virology replication Flashcards
what are the basic steps in replication
- entry
- replication of genome
- generation of mRNA to make new viral proteins
- Assemble new virions
- Exit
- spread to new organism
what happens in the early phase of replication
adsorption to cell penetration of cell membrane uncoating- capside degeneration ------------- [migration of genome to nucleus (some viruses)]
what happens in late stage replication cycle
replication of viral nucleic acid transcription translation assembly release spread to new host
entry
by adsorption and penetration
adsorption
binding to cell and the host range of the virus is often controlled here
the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface
where does replication occur
in the cytoplasm or the nucleus - location is depending on the virus
assembly can occur where?
in nucleus or cytoplasm or the combination of the two
release of virions
budding or lysis
absorption
incorporation of a substance in one state into another
what is the envelope of the cell and where is it from
it is a lipid bilayer
it is derived from the cell
what is on the envelope
enveloped glycoprotein this is an envelope protein
appears as spikes
the spike of the on the enveloped virus are what?
what are they called
transmembrane glycosylated proteins
envelope glycoproteins (Env)
what is the env ectodomain
it mediated the attachment and fusion
it binds to a receptor on the cell surface
tropism is determined by?
the receptor on cells to which the env binds
the envelope glycoproteins are what
trimers
what determines serology
antigenic sites
what neutralize viruses
antibodies
t/f env can be highly variable
true- it mutates frequently to order to evade adaptive immune responses - mainly antibodies
targets for antiviral drugs are developed
by my taking advantage or…
the virus binding and entering
viruses that use cell surface receptors to enter the cell
receptors on the cells to which viruses bind are used by the cell for other purposes and exploited by viruses
- influenza A
- HIV-1
- hepatitis C
- rabies
- rhinovirus
- hepatitis B
- Adenovirus type2
- poliovirus
how does fusion happen when an enveloped virus enters the cells
fusion can occur
- at the cell surface (like in HIV)[fusion and uncaring]
- or with the membrane of the endosome after it enters the cell. the endosome will release the genome into the cell (influenza virus)[endocytosis , fusion and uncoating]
naked virus binding
viral spikes bind to the cell
the trimeric spike proteins mediate binding to their receptor
naked virus entry
e.g polivirus
adenovirus(has triads) lysis leads to uncoating
viruses must
- replicated their genomes
- make mRNA
how do genomes replicated
using either cellular polymerase or a viral polymerase or both
replicase
a viral nucleic acid polymerase
why is mRNA made by viruses
to generate proteins and new virions
what about a virus makes it a good target for drug development?
a virus that uses its own enzyme
what happens if a virus uses a cellular enzyme
then probably not a good target for drugs, since enzyme is needed by the cell to do its normal functions
inhibiting a cellular enzyme can be toxic
DNA viruses
most replicate in the nucleus
the use the cells machinery
must replicate in proliferating cells that are replicating cellular DNA so that the cell
s DNA replication machinery is active
some induce cell proliferation and can cause cancer.
how does an enveloped virus exit from the cells
budding
what happens when proteins accumulate to the point of reaching critical concentration
self assemble into viral subunits or higher order structures
where does assembly of subunits or virions occur within the cell
nucleus
ER/Golgi
cytoplasm
plasma membrane
what are viral proteins first generated as?
poly protein
it is then cleaved into mature proteins by either a viral or a cellular protease
what steps are attractive targets for antiviral drug development
assembly and maturation
maturation of HIV virion
have a precursor Gag polyprotein
it is immatures when the virion has an uncelaved Gag
mature and infectious after Gag is cleaved
how are naked viruses released?
cell lysis
