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Infection and Immunity > Retroviruses > Flashcards

Retroviruses Flashcards

1
Q

what type of genome does the Rous sarcoma has?

A

RNA genome

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2
Q

what is Crick’ “Central Dogma”?

A

“once information has got into a protein it can’t get out again”

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3
Q

what is the Rous sarcoma virus replication dependent on?

A

DNA

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4
Q

what effects does Actinomycin D has on RNA synthesis?

A

Actinomycin D inhibits transcription and hence RNA synthesis

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5
Q

what inhibits virus growth?

A

Actinomycin D

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6
Q

what route did the effects of actinomycin D in sarcoma suggested?

A

RNA -> DNA -> RNA -> Protein

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7
Q

what is the provirus hypothesis?

A

the provirus of Rous sarcoma is a region of DNA homologous with viral RNA stably integrated into the molecule of cellular DNA in the nucleus

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8
Q

what is used to fight against HIV?

A

reverse transcriptase inhibitors

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9
Q

what is the viral RNA dependent on?

A

DNA polymerase

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10
Q

what does the reverse transcriptase do?

A

turns RNA back to DNA

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11
Q

what are the subfamilies in the family retroviridae?

A

orthoretrovirinae and spumaretrovirinae

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12
Q

how are retroviruses transmitted?

A

transmission typically via close contact (oronasal, sexual, blood-borne)

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13
Q

why does the retrovirus have an envelope?

A

because it is susceptible to desiccation and detergents (that’s why the envelope has lipids)

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14
Q

what are the key features of retroviruses?

A
  • two copies of RNA genome in each viral particle
  • reverse transcribe RNA to DNA
  • DNA “provirus” integrates into cellular DNA
  • establish persistent infections
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15
Q

what does the “gag” gene encode in the retrovirus genome?

A

core structural proteins

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16
Q

what does the “pol” gene encode in the retrovirus genome?

A
  • enzymes for replication
  • reverse transcriptase
  • integrase
  • protease
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17
Q

what does the “env” gene encode in the retrovirus genome?

A

envelope glycoproteins

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18
Q

how do retroviruses infect cells?

A

by binding to a cell surface molecule called the receptor

- it binds to a nuclear pore and once it binds it starts replicating

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19
Q

what is necessary for a productive viral life cycle?

A

integration

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20
Q

where do simple retroviruses (e.g. FeLV) integrate?

A

in dividing cells

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21
Q

where can lentiviruses (e.g. HIV) integrate?

A

in non-dividing cells

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22
Q

what is integration?

A

the retroviral genome integrates into the cellular DNA and becomes part of the host

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23
Q

how much of the human genome is derived from ancestral retrovirus infections?

A

8.3%

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24
Q

what does integration do?

A

maximises the chance of viral transmission

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25
which retroviruses integrate?
All
26
how does the retroviral assembly work?
- RNA makes a poliprotein (single long protein? - sticks under membrane - bends the membrane - becomes more circular - protein inserted in this new molecule - has to be cut off from membrane - forms an immature molecule - then matures
27
where do some of the retroviruses assemble?
at the pericentriolar region of the nucleus, the fully assembled particles then migrates to the cell surface
28
is there any vaccine against retroviruses that is effective?
only the feline leukaemia (FeLV) vaccine works
29
what does the FeLV cause?
immunosuppression, tumours, anaemia
30
which are the subgroups of FeLV?
three subgroups: A, B, C, classified according to the viral envelope glycoprotein
31
from where has the FeLV-A subgroups been isolated?
from all infected cats
32
where are the FeLV-B and C subgroups generated?
within the host
33
how viral is FeLV?
Cats may clear the virus or become persistently infected
34
what do retroviruses establish?
persistent infections
35
what does the bovine leukaemia virus cause?
zoonotic bovine leukosis
36
what does the bovine leukaemia virus infect?
B lymphocytes
37
are there free virus in the blood in bovine leukosis?
No
38
what doe persistently infected cattle produce?
antibodies
39
what does viral tax protein trans activates?
cellular genes
40
how is bovine leukaemia virus transmitted?
via infected cells e.g. milk, blood
41
how can bovine leukaemia virus be transmitted?
vertically or horizontally
42
which are the oncogenic retroviruses?
- alpha avian leukosis viruses (ALV) - beta Jaagsiekte sheep retrovirus (JSRV) - gamma feline leukaemia virus (FeLV) - delta bovine leukaemia virus (BLV)
43
what are the mechanisms of retroviral oncogenesis?
- oncogene capture and transduction - insertional activation - insertion leading to truncation - insertion leading to gene inactivation - other mechanisms
44
how can retroviral proteins lead to tumour formation?
they can deregulate normal cellular metabolism and lead to tumour formation
45
what are the effects of an infection with oncogenic virus in the cell?
- loss of contact inhibition - increased saturation density - increased growth rate - anchorage-independent growth - tumorigenic in appropriate hosts
46
what causes OPA?
a retrovirus called JSRV
47
where does JSRV replicate?
only in type II pneumocytes and club cells
48
what are club cells?
bronchiolar exocrine cells
49
what does replication lead to?
To transformation of every cell
50
what does the viral Env switches on?
signals for cell division and activates cell signalling pathways
51
what is the incubation period of Maedi-Visna Virus (MVV)?
approx. 2 years
52
what does MVV cause?
ovine progressive pneumonia
53
how is equine infectious anaemia virus (swamp fever) transmitted?
by bitting insects (horseflies)
54
what is associated with the emergence of viral emergents?
episodic pyrexia/illness
55
what are the treatments for swamp fever?
there are no treatment options
56
what is swamp fever related to?
immune complex formation, complement activation
57
what are the immunodeficiency-causing lentiviruses?
- feline immunodeficiency virus - human immunodeficiency virus - simian immunodeficiency virus
58
how many people are currently infected by HIV?
35 million people
59
how many deaths in sub-Saharan Africa are caused by AIDS?
76%
60
where do the endogenous retroviruses (ERVs) genome persists?
in host DNA
61
what does the integration of the retrovirus into the germ cellular DNA cause?
vertical transmission of viral DNA to offspring
62
what are ERVs?
transposable (mobile) genetic elements
63
are ERVs defective?
most of them, but not all
64
what do ERV-derived genes may provide to the host?
useful or essential functions to the host e.g. syncytin in placental morphogenesis
65
what is the fusion of the trophoblast cell layer into the continuous multinucleate syncytiotrophoblast associated with?
implantation of the embryo
66
what mediates the trophoblast cell fusion?
the expression of the HERV-W Env (envelope)
67
for what have retroviral vectors been developed?
gene therapy
68
what may the integration of DNA provirus lead to?
development of cancer
69
what is the integration of DNA provirus used for?
exploited for gene therapy

Infection and Immunity (20 decks)

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