Lecture 5 - Pathogen lifecycle

Question 1

Why do we think we can make vaccines for leishmaniasis?

Answer 1

Single life cycle stage responsible for disease
No ‘antigenic variation’ detected to date
Targeting of virulence determinants may not be essential for effective cell-mediated immunity
Sub clinical infection common
- evidence from HIV reactivation
- evidence from active disease surveillance (seropositivity, molecular diagnosis)
Natural resistance to re-infection after clinical cure (leishmanisation)
Epidemiological data on cross-protection

Question 2

What are the obstacles to Trypanosome vaccines?

Answer 2

Two life cycle stages responsible for disease
‘antigenic variation’ detected to date
T.brucei break blood/brain barrier (difficult to design drugs which also break the barrier)
T.cruzi huge genetic diversity
T.cruzi can infect all nucleated cells
T.cruzi reservoirs include multiple wild animals. (difficult to control on epidemiological scale)

Question 3

What are the helminth parasites?

Answer 3

Tapeworms: Cestodes
Taenia spp.
Flukes: Trematodes
Schistosoma spp.
Round worms: Nematodes
Ascaris

Infection by larvae or eggs
Often tortuous migration in host
Adults do not replicate
Eggs / larvae may cause pathology