Trypanosoma

Question 1

Facts about Trypanosoma cruzi

Answer 1

• protozoan parasite (class kinetoplastida)
• causes chagas‘ disease
• vector is kissing bug
• common in central and south america
• associated with poor socioeconomic conditions

Question 2

Name the three important life cycle stages of Trypanosoma

Answer 2

• epimastigote -> multiplies in midgut of insects
• amastigote -> multiplies intracellularly in vertebrate host
• trypomastigote -> extracellular, non-replicative form; circulates through host and infects new cells

Question 3

Name the two major phylogenetic lineages

Answer 3

T. cruzi I:
- cycles between wild animals and vector (salvation cycle)
- host: marsupials

T. cruzi II:
- cycles between wild animals and vector (salvation cycle) and domestic animals/human and vector (domestic cycle)
- infects placentals

Question 4

What is the difference between myotonic and reticulotropic strains?

Answer 4

myotropic: invade muscle
reticulotropic: prefer phagocytic mononuclear cells (liver and spleen)

Question 5

Diagnosis of Trypanosoma

Answer 5

acute phase: high parasitemia in blood -> microscopy

specific ABs (ELISA)

chronic phase: PCR, hemoculture (incubation of blood sample on medium that supports epimastigote form, xenodiagnosis (uninflected kissing bug feeds on blood -> examine gut content)

Question 6

Treatment of trypanosoma

Answer 6

2 drugs, both only effective shortly after infection
have severe sideeffects

Question 7

Name challenges animal models for T. cruzi have

Answer 7

course of infection varies widely between models depending on:
- host strain
- parasite strain
- route of infection
- size of inoculum

Question 8

Animal models for T. cruzi

Answer 8

• mice (easy, cheap, produces acute and chronic phase of disease)
• hamster
• dogs (resembles human disease in all phases, expensive)
• rats
• rabbits
• monkeys (similar to human chagas disease, closely related to human, expensive)

Question 9

Name parasitic strains

Answer 9

• Y (isolated from human in acute phase)
• CL (isolated from kissing bug)
• Ernane: isolated from patient with cardiac form and megaesophagus
• Benedito: isolated from patient with intermediate form through xenodiagnosis
• Vicentina: isolated from patient with chronic cardiac form through xenodiagnosis

Question 10

T. cruzi mouse model

Answer 10

depending on research question combination needs to be chosen

mice:
- C57BL/6 or /10 -> relatively resistant
- C3H -> susceptible
- BALB/c -> intermediate
- need mice -> highly susceptible (immunodeficient)

T. cruzi strains:
- Tulahuen, Y, RA, Peru (reticulotropic)
- CL, Brazil, Colombia (myotropic)

human disease resembled by BALB/c mice with Colombian strain (inoculation of 100 trypomastigotes)

Question 11

How do you inoculate mice with T. cruzi?

Answer 11

1. infection with blood trypomastigote:
   - blood trypomastigote obtained from infected (immunodeficient) animal
   - inoculation range: 100 - 1x10⁷
2. infection with metacylic trypomastigote
   - metacyclic trypomastigote obtained from bug
   - inoculation range: 200-400

routes:
intraperitoneal, conjunctival (ocular eye surface), s.c., oral

Question 12

What are the key parameters to monitor an infection?

Answer 12

• mortality
• parasitemia (blood examination or xenodiagnosis)
• tissue parasitism (real time PCR or HE microscopy)
• pathology (HE microscopy: signs of inflammation?, measure of transaminases in serum -> liver injury)
• immune response (proinflammatory cytokines through FACS, real time PCR or ELISA)

Question 13

Are there working in vitro models?

Answer 13

Yes, studies with macrophages work in vitro