Shillitoe Flashcards
(7 cards)
Explain mechanisms by which viruses encode and express their genes
Viral genes are eukaryotic
Gene expression in viruses is regulated by
cellular transcription factors (this explains tissue-specificity of many viruses)
Viral genomes are efficient:
- No space is wasted
- Reading frames can overlap on the same strand
- Reading frames can overlap on the complementary strand
- Ribosomal frame shifting changes amino acid sequence
- Alternative splicing of RNA changes amino acid sequence
- Expression of polyproteins makes 1 promoter enough
Why are viral mutations important?
Allow epidemiological studies
e.g. MERS
Allows live vaccines to be made
e.g. early polio vaccines
Can produce new antigens which avoid immunity
e.g. Influenza antigenic drift
Can lead to drug resistance
e.g. Protease of Hepatitis C
Integration of viral genome can cause disease
e.g. Papillomavirus in cervical cancer
What is interference?
infection by one virus tends to prevent infection by another by blocking of receptors
competition for resources
production of interferon or other anti-viral agents
Define the different virus interactions
Complementation - when a gene function of one virus replaces a mutated or missing gene of another. This allows defective viruses to grow
Phenotypic mixing - exchange of capsid proteins leading to a pseudotype virus
Recombination - The exchange of genes by crossing over at regions of homology. Produces a hybrid virus
Reassortment - the rearrangement of parts of a segmented genome to form a new set of segments
Describe gene therapy
Gene therapy aims to correct or prevent disease by transfer of appropriate genes to the patient
Steps in gene therapy development:
- Delete an essential gene from virus
- Insert that gene into ‘complementing’ cell
- Clone the therapeutic human gene into virus
- Grow the virus in the complementing cell
- Test virus in cells, animals, humans
What are some of the diseases that might be treated with gene therapy?
Retinal disorders
Hemophilia
Immune disorders
Liver enzyme deficiencies
Cystic fibrosis
What are the problems with gene therapy?
- Transient expression of foreign gene
- Requirement for very high doses of virus vectors
- Inflammatory response to virus vector
