viral genetics
DESCRIPTION
Viral Genetics. Hsiao-Sheng Liu 劉校生 國立成功大學微生物暨免疫學研究所. The objectives. What kind of genetic changes are detected in viruses? The effects of viral genetic changes on viral virulence The application of viral mutants. What kind of genetic changes are detected in the virus?. A. Mutation - PowerPoint PPT PresentationTRANSCRIPT
Viral GeneticsHsiao-Sheng Liu 劉校生 國立成功大學微生物暨免疫學研究所
The objectives
• What kind of genetic changes are detected in viruses?
• The effects of viral genetic changes on viral virulence
• The application of viral mutants
What kind of genetic changes are detected in the virus?
A. Mutation– Poor fidelity of viral polymerase: RNA-dependent RNA polymerase;
RNA virus lack of genetic error-checking mechanism (one error per 1x10 nucleotides)
– Rapid replication rate
3
A. Mutation
B. Recombination (Reassortment)
Attenuated virus Violent virus
Recombinant virus
HA HA NANA
HA NAHemagglutinin
NeuraminidaseLipid bilayer
Matrix proteinRibonucleoprotein
• Antigen drift: gene mutation
• Antigen shift: gene recombination
Antig
en
Antige
n
• NP: nucleoprotein
Mutation Recombination
A. MutationB. Recombination (Reassortment)
C. Transcapsidation: Phenotype of A and genome of B
D. Marker rescue
An example of viral genetic changes: SARS
Molecular analyses by RT-PCR:@ A 405 nucleotide segment of the coronavirus polymerase gene was amplified.
From Times
What kind of viral mutants may be generated?
Mutants• Lethal mutant• Plaque mutant• Host-range mutant• Attenuated mutant• Temperature sensitive mutant
What is the application of viral mutants?
Vaccine
Understanding a mutated virus is the first step to find a vaccine
Why the virus is used for gene therapy?
1. Rapidly amplified in appropriate cell
2. Deliver the gene without producing infectious virus
What viruses are used for gene therapy?
Virus-mediated gene transfer in mammalian cells1. Retrovirus2. Adenovirus3. Adenovirus-associated virus4. Herpes simplex virus
What is the defective virus?
A. Defective Interfering viral particle (DI)
B. Pseudovirion: Virus particle contains host nucleic acid
Web site for virology• General virology:
www.tulane.edu/~dmsander/garryfavweb.html
• Taxonomy of viruses: life.anu.edu.au/viruses/Ictv/index.html
• Infectious diseases: www.gen.emory.edu/medweb/medweb.id.html
Genetic change between viral particles
H5N1
H1N1