Shein - - Strand RNA Viruses Part 1

Question 1

WHat class of negative strand RNA viruses does the influenza virus fall under?

Answer 1

Orthomyxoviridae

Question 2

Structure of the influenza virus

• envelope
• matrix
• nucleocapsid

Answer 2

Envelope - lipid bilayer with a spherical appearance and derived host membranes. There are two glycoprotein spikes - Neuraminidase and Hemaglutinin

Matrix - adds stability and structure. Has two matrix proteins called M1 and M2.

Nucleocapsid - The genome has a negative polarity and there are proteins in the nucleocapsid as well.

Question 3

Neuraminidase and Hemagluttinin

Answer 3

The two glycoprotein spikes on the influenza virus.

Hemaglutinin - Attaches strongly to the host cells receptors which are comprised largely of sialic acid. Causes agglutination of RBCs.

Neurominidase - involved in cell to cell spreading

Question 4

Antibodies against Hemaglutinin and neurominidase

Answer 4

Anti-Hemaglutinin - neutralizing antibody

Anti-neuraminidase - non-neutralizing. Rather causes it to stick to the cell and halt cell to cell spreading.

Question 5

M1 and M2

Answer 5

Matrix proteins of the influenza virus

• M1 - interacts with glycoproteins
• M2 - ion control, can alter pH

Question 6

What is the shape of the nucleocapsid for influenza virus?

Answer 6

Helical

Question 7

Replication of influenza RNA

Answer 7

It is a negative strand that comes in. A + strand is made and then another - strand is made to act as a template for the full length genome.
- major difference between this and other SS + RNA is that this one replicates in the nucleus.

Question 8

Pathogenesis of influenza viruses

Answer 8

Spread by respiratory secretions

Can cause Viremia in some viruses, while others are limited to the respiratory tract. This causes cellular and cilia destruction, which allows for secondary bacterial infections to occur.

Question 9

Reye’s Syndrome

Answer 9

Following a viral infection such as varicella or influenza, people used to get brain damage and liver dysfunction. The cause is unknown but it is associated with use of ASPIRIN

Question 10

Immunity against influenza viruses

Answer 10

• there are anti-HA and anti-N antibodies.
• we have IgA in nasal secretions, which are protective but only last 6 months. This is one reason we get the flu shot every year.
• we have IgG in serum which is not as protective.

Question 11

What are the different strains of influenza?

Answer 11

A B and C

Question 12

Antigenic Drifts

Antigenic Shifts

Answer 12

Drifts - minor point mutations that accumulate over the years and eventually give you a new AA change which may or may not change the protein.

Shifts - Major changes that occur quicker. They are a reassormtent of different HA and N types. So, for instance, if you have an H1N1 strain and an H2N2 strain, they can rearrange to create a H1N2 strain, which is new. This only occurs in Influenza A and is involved in pandemics.

Question 13

Sialic Acid-Galactose Receptor

- role in new viruses.

Answer 13

This is the receptor for influenza. The three main species that have this receptor are the birds, pigs, and us. The issue is that the birds and humans have different types and in different locations - humans in the respiratory tract and birds in the GI tract. The pigs though have both receptors in their respiratory tract. This allows them to be infected by both animals and reassortment to occur. This is the theory behind how a new virus can c one about.

Question 14

Influenza vaccines

Answer 14

Grown in eggs

Can be trivalent or quadravalent

Question 15

Swine flue

Answer 15

A type of influenza A ( H1N1)

• human to human transmission.
• it is a mix of genes from different animals.

Question 16

Avian Flu

Answer 16

Also a type of Influenza A

• human to human transmission.
• China only

Question 17

WHy is transcription of influenza inferential than most other - strand RNA viruses

Answer 17

Influenza is segmented and has 8 segments. Therefore, there is no need for post-transcriptional splicing. Most other - strand RNAs are non-segmented but the ribosomes create one positive RNA transcript at a time from one gene at a time.
- this is as opposed to + strand RNA viruses that make one long polypeptide and then are cleaved afterwards.

Question 18

What is the only negative double stranded RNA virus?

Answer 18

Rotavirus

Question 19

Which viruses have Segmented RNA??

Answer 19

BOAR

• Bunyaviridae
• orthomyxociridae
• Arenavirus
• reovirus

Question 20

Where is influenza virus replicated?

Answer 20

In the nucleus