39-40 (-) and dsDNA Flashcards
what is the only virus in the orthomyxovirus family called?
influenza (Note there are influenza A,B,C)
Orthomyxoviruses are enveloped? helical? segmented?
enveloped and helical with 8 segments
What 3 factors determine the strain of flu?
1) NP protein
2) M1 protein
3) M2 protein
what does the VAP (hemaglutinin) of orthomyxoviruses interact with on host cells?
Sialic acid on host to promote attachment
(note that HA has to first be cleaved by a protease in order to bind to sialic acid. This protease is abundantly found in the lung of humans.)
what does H5N1 influenza mean?
H=hemagluttinin type 5
N=Neuraminidase type 1
what do the orthomyxoviruses have to take into the cell with them besides their - sense RNA?
RDRP
what kind of linkage (bond) connects HA to SA?
alpha 2,6 linkage using galactose (this is important because it allows for tropism of the virus to respiratory)
How do orthomyxoviruses (influenza) get into the host cell?
Binding HA and SA, then they are phagocytosed. From they they fuse with and endosome. The low Ph and M2 protein pump allows fusion of membranes. RNA enters cytoplasm.
where does orthomyovirus replicate?
in the nucleus. Recall this is the exception because it is a (-) strand RNA virus.
Orthomyxoviruses do not have caps needed for translation. How do they fix this problem?
They steal the 5’ caps from the cellular mRNA. This promotes their growth and inhibits the host.
What does the orthomyxovirus use for replicating its genome?
RDRP (it goes from - stand that serves as a template for + stand that once again serves as a template for - stand)
How do the viruses bud away from the host cell?
They use NA (this cleaves the Sialic acid facilitating its release. This is where Tamaflu works)
why can you get the flu every year?
New strains due to HA (H) and NA (N) variation. ( so you are never getting the same strain twice. You get a slight variation)
what is antigenic drift in influenza?
minor changes in HA or NA from point mutations
what is antigenic shift in influenza?
major changes in HA or NA from complete replacement of one or the other. (This only occurs in influenza A)
what causes the yearly cycle of influenza? what causes a pandemic?
yearly cycle=antigenic drift
pandemic=antigenic shift
what do you elicit an immune reaction against in influenza?
HA and NA
why does influenza change every year through antigenic shift?
Its because it uses an error prone RDRP that allows for the point mutations in both influenza A and B
why are orthomyxovirus able to under go genetic shift so easily?
because they have 8 segments which makes for easy recombination.
T/F orthomyxoviruses have known avian and swine connections for recombination?
True (Ex: swine flu)
why did the flu of 1918 kill so many people?
Because there was an extreme antigenic shift in influenza (new HA or NA) that the human population had never seen before. Also, the RDRP was more pathogenic
A spanish flu of 1918 kill a lot of people. What class of flu was it A, B, or C?
A, you know this because it was able to undergo genetic shift which can only be done by type A
what barrier prevents free flow of influenza A from waterfowl to pigs to humans?
Sugar linkages.
Birds use 2,3 linkages and humans use 2,6 linkages.
when and how is the flu spread?
when= mainly in winter
how=large aerosol droplets
How is influenza detected in the lab?
viral culture Reverse transcriptase Immunoflourescence Serology Enzyme assay (just note that quick in office tests don't distinguish between A and B while higher quality lab tests test for A or B)
What is the function of the M2 ion channel?
Promotes viral uncoating from the endosome allowing RNA release into the cytoplasm
what does tamiflu do?
Neuraminidase inhibitor: prevents cleavage of sialic acid from cell membrane by NA slowing viral budding.
T/F there are trivalent and tetravalant flu vaccines?
TRUE
Which type of flu vaccine is injected? inhaled?
injected=inactivated (0-2, >49 years of age)
inhaled=attenuated (2-49 years old)
which diseases are caused by paramyxovirus?
measlesmumps
RSVParainfluenza
which paramyxoviruses go systemic? which stay in respiratory tract?
systemic=measles and mumps
respiratory=RSV and parainfluenza
T/F In the MMR shot all of the viruses are killed?
False, they are all alive.
do you build up immunity to RSV or Parainfluenza of the same serotype?
No, the body does not elicit a good reaction for protection against these two paramyxoviruses.
Paramyxoviruses are enveloped/naked? segmented? helical?
They are enveloped helical non segmented.
T/F the replication cycle of paramyxoviruses are the same as orthomyxoviruses?
False, ortho replicates in the nucleus and para does not. Also ortho steals the 5’cap
How is paramyxovirus transferred from one person to the next?
Large droplets of saliva or resp. secretions
T/F paramyxovirus steals the 5’ caps just like the myxovirus does?
false it does not
Where does paramyxovirus replicate?
in the cytoplasm because it is RNA.
recall the orthomyxovirus is the exception
what are key indicators for a mumps infection?
swelling of cheeks and under jawParotitis
T/F mumps can cause sterility in men?
True if it replicates in the testis.
what are the key indicators that a person has measles? 4x
koplik spots (tongue spots)
high fever
Rash can progress to encephalitis and pneumonia
T/F measles is a huge risk for toddlers in Africa killing thousands each year?
TRUE
What causes the rash in measles?
T cell response to the virus
If you see Koplik spots on a child, what is the disease?
measles
they look like grains of sand on a wet background
what are the 3 main steps to a measles infection?
1) enters body via respiratory route
2) spreads throughout body causing viremia
3) transmits to basal side of trachea epithelia and is released on the apical side.
measles causes encephalitis in 3 ways which are?
1) infection of neurons
2) immune mediated post infection
3) subacute sclerosing pan encephalitis
How do you prevent measles? treatment?
1) prevent with MMR vaccine
2) no treatment
what is the leading cause of croup in kids?
parainfluenza virus
T/F you can get the same strain of para influenza over and over?
true. short lived immunity to same strains
Which virus causes lower resp. tract infection (bronchiolitis), kills epithelial cells in the lungs causing plugs of dead cells?
RSV or the paramyxovirus family
what % of children in daycare are exposed to RSV annually?
98%
RSV is dangerous for whom?
1) lung disease
2) premature
3) very young/old
T/F you will not get the same strain of RSV?
False, as with the parainfluenzas, you have a very short lived immunity.
what is the leading cause of bronchiolitis?
RSV
Is there a vaccine for RSV? Treatment?
No vaccineTreatment uses Ribavarin (Nucleotide analog) and monoclonal antibodies against F protein (very expensive)
what does metapneumovirus do?
Bronchiolitis and common colds
when do you usually see metapneumovirus and RSV?
fall/winter
What virus is being defined? Enveloped, helical, bullet shaped, neg. strand RNA?
rabies virus
at what point does rabies become lethal?
once it infects a nerve of the PNS and begins to move retrograde towards spinal cord/brain
What are Negri bodies?
inclusion bodies found in rabies infected nerves
Is there a treatment for rabies?
No treatment for rabies. However post exposure prophylaxis is possible through human rabies immunoglobulin and killed virus vaccine.
what are the two viruses that are part of the filovirus family?
Ebola and marburg viruses
How would you describe filoviruses?
enveloped
helical
neg. strand RNA
How would you decribe bunya viruses?
enveloped helical neg. strand RNA 3 segments circular RNA
what are the 2 types of viruses under bunya virus familiy?
Hantavirus
Lacross virus
what are the two subtypes of Hantavirus of the bunya virus family?
1) sin nombre virus (mice in 4 corners area)
2) sin nombre like virus (mice in Yosemite)
what causes Hantavirus, what does it do to the body?
Deer mice feces, causes your lungs to fill with fluid and you die.
where do you find Lacross virus, what are carriers?
Found in wooded areas because small mammals such as squirrels are carriers. Transferred through mosquitoes
what are the two leading causes of viral encephalitis?
1) WNV encephalitis
2) Lacross encephalitis
what are the two members of Reoviruses?
RotavirusReovirus
which virus is the number one cause of gastroenteritis in kids?
Rotavirus
How do you describe Reoviruses as far as DNA/RNA, DS/SS, etc?
Naked
DS RNA
11 segments
Linear
How is reovirus spread?
oral fecal
what is the only DS RNA we cover?
Reoviruses
what is the largest problem associated with reovirus infection?
dehydration from the gastroenteritis
How do you treat Reoviruses?
supportive care only
