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PRIS > Viruses 2 - replication > Flashcards

Viruses 2 - replication Flashcards

reminder - viruses 3 in on paper cards

1
Q

What type of mutations do RNA viruses have?

A
  • more unstable mutations
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2
Q

What happens if a virus is more virulent?

A
  • control is more difficult
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3
Q

What is the control of non-enveloped viruses like?

A
  • more difficult to control and spread more easily
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4
Q

What do we use in diagnosis and vaccination?

A
  • use structural vs non-structural proteins
  • DIVA vaccine/test
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5
Q

What is antigenic drift?

A
  • small changes eventually lead to changes in surface proteins (HA and NA)
  • happening all the time as the virus replicated such as point mutations
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6
Q

What is antigenic shift?

A
  • abrupt major changes to those surface antigens (HA/NA) - like a host species jump
  • can occur if your genome is segmented
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7
Q

The first stage of viral replication is attachment and entry.
what are the different ways this can happen?

A
  • penetration (injection of genome) = non-enveloped
  • Fusion = enveloped
  • Endocytosis = enveloped
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8
Q

How do viruses bind?

A
  • viruses bind to receptor in cell surface
  • glycoprotein on virus binds to protein/polysaccharide of receptor
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9
Q

What is haemagglutinin?

A
  • H-antigen
  • H1-18
  • essential for attachment
  • leads to variation in virulence based in tropism
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10
Q

What is neuraminidase?

A
  • N-antigen
  • N 1 -11
  • essential for escape
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11
Q

What is tropism?

A
  • the ability of specific virus to infect particular cell, based in virus-receptor interaction
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12
Q

What are the two types of pathogenesis?

A
  • highly pathogenic
  • lowly pathogenic
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13
Q

What does a change in tropism lead to?

A
  • change in pathogenesis, symptoms and virulence
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14
Q

What is endocytosis?

A
  • part of the cell machinery for moving large-sized materials into cell through engulfing
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15
Q

How can viruses exploit endocytosis and what different methods do they use?

A
  • to gain gain entry
  • they use different methods of endocytosis such as vesicles and pits
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16
Q

What might enveloped viruses do during endocytosis?

A
  • may fuse with endosomal membrane
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17
Q

What happens once a virus has entered a cell through endocytosis?

A
  • once inside there is a pH change which releases virus from endosome
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18
Q

What is the non-endocytic route of entry?

A
  • virus released directly into cytoplasm
  • enveloped viruses with fusion at cell surface
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19
Q

What is the non-endocytic penetration route?

A
  • non-enveloped virus attached to host cell and injects virus into cell
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20
Q

Where do DNA viruses replicate?

A
  • replication of genome in cytoplasm
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21
Q

Where do RNA viruses replicate?

A
  • replication of genome in nucleus
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22
Q

What is uncoating?

A
  • release of the viral genome from capsid so it can replicate inside host
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23
Q

How can viruses escape a cell?

A
  • pH change
  • fusion
  • viral envelope with endosomal membrane
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24
Q

What varies greatly in viruses?

A
  • extent of nucleoprotein complex and capsid disintegration
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25
Q

What must viruses do for replication?

A
  • must replicate its genome
  • produce proteins e.g., capsid, glycoproteins if enveloped
  • assemble genome and capsid (and envelope)
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26
Q

What is mRNA used for?

A
  • used for transcription (DNA > mRNA > ribosome > protein)
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27
Q

Viruses - different strategies depend on genome:

A
  • DNA v RNA
  • RNA > single or double-stranded
  • positive or negative sense RNA
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28
Q

What is positive RNA?

A
  • works as mRNA - can inject genome directly
29
Q

What is negative sense RNA?

A
  • must create template, like mRNA before its read
30
Q

DNA has 2 strands what are they?

A
  • positive/sense
  • negative/antisense
31
Q

RNA has 1 strand - what is it?

A
  • positive or negative sense
32
Q

What does RNA positive sense do?

A
  • injects genome into cell to make proteins
33
Q

What does RNA negative sense do?

A
  • must first produce positive stand to produce proteins
34
Q

DNA viruses mRNA transcription occurs where and what does it utilise?

A
  • in the nucleus
  • utilises cellular RNA polymerase
35
Q

Where does DNA viruses mRNA get transported?

A
  • transported to ribosomes in cytoplasm for translation
36
Q

What do RNA viruses use for transcription?

A
  • cells don’t possess enzyme for RNA transcription
  • therefore, they must use own enzyme
37
Q

Where do RNA viruses travel for transcription?

A
  • most remain in cell cytoplasm (no need to enter nucleus)
38
Q

What are ribosomes?

A
  • cellular organelles composed of RNA protein
  • site of protein synthesis
  • site of translation of viral mRNA (so are essential to replication)
39
Q

What are early proteins?

A
  • non-structural (enzymes etc.)
40
Q

What are late proteins?

A
  • structural (capsid and envelope)
41
Q

What is assembly/packing?

A
  • packaging of new genomes with viral proteins to form new virus particles
42
Q

What is reassortment?

A
  • segmented genome allows exchange of gene segments in coinfected cells
43
Q

What does reassortments still have the potential to do?

A
  • still has the potential to alter nature of infection
  • e.g., may affect resistance to pre-existing immunity
44
Q

What is viral mutation?

A
  • pulls multiple strains and combines into a new one which the host may not have immunity against
  • this is why flu jabs are repeated - new mutations/strains
45
Q

What happens during assembly and exit phase of viral replication?

A
  • re-assembly or viral components and egress from cell
46
Q

What are the different methods of viral release and what are each of these?

A
  • budding from plasma membrane (enveloped viruses acquire envelop)
  • exocytosis ( cell wall lets virus pass)
  • lysis (cell rupture - non enveloped)
47
Q

What is the structure of canine parvovirus and how does this aid spread?

A
  • a small non-enveloped virus, which means it can live in the environment and be difficult to destroy
48
Q

How does canine parvovirus virus exist a cell?

A
  • penetration and lysis
49
Q

What virulence does Canine parvovirus have and how does it damage the body?

A
  • high virulence
  • it damages the GI tract cells and slough off gut cells, can also damage spleen and bone cells
50
Q

Why do we culture viruses?

A
  • research
  • vaccine production
  • as tool - to express viral proteins
  • diagnostics
51
Q

We can culture viruses using living cells - what can these be?

A
  • animal host
  • fertilised chicken eggs
  • cell cultures
52
Q

When can we use animal hosts for culturing and why is there issues using these?

A
  • only where limited success with eggs or cell cultures
  • ethical clearance required
53
Q

What age do we use chicken eggs for culturing?

A
  • use at 8-11 days
54
Q

There are 4 main sites of inoculation in chicken eggs that can be used for different viruses what are these?

A
  • chorioallantoic membrane inoculation
  • amniotic inoculation
  • yolk sac inoculation
  • allantoic inoculation
55
Q

What is a must in cell culture?

A
  • must be appropriate for virus (tropism)
56
Q

Cell cultures are usually derived from what? and what is an advantage of this?

A
  • tissue samples such as lung, kidney, liver
  • ADVANTAGE - easy to manage and scale up
57
Q

What are the steps required for preparation of cell culture?

A
  1. collect sterile tissue sample and cut very small
  2. treat with proteolytic enzymes, obtain cells
  3. suspend in growth medium (contains amino acids, vitamins, salt, glucose, buffering solution, foetal calf serum, antibiotics)
  4. cells grow - cover flask, attach to slides
  5. treat with trypsin - remove cells - transfer to new flasks = passaging
  6. once cells growing well - can use for viral culture
58
Q

What are the two culture types?

A
  • primary cell cultures
  • continuous cell lines
59
Q

What are primary cell cultures?

A
  • from freshly prepared tissue sample
  • can survive approx. 15 passages (differentiation prevents further cell division)
60
Q

What are continuous cell lines?

A
  • immortalised cell - continue to grow
  • often derived from tumours
  • disadvantage - loss of cell receptors
61
Q

What are the steps involved in viral culture?

A
  • obtain clinical sample, swab, faeces, tissue
  • keep cold (ice) or freezing for long-term storage
  • inoculate in culture medium with antibiotics
  • look for cytopathic effects as a signs of viral infection
62
Q

What are cytopathic effects?
and
When looking for cytopathic effects what do you look for?

A
  • visible changes to host cells observed under light microscope
  • holes, cells round up and detach
  • syncytia, cells fuse, multi-nuclei
  • inclusion bodies (protein masses within cells)
63
Q

What are non-cytopathogenic viruses?

A
  • many viruses, no CPE or signs of replication but will get viral particles
  • will have to stain for virus protein - colour change
64
Q

What are infectivity assays used for?

A
  • to quantify number of infectious particles produced
65
Q

-What are plaque assays used for?

A
  • to quantify plaque forming units (pfu/ml)
66
Q

What do serial 10-fold dilutions use?

A

– use late dilutions to inoculate cell cultures

67
Q

What does adding agarose overlay do?

A

– prevents virus particles contacting the medium

68
Q

What causes plaque formation?

A

Virus – infects neighbouring cells cause plaque formation

69
Q

What are the stages to plaque assays?

A
  1. mix virus dilution with cells. plate. Overlayer cells with agarose
  2. remove agarose later, stain cells to visualize plaques in the monolayer
  3. virus titre is determined by counting plaques and multiplying by the dilution factor. Plaque counts from at least 3 replicates at each dilution should be averaged

PRIS (16 decks)

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