Seminar Lecture 1: Apicomplexes: T. gondii

Question 1

What are the 2 apicomplexes we focus on?

Answer 1

Toxoplasma and plasmodium

Question 2

Explain the life cycle of Toxoplasma gondii

Answer 2

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

Question 3

____ are the only known definitive host of toxoplasma gondii

Answer 3

cats

Question 4

Tachyzoites are the ___ growing life stage of toxoplasma gondii

Answer 4

fast

*tachos are fast

Question 5

Bradyzoites are the ___ life stage of toxoplasma gondii, found in the tissue cyst in the ___

Answer 5

slow
cat

brady is slow

Question 6

In T. gondii, mature oocysts turn into _____ in the intermediate host. They can also turn into ___–> cysts

Answer 6

tachyzoites

bradyzoites

Question 7

What are the 3 main ways of contracting T. gondii?

Answer 7

1. food-borne (ingestion)
2. zoonotic (animal-human)
3. congenital

Question 8

T. gondii bradyzoites are the __-replicating form found in cats. They form ____

*can also be in an intermediate host as a ___ ___

Answer 8

slow
oocysts

dormant cyst

Question 9

T/F

T. gondii sporulated oocysts can last for a very long time in the enviro (water/food/soil) and can even withstand freezing

Answer 9

true

Question 10

Does there need to be another intermediate host in order for humans to contract T. gondii?

Answer 10

No
Sporulated oocysts shed into the environment can be directly ingested by humans (drinking water, food, etc) without it entering another intermediate host first

Question 11

What’s an oocyst vs a cyst?

Answer 11

Oocyst= thick-walled cell with a zygote in it, so sexual reproduction

Cyst= the dormant stage. Asexual reproduction

Question 12

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.

Answer 12

schizogony

gametogony or sporogony

definitive

Question 13

Toxoplasmosis is infective to all ___-blooded mammals. Cats are the ___ host and birds/ mammals are the ____ hosts

Answer 13

warm-blooded

definitive

intermediate

Question 14

T/F

T. gondii is generally asymptomatic

Answer 14

true

only concern is if you’re pregnant –> congenital issues/ miscarriages

Question 15

Can toxoplasmosis migrate across the placenta?

Answer 15

Yes; severe implications for fetal development

Question 16

Can toxoplasmosis cross the blood-brain barrier?

Answer 16

yes

Question 17

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

Answer 17

intestinal

schizogony
merozoites

slow
chronic

Question 18

Sporozoites are in the released from the ___ (so they’re in the definitive host).

Sporozoites are released in ____ following ___ (asexual/ sexual) reproduction

Answer 18

cat

oocysts
sexual

Question 19

Tachyzoites are in ____ or other animals. Asexually replicate _____ inside host cells (then burst them) in the parasitophorous vacuole

Answer 19

humans

quickly

Question 20

What is the parasitophorous vacuole?

Answer 20

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

Question 21

T/F
some tachyzoites turn into bradyzoites

Answer 21

true

tachyzoites –> bradyzoites –> cysts –> can turn back into tachyzoites

Question 22

Is toxoplasmosis intracellular or extracellular?

Answer 22

intracellular- inside the host cell

• occurs in nucleated cells (eg. muscle cells, epithelial cells, neurons… any cell with a nucleus)

Question 23

T. gondii is characterized by 4 particular features:

Answer 23

• 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

Question 24

what are dense granules?

Answer 24

organelles of Toxoplasma gondii; secretory vesicles that play a major role in the structural modifications of the parasitophorous vacuole

Question 25

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

Answer 25

protection

lysosomal

epitopes (the part of an antigen that is recognized by the immune system)

cerebral (in the brain)