Facts about Trypanosoma cruzi
- protozoan parasite (class kinetoplastida)
- causes chagas‘ disease
- vector is kissing bug
- common in central and south america
- associated with poor socioeconomic conditions
Name the three important life cycle stages of Trypanosoma
- epimastigote -> multiplies in midgut of insects
- amastigote -> multiplies intracellularly in vertebrate host
- trypomastigote -> extracellular, non-replicative form; circulates through host and infects new cells
Name the two major phylogenetic lineages
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
What is the difference between myotonic and reticulotropic strains?
myotropic: invade muscle
reticulotropic: prefer phagocytic mononuclear cells (liver and spleen)
Diagnosis of Trypanosoma
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)
Treatment of trypanosoma
2 drugs, both only effective shortly after infection
have severe sideeffects
Name challenges animal models for T. cruzi have
course of infection varies widely between models depending on:
- host strain
- parasite strain
- route of infection
- size of inoculum
Animal models for T. cruzi
- 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)
Name parasitic strains
- 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
T. cruzi mouse model
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)
How do you inoculate mice with T. cruzi?
- infection with blood trypomastigote:
- blood trypomastigote obtained from infected (immunodeficient) animal
- inoculation range: 100 - 1x10⁷ - infection with metacylic trypomastigote
- metacyclic trypomastigote obtained from bug
- inoculation range: 200-400
routes:
intraperitoneal, conjunctival (ocular eye surface), s.c., oral
What are the key parameters to monitor an infection?
- 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)
Are there working in vitro models?
Yes, studies with macrophages work in vitro
