Viral Evasion of the Host Immune Response Flashcards
What is a key difference between internal virus proteins and surface antigens?
Internal viral proteins vary less
Describe the process of presentation of viral peptides on MHC Class I.
Viral peptides chopped up by proteasome Peptides transported through TAP protein into the endoplasmic reticulum Here, they're loaded onto MHC class I + move to cell surface where T cells can recognise the antigen
State 3 viruses (and the proteins involved) that evade antigen loading onto TAP.
EBV – EBNA1: can’t be chopped up by the proteasome
HSV – ICP47: blocks access of the peptides to the TAP protein
CMV – US6: blocks ATP binding to TAP preventing translocation
State 2 viruses (and the proteins involved) that modulate tapasin function and prevent MHC transport.
Tapasin is involved in loading MHC molecules
Adenovirus E3-19K: prevents recruitment of TAP to tapasin + retains MHC in the ER
CMV – US3: binds to tapasin + prevents loading of peptides onto MHC
State 1 virus (and the protein involved) that interferes with MHC presentation at the cell surface.
KSHV (Kaposi Sarcoma Herpes Virus) – kK3
Induces polyubiquitination + internalisation of MHC
MHC is then passed to lysosomes + degraded
What do NK cells recognise on the cell surface that triggers killing of cells? What is the consequence of this?
Missing self: lack of MHC on the cell membrane is not healthy
Viruses that disrupt MHC presentation get killed
How do viruses evade this mechanism of NK-mediated killing infected cells?
Encode MHC analogues: virally encoded MHC is useless but fools NK cells
Upregulate MHC
What 4 features aid HIV in resisting neutralisation?
Large space between spikes prevents antibody cross linking
Extensive glycosylation masks antibody epitopes
Functionally important sites are difficult to access
Huge variation in the redundant AAs visible to B cell receptor + antibodies
What is antigenic drift? Give an example of a virus that exhibits this process
Continued rapid evolution driven by antigenic pressure from the host
Influenza
What is antigenic shift? Give an example of a virus that exhibits this process
Introduction of new subtypes of the virus from an animal source
Thus antigens don’t look like anything that humans have seen before
Influenza
How else can viruses cause regular infections without changing their antigen profile?
Can have several genetically stable serotypes that co-circulate
E.g. rhinovirus has > 120 antigenically distinct serotypes
How many serotypes of poliovirus are there and what type of vaccine was produced for polio?
3: trivalent vaccine
1 of the serotypes has been eradicated now
What are 4 features of dengue haemorrhagic fever (DHF)?
Leakage of plasma from capillaries leads to: Increased red cell count Decrease in protein Tendency to severe bruising + bleeding Shock
What is the treatment for DHF?
IV fluids
How many serotypes of dengue are there?
4
