POM 09 - Influenza Flashcards
what are the 4 structural elements of a virus
piece of nucleic acid DNA or RNA
protein caspid
envelope - from human cell membranes
viral proteins (haemagglutinin and neuraminidase)
what do viruses need in order to replicate
require a host cell for replication
what are the 2 types of influenza A that have adapted to humans
H1N1
H3N2
what are cytopathic viruses
viruses that damages cell
how many types of influenza B virus are there
1
when you experience lethargy and loss of appetite from influenza virus what causes these symptoms
mediated by immune system itself - not the virus
caused by cytokine proteins that when they build up in blood stream they react with receptors in the brain and cause illness
what are viral proteins in terms of where they are located and what they do
protein on surface of virus that allows it to bind to its target cell (for influenza its the epithelial cells of the upper airways)
what does haemagglutinin do and how can it be used to prevent influenza dieases
attach to residues called sialic acids
if immune system antibodies bind to haemagglutinin then it cant bind to sialic acid in the nose, as such these neutralising antibodies prevents the infection from taking place
what is antigenic drift in terms of the influenza virus
influenza viruses frequently mutate and their surface proteins/antigens change
what is antigenic shift in terms of the influenza virus
a new type of influenza A virus arises
what is the difference between antigenic shift and antigenic drift
antigenic drift is a mutation in virus that is continuous and under selection pressure of human immune system - it is a slow process due to mutations and only occurs in influenza B
antigenic shift is an abrupt change in genes that make up the influenza A virus
what is an example of how influenza B has undergone antigenic drift regarding HA and antibodies
in terms of what normally happens and what happens after drift occurs
normally the immune system reacts to the virus and forms antibodies to it which can bind to the haemagglutinin molecule and prevent it from binding to the sialic acid in our nose
however the drift can cause the virus to mutate such that the haemagglutinin changes shape/protein structure so that overtime it changes so much that infection cannot be prevented by the antibodies and person is no longer immune
what does neurominidase do
snips the reaction between sialic acid and haemagglutinin to allow viral particle to leave the cell
how do neuraminidase inhibitors treat influenza
if neuraminidase is inhibited then the virus particle cant be released from sialic acid to infect other neighboring cells
when is seltamivir and zanamivir effective in treating influenza
why is this
at the beginning of the infection before lots of cells are already infected - if infection is already in the cells of nose and throat then drugs dont do anything as there are no more cells to prevent virus spreading to
