(Final) Virus replication Flashcards
T/F: Viruses have the capability to multiply by division
FALSE
How does a virus replicate?
It must hijack the host cell and utilize their organelles to produce its proteins and nucleic acid
What is a permissive cell?
A cell in which a virus is able to replicate
What is a non-permissive cell?
Cells in which a factor or factors necessary for viral replication is not present OR one detrimental to viral reproduction IS present, but the appropriate receptors are missing
What is the MOI or Multiplicity of Infection?
Refers to the number of virions that are added per cell during infection
When does the latent period of viral replication occur?
After uncoating and lasts until just before the 1st appearance of EXTRACELLULAR NEW virus particle
When does the eclipse period of viral replication occur?
After uncoating and until just before the 1st appearance of INTRAcellular new virus particle
What comes first, the latent period or eclipse period in virus replication?
Eclipse period since it goes until new virus is seen within the host cell
Latent = until the appearance of EXTRAcellular new virus particles
What is the Burst Size?
Number of infectious virions released per average cell
What are the steps of virus replication?
- Attachment
- Penetration
- Uncoating
- Synthesis of viral components (nucleic acid and protein)
- Assembly and maturation
- Release in large numbers
T/F: Virus attachment to receptors on the host cell are not specific
FALSE
they are very specific like a lock and key** each virus has its own surface receptor or receptors on specific host cells
How can cells escape attachment from viruses?
If they lack the appropriate receptor for that virus
T/F: In some cases, binding to a cellular receptor is not sufficient for infection; an additional cell surface molecule or co receptor will be needed for entry
TRUE
Co-receptors help certain viruses attach to host cells
Can some viruses use more than one host cell receptor for attachment?
YES
Ex: HIV
What are the two methods naked viruses can penetrate host cells?
- receptor mediated endocytosis (most common)
2. Pore mediated penetration
What two methods do enveloped viruses use to penetrate host cells?
- Surface membrane fusion (pH independent fusion protein)
2. Receptor mediated endocytosis (have pH DEPENDENT fusion protein)
How does FIP virus penetrate host cells?
Antibody-mediated attachment protein and penetration
This is an uncommon method of entry for viruses
What is a more specific method of endocytosis used to penetrate host cells by Non-enveloped viruses?
Clathrin-mediated endocytosis
The process of injecting a viral genome into the host cytoplasm through creation of a pore in the host membrane is known as what? What viruses do this?
Pore mediated penetration
done by naked/non-enveloped viruses
T/F: Surface membrane fusion of enveloped viruses to host cells uses a pH indepented fusion protein
TRUE
How does an enveloped virus with a pH dependent fusion protein enter a host cell?
Receptor mediated endocytosis
uses an endosome to penetrate the cell
What method does FIP virus used to infect host macrophages?
antibody mediated attachment and penetration
The release of viral genome in the host cell is known as what?
Virus uncoating
**The virus can no longer be detected
T/F: After uncoating, a virus is no longer detectable
TRUE
Are virions still infectious after they have undergone uncoating?
NO. they lose infectivity
this is bc they have released their DNA/RNA
What are the two objectives of the “parent” virus taking over the host cell machinery?
- Make multiple copies for new viral genome
2. Make viral proteins for capsid successful replication
What is the function of Reverse transcriptase?
Conversion of viral RNA to cDNA during virus replication
and for double strand DNA viruses that require a single strand RNA intermediate
T/F: A positive strand of DNA will synthesize a positive strand of DNA
FALSE
positive will synthesize negative and vice versa
What modifications must viral mRNA under do to be recognized by host ribosomes?
- capping
- addition of a PolyA tail
- Splicing
These are essential for the processing of viral mRNA
Addition of 7-methylguanosine to the 5 prime end of RNA is what process?
Capping
**5 prime end of the viral mRNA
What end of the viral mRNA does the poly A tail get added to?
3 prime end
*addition of poly-A tail
second step
What is splicing?
RNA splicing is a process that removed introns and joins exons in a primary transcript
T/F: Assembly of virus genome and proteins into new virions follows a specific order
TRUE
Where does the assembly process and maturation of new viruses take place?
Many options depending on the virus
Nucleus, cytoplasm, plasma/cell membrane (most enveloped viruses)
How do naked viruses leave host cells?
LYSIS
T/F: Naked viruses can leave the host cell via budding
FALSE
they are naked so budding would given them an envelope
Enveloped viruses leave the host cell via what process?
Budding through the plasma membrane
What types of viruses leave the host cell via EXOCYTOSIS?
Viruses that acquire their envelope via budding from the ER, goli, or nuclear membrane
What enzyme do reoviruses use to integrate with the host DNA?
What enzyme do they require to synthesize RNA into DNA?
integrase = integration
Reverse transcriptase
What are two ways viruses spread cell-to-cell?
Extracellular spread
Intercellular spread - results in rapid virus dissemination, evasion of the immune system, and persistent infections
Nuclear spread of virus genome- viral genome is integrated into the host cell genome and passed down to progeny cells
What is the fastest method of virus cell to cell transfer?
Intercellular spread
How are viruses spread via progeny cells?
Nuclear spread
