Micro 3: viral evasion Flashcards
How does EBV evade antigen recognition?
EBNA1 cannot be processed by the proteasome (has sequences rich in guanine and alanine)
How does CMV evade antigen recognition?
US6 stops ATP binding to TAP preventing translocation.
US3 also binds to tapasin and stops peptides from being loaded onto MHC.
How does HSV evade antigen recognition?
ICP47 blocks processed peptides from entering TAP protein
How does adenovirus evade antigen recognition?
E3-19k stops recruitment of TAP to Tapasin and retains MHC in the ER
How does KSHV evade antigen recognition?
The protein kK3 induces polyubiquitinylation and internalisation of MHC.
From the internalised endoscope, MHC is passed to lysosomes where it is degraded.
How do viruses avoid being killed by NK cells when they don’t express MHC molecules?
Express MHC analogues e.g. CMV produced gpUL40
Describe the mechanism behind vincristine treated cells before transplantation
Cells express MRP-1 which removes toxic molecules from the infected cell.
HCMV produces UL138 protein which leads to loss of MRP-1
If you treat cells with vincristine, it will be retained in the infected cells and therefore you can eliminate these beforehand.
What is the difference between antigenic shift and antigenic drift?
Antigenic drift is the continued rapid evolution driven by antigenic pressure by the host.
Antigenic shift is the introduction of new subtypes from an animal source.
How does the HIV gp120 avoid neutralisation?
Large spaces between spikes so sAb cannot crosslink
Extensive glycosylation masks antibody epitopes
Important conserved region is inaccessible (CD4 binding site)
How does influenza avoid innate and cellular immunity?
The width of the canyon, that interlocks with ICAM-1 receptor is too low for the Fab antibody to interlock with.
What does poliovirus vaccine consist of?
3 serotypes of poliovirus require trivalent vaccine
Salk: inactivated
Sabin: live attenuated
What is the pathology of dengue virus and how do you treat it?
Leakage of blood plasma from capillaries.
Detected by increase in red cell count and decrease in protein level in blood.
Tendency to severe bruising, and bleeding.
Patient deteriorates even after fever drops; shock. Treat with IV fluid replacement.
What is meant by antibody enhancement of Dengue fever?
There are 4 serotypes of Dengue but there is no cross protection.
If antibodies are made against one serotype,
and the virus is present for a different serotype, it can bind but is unable to neutralize the virus.
Taken up into monocytes and induces cytokine storm.
How does Ebola evade antibody recognition?
Has a high content of phosphatidyl serine lipids on surface of cells and is taken up by macropinocytosis as they are recognised as foreign. (Apoptotic mimicry)
It is then not susceptible to antibody surveillance and reduces the time that antibodies can neutralise it.
Viral filaments may be harder to neutralise as the GP are inaccessible in folded pockets.
What is the role of sGP?
It is a soluble GP produced by the Ebola virus and is an antibody decoy.
Antibodies will bind the soluble GP, leave the virus particle undetected.
