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Management of Infection > Lecture 3D - Viruses > Flashcards

Lecture 3D - Viruses Flashcards

1
Q

What is the genetic structure of viruses?

A

they are acellular

they contain DNA and RNA

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2
Q

How do viruses reproduce?

A

inside cells and rely upon the host cell machinery to survive and reproduce

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3
Q

What are prions?

A

a novel form of infectious proteins which have no DNA at all

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4
Q

Why can prions (and maybe viruses) not be considered as independent living organisms?

A

they do not possess the machinery to reproduce themselves, but require intracellular enzymes, metabolic pathways and organelles in order to reproduce

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5
Q

What are viruses?

A

non living obligate intracellular parasites that need a host cell in order to replicate

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6
Q

How do viruses contain genetic info?

A

they possess their own genetic info in the form of RNA or DNA

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7
Q

What form do viruses also have?

A

an extracellular form

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8
Q

What can viruses infect?

A

all types of cellular organisms including plants and animals

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9
Q

What are some strains of virus associated with?

A

increased risk of cancer

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10
Q

What happens if viruses have genetic information in the form of RNA?

A

usually it will have to be reverse transcribed back to DNA in order for the virus to replicate

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11
Q

What are the aims of infectious virus particles?

A

to be able to invade a host cell to replicate and to be able to transmit from one host organism to another

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12
Q

What are successful viruses?

A

they tend to not kill their host, as it does not help the survival of the viral strain

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13
Q

How are polio and hepatitis A transmitted?

A

faecal-oral route

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14
Q

How is rabies transmitted?

A

bite of an infected animal e.g. rabid dog or bat

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15
Q

How is human papilloma virus (warts) transmitted?

A

skin contact

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16
Q

How is herpes 1&2, HPV, hepatitis B and HIV transmitted?

A

sexual transmission

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17
Q

How is ebola transmitted?

A

all body fluids and tissues

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18
Q

How is influenza, colds, measles, mumps, rubella transmitted?

A

respiratory

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19
Q

How is yellow fever, dengue fever, chikungunya virus transmitted?

A

insect vectors

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20
Q

What is COVID-19?

A

a coronavirus which can cause severe acute respiratory syndrome

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21
Q

Extracellular form viral structure?

A

diverse sizes, shapes and chemical composition

nucleic acid surrounded by protein coat (capsid)+/-lipid envelope

mainly rod shapes with a helical nucleic acid or icosahedral with spherical nucleic acid

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22
Q

What do viruses have surrounding their icosahedral shape?

A

filamentous fibres

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23
Q

What do viruses have at their core?

A

their genetic material, either DNA or RNA

and often some enzymes needed for cell entry during infectin and replication

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24
Q

What are viruses with RNA?

A

retroviruses, the RNA needs to be reverse transcribed in order for the virus to replicate

25
Q

What is the lipoprotein bilayer on a virus?

A

envelope (some viruses)

derived from the host

26
Q

What viruses have lipoprotein bilayer?

A 
DNA = hepatitis B
RNA = rabies, rubella
27
Q

What is the protein shell?

A

the capsid - nearly all viruses have this

this encapsulates their genomic material

28
Q

Naked viruses?

A 
DNA = papilloma 
RNA = hepatitis E
29
Q

What do the glycoprotein spikes do?

A

they bind to the target protein in the host and trigger the sequence of events which enables the virus to enter the cell

30
Q

Size of the largest viruses?

A

300-400nm across with a 100nm layer of filamentous fibres surrounding their icosahedral shape

31
Q

Size of COVID-19 virus?

A

50-150nm in diameter without the spikes

32
Q

DNA virus replication?

A

when the DNA is inserted into the host cell, it uses the host cells RNA polymerase to make mRNA, which is the translated by the ribosomes of the host cell

33
Q

RNA virus replication?

A

have several ways to replicate

some carry their own RNA polymerase to produce mRNA

some have to carry out an additional step so that the negative or antisense) RNA is converted to positive (sense) RNA, from which mRNA is made

34
Q

What do retroviruses have to do?

A

reverse transcribe their RNA into DNA which is then inserted into the host cell genome

35
Q

How does a virus with a lipid envelope leave the cell after replication?

A

it wraps itself in the membrane and buds off from the cell, to then travel onto the next target cell

36
Q

How does a virus without a lipid envelope leave the cell?

A

it escapes by rupturing the cell membrane (cytosis) as it is released, killing the host cell

it is therefore cytopathic

37
Q

What are prion protein diseases?

A

rare, fatal neurodegenerative diseases belonging to amyloid group

38
Q

What do prion protein diseases affect?

A

Humans (Creutzfeld jacob disease) and agricultural, zoo and wild animals

39
Q

Examples of prion protein diseases?

A

scrapie in sheep

bovine spongiform encephalopathy in cows

chronic wasting disease in elk and deer

40
Q

Aetiology of prion protein diseases?

A

genetic, sporadic and infectious

41
Q

Incubation period of prion protein diseases?

A

they can have lengthy incubation periods >40 years!

42
Q

Clinical characteristics of prion protein diseases?

A

dementia and ataxia

neuronal loss, gliosis and spongiform change in the brain

43
Q

Immune response to prion protein diseases?

A

no classical host immune response

44
Q

Treatment of prion protein diseases?

A

currently no treatments available for the disease, has to be managed by trying to eliminate the spread

45
Q

What is a marker of astrocytic gliosis?

A

glial fibrillary acidic protein

46
Q

What is detected by antibodies?

A

the prion protein

47
Q

What is one of the characteristic of prion diseases?

A

the accumulation of aggregates of abnormally folded prion protein (PrP)

48
Q

Structure of the normal prion protein PrPC?

A

3% beta sheet

monomeric and soluble

protease sensitive (PrPsen)

neuroprotective

49
Q

Structure of infectious form of the prion protein (PrPSc)?

A

disease associated form

43% beta sheet

aggregated and insoluble

partially protease resistant (PrPres)

infectious, toxic

50
Q

What is the infectious agent of prion disease not associated with?

A

any nucleic acids

there is no detectable viral agent in the infectious particle

51
Q

Why is PrPC easy to break down?

A

it has a relatively open structure

52
Q

What happens when the aggregates of PrPSc are formed?

A

they are hard to break down and can induce normally folded prion protein to misfold, propagating the number of infectious particles

53
Q

Prion hypothesis?

A

prions are transmissable particles that are devoid of nucleic acid and seem to be composed entirely of a modified protein (PrPSc)

54
Q

How is PrPC converted to PrPSc?

A

through post translation process during which is acquires a high beta sheet content

55
Q

What do prions appear to encipher?

A

strain-specific properties in the tertiary structure of PrPSc

56
Q

How is PrPSc broken down?

A

it is protease resistant and can only be broken down at a very slow rate by the cell

57
Q

What does the misfolding of PrPC require?

A

the assistance of an additional unknown chaperone protein called protein X

(stanley prusiner 1998)

58
Q

What does prion mean?

A

a protein only infectious agent

Management of Infection (36 decks)

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