Toxoplasmosis

Question 1

Facts about Toxoplasma gondii

Answer 1

• obligate intracellular protozoa
• definite host: cat
• human is intermediate host
• Sporozoites are infectious agent

Question 2

How do humans get infected?

Answer 2

1. feline feces (infectious after 3-5 days) -> cat owners
2. gardening
3. playing golf (sand bunker)

flies can also transmit Toxo

Question 3

3 forms of Toxo

Answer 3

1. Oocyst
   
   • only in cats, eggs of Toxo, one is enough to cause infection
2. Tachyzoites
   
   • fast replication, in circulation 2 weeks after infection
3. Bradyzoites
   
   • 2-2000 in cysts
   • intermediate host

Question 4

What are the mechanisms Toxo uses to enter a cell?

Answer 4

• inducing formation of parasitophorous vacuole (intracellular) -> no acidification, prevents apoptosis
• helps producing LXA4 -> reduces immune response

Question 5

Describe the 3 Toxo strains and there outcome

Answer 5

Type I:
- no elimination of Toxo in macrophages, resulting in acute death by excessive parasitic burden

Type II:
- elimination of Toxo in macrophages, but acute death by inflammation

Type III:
- no elimination of Toxo in macrophages, but control of parasitic growth -> chronic infection
- late activation of effecto mechanism eventually can clear Toxo in macrophages

Question 6

How to identify an acute or previous infection?

Answer 6

test for specific ABs:
1. no IgG -> no infection
2. IgG detected:
a) IgM negative -> infection over 2 years ago
b) IgM low -> false positive; infection in past 2 years, new infection (draw second sample few weeks later)
c) IgM high -> infection in last 3-6 months

if ABs detected you have bradyzoit cysts in body

Question 7

Toxo infection model

Answer 7

• inoculation of mice with cysts (minced brain tissue)
• modulates immune response
• can alter behaviour of mice
• parasitic burden is higher in C5aR2-/- mice