Viruses 5 Flashcards
How are infected host cells detected?
Detection of bacterial/viral proteins displayed by infected cells
How are infected host cells dealt with once detected?
Killing by cytotoxic t cells, apoptosis of the infected cells
ROle of MHCI?
Presents fragments of synthesised peptides on the surface of the cell that is synthesising those peptides
How does VZV evade the immune system?
Blocks the TAP protein that loads antigens onto MHCI
How does HCMV evade the immune system?
SUbverts protein processing antigens in host cells so MHC molecules are degraded
Ubiquitinate the MHCI
How does herpes evade the immune system?
Suppresses apoptosis in early stages of infection. Then integrates into chromosome and remain dormant.
How does HIV evade the immune system?
produces proteins that inhibit autophagosome formation
What is autophagy?
foreign particles to be engulfed by membranes and marked for destruction
How do mumps/measels evade the immune system?
block interferon production
How do viruses evade antigens?
Errors in viral replicaiton can lead to variation in antigen structure
Strategies to combat viral infections?
ID reservoirs and transmission routes
Vaccination
Antiviral drug development
How is Hep A transmitted?
Fecal-oral transmission–> contaminated drinking water and food
Ways to combat hep A transmission?
High sanitation levels
How is influenza categorised?
Surface antigen composition–> Haemagglutinin and Neuraminidase
What do Haemagglutinin and Neuraminidase do?
Facilitate entry and exit into host cells
What is antigenic drift?
slight changes due to random mutation.
What is antigenic shift?
major genetic change results in new antigen (H or N) that is “new” to the host immune system
Why may antigenic shift cause an influenza pandemic?
New forms of influenza are “new” to the host immune system due to their new makeup, so the host wont deal with them as well/quickly
How are new influenza strains formed?
Animals have two or more influenza infections at once, the fragments of protein that they each synthesise in the cells at the same time are packaged at random–> leads to new combinations of influenza from the two that the animal was initially infected with
Why does the WHO surveil the new influenza strains that are circuating?
So it can design new vaccines specifically for those strains
Difficulty of developing antiviral drugs?
Lack of antigenic targets
How does tamiflu (oseltamivir) work?
Is is a neuraminidase inhibitor
What do neuraminidases do?
Facilitate the final release step of the viral particle from the host
What does tamiflu need to have happened for it to work?
Patient to have already gotten the flu
