Lec 13 - Viral diversity and evolution Flashcards
How does mutational diversity arise in viruses?
Lack of proofreading ability in viral polymerase
What is recombination?
Coinfection with offspring a combo of both due to proteins recognising similar regions
What is reassortment?
Coinfection by segmented viruses so offspring is a combo of both
Compare antigenic shift and drift
Shift: big change over short time
Drift: small change over long time
How does genome size influence mutation rate?
Bigger genomes tolerate less mutations bc too many genes
Smaller genomes tolerate more mutations
How have lentiviruses coevolved with their host?
SIV replicates in particular primate species by overcoming the TRIM5 protein in that species
How does TRIM5 block lentiviruses?
- Blocks uncoating
- Labels capsid for proteasome for degradation
- Labels capsid for virophagy/autophagy degradation
Where do most medically important emerging viruses come from and why?
Mammals because most similar conditions to humans
What is a consensus sequence?
An average virus/sequence calculated from the variants present in the host
What is a quasispecies cloud?
The mutant spectrum using the consensus sequence
What forms a natural bottleneck in HIV transmission and how does HIV survive it?
Multiple layered mucosa
CCR5 HIV infects CCR5 macrophages abundant in mucosa then CD4+ T cells
What are the features of a transmitted founder (TF) virus?
- Resist IFN-y
- Better dendritic cell interaction
- Higher replication rate
What antibodies are formed from HIV infection?
Initial autologous neutralising antibodies select for escaping mutants to make cross-reactive neutralising antibodies
What does Muller’s ratchet refer to?
HIV in asexual populations declines in fitness from decreasing virulency with increasing diversification
Explain error threshold in RNA viruses
The info that must be maintained for virus survival.
Too much mutation: lose info
Too little mutation: killed by host
Bypass immunity too well: kill host with no viral replication
