Lecture 10.1: Influenza

Question 1

What is the incubation period? How long is a patient infectious?

Answer 1

1-5 days. After that, infectious for 5-6 days.

Question 2

What is the pathenogenesis of influenza (briefly)?

Answer 2

Binds to sialic acid containing receptors on non ciliated respiratory epithelium (as they have the alpha 2-6 link)

Generally replicates in URT and LRT, particularly larger airways.

Can cause fever (IL-1) and aches (IFN).

Question 3

What is a complication of influenza? Why?

Answer 3

Cilia tends to die during a bout of influenza. Thus pneumonia can be a sequelae.

Question 4

How many gene segments are there in the genome of influenza?

Answer 4

8 Gene segments of single stranded RNA which are -ve sense.

Question 5

What are the three types of influenza?

Answer 5

A, B, C. A and B are flu causing, and A can infect other species.

Question 6

What are the functions of haemagglutinin (trimer) and neuraminidase (tetramer)? Also what is NS-1?

Answer 6

Haemagglutinin helps to grip on to the cell and neuraminidase helps to exit. NS-1 is a non structural protein with anti interferon activity.

Also note that there are 16 different types of H and 9 different types of N.

Question 7

What is needed to cleave HA before the virus becomes infectious?

Answer 7

Tryptase clara, only found in the RT.

Question 8

Why are CD8 T cells broadly cross reactive between Type A subtypes of influenza?

Answer 8

They can recognise peptides derived from the internal antigens of the virus. This cannot be done for type B.

Question 9

What do the antibodies do? And how does cross reactivity help us?

Answer 9

Cross reactivity cannot stop infection, but can lessen severity. The antibody essentially inhibits attachment or release.

Question 10

What is antigenic drift?

Answer 10

Creation of new strains within a subtype. If there is no advantage in mutation, it is simply a drift. Evolution of antigenic drift is said to be linear.

Question 11

Adamantanes are a class of drug that affects which influenza strain? How?

Answer 11

Only affects type A, NOT type B. They inhibit function of M1 ion channel so it prevents the RNPs from escaping the endosome.

Question 12

Tamiflue and Relenza (ivirs) are effective against which strains? How do they work?

Answer 12

They are affective against both A and B. They block action of NA.

Question 13

How is swine flu and avian flu transmitted?

Answer 13

Swine is man to man. Avian is bird to man. Former is not very severe. Latter highly lethal.