| what are the host tropisms of the different influenza types? | influenza A: humans, birds, pigs, horses, bats, seals etc.
influenza B: humans (pigs and seals)
influenza C: humans and pigs
influenza D: pigs and cattle |
| what are the main proteins on the influenza envelope and what are their functions? | hemagglutinin (HA): mediates the binding of the virion to the target cell and the entry of the genome into that cell
neuraminidase (NA): involved in the detachment of the virion from attachement sites in the human e.g. the mucus |
| what is the membrane protein (M2) and what does it do? | it is a protein in the lipid bilayer of the influenza virus. once inside the cell, it forms a proton channel that promotes the acidification of the envelope/inside of the virion, which causes uncoating |
| how does the influenza virus exit a cell and why? | it exits the cell by budding. this is because it's an enveloped virus, which gets its envelope from the host's cell membrane |
| what is the pathogenesis of influenza? | it kills mucus-secreting, ciliated and other epithelial cells in the respiratory tract, causing local respiratory tract infection and secondary bacterial pneumonia
neuraminidase increases this effect by cleaving off sialic acid residues, providing access to the underlying tissue, causing primary viral pneumonia |
| what is the difference between antigenic drift and antigenic shift? | antigenic drift: genetic variation in viruses caused by mutations, minor antigenic changes, in all influenza, causes seasonal flu, only young and elderly get sick
antigenic shift: two or more viruses combine to form a new virus, major antigenic change, only in influenza A, causes pandemics, everyone gets sick |
| why are pigs good 'mixing vessels' for new influenza strains/avian influenza? | pigs have both 2.3 and 2.6 sialic acids on their receptors in the respiratory tract. humans only have 2.6 sialic acid on their receptors in the upper respiratory tract.
avian influenza prefers to bind to 2.3 sialic acids, which it can do in pigs. there it can mutate and also bind to 2.6 sialic acids. now it can also bind to 2.6 sialic acids in humans |
| why is avian influenza more dangerous to humans? | avian influenza binds to 2.3 sialic acids deep down the respiratory tract of humans, the deeper down the more dangerous to clean up
there are no vaccines or immunity to the avian flu |
