Virology Final Part 4

Question 1

What is the structure of the influenza virus?

Answer 1

Enveloped, (-) sense segmented RNA genome, pleomorphic, each segment of RNA separately encapsulated with several copies of the NP and has own polymerase complex

Question 2

What proteins are embedded on the influenza virus envelope?

Answer 2

Hemagglutinin, neuraminidase, matrix protein

Question 3

What is the function of H protein on the influenza virus?

Answer 3

Attachment to the host cell

- release of the viral RNA into the cell by causing fusion of viral and cellular membranes

Question 4

What is the N protein for on the influenza virus?

Answer 4

Release from the host cell?

Question 5

What is the function of the matrix protein?

Answer 5

Allows H+ to enter— important for uncoating

Question 6

How are each of the segments of the influenza genome organized?

Answer 6

Each is organized into a ribonucleoprotein (RNP)

Question 7

What is the structure of a RNP?

Answer 7

RNA coated with NP and packaged with RDRP

Question 8

What makes up the RDRP complex?

Answer 8

PB1, PB2, PA

Question 9

What is the host’s virus receptor for influenza? What is the anti receptor?

Answer 9

Sialic acid; hemagglutinin

Question 10

Why is influenza preferential to humans?

Answer 10

The human anti-receptors fit better with human SA

Question 11

Why are pigs mixing vessels for influenza?

Answer 11

They have two forms of SA on their cells

Question 12

Most human influenza illnesses are due to which H types?

Answer 12

1, 2 and 3

Question 13

How do you name an influenza strain?

Answer 13

• antigenic type
• (sometimes host of origin)
• geographical origin
• strain number
• year of collection
• virus subtype

Question 14

What is the function of tryptase Clara?

Answer 14

It cleaves H0 to form H1 and H2 so it will undergo a pH dependent change and reveal the fusion peptide

Question 15

Where is the influenza genome replicated?

Answer 15

In the cells nucleus

Question 16

What two modifications are needed for the virus to get its genome into the cytoplasm?

Answer 16

1. Tryptase Clara cleaves H to reveal fusion peptide
2. pH dependent change in the endosome allows H to unfold so the fusion peptide inserts into the endosome membrane
3. H+ enters the cavity and separates the RNPs from the matrix protein

Question 17

What must the virus do so that it can replicate and transcribe its genome?

Answer 17

• has pre-formed RDRP packaged inside

- has a gene that encodes the RDRP

Question 18

How does influenza generate mRNAS that can compete for access to the ribosome?

Answer 18

• cap stealing from cellular mRNA and a primer to provide the 3’OH group
• the viral genome has a signal to construct poly(A) tail on the mRNA
• the cellular mRNA is destroyed when the virus steals the cap to synthesize its own mRNA— eliminates competition

Question 19

What does influenza need to encode?

Answer 19

• RDRP, structural proteins, envelope proteins

Question 20

How do the genes get split apart?

Answer 20

The fragments with two genes use the cell’s splicing enzymes to modify RNA so that its monocistronic

Question 21

What are the two types of (+) RNA that influenza synthesizes during its replication cycle?

Answer 21

Incomplete and complete

Question 22

What is incomplete RNA?

Answer 22

• mRNA needed for protein synthesis

- made early in the replication cycle by stealing 5’ caps

Question 23

What is complete (+) RNA?

Answer 23

• a template to replicate the genome
• made later in the cycle and not used as mRNA
• the alternate conformation of the RNA POL does not require a primer

Question 24

What are the two conformations of RNA POL?

Answer 24

1. Open: conformation for making mRNA, needs a primer

2. Closed: for replicating the genome, no need for primer

Question 25

What are the three sites on the open conformation of the RDRP?

Answer 25

1. endonuclease (cleaves polypeptide chain)
2. Binding of the 5’ end of the template
3. Site that reads the template and synthesizes the mRNA

Question 26

How does cap stealing work?

Answer 26

• the polymerase complex binds a host cell mRNA by its cap, and the endonuclease cuts the cap off the mRNA
• the mRNA stays on the complex and is used as a primer

Question 27

How does influenza do mRNA synthesis?

Answer 27

• The polymerase reads the (-) template and adds complimentary nucleotides to the end of the cellular mRNA fragment

Question 28

How many of the segments undergo splicing after translation, but before it goes to the cytoplasm?

Answer 28

2 out of 8

Question 29

Where is the mRNA for the H, N and M2 proteins translated? Where is the rest of the mRNA translated?

Answer 29

A ribosome associated with the ER; cytoplasmic ribosomes

Question 30

What is the first component of the virus that assembles at the plasma membrane?

Answer 30

RNP’s and M1 proteins

Question 31

What promotes membrane fission?

Answer 31

M2

Question 32

What controls the release of the virus?

Answer 32

Neuraminidase— cleaves the sialic acid residues from the virus and the host cell

Question 33

Why does the virus remove sialic acid from the host cell? Why is it removed from the virus?

Answer 33

To ensure the newly release particle does not reinfect the cell; to prevent the virus particles from sticking together

Question 34

How does an “already infected with influenza” cell die?

Answer 34

Programmed cell death (apoptosis, necropoptosis, pyropoptosis