Block 1: Bacterial Virulence Factors

Question 1

What does IgA proteases do?

Answer 1

They cleave IgA antibodies and allow the bacteria to adhere to mucosal surfaces

Question 2

Which bacteria secete IgA proteases?

Answer 2

1. S. Pneumoniae
2. H. Influenza type B
3. N. Meningitidis
4. N. gonorrhoeae

Question 3

What does M protein do?

Which bateria consists of this protein?

Answer 3

1.

Prevents opsonization and phagocytosis

It is similar to antigens present in the heart, so Abs that form against the M protein can attack the heart as well.

This leads to Rheumatic Fever

2. S. pyogenes

Question 4

What does Protein A do?

And bacteria has this on its surface?

Answer 4

1. It binds to the Fc portion of IgG Abs, so only the Fab portion of IgG is exposed. It prevents opsonization and phagocytosis.
2. Its found on the surface of S. aureus

Question 5

what is lipid A and what is it a part of?

Answer 5

it is an endotoxin that is on gram negative bacteria. it is attached to LPS.

when it is released, it triggers an immune response.

Question 6

Endotoxins are used only by

Answer 6

gram-negative organisms