Virology 3

Question 1

Baltimore Classification of Influenza?

Answer 1

Group 5: negative sense RNA

Question 2

Influenza belongs to what family?

Answer 2

Orthomyxoviridae
-Influenza is the only genus that belongs to this family

Question 3

Influenza can be divided into 3 types:

Answer 3

-Influenza A
-Influenza B
-Influenza C

Question 4

Influenza A:

Answer 4

-Can infect multiple species
-Most virulent
-Most important human pathogen
-Can further be defined based on serotypes

Question 5

Influenza B:

Answer 5

-Only infects humans and seals
-Less genetically diverse than influenza A
-1 serotype
-We obtain immunity to this strain at an early age

Question 6

Influenza C:

Answer 6

-Can infect multiple species
-Causes severe illness and local epidemic

Question 7

What are serotypes?

Answer 7

A subdivision of viruses based on antigenicity

Question 8

Influenza A can further be divided on serotypes:

Answer 8

-Divided based on two surface proteins
H:hemagglutinin (1-15)
N:neuraminidase (1-9) e.g H5N1

Question 9

Examples of hosts Influenza A effects:

Answer 9

-Birds
-Swine (pigs)
-Humans
-Horses
-Ferrerts, Mink
-Seals, whales

Question 10

Structure of influenza:

Answer 10

-100nm
-Spherical or filamentous (pleomorphic)
-Segmented genome
-Helical capsid
-Lipid envelope

Question 11

Components of influenza:

Answer 11

-11 proteins (HA and NA being the major ones)
-10 genes with overlapping reading frames
-Replicates in the nucleus
-RNA polymerase (PA, PB1/2)
-Nucleocapsid (NP)
-Non-structural proteins (NS1, NS2)
-Matrix proteins 1&2

Question 12

Major proteins in influenza

Answer 12

• NA
  -HA
  *These proteins are targeted by antiviral drugs

Question 13

Neuraminidase (NA) 1-9:

Answer 13

-Glycoprotein found on the outside of the viral particle
-Enzymes is involved in the release of the viral particles from the cell

Question 14

Haemagglutinin (HA) 1-15:

Answer 14

-Lectin protein that mediates binding and entry of the virus to target cells

Question 15

Influenza Genome organisation:

Answer 15

-8 segmented single stranded negative RNA genome
-Has no nucleic acid proof reading

Question 16

Influenza replication cycle: steps 1

Answer 16

1. Virus binds via HA to sialic acid receptors on susceptible cells and enters via endocytosis or Viropexis.

Question 17

Influenza replication cycle: steps 2

Answer 17

2. Virus nucleocapsid containing the negative viral RNA is transported to the nucleus

Question 18

Influenza replication cycle: steps 3

Answer 18

3. VRNA is transcribed to complementary viral +mRNA via VRNA polymerase

Question 19

Influenza replication cycle: steps 4

Answer 19

4. Viral complementary positive mRNA is either exported to cytosplasm and golgi/ER and translated or remains in the nucleus

Question 20

Influenza replication cycle: steps 5:

Answer 20

5. The viral proteins return to nucleus and induce new negative viral RNA and nucleocapsid

Question 21

Influenza replication cycle: steps 6, 7, 8

Answer 21

6. HA and NA proteins migrate to plasma membrane
7. Matrix and NS2 shutoff replication deliver nucleocapsid to plasma membrane
8. Virus assembles and buds from cell and the host cell dies

Question 22

The synthesis of mRNA in influenza is catalysed by what enzymes?

Answer 22

-Viral RNA- dependent RNA polymerase

Question 23

What are two forms of positive sense RNA:

Answer 23

-Viral mRNA
-cRNA (complementary RNA)

Question 24

Difference between viral mRNAs and cRNAs?

Answer 24

-mRNA are capped and polyadenylated
-cRNA is not capped or polyadenylated

*Both molecules contain a 5’ triphosphate group

Question 25

Two mechanisms of antigenic variation (how variations arise:

Answer 25

-Antigenic drift: minor changes in antigen structure
-Antigenic shift: major changes in antigen composition (occurs after viruses with segmented genomes co-infect and exchange components)