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Virology > Paramyxoviruses > Flashcards

Paramyxoviruses Flashcards

1
Q

“Para”

A

Other, next to

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2
Q

“Myxa”

A

Mucus

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3
Q

What type of genome?

A

nonsegmented (-)ssRNA

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4
Q

What type of structure?

A

Helical nucleocapsid with a pleomorphic envelope

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5
Q

Rinderpest morbillivirus

A

Cattle plague with almost 100% fatality

Eradicated in 2011 by vaccines

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6
Q

Morbilivirus

A

Italian for “little disease” because big disease was The Plague

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7
Q

Where did measles come from?

A

Zoonotic transmission from rinderpest virus. Couldn’t have existed until about 5000 years ago because that’s when we had large enough civilizations to feed it

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8
Q

What is the VAP?

A

Hemagglutinin

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9
Q

What is used for membrane fusion?

A

A fusion protein (F)

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10
Q

Does measles have Neuraminidase?

A

No

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11
Q

Nucleoprotein (N)

A

Coats the RNA genome

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12
Q

Large protein (L)

A

The RNA dependent RNAP

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13
Q

Phosphoprotein (P)

A

A cofactor needed for RNAP and to attach the nucleoprotein to the genome

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14
Q

Life cycle

A
  1. Attachment - Hemagglutinin binds host SLAM
  2. Penetration/entry - fusion protein (F) fuses plasma membranes
  3. Uncoating
  4. Gene expression - mRNA synthesis using viral RNAP in the cytoplasm (P and L)
  5. Genome replication - in the cytoplasm (N, P, and L)
  6. Assembly - at plasma membrane (N, P, and L)
  7. Release - via budding
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15
Q

How is the lifecycle different from orthomyxoviruses?

A

Replication occurs in the cytoplasm NOT the nucleus

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16
Q

mRNA synthesis uses which proteins?

A

P and L

17
Q

Genome replication uses which proteins?

A

N, P, L

18
Q

How does the virus know if a mRNA is used for genome replication or secondary transcription?

A

Genome replication has N, P, L
Secondary transcription has P, L

N means No stay

19
Q

How are (-)ssRNA genes expressed?

A

Viral RNAP converts (-)ssRNA to (+)ssRNA
Host translates (+)ssRNA (mRNA)
Some new (+)ssRNA is converted back to (-)ssRNA for genome replication

20
Q

Transcriptional polarity

A

3’ genes are transcribed more efficiently than 5’ genes because of polymerase skipping at polyU sequences between genes

21
Q

What is the first gene transcribed and why?

A

Nucleocapsid because need many copies of subunit

22
Q

What is the last gene transcribed and why?

A

L (the viral RNAP) because it can process many (-)ssRNA

23
Q

How is measles transmitted?

A

Respiratory aerosols
Fomites - contaminated object or surface

24
Q

What is a fomite?

A

A contaminated object or surface

25
Q

What is measles known for?

A

Being the most contagious human virus. One infected person infects on average 12-18 others

26
Q

What is needed to maintain measles?

A

A population size of 500,000 (16,000 newborns a year)

27
Q

Why do Guam and Bermuda have such high incidences of measles?

A

Goddamn tourists

28
Q

Primary site of replication?

A

Regional lymphoid tissues (macrophages and dendritic cells)

29
Q

Secondary sites of replication and how does it get there?

A

Dendritic cells carry it to T cells, B cells, and epithelial cells

30
Q

What is the receptor for primary replication?

A

SLAM

31
Q

What is the receptor for secondary replication?

A

Nectin-4 (epithelial cells)

32
Q

Common symptoms of measles

A

High fever
Red watery eyes
Bronchopneumonia
Congestion/Runny nose/Cough
Transient immunosuppression
Skin rash

33
Q

Rare symptoms of measles

A

Encephalitis
Subacute sclerosing panencephalitis (7-10 years after infection)
Death

34
Q

When are you infectious and why?

A

After a week because that’s when it can escape epithelial cells

35
Q

Immune amnesia

A

Severe but transient immunosuppression
Severe depletion of T cells and B cells = lose memory cells

36
Q

When does the body recover from immune amnesia?

A

36 months

37
Q

Measles live-attenuated vaccine (John Enders)

A

Many passages in human cells to create host range mutations because we are the only known host
Many passages in chicken cells to attenuate by host range mutations and temperature mutations

38
Q

Henipaviruses

A

Paramyxoviruses of zoonotic concern (Hendra virus and Nipah virus)

From bats

Virology (18 decks)

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