Host-Parasite Interactions 4

Front 1

What causes much of the damage in many parasite infections?

Back 1

Immunopathology

Immune evasion

Front 2

Why is maximum virulence by the parasite, as well as maximum response by the host not often seen in infection?

Back 2

Fitness costs are high for both - an equilibrium is established between the two

Front 3

Generally speaking, what causes virulence in host following parasite infection?

Back 3

Resource extraction can cause virulence by depletion - if extraction is destructive this can cause pathogensis.

Immune evasion by the host can cause pathogenesis.

Front 4

How might a parasite demonstrate passive evasion?

Back 4

Hide in immune-priveleged sites

Becomes "invisible" to immune system

Antigenic variation

Quiescence (inactivity)

Front 5

Generally speaking, how can parasites actively interfere with an modulate the immune system of the host?

Back 5

Express gene products which interferes with the host's immune response

Front 6

Hosts can acquire concomitant immunity when they have a low-level parasite infection, what is this? What are the implications of it?

Back 6

Simultaneous immunity and infection which prevents reinfection - may be able to use this idea for vaccinations.

Front 7

Give 2 examples of parasites against which hosts can develop concomitant immunity.

Back 7

Taenia - prevents reinfection of adult tapeworm in DH, immune IH my find cyscticerci in tissues

Babesia

Front 8

What is quiescence? What is the effect of using this as a method?

Back 8

Metabolic slowdown (slows/stops movement or life cycle functions delayed)

Reduces metabolic products that stimulate host response. (Excretory secretory antigen highly immunogenic)

Reduces virulence and immune evasion

Front 9

Briefly describe the Toxoplasma gondii life cycle.

Back 9

Cats (DH) ingest infective oocysts.

Transmitted to IH through oocysts, carnivorism, or transplacentally (mostly in humans and sheep).

Front 10

What is a tachyzoite?

Back 10

Rapidly dividing crescent-shaped stage stage of development of acute tissue phase

Front 11

What is a bradyzoite?

Back 11

Slow growing, quiescent, comma shaped form, found in clusters within pseudocyst in tissues (mainly in muscles and brain).

Protected against immune response, presented in chronic toxoplasmosis.

Front 12

Where does the quiescent larvae of Trichinella spiralis reside? What can immune response cause?

Back 12

Muscle - immune inflammatory response causes myocytis

Front 13

Which immune response is insufficient in tackling Trichinella infection?

Back 13

TH2 response

Front 14

What is found on Fasciola hepatica? What is it made from and describe its roles and how it does this?

Back 14

Cathespin L - Made up of cysteine proteases, primary role is digestion of alpha-alpha from haemoglobin.

Acts by cleaving Fab from Fc region on immunoglobulins, preventing antibody-mediated attachment of eosinophils to parasite surface.

Front 15

Which immune-priveleged site can Fasciola hepatica occupy in humans?

Back 15

Eye

Front 16

Is Schistosomiasis a zoonoses?

Back 16

Yes

Front 17

Give examples of Schistosoma species.

Back 17

Schistosoma bovis

S. mattheei

S. indicum

S. japonicum

S. nasalis

Front 18

Describe what is contained the the trematode tegument.

Back 18

Double lipid bilayer

Glycocalyx (glycoprotein and polysaccharide)

Can coat with host antigens (e.g. Schistosoma) - RBC antigens, MHC, serum glycoproteins and this is called molecular mimicry (evades immune rresponse).

Front 19

What role does the glycocalyx play in the trematode tegument (e.g. Fasciola hepatica)?

Back 19

Undergoes dynamic changes during growth and maturation in host - does so by regularly shedding and replacing (more rapid in juvenile than adult) which allows evasion of immune responses such as cell-mediated damage by eosinophils.

Front 20

What happens to trematode shedding when specific antibodies are created? What happens to the antibodies?

Back 20

Rate of shedding increases - the outer tegument forms complexes with antibodies to reduce eosinophil attachment. Can also shed to dislodge eosinophil.

Front 21

Where is trypanosomiasis found?

Back 21

Tsetse-infected areas of sub-Saharan Africa

Front 22

Is trypanosomiasis zoonotic?

Back 22

Yes - causes sleeping sickness in humans

Front 23

Give some examples of Trypanosoma species.

Back 23

Trypanosoma brucei

T. evansi

T. congolense

T. simiae

T. vivax

Front 24

Which of the following diseases is zoonotic?

Back 24

Trypanosoma vivax

Trypanosoma congolense

Trypanosoma evansi

Trypanosoma brucei

Trypanosoma simiae

Front 25

When parasites undergo antigen variation (e.g. trypanosomes, Plasmodium), what happens to the immune responses over time?

Back 25

Immune response goes in waves as the parasite is continually shed; this persists until immune system is exhausted.

Front 26

What does Leishmania use for growth factor?

Back 26

Host cytokines

Front 27

Which animals immune response gives resistance to Leishmania infection, and which results in disease? Explain.

Back 27

TH1 mediated response, which uses IFN-gamma, IL-2, TNF-alpha, initiates macrophage activation, production of NO and kills parasite within macrophage resists the disease.

TH2 mediated response produces IL-4, IL-10 and initiates a humoral response to infection; this does not eliminate the disease, so intracellular parasites persist and disease occurs.

Front 28

Summarise the ways in which subversion of immune responses by parasites occur.

Back 28

Intracellular apicomplexan parasites live in non-fusogenic parasitophorous vesicles (e.g. Eimera, Cryptosporidium, Toxoplasma, Babesia)

Hijack cellular processes, subverting immune responses (e.g. protein synthesis, membrane trafficking, modulate gene expression, antigenic presentation, apoptosis)

Polyclonal Ig synthesis, wherein large quantities of ineffective antibodies are made (e.g. Trypanosoma, Schistosoma)

May consume immunoglobulin (e.g. taeniid tapeworm cystercerci)

Front 29

Name the parasite that causes subversion of ant host behaviour and how this occurs.

Back 29

Dicrocoelium dendriticum - Once the ant IH has consumed the parasite from snail slime (snails get it from faeces), the migrating cercaria invades the brain, establishing itself in the ventral suboesophageal ganglion ("Hirnwurm" or cerebral larva). The ants are simulated to ascend on pasture vegetation and fix themselves there with their mandibles.

Front 30

Aside from Dicrocoelium dendriticum, name another parasite that infects its intermediate host and manipulates it into making itself more likely to get caught by the prey (DH).

Back 30

Toxoplasma gondii - Infects rodents so more likely to be caught by cats