Paramyxoviruses

Question 1

“Para”

Answer 1

Other, next to

Question 2

“Myxa”

Answer 2

Mucus

Question 3

What type of genome?

Answer 3

nonsegmented (-)ssRNA

Question 4

What type of structure?

Answer 4

Helical nucleocapsid with a pleomorphic envelope

Question 5

Rinderpest morbillivirus

Answer 5

Cattle plague with almost 100% fatality

Eradicated in 2011 by vaccines

Question 6

Morbilivirus

Answer 6

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

Question 7

Where did measles come from?

Answer 7

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

Question 8

What is the VAP?

Answer 8

Hemagglutinin

Question 9

What is used for membrane fusion?

Answer 9

A fusion protein (F)

Question 10

Does measles have Neuraminidase?

Answer 10

No

Question 11

Nucleoprotein (N)

Answer 11

Coats the RNA genome

Question 12

Large protein (L)

Answer 12

The RNA dependent RNAP

Question 13

Phosphoprotein (P)

Answer 13

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

Question 14

Life cycle

Answer 14

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

Question 15

How is the lifecycle different from orthomyxoviruses?

Answer 15

Replication occurs in the cytoplasm NOT the nucleus

Question 16

mRNA synthesis uses which proteins?

Answer 16

P and L

Question 17

Genome replication uses which proteins?

Answer 17

N, P, L

Question 18

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

Answer 18

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

N means No stay

Question 19

How are (-)ssRNA genes expressed?

Answer 19

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

Question 20

Transcriptional polarity

Answer 20

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

Question 21

What is the first gene transcribed and why?

Answer 21

Nucleocapsid because need many copies of subunit

Question 22

What is the last gene transcribed and why?

Answer 22

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

Question 23

How is measles transmitted?

Answer 23

Respiratory aerosols
Fomites - contaminated object or surface

Question 24

What is a fomite?

Answer 24

A contaminated object or surface

Question 25

What is measles known for?

Answer 25

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

Question 26

What is needed to maintain measles?

Answer 26

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

Question 27

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

Answer 27

Goddamn tourists

Question 28

Primary site of replication?

Answer 28

Regional lymphoid tissues (macrophages and dendritic cells)

Question 29

Secondary sites of replication and how does it get there?

Answer 29

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

Question 30

What is the receptor for primary replication?

Answer 30

SLAM

Question 31

What is the receptor for secondary replication?

Answer 31

Nectin-4 (epithelial cells)

Question 32

Common symptoms of measles

Answer 32

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

Question 33

Rare symptoms of measles

Answer 33

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

Question 34

When are you infectious and why?

Answer 34

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

Question 35

Immune amnesia

Answer 35

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

Question 36

When does the body recover from immune amnesia?

Answer 36

36 months

Question 37

Measles live-attenuated vaccine (John Enders)

Answer 37

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

Question 38

Henipaviruses

Answer 38

Paramyxoviruses of zoonotic concern (Hendra virus and Nipah virus) From bats