Host Defenses and Virulence Factors

12 Jun Host Defenses and Virulence Factors

Question
Assignment 8.1 – Host Defenses and Virulence Factors

Name: Date:

1. Host Defenses

a. What are the two broadest categories of host defense?

b. What are some of the innate or non-specific defenses employed by the body?

c. What are some of the components of the adaptive (specific) defenses?

2. Virulence Factors: Exotoxins

a. What type of macromolecule is an exotoxin?

b. What is a neurotoxin? Name one genus of bacteria that produces neurotoxins.

c. What general area of the body do enterotoxins affect?

d. What are cytotoxins?

e. How does the cytotoxin produced by Corynebacterium diphtheriae affect host cells?

f. What is the general description of A-B toxins (in terms of the function of each subunit)?

g. How do membrane disrupting toxins affect the host cell membrane?

h. Describe superantigens and their effect on the body (in particular the immune system).

3. Virulence Factors: Endotoxin

a. What are endotoxins?

b. How or when are endotoxins released from the bacterial cell?

c. What intercellular signal is released by macrophages following their ingestion of bacteria?

d. By what mechanism do endotoxins cause fever?

e. How does the presence of endotoxin lead to shock (dangerous drop in blood pressure)?

4. Virulence Factors: Penetrating Host Tissues

a. What is the enzyme name for the “spreading factor”streptococcal species and Clostridium perfringensuse toinvade host tissues?

b. What enzyme is used by some streptococci and C. perfringens to digest collagen?

c. What is streptokinase? How does this toxin work? What is another name for streptokinase?

d. How is streptokinase and/or staphylokinase activity advantageous to the pathogens that produce them?

5. Virulence Factors: Hiding From Host Defenses

a. How do macrophages, B cells, and T cells detect the presence of foreign cells?

b. How does the composition of the bacterial capsule enable it to evade detection by immune cells such as macrophages?

c. How does Mycobacterium tuberculosis survive being ingested by macrophages?

d. By what mechanism are Shigella and Listeria able to survive in macrophages following phagocytosis?

e. By what mechanism does Leishmania and Legionella survive within the phagolysosome (fused phagosome and lysosome)?

f. What pathogens employ antigenic variation to avoid detection by the immune system?

6. Virulence Factors: Inactivating Host Defenses

a. What are peptidases?

b. What bacterium is capable of producing a molecule that mimics complement, therefore preventing thiscascade of immunological activity from occurring?

c. What are leukocidins? What species produce leukocidins?

d. How do IgA proteases aid the species that produce them? Name one species that produces this enzyme.

e. Describe one method by which HIV suppresses the activity of the immune system.

f. What is the general definition of a superantigen?

7. Virulence Factors: Enteric Pathogens

a. Name two examples of enteric pathogens.

b. By what methods is Salmonella able to inhibit phagocytosis?

c. What does Salmonella inject into host cells that causes actin rearrangement and membrane ruffling? What is the result of this activity?

d. How does the entry of Salmonella into host cells result in diarrhea?

e. What type of cells must Shigella attach to for entry?

f. How does Shigella direct its entry into the host cell?

g. What is one other example of a mechanism used by Shigella to spread to neighboring cells?