1. Pathogen diversity - Virulence trade-off theory Flashcards
Structure of the lecture
- SIR modelling
- Conserved/Variable immune targets
- Drivers of evolutionary dynamics
- Virulence trade-off theory
- Virulence and imperfect vaccines
What are the 3 types of SIR model?
1.1
- SIR (e.g., Measles, Rubella)
- SI (e.g., HIV, TB)
- SIRS (e.g., Influenza and SARS-CoV-2)
Where do conserved targets of immunity occur?
2.1
SIR/SI pathogens
E.g., smallpox, polio, measles, HepB, diptheria, pertussis
Where do variable targets of immunity occur?
2.2
SIRS pathogens
e.g., pneumococcus, meningococcus, malaria, hiv, papilloma
What is a good example of conserved vs., variable targets?
hemagluttinin.
conserved in measles
variable in influenza
what are the three main factors that drive pathogen evolutionary dynamics
3.1
- host interactions
- genetic makeup
- R0
how do host interactions drive pathogen evolution?
3.2
genetic variants that prevent pathogen entry
genetic variants that improve host survival
genetic diversity that aids host immunity at a population level
how does pathogen genetic makeup influence their evolutionary dynamics?
3.3
driven by regulatory genes, structural genes and regulatory genes
how does R0 influence pathogen evolutionary dynamics?
3.4
transmission factors
virulence factors
antigenic determinants
an example of the changing evolutionary dynamics of pathogens?
3.5
cps locus
what is virulence trade-off theory?
4.1
pathogens evolve towards optimum virulence, and duration to maximise R0
example of virulence trade-off theory
4.2
trade-off between virulence and transmission in myxoma virus and RHDV
how can imperfect vaccination drive virulence?
5.1
R0 = BD
Therefore, an unvaccinated proportion of the population can increase virulence
example of imperfect vaccination driving virulence?
5.2
marek’s disease in poultry chickens
