Viral immune evasion Flashcards
What are the MAIN roles of antibodies against viruses (2)
- Neutralising extracellular virus blocking viral attavhment proteins and destabilising viral structure
- Opsonisation of virus for phagocytosis
- Promotes killing of target cell via complement cascade
- Resolves lytic viral infection
- Blocks viremic spread to target tissue
How do interferons help against viruses? [2]
- Virally infected cells produce and release them
- **IFN binds to a cell surface receptor on other cells and induces production of antiviral enzymes **
- IFN activates NK cells and systemic antiviral response
Name the 2 Type 1 IFNs. Which cells specially secrete IFN-alpha?
IFN-alpha & IFN-beta
Plasmacytoid dendritic cells (PDCs)
Is IFN- beta secreted by all cells?
Yes
Is the IFN-alpha receptor present on all tissues
Yes
What is a Type 2 IFN and which cells is it produced by? [2]
IFN-gamma
Activated T cells and NK cells
What is a Type 3 IFN and how does it signal?
IFN-lambda
Through IFN-lambda receptors on epithelial surfaces
How do viruses combat IFN
- Hep B and influenza block production of IFN by inhibition of IFN transcription
- Influenza produces a protein that counters RNA sensing and prevents poly A
How do virus combat T cells?
- HIV kills CD4 T cells and alters macrophage function
- Herpes simplex virus can prevent CD8 T cell killing
What are NK cells activated by and what do they do?
Activated by IFN-alpha and IL-12
Releases toxic substances when it finds cells displaying fewer than normal MHC in order to kill virus infected cell
What do macrophages do?
Filter viral particles from blood
Inactivate opsonized virus particles
Present antigen to CD4 Tcells
How do dendritic cells protect against viruses?
- Immature and plasmacytoid DCs produce IFNalpha and other cytokines
- Initiate and determine the nature of CD4 and CD8 T cell response
- Present antigen to Tcells
