ID week 5
four mechanisms for penetration and uncoating
1. fuse directly with PM 2. clatherin dependent endocytosis 3. caveloin dependent pathway 4. clatherin and caveolin independent pathway
what are 6 characteristics to classify viruses?
1. structure 2. biochemical properties 3. disease caused 4. means of transmission 5. host cell 6. tissue or organ
immunopathology often occurs as a result of ______ cell killing virus infected host cells
CD8 T cells
the below are what kind of viruses? Smallpox HSV Adenovirus Hep B Epstein-Barr virus (EBV) Varicella-zoster
DNA viruses
enveloped viruses with bisegmented RNA genome that encodes 4 proteins
LCM
EBV component that inhibits T cell activation
LMP-1
EBV protein localized to exosomes
LMP-1 latent membrane protein
postive strand RNA virus
Togavirus
Asparagine (n-linked) can serve as viral _________ proteins
attachment
four major steps of the infection cycle
attachment and entry translation genome replication assembly/release
__________ tend to have steady growth while _______ tend to have sharp "bursts" of growth
bacteria viruses
reverse transcriptase
converts RNA to DNA
viral mRNA regardless of origin undergoes ______________ modifications knows as __________
covalent RNA processing
mechanism by which viruses kill host by damaging infected cells
direct killing
a tRNA is selected according to the sequence of mRNA codon. peptide bond form between polypeptide chain and incoming AA
elongation
a lipid membrane obtained by budding through host membrane structures
envelope
can derive from nucleus , ER, or plasma membrane
envelope
functions to.... protect internal structures attach to target cells aid in viral entry
envelope
flaviviridae family are ________ and single stranded ______ RNA
enveloped + sense
viral membranes that can host derived are called ______
envelopes
extracellular vesicles that facilitate communication between cells
exosomes
what 3 things are used to generally distinguish between viruses?
family, genera, and species
Adenovirus transmission
fecal, aerosol , fomites
negative strand DNA virus
filovirus
examples of helical viruses
filovirus orthomyxoviruses
zika virus is in_________ family
flaviviridae family like yellow fever, dengue, etc.
viruses with negative strand RNA genomes are typically what shape?
helical
viral capsids can have which 3 symmetries
helical isosahedral complex
enveloped viruses can have what two symmetries?
helical or icosahedral NOT complex
which is smaller: hep c virus or vaccinia virus?
hep c virus
envelopes are derived from host or virus?
host
the process of translation occurs where?
host ribosomes
when does conformational change or cleavage of glycoproteins occur?
late in assembly or after release
in ____________ stage of infection viral gene products are made in low amounts or not at all
latent
these viruses have what pattern of infection? herpes virus
latent
HSV viron is released how?
lysis exocytosis cell to cell bridges
all viruses must produce _______ to be translated by host ribosomes
mRNA
kolplik spot mouth ulcers are seen in what virus?
measles
most eukaryotic mRNAs are _________
monocistronic
only encode a single protein
monocistronic
Adenovirus portal of entry
mouth gets in GI
____________ viruses are resistant to harsh environmental conditions like temperature
naked capsid viruses
does helical structure limit capsid/virus size?
no
generally _____ bonds are formed so that mature viron can enter new target cell
non-covalent
release of most ____________ viruses results in cell lysis/death
non-enveloped
Adenovirus is ______________ and ________ stranded DNA genome
non-enveloped and double stranded
what are the fates of infected cells?
nothing cell lysis (death) permanent change viral latency immune mediated cell death
HSV ________ associates with viral proteins in the cytoplasm the buds into the golgi
nucleocapsid
discrete structural unit consisting of nucleic acid enclosed in capsid (the who package)
nucleocapsid
refers to the development of cancer
oncogenesis
segmented, negative strand RNA virus
orthomixovirus
5 protomers combine to form
pentamer capsomere
NKs release .....
perforins and granzymes
________ cells allow for the completion of the viral life cycle and production of infectious agents
permissive
these viruses have what pattern of infection? measles HIV
persistant: symptoms
these viruses have what pattern of infection? JC virus Lymphocytic choriomeningitis
persistent: asymptomatic
most RNA viruses bud from the _________. why?
plasma membrane so virus is released without killing cells
Examples of RNA modification
poly A tail at 3' end m'GpppN' Cap at 5' end
bacterial mRNA tend to be ________, encoding more than 1 protein
polycistronic
in icosahedral viruses proteins associate to form _______
protomers
what does binding to alpha dystroglycan result in?
receptor mediated ednocytosis
transforming infections alter growth properties in what ways?
reduce requirements for serum growth (lower the bar) loss of contact inhibition
many viruses spread via _________ route in order to remain wet
respiratory or in bodily fluids
permanent change to cells (what virus)
retroviruses
viruses are thought to contribute to 20% of human cancer. which viruses are mostly to blame?
retroviruses and DNA viruses
capsids with helical symmetry appear as _____ shaped
rod shaped
why is the flu able to re-assort so easily?
segmentation
viral genomes must be _________ packaged during assembly
selectively
viral protein "addresses"
signal sequences membrane retentions signals nuclear export signals
zika portal of entry......
skin
IFN Natural Killer CD8
specific to T cells
GP1 and GP2 associate to form ______ proteins
spike proteins
_________ cells express appropriate viral receptors on their surface
submissive
host cells must be ________ and ________ to a virus for entry to occur
susceptible submissive
replication in target tissue causes what?
symptoms
______ link specific AAs with codons in the mRNA
tRNA
stop codon enters the ribosome and cleaves the protein chain
termination
how are more complex icosahedrals formed, such as those in herpes simplex virus?
the addition of more subunits
viruses relay on _______ for metabolism and for ATP required processes
the host
enveloped viruses must remain _____
wet
does icosahedral structure limit capsid/virus size?
yes
the below are what kind of viruses? Measles Flu Rabies Ebola HIV Dengue Zika Hep C Hep A
RNA viruses
what viral properties were considered by the classical system?
RNA vs DNA, size, protein shell symmetry, presence vs absence of envelope
mRNA strands and DNA strands equivalent to the mRNA are considered to be what sense? why?
+ easily translatable
RNA and DNA strands that complement + strands have what sense?
-
modes of control for viruses
1. Quarantine 2. vector elimination 3. vaccination 4. antiviral treatments 5. lifestyle changes 6. hygiene and sanitation
what are the 3 conditions in the Baltimore system?
1. Whether it is RNA or DNA 2. if genome is ss or ds 3. whether rNA ss is positive or negative sense
in what two ways do viruses cause cancer?
1. activating cellular transduction pathways 2. disruption of cell cycle control pathways
6 unique properties of viruses you should know for quiz!
1. viruses are filterable agents 2. viruses are obligate intracellular parasites 3. viruses cannot make energy or proteins independent to host cell 4. viral genomes can be DNA or RNA, but NOT both 5. viruses have a naked capsid (envelope morphology) 6. viral components are assembled, but do not "replicate" by division
chain of infection stage where entry into a susceptible host occurs
Acquisition
virus with double strand DNA
Adenovirus
LCMV is a member of _______ virus family
Arenaviridae
most viral glycoproteins have ______ carbohydrates
Asparagine (n-linked)
focuses on genome type, and that all viruses must produce mRNA that host can translate
Baltimore system
the viral genome encodes protein synthesis machinary like ribosomes and tRNA, and proteins for metabolism true or false?
FALSE they do not
non-enveloped viruses tend to survive harsher environments, and are therefore often found in the _________
GI
in LCM, a protein called ______ is translated by ER-bound ribosomes
GP-C
GPC is cleaved into _________ and ________
GP1 and GP2
the flu infects many hosts, relying on _______ protein on cell surfaces in order to infect
HA
mutation of the CCR5 gene is a co-factor in __________ entry
HIV
the _________ nucleocapsid assembles in the nucleus an buds into, adn then out of, the ER
HSV
measles reduce levels of _______ cytokine, meaning not as much viral clearance occurs
IL-12
why must enveloped viruses remain wet? what are they disrupted by?
acids detergents drying heat
these viruses have what pattern of infection? Rhinovrius Flu Rotavirus
acute
adenovirus is part of what family?
adenoviridae
LCM virion binds to what receptor?
alpha dystroglycan
disadvatage of this mechanism is that high volume of molecules needs to synthesized to increase chance encounters between them
assembly from individual protein
assembly or proteins shells/capsids have 3 techniques
assembly from individual protein assembly from polypeptide chaperon assisted assembly
perk of this mechanism is that individual proteins dont need to find eachother at an assembly sie
assembly from polypeptide
polioviruses uses what kind of assembly for capsids/ protein shells?
assembly from polypeptide
best way to control Adenovirus is through......
better hygiene and sanitation
protein coat of a virus
capsid
this protein structure protects viral genomes and in some cases mediates attachment
capsid
genomes are packed into ______
capsids
many viruses spread ________ without passing into extracellular space. others can also spread extracellularly
cell to cell
______ assist in protein folding and can be host or virus derived. this one happens often.
chaperon assisted assembly
______ are most susceptible Adenovirus
children
___________ was based on the idea that viruses should be classified by shared traits rather than those of what cells they infect
classical system
viruses like HIV, flu, and polio require _______ or ___________ to be fully infectious / mature
conformational change cleavage of glycoproteins
parvoviruses and picornaviruses contain capsids of what structure?
icosahedral
stage in chain of infection where virus is amplified and moves from primary to secondary site (usually through blood or lymph)
incubation period
most common portal entry for viruses?
inhalation
formation of complex of mRNA, ribosome, and initiator tRNA
initiation
where does translation begin and end?
initiation codons and termination codons
chain of infection stage that occurs at a primary site where proper receptors/ machinary are needed to establish infection
initiation of infection
three stages of protein translation
initiation, elongation, termination
skin, tears, mucous, and immune cells like macrophages and dendritic cells are a part of what immune response
innate immunity
interferon production and apoptosis are ________ responses
instrinsic
catalyzes insertion of viral double strand DNA into host DNA
integrase
both ______ and __________ enzymes are encoded intro viral genomes of retroviruses
integrase and reverse transcriptase
most non-enveloped viruses (and some enveloped) do what to cell upon exiting?
kill
_______ genomes tend to encode proteins for viral replication, nucleic acid metabolism, and evasion of host immune system
larger
Paroviridae viruses contain ss DNA genomes. what is their pathway to mRNA?
the ss DNA is synthesized into double strand the double strand is then translated to mRNA
rabies has limited __________ tropism
tissue tropism
example of capsid with helical symmetry
tobacco mosaic virus
cancer related viruses cause _______________ infections, leading to cell proliferation
transforming
in general, enveloped viruses attach via ______ and non-enveloped viruses attach via _________
transmembrane glycoproteins capsid surface or projections
HSV blocks peptide uptake into the ER true or false
true
adenovirus E3 blocks MHCI transport to golgi true or false
true
sometimes, immunopathology causes death of host true or false
true
the viral genome contains all the info needed for a virus to replicate/ spread true or false
true
viruses with larger genomes are less dependent on the host true or false
true
mRNA contains 5 and 3 ______ and an _______
untranslated regions (UTR) open reading frame (ORF)
best way to control zika?
vector control/ reservoir elimination
process by which viruses causes disease
viral pathogenesis
______ contains a nucleic acid genome packed into a protein capsid
virion (virus particle)