Viruses as causes of disease

Question 1

What is a virus?

Answer 1

An infectious, obligate intracellular parasite comprising genetic material (DNA or RNA) surrounded by a protein coat and/or a membrane

Question 2

Viruses don’t have…

Answer 2

Cell wall, organelles, both DNA and RNA

Question 3

Different shapes of viruses

Answer 3

Helical, icosahedral, complex

Question 4

Give examples of non-enveloped viruses

Answer 4

Adenovirus, parvovirus

Question 5

Give example of enveloped viruses

Answer 5

influenza, HIV

Question 6

A virus envelope is the lipid coat derived from p____ m______of the host cell

Answer 6

plasma membrane

Question 7

How do viruses replicate:
1) A______ to specific receptor

Answer 7

Attachment

Question 8

What are viruses called outside a living cell?

Answer 8

Virion

Question 9

How do viruses replicate?
2) Cell entry (u____ of virion within cell)

Answer 9

uncoating (only central core carrying nucleic acid and some associated proteins enter host cell)

Question 10

How do viruses replicate?
3) Host cell interaction and replication

Answer 10

Migration of genome to cell nucleus
Transcription to mRNA using host materials

Question 11

How do viruses replicate?
4) A____ of virion

Answer 11

Assembly (location of assembly changes depending on type of virus)

Question 12

How do viruses replicate?
5) R____ of new virus particles

Answer 12

Release
Can burst cell and cause cell death
or
Can be budding / exocytosis

Question 13

HIV i_____ its own viral DNA into the host cell’s DNA

Answer 13

integrates

Question 14

How do viruses cause disease?

Answer 14

Direct destruction of host cells

Modification of host cell

“Over-reactivity” of immune system

Damage through cell proliferation

Evasion of host defences

Question 15

Give an example of a virus which directly destroys its host cell?

Answer 15

Poliovirus - lysis of neurons leading to paralysis

Question 16

Give an example of a virus which modifies the host cell

Answer 16

Rotavirus - atrophies villi and flattens epithelial cells causing reduction in surface area of small intestine, nutrients including sugar not absorbed leading to diarrhoea

Question 17

Give an example of a virus which causes over-reactivity of immune system

Answer 17

Hepatitis B
Infects hepatocytes which presents viral antigen. Body responds by killing whole cell. Gives symptoms of liver damage (jaundice, pale stool, fever, itching)

Question 18

Give an example of a virus which damages through cell proliferation

Answer 18

HPV, Viral DNA integrated into host DNA, virus interacts with tumour suppressors leading to cervical cancer

Question 19

Give an example of a virus which evades host defences

Answer 19

Herpes viruses demonstrate latency, lie dormant in cells eg nerve root ganglions, lymphoid cells, myeloid cells

Question 20

Varicella Zoster Virus causes

Answer 20

chickenpox.

Question 21

Reactivation of Varizella Zoster Virus from dorsal root ganglion causes

Answer 21

Shingles

Question 22

Evasion of host defences can be at a molecular level due to a______ variablity

Answer 22

antigenic