Unit 11

Question 1

Give several examples of viral virulence factors.

Answer 1

Attachment proteins and unique enzymes needed by the virus.

Question 2

What is an attenuated virus?

Answer 2

A virus that has lost a virulence factor.

Question 3

What is viremia?

Answer 3

Viremia is characterized by viruses in blood and may allow the virus to spread to a secondary site if the cells allow it.

Question 4

What is the significance of the immune response in fighting a viral infection?

Answer 4

Viruses are intracellular parasites, so you must kill your own cells. Cytokines (interferon), immune complexes and complement can cause damage.

Question 5

What are the 4 potential outcomes of a viral infection of a cell?

Answer 5

Failed infection (abortive infection), cell death (lytic infection), replication without cell death (persistent infection) and presence of a virus without production but with potential for reactivation (latent-recurrent infection).

Question 6

What is viral incubation period and how is this measured?

Answer 6

Incubation period refers to the time between exposure and symptoms. For must viruses it is measured in days to years.

Question 7

Describe the significance and clinical manifestations of a latent infection? Chronic persistent infection?

Answer 7

A latent infection has viral genome present, but shed virus is not detectable. Chronic persistent infection has low detectable amounts of virus present.

Question 8

How are viruses transmitted?

Answer 8

Inhalation and oral mucosa. Fecal oral via naked nucleocapsids. Blood. Syncytium.

Question 9

What is syncytium?

Answer 9

Allows cell to cell transfer with out being exposed to the immune system.

Question 10

Describe the link between viruses and cancer.

Answer 10

Some viruses are oncogenic. They provide or activate growth stimulating genes, oncogenes. They remove STOPS for DNA synthesis and growth. They prevent apoptosis. They integrate into the host and turn on neighboring genes. And they cause cells to divide faster and get more mutations.

Question 11

How are viruses grown?

Answer 11

Viruses must be grown in tissue culture in cells or in live animals.

Question 12

How are viruses grown?

Answer 12

Viruses must be grown in tissue culture in cells or in live animals.

Question 13

Give several examples of CPE or cytopathic effect of the virus.

Answer 13

CMV-Large cells. Inclusion bodies-Negri bodies-rabies in the brain. HSV, Varicella Zoster-Cowdry bodies in single or fused cells.

Question 14

How are viruses diagnosed?

Answer 14

Serology, detection of viral components, symptoms, history, season, isolate and grow the virus on cells, identify virus with electron microscope.

Question 15

How are viruses diagnosed?

Answer 15

Serology, detection of viral components, symptoms, history, season, isolate and grow the virus on cells, identify virus with electron microscope.

Question 16

How do antiviral agents disrupt the virion?

Answer 16

Enveloped viruses are susceptible to lipid and detergents. It stops the infection.

Question 17

How do antiviral agents block attachment?

Answer 17

Antibodies and passive immunization. Usually in the form of receptor antagonists. Ex: CCR5 to block infection by HIV.

Question 18

How do antiviral agents block penetration and uncoating.

Answer 18

Amantadine and rimantadine neutralize pH in vesicle that normaly causes uncoating. Used for Influenza A.

Fuzeon blocks HIV syncytium formation, which thus blocks penetration and uncoating.

Question 19

How do antiviral agents block RNA synthesis and transcription?

Answer 19

Tough because we need mRNA too.

Question 20

How do antiviral agents block genome replication?

Answer 20

Nucleoside analogues.

Question 21

How do antiviral agents protein synthesis?

Answer 21

This is a poor target because viruses use HOST ribosomes and these inhibitors aren’t specific.

Question 22

How do antiviral agents protein synthesis?

Answer 22

This is a poor target because viruses use HOST ribosomes and these inhibitors aren’t specific.

Question 23

How do antiviral agents block virion assembly and release?

Answer 23

HIV protease is required to cut up long protein chains.

Relenza and tamiflu are enzyme inhibitors for Influenza.

Question 24

How do antiviral agents stimulate host immune response?

Answer 24

Innate I/S. Specific immune system through passive antibodies. Vaccination.