34 - Virology Flashcards
what is a virus?
obligate intracellular parasite
what is the smallest known self-replicating orgaisms?
virus (20-300 nm)
what are potential viral hosts?
bacteria
protozoa
fungi
algae
plants
animals
who were the 3 men credited for the discovery of viruses
Adolf Mayer
Dmitri Ivanovsky
Martinus Beijerinck
what is the purpose of the capsid?
protein shell surrounding the nucleic acid genome
positive sense (+) RNA is what?
translatable RNA (same as mRNA)
negative sense (-) RNA is what?
RNA that must be copied (not translatable) into (+) RNA prior to protein expression)
what is an ambisense RNA?
there are genes on both (+) and (-) sense RNA’s
energetic significance of the ocosahedral
most energetically favorable way to make a sphere out of flat planes
the _________ ____________ of a virus is vital in transmission and its mechanism of infection
outer surface
do enveloped or non-enveloped viruses tend to be more stable
non-enveloped
where does the virus derive its membrane from?
the host
T/F most viruses aren’t limited to a particular host, tissue, or cell type
False
what is host cell range determined by?
Host cell receptor availability for entry/binding
presence of intracellular host cell factors
what is the capacity of a cell, tissue, or species to support virus replication
susceptibility
major steps of general virus replication
binding/adhesion
fusion and entry into cell
uncoating
replication and gene expression
assembly
release
(maturation)
majority of epithelial sites that viral infections initiate at?
respiratory epithelia
conjunctiva
gastrointestinal tract
vaginal mucosa
T/F a virus can interact with any plasma membranes, carbohydrates, proteins, or lipids within membrane
true
targets of viral binding
cellular protein(s)
lipids (specific/non-specific)
carbohydrates (specific/non-specific)
receptors may limit host-cell __________ and _________
range, susceptibility
how does the virus enter using fusion with plasma membrane (enveloped)?
receptor binding causes conformation change in envelope protein resulting in fusion with cell membrane
describe viral entry using endocytosis
internalization into endosome
pH changes causes conformation change in envelope protein and fusion with endosomal membrane and release into cytosol
describe viral entry through plasma membrane
pore formation (injection) (enteroviruses)
membrane perforation (adenoviruses; reviruses)
when uncoating, viruses may release factors to initiate _________ and/or __________
replication, shut off of host cell defenses
what will replication complexes do during RNA viral replication
protect against innate immunity
sequestration of viral components
most viruses will have their own specific ___________ during RNA viral replication
RNA polymerase
what organelle(s) are viral replication complexes assoc. with?
ER or Golgi
what is a huge signal for the innate immune system with RNA viruses?
dsRNA
T/F RNA is labile
True
what will provide specificity in RNA viruses?
RNA structure
what will determine the recruitment of cellular factors, promote translation, and package signals in RNA viruses?
RNA structure
what are mechanisms RNA viruses use to increase genetic capacity?
segmented RNA genome
subgenomic RNA’s
polyprotein synthesis
nested subgenomic RNA’s
where does replication typically occur with DNA viruses?
in the nucleus
will DNA viruses use host machinery for replication?
may or may not
depends whether virus carries a DNA polymerase
Which phase is DNA synthesis most efficient for DNA viruses?
S phase
Which DNA viruses are limited to infecting mitotically active cells
parvoviruses
which DNA viruses drive cellular proliferation
adenoviruses
T/F some DNA viruses inhibit cellular DNA synthesis
True
during assembly part of replication where is the genome incorporated as the core is assembled in RNA viruses? DNA Viruses?
RNA: cytoplasm
DNA: nucleus
for enveloped viruses, where does assembly typically occur?
the site of membrane acquisition (e.g. nucleus, ER/golgi, plasma membrane)
steps in the replication - budding/release process?
1) lytic
2) exocytosis via cellular pathways
3) budding out plasma membrane
(maturation)
which pathway usurps the ESCRT vesicular budding pathway
HIV
what is a disease that is naturally transmitted between humans and other vertebrates?
zoonoes
T/F humans are typically dead-end hosts
True
what is primary infection
infection with invasion at portal of entry
after replicating locally what is the term for when some of the viruses enter circulation and infect other tissues?
secondary viremia
what is a target cell?
the cells that are targeted by the virus and result in clinical disease
T/F it’s likely the majority of virus infections cause no disease
True
enveloped viruses must remain _________!
wet
what environmental factors will affect transmission
temp
humidity
vector life-cycles (feeding/reproductive periods)
T/F the adaptive immune response can contribute to the clinical diesase
true, the adaptive immune response may limit or contribute to clinical disease
viremia may produce ___________
biphasic disease
what are the 2 types of persistent infections?
latent infections
chronic infections
which viruses can result in concolytic transformation of cells
epstein-barr virus
hepatitis B(DNA) and C (RNA)
papillomavirus
human T-cell lympohotropic virus (HTLV)
what are immune modulating drugs?
interferons
steroids
monoclonal antibodies
T/F vaccines will typically block infection
False, they typically do not completely block infection, but prevent disease
mechanisms that vaccines use to prevent disease?
rapid clearance
aborting viremia
blocking transmission to target organs
types of vaccines?
prophylactic/preventative (active)
post-exposure (active and/or passive)
therapeutic (active)
live-attenuated virus will produce both _________ and ___________ immunity to multiple targets
humoral, cellular
T/F inactivated vaccines usually only produce cellular immunity
False! INACTIVATED usually only produce HUMORAL
viral vectors will use _________ virus to express antigenic proteins of __________ viruse
attenuated, pathogenic