Virus replication, entry and exit
7 important questions on Virus replication, entry and exit
How does a virus enter the host? A cell?
Host Skin protects us from viruses, but has weak points which are the entry points of our body like eyes, mouth, vagina or anus
- Transmitting over placenta: When a virus is already in mum’s body, it can sometimes be transmitted to her unborn child
Cell
- Virus binds to an attachement factor of a receptor from a cell
- Leads to activation of signalling pathways
Mostly they infect dividing cells
What are the entry mechanism for the 2 virus type?
- Enveloped: Direct membrane fuision
- Lipid bilayer taken from the cell membrane during virus particle budding, through which rival spike protein protrude
- Non enveloped: Endocytosis
- Cell-cell contact, an already infected cell can use a virological synapse to infect another cell
The virions are internalized (through membrane fusion or by endocytosis) by the cell who assumes that the virion is something good
Which viral protein binds to the cell membrane protein?
- Enveloped: spike glycoprotein that bind to receptor
- Non-enveloped: projection or indentation in the capside surface bind to receptor
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Explain cell-cell contact if virus is already in a cel
- Giant cells (Syncytia): virus can move freely in those cells
- After uptake by macrophages or dendritic cells some viruses survive degradation in the endosomes and can be presented as whole virions to a CD4+ T-cells
- Dendritic cells infecting CD4+ cells with HIV particles they have captured
While virus replication which steps is done by host?
- Transcription (when needed)
- Translation of the viral RNA into proteins is done by host ribosomes
- Replication of the genome is in most cases done by a virus encoded enzymes
How does the virus exit a cell?
- Enveloped: through budding
- Non enveloped
- Through cell lysis (in culture)
- Use extracellular vesicle, exosomes (in cell)
What is the difference between an enveloped virus and non-enveloped?
Enveloped: sensitive to heat and detergents - it has limited survival outside host
Non-enveloped: more stable outside host
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