7 - Influenza Small Group Flashcards
What type of virus is influenza? Which types are significant in human disease? What are characteristics of this type of virus?
An orthomixovirus; only influenzas A and B (not C) are significant causes of human disease.
Orthomixoviruses are all enveloped and have segmented negative RNA genomes.
What does the envelope of influenza contain? What is the envelope internally lined by?
Envelope: Glycoproteins hemagglutinin (HA) and Neuraminidase (NA)
Membrane M2 protein
Internally lined by: matrix (M1) proteins
What does the genome of influenza A and B consist of?
Eight different helical nucleocapsid segments, each contain a negative sense RNA associated with a nucleoprotein (NP).
What is the function of hemagglutinin?
Viral attachment protein that binds to sialic acid on epithelial cell surface receptors.
What causes minor antigenic changes?
Mutations of HA and NA genes - called antigenic drift
What causes major antigenic changes (antigenic shift)?
Re-assortment of genomes among different strains, including animal strains.
What are the two classes of antivirals?
- Amantadine and rimantadine
2. Zanamivir and oseltamivir (Tamiflu)
What is the function of Amantadine and rimantadine?How well do they work?
Inhibits viral replication by targeting M2 to prevent uncoating.
Not very good at treating the flu due to resistance.
What is the function of Zanamivir and oseltamivir (Tamiflu)? How well do they work?
Inhibit neurominidase and prevent viral release from cells.
This stops the spread of infection and is only effective within the first 24-48 hours after the onset of influenza A.
What is the primary mechanism for producing flu vaccine strains?
Inoculation of embryonated eggs with the virus.
Virus loaded fluid from egg is harvested and undergoes purification and formalin inactivated.
(Alternatively, sometimes HA and NA are extracted and a vaccine is made from just these protein elements).
