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Virology > Segmented Viruses > Flashcards

Segmented Viruses Flashcards

1
Q

Orthomyxoviridae characteristics?

A

-Group 5–>(-)ssRNA
-enveloped
-helical
-segmented
-replicates in NUCLEUS not cytoplasm
-cap-snatching

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2
Q

What is an advantage and disadvantage to being segmented?

A

Adv: Genes can be individually transcribed b/c diff promoters
Disadv: All segments need to be in genome to be infectious–>if missing even just 1 segment = NOT INFECTIOUS

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3
Q

Where does influenza virus replicate?

A

NUCLEUS

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4
Q

How many segments does influenza virus usually have?

A

7 or 8 segments

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5
Q

How do segmented viruses rapidly evolve?

A

Reassortment of segments

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6
Q

Genetic drift (Antigenic drift in flu)

A

Changes that happen because of error prone polymerase
-point mutations, insertions, deletions

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7
Q

Genetic shift (Antigenic shift in flu)

A

Changes that happen because of reassortmnet

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8
Q

Which causes bigger changes, genetic drift or shift

A

Genetic shift

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9
Q

What pathogens are in Orthomyxoviridae?

A

Influenza A, B, and C

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10
Q

Which strain of influenza are pandemic and why?

A

Influenza A because it has animal hosts and can get new segments through antigenic shift

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11
Q

Why was the Spanish flu unique?

A

Infected mostly healthy adults

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12
Q

How does influenza enter?

A

Hemagglutinin (HA) binds to sialic acid

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13
Q

How does influenza exit?

A

Neuraminidase (NA) cleaves sialic acid

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14
Q

What is the reservoir for influenza?

A

Water fowl

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15
Q

True or false: Birds can directly infect humans

A

FALSE
-Birds have 2,3 sialic acid bond while humans have 2,6 so they cannot infect
-Need intermediate host like pigs that have both 2,3 and 2,6
-Bird infect–>pig infects–>human

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16
Q

True or false: Novel influenza strains (pandemic) come from reassorted strains

A

True

17
Q

Why do we need a new flu vaccine every year?

A

Flu viruses evolve through antigenic drift which causes 1 strain of flu to be selected and take over every year

18
Q

Where does influenza make its proteins and packaging?

A

Cytoplasm

19
Q

True or false: Proteins can get translated in nucleus

A

False
-there are no ribosomes in nucleus
-mRNA translation/proteins are made in cytoplasm

20
Q

What is cap-snatching?

A

Segmented viruses steal 5’ ends from host (10-20 bp) to start their transcription

21
Q

What are 3 advantages of cap-snatching?

A
  1. Don’t have to encode capping machinery
  2. Nor recognized by immune system
  3. Shuts off host translation
22
Q

Where does alternative splicing only happen?

A

Nucleus

23
Q

What is an advantage for influenza by replicating in nucleus?

A

Can use host alternative splicing machinery to make more different types of proteins

24
Q

How can we inhibit influenza?

A

-Zanamivir
-Tamiflu
-act as sialic acid–>NA will bind to this instead of actual sialic acid–>sialic acid will not be cleaved–>virus cannot exit & replicate

25
Q

Bunyavirales characteristics

A

-Group 5–>(-)ssRNA
-segmented
-enveloped
-cap snatch
-helical
-replicates in CYTOPLASM
-only 2-3 segments

26
Q

What pathogens are in Bunyavirales?

A

-Lassa virus (mouse)
-Haantan and Sin Nombre ( mouse)
Rift valley fever (Arbovirus-mosquito)
-Crimean-Congo hemorrhagic fever (Arbovirus-tick)

27
Q

True or false: Lassa spreads human to human

A

False
-Does not spread person to person
-Get it by coming into contact with mouse urine/feces

28
Q

Reoviridae characteristics

A

-GROUP 3–>dsRNA
-segmented
-replicates in cytoplasm
-non enveloped
-icosahedral
-transcription happens INSIDE CAPSID
-10 to 12 segments

29
Q

Why do reoviridae need to replicate inside capsid?

A

If dsRNA was in cytoplasm the cell would do an immune response so it stays in the capsid shell

30
Q

How do reoviridae enter and exit?

A

Non enveloped
-Entry: penetrate membrane
-Exit: lysis

31
Q

Is it surprising that reoviridae can cause diarrhea?

A

No since it is non enveloped it is environmentally stable and can live in GI tract

32
Q

What pathogens are in reoviridae?

A

Rotavirus

Virology (19 decks)

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