Respiratory Pathogens: Example 1 - influenza A

Question 1

what are 3 features of Influenza A virus itself

Answer 1

• enveloped
• spherical
• 90-100nm diameter

Question 2

what are the different types of influenza named based on?

Answer 2

named based on their spike proteins

Question 3

what are the 2 spike proteins found on influenza A

Answer 3

haemagglutinin (HA) + neuraminidase (NA)

Question 4

what does positive and negative sense mean in genetics

Answer 4

the sense means the direction in which the transcription is read

Question 5

how many segments exist in the genome on influenza A and how many proteins do these segments enode for?

Answer 5

• genome has 8 segments
• these 8 segments can code for 10-14 proteins

Question 6

what is the baltimore system

Answer 6

the way to classify viruses

Question 7

what does monocistronic mean

Answer 7

when genome segments encode for a single protein each and are translated into peptides directly from that genome.

Question 8

what features make genome sections in influenza A monocistronic?

Answer 8

they are monocistronic because the genome segments:

• are single stranded
• because of their genetic sense

Question 9

what does PB2, PB1 and PA enzyme proteins allow for influenza A to do?

Answer 9

allows influenza A to transcribe without using the host cell’s machinery

Question 10

outline the ** lifecycle of influenza A

Answer 10

1. influenza A virus present near host cell
2. Influenza A adheres to the host cell via spike proteins attachment to alveolar sialic receptors
3. This leads to a conformational change and the virus is taken into an endosome via endocytosis
4. Influenza A will then uncoat its own envelope and release its genetic information
5. the viral RNA released can be copied into a complementary strand using the virus’ own polymerase enzyme, or the viral RNA can go directly to a ribosome and undergo protein synthesis and produce its own proteins
6. these proteins will eventually make up a new virion (encapsulated virus particle) through assembly of different parts
7. the virion matures and then can go on to infect another host cell, which is called dissemination, or it can infect another individual, which is called transmission.

Question 11

what is the natural reservoir for Influenza A

Answer 11

birds

Question 12

what type of virus is influenza A in terms of Spread?

Answer 12

zoonotic virus

Question 13

how is influenza A transmitted mainly

Answer 13

inhalation

Question 14

what are the 2 major components to symptoms caused by infection of Influenza A virus

Answer 14

• respiratory tract symptoms
• systemic symptoms

Question 15

what are 3 examples of respiratory tract symptoms caused by Influenza A infection

Answer 15

• rhinitis (sneezing, itchy nose, runny nose, congestion)
• cough
• shortness of breath

Question 16

what are 3 examples of systemic symptoms caused by influenza A infection

Answer 16

• fever
• headahcer
• myalgia

Question 17

what cytokine released by alveolar macrophages causes increased body temperature?

Answer 17

IL-1

Question 18

what cytokine released by alveolar macrophages cause headaches and general myalgia?

Answer 18

IL-6

Question 19

what cytokine released by alveolar macrophages causes the liver to release acute phase proteins?

Answer 19

IL-6

Question 20

what is a pneumotropic virus (influenza A)

Answer 20

a virus that infects cells lining the respiratory tract, down to the alveoli

Question 21

what is a cytolytic infection (influenza A)

Answer 21

when the infection strips the surface respiratory epithelium

Question 22

what 2 innate defence mechanisms does influenza A remove by stripping surface respiratory epithelium

Answer 22

• mucous secreting cells
• cilia

Question 23

what are interferons in defence to?

Answer 23

antiviral defence

Question 24

what 3 ways are interferons antivirals?

Answer 24

infected cells give off interferons to signal to the neighbouring cells to:
- switch them off and make them dormant and not undergo protein synthesis
- schedule programmed cell death (apoptosis)
- cause neighbouring cells to produce more interleukins

Question 25

what is the main complication of influenza A infection and what are the 2 types

Answer 25

main complication: Pneumonia

two types:

• primary influenza pneumonia
• secondary bacterial pneumonia

Question 26

what type of infiltration occurs in primary influenza pneumonia vs secondary bacterial pneumonia?

Answer 26

primary influenza pneumonia:
- alveolar lymphocyte/mononuclear cell infiltration

secondary bacterial pneumonia:
- alveolar macrophage/polymorphonuclear cell inflitration

Question 27

what is a cytokine storm

Answer 27

a cytokine storm is when there is an excess of uncontrolled inflammatory cytokine signals being produced

Question 28

what 3 things can cytokine storm lead to

Answer 28

lead to:

• excessive inflammation elsewhere in the body
• healthy tissue being damaged and scarred all over the body
• sepsis

Question 29

what is antigenic drift

Answer 29

series of spontaneous point mutations occuring over long periods of time

Question 30

what are the 2 mechanisms that give rise to antigen variation?

Answer 30

• antigenic drift
• antigenic shift

Question 31

what do the small variations associated with antigenic drift cause

Answer 31

causes the seasonal flu epidemics

Question 32

what is antigenic shift

Answer 32

sudden dramatic change resuling in a new subtype of pathogen

Question 33

what is one situation where antigenic shift can occur?

Answer 33

co-infection of host cell with two different viruses which causes reassortment of viral RNA strands resulting in a new subtype consisting of a mixture of RNA strands from each virus

Question 34

what 2 ways we prevent influenza A

Answer 34

• infection monitoring
• vaccination

Question 35

what are the 3 types of vaccination

Answer 35

• inactivated
• recombinant
• live attenuated

Question 36

what are 4 ways to treat influenza A

Answer 36

• oxygen therapy
• anti-viral drugs
• antibiotics
• Intensive Treatment unit (ITU/intensive care) support