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102 Theme 4 > Lecture 4: Viruses > Flashcards

Lecture 4: Viruses Flashcards

1
Q

How big is a virus

A

20-300nm

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2
Q

What shapes can a virus be

A

Icosahedral or helical

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3
Q

What are some features of viruses

A

Capsid
- protein coat that encloses genome and core proteins
Some have an envelope
- lipid bilayer that surrounds the capsid
- has glycoproteins that form projections
Can contain either DNA or RNA
- positive or negative polarity
- single molecule or fragmented

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4
Q

Ways of transmitting viral infections

A 
Horizontal 
- airborne 
- fecal-oral
- sexual 
- vector borne
- blood
Vertical 
- in utero through placenta during pregnancy
- intra partum at childbirth
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5
Q

sizes of droplets and aerosols

A

droplets are >2μm

aerosols are <2μm

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6
Q

viruses that do airborne transmission

A
  • common cold (rhinovirus)
  • influenza (orthomyxoviridae)
  • measles and mumps (paramyxoviridae)
  • rubella (logaviridae)
  • chickenpox (herpesviridae)
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7
Q

virus that travels through fecal-oral route

A

hepatitis A and E

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8
Q

which family of viruses travel through vector-borne transmission

A

arboviruses

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9
Q

viruses that travel through blood contamination

A

HIV, hepatitis B and C

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10
Q

viruses that travel through vertical transmission

A
  • HIV, hepatitis B and C

- citomegalovirus, zika virus, rubella

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11
Q

outline viral replication

A

1) interaction between viral glycoproteins and cell receptors
2) penetration of the virus into the host cell
3) enzymatic removal of the protein coat and liberation of the viral nucleic acid and core proteins into cytoplasm of the host cell
4) production of viral mRNA and host cell ribosomes synthesise the viral proteins
5) morphogenesis and maturation of the new viruses
6) release of virus, either through lysing or budding

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12
Q

how is the viral mRNA synthesised

A

DNA viruses
- uses host’s DNA dependent RNA polymerase
negatively charged RNA viruses
- need viral RNA-dependent RNA polymerase
positively charged RNA viruses
- used directly as RNA template

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13
Q

cytopathic effects of viral replication

A
  • inhibits cell transcription and translation
  • changes membrane permeability
  • alters cytoskeleton or trafficking pathways
  • cell to cell fusion
  • induces apoptosis
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14
Q

how can viruses spread from their initial site of replication

A
  • haematogenous
  • lymphatic
  • neural
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15
Q

what is a tropism and what does it depend on

A

the ability of different viruses to infect different cell types
depends on:
- specific receptors on the host cell
- specific host enzymes for viral maturation
- temperature and pH

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16
Q

example of disease caused by direct cytopathic effect

A

West Nile virus affects neurons, induces apoptosis, causes encephalitis and movement disorders

17
Q

example of disease caused by antibody-mediated immunity

A

dengue fever causes a massive release of cytokines after reinfection from a different serotype (strain). Causes vascular leakage and hemorrhage

18
Q

example of disease caused by virus-induced tumorigenesis

A
  • HPV causes cervical cancer

- hepatitis B and C cause hepatocellular carcinoma of the liver

19
Q

ways to diagnose a viral infection

A
  • microscopy
  • particle agglutination test (virus coated with viral antibodies)
  • immunofluorescence technique (IFT)
  • serology (use of antibodies to detect viral antigen)
  • quantitative PCR (qPCR) and reverse transcription PCR (RT-PCR)
  • ELISA
  • haemagglutination test
  • complement fixation test
20
Q

what is latency

A
  • period when the productive replication cycle is silent, but can reinitiate
  • common with herpesviridae viruses
21
Q

antiviral treatment for SAR-CoV-2

A

remdesivir which inhibits RNA dependent RNA polymerase

22
Q

how can antiretrovirals work

A
  • attachment inhibitors
  • fusion inhibitors
  • integrase inhibitors
  • protease inhibitors
  • nucleoside and non-nucleoside reverse transcriptase inhibitors
23
Q

prevention of HIV

A
  • pre-exposure prophylaxis (PrEP)
  • post exposure prophylaxis after sexual exposure (PEPSE)
  • condoms and male circumcision

102 Theme 4 (11 decks)

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