S.M Lecture 3

Question 1

Symptoms of Influenza

Answer 1

• Begin 24-48hr after infection, chills
• Fever for a few days (38-39 o C), headache, fatigue due to cytokine release
• Aches and pains, nasal congestion, irritated watery eyes
• Nausea and vomiting
• Possible complications….. Tissue damage, pneumonia, bronchitis, sinus and ear infections.

Question 2

What type of virus is influenza?

Answer 2

• Negative Sense RNA Viruse
• Helical Capsid
• Enveloped
• Belongs to orthomyxoviridae family

Question 3

True or False - Influenza can be divided into 3 types

Answer 3

True. Influenza A, B and C
There is no single genus of influenza, but rather a family of viruses that are divided into different types and subtypes based on their genetic and antigenic properties.

Question 4

Influenza A is divided into subtypes based on which two surface proteins?

Answer 4

• H: hemagglutinin (1 Host range: 15)
• N: neuraminidase 19. e.g. H5N1

Question 5

Describe Infleunza A

Answer 5

• Can infect multiple species
• most virulent and most important human pathogen
• can be further defined based on serotypes

Refer to table in slides

Question 6

Describe Influenza B

Answer 6

• Almost exclusively infect humans; also the seal!
• Does not mutate to same degree as influenza A therefore less genetically diverse
• 1 serotype…..immunity at early age

Refer to table in slides

Question 7

Describe Influenza C

Refer to table in slides

Answer 7

• Can infect multiple species, humans, pigs
• Severe illness and local epidemic

Question 8

Host Range of Influenza A

Answer 8

Host range: Birds (avian), (Major reservoir) All H & N types Swine Humans Horses Ferrets, Mink Seals, Whales

Question 9

How is influenza transmitted?

Answer 9

• Aerosol, close contact

Question 10

What is influenza sensitive to?

Answer 10

• Sensitive to pH, heat and solvents.

Question 11

What are the characteristics of Influenza?

Answer 11

• 100nm…roughly spherical, though filamentous forms do occur (pleomorphic)
• Segment genome
• single-stranded-sense RNA
• Not a single strand of nucleic acid…it consists of 8 pieces of segmented -ve strand RNA (encode 11 proteins)
• > 10 genes
• overlapping reading frames
• helical capsid and envelope
• replicates in nucleus

Question 12

Name the proteins that influenza encodes

Answer 12

• Proteins (HA, NA, NP, M1, M2, NS1, NEP, PA, PB1, PB1-F2, PB2)

Question 13

Neuraminidase (NA) 19

Answer 13

• Glycoprotein found on outside of the viral particle
• Enzyme involved in the release of viral particles from cell
• These proteins are the target for antiviral drugs

Question 14

Haemagglutin (HA) 1-15

Answer 14

• Lectin that mediates binding and entry of the virus to target cells
• This protein is a target for antiviral drugs

Question 15

Influenza genome organisation

Answer 15

• 8 segmented ss Negative RNA genome

Question 16

Influenza Replication Cycle

Answer 16

• refer to slides

Question 17

Why are RNA viruses prone to error?

Answer 17

• The replication machinery of RNA viruses is error prone, giving rise to variation.
• Enveloped viruses are more tolerant to mutation than non enveloped viruses (Plasticity), as the capsid has to perform a variety of functions which can not be compromised

Question 18

What are the two mechanisms to antigenic variation?

Answer 18

• Antigenic drift and shift

Question 19

Antigenic Drift

Answer 19

• Appearance of virus with minor changes in antigen structure

Question 20

Antigenic Shift

Answer 20

Appearance of virus with major changes in antigen composition.
(The geneic change that enables a flu strain to jump from one animal species to another, including humans is called “antigenic shift”)

Question 21

When does antigenic shift occur?

Answer 21

• Occurs after viruses with segmented genomes co-infect and exchange components
• Occurs in areas with high numbers of pigs, birds and people.

Question 22

Name the four different flu viruses which swine flu is made up of

Answer 22

• North American swine influenza
• North American avian influenza
• human influenza, and swine influenza virus typically found in Asia and Europe

Question 23

Sialic Acid Linkages

Answer 23

HA binds to sialic acid (which is attached to galactose via linkage) on surface of host cell membranes.