Myxoviruses (Influenza) Flashcards
Describe the structure of orthomyxo viruses: Capsid, envelope, baltimore type.
Influenza virus is an enveloped virus with a helical nucleocapsid. It is baltimore type V (-ssRNA).
What are the proteins that can be found in the influenza envelope? What are their functions?
Hemagglutinin (HA) - Binding & fusion.
Neuraminidase (NA) - Binding, and later budding (cleavage).
M2 - Pore, for acidification.
Describe the genome of influenza viruses.
Why does it encode a polymerase?
8 strands of -ssRNA.
Because its genome is negative sense, it needs a polymerase to produce a +ssRNA strand for replication.
What does M1 accomplish in the influenza virus?
M1 sits inside the viral envelope and binds RNA to the membrane. Presumably, this is important for budding and export.
Where does influenza cause infection?
How does it recognie these cells?
Upper, and sometimes lower respiratory tracts.
Hemagglutinin can recognize certain sialic acids on the cells, mostly distinguished by their glycosidic linkages.
How does influenza enter the host cell?
It is endocytosed, then responds to acidification via conformational shifts in FA and M2 to promote fusion and export of the nucleic acids (and their associated proteins).
How does influenza stop host cell translation?
They degrade host cell mRNAs in order to steal their “caps” (5’ guanosine).
What is the final step in influenza infection?
Neuraminidase (NA) must cleave the neuraminic acid in order to be released and infect new cells.
How do amantadine and rimantadine stop flu function?
How do zanamivir and oseltamivir stop flu function?
Plug M2 to stop the viral acidification response.
Bind and inhibit neuraminidase to prevent egress from the host cell.
Distinguish between genetic “drift” and “shift”.
Drift is just random genetic mutation resulting mostly from replication errors. Shift results from the combination of two different strains (this only occurs in influenza A, and only in animals).
How is influenza diagnosed?
Viral cultures and serology. Nasopharyngeal swabs are common.
What is the structure of the seasonal flu vaccine?
How is it manufactured?
Live-attenuated virus (heat-sensitive; may still cause transient upper respiratory infection?)
Selected flu strains are injected into chicken eggs following reassortment/hybridization with egg-loving strains.
