2.04 - Respiratory Viruses

Question 1

What are haemagglutinin and neuraminidase?

Answer 1

Haemagglutinin is a protein on influenza virus particles that attaches to receptors in the cell surface (cialic acids) in order for the virus particle to enter the cell
Neuraminidase is a protein that cleaves the virus from the sialic acid allowing it to bud from the cell

Question 2

Describe how influenza virus is classified

Answer 2

Divided in to groups A, B & C
Influenza A viruses are then split into serotypes based on the form of Haemagglutinin (H1-H16) and Neuraminidase (N1-N9) present.
Isolates are then named in type, location of lab that first isolated the virus and the year it was isolated. E.g. A/Brisbane/59/2007 (H1N1)

Question 3

Describe the immunity against influenza

Answer 3

Innate immunity is strong (particularly interferons)
T cells are required to clear an infection
Antibodies that recognise HA and NA are most important for preventing re-infection. Anti-HA is a classic neutralising antibody, Anti-NA is protective but not neutralising

Question 4

Describe antigenic drift

Answer 4

Antigenic drift is a mechanism for variation in viruses that involves the accumulation of mutations within the genes that code for antibody-binding sites.
Genetic drift will never result in a change of the HA or NA category, just slight changes resulting in avoidance of the immune system.

Question 5

Describe antigenic shift

Answer 5

Antigenic shift is the process by which two or more different strains of a virus combine to form a new subtype having a mixture of the surface antigens of the two or more original strains.

Question 6

Describe respiratory syncytial virus (RSV)

Answer 6

Very common respiratory pathogen (almost all children had it by 2yo)
Enveloped capsid with helical symmetry
Negative sense RNA genome
Disease largely caused by immunopathology (narrowing of bronchioles due to inflammation)
Transmitted by droplets

Question 7

Describe Rhinovirus

Answer 7

Most common cause of the common cold
Positive sense RNA virus
Non enveloped (virus released by lysis)

Question 8

Describe Adenovirus

Answer 8

Linear, double stranded DNA genome
Non-enveloped genome
Replicates in the nucleus
Cause of URTI