mechanisms of viral infection and pathogenesis

Question 1

what affects host susceptibility to disease

Answer 1

• lifestyle, age, other medical conditions

Question 2

why may some viruses undergo reactivation

Answer 2

can be latent after primary infection e.g. when immunocompromised may reactivated

Question 3

what is secondary infection

Answer 3

infection with a second different organism after/whilst being infected with another organism e.g. opportunistic infections after HIV

Question 4

what is reinfection

Answer 4

infection with the same organism following recovery of an infection with the same organism

Question 5

how may viruses enter the body

Answer 5

resp tract, face-oral route, blood, body fluids, skin cuts, sexually, animal bites, insect bites

Question 6

examples of viruses causing acute disease

Answer 6

rabies, rhinovirus, influenza, rotavirus

Question 7

what determines the pathogenicity of a virus

Answer 7

site of entry, tissue tropism, extent of cell damage caused ability of immune system ti clear disease

Question 8

what is vertical transmission

Answer 8

transmission from mother to baby immediately before/after birth. significant bc baby is unable to mount an immune response,

Question 9

what is immune evasion

Answer 9

a strategy used by pathogenic organisms and tumours to evade a host’s immune response to maximize their probability of being transmitted to a fresh host or to continue growing, respectively.

Question 10

how may a virus evade the immune system

Answer 10

• evades when invading a nonoptimum immune system
• establishing latency (stops replicating and only makes v few viral proteins)
• CMV down regulates MHC2 .’. cannot present to CD+
• HIV/CMV replicate in privileged sites .’. hard for immune system to target it
• viruses change viral proteins regularly

Question 11

what is papilloma virus

Answer 11

non-enveloped dsDNA. group of viruses that affect your skin and the moist membranes lining your body. can be classified into high and low risk groups

Question 12

what are the high risk HPV (human papilloma virus)

Answer 12

HPV 16,18,31,45

these strains linked to development of cervical carcinomas and other malignancies

Question 13

what does HPV infect

Answer 13

epithelial cells. requires actively dividing cells in order to replicate .’. infects basal layers of epithelium

Question 14

what happens when HPV infects basal cells of epithelium

Answer 14

migrates to cell nuclei and starts to copy own viral DNA. DNA genome not yet integrated into host, exists as plasmid. genes E6/E7 cause host to become transformed once they are integrated

Question 15

role of E6 of HPV

Answer 15

interferes with P53. P53 is a antioncogene that causes apoptosis if DNA is damaged or cell is infected by virus

Question 16

role of EP6 of HPV

Answer 16

interferes with retinoblastoma which is a regulator of cell cycle. E7 binds to Rb .’. cell cycle becomes unregulated
also activates telomerase .’. keeps telomeres of cancerous cells intact

Question 17

role of E6/7 when HPV plasmid is unintegrated into host genome

Answer 17

viral gene E2 turns down expression so are not expressed .’. no effect

Question 18

how does HPV plasmid become integrated into host genome

Answer 18

Virus cuts plasmid in middle of E2. split DNA is now linear and integrates into host DNA. E2 gene is split .’. nonfunctioning .’. free exression of E6/7