Viral Immune Evasion Flashcards
What is the ultimate gal of the immune response to a viral infection?
eliminate both the virus and the host cells harbouring or replicating the virus.
Describe how antibody neutralises extracellular virus?
- It blocks viral attachment proteins (e.g., glycoproteins, capsid proteins)
- It destabilises viral structure
What are the five functions of antibody in the anti-viral response?
- neutralise extracellular virus
- Opsonise virus for pathogocytosis
- promotes killing of target cell by the complement cascade and antibody-dependent cellular cytotoxicity.
- resolves lytic viral infections.
- blocks viremic spread to target tissue
Which Ig class is an indicator of recent infection?
IgM
Which Ig class is a more effective anti-viral than IgM?
IgG
Which Ig class is important for pretecting mucosal surfaces?
IgA
What does HIV exist as?
Quasi-species / multiple clades
How does HIV escape antibody recognition?
Exists as multiple quasi-species
How does HBV and Ebola virus evade antibody recognition?
encode secreted surface antigens that mop up antibody, stopping it reaching virus particles or infected cells.
How many serotypes does Dengue Virus exist as?
4 Serotypes
What triggers Dengue Haemorrhagic fever?
Previous infection with one serotype followed by infection with a different serotype can lead to antibody dependent enhancement of disease as virus enters immune cells via antibody and the Fc-Receptor.
Which virus shows antigenic drift?
Influenze virus
What is antigenic drift?
When viruses like flu mutate and evolve each year
Describe how influenza undergoes antigenic shift?
Influenza viruses can also acquire completely new antigens by reassortment with animal viruses
Why is finding a cold vaccine difficult?
Rhinovirus - the most common cold causing pathogen, has too many serotypes
What is the name of the small proteins released by virally infected cells that play a role in immune protection against viruses?
Interferons
How is interferon production induced?
The presence of molecules made by viruses that are sensed by the cell as foreign or in the wrong cellular location
What might trigger the production of interferon from a virally infected cell?
double-stranded RNA
RNA that lacks a 5’ cap
DNA in the cytoplasm.