Influenza Flashcards
Populations that are high risk with Influenza?
- 65yo and older
- Existing chronic medical conditions
- Lowered immunity (pregnancy, young children)
Structure of Influenza:
- RNA virus
- Lipid envelope
- Protein capsid
- Neuraminidase and Hemagglutinin surface proteins
What is the most virulent form of Influenza?
Influenza A
What is the function of Hemagglutinin (HA)?
Surface glycoprotein that binds to cellular receptor and initiates membrane fusion (infiltration)
What is the function of Neuraminidase?
Surface enzyme that allows the virus to leave the infected cell and spread throughout the body (exit)
What are the different Influenza strain names based upon (e.g. H#N#)?
Variations of surface protein distribution (HA and NA)
Why is the flu rarely fatal?
It usually takes 1000s of Influenza replications before the virus kills the cell.
What are the primary targets of the Influenza virus?
Epithelial cells of the Upper and Lower respiratory tracts
Lower resp. infection often more fatal
How does Influenza enter the cell?
HA binds to Sialic Acid residues on surface of target cell
- > Receptor-mediated endocytosis of Influenza RNA using host-cell membrane
- > Vesicles fuse with endosomes
How does the Influenza viral RNA work within the cell? How does it multiply?
Low pH in endosomal lumen activates Influenza RNA
- > RNA replicates w/cell’s RNA polymerase
- > Influenza proteins translated w/cell’s ribosomes
- > New Influenza virions assembled using host cell’s membrane
How is the Influenza virus released from the host cell?
NA cleaves HA and Sialic Acid connections to release newly formed virions
What constitutes an Influenza vaccine?
Inactivated Influenza viruses w/variants of NA and HA
Why doesn’t the flu vaccine always work?
Antigenic Drift and Antigenic Shift
What is antigenic drift?
Point mutations (slight variations) in flu surface proteins that occurs from many replications DURING THE FLU SEASON of ONE STRAIN of Influenza
What is antigenic shift?
When TWO STRAINS of Influenza (often Avian) combine to form a NEW STRAIN of Influenza with different variants of HA and NA that infects unimpeded by antibodies
