Afzal Aleem - Freshers Flu Flashcards
Describe the 1st step of the mechanism of influenza action
Haemaglutinin receptors on influenza attach onto sialic acid on the csm of respiratory endothelial cells
Describe the 2nd step of the mechanism of influenza action
Influenza enters the cell via endocytosis and releases its RNA into the cytoplasm of the host cell
Describe the 3rd step of the mechanism of influenza action
The viral RNA is then imported into the nucleus using viral localisation signals
Describe the 4th step of the mechanism of influenza action
The viral RNA is transcribed into mRNA using the host cell machinery and viral RNA polymerase
Describe the 5th step of the mechanism of influenza action
The viral RNA is exported to the cytoplasm and uses the ribosomal machinery of the host cell to synthesise viral proteins
Describe the 6th step of the mechanism of influenza action
Viral RNA and various viral proteins, such as HA, neuraminidase and M2 proteins, assemble and the virus buds from the cell membrane and leaves the cell.
What are the influenza A glycoproteins
Haemagglutinin, neuraminidase and Matrix-2
What kind of illness does influenza C cause
Mild upper respiratory tract illness (like common cold)
What is haemaglutinin and what does it do?
- Membrane glycoprotein
- Binds to sialic acid, allowing virus to enter cell
What is the effect of HA binding to sialic acid on erythrocytes?
Haemagluttination - creates a lattice of interconnected RBCs and virus particles
What is neuraminidase and what does it do?
- Membrane glycoprotein and glycoside hydrolase enzyme
- Cleaves sialic acid side groups from glycoproteins so that viruses can be released from cells
What is antigenic drift?
- Natural mutation of a viral strain resulting in small genetic changes
- Accumulation of genetic changes can produce viruses with slightly different antigenic material and cause people to become susceptible again
- Occurs in all influenza subtypes
What is the result of antigenic drift?
- Sometimes no effect
- With accumulation - causes a loss of immunity or vaccine mismatch
What is antigenic shift?
- Abrupt change in genetic material that results in formation of a new influenza A virus subtype or virus with HA or HA/NA combo that has emerged from an animal population that most people don’t have immunity against.
- Only occurs in influenza A
Describe the mechanism of antigenic shift
When two or more different strains of a virus infect the same cell, their genetic material can combine to produce progeny with new HA/NA combinations.
