Introduction to Viruses 2 Flashcards
vast majority of DNA viruses have
double stranded genome
vast majority of RNA viruse have
single stranded genome
parovirus is what kind of genome
single stranded DNA
what is the only family that has single stranded DNA
parovirus
where do DNA viruses replicate
where the majority of our DNA is: nucleus
what is exception to DNA replication
Pox viruses - replicate in cytoplasm
where do RNA viruses replicate
cytoplasm
what is exception to RNA viruses replicate
orthomyxoviruses - replicates in nucleus
what DNA families replicate in both nucleus and cytoplasm
retrovirus
hepadnavirus
baltimore classification is classified based on
replication strategy
ds DNA virus, how will it replicate?
nucleus
exceptoin to route for DNA virus, how will it replicate?
poxvirus will replicate in the cytoplasm
replication strategy for majority of double stranded DNA viruses
in nucleus
in the nucleus the viral DNA genome is transcribed by
host RNA polymerase
for large DNA viruses they will have what right away
immediate early and early gene products
viral DNA polymerase - ds DNA
some viruses encode their own, host cells would only have it in S phase, they wouldn’t have sufficient to replicate their genome
depending on cell virus affects it can utilize
host DNA polymerase
for herpes virus they encode their own
viral DNA polymerase
what needs to be packaged
enzymes that are required to get to mRNA stage
regarding DNA polymerase, the virus just has to
encode it
viral DNA polymerase will do what
replicate viral genome
late proteins are
structural proteins of virus
do DNA virus have to package DNA enzyme
no b/c the host cell can provide enzyme needed to get to mRNA
what is exception to DNA replication
pox virus - they replicate in cytoplasm, so even though host cell has the enzyme needed to get to mRNA, it won’t be found in the cytoplasm, so they have to package RNA polymerase
pox virus has to package
RNA polymerase
RNA polymerase in pox virus is packaged
in virion itself
anything packaged also has to be
encoded
once there is mRNA what is made
early proteins
for pox viruses to replicate genome it has to encode
DNA polymerase
does pox virus package DNA polymerase
no - it is translated from first wave
list out steps of normal double stranded DNA proliferation
pg 33
list out steps of exception double stranded DNA replication
pg 34
once mRNA is made it can be translated
into any protein the Virus needs
single stranded DNA family are
paroviruses
exception to double stranded DNA
poxvirus
list steps for single stranded DNA viral replication
pg 36
once single stranded DNA is in host cell genome what happens
the host RNA polymerase will transcribe it
once mRNA of single stranded DNA is made it will
go to cytoplasm and make protein
paroviruses viruses infect what kind of cell
replicating cells
erythrocytes
for ss DNA what will replicate the genome
host DNA polymerase will replicate genome
double stranded RNA virus family
riovirus (rotavirus is part of that family)
majority of rna virus replicate in
cytoplasm
ds RNA genome has to be transcribed into
mRNA
list steps of ds RNA replication
37
ds RNA has to package
RNA dependent RNA polymerase
the viral rna transcriptase used for ds RNA is
RNA dependent RNA polymerase
mRNA in ds RNA replication is translated into
proteins
mRNA is used to also make
viral RNA replicase
what is viral RNA replicase
RNA dependent RNA polymerase
new copies of genome are
encapsulated and released from the cell
positive sense RNA can be
directly translated into proteins
+ssRNA genome steps
pg 38
in +ssRNA does RNA dependent RNA polymerase need to be packaged
no
why doesn’t +ssRNA need to package RNA dependent RNA polymerase
it’s not needed to get to mRNA stage
-ssRNA virus what are examples
influenza, measles, rabies
influenza virus replicates in the
nucleus (this is exception!)
in influenz does the site of replication have anything to do with how it replicates
no b/c we don’t have the rna dependent rna polymerase so it doesn’t matter where it’s replicated
list steps for -ssRNA replication
pg 39
in -ssRNA genome rna dependent rna polymerase
is packaged in virion
in replication cycle of -ssRNA there is intermediate called
replication form - ds RNA
complementary starnd to genome in -ssRNA is
mRNA
+sense RNA virus it can be
direclyt translated into proteins
-sense RNA virus
genome cannot be direclyt translated, need to make complementary strand
enzyme needed for -sense RNA
has to be packaged as part of the virus
HIV is what kind of virus
retrovirus
why is HIV not considered part of +sense?
although genome is +sense, it’s not available for translation
list steps for +ssRNA with DNA intermediate
pg 41
reverse transcriptase
has three catalytic activities
what is first activity of reverse transcriptase
rna dependent DNA polymerase
makes rna to make complimentary dna strand
second function of reverse transcriptase
dna dependent dna polymerase
uses dna strand to make template to the strand
third function of reverse transcriptase
ribonuclease - degrades the rna strand
what happens at end of +ss RNA with DNA intermediate
stays in host cell nucleus, will not be transcribed unless cell is activated
what enzyme does HIV bring with it to process proteins into mature form
protease
viral proteins made in +ss RNA with DNA intermediate (HIV)
precurser proteins - have to be made into mature form
why is protease packaged (in viruses like HIV)
it is still working when virus is budding from cell
unless cell is activated, HIV will
be provirus in nculeus, will not be made or transcribed or infect new cells
HBV stands for
hepatitis B virus
partial dsDNA genome example
HBV
steps of partial dsDNA genome with RNA intermediate
pg 44
viral dna polymerase in HBV
reverse transcriptase
HBV uses what to make mRNA
host RNA polymerase
HBV has what kind of genome
Partially double-stranded DNA with RNA intermediate
why does HBV virus bring the enzyme with it
it doesn’t need it, it could use host cell enzyme
reverse transcriptase is packaged and encoded is b/c its required for packaging genome (needs reverse transcriptase to package!)
look at chart on pg 48-49
look at virion for each and understand
depending on where virus assembles it determines where what are
inclusion bodies are
inclusion bodies are deposits of protein falling out of solution b/c there’s so much protein being made
virus that assemble in nucleus, what kind of inclusion bodies?
intranuclear inclusion bodies (herpes)
virus that assemble in cytoplasm there will be what kind of inclusion bodies
intracytoplasmid inclusion bodies
if there are inclusion bodies or not depends on what?
depends on level of protein production
naked viruses will do what for release
burst open cell
envelop virus will require what for release
envelope from membrane bound body in cell - almost always plasma membrane
when viruses are budding they will indictate where they will bud by doing what
inserting peplomers at that site
naked virus released by
lysis
envelop virus released by
budding
herpes virus aquires envelope in what process
2 step process
2 step process of herpes virus envelop aquirement
assembles in nucleus, when it buds out of nuclear membrane it aquires envelope from inner nuclear membrane. that envleop efuses with outer nuclear membrane and that first envelop eis lost. the final envelope is aquired by budding into the golgi and then continues to plasma membrane and outside of cell
secondary envelop of herpes virus aquired by
golgi
ex of segmented RNA genome
influenza virus (8 different segments)
what can happen w / segmented genomes
if a cell is infected with (ex: two strains of influenza A virus), it can mix and match its genomes
reassortment!
what is re-assortment used to do
used to generate influenza vaccines
virus 1 and virus 2 (types of influenza) the different influenza RNA gene segments can be (what is result)
reassorted b/w themselves, so there can be virus that have features of both 1 and 2
what would re-assortment be used for regarding vaccines
generate a live vaccine that is weakened (live attenuated vaccine)
if there virulent strain of flu, how would you make a vaccine to protect ppl against it
grow the vaccine up with a weakened strain of the flu in fertilized chick eggs and it will reassort its genome
at end select for virus that has weakened nature of the one strain but has antigens of the virulent strain
external proteins dictate what
tropoism of virus
another mixing that can happen b/w viruses besides reassortment?
mixing of surface proteins
describe what is mixed when viruses mix their surface proteins
peplomers of envelope virus
or capsid proteins of naked virus
a cell that is affected with two different viruses may have altered
tropoism
what is ultimate result of a virus that mixes surface proteins
that virus that leaves could have different tropism and infect another type of cell. however, it will only affect the different cell once b/c its genome hasn’t changed, so when it reproduces it will go back to what it could affect before
in mixing of surface proteins of two viruses, what is mixed regarding phenotype and genotype
changing of phenotype, genome doesn’t change
laboratory diagnosis of viral disesase
detection of virus
direct detection of viral antigens
serological analysis
molecular analysis of genetic material
dhow is detection of virus usually done
culture of virus
if virus has hemagglutin can detect certain properties
HAI
can be done for viruses that have hemagglutinin
determine amount of virus what assay used
viral plaque assay
viral plaque assay
grow cells that are susceptible to infection by virus of interest
prepare different dilutions of virus (b/c when starting off don’t know how much you have)
incubate
virus infects cell
get cell lysis
sufficient cells lysed that you can see it
count plaques to know how much virus is there
basis of viral plaque assay
virus lysing the cell it infects
dilution factor is inverse of
dilution
everywhere a virus infects a cell the virus
will lead to cell death
area of cell death is called
plaque (viral plaque)
count number of plaques what will it tell you
tell you how much virus is there
to determine how much virus is there after you get the plaques, what do you do?
multiply number of plaques by dilution number
in plaque assay you always have to change the mL it was plated in to be
1 mL
for viral plaque assay you need to know number of plaques in
1 mL
five hours following infection with polio virus, what happens
all the proteins being made inside the cell are poliovirus proteins
the poliovirus hijacks the cell
live vaccine that is weakened is called
live attenuated vaccine
