Viruses and shit Flashcards
Viral structure
Protein capsid that surrounds nucleic acid- Nucelocapsid
Some are enveloped which is an additional covering.
Viral classification
DNA viruses are double stranded except parvoviruses which had ssDNA
RNA viruses are single stranded except dsRNA reoviruses
Most DNA viruses are budded of the nucleus while RNA viruses multiply in and released from cytosol
Modes of penetration
Endocytosis and fusion
Viral replication
Primary- where virus replicates after initial entry determines whether it is localised or will spread
Secondary- replication that take place at susceptible organs after systemic spreading
Cell tropism
Affinity for cell determined by: receptors for virus transcription factors that recognise viral promoters cell ability to support replication physical barriers
Cell damage
If they don’t damage or kill cells virus can proliferate widely (eg HIV just buds off and causes persistant infections)
Picornaviruses causes lysis and cell death leading to fever and increased mucous production
Type 1 interferon (IFN) induction
dsRNA of virus induces expression of interferons by the infected cell
Bound IFN’s activate JAK/STAT pathway which synthesises several genes
IFN’s and NK cells
IFN alpha/beta induces kinase called rna dependant protein kinase (PKR)
IFN alpha/beta binding to NK cells induces lytic activity which kills infected cells. This is enhanced by IL-12
Antibody viral neutralization
If antibody is exposed to viral antigen it can bind to infected cells
3 ways of doing this:
- Blocking penetration
- Causing lysis of virion
- Agglutinating viral particles and acts as an opsonising agent
Cell mediated anti viral response
CD8+Tc cells
CD4+ Th1 cells
Viral response to immune response
Evade IFN alpha/beta actions Inhibit antigen presentation Reduce levels of class 2 MHC on surface membrane Evade complement mediated destruction Immunosupression by invading T cells Change antigens constantly
