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WEEK 12 SEM 4 > Mechanisms of viral infections and pathogenesis > Flashcards

Mechanisms of viral infections and pathogenesis Flashcards

1
Q

What is kaposi’s sarcoma?

A

cancer caused by herpes simplex virus 8

- occurs in immunocompormised people e.g. with HIV

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2
Q

If you have multiple sexual partners, what are you likely to get?

A
  • papillomavirus

- causes genital warts and cervical cancer

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3
Q

How can you get EBV?

A
  • causes glandular fever
  • kissing
  • bodily fluids
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4
Q

What is a primary infection?

A
  • it can enter and replicate at site of entry and remain there e.g. influenza virus and rhino virus
  • the virus can replicate at the entry site and then spread e.g. varicella zoster
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5
Q

Where doest varicella zoster virus start and spread to?

A
  • start in respiratory tract
    (asymptomatic here)
  • spread to skin
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6
Q

What is reactivation?

A
  • stay latent in body cells and reactivate later in time
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7
Q

Give examples of viruses that can reactivate in the body?

A
  • herpes simplex virus
  • varicella zoster
    they hide in neurons
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8
Q

What is secondary infection?

A
  • second different organism after having/while being infected by a previous organism
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9
Q

What is a good example of a secondary infection?

A
  • someone has bacterial infection
  • give antirbiotics
  • gets rid of commensal organisms
  • so less competition for other organisms to grow
  • can get candida albicans (vaginal thrush)
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10
Q

What is a bad reason why secondary infection can go?

A
  • when there is compromised immunity
  • e.g. HIV where we see increased bacterial and fungal infections
  • e.g. getting bacterial pneumonia after viral respiratory tract infections
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11
Q

What is reinfection?

A
  • same organism infects again
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12
Q

Which organisms reinfect?

A
  • influenza

- rhinovirus (common cold)

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13
Q

Which viruses enter through the respiratory tract?

A
  • influenza virus
  • rhinovirus
  • varicella Zoster
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14
Q

Which viruses enter through the faecal-oral route?

A
  • noravirus

- rotavirus

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15
Q

Which viruses enter the blood?

A
  • HIV
  • HepA
  • HepC
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16
Q

Which viruses enter through skin cuts?

A
  • papilloma virus

- molluscum contagiosum

17
Q

Which viruses are passed on through sexual transmission?

A
  • papilloma virus
  • HIV
  • HSV
18
Q

Which viruses are passed on through animal bites?

A
  • rabies
19
Q

Which viruses are passed through insect bites?

A
  • hemorrhagic fever

- lassafever (Arenaviridae)

20
Q

Which viruses cause acute diseases?

A
  • influenza
  • rhinovirus
  • rotavirus
  • rabies
21
Q

Which viruses cause chronic disease (lasting more than 3 months)?

A
  • HepB

- HepC

22
Q

What decides how pathogenic a virus is?

A
  • nature of virus
  • site of entry
  • tissue tropism
  • what tissue does it affect?
  • extent of cell damage caused
  • ability of the immune system to clear the virus
23
Q

What are examples of vertically transmitted viruses?

A
  • rubella

- parvovirus

24
Q

In a perinatal infection, how is the immune system evaded?

A
  • a huge viral load of herpes simplex virus can be passed from mother to child
  • the load is so much that baby struggles to clear it
25
Q

How does HSV evade the immune system?

A
  • stays latent in nerve ganglia

- immune system cant reach here bc doesnt know where the virus is

26
Q

How does CMV evade the immune system?

A
  • downregulate MHC1- so infected cells cant present to CD8+

- hide in privileged sites e.g. CD4 T helper cells

27
Q

How do HIV and CMV evade the immune system?

A
  • hide in privileged sites e.g. CD4 T helper cells

- hard for immune system to get the virus

28
Q

How does influenza evade the immune system?

A
  • change antigens constantly
  • so immune system doesnt recognise it when it infects again
  • so each time it takes the immune system time to react
29
Q

How does HepB evade the immune system?

A
  • releases incomplete surface proteins
  • they form an incomplete virus
  • they decoy proteins and divert immune response away from complete virus
30
Q

What is human papillomavirus?

A
  • non enveloped
  • double stranded DNA virus
  • over 100 types
  • put into high risk and low risk
31
Q

What are the high risk human papillomaviruses?

A
  • HPV 16, 18, 31 and 45

- development of cervical carcinoma and other malignancies

32
Q

What does HPV attack?

A
  • epithelial cells and these epithelial surfaces have different cellular layers
  • epithelial surface has many layers
  • only cells in basal layer actively divide
  • virus needs to infect here
  • they attack and migrate to cell nucleus
  • now copies its own DNA
33
Q

What genes does the HPV have?

A

E2, E6, and E7

34
Q

What does E6 do?

A
  • E6 gene interferes with TP53 (coded by the p53 gene) (a tumor suppressor gene)
  • TP53 PROTEIN normally causes apoptosis if the cell’s DNA is damaged or if the cell is infected by a virus
  • activates telomerase gene (keeps cancerous cell intact)
35
Q

What does E7 do?

A
  • interferes with retinoblastoma which is a tumor suppressing protein in the host cell
  • retinoblastoma normally helps regulate the cell cycle
  • E7 binds to this protein and stops it from functioning, and the cell cycle becomes unregulated
36
Q

What does E2 do?

A
  • downregulates E6 and E7 expression
  • when the viral plasmid is unintegrated into host DNA, E2 turns down the cancer causing genes so they are not expressed and do not have an effect
  • BUT when HPV integrates its DNA into the host genome
  • the virus makes a cut in the DNA plasmid in the middle of E2
  • the circular viral DNA is not linear, and it integrates into the host DNA-now an upstream regulatory region recruits transcription factors and E6 and E7 are produced
37
Q

Tell me about Zika virus:

A
  • flaviviridae family
  • enveloped
  • ssRNA
  • positive sense
  • Transmission: via mosquitos
  • causes microcephaly in infants when pregnant women get zika

WEEK 12 SEM 4 (5 decks)

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