Viral Pathogenesis

Question 1

what are main sites of viral entry?

Answer 1

• respiratory tract
• alimentary tract
• urinogenital tract
• conjunctiva (eyes)
• arthropod (insects)
• capillary
• skin

Question 2

what is an overt disease?

Answer 2

Apparent disease (what we see, symptoms), many viruses are unapparent

Question 3

what are acute virus infections?

Answer 3

• rapid onset of disease
• relatively brief period of symptoms
• resolution for infection happens within days
• localised to specific site of the body

Question 4

what does widespread infection of virus to tissues cause?

Answer 4

viraemia

Question 5

what are steps for infection for Influenza A virus?

Answer 5

• virus infects cell of respiratory tract
• destruction of respiratory epithelium occurs ( secondary bacterial infections)
• altered cytokine expression leading to fever (e.g. interleukin-1 and interferon)

Question 6

what is antigenic drift?

Answer 6

gradual evolution of viruses to generate antigenic variants

Question 7

what is antigenic shift?

Answer 7

significant changes in virus antigenic structure

Question 8

what hosts play a huge role in generating new virus types through antigenic shift?

Answer 8

non-human hosts

Question 9

what are 2 outcomes for a virus which enters the gut?

Answer 9

1. virus excretion in the faeces

2. viraemia; in non-neuronal tissue or neuronal tissue which can lead to paralysis

Question 10

what is a latent virus infection?

Answer 10

stays in tissues for the rest of your life but remains dormant until activated

Question 11

what are 2 types of common latent virus infections?

Answer 11

1. herpes simplex virus (cold sores type 1)

2. herpes simplex virus (genital lesion type 2)

Question 12

what 3 types of stimuli can reactivate a latent virus?

Answer 12

1. chemical signal
2. mechanical signal
3. light signal

Question 13

what are some factors which suppress an immune system?

Answer 13

-stress
-drugs
-bacterial illness
-steroids
(all lower immune resistance)

Question 14

where does virus lie dormant?

Answer 14

in the cell nucleus (but no replication occurs)

Question 15

when does viral replication occur?

Answer 15

when virus migrates to epithelial cells (primary infection)

Question 16

what cancer can HPV lead to?

Answer 16

cervical carcinoma

Question 17

what cancer can retrovirus lead to?

Answer 17

lymphomas and leukaemias

Question 18

How is the virus HTLV-1 transmitted? (responsible for tumour formations

Answer 18

transmission by blood; mother to child

Question 19

what does HTLV-1 virus do?

Answer 19

• infects T cells
• modifies host cell gene expression using a transactivating protein (tax)
• can lead to variety of disease including leukaemia

Question 20

how does a retrovirus induce tumour formation? (4)

Answer 20

1. virus infects cell
2. virus nucleic acid made as viral DNA integrates into cellular genome
3. virus causes changes in cellular gene expression
4. uncontrolled cell multiplication and tumour formation

Question 21

which cells does HIV kill in the body?

Answer 21

CD4 (Helper T cells)