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Infection and Immunity > 13 Virus 1 > Flashcards

13 Virus 1 Flashcards

1
Q

what are viruses

A

obligate intra-cellular parasites

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2
Q

what surrounds a virus

A

nucleic acid surrounded by protein capsid or protein shell

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3
Q

how do viruses enter cells

A

via interaction with specific cell receptors = TROPISM

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4
Q

what happens when a virus enters a cell

A

following cell enter the host cell machinery is hijacked = synthesis of new virus

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5
Q

how is a virus released

A

released by budding (enveloped virus) or by cell lysis or via secretory pathway

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6
Q

what is an orphan virus

A

virus that doesn’t result in disease

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7
Q

virion

A

virus particle

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8
Q

Virus structure - nucleic acid

A

can be DNA or RNA

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9
Q

nucleocapsid

A

nucleic acid plus protein

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10
Q

how are capsids arranged

A

arranged in symmetrical patterns

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11
Q

HIV structural arrangement

A

HIV has helical nucleocapsid and icosahedral core

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12
Q

what have some viruses developed from host cell membrane

A

some viruses also possess a lipid envelope derived from host cell membrane

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13
Q

what are some viruses involved in

A

involved in cell attachment and entry

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14
Q

what are some of the enzymatic functions viruses have

A

> for copying viral genome (polymerases)
for trimming viral proteins (proteases)
other modifying enzymes

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15
Q

how are viruses grouped

A 
according to their shared properties
nature of the nucleic acid: RNA or DNA
capsid symmetry
presence or absence of an envelope
size
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16
Q

how are virus families named

A

All Families have the suffix -viridae (e.g. retroviridae), whilst genera have suffix virus (e.g. flavivirus)

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17
Q

hierarchy of recognized viral taxa

A

(Order) > Family > (Sub-family) > Genus > Species

Not all viruses belong to a order or sub-family

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18
Q

RNA viruses

A

Take RNA put into cell and get a virus back

Use own polymerase to make a positive sense copy

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19
Q

what do viruses lack

A

mitochondria and ribosomes

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20
Q

what is used to replicate the viruses

A

polymerases required to replicate their nucleic acid genome (be it DNA or RNA)

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21
Q

where can virus replication occur

A

only in living cells

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22
Q

what mediates virus attachment to target cells

A

mediated by a specific interaction between a component (usually a protein) of the surface of the virus and a cellular receptor

23
Q

what is the capsid sometimes covered in when buds

A

sometimes the capsid is covered with the membrane of the host cell as the virus buds off

24
Q

how does a virus enter

A

Attachment and replication - Interaction with specific cell surface receptor
> Membrane fusion
- Receptor-mediated endocytosis

25
Q

what is receptor-mediated endocytosis

A

take things from outside of the cell and bring into inside

26
Q

Genome replication and virus protein production - RNA virus

A 
virion contents:
(-)RNA
dsRNA
(+)RNA
genome replication cycle RNA to RNA
27
Q

Genome replication and virus protein production - reverse-transcribing viruses

A

virion contents:
(+)RNA
dsDNA
genome replication RNA to DNA using reverse transcriptase

28
Q

Genome replication and virus protein production - DNA virus

A

virion contents:
ssDNA
dsDNA
genome replication DNA to DNA

29
Q

Virus release

A

Nucleocapsid assembly may take place in nucleus or cytoplasm
Envelope viruses bud through cell membrane (sometimes through golgi / ER)
Non-enveloped viruses mature in golgi / cytoplasm
- transported to surface via secretary vesicles
May or may not cause cell lysis

30
Q

Bacteriophage

A

Lytic phage
Temperate phage
Pseudolysogeny

31
Q

Lytic phage

A

phage genome replicated, phage capsid and tail proteins are synthesized using bacterial cell machineries; the phage genome is then packaged into progeny phage particles, which are liberated via bacterial lysis

32
Q

Temperate phage

A

phage genome integrated into bacterial chromosome (becoming a prophage)
persists as a latent or dormant phage
Prophages replicated together with bacterial host chromosome during host cell replication and switch into lytic production upon exposure to DNA damage

33
Q

Pseudolysogeny

A

bacterial cells can’t support DNA replication or protein synthesis
phage genome remains for extended period of time as a non-integrated preprophage, at which point the phage enters either a lysogenic or a lytic life cycle

34
Q

when does pseudolysogeny occur

A

nutrient-deprived conditions

35
Q

why does pseudolysigenic preprophage not replicate

A

Pseudolysogenic preprophage does not replicate and so is only inherited by one of the daughter cells following cell division

36
Q

Tobacco mosaic virus

A

ssRNA +ve

37
Q

Tobacco mosaic virus effect

A

causes mottling of leaves and fruits and affects tomatoes peppers cucumbers as well as tobacco

38
Q

what do human viruses usually cause

A

cell death and inflammation - damage to respiratory tract cells and aching body and fever as the inflammatory response of the immune system reacts to the virus proteins

39
Q

what do some latent infections cause

A

initial infection goes away but later a further sometimes slightly different infection breaks out from virus stored in the body- such as human Herpes viruses which cause chicken pox and shingles

40
Q

what is sputnik

A

Virophage virus that requires another virus to replicate inside the amoeba

41
Q

retrovirus advantages

A

effective over long periods
efficient transfection ex vivo
low immune response in host

42
Q

retrovirus disadvantages

A

small, max 8kb insert size
inefficient transfection in vivo
relies on target cell mitosis
safety concerns

43
Q

retrovirus type

A

integrates with host chromatin

44
Q

lentivirus advantages

A

transfects proliferating and non-proliferating hosts and haemo stem cells
new generation are self-inactivating for safety

45
Q

lentivirus disadvantages

A

need active transport into cell
small, max 8kb insert size
technologically challenging
safety concerns, immunodeficiency origins

46
Q

adeno-associated virus advantages

A

very good length of expression especially in vivo
efficient transfection in vivo
low immune response in host

47
Q

adeno-associated virus disadvantages

A

safety problems owing to potential insertional mutagenesis
small, max 4.5kb insert size
high immuno response
technologically challenging

48
Q

adeno-associated virus type

A

either

49
Q

adenovirus advantages

A

highly efficient transfection in vivo and ex vivo

transfects proliferating and non-proliferating hosts

50
Q

adenovirus disadvantages

A

repeat treatments ineffective due to strong immune response
small, max 7.5kb insert size
technologically challenging
short expression duration

51
Q

adenovirus type

A

extra chromosomal DNA

52
Q

herpes simplex virus advantages

A

very good length of expression especially in vivo
safe for use in immunocompromised patients
large insert size up 30kb
effective on many cell types

53
Q

herpes simplex virus disadvantages

A

difficult to produce in large quantities

54
Q

herpes simplex virus type

A

extra chromosomal DNA

Infection and Immunity (29 decks)

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