Lecture 6 - Identifying Host Factors

Question 1

How is virulence considered?

Answer 1

In the context of the host

As a relative term

Question 2

How can host determinants be found?
1)
2)
3)
4)

Answer 2

1) Introduce immune or susceptible antibodies or cells into host animal
2) Deplete host factors with antibodies
3) Deplete host factors using knockout mice
4) Deplete host factors with a transgene

Question 3

How to identify a host determinant
1)
2)
3)

Answer 3

1) Alter a mouse in a certain way (factor depletion using antibodies, etc)
2) Infect altered mouse, normal mouse with pathogen
3) Observe LD50, ID50, bacterial growth, pathology, transmission, etc

Question 4

What is iNTS?

Answer 4

Invasive non-typhoidal salmonellosis

Question 5

Evolution of invasive non-typhoidal salmonellosis
1)
2)

Answer 5

1) Salmonella enterica var. typhimurium was the leading cause of bacterimia in HIV+ patients in Malawi
2) Moved from infecting HIV+ to HIV- individuals

Question 6

Causative agent of invasive non-typhoidal salmonellosis

Answer 6

Salmonella enterica var. typhimurium

Question 7

Deficiencies predisposing to more severe salmonella infections

Answer 7

Deficiencies in IL-12, CD4

Question 8

Invasive non-typhoidal salmonellosis mortality rate in children

Answer 8

45%

Question 9

Difficulties in making a vaccine against Salmonella enterica var typhimurium (or treatment)
1)
2)
3)

Answer 9

1) Intracellular bacteria (vaccine immunity is normally antibody-mediated)
2) CD4+ T cells needed for a robust immune response - many patients are HIV+, therefore have little to no CD4+ T cells
3) Difficult to get antimicrobials into host cells

Question 10

Cytokine that can control S typhimurium infection

Answer 10

IFNg

Question 11

Issues with iNTS murine model

Answer 11

Lethal infection in mice within two to three days. Human infection lasts several weeks

Question 12

Type of mice used in iNTS murine model

Answer 12

C57B6 mice

Question 13

Solution to poor iNTS murine model

Answer 13

Use an attenuated strain of S. typhimurium that is less virulent in mice.
New strain controlled by mice within around 2 weeks

Question 14

S. typhimurium experiment to determine controlling immune response
1)
2)
3)

Answer 14

1) Gather C57B6 mice with various immune deficiencies
2) Innoculate with a set amount of S typhimurium
3) Observe different courses of disease

Question 15

Immunodeficiencies of C57B6 mice used in S typhimurium experiment
1)
2)
3)
4)

Answer 15

1) Deficient in IFNg, lymphocytes (RAG2 deficient). Very susceptible
2) Deficient in CD4+, CD8+ T cells. Susceptible (died)
3) Deficient in CD4+ T cells (chronic infection)
4) Mice lacking B cells, CD8+ T cells, MHC I, CD1. Course of disease is same as wild type mice

Question 16

Information from S typhimurium study in mice
1)
2)
3)

Answer 16

1) No control in mice lacking IFNg and lymphocytes
2) Chronic infection in mice lacking CD4+ T cells (mimics HIV)
3) Exacerbated chronic infection in mice lacking both CD4+ and CD8+ T cells

Question 17

Which enzyme degrades DNA to siRNA?

Answer 17

DICER

Question 18

What is 2-dimensional gel electrophoresis?

Answer 18

Proteins are separated by weight along the Y-axis, and separated by charge along the X-axis

Question 19

How can siRNA be used to find host determinants?

Answer 19

Made complementary to gene of interest, inserted into host cells to observe effect of suppressing gene of interest

Question 20

What are genome-wide association studies?

Answer 20

1) Take genomes from a group of people - uninfected, infected, severely infected
2) Compare genomes to see if any genes, SNPs, correlate with disease severity