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15 Cards in this Set
- Front
- Back
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Describe the idea of a virus particle that is infectious but replication-defective
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These are viruses that infect cells and transport their DNA into the nucleus, but cannot reproduce and release new infectious particles; they are infective for only one round
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What is a "packaging" cell line and how is it used?
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It is a cell line that expresses viral structural proteins necessary for the development of a retrovirus but does not package the viral gag, pol, or env mRNAs
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What viral sequences must be available in the plasmid used to construct a retroviral vector
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The upstream and downstream LTR sequences, the psi RNA packaging sequence
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What are the major advantages of using retroviral vectors?
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They integrate genome DNA into chromosomal DNA more efficiently than artificial DNA uptake and other virus vectors such as Adeno and Parvo (which don't integrate DNA)
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What is used to construct a retrovirus vector?
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A bacterial plasmid with integrated proviral DNA that lacks all retroviral sequences (except LTRs and packaging sequences), and the desired sequence for insertion in the form of cDNA
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What does the packaging cell line do with the proviral DNA of the unintegrated plasmid?
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It transcribes it into genome-like RNA and packages it into the structural viral proteins
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What is the advantage of lentivirus vectors as opposed to murine retrovirus vectors?
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Lentivirus retroviral vectors are able to integrate pro-viral DNA in both non-dividing and and dividing cells, while murine vectors can only integrate in dividing cells
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What is the advantage of pseudotyped retroviruses compared to murine viruses with amphotrophic Env protein?
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They have increased virion stability and extended host range with the rhabdovirus envelope glycoprotein replacing the retrovirus Env protein
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The first retroviral vectors were made from what sort of retrovirus?
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Murine retrovirus (rodents)
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What is the major risk for using retro/lenti virus vectors?
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Insertional mutagenesis
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What is meant by "pseudotyping" retroviral vectors?
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They have been provided with the G glycoprotein from VSV (a rhabdovirus) to give a wider host species range and greater stability of the viral envelope
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What are the differences between adenoviral and retro/lentiviral vectors for gene therapy?
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Adenovirus does not integrate into the chromosome and has a decreased capacity for larger cDNA sequences in recombinant adenoviral genomes
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What is the disadvantage of using first generation adenoviral vectors?
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They lack the E1 gene, which renders them "leaky" and results in low-level transcription of many genes, which are processed and presented on the surface of the cell, causing the CD8 CTL response to kill the infected cells
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What is an advantage of using adenoviral-associated viruses (Parvo) vectors?
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The dsDNA form of the genome can be integrated into the chromosome without the use of an adenovirus helper and can be maintained long-term
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What is the major disadvantage to using adenoviral-associated viruses (Parvo) as vectors?
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The genome is very small and limits the amount of foreign DNA to 4kb and can have rare insertional mutagenesis
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