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Undeleted > Virology > Flashcards

Virology Flashcards

1
Q

def. of virus

A

broad general term for any aspect of the infectious agent which includes: infectious or inactivated particle, viral nucleaic acid and protein in infected cell

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2
Q

def. of virion

A

complete intact virus particle outside of the cell

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3
Q

def. viroid

A

short stretch of circular single stranded RNA without a protein coat

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4
Q

what can virus be seen with

A

electron microscope

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5
Q

what is virus structre

A

core of nucleic acid surrounded by protein coat +/- evelope

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6
Q

3 different options for nucleic acids in viruses

A
  1. DNA or RNA
  2. single or double stranded
  3. linear/circular
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7
Q

what proteins are in viruses

A
  1. structural - capsid made of capsomeres

2. enzymes - few, differ from host cell

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8
Q

what is significance of virus enzymes

A

target for drugs

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9
Q

what is envelope made from

A

cell as it pushes out

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10
Q

5 different morphologies of virus

A
  1. helical/tubular - +/- envelope
  2. icosahedral - +/- envelope
  3. complex
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11
Q

what is enveloped cubic virus for sure

A

herpesviridae

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12
Q

4 ways to class viruses

A
  1. type and stucture of viral nucleic acid
  2. strategy used in replication - site
  3. type of symmetry of virus capsule
  4. presence of envelope
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13
Q

what are virus families

A

similar structural, genomic and replication properties (suffix viridae)

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14
Q

what are virus genera

A

subdivisions of families (suffix: virus)

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15
Q

what are genera subtypes based on

A

nucleotide sequences and antigen reactivities

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16
Q

6 DNA viruses - rest are RNA

A
  1. Hep B
  2. HPV
  3. parvovirus
  4. herpes
  5. adenovirus
  6. polyoma viruses
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17
Q

viral replications steps (7)

A
  1. adsorption (attachment)
  2. entry
  3. uncoating
  4. transcription
  5. synthesis
  6. assembly
  7. release
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18
Q

how do viruses attach

A
  • random collision
  • interaction between specific proteins on virus and on surface of cell
  • able to only infect a limited range of cells
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19
Q

2 mechs. of virus entry

A
  1. endocytosis

2. fusion of envelope with cell

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20
Q

how do virus uncoat

A

cell enzymes strip capsid - no longer visible

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21
Q

2 things that must be synthesized

A
  1. proteins (structural and enzymes)

2. nucleic acids - new virus genome

22
Q

where do DNA virus do their replications

A
  • DNA in nucleus
  • protein in cytoplasm
  • move proteins into nucleus for packaging
23
Q

2 types of RNA viruses and how they replicate

A

+sense - actas a mRNA and can make proteins immediatelly

-sense - must first make a +sense using viral enzymes and then copy

24
Q

how do retroviruses work

A

contain reverse transcriptase

  • +sense RNA > cDNA > integrated directly into the host chromosome
  • virus doens’t need to do any work
25
Q

2 ways of release

A
  1. bud out

2. rupture cell

26
Q

2 ways virus may cause damage

A
  1. directly

2. through host reactions to the virus

27
Q

2 factors that affect the outcome of viral infections

A
  1. host’s defences

2. virulence factors

28
Q

4 possible outcomes of a virus-host cell interaction

A
  1. cell death - lytic
  2. cell transformation - cancer or malignancy
  3. latent infection - may reactivate any time to cause disease, may have continuous or intermittent shedding
  4. cell fusion to form nucleated cells - HIV
29
Q

5 possible ways viruses evade the immune system

A
  1. antigenic variation - keep switching
  2. encode receptors for inflammatory cytokines - shutting down imune system
  3. reduce expression of MHC-class 1 - reducing ability of T cells to kill
  4. direct cell to cell propagation
  5. attenuation
30
Q

3 types of persistent viral infections (some overlap)

A
  1. chronic carrier - chronic illness due to continuous shedding
  2. latent infection - may pop back up and may shed
  3. slow virus infections - due to prolonged incubation periods
31
Q

2 routes of viral transmission

A
  1. horizontal - person to person

2. vertical - mother to fetus

32
Q

when can transmission occur

A
  1. with or without disease
  2. during asymptomatic shedding
  3. during incubation period
33
Q

what are some epidemiological aspects that change viral outcomes

A
  1. mode of tranmission
  2. age
  3. gender
  4. ethnicity
  5. travel Hx
  6. occupation
  7. season
  8. medical conditions
34
Q

what is incubation time

A

time from infection to dev. of Sx

35
Q

2 short incubation virus (1-2 days)

A

GI and resp viruses

36
Q

3 medium incubation viruses (1-3 weeks)

A
  1. MMR
  2. VZV, HSV
  3. enteroviruses, polio
37
Q

4 long incubation viruses (months)

A

heps, HIV, EBV, rabies

38
Q

some non-specific host defences

A
  • skin
  • rest tract, cilia, mucous
  • GI - acid, lymphoid
  • GU- flow
    tears
  • phago
  • interferons
39
Q

what does humoral do

A
  • Ig
  • neutralize viruses
  • elimination of viruses
40
Q

3 main Igs in virus infections

A

IgM - early - 1week to 6 months
IgG - months to years, responsible for immunity
IgA - dimer of 2 Igs, body secretions, mainly for GI

41
Q

what does cellular defense do

A
  • elim of virus infected cells

- most important defence

42
Q

6 cell mediated types and functions

A

Th - stim cytotoxic response and activate B cells
Ts - control and reg. response by supressing Th
Tc - cytotoxic - min cells to kill virus infected cells
Td - delayed hypersentitivity cell - release macrophage activating factor
NK - direct killing of infected cells
interleukins - modulate immune response

43
Q

5 times rapid and accurate diagnosis is important

A
  1. tranplant
  2. HIV
  3. effective chemo
  4. epidemiology
  5. transplant safety
44
Q

3 methods to diagnose viruses

A
  1. isolation (culture)
  2. direct detection
  3. serology (AB/antigen)
45
Q

3 methods of culture

A
  1. tissue culture
  2. chick embryo
  3. animal innoculation
46
Q

how must viruses be samples

A

quickly and in a cool special medium

47
Q

2 adv. of cuture

A
  1. definitive

2. obtain isolate for further tests

48
Q

3 disadv. to culture

A
  1. not all viruses cultruable
  2. may take long time
  3. biohazard
49
Q

how is direct detections done (3)

A
  1. look at the sample with electron microscope
  2. look for monoclonal ABs against
  3. PCR for viral DNA/RNA
50
Q

what is serology tests

A

look for ABs against

51
Q

4 ways to diagnose in serology

A
  1. IgM ABs
  2. four fold rise in AB titre
  3. seroconversion
  4. very high single AB titre (unreliable)

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