Seminar Lecture 1: Apicomplexes: T. gondii Flashcards
What are the 2 apicomplexes we focus on?
Toxoplasma and plasmodium
Explain the life cycle of Toxoplasma gondii
a. cat poops out unsporulated oocyst (immature)
b. matures into sporulated oocyst and enters enviro
c. gets picked up by intermediate host (mammals/ birds) and becomes a tissue cyst
d. humans ingest the tissue cyst (bradyzoites) from raw meat/ organ transplant/ blood transfusion
e. If a pregnant human ingests a tachyzoite, it can cause congenital defects
____ are the only known definitive host of toxoplasma gondii
cats
Tachyzoites are the ___ growing life stage of toxoplasma gondii
fast
*tachos are fast
Bradyzoites are the ___ life stage of toxoplasma gondii, found in the tissue cyst in the ___
slow
cat
brady is slow
In T. gondii, mature oocysts turn into _____ in the intermediate host. They can also turn into ___–> cysts
tachyzoites
bradyzoites
What are the 3 main ways of contracting T. gondii?
- food-borne (ingestion)
- zoonotic (animal-human)
- congenital
T. gondii bradyzoites are the __-replicating form found in cats. They form ____
*can also be in an intermediate host as a ___ ___
slow
oocysts
dormant cyst
T/F
T. gondii sporulated oocysts can last for a very long time in the enviro (water/food/soil) and can even withstand freezing
true
Does there need to be another intermediate host in order for humans to contract T. gondii?
No
Sporulated oocysts shed into the environment can be directly ingested by humans (drinking water, food, etc) without it entering another intermediate host first
What’s an oocyst vs a cyst?
Oocyst= thick-walled cell with a zygote in it, so sexual reproduction
Cyst= the dormant stage. Asexual reproduction
The trophozoite and tissue cyst represent stages in asexual multiplication (______), while the the oocyst is formed by sexual reproduction (_____ or ______). All 3 forms occur in domestic cats and other felines, which are the ______hosts and support both schizogony and gametogony.
schizogony
gametogony or sporogony
definitive
Toxoplasmosis is infective to all ___-blooded mammals. Cats are the ___ host and birds/ mammals are the ____ hosts
warm-blooded
definitive
intermediate
T/F
T. gondii is generally asymptomatic
true
only concern is if you’re pregnant –> congenital issues/ miscarriages
Can toxoplasmosis migrate across the placenta?
Yes; severe implications for fetal development
Can toxoplasmosis cross the blood-brain barrier?
yes
Bradyzoites invade the ___ tissues of the cat and reproduce asexually (______), producing _____. These differentiate into micro or macrogametes.
Bradyzoites are known as the “resting” stage (b/c of __ reprouction) and they’re latent tissue cysts, causing ___ infection
intestinal
schizogony
merozoites
slow
chronic
Sporozoites are in the released from the ___ (so they’re in the definitive host).
Sporozoites are released in ____ following ___ (asexual/ sexual) reproduction
cat
oocysts
sexual
Tachyzoites are in ____ or other animals. Asexually replicate _____ inside host cells (then burst them) in the parasitophorous vacuole
humans
quickly
What is the parasitophorous vacuole?
The parasitophorous vacuole (PV) is a structure produced by apicomplexan parasites in the cells of its host. The PV allows the parasite to develop while protected from the host cell’s phagolysosomes (which destroy pathogens).
Tachyzoites replicate by endodyogeny (asexual reproduction) inside the PV
T/F
some tachyzoites turn into bradyzoites
true
tachyzoites –> bradyzoites –> cysts –> can turn back into tachyzoites
Is toxoplasmosis intracellular or extracellular?
intracellular- inside the host cell
- occurs in nucleated cells (eg. muscle cells, epithelial cells, neurons… any cell with a nucleus)
T. gondii is characterized by 4 particular features:
- conoid structure to assist in host cell invasion
3 Apical secretory organelles for movement, attachment, and invasion of host cells:
- micronemes
- rhoptries
- dense granules
*be able to label these on a diagram
what are dense granules?
organelles of Toxoplasma gondii; secretory vesicles that play a major role in the structural modifications of the parasitophorous vacuole
The parasitophorous vacuole is the primary ____ for the parasite. It resists typical ____ function; has similar ____ to the host so evades the immune response.
It’s typically ______, which is easy because it can cross the blood-brain barrier
protection
lysosomal
epitopes (the part of an antigen that is recognized by the immune system)
cerebral (in the brain)
