COVID + Influenza

Question 1

What type of virus is the influenza Virus?

Answer 1

Enveloped RNA virus with 8 RNA segments

Question 2

What characteristics would a flu virus need in order to become a pandemic virus?

Answer 2

Most viruses usually don’t transmit well to humans - in order of avian influneza viruses to transmit to humans it needs;

3. Novel antigenicity
4. Replicate effeiciency in human airway
5. efficient transmission between people

Question 3

What are the different types of Influenza Viruses generally causing human influenza infections?

What are their natural reservoir?

Answer 3

Influenza A: natural reservoir Ducks/ Birds
Influenza B ?

Differnece between them: different proteins (e.g. M2 protein on influenza A, BM2 channel on Influenza B)

Question 4

What is antigenic drift?

Answer 4

Accumulation of point mutations (due to error prone RNA polymerase) that changes the nature of the antigen over time (drift)

Question 5

What is an Antigenic Shift?

Answer 5

Recombination of genomic segments of two co-infecting flu strains –> leads to rapid potentially whole antigenic change for a viral strain

Question 6

. Explain the replication cycle of the influenza virus in human cells

What role do HA (Haemagglutinin) and NA (Neuraminidase) play in this?

Answer 6

1. Influenza viruses bind to the respiratory tract epithelium
2. **Viral hemagglutinin (H) **binds sialic acid residues (neuraminic acid derivatives) on the host cell membrane → virus fusion with the membrane → entry into the cell
3. The virus replicates in the nucleus of the cell
4. The new virus particles travel to the cell membrane → formation of a membrane bud around the virus particles (budding)
5. Viral neuraminidase (N) cleaves the neuraminic acid → virions exit the cell
6. Host cell dies → cellular breakdown triggers a strong immune response

Question 7

Why is influenza predominanty a respiratory disease?

Answer 7

Because Virus is activated by Human airway tryptase found in lung tissue

Mechanism
Trypttase is cleaving the viral hemagglutinin surface

Question 8

What usually causes severe outcome of influenza?

Answer 8

Secondary bacterial pneumonia
Mutatint virus
CO morbidity
Cytokine storm

Question 9

What different classes of antiviral therapy can be administered for the treatment of influneza?

Answer 9

1. Amantadine (inhibit cell entry via the M2 channel - no lnoger recommended as only present in influenza A + resistance occurs)
2. Polymerase inhibitor - Baloxavir (new drugs)
3. Neuraminidase inhibitor

Question 10

What is the antiviral of choice in treating Influenza?

What is the MOA?

Answer 10

Oral Oseltamivir (Tamiflu)
+ other drugs from Neuroaminidase inhibitors

Inhibit exiting of formed virons –> stop viral replication

However limited effectiveness so only given if
1. Symptom onset <48h
2. Severe disease/ high risk

Question 11

What type of vaccine is the influenza vaccine?

Answer 11

Different types of vaccines available
1. inactivated - given to adults at risk
2. live attenuated - given to children
3. combination

Question 12

What are the characteristics of coronavirus?

Answer 12

Coronavirus

large, encapsulated RNA virus witth +ve sense RNA genome

Question 13

What role do ACE recpeptos play in an infection with coronavirus?

Answer 13

ACE receptors are a entry point of viruses to cells (however conversely probably limit viral infection)

Question 14

Explain the time course of a normal COVID-19 infection

Answer 14

Question 15

Summarise COVID treatment in the UK

Answer 15

1. Dexamethasone given if oxygen requirement
2. Monoclonal antibodies (Regeneron, Sotrovimab), can be given
3. Small molecule antivirals (e.g. Remdesivir)