Virus Replication Flashcards
Viral Replication:
Steps
- Receptor mediated
- Attachment and Entry
- Uncoating
- Genome replications
- RNA and protein synthesis
- Assembly of nucleocapsid and maturation
- Release form the cell
Susceptible
has a receptor for a virus
Resistant
does not have the receptor for a virus
Permissive
Can replicate the virus
Susceptible and permissive
The virus can enter the cell and replicate
Viral Replication:
- Steps for Attachment and Entry
- Virions have to diffuse across the plasma membrane and then release the genome
- Steps for attachment and entry:
- Adhere to the cell surface
- not specific, happens by chance since they cannot move
- Attache to a recepto
- these receptors are not made for the virus they are receptors for proteins that the cell normally needs
- Genome is then transferred into the cell
- Adhere to the cell surface
Viral Replication:
- Entry:
Once the virus enters it is transported to the correct location
CME = Clathrin-mediated endocytosis
Viral Replication:
- Uncoating
Acidic condition in the endosome triggers changes in viral structural proteins resulting in uncoating and release of the viral genome
Viral Replication:
make mRNA
Transcription
Viral Replication:
- Transcription of Viral Genes
DNA genome Viruses
Host or virus DNA-dependent RNA polymerase generates viral mRNA
mRNA is translated into viral proteins using cellular machinery
Viral Replication:
- Transcription of viral genes
RNA genome Viruses
Require a viral-encoded RNA-dependent RNA polymerase (RdRp) to make mRNA
There is no cellular RdRp to copy RNA form a viral RNA template.
Virus must possess or synthesize RdRp
Viral Replication:
- Translation of mRNA to make viral proteins
- Translate the mRNA into protiens
- Compare to cell mRNA
- 5’ cap UTR AUG ORF stop UTR AAAAAA 3’
- Ribosomes are needed for translation
- tRNA also needed to add the correct amino acids
- Translation also needs
- initiation
- Elongation
- Termination proteins
Viral Replication:
- Virus Replication:
Viral Genome synthesis:
DNA viruses
most replicate in the nucleus
except poxvirus and mimivirus
Most us the host DNA-dependent DNA polymerase
Except poxvirus and herpesvirus
Viral Replication:
- virus replication
Viral genome synthesis
RNA viruses
most use viral encoded RNA-dependent RNA polymerase
except retroviruses that use reverse transcriptase
Quasispecies - not two viral genomes are identical
Viral Replication:
- Translation of Viral Proteins
- All viruses use cell machinery for making proteins
- Viral protiens:
- often named based on timing of synthesis
-
Early Translation Products:
- mostly nonstructural protiens
-
Late Translation Products:
- Structural proteins
Viral Replication:
- Assembly of nucleocapsids and Virus maturation
-
Self assembly of the capsid:
- many viral proteins assemble on their own
- HIV poliovirus, Influenza HA
- Empty shells can be the basis for vaccines
- many viral proteins assemble on their own
-
Assisted Assembly:
- some need scaffold and chaperones from the cell to form the viral structure
- All viruses have to:
- form the protein chell from one or many viral proteins
- Assemble the protein shell
- Release the virion from the host cell
- Some viruses have to:
- Acquire an envelope
- Go through virion maturation
Viral Replication:
- Budding or Release from the cell
Envelope
Normally happens after the assembly of the nucleocapsid then buds
There are four strategies for budding
Viral Replicaiton:
- Budding or Release from the cell
Budding:
Depending on the virus, budding can occur form any membrane compartment
Can make a double membrane on the virus
Viral Replication:
- Budding or Release from the cell
How can viruses exit the cell
- Important for pathogenesis:
- budding:
- aquires a membrane
- Lysis:
- break the cell open and release the virion
- Release viruse without lysis (poliovirus)
- Move from cell to cell without cell lysis
- budding:
Viral Replication:
dsDNA virus:
Steps 1-3
Herpesvirus Replication - replicates in the nucleus
- Protein vhs:
- cuts up the host cell mRNA which blocks host cell defenses
- Protein VP16:
- facilitates the transcription of herpesvirus RNA
Viral Replication:
dsDNA virus:
Steps 4-5
Herpesvirus replication - replicates in the nucleus
- Three types of mRNA produced by the virus
- a - immediate earyly
- B - early
- y - late
Viral Replication:
+RNA virus (Coronavirus)
Replicates in the cytoplasm
Buds in the ER/Golgi
Only makes 8 viral proteins
Viral Replication:
Retrovirus
Retroviruses have a provirus step
They replicate in the Nucleus for the DNA step
If a retrovirus infects a germ cell there cen be a generational infections (vertical transmission)
When the cell divides the virus divides with it because of hte provirus
