Virus Entry to Host Cell Flashcards
Describe the steps to a very basic and all encompassing replication strategy.
Enter host cell Replicate genome Make mRNA Make proteins Assemble virions Escape from host
What determines cell tropism?
Receptors which make a cell susceptible to virus entry and replication.
What is the mechanism name of membrane fusion and fission?
Hairpin
How do virions enter the cell?
Either by endocytosis or cell fusion.
Which viruses use pore formation?
Non-enveloped viruses
What are the steps to viral entry
Weak binding
Strong and specific binding to receptor
Enhanced binding
Nucleocapsid enters cytoplasm
How can cells prevent viral entry?
Antibodies: via immune response or IVIG therapy
Dendrimers: nanobiotech or novel therapeutics
Describe early viral genes/proteins.
Enable genome replication
Expressed at low levels
Often effect RNA or DNA synthesis machinery
Often effect cell cycle progression
Describe late viral genes/proteins.
Can be made using newly replicated genomes
Abundant expression
Used to package genomes and assemble virions
What are the outcomes of viral replication?
Acute, chronic, latent, or transformational infections
What are the patterns of viral infection?
Acute, chronic, latent, or slow.
What is a characteristic of the domain archaea that bacteria and eukarya do not have?
They are not, so far as we know, infected by viruses.
Describe RNA dependant RNA polymerases
Reads RNA, makes RNA
Encoded by viruses only
No proof reading
1 mistake: 10^3-10^5 nt
Describe DNA dependent RNA polymerase
Reads DNA, makes RNA
Encoded by viruses and hosts
Some proof reading
1 mistake: 10^4-10^5 nt
Describe RNA dependent DNA polymerase
Reads RNA, makes DNA
Encoded only by retroviruses
No proof-reading
1 mistake: 10^4 nt
Describe DNA dependent DNA polymerase
Reads DNA makes DNA
Encoded by viruses and hosts
Proof reading
1 mistake: 10^7-10^9 nt
Name the mechanisms for virus genome variation.
Mutation, recombination, rearrangement, reassortment
Describe viral mutation.
Point mutations
Accuracy of polymerases
Hot spots
Creates antigenic drift
Describe viral recombination
Can occur during dual infections
HGT
Generation of new virus strains
Has recombination rate (e.g. HIV RR 2.8)
Describe viral rearrangement
Gene reordering and/or duplication
Describe viral reassortment
Occurs in viruses with fragmented genomes
Analagous to sexual repro
Exchange of pieces to create new strain
Creates antigenic shift
What is the cause of viral antigenic drift?
Mutations
What is the cause of viral antigenic shift?
Reassortment
What is a viral quasi-species?
Group of non-identical but interactive sequence which compete in a highly mutagenic environment with selective pressure
Describe with examples how one flu can cause multiple epidemics.
Escape mutants = Spanish, Russian flus with H1N1.
Name some criteria used to classify viruses
Nucleic acid Symmetry of capsid Enveloped or not Genome architecture Baltimore class
