Test 2: orthomyxo Flashcards
orthomyxoviridea are —
influenza
enveloped
pleomorphic- spherical or filamentous
medium size (120 nm)
large spikes
segmented
negtaive sense
ssRNA
— line the inner surface of the virion envelope of orthomyxovirus
M1
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
what kind of genome does orthomyxoviridae have?
segmented negative sense ssRNA
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
— on viron envelope of flu virus creat ion channels
M2
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
what are the two spikes found on flu A
HA- hemagglutinin
NA- neuraminidase
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
flu A has how many segments of ssRNA
8
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
because fluA is negative sense it brings it own —
polymerase
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
flu A has — genes that create — proteins
8
10
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
how to name influenza virus
where do RNA viruses replicate?
what virus is the exception to this rule?
cytoplasm
Influenza A
HA protein on flu A will bind to host receptor —- in humans and — in birds
2-6 linked sialic acids
2-3 linked sialic acids
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
RNA replication of flu A occurs in the ___
nucleus
different from other RNA viruses that usually replicate in the cytoplasm
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
Influenza viruses enter cells via —
receptor-mediated endocytosis
HA binds to sialic acids (2-6 in humans, 2-3 birds)
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
how does flu A release genome?
- HA needs to be cleaved by host protease
- low pH inside the endocytic vesicle allows fusion of HA to endosome
- change in ion concentration by ion channel M2 will cause M1 to let go of genome
- will kick out genome that makes its way to the host nuclues
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
— pH mediated change
of structure in endocytic
vesicle of HA on fluA
low
FluA: While in the endosome, the ion
channel — allows the flow of
protons — the virus particle to
enable dissociation of M1 from the
RNP complex.
M2
into
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
—- are antivirals for flu that attack M2
M2 inhibitors
M2 are ion channels that change pH inside→cause M1 to let go to viral genome
amantadine and rimantadine
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
how will fluA initiate mRNA synthesis
Flu A- is a negative sense ssRNA
cap snatching: needs to steal 5’ cap from host mRNA to trigger negative sense into positive sense
done by viral endonuclease (PA)
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
what is cap snatching
negative sense Flu2 will use its viral endonuclease (PA) to cleave the 5’cap from cellular mRNA to change negative sense into positive sense
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
HA on flu A is used for
attachment to host cell
fusion to endosome
NA cleaves — from th cell surface to release infectious viruses
sialic acid
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
—- (antivirals) limit flu virus spread and reduce transmissibility. They mimic sialic acid.
NA inhibitors
— are the reservoir hosts of flu A
aquatic birds
flu viruses replicates where in the body?
intestinal and upper respiratory epithelium
excreted in high amounts in feces and oral secretions
antigenic drift vs shift
drift: small change
shift: reassortment- change in entire gene
Small mutations in key proteins that alter antigenicity and/or virulence hat occur over time due to selective pressure and/or mistakes made by the error-prone viral polymerase
antigenic drift
Major changes by — cause an “epidemic Seasonal Influenza”
drift
drift= small mutations
Segmented genome allows genomic
segments reassortment. This causes major changes in the subtype. Shifts leads to a pandemic.
antigenic shift
why we need new vaccines
why are pigs mixing vessels for flu?
have 2-3 and 2-6 sialic acid receptors
can bind to avian and human flu
can undergo antigenic shift/reassortment and create completely new subtype
— strains of flu can infect pigs, and dual infection may lead to
reassortment and emergence of
new strains.
Avian and human
both avian 2-3 and human 2-6 receptors
swine influenza causes
respiratory disease, high fever and abortions
H3 N2
swine flu is spread by
inhalation, direct, fomites
H3N2- dogs and pigs and huamns
control of swin flu
vacccine and biosecurity
can easier transfer from pigs to humans
2 types of avian flu
low pathogenic avian influenza (LPAI)
highly pathogenic acian influenza (HPAI)
symptoms of low pathogenic avian flu
ruffled feathers
decreased egg production
can be asymptomatic
symptoms of highly pathogenic avian influenza
rapid spread- systemic disease and CNS
Fowl plague- visceral necrosis
mortality rate 90-100% within 48 hours
the more —- HA= more virulent virus
cleavable
if many proteases can cut HA then more viruses will form
Flu (orthomyxo): enveloped, pleomorphic- spherical or filamentous, medium size (120 nm), large spikes, segmented negative sense ssRNA
HPAI contain a polybasic sequence at the cleavage site of HA that allows for intracellular cleavage by —
ubiquitous protease →can effect different organs and systems, leads to systemic infections and death
highly pathogenic avian influenza
LPAI contain a —- cleavage site on the HA.
monobasic
low pathogeic avian influenza
what types of HA are usually pathogenic?
HA 5
HA 7
has enhanced cleavability
HA found on surface of flu virus
difference between LPAI and HPAI
LP- will have only host proteases from the respiratory tract that can cleave the HA protein
HP- will have multiple basic residues at the cleavage site to allow for many different proteases to cleave HA protein
— is equine flu
H3N8
argentinean, florida and kentucky
can spread to dogs
H7N7 no longer exsist
transmission of equine flu —
Highly contagious by aerosol droplets;
inhalation, direct, fomites.
symptoms of equine flu
Harsh, dry cough for ~3 weeks, high morbidity, reddened nasal mucosa, conjunctivitis, serous to mucopurulent discharge, fever, inappetence.
H3N8
equine flu
can spread to dogs
cause respiratory tract disease
canine flu symptoms
Respiratory tract disease (coughing,
sneezing, nasal discharge, fever),
secondary bacterial infections. Often
mistaken for kennel cough.
supportive care
H3N2- birds→dogs
H3N8- equine →dogs
diagnosis of canine flu is by
reverse transcriptase PCR
will determine the H/N subtype and culturered for antigenic analysis
The role of — in the release of the progeny flu viruses and the spread of the virus from the host cell to uninfected surrounding cells
neuraminidase
(NA)
Describe the structure of influenza A (orthomyxovirus) virus
negative sense
segmented(8) ssRNA
enveloped with HA and NA spikes
M2 forms pores
M1 lines inside
What are the different avian influenza subtypes that have
high tendency to mutate to HPAI?
H5 H7
What strains/subtype of equine influenza is currently circulating in the USA?
H3N8
H7N7- extinct
What are the clinical signs of swine, horse and canine influenza viruses?
swine: H3N2- Respiratory disease and abortions, high fever
5-7 day course
horse: H3N8 dry cough for 3 weeks, nasal discharge, conjunctivitis, fever
dog: H3N8 and H3N2- cough, sneezing, nasal discharge and fever. looks like kennel cough
