Vet Viral Immune Evasion Flashcards
What is immune evasion?
Deliberate modulation of a host immune system to benefit the infectious agent
- all viruses employ this
- prevent detection, fake signals, stop effector mechanisms
Impact of viral immune evasion is dependent on:
- target of immune evasion
- relative success of immune evasion
- mechanism of immune evasion
What are the two main targets against viruses?
- extra cellular phase (target the viruses between host cells)
- intracellular viruses (target infected host cells)
What do NK cells do?
distinguish infected from uninfected host cells by MH class 1 interaction
Why are inferons important in the viral immune response?
- early anti-viral response
- inferon releases IFNB
- produced by virally infected cells within hours
- lead to the production of anti-viral components
What does MHC class 1 do?
- presents intracellular antigens
- helps detect and kill infected cells
What does MHC class 2 do?
- presents mostly extracellular antigens
- helps respond to extracellular and intracellular infections
What do Th1 cells do during a viral infection?
- enhances macrophage activity, antigen processing, more nutralising antibody production
- Produce IFN-y (DIFFERENTATION OF tH CELLS)- target of vet viruses
How does Pox-virus impact IFN-y?
- produces soluble IFN-y receptors
- leads to blocking of the signal before its received
- Other chemokine and cytokine decoy receptors used
What do neutralising antibodies do?
-can block viruses and bacteria from binding to receptor by which they enter the host cell
- making them a target
How are neutralising antibodies evaded?
changes in the ammino acid sequence of the epitope causes no immunity/limited cross-reactivity
mechanisms of neutralising antibody evasion:
Antigenic drift: single nucleotide / small scale changes that impact recognition of surface antigens
Antigenic Shift: major changes of genes are swapped between viruses
How does pestivirus (bvdb) evade the immune system?
- immune tolerance
- cytopathic and non cytopathic
- causes inter-uterine infection (infecting primary lymphoid tissues)
- Removes any T and B cells responding to self
What does cytopathic mean?
causing death/changes to cells in culture
How do herpesvirus cause viral evasion?
- latency