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Virology > Flaviviruses > Flashcards

Flaviviruses Flashcards

1
Q

Genome type

A

(+)ssRNA

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2
Q

Capsid structure

A

Icosahedral

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3
Q

Enveloped?

A

Enveloped

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4
Q

VAP and does it do fusion?

A

Envelope (E) protein which also has fusion activity

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5
Q

E protein

A

VAP, fusion activity, antiparallel homodimers forms icosahedral-like structure around the capsid

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6
Q

C protein

A

Capsid, forms true icosahedron

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7
Q

What do I mean when I state that the flavivirus lipid membrane is flanked by two icosahedral structures? Consider how this particle structure is advantageous in its transmission cycle.

A

The capsid (C) is a true icosahedron and the envelope (E) forms antiparallel dimers which assemble and are icosahedral-like

The E proteins protect the membrane

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8
Q

M protein

A

Matrix protein, connects E and C proteins

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9
Q

What mainly transmits them?

A

arthropod secondary vectors (ticks and mosquitos)

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10
Q

Host receptors (Just know one)

A

TIM

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11
Q

How does it enter the cell?

A

Receptor mediated endocytosis
Antibody mediated endocytosis

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12
Q

Is fusion involved and if it is is it pH dependent?

A

Acidification caused fusion and the virus leaves the endosome

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13
Q

Where is it replicated in the cell?

A

In the cytosol

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14
Q

What serves as the flavivirus mRNA transcript?

A

A single Open Reading Frame is translated into one polyprotein that integrates into the ER membrane

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15
Q

How are discrete, individual proteins made?

A

Viral and host proteases cleave it into 10 proteins

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16
Q

Where is the polyprotein processed?

A

ER

17
Q

Where is it assembled?

A

ER

18
Q

What happens after assembly?

A

It moved through the golgi and the acidification turns it from rough to smooth

19
Q

How does pH affect the maturation state of flaviviruses?

A

Low pH = smooth = mature

High pH = rough

20
Q

Furin

A

Cleaves pr to make the virus permanently smooth (and mature)

21
Q

How many proteins are translated?

A

A single ORF is translated into a giant polyprotein which integrates into the ER membrane

22
Q

How many final proteins are there?

A

The polyprotein is cleaved by virus and host proteases into 10 functional proteins

23
Q

What is “breathing”

A

The process of particles going from spiky to smooth and back depending on pH (low = smooth) and temperature

24
Q

Example viruses

A

Yellow fever
Dengue fever
West Nile
Zika

25
Q

Yellow fever primarily replicates in what ecosystem

A

African and South America in the jungle (sylvatic) cycle with mosquitoes and nonhuman primates

26
Q

How is fellow fever sustained in the city

A

Humans and mosquitoes

27
Q

Yellow fever Pathogenesis

A
  1. Mosquito feeds and innate cells are recruited
  2. Virus infects local immune cells (dendritic)
  3. Dendritic cells go lymph nodes and activate adaptive
  4. Viremia spreads virus to organs
  5. Secondary replication in liver and cause severe liver damage
28
Q

Primary site of replication for yellow fever

A

Local dendritic cells

29
Q

Secondary site of infection for yellow fever

A

Hepatocytes

30
Q

Primary site of infection for dengue fever

A

Innate immune cells (dendritic, mast, macrophages)

31
Q

Secondary sites of infection for dengue fever

A

Liver and spleen

32
Q

Antibody dependent enhancement

A

Prior infection with one serotype creates antibodies that ENHANCE infection of other serotypes

New serotype is NOT NEUTRALIZED by old antibodies and is internalized in monocyte and replicates in it

33
Q

Dengue fever transmission

A

Aedes aegypti or albopictus mosquitoes
Mother to fetus

34
Q

West Nile transmission

A

Mosquitoes spread to birds and vice versa
Mosquitoes also spread to horses and us

35
Q

Zika transmission

A

Most = mosquito to human
Other = mother to fetus, sex, blood transfusion

36
Q

Why can both humans AND mosquitos be considered primary reservoirs for some flaviviruses?

A

All flaviviruses cause viremia which then causes the spread between human and mosquito/arthropod vectors and the virus replicates in BOTH of us

37
Q

Appreciate the impact ecological disturbances and climate change may have on flavivirus distribution (and why this is).

A

We are encroaching on the jungle (sylvatic cycle) and are exposed to more non human primates and infected mosquitos from them

Warmer temps allow mosquitos to travel to new places and take longer to freeze to death

Virology (18 decks)

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