Effects of Viruses on Host Cells

Question 1

What type of effects can viruses have on host cells?

Answer 1

Cytocidal (lysis/apoptosis)

Non-Cytocidal (persistent infection)

Cell Transformation (tumor cells)

Question 2

Visible damage or morphological changes to host cells during virus invasion:

Answer 2

Cytopathic effect

Question 3

What is it called when four or more cells fuse to create one large cell with 4 or more nuclei?

Answer 3

Syncytium

Question 4

An abnormal structure in a cell that has characteristic staining properties and is associated with certain viral infections:

Answer 4

Inclusion bodies

Question 5

Inclusion bodies can be:

Answer 5

Accumulation of viral components
Degenerative changes in the cell
Crystalline aggregates of virions

Question 6

T/F: inclusion bodies can be intracytoplasmic or intranuclear, can be large or small, single or multiple, round or irregular, and can be eosinophilic or basophilic.

Answer 6

TRUE, they can be all those things

Question 7

Eosinophilic bodies stain _____ and basophilic bodies stain _____.

Answer 7

pink, blue

Question 8

In what ways to viruses cause cell injury and death?

Answer 8

Inhibition of host cell NA synthesis

Inhibition of host cell RNA transcription (mRNA production and processing)

Inhibition of host cell protein synthesis

Causing lysosomes to release hydrolytic enzymes, destroying the cell.

Interference with cellular membrane function

Apoptosis

Question 9

During apoptosis, who is responsible for degradation of the cell’s own DNA and proteins?

Answer 9

caspases

Question 10

Which apoptotic pathway is activated as a result of increased mitochondrial membrane permeability following cell injury?

Answer 10

Intrinsic (mitochondrial) pathway

Question 11

Which apoptotic pathway is activated by engagement of specific membrane receptors, such as FAS, from the TNF receptor family, when the cytokine TNF binds?

Answer 11

Extrinsic (death receptor) pathway

Question 12

Which cells are able to initiate apoptosis of infected cells using mediators like perforin and granzyme?

Answer 12

Cytotoxic T cells and NK cells

Question 13

T/F: Antibodies contribute to cell mediated cytotoxicity?

Answer 13

TRUE - Ab binds Ag on target cell and recruits NK cells to kill the cell. (Ab-dependent cytotoxicity)

Question 14

Tumor suppressor genes are responsible for keeping the cell cycle in check. What are 2 examples of important tumor suppressor genes?

Answer 14

Rb and p53

Question 15

E2F is a proto-oncogene that facilitates cell division. If Rb is a tumor suppressor gene, what effect does Rb have on E2F?

Answer 15

Blocks it and keeps cell division in check.

Question 16

Which tumor suppressor gene prevents damaged DNA from entering the cell cycle, and when the damage can’t be repaired, marks the cell for apoptosis?

Answer 16

p53

Question 17

What kind of genome do oncogenic viruses usually have?

Answer 17

DNA

Question 18

T/F: Oncogenic viruses cause cancer when they infect a PERMISSIVE cell.

Answer 18

FALSE - oncogenic viruses cause cancer when they infect a NON PERMISSIVE cell because they can’t replicate, and the viral DNA integrates into the host DNA, causing cancer.

Question 19

What happens when an oncogenic virus infects a permissive cell?

Answer 19

The virus is able to complete its replication cycle, lyses the cell, and doesn’t cause cancer.

Question 20

What type of viruses steal proto-oncogenes from the host cell DNA and convert them into oncogenes?

Answer 20

Acutely transforming retroviruses

Question 21

What type of viruses insert their genome into the regulatory gene of the host cell DNA, rendering it unable to control the proto-oncogene, and leading to uncontrolled cell division (cancer)?

Answer 21

Slow/chronic transforming retroviruses

Question 22

Why are there sometimes immune responses to tumor cells?

Answer 22

New antigens appear on the surface of tumor cells.

*Most times they are not properly presented to immune cells.

Question 23

Give one example of a tumor antigen

Answer 23

FOCMA (feline oncornavirus membrane-associated antigen)