Mutation Flashcards
Consequences of mutation
- Opportunity for adaptation
- Risk of losing advantages/properties
What are the causes of mutation
Failures in NA replication of:
- Cell
- DNA virus
- RNA virus
Give the types of mutation incidence
Spontaneous/Induced
Causes of induced mutation
- Irradiation
- Mutagenic drugs - halogenated uridine
Give the forms of mutation that can occur in the NA chain
- Point mutation
- Sequence mutations
- Substitution
- Insertion
- Deletion
- Inversion
- Frame shift
Give the final types of mutation
- Silent mutation
- Lethal mutation
- Conditionally lethal mutation
- Beneficial mutation
Silent mutation
- No phenotypic change
- Untranslated region
- Redundant translation code
- Non-important amino acid produced
Lethal mutation
Nonsense (stop)
or
Missense (amino acid change)
Conditionally lethal mutation
Changes in the multiplication activity
i.e. Thermo-sensitive mutants
Give the history of CPV2
- 1978: CPV2
- 1979: CPV2a
- 1984: CPV2b
- 2000: CPV2c
List the influences of mutations on the viral phenotype
- Antigenic change
- Changes in host species specificity
- Changes in organ specificity
- Different tissue tropism (cell cultures)
- Virulence variants
- Cytopathic effects, plaque formation
- Temperature optimum
Antigenic change
- Escape mutants
- Influenza - antigenic drift
Changes in host species specificity
- Feline panleukopenia → Canin parvoenteritis
- SIV → HIV
Changes in organ specificity
- EHV1: Abortion ⇔ EHV4: rhinopneumonitis
- IBR: Rhinotracheitis ⇔ IPV: vulvo-vaginitis
Different tissue tropism (cell cultures)
Bovine adenovirus - Kidney/testicular cells
Virulence variants
- Newcastle disease: Lento-, Meso-, velogenic strains
- Avian influenza: Haemagglutinin protease cleavage site
Cytopathic effects, plaque formation
Aujeszky’s disease virus, BVDV
Temperature optimum
- Rhinoviruses, canine herpesvirus
- Rabies vaccine strains
Effect of mutation on evolution
- Selective advantages
- Environmental pressure
- Adaptation, niche
- Virus’ evolution is a million times quicker than the host’s
Mutation opportunity for protection
- Avirulent strains with conserved antigenic properties
- Attenuated vaccine strains
- Biotechnology, genetic engineering: Accuracy
Mutation effection virus strain stabilisation
- Protection from mutations - low passages
- Seed virus, virus banks
- Freeze drying
