、vide the viral structural proteins for packaging of transfer vectorHelper virus(packaging of transfer vector):deleted Packaging signal sequence,Adeno-associated virus vectors,Non-pathogenic human parvovirus,non-enveloped ss DNA virus,4.6 kilobasesDependent on a helper virus(adenovirus or herpesvirus
5、)for replication(dependovirus)AAV-2 mostly used for vector,Adeno-Associated Virus(AAV),Single Stranded DNA VirusViral ITRs&Rep/Cap 5kb CapacityIntegrating/ConcatamericLong Term ExpressionComplex Production&PurificationMulti pDNA&/or Helper VirusLower Titre Than AdenovirusSerotype Differences In Rece
6、ptorsAAV2 Heparan SulphateAAV5 Sialic Acid,Generation of adeno-associated virus vector,Characteristics of AAV vector,AdvantagesIntegration and persistent expressionNo insertional mutagenesisInfecting dividing and nondividing cellsSafeDisadvantagesSize limitation,4.9 kbLow titer of virus,low level of
7、 gene expression,Adenoviral vectors,Non-enveloped ds DNA,36 kilobasesEarly proteins(E1A,E1B,E2,E3 and E4),late proteins(L1-L5)Causes a benign respiratory infections in humanSerotypes 2 and 5 are commonly used as vectors,Early generations of adenoviral vector(replication defective),Gutless Adenoviral
8、 vector(Amplicon),Modification of the tropism of adenovirus vector,Adenovirus fiber binds to CAR(coxsakie and adenovirus receptor,CAR),receptor which is ubiquitousModify the fiber protein,Characteristics of adenoviral vector,Advantages High titersBoth dividing and non-dividing cellsWide tissue tropi
9、smEasily modify tissue tropismDisadvantagesTransient expression(not good for genetic diseases)Highly immunogenicHigh titers of virus can be toxicMore suitable for cancer immunotherapy,Retroviral vector,Moloney murine leukemia virus(MuLV)Generation of replication defective retroviral vectorTransfer p
10、lasmid vector:Gene of interestLong terminal repeats(LTR):promoter,polyA,integration,replication and reverse transcriptionPrimer binding site(PBS)(origin of replication)RNA packaging signalPoly purine tract(important for replication)Packaging vectorCell line stably transfected with plasmid constructs
11、 containing Gag/pol and Env,Generation of retroviral vector,Pseudotyped retroviral vector,Characteristics of retroviral vector,AdvantagesIntegration:permanent expressionPseudotyped virusDisadvantagesOnly infecting dividing cellsInsertional mutagenesis(tumor formation)Activate oncogenesInhibit tumor
12、suppressor genes,Lentiviral vectors,Infection of non-dividing cells(hepatocytes,neurons)HIV,a human lethal pathogenDelete accessory genesProvide an envelope from a non-retrovirus(VSV)Develop vectors from lentiviruses of non-human pathogensSIV,FIV,EIAV etc,Herpesvirus vectors,Herpes simplex virus 1,m
13、ild disease in human,no riskLinear ds DNA,152 kb,about half of the total 81 genes are non-essential for virus replication40-50 kb of foreign DNA can be accommodatedNeurotropic virus,target to nervous systemReplication defective amplicon particles,Comparison of different viral vectors,Viral vectortit
14、ersmanupilation of immunogenicityinfecting of tropism non-dividing cellsAdenovirus1011terrificvery highyesRetrovirus107goodlowonly lentivirusHerpesvirus107not so goodlowyesAAV107not so goodlowyes,Gene therapy,Gene therapy:to correct a genetic defect by transferring of a functional normal copy of the
15、 gene into cellsExamples of diseases caused by genetic defectOrnithine transcarbamylase(OTC deficiency)Hemophilia(blood coagulation factors VIII or IX)SCID(severe combined immunodeficiency)Muscular dystrophy Cystic fibrosisSickle cell anemia,Application of gene therapy,Genetic disorder(deficiency):O
16、TCCancer Genetic predispositionMutation in oncogene or tumor suppressor geneAutoimmunity diseases:rheumatoid arthritisDelivery of counteracting geneDiseases involve several genes and the environmental interact:diabetes,Factors to be considered in Gene therapy,How to deliver genes to specific cells,t
17、issue and whole animals?(methods of delivery)How much and how long the introduced gene will be expressed?The site and dose of gene delivery Is there any adverse immunological consequence of both delivery vehicle(Virus)and the gene in animals?Is there any toxic effects?,Death of 18-year old Jesse Gel
18、singer,Liver disease:OTC deficiency(genetic disease)University of PennsylvaniaHigh dose of adenoviral vector(E1 and E4 genesdeleted)carrying the normal copy of OTC gene was administeredSuspected cause of death-Toxicity of high titer adenoviral vector-High immunogenicity of adenoviral vector(an immun
19、e revolt),A case of leukemia in a SCID child treated with a retroviral vector,SCID disease or Bubble boy disease(T cell deficiency)Overall quite successful,over 1000 peoples received retroviral gene therapy A French babys treated with retroviral vector 3 years agoA leukemia-like illness developed th
20、is summer.Nine other children treated same time show no sign of leukemiaBut the side effect isnt a big enough risk yet that genetic experiments for children with an often fatal immune disease should stopPeople receiving retroviral gene therapy should be warned about the risk of developing leukemia,谢谢!,
