Week 21: (C) INFLUENZA Flashcards
What are some symptoms of influenza?
headache fever tireless joint aches vomiting coughing runny nose
How is influenza passed on?
aerosols
dropplets
sneezing; say out a large amount of mucous which may contain virus in these particle. if you breath that is you may become infected
What is an example of an influenza virus?
swine flu
What type of particle is the influenza virus which causes human pandemics?
spheroidal particles
What contains the viral genome in the spheroidal particles?
internal nucleocapsid
What does the genome of a spheroidal particle consist of?
The genome consists of
eight single-stranded RNA segments that code for 10 proteins
What are some of the proteins that spheroidal particles genome code for?
PB2, PB1, PA, HA (hemagglutinin), NP
(nucleoprotein), NA (neuraminidase), M1 (matrix protein), M2 (ion-channel protein), and two nonstructural proteins,
NS1 and NS2
How are the type A subtypes classified?
classified according to structural variants for the two surface
proteins: hemagglutinin (15 variants, H1 to H15) and neuraminidase (9 variants, N1 to N9).
What is the target of antiviral drugs on the SPHEROIDAL PARTICLES?
An ion-channel protein
(M2), embedded in the lipid bilayer, is a target for the antiviral drugs amantadine and rimantadine, which inhibit the
protein’s function.
What is the golgi apparatus?
packages proteins into membrane-bound vesicles inside the cell before the vesicles are sent to their destination
What are the 2 ways an influenza virus can mutate?
antigenic drift
antigenic shift
What is antigenic drift?
in which existing antigens are subtly altered, and
antigenic shift, in which two or more strains combine.
What is antigenic shift?
Causes slight flu mutations year on year, from which
humans have partial, but not complete, immunity. By contrast, the new strain of H1N1 appears to have originated via antigenic shift in Mexican pigs
What mutates in a virus?
surface antigens
What are examples of different species harbouring different strains of the flu virus?
bird flu
swine flu
human flu
How did swine flu occur? (antigenic shift)
Swine serve as “mixing vessels” for the genes of avian, porcine and human forms of the influenza virus. In the host
pig, the avian and mammalian viruses can share (reassort) their genes and so create new strains of flu.
genes from bird and human can infect swine and be a novel virus to a human, causing pandemic.
What is a vaccine?
a biological preparation
that improves immunity to a particular disease.
What does a vaccine contain?
A vaccine typically contains a
small amount of an agent that resembles a microorganism.
How does a vaccine work?
The agent stimulates the body’s immune system
to recognize the agent as foreign, destroy it, and “remember” it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters
What are some side effects to taking the influenza vaccine?
> Swelling, redness, or pain at the injection site.
> Fever, headache, fatigue, and muscle aches, occurring shortly after vaccine administration
What is the structure of influenza neuraminidase?
Crystallographic structure of influenza A N9 neuraminidase and its complex with the inhibitor 2-deoxy 2,3- dehydro-N-acetyl neuraminic acid
What receptor does the neuraminidase bind to?
receptor containing sialic acid
What is an antiviral drug that slows down the spread of influenza?
Oseltamivir
sold as Tamiflu
What is the function of Oseltamivir?
slows the spread of influenza virus between cells
in the body by stopping the virus from chemically cutting ties with its host cell. Median
time to symptom alleviation is reduced by 0.5-1 day
What influenzas does tamiflu prevent?
influenzavirus A and B
What is prophylaxis?
treatment given or action taken to prevent disease.
What is Zanamivir?
neuraminidase inhibitor used in the treatment and prophylaxis of Influenzavirus.
What is Zanamivir marketed as?
trade name: Relenza
How does Zanamivir work?
Zanamivir works by binding to the active site of neuraminidase, rendering
the influenza virus unable to escape its host cell and infect others.
How does Zanamivir reduce symptoms?
Zanamivir reduces
the time to symptom resolution by 1.5 days if therapy is started within 48 hours of the onset of symptoms.
What strain is easily spread but rarely fatal?
H1N1
What strain spreads slowly but often fatal?
H5N1
How can an influenza virus cause life-threatening response?
cytokine storm
e.g. in the H5N1 strain (Avian influenza, 1918 pandemic)
What causes common symptoms?
The huge amounts of proinflammatory cytokines and chemokines (such as interferon or tumour necrosis factor) produced from influenza-infected cells
Does influenza cause tissue damage?
YES
Symptoms no entirely due to inflammatory response.
What 2 ways are viruses made?
Golgi apparatus to make glycoprotein in the surface of the cell.
made in cytoplasmic ribosome, these are then used to make the proteins involved in RNA replication.
Virus then assembles with the matrix protein
the virus makes its way to the cell surface and buds out. and infects additional cells
How does the virus get into the cells?
Hemaglutanin
What is the structure of the hemaglutanin?
trimer
globular head
long stalk then small globular region.
What region of the HA is interred into the virus membrane?
small globular region
What is the protease cleavage site?
located on the HA stalk
site of cleavage of a cellular protease.
required for a condo change which allows the haemoglutanin to change its structure.
HA fuse with membrane of cell and causes uncaring.
How does an antibody stop a virus from binding? (neutralise)
bind to sites on the HA to prevent it from binding to host R
What site is on the large globular head on HA?
sialic acid binding site
What undergoes a large confo change when the protease cleavage site is activated?
fusion peptide. change from the stalk to the top of protein causing membrane fusion
